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NONRESIDENT TRAINING COURSE June 2015 Aviation Electronics Technician (Organizational) (ATO) NAVEDTRA 14030A Notice: NETPDTC is no longer responsible for the content accuracy of the Nonresident Training Courses (NRTCs). For content issues, contact the servicing Center of Excellence: Center for Naval Aviation Technical Training (CNATT), (850) 452-8175 or DSN 459-8175 for the AT Rate Training Manager. DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. PREFACE By obtaining this rate training manual, you have demonstrated a desire to improve yourself and the Navy. Remember, however, this manual is only one part of the total Navy training program. Practical experience, schools, selected reading, and your desire to succeed are also necessary to successfully round out a fully meaningful training program. THE MANUAL: This manual is organized into subject matter areas, each containing learning objectives to help you determine what you should learn, along with text and illustrations to help you understand the information. The subject matter reflects day-to-day requirements and experiences of personnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers (ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational or naval standards that are listed in the Manual of Navy Enlisted Manpower and Personnel Classifications and Occupational Standards, NAVPERS 18068(series). THE QUESTIONS: The questions that appear in this manual are designed to help you understand the material in the text. The answers for the end of chapter questions are located in the appendixes. THE EVALUATION: The end of book evaluation is available on Navy Knowledge Online. The evaluation serves as proof of your knowledge of the entire contents of this NRTC. When you achieve a passing score of 70 percent, your electronic training jacket will automatically be updated. THE INTERACTIVITY: This manual contains interactive animations and graphics. They are available throughout the course and provide additional insight to the operation of equipment and processes. For the clearest view of the images, animations, and videos embedded in this interactive rate training manual, adjust your monitor to its maximum resolution setting. VALUE: In completing this manual, you will improve your military and professional knowledge. Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you are studying and discover a reference in the text to another publication for further information, look it up. June 2015 Edition Prepared by AVCM (AW/SW) Thomas Rousseau AT1 (AW/SW) Christopher Latiolais AT1 (AW) Joseph Comer NAVSUP Logistics Tracking Number 0504-LP-115-0006 i NAVEDTRA 14030A COPYRIGHT MATERIAL Copyright material within this document has been identified and approved and is listed below. Copyright Owner Date Chapter Pages ii Remarks iii TABLE OF CONTENTS CHAPTER PAGE 1. Communications ............................................................................................... 1-1 2. Navigation ......................................................................................................... 2-1 3. Radar ................................................................................................................ 3-1 4. Antisubmarine Warfare...................................................................................... 4-1 5. Indicators........................................................................................................... 5-1 6. Infrared .............................................................................................................. 6-1 7. Weapons Systems ............................................................................................ 7-1 8. Computers......................................................................................................... 8-1 9. Automatic Carrier Landing System/Instrument Landing System ....................... 9-1 10. Electrostatic Discharge.................................................................................... 10-1 APPENDIXES I. Glossary ........................................................................................................... AI-1 II. Symbols, Formulas, and Tables ...................................................................... AII-1 III. References ..................................................................................................... AIII-1 IV. Answers to End of Chapter Questions ........................................................... AIV-1 Index ................................................................................................................... Index 1 iv This manual contains active content, you must "trust" this document or select "play" to view the active content. If you can read this warning, you may not have yet activated this document. CHAPTER 1 COMMUNICATIONS As an aviation electronics technician (AT), you will be tasked to operate and maintain many different types of airborne communications equipment. These systems may differ in some respects, but they are similar in many ways. For example, there are various models of amplitude modulation (AM) radios, yet they all serve the same function and operate on the same basic principles. This chapter will focus on the basic principles involved in radio communications and provide examples of the common systems used in Navy aircraft. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Recognize the various types of electrical communications. 2. Describe the uses of various frequency bands. 3. Describe the basic terms associated with radio transmitters and receivers. 4. Describe the basic operating functions of radio transmitters. 5. Describe the basic operating functions of radio receivers. 6. Identify the components of aircraft communication systems. 7. Describe the operating principles of aircraft communications systems. RADIO COMMUNICATIONS In basic terms, communication is defined as the meaningful transfer of intelligence (information) from one location (the sender or source) to another location (the destination or receiver). Electrical communication occurs when intelligence is converted from its original form (speech) into electrical energy. The electrical energy can then be transmitted via wires or radiated through space to a receiver. The receiver converts the electrical energy back into its original form. The electrical communication process occurs in a fraction of a second because electrical energy travels at the speed of light (approximately 186,000 statute miles per second). Types of Electrical Communications Communications have become a highly sophisticated field of electronics. All Navy aircraft have the capability to access the ship-to-ship, ship-to-air, air-to-air, air-to-ground, and ship-to-shore circuits by using compatible and flexible communication systems. The following paragraphs will describe four types of electrical communication systems: radiotelegraph, radiotelephone, teletypewriter, and facsimile. Radiotelegraph Radiotelegraph is commonly called continuous wave telegraphy. Telegraphy is accomplished by opening and closing a switch to separate a continuously transmitted wave into dots and dashes based on Morse code. The major disadvantage of this type of communication is the relatively slow transmission speed and the need for experienced operators at both ends. 1-1 Radiotelephone Radiotelephone (radio) is one of the most useful military communication methods. It is used by aircraft, ships, and shore stations because of its directness, convenience, and ease of operation. An example of a radiotelephone in operation is shown in Figure 1-1. The equipment used for tactical purposes usually operates on frequencies that are high enough to have line-of-sight characteristics. This characteristic reduces the risk of an enemy being able to intercept the messages being transmitted. One of the disadvantages to using this type of system is that the effective transmission and receiving range is limited. In addition, the transmissions are susceptible to wave propagation characteristics that may make communications unpredictable. Teletypewriter Teletypewriter (TTY) signals may be transmitted by landlines, cable, or radio. The Figure 1-1 — Typical radiotelephone in Navy uses radio teletypewriter (RTTY) for highoperation. speed automatic communications across ocean areas. The keyboard used with a standard TTY system is similar to that of a typewriter. When the operator strikes a key, a sequence of signals is transmitted. At the receiving station, the signals are translated back into letters, figures, and symbols and the system replicates the message automatically. Facsimile Facsimile (fax) is the process used to transmit photographs, charts, and other graphic information electronically. The image that is going to be transmitted is scanned by a photoelectric cell. Electrical changes in the scanning cell output corresponding to the light and dark areas being scanned are transmitted to the receiver. At the receiver, the signal operates a recorder that reproduces the picture. The fax signals may be transmitted either by landline or radio. NAVY FREQUENCY BAND USE The radiofrequency (RF) spectrum is any frequency of electromagnetic energy capable of transmission into space. The frequency bands used by that military are shown in Table 1-1. Each band of frequencies has its own characteristics. For further information on the RF spectrum refer to Navy Electricity and Electronics Training Series, Module 17, Radio-Frequency Communications Principles. 1-2 Table 1-1 — RF Spectrum FREQUENCY DESCRIPTION 30 gigahertz (GHz) – 300 GHz Extremely high frequency (EHF) 3 GHz – 30 GHz Super high frequency (SHF) 300 megahertz (MHz) – 3 GHz Ultrahigh frequency (UHF) 30 MHz – 300 MHz Very high frequency (VHF) 3 MHz – 30 MHz 300 kilohertz (kHz) – 3 MHz 30 kHz – 300 kHz 3 kHz – 30 kHz 300 hertz (Hz) – 3 kHz Up to 300 Hz High frequency (HF) Medium frequency (MF) Low frequency (LF) Very low frequency (VLF) Voice frequency Extremely low frequency (ELF) VLF and LF Band Communications The VLF and LF bands were originally used for radio telegraphy. Today, the VLF band is used to communicate with satellites and is a backup to shortwave communication systems. The LF bands are used to provide eight channels of frequency division multiplex RTTY traffic for the fleet multichannel broadcast system. Because the wavelengths were in the kHz range and higher (30 kHz has a wavelength of 10 kilometers, or about 6.2 miles), enormous antennas had to be used. This is no longer a factor with current technology. MF and HF Band Communications The MF and HF bands are not only used by the Navy, but portions are also used by commercial AM broadcasting stations. These spectrums also include the international distress frequencies (500 kHz, 2182 kHz, 8364 kHz, 3023.5 kHz, and 5680 kHz). Interaction Available Signal radiation in these frequency ranges have the important characteristic of being reflected by the ionosphere. The ionosphere is a layer of electrically charged particles at the top of the Earth’s atmosphere. It starts at approximately 37 miles above the Earth’s surface and is caused by strong solar radiation entering the upper atmosphere. When a radio wave in the MF or HF range hits this layer, it is reflected back to Earth. An example of the reflection of radio waves off the ionosphere is shown in Figure 1-2. Multiple radio wave reflections between the ionosphere and Earth are possible. MF and HF transmissions can travel long distances because of the reflective characteristics of the ionosphere. This is particularly true in the HF band. Figure 1-2 — RF reflection off the ionosphere. 1-3 The disadvantage of this type of propagation is that it is dependent on the characteristics of the ionosphere, which varies widely, especially during daylight hours. Variations in the ionosphere can cause RF waves to reflect differently and take different paths over a period of time. This will cause the signal at the receiver to vary in strength and the transmission to fade in and out. VHF and UHF Band Communications Signal radiation in the VHF and UHF frequency ranges does not normally reflect off the ionosphere. As a result, communications in these ranges tend to be line-of-sight and normally cover short distances. The term line-of-sight describes a straight, unobstructed path between the transmitter and receiver. Although the VHF and UHF bands have disadvantages, they are the most commonly used media for tactical communications. TRANSMITTER AND RECEIVER FUNDAMENTALS A radio transmitter and receiver both serve very important functions in a communication system. Transmitters are responsible for generating the proper amount of RF energy to transmit intelligence from one to point to another. Receivers must have the capability to filter unwanted transmissions and to decode the intelligence into a usable form. Before the types and characteristics of transmitters and receivers are explained, an overview of terms is provided to describe the basic functions. Basic Terms The following is a list of the basic terms used to describe the functions and components of radio transmitters and receivers: • Antenna • Harmonics • Subharmonics • Suppression • Fading • Attenuation • Tuned circuits • Oscillators • Varactors • Microphone • Speaker Antenna Antennas (Figure 1-3) are conductors or sets of conductors used to collect or radiate RF energy. 1-4 Figure 1-3 — Typical radio tower antennas. Harmonics The term harmonics is used to describe multiples of the basic frequency. The basic frequency is also known as the fundamental frequency. There are two types of harmonics, even and odd. Even harmonics are described as the fundamental frequency times an even number (2, 4, 6, etc.) Odd harmonics are the fundamental frequency times odd numbers (1, 3, 5, etc.) Subharmonics The term subharmonics is used to describe the submultiple of the fundamental frequency. Subharmonics are expressed in a similar manner as harmonics (even and odd). However, subharmonics are not whole numbers. Instead they are expressed as a fraction of a whole number. For example, even subharmonics would be 1/2, 1/4, etc. of the fundamental frequency. Odd subharmonics would be 1/3, 1/5, etc. of the fundamental frequency. Suppression The term suppression describes the electrical elimination of an undesired portion of a radio signal. Fading The term fading describes the variation of signal strength at the receiver due to the difference in the phase relationships. Attenuation The term attenuation describes the reduction of a radio signal strength due to atmospheric or system loss conditions. Tuned Circuits A tuned circuit is used as a filter in a radio communication system. A tuned circuit allows or rejects specific frequency ranges. Oscillator An oscillator is a component that is used to provide a constant frequency for radio transmitters and receivers. A basic oscillator consists of the following basic components: frequency determining network, amplifier, and feedback network. • A frequency determining network is an inductive or capacitive circuit that contains a crystal. A crystal is a natural or man-made element that is manufactured to vibrate at specific resonant frequency. • An amplifier increases the output of the signal to the desired level. • A feedback network is used to route parts of the signal back to the frequency determining network to maintain oscillation. Varactors A varactor is a semiconductor diode whose capacitance is varied with the amount of voltage applied. This component is used to vary the frequency output of the oscillator. Microphone Microphones are devices that are used to convert sound energy into electrical energy. 1-5 Speaker Speakers are devices that are used to convert electrical energy into sound energy. Types of Transmitters There are three basic types of transmitters used in aircraft radio communications. They are AM, frequency modulated (FM), and single sideband (SSB) types. Amplitude Modulation Transmitter The AM transmitter varies the amplitude of the RF output in proportion to the modulating signal. The modulating signal may consist of many frequencies of various amplitudes and phases. An example of a modulating signal is a speech pattern. The basic operation of an AM transmitter is described below. In addition, a simplified AM transmitter block diagram is shown in Figure 1-4. A basic AM transmitter consists of the following components: • Microphone • Audio power amplifier • Oscillator • Buffer amplifier • Modulator • RF power amplifier • Antenna • Power supply Figure 1-4 — AM transmitter simplified block diagram. 1-6 An audiofrequency (AF) is provided to the transmitter through the use of a microphone. The electrical energy is amplified and modulated to the appropriate level. The modulated signal is routed to the power amplifier to produce the AM signal, which is transmitted via the antenna. Frequency Modulation Transmitter The FM transmitter combines the carrier frequency with the modulating signal to cause the frequency of the resultant wave to vary with the instantaneous amplitude of the modulating signal. The basic operation of a FM transmitter is described below. In addition, a simplified FM transmitter block diagram is shown in Figure 1-5. A basic FM transmitter consists of the following components: • Microphone • Oscillator • Varactor • Frequency multiplier • RF power amplifier • Antenna • Power supply Figure 1-5 — FM transmitter simplified block diagram. First, a sound signal (modulating) is applied to a varactor to vary the capacitance. The varactor causes the oscillator frequency to vary around the fundamental frequency in accordance with the modulating signal. The output of the oscillator is routed to the frequency multiplier which increases the frequency. Finally, the signal is routed to the power amplifier and increased to the desired output level for transmission via the antenna. Single Sideband Transmitter Any carrier signal that has been modulated is accompanied by two identical sidebands (upper and lower). Each sideband carries the identical intelligence. An SSB transmitter is used to transmit either the upper or lower sideband, with the other sideband being suppressed. An SSB transmission is less susceptible to atmospheric interference than an AM transmission. The basic operation of an SSB 1-7 transmitter is described below. In addition, a simplified SSB transmitter block diagram is shown in Figure 1-6. An SSB transmitter consists of the following components: • Microphone • Audio power amplifier • SSB generator • Oscillator • Frequency multiplier • Filter • Mixer/band-pass filter • Antenna • Power supply Figure 1-6 — SSB transmitter simplified block diagram. The audio amplifier increases a signal to a level that is sufficient to operate the SSB generator. The signal is then routed to the frequency generator, which produces a carrier frequency that is applied to both the SSB generator and the frequency multiplier. The SSB generator combines both the audio input and the carrier input to create the upper and lower sidebands. The upper and lower sidebands are then routed through the filter, which selects the desired sideband for transmission and suppresses the other. The signal is then routed to the mixer for conversion to the desired radio frequency. The signal then passes through the band-pass filter where it is filtered before transmission. Finally, the signal is routed to the amplifier where it is increased to the desired output level for transmission via the antenna. 1-8 Receivers Receivers are components that are built to process the signals received via the antenna assembly. The output of the receiver is the intelligence that was modulated and amplified by a transmitter. Receivers have four basic functions: reception, selection, detection, and reproduction. Reception Receiver reception occurs when an RF wave passes through the receiver antenna and induces a voltage level into the antenna. Selection The selection function in a receiver selects the particular frequency of a station that is different from the rest of frequencies that appear at the antenna. Detection Detection occurs when the receiver separates the AF signal from the RF carrier signal through the use of a detector circuit. Reproduction Reproduction describes the process of converting the electrical signal into audio. Receiver Characteristics and Components Receiver Characteristics The four characteristics important to receivers are sensitivity, noise, selectivity, and fidelity. • Sensitivity is one of the important factors in converting RF signals. Sensitivity describes the ability of a receiver to reproduce a weak signal into a useable output. Sensitivity in a receiver is expressed in terms of voltage, usually in the microvolt range. The level change in the signal or sound level is expressed as a decibel (dB). • All receivers generate some amount of noise, which in turn affects the sensitivity of a receiver. Receivers should have the ability to produce at least 10 times as much output signal power compared to noise. Noise can be generated from atmospheric conditions, like lighting, or by components that are internal to a receiver. • Selectivity describes the degree of distinction that a receiver can make between the desired and unwanted signals. The degree of selectivity is based on how well the frequency determining circuits have been built and tuned. • Fidelity describes the ability of a receiver to accurately replicate the signal output as input. One of the characteristics of effective fidelity is the ability to pass all the modulated frequencies that were transmitted. In general terms, a receiver should be designed to have an acceptable compromise between good selectivity and high fidelity. Receiver Components A typical receiver consists of the following sections: antenna, selector, detector, and reproducer. • The antenna section consists of components that are designed to intercept and route incoming radio waves (RF energy). 1-9 • The selector section of a receiver is used to select the desired frequency, which in turn is coupled to the detector section. • The detector section of the receiver is used to recover and extract the intelligence that was passed through the antenna and selector sections. In addition, the detector section filters out unwanted frequencies. • The reproducer section of a receiver takes the filtered intelligence and converts it to an audio output. Types of Receivers The superheterodyne receiver is one of the most familiar types of receivers in use today. Heterodyning is a term that describes the process of combining the incoming signal with the signal generated in the local oscillator. The result of this process is an intermediate frequency (IF) signal. Superheterodyne receivers come in two forms, AM and FM. Amplitude Modulation Receiver An overview of the basic operation of a typical AM receiver is described below. A simplified AM receiver block diagram is shown in Figure 1-7. An AM receiver consists of the following components: • Antenna • RF amplifier • Local oscillator • Mixer • IF amplifier • Detector • AF amplifier • Speaker Figure 1-7 — AM receiver simplified block diagram. 1-10 A signal received by the antenna section is first routed to the RF amplifier for signal amplification. The amplified signal is then sent to the mixer where the original signal and local oscillator signals are combined by heterodyning (mixing). The IF signal is then amplified and routed to the detector section. Finally, the detector section filters the IF signal and routes it to the AF amplifier before the output (audio) is sent to the speaker. Frequency Modulation Receiver An overview of the basic operation of a typical FM receiver is described below. A simplified FM receiver block diagram is shown in Figure 1-8. An FM receiver consists of the following components: • Antenna • RF amplifier • Local oscillator • Mixer • Wide-band IF amplifier • Limiter • Discriminator • AF amplifier • Speaker Figure 1-8 — FM receiver simplified block diagram. The incoming signal is amplified by the RF amplifier and routed to the mixer. The mixer combines the amplified RF signal with the local oscillator signal using the process of heterodyning. The resultant IF signal is amplified by the wide-band IF amplifier section. The amplified signal is routed to the limiter circuit in the receiver. The limiter circuit removes all of the signals that do match the same amplitude 1-11 levels, which in turn reduces the amount of noise interference. The signal is then routed to the discriminator circuit, which is built to respond to the shifts in frequency variation. The AF component is then extracted and routed to the speaker for output. AIRCRAFT COMMUNICATIONS SYSTEMS Aircraft communication systems are critical components for the aircrew. Without an effective communication system the aircrew would be unable to safely and effectively complete the assigned mission. The next paragraphs will provide an overview of the following: ARC-210 communication system, digital communication system (DCS), multifunctional information distribution system (MIDS), intercommunication system, and the data link. ARC-210 Communication System The ARC-210 communications system is used for RF transmission and reception of plain voice and encrypted AM and FM signals and is used in a variety of Navy aircraft. The following paragraphs will provide an overview of the ARC-210 communication system components and modes of operation used in the F/A-18 series of aircraft. The ARC-210 system is made up of the following components: • VHF/UHF receiver-transmitter no. 1 and no. 2 (Figure 1-9) • Communications antennas (3) • Antenna selector • ANT SEL COMM 1 switch VHF/UHF Receiver/Transmitter No. 1 and No. 2 The F/A-18 series aircraft can be configured with two ARC-210 radios, which will act as receivertransmitter number 1 (COMM 1) and receivertransmitter number 2 (COMM 2). The ARC-210 radio operates in the 30 Hz to 399.975 MHz AM and FM frequency ranges. The frequency bands and modes of operation are shown in Table 1-2. Each radio provides the operator with the ability to receive and transmit voice communications to other aircraft or ground stations in plain voice or anti-jam mode. The ARC-210 radios also have the capability of monitoring the guard frequency (121.50 MHz) while still using other communication frequencies through the use of a separate guard receiver. The guard channel is segregated from the other channels and is only used in case of emergency. Figure 1-9 — VHF/UHF receiver-transmitter. COMM 1 and COMM 2 operate in both the frequency modulation (FM) and amplitude modulation (AM) frequency bands. COMM 1 and COMM2 can operate in relay mode, which will retransmit intelligence received to other aircraft or ground stations. 1-12 Table 1-2 — ARC-210 Frequency Bands and Operating Modes FREQUENCY (MHz) MODE OF OPERATION 30.00 – 87.975 FM 108.000 – 117.975 (receive only) AM 118.000 – 155.975 AM 156.000 – 173.975 FM 225.000 – 399.975 AM or FM The ARC-210 radios have three modes of operation: fixed frequency, maritime, and anti-jam. • Fixed frequency mode allows the operator to transmit and receive voice communications by selecting one of the 20 preset channels using the upfront control display (UFCD). • Maritime mode allows the operator to select one of the 57 preset channels to communicate with ships or stations. Selection of this mode is made on the UFCD. • Anti-jam mode uses two sub modes of operation to provide jam resistant communications, single channel ground and airborne radio system (SINGCARS), and havequick. o The SINCGARS mode of operation provides line-of-sight, jam resistant VHF FM band voice communications. o The havequick mode of operation provides line-of-sight, jam resistant UHF AM band voice communications. Communications Antennas The ARC-210 radio system uses three dual blade antennas for receiving and transmitting. The upper and lower forward antenna is used by COMM 1 and the data link system. The lower aft antenna is used by COMM 2. Antenna Selector The antenna selector is an RF switching unit that connects the receiver-transmitter to an antenna. COMM 1 is either manually or automatically connected to the upper or lower forward antenna. ANT-SEL COMM 1 Switch The COMM 1 switch of the ANT-SEL control panel assembly (Figure 1-10) is used to select the upper or lower antenna for use by COMM 1. AUTO position allows the COMM 1 and the data link to switch automatically between upper and lower antenna as required. Figure 1-10 — ANT-SEL control panel. 1-13 Digital Communications System The F/A-18 series aircraft can be configured with the RT-1824(C) DCS compatible radio (Figure 111). When DCS is installed in the F/A-18 series aircraft it will take the place of COMM 2 but still provides all of the standard voice communications. DCS was designed to lower the workload for the operator during close air support (CAS) missions by visually displaying mission information in a text format. In addition, DCS provides secure voice communications between the operator and a forward air controller (FAC). The system provides the operator with 9-line text briefs provided by the FAC on the appropriate display. The 9-line brief consists of target, mission, and navigation data. The purpose of this information is to decrease the possibility of miscommunication during a CAS mission. Figure 1-11 — DCS radio set. Multifunctional Information Distribution System The MIDS is designed to improve the situational awareness of aircrew and improve the effectiveness of the command and control centers. The MIDS network accomplishes this by using secure digital communications to display the location and status of participating friendly air and surface forces. The MIDS consists of the following components: radio terminal unit, remote power supply, switchable notch filter, and fixed notch filter. Radio Terminal Unit The radio terminal unit is the main component of the MIDS. The radio terminal unit is used to exchange real time information among the secure network participants. An example of a typical MIDS secure network is shown in Figure1-12. In addition, the radio terminal unit houses the components and provides the functions of the Tactical Air Navigation (TACAN) system. The radio terminal unit provides the operator with four functions: secure data link, secure voice communications, relative navigation, and TACAN. • The secure data link enables the MIDS to exchange and display real time tactical information among the participating units active in an established secure network. • The secure voice function allows active network participants to use jam resistant communications. • Relative navigation improves the navigational accuracy of a host aircraft using the secured MIDS network. The host aircraft compares the location of other network participants to its location by measuring the time it takes for a participant to receive a message. The resultant data is then used by the host aircraft navigational systems to make corrections if relative navigation is the only active position keeping source. • The TACAN system is used to provide the operator with the distance and bearing to a compatible aircraft, ship, or shore station. 1-14 Figure 1-12 — Typical MIDS secure network. Remote Power Supply The remote power supply provides the operating power for the MIDS radio terminal unit and associated equipment. Switchable Notch Filter The switchable notch filter is used to prevent the interference between the MIDS and the Identification Friend or Foe (IFF) RF transmissions. The switchable notch filter also switches out when the operator is using the TACAN function of the radio terminal unit. Fixed Notch Filter The fixed notch filter is used to limit the number of TACAN channels transmitted by the upper antenna. Intercommunication System The F/A-18 series aircraft intercommunication system is used to provide the aircrew with amplification and distribution of inter-cockpit communications, aircrew-to-ground communications, voice alerts, warning tones, and advisory tones. The intercommunication system consists of the following components: intercommunication amplifier-control (IAC) and the communications control (COMM CONT) panel. 1-15 Intercommunication Amplifier-Control The IAC is used to amplify audio outputs and to provide the aircrew with communication-, navigation-, and identification-related warnings and advisories. In addition, the IAC provides a means to adjust the volume for avionics systems warnings, advisories, and ground crew communications. The IAC interacts with the following systems: • Tactical Air Navigation – audio tones associated with TACAN station identification are amplified and routed by the IAC. • Identification Friend or Foe – the IAC provides the aircrew with audio tones associated with the IFF system operation. • Multifunctional information distribution – secure voice audio associated with the MIDS is amplified and routed by the IAC. • Landing gear –the IAC provides the aircrew an unsafe landing gear tone when the landing gear operating outside of normal parameters. • Stores management – the armament computer routes weapons audio to the IAC for amplification and output. • Tactical electronic warfare – the IAC provides warning and advisory tones initiated by the ALR67 electronic warfare computer system. • Mission computer – the mission computer system routes voice alerting commands to the IAC for amplification and output to aircrew headsets. • Fire detection – a voice alert message is amplified and routed to aircrew headsets when a fire is detected in the engine or auxiliary power unit bays. • Bleed air detection – a voice alert message is amplified and routed to aircrew headsets when a bleed air system overheat condition is detected. An IAC systems interaction block diagram is shown in Figure 1-13. COMM CONT Panel The COMM CONT panel is used to provide ground crews with the ability to communicate with the aircrew in the cockpit. The COMM CONT panel is part of the ground services panel as shown in Figure 1-14. Data Link A data link system is used for the electronic exchange of secure data between two capable and participating units (aircraft, ship, shore station, etc.) The following paragraphs provide a basic overview of the data link system used in the P-3C Orion aircraft. The ACQ-5 data link system consists of the following components: • C-7790A data terminal set control-monitor • CV-2528 data terminal set convertor-control • PP-6140 data terminal set power supply • A507 data terminal set communications interface 2 1-16 C-7790A Data Terminal Set Control-Monitor The control-monitor enables the operator to select the modes of operation and monitors the system for operational failures. CV-2528 Data Terminal Set Converter-Control The convertorcontrol modulates and demodulates digital data and converts the data to audio tones. The audio tones are then routed to the aircrew headsets. Figure 1-13 — IAC systems interaction block diagram. PP-6140 Data Terminal Set Power Supply The power supply provides the data terminal set with the required regulated voltages for operation. A507 Data Terminal Set Communications Interface 2 The communications interface 2 is used to provide a digital connection between the aircraft central computer and the data link system. Figure 1-14 — COMM CONT panel. 1-17 End of Chapter 1 Communications Review Questions 1-1. What type of energy transmission is used in radio communications? A. B. C. D. 1-2. The speed of light travels at approximately how many miles per second? A. B. C. D. 1-3. Teletypewriter Radiotelegraph Facsimile Radiotelephone What type of code uses a series of dots and dashes to relay intelligence? A. B. C. D. 1-6. Teletypewriter Radiotelegraph Facsimile Radiotelephone What radio equipment signal may be transmitted by landlines, cable, or radio? A. B. C. D. 1-5. 146,000 166,000 186,000 206,000 What communication method is the most useful to the military? A. B. C. D. 1-4. Thermal Electrical Mechanical Chemical Binary Morse Python Semaphore What frequency band is used to communicate with satellites? A. B. C. D. Very low Low Medium Very high 1-18 1-7. Other than the high frequency band, what frequency band is also used by commercial broadcasting stations? A. B. C. D. 1-8. What atmospheric layer is caused by strong solar radiation? A. B. C. D. 1-9. Very low Low Medium Very high Troposphere Stratosphere Mesosphere Ionosphere What frequency band is used to provide eight channels for fleet multichannel broadcast? A. B. C. D. Low Medium Very high Ultra high 1-10. Other than the ultrahigh frequency band, what frequency band is commonly used for tactical communications? A. B. C. D. Extremely low Low High Very high 1-11. What term describes multiples of the fundamental frequency? A. B. C. D. Fading Harmonics Suppression Varactors 1-12. What type of circuit allows or rejects specific frequency ranges? A. B. C. D. Varactor Oscillator Tuned Parallel 1-13. What term describes the reduction of the signal strength due to the atmospheric conditions? A. B. C. D. Subharmonics Suppression Fading Attenuation 1-19 1-14. What component is used to maintain a constant frequency for transmitters and receivers? A. B. C. D. Oscillator Capacitor Diode Varactor 1-15. Which of the following fractions can be used to express an odd subharmonic? A. B. C. D. One-half One-third One-sixth One-eighth 1-16. What component of a frequency modulating transmitter varies sound signal capacitance? A. B. C. D. Varactor Oscillator Frequency multiplier Radiofrequency amplifier 1-17. What component of an amplitude modulated transmitter provides audiofrequency? A. B. C. D. Audio power amplifier Oscillator Buffer amplifier Microphone 1-18. What component of an amplitude modulated transmitter combines the audio and radiofrequency signals? A. B. C. D. Buffer amplifier Modulator Oscillator Power supply 1-19. What frequency modulated transmitter component increases the routed signal? A. B. C. D. Oscillator Varactor Frequency multiplier Radiofrequency power amplifier 1-20. What component of the single sideband transmitter creates the upper and lower sidebands? A. B. C. D. Power amplifier Generator Oscillator Frequency multiplier 1-20 1-21. What measurement is used to express changes in sound levels? A. B. C. D. Microfarad Milliamp Decibel Foot pound 1-22. What receiver characteristic is expressed in volts? A. B. C. D. Noise Fidelity Selectivity Sensitivity 1-23. How many more times should a receiver signal output be compared to potential noise? A. B. C. D. 10 20 30 40 1-24. What receiver characteristic is the degree of distinction between desired and unwanted signals? A. B. C. D. Noise Fidelity Selectivity Sensitivity 1-25. A receiver is designed to have a compromise between selectivity and what characteristic? A. B. C. D. Noise Fidelity Selectivity Sensitivity 1-26. What frequency signal results from heterodyning? A. B. C. D. Midway Equidistant Transitional Intermediate 1-27. What section of an amplitude modulated receiver filters the intermediate frequency? A. B. C. D. Detector Mixer Speaker Local oscillator 1-21 1-28. What section of a frequency modulated receiver reduces the amount of noise interference? A. B. C. D. Speaker Mixer Discriminator Limiter 1-29. What section of a frequency modulated receiver extracts the audiofrequency component of the signal? A. B. C. D. Speaker Mixer Discriminator Limiter 1-30. How many antennas are used in the F/A-18 ARC-210 communication system? A. B. C. D. 2 3 4 5 1-31. How many ARC-210 receiver transmitters are used in the F/A-18? A. B. C. D. 2 3 4 5 1-32. What frequency in megahertz is the ARC-210 radio’s highest operating range? A. B. C. D. 117.975 155.975 173.975 399.945 1-33. How many preset channels are available in the ARC-210 fixed frequency mode? A. B. C. D. 10 15 20 25 1-34. Other than plain voice, what mode of communication is provided by the ARC-210 radio? A. B. C. D. Anti-jam Clear Target Jettison 1-22 1-35. What system provides a method of secure communication between the operator and a forward air controller? A. B. C. D. Analog Manual Digital Automatic 1-36. What system provides the intercommunication amplifier-control with weapons audio? A. B. C. D. Identification friend or foe Landing gear Stores management Tactical Air Navigation 1-23 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. 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CHAPTER 2 NAVIGATION The term navigation is defined as the process of directing the movement of a craft from one point to another. Some type of navigation has been in use since humans started to venture away from their homes. Exactly how they managed to find their way will remain a matter of conjecture, but some of their methods are known. The Greeks used primitive charts and a crude form of dead reckoning by using the sun and the North Star to determine direction. Early explorers created the astrolabe shown in Figure 2-1 to guide their way. However, many of the early methods were extremely inaccurate. Accurate navigation became a reality in the early 1700s when the chronometer and sextant were invented. These tools allowed explorers to travel even greater distances from their homes. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Describe some common navigational terms. 2. Recognize the various methods of navigation. 3. Describe the operating principles of airborne navigation systems. Figure 2-1 — Ancient astrolabe. NAVIGATIONAL TERMS Air navigation, unlike naval navigation, involves movements above the surface of the Earth. This creates a set of conditions that make air navigation unique. For example, a ship can stop and resolve any uncertainty of motion or wait for more favorable conditions if necessary; most types of aircraft, on the other hand, must keep going. Therefore, air navigation methods and procedures must be done quickly and accurately. Another obstacle that aircraft face is weather changes that affect visibility of landmarks. However, advances in technology and improvements in aircraft avionics have made it less complicated for aircrew to navigate during inclement weather. There are certain terms that you must learn to understand navigation. Aircrew use these terms to express and accomplish the practical aspects of air navigation. The following paragraphs define the terms position, direction, distance, and time in relation to navigation. Position Position is a location defined by stated or implied coordinates. It always refers to some place that can be identified. Aircrew must know the aircraft’s immediate position before they can direct it to another position. 2-1 Direction Direction is the position of one point in space relative to another without reference to the distance between them. Direction is not in itself an angle, but it is measured in terms of its angular distance from a reference direction. Distance Distance is the spatial separation between two points and is measured by the length of a line joining them. This is a simple problem on a plane surface. However, consider distance on a sphere, where the separation between points may be expressed as a variety of curves. Time Time is defined in many ways, but for air navigation purposes, it is either the hour of the day or an elapsed interval. The terms above represent definite quantities or conditions that can be measured in several different ways. For example, the position of an aircraft may be expressed in coordinates such as latitude and longitude, or as being 10 miles south of a certain landmark. EARTH’S SIZE AND SHAPE For navigational purposes, the Earth (Figure 2-2) is assumed to be a perfect sphere, although it is not. There is an approximate 12-mile difference between the highest point and the lowest point of the Earth’s crust. The variations in the surface (valleys, mountains, oceans, etc.) give the Earth an irregular appearance. Measured at the equator, the Earth is approximately 6,887.91 nautical miles in diameter. The polar diameter is approximately 6,864.57 nautical miles. This difference between the two measurements is 23.34 nautical miles. This measurement may be used to express the ellipticity of the Earth. Figure 2-2 — View of the Earth. Great Circles and Small Circles The intersection of a sphere and a plane is a circle. If the intersection of the plane passes through the center of the sphere, it is a great circle. If it does not, then it is defined as a small circle. The arc of a great circle is the shortest distance between two points on a sphere, just as a straight line is the shortest distance between two points on a plane. On any sphere, an infinite number of great circles may be drawn through any point, though only one great circle may be drawn through any two points that are not diametrically opposite. An example of great and small circles is shown in Figure 2-3. Circles on the surface of the sphere other than great circles are small circles. On the surface of the Earth, as on any sphere, a small circle is a circle whose center and/or radius are not that of the 2-2 sphere. Special sets of small circles, called latitude and longitude, are discussed in the next paragraph. Latitude and Longitude The nature of a sphere is such that any point on it is exactly like any other point. There is neither a beginning nor an ending as far as differentiation of points is concerned. Points and lines of reference are necessary so that locations may be identified on the Earth. The location of New York City with reference to Washington, DC, is stated as a number of miles in a certain direction (north, south, east, and west) from Washington, DC. Any point on the Earth can be located the same way based on this system. This system does not work easily for navigation purposes. For example, a point could not be precisely located in the mid-Pacific Ocean without any nearby geographic features to use as a reference. That is why a system of imaginary reference lines is used to locate any point on Earth. These reference lines are the parallels of latitude and the meridians of longitude. Latitude Each day the Earth rotates once on its north-south axis. This axis terminates at the two poles. The equator is constructed at the midpoint of this axis at right angles to it. A great circle drawn through the poles is called a meridian, and an infinite number of great circles maybe constructed in this manner. Each meridian is divided into four quadrants by the equator and the poles. Because a circle is divided into 360 degrees, each of the four quadrants encompasses 90 degrees. Take a point on one of these meridians 30 degrees north of the equator. Through this point passes a plane perpendicular to the north-south axis. This plane will be parallel to the plane of the equator, as shown in Figure 2-4, and will intersect the Earth in a small circle called a parallel or parallel of latitude. This particular parallel of latitude is called 30 degrees north and every point on this parallel will be at 30 degrees north. Parallels can be constructed at any desired latitude. Figure 2-3 — Great circle is the largest circle in a sphere. The equator is the great circle midway between the poles. The parallels of latitude are small circles constructed with reference to the equator. The angular distance measured on a meridian north or south of the equator is known as latitude and forms one component of the coordinate system. Longitude The latitude of a point can be shown as 20 degrees north or 20 degrees south of the equator, but there is no way of determining whether one point is east or west of another. This is resolved by the use of the other component of the coordinate system, longitude. Longitude is the measurement of the east-west distance. Unlike latitude, longitude has no natural starting point. The only way that this problem could be solved was by selecting an arbitrary starting point. Many places had been used in the past, but when the 2-3 English speaking people started to make charts, they chose the meridian through their principal observatory in Greenwich, England. This meridian has now been adopted by most of the world as the official starting point to calculate longitude. Greenwich meridian, sometimes called the prime meridian or first meridian, is the 0 meridian. Longitude is counted east or west from this meridian through 180 degrees beginning at the prime meridian. Figure 2-4 — Planes of the Earth. Therefore, the Greenwich meridian is the 0-degree meridian on one side of the Earth and, after crossing the poles, the 180th meridian on the opposite side (180 degrees east or west of the 0degree meridian). If a globe has the circles of latitude and longitude drawn on it according to the principles described, and the latitude and longitude of a certain place has been determined, this point can be located on the globe in its proper position (Figure 2-5). In this way, a globe can be formed that resembles a small-scale copy of the Earth. Latitude is measured in degrees up to 90, and longitude is measured in degrees up to 180. The total number of degrees in any one circle cannot exceed 360. A degree of arc may be subdivided into smaller units by dividing each degree into 60 minutes (′) of arc. Each minute can be further divided into 60 seconds (″) of arc. Measurements may also be made in units as small as thousandths of minutes if it is required. Figure 2-5 — Latitude is measured from the equator; longitude from the prime meridian. Distance Distance as previously defined is measured by the length of a line joining two points. In navigation, the most common unit for measuring distance is the nautical mile. All of the following units can be used interchangeably as the equivalent of 1 nautical mile: • 6,076.10 feet (nautical mile) • 1′ of arc of a great circle on a sphere having an area equal to that of the Earth 2-4 • 6,087.08 feet (geographic mile) • 1′ of arc on a meridian (1′ of latitude) • 2,000 yards (for short distances) It is sometimes necessary to convert nautical miles into statute miles or statute miles into nautical miles. This conversion is made with the following ratio: 𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦 𝟔𝟔, 𝟎𝟎𝟎𝟎𝟎𝟎 𝐟𝐟𝐟𝐟 = = 𝟏𝟏. 𝟏𝟏𝟏𝟏 𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦 𝟓𝟓, 𝟐𝟐𝟐𝟐𝟐𝟐 𝐟𝐟𝐟𝐟 The rate of change of position is determined by speed. Speed is expressed in miles per hour either statute miles or nautical miles. A knot is 1 nautical mile per hour (1 knot is equal to 1.15 statute miles per hour). Therefore, a speed of 200 nautical miles per hour and a speed of 200 knots are the same. Note that the phrase “200 knots per hour” is incorrect unless referring to acceleration. Direction Direction is the position of one point in space relative to another without reference to the distance between them. The time-honored system for specifying direction (north, south, east, and west) does not meet the needs of modern navigation. Therefore, a numerical system is used to meet navigational needs. The numerical system (Figure 2-6) divides the horizon into 360 degrees, starting with north as 000 degrees. Going clockwise, east is 090 degrees, south 180 degrees, west 270 degrees, and back to north. The circle, called a compass rose, represents the horizon divided into 360 degrees. The nearly vertical lines represent the meridians, with the meridian of position “A” passing through 000 degrees and 180 degrees. Position “B” lies at a true direction of 062 degrees from “A,” and position “C” is at a true direction of 295 degrees from “A.” Figure 2-6 — Numerical system used in air navigation. Determination of direction is one of the most important parts of air navigation. Therefore, the terms involved must be clearly understood. Generally in navigation, unless otherwise stated, all directions are called true directions. • Course is the intended horizontal direction of travel. • Heading is the horizontal direction in which an aircraft is pointed. • Track is the actual horizontal direction made by the aircraft over the Earth. • Bearing is the horizontal direction of one point to another. The direction from the aircraft to some point on the Earth’s surface is marked by the line of sight (visual bearing). Bearings are usually expressed in terms of one of two reference directions: (1) true north, or (2) the direction in which the aircraft is pointed. If true north is being used as the reference, the bearing is called 2-5 a true bearing. If the heading of the aircraft is the reference, the bearing is called a relative bearing (Figure 2-7). Figure 2-7 — Measuring relative bearing. Altitude and Atmosphere A basic understanding of altitude is required to understand how the various types of altimeters (instruments used to measure altitude). Altitude is defined as the vertical distance of a level, a point, or an object measured from a given surface. Knowing the aircraft’s altitude is imperative for terrain clearance, aircraft separation, and a multitude of operational reasons. Standard Datum Plane The standard datum plane is a theoretical plane where the atmospheric pressure is 29.92 inches of mercury (Hg) and the temperature is 15 degrees Celsius (°C) or 59 degrees Fahrenheit (°F). The standard datum plane is the zero-elevation level of an imaginary atmosphere known as the standard atmosphere. In the standard atmosphere, pressure is at 29.92 Hg at 0 feet, and decreases upward at the standard pressure lapse rate. The temperature is 15 °C at 0 feet, and also decreases upward but at the standard temperature lapse rate. Standard lapse rates are shown in Table 2-1. 2-6 Table 2-1 — Standard Lapse Rates Temperature Standard Altitude (ft) Pressure (Hg) (°C) (°F) 0 29.92 15.0 59.0 1,000 28.86 13.0 55.4 2,000 27.82 11.0 51.9 3,000 26.82 9.1 48.3 4,000 25.84 7.1 44.7 5,000 24.89 5.1 41.2 6,000 23.98 3.1 37.6 7,000 23.09 1.1 34.0 8,000 22.22 -0.9 30.5 9,000 21.38 -2.8 26.9 10,000 20.57 -4.8 23.3 11,000 19.79 -6.8 19.8 12,000 19.02 -8.8 16.2 13,000 18.29 -10.8 12.6 14,000 17.57 -12.7 9.1 15,000 16.88 -14.7 5.5 16,000 16.21 -16.7 1.9 17,000 15.56 -18.7 -1.6 18,000 14.94 -20.7 -5.2 19,000 14.33 -22.6 -8.8 20,000 13.74 -24.6 -12.3 21,000 13.18 -26.6 -15.9 22,000 12.64 -28.6 -19.5 23,000 12.11 -30.6 -23.0 24,000 11.60 -32.5 -26.6 25,000 11.10 -34.5 -30.2 26,000 10.63 -36.5 -33.7 27,000 10.17 -38.5 -37.3 28,000 9.72 -40.5 -40.9 29,000 9.30 -42.5 -44.4 30,000 8.89 -44.4 -48.0 The standard atmosphere is theoretical. It was derived by averaging the readings taken over a period of years. The list of altitudes and their corresponding values of temperature and pressure given in Table 2-1 were determined by these averages. 2-7 Planes of Altitude There are as many kinds of altitudes as there are reference planes from which to measure them. Only six of these planes concern the navigator. They are indicated altitude, calibrated altitude, pressure altitude, density altitude, true altitude, and absolute altitude. Examples of the types of altitude are shown in Figure 2-8. • Indicated altitude is the value of altitude that is displayed on the pressure altimeter. • Calibrated altitude is indicated altitude corrected for installation/positional error. • Pressure altitude is the height of the aircraft above the standard datum plane. • Density altitude is the pressure altitude corrected for temperature. Density altitude is used in performance data and true airspeed calculations. • True altitude is the actual vertical distance above mean sea level, measured in feet. It can be determined by two methods: 1. Set the local altimeter setting on the barometric scale of the pressure altimeter to obtain the indicated true altitude. 2. Measure altitude over water with an absolute altimeter. • Absolute altitude is the height above the terrain. It is computed by subtracting terrain elevation from true altitude, or it can be read directly from an absolute altimeter. Figure 2-8 — Types of altitude. Altimeters There are two main altimeters used in aircraft. They are the pressure altimeter and the absolute (radar) altimeter. 2-8 Pressure Altimeter The pressure altimeter is an aneroid barometer calibrated to indicate feet of altitude instead of pressure. The pointers are connected by a mechanical linkage to a set of aneroid cells. Aneroid cells expand or contract with changes in barometric pressure. The cells assume a particular thickness at a given pressure level, and thereby position the altitude pointers accordingly. On the face of the indicator is a barometric scale that indicates the barometric pressure of the point or plane from which the instrument is measuring altitude. If you turn the barometric pressure set knob on the altimeter, it manually changes the setting on the scale. In addition, adjusting the knob results in the simultaneous movement of the pointers to the corresponding altitude reading. Like all measurements, an altitude reading is meaningless if the reference point is unknown. The pressure altimeter face supplies both values. The pointer position indicates the altitude in feet, and the barometric scale indicates the pressure of the reference plane. There are two different types of pressure altimeters used in naval aircraft. They are the counter-pointer and the counter-drum-pointer altimeters. • • A counter-pointer altimeter (Figure 2-9) has a two-digit counter display, which indicates altitude in 1,000-foot increments from 0 to 80,000 feet. A single conventional pointer indicates hundreds of feet on the fixed circular scale. The pointer makes one revolution per 1,000 feet of altitude, and as it passes through the 900to 1,000-foot area of the dial, the 1,000foot counter is actuated. The shaft of the 1,000-foot counter actuates the 10,000foot counter at each 10,000 feet of altitude change. To determine the indicated altitude, you read the 1,000-foot counter and then add the 100-foot pointer indication. Figure 2-9 — Counter-pointer altimeter. A counter-drum-pointer altimeter is different from the counter-pointer altimeter because of the addition of a 100-foot drum. The drum follows the 100-foot pointer and actuates the 1,000-foot counter. In this way it prevents the reading error when the 1,000-foot counter switches. There are five categories of errors relating to pressure altimeters. They are the mechanical error, scale error, installation/position error, reversal error, and hysteresis error. • Mechanical error is caused by misalignments in gears and levers that transmit the aneroid cell expansion and contraction to the pointers of the altimeter. This error is not constant, and it must be checked before each flight by the setting procedure. • Scale error is caused by irregular expansion of the aneroid cells. It is recorded on a scale correction card maintained for each altimeter in the instrument maintenance shop. • Installation/Position error is caused by the airflow around the static ports. This error varies with the type of aircraft, airspeed, and altitude. The magnitude and direction of this error can be determined by referring to the performance data section in the aircraft Naval Air Training and Operating Procedures Standardization (NATOPS) manual. 2-9 NOTE An altimeter correction card is installed in some aircraft that combines the installation/position and scale errors. The card shows the amount of correction needed at different altitudes and airspeeds. • Reversal error is caused by inducing false static pressure into the system. This normally occurs during abrupt or huge pitch changes. This error appears on the altimeter as a momentary indication in the opposite direction. • Hysteresis error is a lag in altitude indication due to the elastic properties of the material within the altimeter. This occurs after an aircraft has maintained a constant altitude for an extended period of time and then makes a large, rapid altitude change. After a rapid descent, altimeter readings are higher than actual. This error is negligible during slow climbs and descents or after maintaining a new altitude for a short period of time. Absolute (Radar) Altimeter Accurate absolute altitude is important for navigation, bombing, and close air support missions. Absolute altitude can be computed from the pressure altimeter readings, but the results are often inaccurate. Under changing atmospheric conditions, corrections applied to pressure altimeter readings to obtain true altitudes are only approximate. In addition, any errors made in determining the terrain elevation will result in a corresponding error in the absolute altitude. An aircraft radar altimeter uses pulsed rangetracking radiofrequency (RF) energy that measures the surface of terrain clearance below the aircraft. Typical radar altimeter systems consist of a receiver-transmitter, transmit/receive antennas, cockpit height indicator (Figure 2-10), and interference blanker system. The interference blanker system sends blanking RF pulses that allow the radar altimeter to operate without interfering with other avionics systems. Figure 2-10 — Typical cockpit height indicator. Radar altimeters are reliable in the altitude range of 0 to 5,000 feet. Radar altimeters develop information by radiating a short duration RF pulse from a transmit antenna and measuring the time interval it takes to receive the reflected signal. The altitude information is then continuously sent to the height indicator in feet of altitude. The height indicator is disabled when the aircraft is above 5,000 feet. When the aircraft is on the ground, the system is disabled by the aircraft weight-on-wheels switch. An example of a radar altimeter transmit and receive cycle is shown in Figure 2-11. 2-10 Interaction Available Figure 2-11 — Typical radar altimeter system in operation. AIRBORNE NAVIGATION SYSTEMS Airborne navigation systems can be self-contained units or ground-referenced units. A self-contained unit is complete and does not depend on transmissions from a ground station. A ground-referenced unit requires a transmission from an outside source, such as a ground station. Both types aid aircrew in completing their mission safely and efficiently. The following navigation systems will be discussed: automatic direction finder (ADF), Tactical Air Navigation (TACAN), global positioning system (GPS), and inertial navigation system (INS). Automatic Direction Finder The ADF system is used to provide a bearing to a selected station. This system is primarily used when other navigation methods have failed. A typical ADF system uses a specific frequency band to transmit and receive bearing signals from a station. The data received from the ADF is processed by computer systems and displayed on aircraft navigational equipment. In some cases, the ADF system is an operational mode of aircraft radio communication systems. Tactical Air Navigation The TACAN system is a polar coordinate type radio air-navigation system that provides an aircrew with distance information, obtained from distance measuring equipment (DME), and bearing (azimuth) information. Aircrew can obtain navigational data from other TACAN-capable aircraft, ships, or shore stations. 2-11 TACAN Principles A TACAN system uses proven radar-ranging techniques to determine distance by measuring the round-trip travel of pulsed-RF energy. The strength of a radar return signal normally depends on the natural reflection of the radio waves. However, TACAN beacon-transponders can generate artificial replies instead of depending on the natural reflection of radio waves. A typical TACAN system uses 126 two-way operating channels in 962 to 1213 megahertz (MHz) frequency range. Each of the operating channels uses separate frequencies when transmitting or receiving. TACAN Pulse-Pairs A TACAN system uses twin pulse-pairs to communicate between receivers and transponders. The twin pulse-pairs increase the average radiation power and reduce the possibility of transmitting false signals. Bearing and Distance Information The timing of the transmitted pulses supplies the actual distance information to the aircraft. The TACAN beacon-transponder modulates the strength of the pulse to convey bearing information by producing a specific directional-radiating pattern around a vertical axis. This signal, when properly referenced, indicates the aircraft’s direction from the TACAN facility. The signal and distance data give the aircraft a two-piece fix (distance and direction) for determining specific aircraft location. Radiation Pattern Ground stations (Figure 2-12) or ships feed RF energy to a central antenna element, which does not have any directivity in the horizontal plane. The parasitic (conductive) elements positioned around the central element are switched on and off (electronically) at a rate of 15 revolutions per second (900 revolutions per minute). This process creates a 15-hertz (HZ) amplitudemodulated signal. The aircraft TACAN equipment obtains bearing information by comparing the 15 Hz modulated signal with a 15 Hz reference burst signal it receives from the ground facility. The phase relationship Figure 2-12 — Typical TACAN ground station antenna. between the 15 Hz modulated signal and the 15 Hz reference burst signal depends on the location of the aircraft. In addition, 32 outer parasitic antennas are added to the electronically scanned antenna to reduce site error. When the 32 antennas are switched on and off (electronically), a 135 Hz signal, known as the auxiliary reference burst, is created. A composite TACAN signal is composed of 2,700 interrogation replies and noise pulse-pairs-persecond. The composite signal also includes 180 north burst pulse-pairs and 720 auxiliary-burst-pulsepairs for a total of 3,600 pulse-pairs-per-second. 2-12 Global Positioning System An unlimited number of users can use GPS because it is a space-based radio navigation system that provides continuous, all-weather, passive operation anywhere in the world. The Department of Defense uses a GPS that was designed for and operated by the U.S. military. Three major segments—space, control, and user—make up GPS. Space Segment The GPS satellite constellation consists of 21 operational and 3 spare satellites, positioned approximately 12,550 miles high in a semi-synchronous orbit around the Earth. The satellites are in six orbital planes with three or four operational satellites in each plane. There are a minimum of four satellites observable from anywhere in the world. A basic GPS network is shown in Figure 2-13. Figure 2-13 — Basic GPS network. Satellites transmit two GPS carrier frequencies that are commonly referred to as L1 and L2. Both signals contain codes that provide positioning, timing, and navigation data. The L1 carrier signal operates in 1575.42 MHz frequency range and the L2 carrier signal operates in the 1227.6 MHz range. L1 and L2 carrier signals are used to transmit position, velocity, and time (PVT) signals for use by compatible equipment. The L1 and L2 carrier frequencies are transmitted from the satellites using the spread spectrum technique. The spread spectrum technique increases the availability of the signals and improves the resistance against jamming and natural interference. There L1 and L2 carrier frequencies transmit two codes: course acquisition (C/A) and precise (P). C/A codes are available to both civilian and military users. P code use is currently restricted to military and other users determined by the Department of Defense. 2-13 Control Segment This segment is made up of a master control station and a number of separate monitor stations located around the world. The master control station is responsible for tracking, monitoring, and managing the satellite constellation. The master control station is also responsible for updating navigation data messages. User Segment The user segment of GPS is the equipment used to receive, decode, and process PVT information. Aircraft GPS Satellites in the GPS constellation transmit a one-way (listen only) signal. Aircraft must have specific components installed to use this signal and the associated navigation data. Typical GPS installed in an aircraft consists of the following components: • A GPS receiver determines distance to a satellite by measuring the time difference between the time the satellite transmits the signal and the time GPS receives the signal. The time that is received is determined by the GPS clock. If the GPS clock is not perfectly synchronized with the satellite clock, the time measurement is inaccurate. A GPS receiver can be initialized with crypto keys enabling it to receive highly accurate anti-spoofing and precise navigation signals. • A GPS antenna (Figure 2-14) is normally mounted on the aircraft’s upper fuselage surface. Mounting the antenna in this area improves RF signal reception. The purpose of the GPS antenna is to provide RF navigation signals to the GPS receiver. The RF cable assemblies connect the GPS antenna to the receiver. Assemblies consist of coaxial cables that normally have a frequency range of 1 to 1.6 gigahertz (GHz). The keyfill panels are used to input cryptological keys into the GPS receiver that allow access to highly accurate, precise navigation signals. • • Figure 2-14 — Typical GPS antenna mounting. Inertial Navigation System An INS is a self-contained, electronic, all-altitude navigation system with host aircraft interface. It transmits navigational outputs when requested to the aircraft. The INS detects aircraft motion and provides acceleration, velocity, present position, pitch, roll, and true heading data. In addition, INS uses dead reckoning to provide accurate position navigation. Dead reckoning is the process of estimating present position from known information. A typical inertial navigation unit (INU) is shown in Figure 2-15. Basic Components The INS continuously measures aircraft accelerations to compute aircraft velocity and change in present position. These measurements are made by precision inertial devices mounted on a three2-14 axis stable element, which is part of a four-gimbal structure. The four-gimbal structure allows the stable element to move with 360 degrees of freedom about the three axes. Two gyros provide gimbal stabilization signals to maintain the stable element level with the Earth’s surface and aligned to true north. The system uses these signals to measure aircraft pitch-and-roll attitudes. The inertial characteristics of the gyroscopes used in the system define and maintain the reference axes for relatively long periods with great accuracy. Gyroscopes are mechanical devices that contain a spinning mass (gyro) that is universally mounted (by gimbals) allowing it to assume any position in space. With a gyrostabilized platform as a reference, it is possible to accurately detect components of motion in any direction. To do this, precision accelerometers and analog or digital computers are used in an INS. Figure 2-15 — Typical inertial navigation unit. Accelerometers The primary data source for the INS is the accelerometer. An accelerometer is a device used to produce a voltage proportional to the acceleration input. Three accelerometers are mounted on the stable element between the gyros. They provide output signals proportional to total accelerations experienced along the three axes of the stable element. The system uses these accelerations to produce aircraft velocities and changes in position. By mounting three accelerometers on a stable element, the platform “X” (east and west), “Y” (north and south), and “Z” (up and down) velocities are continually measured. The “X” and “Y” velocities are also resolved into the north and east velocities by using aircraft heading. The combination of these velocities gives the change in latitude and longitude from the last known position. Inertial Corrections In a space-stabilized system, the platform appears to rotate as the Earth turns on its axis. In addition, the platform would not remain level to the vertical as the aircraft moves over the surface of the Earth. To overpower these appearing gyro precessions as the aircraft travels and the Earth rotates, the platform must be torqued so that it remains normal (perpendicular) to the Earth surface. Earth rate converts space-stable INS to a geographical-stable (Earth-oriented) system. Gyro-torquing 2-15 computations are made as a function of time and distance traveled. The gyro-torquing computations (corrections) are described below: • The alpha angle is the angular difference between the platform heading and true north. Alpha angle is used as a gyro-torquing correction factor during alignment and navigation. • Earth rate correction is used to maintain the platform heading alignment and level in order to allow accelerometers to sense aircraft acceleration only. • Schuler loop mechanization is used to prevent the aircraft acceleration from causing an oscillation in the INU platform. Schuler loop correction is used as a gyro-torquing correction factor during navigation. • Centripetal force is a true acceleration sensed by accelerometers because the Earth and its atmosphere are moving with respect to inertial space. Centripetal force correction is made by correcting the difference between centripetal force, aircraft velocity, and position. • The Coriolis force is a false acceleration caused by the Earth rotating around its polar axis as related to inertial space. Coriolis force acceleration correction is required to keep the platform level to the Earth. Alignment The process of INS alignment uses a statistical estimation known as Kalman filtering. The platform outputs and reference data are compared to external reference data inputs. Kalman filtering estimates the errors in the compared data to correct platform heading, velocity, and attitude. • A ground alignment (Figure 2-16) analyzes position data (latitude and longitude) manually entered into the aircraft. o A carrier alignment uses the ship’s inertial navigation system (SINS) to provide the aircraft with reference data (ship’s velocity, position, and attitude). Carrier aircraft receive updated position information from either a SINS cable or an aircraft data link. A Figure 2-16 — Typical ground alignment cockpit display. 2-16 SINS cable can be connected from a deck edge receptacle on the ship to a receptacle on the aircraft to receive updated reference data. • o The aircraft data link uses electronic methods to receive updated reference information from the SINS. An inflight alignment (Figure 2-17) uses inputs and reference data from avionics systems to either preserve an existing alignment or to start a new alignment. During the alignment, air data dead reckoning is used for navigation and for maintaining the current existing position. Figure 2-17 — Typical inflight alignment cockpit display. 2-17 End of Chapter 2 Navigation Review Questions 2-1. What navigational term is defined as one point in space relative to another, without reference to distance? A. B. C. D. 2-2. What navigational term is defined as the spatial separation between two points measured by a line? A. B. C. D. 2-3. 20.25 21.75 22.36 23.34 What geographic location is the official starting point to calculate longitude? A. B. C. D. 2-6. 12 14 16 18 The ellipticity of Earth can be expressed in how many nautical miles? A. B. C. D. 2-5. Position Direction Distance Time How many miles is the approximate distance between the highest and lowest point of the Earth? A. B. C. D. 2-4. Position Direction Distance Time London, England Leeds, England Greenwich, England Wisbech, England One knot is equal to how many statute miles per hour? A. B. C. D. 0.75 1.15 1.25 1.75 2-18 2-7. What true direction is defined as the intended horizontal direction of travel? A. B. C. D. 2-8. What altitude reference plane is the height of the aircraft above the standard datum plane? A. B. C. D. 2-9. Bearing Track Heading Course Pressure Indicated Density Calibrated What type of cell is connected to mechanical linkage inside pressure altimeters? A. B. C. D. Anode Aerate Aneroid Android 2-10. What pressure altimeter error is caused by misalignments in gears and levers? A. B. C. D. Reversal Scale Hysteresis Mechanical 2-11. What pressure altimeter error is caused by inducing false static pressure into the system? A. B. C. D. Reversal Scale Hysteresis Mechanical 2-12. What type of altimeter uses radio frequency pulses to measure aircraft height? A. B. C. D. Static Pressure Absolute Pitot 2-13. What airborne navigation system uses polar coordinate type radio signals? A. B. C. D. Automatic direction finder Tactical Air Navigation Global positioning Inertial navigation 2-19 2-14. What signal, in hertz, does the Tactical Air Navigation system use to obtain bearing information? A. B. C. D. 5 11 15 19 2-15. What segment of the global positioning system consists of satellite monitoring stations? A. B. C. D. Space User Carrier Control 2-16. The global positioning system L1 carrier signal operates in what megahertz frequency? A. B. C. D. 1227.61 1424.82 1575.42 1610.71 2-17. What global positioning system carrier signal operates in the 1227.6 megahertz range? A. B. C. D. L1 L2 L3 L4 2-18. What aircraft characteristic is continually measured by the inertial navigation system? A. B. C. D. Altitude Speed Acceleration Attitude 2-19. What components are the inertial navigation system’s main sources of data? A. B. C. D. Accelerometers Gyros Gimbals Servos 2-20. What mode of inertial alignment is initiated by manually entering positon data? A. B. C. D. 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CHAPTER 3 RADAR Radio detection and ranging (radar) systems are one of the most important offensive and defensive tools used in tactical aircraft. Modern radar systems provide the operator with the enhanced ability to detect, track, and intercept hostile air and surface targets. Organizational aviation electronics technicians (AT) will operate, troubleshoot, and repair complex radar systems. Therefore, a basic understanding of the principles and components of radar systems is important to complete the tasks. This chapter will provide an overview of the basic concepts, principles, and components of a typical radar set. The radar used in the Fighter/Attack (F/A)-18 series, Multi-Mission Helicopter (MH)-60R, and the Patrol (P)-3 Orion platforms will be provided as examples of the systems being used in the fleet. In addition, because they are normally integrated with radar systems, the basic principles and the components used in Identification Friend or Foe (IFF) systems will be described. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Describe the basic operating principles of a radar system. 2. Recognize the basic components used in typical radar systems. 3. Describe the types of typical radar systems. 4. Identify the components of the APG-73 radar system. 5. Describe the operating principles of the APG-73 radar system. 6. Identify the components of the multi-mode radar (MMR) system. 7. Describe the operating principles of the MMR system. 8. Identify the components of the APN-234 color weather radar system. 9. Describe the operating principles of the APN-234 color weather radar system. 10. Identify the components of a typical IFF system. 11. Describe the operating principles of a typical IFF system. 12. Identify the components of the APX-123(V) IFF system. 13. Describe the operating principles of the APX-123(V) IFF system. BASIC RADAR PRINCIPLES AND OPERATION Radar systems operate using a concept that is very similar to hearing an echo reflecting off of a surface (cave, canyon, etc.). The distance and the general direction of the object can be determined because the speed of sound in the air is a known quantity. Radar systems use a similar theory to determine the direction and distance to a target. However, radar systems use radiofrequency (RF) energy instead of sound waves. A typical radar system in operation is shown in Figure 3-1. The following basic radar operating principles will be discussed in this section: • Range • Bearing • Resolution 3-1 • Accuracy Interaction Available Figure 3-1 — Typical radar system in operation. Range A radar system can measure the range (distance) to a target because RF energy travels through space in a straight line at a constant speed (186,000 statute miles or 162,000 nautical miles per second). There are some standard measurements to consider before the range to a target can be determined. The Navy uses nautical miles to measure standard distances. The distance of 1 nautical mile is about 6,080 feet in comparison to 1 statute mile, which is about 5,280 feet. Standard timing in radar systems is expressed in microseconds (µs). Therefore, transmitted RF energy travels at a constant speed of approximately 984 feet per µs. The time that it takes for RF energy to travel 1 nautical mile, using the information above, can be calculated by using the following formula: 𝟔𝟔, 𝟎𝟎𝟎𝟎𝟎𝟎 𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟 = 𝟔𝟔. 𝟏𝟏𝟏𝟏 µ𝐬𝐬 𝟗𝟗𝟗𝟗𝟒𝟒 𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟 𝐩𝐩𝐩𝐩𝐩𝐩 µ𝐬𝐬 Further calculations are required because a radar system determines the range to a target by measuring the elapsed time it takes for the RF energy to travel to a target and return to the transmission medium. This is easily accomplished by using the following formula: 𝟔𝟔. 𝟏𝟏𝟏𝟏 µ𝐬𝐬 × 𝟐𝟐 (𝐑𝐑𝐑𝐑 𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩 𝐨𝐨𝐨𝐨𝐨𝐨 𝐚𝐚𝐚𝐚𝐚𝐚 𝐑𝐑𝐑𝐑 𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩 𝐛𝐛𝐛𝐛𝐛𝐛𝐛𝐛) = 𝟏𝟏𝟏𝟏. 𝟑𝟑𝟑𝟑 µ𝐬𝐬 3-2 The resulting 12.36 µs time interval is known as a radar mile or nautical radar mile. The range to a target can now be calculated by measuring the elapsed time it takes for a radar pulse to travel round trip then dividing it by 12.36 µs. The formula is as follows: 𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑 = 𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄 𝐭𝐭𝐭𝐭𝐭𝐭𝐭𝐭 𝟏𝟏𝟏𝟏. 𝟑𝟑𝟑𝟑 µ𝐬𝐬 𝐩𝐩𝐩𝐩𝐩𝐩 𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦 To further clarify this concept, an example of determining the range to a target is given below: 𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑 = 𝟔𝟔𝟔𝟔 µ𝐬𝐬 = 𝟓𝟓 𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦 𝟏𝟏𝟏𝟏. 𝟑𝟑𝟑𝟑 µ𝐬𝐬 𝐩𝐩𝐩𝐩𝐩𝐩 𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦 Based on the above calculation, the target is approximately 5 nautical miles away from the radar system. Minimum Range The minimum range of a radar system is dependent on timing, pulse width, and recovery time. Minimum range can be calculated using the following formula: 𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 = (𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩 𝐰𝐰𝐰𝐰𝐰𝐰𝐰𝐰𝐰𝐰 + 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 𝐭𝐭𝐢𝐢𝐦𝐦𝐦𝐦) × 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲 Below is an example of using this formula to calculate a radar system’s minimum range: 𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 = (𝟐𝟐𝟐𝟐 + 𝟎𝟎. 𝟏𝟏) × 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲 = 𝟐𝟐𝟐𝟐. 𝟏𝟏 × 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲 = 𝟒𝟒, 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲 (𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚) Maximum Range The maximum range of a radar system is dependent on the signal carrier frequency, peak power of the transmitted pulse, pulse repetition frequency (PRF), and the sensitivity of the receiver. The carried frequency is the actual frequency of the transmitted RF energy. The PRF is the primary limiting factor in determining the maximum range of a radar system. The timing between one pulse and the other is called pulse repetition time (PRT). The PRT is equal to the reciprocal of the PRF: 𝟏𝟏 𝐏𝐏𝐏𝐏𝐏𝐏 There are outside limiting factors that can affect the maximum range of a radar system such as atmospheric conditions. These factors can make it difficult to determine the maximum range of a radar system. However, it is possible to determine the maximum theoretical range of a radar system operating in optimal conditions by using the following formula: 𝐏𝐏𝐏𝐏𝐏𝐏 = Bearing 𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 = 𝟏𝟏𝟏𝟏𝟏𝟏, 𝟎𝟎𝟎𝟎𝟎𝟎 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦/𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬 × 𝐏𝐏𝐏𝐏𝐏𝐏 𝟐𝟐 The term bearing is used to describe the position of a target in relation to the radar system. The bearing to a target can be expressed in two ways: true and relative. True Bearing True bearing (Figure 3-2) is the angle between true north and the line directly pointed at the target. Notice that the angle is measured in the horizontal plane in a clockwise direction from true north. 3-3 Relative Bearing Relative bearing (Figure 3-2) is measured in a clockwise direction using the centerline of the radar antenna as the reference point. Resolution The term resolution refers to the ability of a radar system to distinguish between targets. Resolution in radar systems can be expressed in three ways: target, range, and bearing. Target Resolution Target resolution is defined as the radar system’s ability to distinguish between two targets that are close together in either range or bearing. This characteristic is very important for weapons control radar systems. Figure 3-2 — True and relative bearing. Range Resolution Range resolution is defined as the radar system’s ability to distinguish between two targets that are on the same bearing but at different ranges. Range resolution is dependent on the width of the pulse and the type and size of the target. Bearing Resolution Bearing resolution is the radar system’s ability to distinguish between two targets that are at the same range but at different bearings. Bearing resolution is dependent on the radar system’s beam width and the range of the target. Accuracy Radar accuracy is the ability of the system to determine the correct range, bearing, and, in some cases, altitude of a target. The overall accuracy of radar is dependent on the overall resolution of the system. There are two factors that can directly affect the accuracy of a radar system: pulse shape and atmospheric conditions. Pulse Shape The perfect shape of a radar pulse can be defined as a square wave that has vertical leading and trailing edges. The perfect radar pulse enables the radar to accurately define a target. However, due to limiting factors, most radar systems are unable to consistently produce a perfect pulse shape. Radar systems vary the shape of the pulses to identify targets at short or long ranges For example, radar systems use narrow pulse shapes to identify targets at short ranges. The narrow pulse shape allows the radar to rapidly transmit and receive the RF energy. In comparison, in order to identify targets at longer ranges, the radar system must widen the width of a pulse and modulate the PRF. Atmospheric Conditions The speed of RF energy traveling through space is affected by temperature, pressure, and the amount of water vapor (humidity) in the atmosphere. This effect on RF energy traveling through the atmosphere is called refraction. Refraction is the deflection or change in direction of RF waves as 3-4 they travel through space at different speeds. RF refraction through the atmosphere will affect a radar system’s ability to accurately identify a target at various ranges. Radar System Components A typical radar system requires the following components to operate: • Synchronizer • Transmitter • Duplexer • Antenna • Receiver • Indicator • Power supply The components in many cases are combined in single units. A functional block diagram of a basic radar system is shown in Figure 3-3. Figure 3-3 — Functional block diagram of a basic radar system. Synchronizer A synchronizer (timer) supplies the signals that time the transmitted pulses, the indicator, and other associated circuits. A synchronizer also sets the interval between transmitted pulses to ensure the pulsed RF energy is the proper length. The timing of the RF pulses is directly related to the PRF. 3-5 Transmitter A radar transmitter is a component that generates RF energy in the form of short and powerful pulses. Transmitters use oscillators to turn a low-power RF energy signal into a high-power output signal. Extremely high voltage is used to switch the oscillator on and off, which in turn generates the high-power RF energy pulse. WARNING Radar transmitters are capable of producing high voltages that can be extremely hazardous to personnel. Safety procedures and precautions must always be observed by personnel working on or around radar transmitters. Duplexer The duplexer is an electronic switch that allows a radar system to use the same antenna to alternate between transmitting and receiving RF energy. The switching time is called receiver recovery time. A duplexer must be capable of switching between the two cycles rapidly to improve the detection of short range targets. In addition, duplexers should absorb very little power during transmit and receive cycles. This characteristic is very important because received echoes can be very low amplitude. Antenna Radiated energy has the tendency to spread out equally in all directions. The antenna routes the RF energy from the transmitter and radiates the energy in a highly directional beam. An echo received by the antenna is routed to the receiver for processing. Antenna systems normally include transmission lines, waveguides, and duplexers. Additionally, most airborne radar systems use some form of an array antenna. Array antennas are groups of individual radiating elements arranged horizontally and vertically to form a plane. Receiver A radar receiver amplifies the weak echoes returned by the reflecting object (target) and reproduces the echoes into a video pulse that is routed to an indicator. One of the primary functions of a radar receiver is to convert the frequency of the echo into a lower frequency that is easier to amplify. This function is important because radar frequencies are in very high ranges, which make them difficult to amplify. Indicator A radar system indicator is used to provide the operator with a visual display of the returned echo signals that indicate the bearing, range, and altitude of a target. Most modern aircraft use multipurpose displays to show radar data and to control system functions. Power Supply The power supply provides the regulated voltages and signal routing required for operation of a typical radar system. Methods of Radiofrequency Transmission There are four methods a radar system uses to transmit RF energy to detect and track targets: pulse modulation, frequency modulation, continuous wave, and pulse-doppler. 3-6 Pulse Modulation The pulse modulation method of transmission uses very short and powerful bursts of RF energy (pulses). Additionally, pulse transmissions normally occur in a very short period of time (between 0.1 to about 50 µs). The time duration of the pulse travel time is measured and used to calculate range. What makes pulse modulation unique is that it does not depend on the relative frequency of the returning signal or the motion of a target. Pulse modulated radar systems use one antenna and a duplexer to transmit and receive RF energy. Frequency Modulation The frequency modulation of transmission radiates RF energy whose frequency increases and decreases from a fixed reference frequency. The frequency of the returned signal differs from the radiated signal by the amount of time it takes for that signal to travel to the target and return. This type of modulation is normally used in radar altimeter systems. Continuous Wave The continuous wave (Doppler) method of transmission directs continuously transmitted RF energy at a target. A shift in frequency occurs when the target moves towards and away from the transmitted RF energy. The apparent shift in frequency is known as the Doppler effect. A good example of the Doppler effect in action (Figure 3-4) is the changing pitch of a train whistle as a train moves towards a stationary listener. As the train moves closer to the listener, the whistle tone is higher (increase in frequency). The tone of the whistle decreases (decrease in frequency) as the train moves away from the listener. Therefore, the amount of shift is proportional to the speed of the reflecting target. This characteristic makes the continuous wave transmission method the best way to detect a fast moving target in situations where range resolution is not important. Fire control radar systems use this method to illuminate a target for missile systems. Interaction Available Figure 3-4 — Doppler effect. Pulse-Doppler Pulse radar systems can be used to track targets using the Doppler effect. When a transmitted pulse is received, it is compared to the transmission frequency. If there is a difference in the transmitted and received frequencies (Doppler shift) the target is moving. If the frequencies remain the same, then the target is stationary. 3-7 Methods of Scanning Interaction Available Scanning in a radar system is defined as the systematic movement of a radar beam in a pattern while searching for or tracking a target. The method of scanning is dependent on the purpose of the radar system and the antenna size and design. Some radar systems can use different scanning patterns that depend on the selected mode of operation. There are two methods of scanning: stationary lobe and beam. Stationary-Lobe Scanning Stationary-lobe scanning radar is the simplest type of scanning system (Figure 35). This method of scanning uses a single beam that is stationary in reference to the antenna. The antenna must be mechanically rotated to obtain 360-degree coverage. Figure 3-5 — Typical lobe scanning pattern. Beam Scanning There are two methods that can be used in a beam scanning radar system: mechanical and electronic. • In a mechanically scanning radar system, either the entire antenna can move in the desired scanning pattern, or the energy source can be moved relative to a fixed reflector or vice versa. The most common type of mechanical scanning is used to rotate an antenna to obtain 360degree coverage. • An electronically scanning radar system changes the scanning pattern by electronically switching a multi-element array or by switching between a set of energy sources. Electronic scanning systems are more efficient at changing scan patterns compared to mechanical scanning systems. It is important to note that most modern radar systems use a combination of both mechanical and electronic scanning methods. Types of Radar Systems The following paragraphs will provide a brief overview of the search, tracking, missile guidance, approach, and airborne radar systems. Search Radar A search radar system is designed to scan a volume of space in order to detect any target within that space. A typical search radar system installed onboard a ship is shown in Figure 3-6. Search radar systems are further divided into the following types: surface, air, and height finding. 3-8 • A surface search radar system has two primary purposes. First, surface search radar is used to determine the range and bearing of surface targets or low-flying aircraft. Second, surface search radar systems generate a pattern for all of the objects within line-of-sight distance from the antenna. • An air search radar system is used to detect and determine the position, course, and speed of air targets. There are two types of air search radar systems: two-dimensional (2D) and three-dimensional (3D). o A 2D air search radar system provides the range and bearing of a target. • o A 3D air search radar system provides the range, bearing, and altitude of a target. Figure 3-6 — Typical search radar system. A height finding search radar system is used to provide accurate range, bearing, and altitude of air targets detected by air search radar systems. Tracking Radar A tracking radar system (also called fire control radar) is used to provide continuous positional data on a target. These systems normally use a narrow, circular beam to track a target. Missile Guidance Radar There are three basic types of radar guidance used to guide a missile to a target: beam-rider, homing, and passive. • A beam-rider missile follows a beam of directed continuous wave RF energy to intercept a target. • A homing missile detects the reflected radar energy and uses it to intercept a target. • A passive missile intercepts a target by using the energy radiated by the target. Approach Radar An approach radar system (Figure 3-7) is used to guide aircraft to a safe landing in all weather conditions. There are two types of approach radar systems: carriercontrolled approach (CCA) and ground-controlled approach (GCA). 3-9 Figure 3-7 — Typical approach radar system. • The CCA radar is a highly sophisticated system designed to provide guidance information to an aircraft landing on the flight deck of an aircraft carrier. The CCA radar is more complicated than a GCA because the system must compensate for the movement of the ship. • The GCA radar system is a land-based version of the CCA radar system. Airborne Radar Airborne radar systems are designed to meet the strict weight and space limitations necessary to be installed into aircraft. An airborne radar system uses the same characteristics and performs the same functions as ship and land-based systems. AIRCRAFT RADAR SYSTEMS The following section will provide a basic overview of the APG-73 radar system used in the F/A-18 series aircraft, the MMR system used in the MH-60R Seahawk helicopter, and the APN-234 color weather radar system used in the P-3 Orion. APG-73 Radar System The APG-73 radar system provides the operator with the ability to detect, acquire, and track airborne and surface targets. The APG-73 radar system uses target range, range rate, antenna angles, and antenna rates to formulate weapons delivery solutions. Components The APG-73 radar system consists of the following components: • The radar antenna (Figure 3-8) is an electrically driven, high-gain, low-side lobe, two-axis gimbal assembly that provides RF radiation and reception abilities for radar operation. The antenna is made up of the following components: o The planar array is used to radiate a high power and high gain RF pencil beam or mapping beam depending on the operator-selected mode. o The guard horn assembly is used to suppress received signals by the array. o The null horn assembly is used in the air intercept missile (AIM)-7 Sparrow illumination mode of operation. o The waveguide assembly routes microwave energy between the antenna, transmitter, and radar receiver. o The servo assembly provides the signals to the antenna and commands the positon of the antenna. Figure 3-8 — APG-73 radar antenna. 3-10 • The flood antenna is used as a backup illumination source for the AIM-7 Sparrow illumination mode of operation. • The radar power supply converts aircraft or ground equipment 115-volt alternating current, 400-hertz (Hz) power into direct power for use by the radar system. In addition, the radar power supply provides power rectification, output power control, fault sensing, and fault protection. • The radar receiver is used to process RF energy into a useable signal that is routed to the radar data processor (RDP). The radar receiver converts the received RF energy into an intermediate frequency (IF) signal. • The RDP is a general purpose dual processor digital computer that performs the following functions: radar management control, data processing, and performance monitoring. The RDP is an input and output device that interfaces with the mission computer system. The RDP provides target information, display conditions, and built-in-test commands. The RDP also commands the radar system into the air-to-air and air-to-ground modes of operation. • The radar transmitter is a high-power RF amplifier that houses a three-port waveguide switch to route RF to a dummy load, main antenna, or flood antenna. • The electrical equipment rack (Figure 3-9) provides for the physical support and mounting for the APG-73 radar system. In addition, the electrical equipment rack provides the framework for routing electrical connections, coolant lines, and waveguides. It allows the radar package to be easily extended for maintenance and protects the system from the high temperatures when the gun system is fired. The electrical equipment rack is physically and electrically connected to the aircraft by the pantograph assembly. Controls and Indicators Figure 3-9 — APG-73 electrical equipment rack. The APG-73 radar system uses the following controls and indicators: • The master arm control panel is used to select the air-to-air and air-to-ground modes of operation. • The map gain control panel controls the gain (clarity) of the radar map display. • The left hand vertical control panel contains the brake assembly. The parking brake function of the brake assembly is required to keep the aircraft stable during the radar built-in-test. • The lock/shoot light assembly supplies a head-up display of a radar lock-on condition when the radar is in the air-to-air master mode of operation. The lock light indicates that the radar is 3-11 tracking a target. The shoot light indicates that the launch criterion has been met for air-to-air weapons launch. • The sensor pod control panel assembly (Figure 3-10) houses the following radar system controls: o OFF – removes power from the radar system. o Standby (STBY) – activates all of the radar system components except the transmitter. This selection allows the radar system to warm-up before the application of high voltage or can be used to remove the high voltage being applied to the radar system. Figure 3-10 — Sensor control pod control assembly. o Operate (OPR) – is used to turn all components of the radar system in to an operating condition. o Emergency (EMERG) – allows for the full emergency operation of the radar system when the aircraft is in a weight-off-wheels (airborne) condition. • The right throttle grip provides the operator with the ability to select the radar modes of operation, designate and lock targets, and control antenna elevations. • The left throttle grip contains a switch that is used to cycle targets for the High Speed AntiRadiation Missile (HARM). • The aircraft controller grip assembly can be used to select modes of radar operation. • The two (left and right) digital display indicators (DDIs) provide the operator with interface capabilities and visual radar displays. The left and right DDIs are functionally interchangeable. Modes of Operation The APG-73 radar system uses three main modes of operation: air-to-air (A/A), air-to-ground (A/G), and navigation. • The A/A mode (Figure 3-11) of operation detects, tracks, assesses, and designates airborne targets. A/A mode enables the 3-12 Figure 3-11 — Typical A/A radar display. operator to focus on engaging hostile airborne targets by minimizing the number of switch selections to enable and release A/A weapons. The A/A mode uses the following submodes: o Velocity search – detects A/A targets at long range. o Range while search – provides the operator with all aspect detection of A/A targets. o Track while scan – provides the operator with the ability to detect targets in medium to long ranges and to continue to search for other A/A targets. o Single target track – designates and tracks an individual target until the radar lock is broken. o Automatic acquisition – automatically designates a target within the radar field-of-view. o Manual acquisition – initiates when the operator manually selects a target using the throttle designation switch or cage/uncage switch. o Air combat maneuvering – is an operator-selected mode that uses the following submodes: • Wide acquisition – automatically acquires targets to the left and right of the nose of the aircraft. Vertical acquisition – automatically acquires targets in the vertical plane of the aircraft. Boresight – is used to align the radar antenna to the horizontal plane. Gun acquisition – is activated when the operator selects the aircraft gun system. The A/G mode of operation provides the operator with the ability to map, navigate, detect targets, and track targets. The A/G mode automates many of the weapons delivery tasks normally conducted by the aircrew. The A/G mode of operation is divided into the following submodes: o A/G ranging – automatically initiates when the operator selects A/G weapons or when A/G target data is required. o Real beam ground map – assists in sensor-aided A/G weapons delivery. o Sea surface search – detects surface targets over large bodies of water. An example of the APG-73 sea surface display is shown in Figure 3-12. o Doppler beam sharpened – uses three selected resolution modes to increase the A/G field-of-view. o Ground moving target – provides the operator with the ability to detect moving targets on the surface. 3-13 Figure 3-12 — APG-73 sea surface search display. o Real beam ground map-ground moving target indication – provides the operator with better resolution and detail while detecting surface targets. o Precision velocity update – computes velocity error signals that are used by the inertial navigation system during an in-flight alignment. o Terrain avoidance – commands the radar to search and display detected terrain directly in front of the aircraft. o Fixed target and ground moving target track – both submodes track surface target movements. An example of a ground moving target display is shown in Figure 3-13. • The navigation mode of operation is the default mode of operation when the A/A and A/G modes are not selected by the operator. The operator can easily select the other two main modes of operation while in the navigation mode of operation. Multi-Mode Radar System Figure 3-13 — APG-73 ground moving target display. The MH-60R Seahawk uses a radar system that provides the operator with the ability to track and identify targets, scan surface targets, and use the functions of the IFF system. Components The MMR processing subsystem uses the following components: • The radar receiver-transmitter generates the high-power RF energy required to transmit the required operating mode waveforms. The receiver section collects and interprets RF signals and routes the signal to the RDP for processing. • The RDP performs signal and data processing on all target data received from the radar receiver-transmitter. The RDP provides command signals and interfaces with the helicopter mission computer system. In addition, the RDP processes and generates video signals that are displayed on the appropriate mission displays. • The antenna assembly is located on the underside of the MH-60R helicopter. The antenna radiates X-band RF energy via a waveguide assembly. In addition, the antenna assembly houses the L-band IFF antenna and interrogator receiver-transmitter used to transmit and receive coded RF IFF challenges and replies. • The pedestal assembly rotates the antenna assembly in response to operator inputs. In addition, the pedestal assembly provides the signal interface between the IFF interrogator receiver-transmitter, RDP, antenna assembly, and radar receiver-transmitter. 3-14 Controls and Indicators All aspects of MMR operation are performed via the mission display systems and the functional keypad (Figure 3-14). The interface and signal routing between the MMR and the mission computer system is facilitated by the aircraft data handling unit. Figure 3-14 — MMR control and indicator. Modes of Operation The MMR operates in four general modes: long-and short-range search, surface target imaging, target designate, and navigation. • Long-and short-range search – identifies and tracks targets at both short and long ranges by using radiated RF energy. Long-range search is useful for surveillance operations at distances greater than 100 nautical miles. Short-range search is useful for low-visibility navigation and search and rescue operations. In addition, the MMR, in conjunction with the IFF interrogator, can be used to identify a participating unit or a hostile target. • Surface target imaging – provides the operator with a 2D digitally scanned image of a surface target (ship) in all weather conditions by using synthetic aperture radar. • Target designate – radiates a target to provide data for weapons targeting or to designate a target for another aircraft or ship. • Navigation (mapping) – maps coastlines and other terrain features for operator display to increase positional awareness. 3-15 APN-234 Color Weather Radar System The APN-234 color weather radar system is installed in the P-3 Orion. The system provides the operator with continuous weather information on cloud formation, rainfall rates, thunderstorms, and icing conditions. The purpose of the system is to detect hazardous weather and to identify clear flight corridors. Components The APN-234 color weather radar system consists of the following components: • The receiver-transmitter produces a constant-level microwave pulse (between 200 to 800 Hz) that is routed to the antenna assembly via a waveguide system. The receiver-transmitter converts reflected pulses into range and bearing data. The digital range and bearing is transmitted to the indicator-control for display. • The antenna assembly transmits microwave pulses routed from the receiver-transmitter via a waveguide assembly. The antenna assembly also receives the reflected microwave pulse and routes them to the receiver-transmitter for processing. The antenna assembly is physically made up of a 10-inch flat planar array and drive assembly. • The waveguide assembly is a pressurized component used to conduct microwave energy between the receiver-transmitter and antenna assembly. Controls and Indicators The APN-234 color weather radar uses an indicator-control (Figure 3-15) to provide the interface for control of the system. The indicator-control uses a three-color display (red, yellow, and green) to provide visual display of the area scanned by the antenna assembly. Modes of Operation The APN-234 color weather radar uses four modes of operation: weather, weather alert, map, and search. • Weather – displays areas of high moisture density by measuring the return of reflected microwave energy off of cloud formations. Displayed colors reflect the intensity of the returned microwave energy and are based on the strength of the returned signal. High levels of moisture will return high levels of microwave energy. Figure 3-15 — APN-234 indicator-control. 3-16 • Weather alert – operates the same as the weather mode except special circuits cause red areas to flash, notifying the operator of areas of intense rainfall. • Map – allows the weather radar system to display ground features. Rough terrain and urban areas are displayed in red, open ground is yellow, and rough waters appear as green on the indicator-display. Calm water will not return a signal because it reflects very little energy. • Search – tracks surface objects overwater. Special circuits reduce the amount of noise, which in turn enhances the ability to discern small targets. BASIC IFF SYSTEMS PRINCIPLES A typical IFF system provides a means for identifying friendly aircraft from enemy aircraft. An IFF system permits a friendly aircraft to identify itself automatically by transmitting a reply when challenged by a valid interrogator. In addition, an IFF system can be used to report aircraft and altitude information to air traffic control radar systems, ships, and other aircraft. Typical IFF System Components A typical IFF system is made up of the following components: • The interrogator unit responds to coded pulse signals from a challenger. The challenger can be another aircraft, ship, or ground station. The reply signals are routed to the codersynchronizer unit. • The coder-synchronizer unit in a typical IFF system is synchronized to the radar system so that reception of an IFF response and radar RF signals cannot occur at the same time. • The transponder unit in a typical IFF system receives the challenge signals from an interrogator unit and transmits the properly coded response. • The search radar unit in a typical IFF system initiates the trigger pulse and radar video signals when an unidentified aircraft has been detected by the radar. An example of typical IFF display indications is shown in Figure 316. Figure 3-16 — Example of a typical IFF display. IFF Modes of Operation A typical IFF system uses the following modes of operation: modes 1, 2, 3/A, C, and 4. • Mode 1 – provides the general identification of military aircraft only; has 32 different codes. • Mode 2 – identifies specific military aircraft; has 4,096 different codes. 3-17 • Mode 3/A – is used by both the military and civilian air traffic control to identify aircraft; has 4,096 different codes. • Mode C – provides aircraft altitude information based on the aircraft’s current pressure altimeter reading; has 2,048 different codes. • Mode 4 – is a classified secure mode of operation used only by military aircraft. AIRCRAFT IFF SYSTEMS The following paragraphs will describe the IFF system found in the P-3 Orion aircraft. The P-3 Orion uses the AN/APX-123(V) IFF transponder system. APX-123(V) IFF Transponder System The APX-123(V) IFF transponder system used in the P-3 Orion aircraft receives IFF coded signals and decodes the signal to determine its validity. In addition, the IFF transponder system responds to valid IFF interrogations by using the correct code for the mode and set. Components The APX-123(V) IFF transponder system consists of the following components: • The APX-123(V) IFF and very high frequency (VHF)/ultrahigh frequency (UHF) antennas receive and transmit IFF coded interrogation signals and responses. • The aircraft control display units (CDUs) are used by the pilot, copilot, and the navigation/communication officer to access and operate the functions of the APX-123(V) IFF transponder system. • The APX-123(V) IFF transponder receives the interrogation signals and detects and amplifies the signal. The transponder then analyzes the spacing between the pulse-pairs to determine the proper reply. The pulse-pair can contain one or more of the following codes: o Emergency signal o Identification (IDENT) o Special position indicator (SPI) pulse (mode 3/A) • o Altitude information (mode C) The APX-123(V) IFF transponder incorporates embedded cryptological functions used to interface and control modes 4 and 5. Modes of Operation The APX-123(V) IFF transponder has seven different modes of operation. Modes 1, 2, 3/A, C, and 4 provide the same information as described in the typical IFF system section. Modes S and 5 are described below: • Mode selective interrogation (S) – is a civilian air traffic control capability that reduces the number of unwanted IFF replies. Each aircraft is assigned a unique and permanent mode S address that allows air traffic control to direct interrogations and to send data messages to the desired aircraft. • Mode 5 – is a secured cryptological mode that uses two methods of data transmission, level 1 and level 2. 3-18 The APX-123(V) IFF transponder also has two special and three functional testing modes of operation: identification of position, emergency, power up built-in-test, initiated built-in-test, and periodic built-in-test. • Identification of position (I/P) – is transmitted in modes 1, 2, 3/A, and S to provide the ability for air traffic control to determine the identification between two aircraft. • Emergency mode – is used for emergency replies in all modes of operation except mode C. • The power up built-in-test (PUBIT) – provides the operator with the operational performance status of the IFF transponder system when power is applied via the CDU. • The initiated built-in-test (IBIT) – provides the operator with the operational performance status of the IFF transponder system when the test function is manually selected via the CDU. • The periodic built-in-test (PBIT) – runs automatically during IFF transponder operations and provides the operator with up-to-date operational status indications. A typical APX-123(V) IFF bit status display page is shown in Figure 3-17. Figure 3-17 — Typical APX-123(V) IFF bit status display. 3-19 End of Chapter 3 Radar Review Questions 3-1. At what speed, in statute miles per second, does radiofrequency energy travel? A. B. C. D. 3-2. What term is used to describe the position of a target in relation to a radar system? A. B. C. D. 3-3. Target Range Bearing Relative What term defines a radar system’s ability to determine range, bearing, and altitude? A. B. C. D. 3-6. 3,080 4,080 5,080 6,080 What type of resolution is defined as the radar system’s ability to distinguish between two close objects regardless of distance or bearing? A. B. C. D. 3-5. Accuracy Bearing Range Resolution One nautical mile equals how many total feet? A. B. C. D. 3-4. 166,000 176,000 186,000 196,000 Altitude Accuracy Bearing Resolution What radar system component generates short and powerful radiofrequency pulses? A. B. C. D. Duplexer Antenna Indicator Transmitter 3-20 3-7. What radar system component provides the operator with a visual display of returned radiofrequency echoes? A. B. C. D. 3-8. What method of radiofrequency transmission occurs between 0.1 to about 50 microseconds? A. B. C. D. 3-9. Duplexer Antenna Indicator Transmitter Pulse-doppler Continuous wave Pulse modulation Frequency modulation What is the name of the apparent shift in frequency? A. B. C. D. Doppler Pulse Amplitude Modulate 3-10. What type of search radar system provides range, bearing, and altitude? A. B. C. D. Two-dimensional Three-dimensional Four-dimensional Five-dimensional 3-11. What type of radar system is also known as fire control? A. B. C. D. Search Missile Approach Tracking 3-12. What type of radar system is used to guide aircraft to a safe landing? A. B. C. D. Approach Missile Search Tracking 3-13. What type of missile guidance system detects and uses reflected radar energy? A. B. C. D. Beam Passive Homing Unguided 3-21 3-14. What type of approach control radar is the most complicated? A. B. C. D. Beam Ground Homing Carrier 3-15. What APG-73 antenna assembly is used to route microwave energy to the transmitter and receiver? A. B. C. D. Servo Null horn Waveguide Guard horn 3-16. What APG-73 radar component converts radiofrequency energy into an intermediate frequency signal? A. B. C. D. Receiver Transmitter Power supply Data processor 3-17. What APG-73 radar component is a general purpose computer? A. B. C. D. Receiver Transmitter Power supply Data processor 3-18. What APG-73 radar component is a high-power amplifier with a three-port waveguide switch? A. B. C. D. Receiver Transmitter Power supply Data processor 3-19. What APG-73 antenna is used as a backup Sparrow missile illumination source? A. B. C. D. Null Guard Flood Sentry 3-22 3-20. What APG-73 radar system control panel can be used to select the air-to-air mode of operation? A. B. C. D. Map gain Master arm Left vertical Aircraft controller 3-21. What APG-73 air-to-air search mode of operation can be used to detect targets at long range? A. B. C. D. Wide Range Manual Velocity 3-22. Other than air-to-air and air-to-ground, what is a main APG-73 radar mode of operation? A. B. C. D. Velocity Acquisition Combat Navigation 3-23. What APG-73 radar acquisition mode can be selected using the cage/uncage switch? A. B. C. D. Manual Wide Vertical Automatic 3-24. Other than ground moving target track, what APG-73 radar submode can be used to track surface target movements? A. B. C. D. Floating Ground Fixed Precision 3-25. What frequency band of radiofrequency energy is radiated by the multi-mode radar antenna? A. B. C. D. L K C X 3-26. What section of the multi-mode radar collects and interprets radiofrequency signals? A. B. C. D. Receiver Processor Interrogator Transmitter 3-23 3-27. What multi-mode radar assembly provides all signal interfaces for the system? A. B. C. D. Antenna Pedestal Receiver Processor 3-28. What multi-mode radar component interfaces with the mission computer system? A. B. C. D. Antenna Pedestal Data processor Receiver-transmitter 3-29. The multi-mode radar antenna is located on what side of the MH-60R Seahawk? A. B. C. D. Top Under Port Starboard 3-30. What multi-mode radar mode can be used to map coastlines and other terrain features? A. B. C. D. Navigation Target designate Short-range search Long-range search 3-31. What multi-mode radar mode provides the operator with a two-dimensional scanned image? A. B. C. D. Target designate Long-range search Short-range search Surface target imaging 3-32. What multi-mode radar mode provides weapons data? A. B. C. D. Target designate Long-range search Short-range search Surface target imaging 3-33. What system works in conjunction with multi-mode radar to classify hostile targets? A. B. C. D. Weapon Navigation Communication Identification Friend or Foe 3-24 3-34. How many general modes of operation are used by the multi-mode radar? A. B. C. D. Two Three Four Five 3-35. Which of the following aircraft use the APN-234 radar system? A. B. C. D. P-3 Orion F/A-18 Hornet E-2C Hawkeye MH-60R Seahawk 3-36. What APN-234 component converts reflected pulses into range data? A. B. C. D. Indicator-control Antenna assembly Receiver-transmitter Waveguide assembly 3-37. What component of the APN-234 radar is pressurized? A. B. C. D. Indicator-control Antenna assembly Receiver-transmitter Waveguide assembly 3-38. What is the diameter, in inches, of the APN-234 planar array? A. B. C. D. 5 10 15 20 3-39. What component of the APN-234 radar displays digital range and bearing information? A. B. C. D. Indicator-control Antenna assembly Receiver-transmitter Waveguide assembly 3-40. The APN-234 uses how many colors to display information? A. B. C. D. Two Three Four Five 3-25 3-41. The APN-234 provides the operator with how many modes of operation? A. B. C. D. Two Three Four Five 3-42. Colors displayed by the APN-234 are dependent on what characteristic of the returned energy? A. B. C. D. Intensity Amplitude Frequency Wavelength 3-43. What APN-234 mode uses special circuits to display flashing red areas on the display? A. B. C. D. Map Search Weather Weather alert 3-44. What color are rough terrain and urban areas displayed in the APN-234 search mode? A. B. C. D. Red Green Yellow Orange 3-45. What typical Identification Friend or Foe component is matched to the radar system? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-46. What typical Identification Friend or Foe component initiates the trigger pulse and radar video signals? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-26 3-47. What typical Identification Friend or Foe component responds to the coded signals from the challenger? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-48. What typical Identification Friend or Foe component transmits the proper coded response to a valid interrogation? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-49. Other than aircraft data, what other type of information can be transmitted by typical identification friend or foe systems? A. B. C. D. Range Bearing Altitude Velocity 3-50. What typical Identification Friend or Foe mode uses 32 different codes? A. B. C. D. 1 2 3/A 4 3-51. What typical Identification Friend or Foe mode is used by both military and civilian aircraft? A. B. C. D. 1 2 3/A 4 3-52. Identification Friend of Foe mode C contains what total number of codes? A. B. C. D. 1,048 2,048 3,048 4,048 3-27 3-53. What typical Identification Friend or Foe mode is used for general identification of military aircraft? A. B. C. D. 1 2 3/A 4 3-54. What typical Identification Friend or Foe mode is a secure mode used only by military aircraft? A. B. C. D. 1 2 3/A 4 3-55. Other than very high frequency what other frequency antenna is used by the APX-123(V) system? A. B. C. D. Low High Super high Ultrahigh 3-56. What APX-123(V) component incorporates embedded cryptological functions? A. B. C. D. Antenna Interrogator Transponder Control display 3-57. Identification friend or foe pulse pairs can contain how many codes? A. B. C. D. Three Four Five Six 3-58. How many modes of operation are used by the APX-123(V) system? A. B. C. D. Four Five Six Seven 3-59. What APX-123(V) mode reduces the number of unwanted Identification Friend or Foe replies? A. B. C. D. Q R S T 3-28 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. If you have an idea for improving this manual, or if you find an error, a typographical mistake, or an inaccuracy in CNATT manuals, please write or e-mail us, using this form or a photocopy. 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CHAPTER 4 ANTISUBMARINE WARFARE The detection of enemy submarines is important mission for the Navy. One of the most important tools in detecting enemy submarines is sound navigation ranging (sonar) equipment. As an aviation electronics technician (AT), you will need to understand the principles used in the operation of antisubmarine warfare (ASW) equipment. This chapter will provide an overview of the basic principles of sonar, sonobuoys, and the principles of magnetic anomaly detection (MAD) equipment. Every effort has been made to provide relevant examples of the equipment being used in the fleet. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Identify the factors that affect the behavior of a sound beam in the water. 2. Identify the components of typical sonobuoys. 3. Identify the different types of typical sonobuoys. 4. Recognize the components of a typical sonobuoy receiver. 5. Describe the operating principles of a typical sonobuoy receiver. 6. Describe the operating principles of a typical acoustic processing system. 7. Recognize the components of an airborne sonar system. 8. Describe the operating principles of an airborne sonar system. 9. Describe the operating principles of MAD systems. SONAR PRINCIPLES The term sonar is used to describe equipment that transmits and receives sound energy propagated through water. The operating principles of sonar are similar to that of radio detection and ranging (radar), except the transmission medium is sound waves instead of radiofrequency (RF) waves. Similar to radar, range can be determined in sonar because the speed of a sound wave (echo) and the time it takes to travel out and back are known quantities. Additionally, the bearing (direction) of the sound can be determined by identifying the point the sound echo was reflected. Active and Passive Sonar Sonar equipment is generally categorized as being either active or passive. Active sonar equipment depends on a transmitted sound wave and the return of the echo. In contrast, passive sonar equipment uses the sound generated by the target as the source of the echo. An example of active and passive acoustic sensors is shown in Figure 4-1. Transducers Active sonar equipment requires the use of a component called a transducer. A transducer converts an electrical signal into acoustical energy and vice versa. Transducers are watertight and act in the same manner as a loudspeaker when used to transmit a sound wave and as a microphone when receiving the transmitted echo. A typical transducer uses a diaphragm to create areas of low and high 4-1 pressure underwater. The mechanical action of the diaphragm creates two types of sound waves: rarefaction and compression. • Rarefaction occurs when the transducer diaphragm moves inward which in turn creates a low-pressure wave. • Compression occurs when the transducer diaphragm moves in an outward motion. The outward movement creates a wave of high pressure underwater. The vibration of the diaphragm creates the sound wave pattern Figure 4-1 — Active and passive acoustic sensors. shown in Figure 4-2. The distance between two successive rarefactions or compressions is the wavelength of the sound wave. The frequency of the sound wave can then be determined by counting the number of wavelengths that occur per second. Factors Affecting the Sound Wave The term transmission loss can be used to describe the loss of signal strength as a sound wave travels through the water. There are seven factors that can cause transmission loss: • Absorption and scattering • Reflection • Reverberation • Divergence • Temperature • Refraction • Salinity Figure 4-2 — Transducer sound wave pattern. Absorption and Scattering Sound energy emitted by a source will be absorbed while passing through the water. The amount of energy that will be absorbed can depend on the sea state. When the winds are high enough to produce whitecaps and a concentration of bubbles at the surface level, the absorption level of sound 4-2 energy will be higher. Further, the loss of sound energy is greater in areas of wakes and strong ocean currents, such as riptides. These characteristics can create false echoes and high reverberations that make accurate echo-ranging nearly impossible. It is also important to note that the absorption of sound waves is greater at higher frequencies. Sound waves are weakened when they reach a region of seawater that contains foreign matter, such as seaweed, silt, animal life, or air bubbles. Foreign matter in the water scatters the sound beam and causes the loss of sound energy. The practical result of scattering is the reduction of the echo strength especially at long ranges. Reflection When a sound wave hits an object or a boundary region between transmission mediums it echoes (reflects) back to its origin. The echo will occur in cases where the two mediums are of sufficiently different densities and the sound wave strikes at a large angle. The echo will occur because the sound wave travels at different speeds through the two different densities. The reflection of a sound wave off of a submarine is shown in Figure 4-3. Interaction Available Figure 4-3 — Sound wave reflecting off of a submarine. Sound waves travel about 4 times faster in water than they do in the air. Additionally, the density of water is more than 800 times greater than the density of the air. Therefore, nearly all sound waves will be reflected in a downward direction from the sea surface. When a sound wave strikes the bottom of the ocean it naturally reflects in an upward direction. There will be very little signal loss if the bottom happens to be a smooth, hard surface. Other factors being equal, the transmission loss of a sound wave will be less over a smooth, sandy bottom and greater over soft mud. Over rough and rocky bottoms, the sound is scattered, resulting in strong bottom reverberations. However, it is important to note that a sound wave may never strike the bottom due to extremely deep waters (600 feet or more). The water pressure at extreme depths is so great that a sound wave will actually speed up and bend back towards the surface. In calm seas, most of the sound energy that strikes the water surface from below will be reflected back down into the sea. A scattering effect occurs as the sea gets progressively rougher. In these circumstances, part of any sound striking the surface is lost in the air, and part is reflected in scattering directions in the sea. In water less than 600 feet deep, the sound may also be reflected off the bottom. 4-3 Reverberation Reverberations are multiple reflections of a sound wave. A good example of natural reverberation is the sound of thunder. The discharge of lightning causes a quick, sharp sound but by the time the sound of thunder is heard, it is usually drawn out to a prolonged roar due to the characteristics of reverberation. Reverberations often occur when using sonar systems. Sound waves strike small objects in the water, like fish or air bubbles, which cause the sound waves to scatter. Each of the scattered sound waves produces a small echo that may be returned to a transducer. Echoes are also created by the reflections of sound from the surface and bottom of the sea. The combinations of the echoes from the cumulative disturbances are reverberations. Because the waves are reflected back from different ranges, the combination can become a continuous sound that can become so loud that it interferes with the returning target echo. There are three main types of reverberations of a sound wave. They are as follows: • There is reverberation from the mass of water. The cause of this type of reverberation is not completely known, although fish and other objects contribute to it. • There is reverberation from the surface. The reverberation is most intense immediately after the sonar transmission; it then decreases rapidly. The intensity of the reverberation increases with the change of sea state. • There is reverberation from the bottom. In shallow water, this type of reverberation is the most intense of the three, especially over rocky and rough bottoms. Divergence Sound waves, like light waves, weaken with distance. The farther a target is from a sonar transducer, the weaker the sound waves will be when they reach it. This characteristic is known as spreading or divergence. Temperature Temperature is the most important factor that can affect the speed of a sound wave traveling in sea water. Near sea level, a sound wave will travel at approximately 1,080 feet per second. In seawater, sound waves can travel at approximately 4,700 to 5,300 feet per second. One degree of temperature change can increase the speed of a sound wave by 4 to 8 feet per second. The temperature of the sea can vary greatly from freezing in the polar regions to over 85 degrees Fahrenheit (°F) in the tropical regions. The temperature can vary by more than 30 °F from the surface to a depth of greater than 450 feet. Thermal gradient is a term used to describe the direction and the rate of temperature changes around a particular location. There are two types of temperature gradients: positive and negative. • A positive thermal gradient occurs when the surface temperature is cooler than the layers beneath it. This condition rarely occurs, but when it does it will cause a sound wave to travel in sharp upward angle. • A negative thermal gradient describes the colder temperatures that occur with the increase of depth. A negative thermal gradient will cause a sound wave to be refracted in a downward angle. If the temperature gradient remains the same throughout, then the layer is called isothermal (constant temperature). If the temperature of water is a region of rapidly decreasing temperature then the layer is called a thermocline. 4-4 Under normal conditions the temperature of the sea consists of the following layers: • The surface layer is an isothermal or mixed layer in which the temperature changes slightly with depth. • The layer below the surface consists of a thermocline. • The layer below the thermocline consists of a region of water that slowly decreases in temperature. The temperature layers of the ocean are shown in Figure 4-4. Any change in the above combination will change the path of the sound wave. The change in the path of sound waves due to temperature can be advantageous to a submarine trying to avoid detection. This advantage is especially true if the submarine dives below a thermocline. Refraction A sound beam would travel in a straight line if there were no temperature differences in the water. The straight line of travel will occur because the speed of sound would stay roughly the same at all depths and would become weaker at the same rate. Figure 4-4 — Temperature layers of the ocean. The reality is that the speed of sound is not uniform at all depths. Refraction is a term used to describe the bending of a sound wave caused by the variations of temperature. The path of the sound beam will bend away from areas of higher temperature and towards lower temperatures (Figure 4-5). The characteristics of refraction can significantly lower the detection range of an undersea target. Figure 4-5 — The effect of a positive thermal gradient. 4-5 Salinity The term salinity is used to describe the amount of salt content in seawater. Fresh water has a density of about 62.4 pounds per cubic foot but saltwater weighs approximately 64 pounds per cubic foot. The reason for the difference in the overall weight is the salt in the seawater. Salinity does affect the speed of a sound wave but in a lesser manner than temperature. The higher the salt content of the seawater, the faster the sound wave will travel through it. A good example of an area with high salinity is the mouth of a river that empties into a sea. In most other areas, salinity has such little effect that this characteristic can be ignored. When the surface of the sea is cooler than the layers beneath it, the temperature increases with depth, and the water has a positive thermal gradient. This condition is unusual, but when it does happen, it causes the sound beam to be refracted sharply upwards. If the temperature remains the same throughout the water, the temperature gradient is isothermal (of a constant temperature). The surface layer of water is isothermal, but beneath this layer the temperature decreases with depth. The temperature decrease causes the sound beam to split and bend upward in the isothermal layer and downward below it. Sound wave behavior in isothermal conditions is shown in Figure 4-6. Doppler Effect The Doppler effect plays as big a role in sonar systems as it does in fire control radar systems. The received frequency differs from the transmitted frequency when there is relative motion between a target and a receiver. The number of waves will increase if the target is moving towards the receiver. The effect at the receiver is an apparent decrease in wavelength or an increase in frequency. In contrast, if the target is moving away from the receiver the wavelength will become longer and the frequency will be lower. The amount of change in the wavelength and the frequency is dependent on relative velocity between the target and the receiver. Doppler Effect and Sonar Figure 4-6 — Sound wave behavior in isothermal conditions. There are three basic sounds used by typical sonar equipment. • The actual sound wave or ping generated by the equipment • The reverberations that return from the generated sound wave • The returned echo from the target The ping is not normally heard by the operator because most sonar equipment is designed to block it out, which leaves the operator with the challenge of identifying a returned echo from a target against the received reverberations. This challenge is where the Doppler effect becomes very important. 4-6 A helicopter using a sonar transducer to transmit a 10 kilohertz (kHz) ping is illustrated in Figure 4-7. The object near the target is causing reverberations that are being received at the same transmitted frequency (10 kHz), which is indicative of a stationary object. The transducer is also receiving a sound wave that is being received at a frequency of 10.1 kHz (high Doppler) from the submarine. The increase in the received frequency indicates that the submarine is moving towards the helicopter’s position. The difference in the received frequency when the submarine is moving away from the position of the helicopter is shown in Figure 4-8. The transducer is transmitting a signal at a frequency of 10 kHz. The returning echo being received by the transducer is a frequency of 9.9 kHz (low Doppler). The lower frequency indicates the submarine is moving away from the transmitted sound wave. Figure 4-7 — Submarine moving towards a transducer. In Figure 4-9, the results when a target is either stopped or crossing the sound beam at a right angle are illustrated. Notice that the transmitted and received frequency remains the same at 10 kHz (no Doppler). The operator might believe that they are receiving a reverberation or that the target is not moving. SONOBUOYS The primary mission of the Navy’s ASW forces is the detection, localization, and identification of submarines. One of the most useful tools supporting this mission has been the sonobuoy. Since its development during World War II, the sonobuoy has gone through many changes. The improvements in the design over the years have created large numbers of specialized and reliable sonobuoys. Figure 4-8 — Submarine moving away from a transducer. 4-7 Figure 4-9 — Submarine stationary or at a right angle to a transducer. Description and Components A sonobuoy (Figure 4-10) is a cylindrical metal tube that is about 3 feet long and 5 inches in diameter. A typical sonobuoy can weigh anywhere from 20 to 39 pounds depending on its purpose. They are encased in a plastic cylindrical housing called a sonobuoy launch container. It is important to note that sonobuoys are expendable devices that are never recovered after they are launched from an aircraft. Not recovering the sonobuoys may seem like a waste of assets, but it has proven to be the cheapest and most reliable method to search the ocean. A typical sonobuoy consists of the following components: • Inflation bottles • Float bags • Batteries • RF cabling • Hydrophone • Electronic processors • Antennas Figure 4-10 — Typical sonobuoy. Each type of sonobuoy is designed to meet a very specific set of specifications that are unique to the particular type of sonobuoy. The operational specifications are the same for all the manufacturers. However, there are some differences in the prelaunch selection of life and depth settings of the same 4-8 type of sonobuoy. The storing, handling, and setting of a particular type of sonobuoy can be found in the following publication, Sonobuoy Instruction Manual, NAVAIR-28-SSQ-500-1. External Markings Each sonobuoy has the following information marked on the sonobuoy case: • Nomenclature or type • Serial number • Manufacturer’s code number • RF channel number • Contract lot number • Weight • Prelaunch setting Principles of Operation Many of the tactical sonobuoys are designed to detect underwater sounds, such as submarine noise. The sound waves detected by the sonobuoy are modulated by an oscillator in the RF transmitter portion of the sonobuoy. The output of the transmitter is a frequency modulated (FM) very high frequency (VHF) signal that is transmitted from the antenna. The signal is received by the aircraft, then detected and processed by a sonobuoy receiver. By analyzing the detected sounds, the operator can determine various characteristics of the detected submarine. The use of several sonobuoys operating on different VHF frequencies deployed in a tactical pattern enables the operator to localize, track, and classify a submerged submarine. Frequency Channels Certain sonobuoy designs are equipped with an electronic function select (EFS) system. The EFS system provides each sonobuoy with 99 selectable channels. The EFS also provides each sonobuoy with 50 life and 50 depth setting selections. The operator must reset all three settings any time any one of the three are changed. Sonobuoy type and RF channel number are also stamped on each end of the buoy. Sonobuoys with EFS will not be stamped with the RF channel number marking because the channel will be selected by the operator. Deployment Sonobuoys are dropped by aircraft in area that is thought to contain a submarine. The pattern normally involves dropping three or more buoys in a tactical pattern. A typical sonobuoy launch container is shown in Figure 4-11.The operator will select the best pattern to that will provide the best coverage and increase the chances of identifying or tracking the target. Sonobuoys in a launch container can be deployed from an aircraft using any of the following methods: • Spring • Pneumatic 4-9 Figure 4-11 — Typical sonobuoy launch container. • Free-fall • Cartridge Deployment of a sonobuoy from an aircraft can occur at altitudes approaching 30,000 feet and at speeds of up to 370 knots. A descent-retarding device is required because descent velocities can exceed 120 feet per second. The descent-retarding devices are used to increase the aerodynamic stability and to reduce water-entry shock. The devices used to control the descent of the sonobuoy consist of one of the following: • Parachute • Rotating-blade assembly (rotochute) NOTE Do not mix parachute and rotochute sonobuoys during a tactical deployment because of the different descent characteristics. If the two are intermixed, the spacing of the tactical pattern will be incorrect and submarines might be missed. Water Entry and Activation There are two methods that can activate a sonobuoy, water impact or battery activation. Jettisoning of the bottom plate allows the hydrophone and other internal components to descend to the preselected depth. Upon the release of the parachute or rotochute, the antenna is erected. In some sonobuoys, a seawater-activated battery fires a squib, which deploys a float containing the antenna. A termination mass (drogue) is used to stabilize the hydrophone at the selected depth, while the buoyant sonobuoy section (float) follows the motion of the waves. A section of elastic suspension cable isolates the hydrophone from the wave action on the buoyant section. Most of the sonobuoys in the fleet today are equipped with seawater-activated batteries, which provide the power required for the sonobuoy electronics. Data transmission from the buoys usually begins within 3 minutes after the buoy enters the water. In cold water or water with low salinity, the activation time might be increased. There are some models of sonobuoys that use lithium batteries that are not water activated. Operating Life Sonobuoy transmitters are designed to deactivate at the end of a preselected time. The sonobuoy either uses an electronic RF OFF timer, or the transmitter is deactivated when the buoy is scuttled. Some types of sonobuoys use an RF command to activate a mechanism designed to flood the flotation section with seawater. Other types of sonobuoys deflate the flotation balloon to scuttle the unit. In either case, the unit fills with seawater and sinks. A typical deployed sonobuoy is shown in Figure 4-12. 4-10 Figure 4-12 — Typical deployed sonobuoy. Sonobuoy Classification Sonobuoys are grouped into three categories: passive, active, and special purpose. Examples of the sonobuoys in each category are discussed below. Passive Sonobuoys The passive sonobuoy is a listen-only buoy. An overview of the directional frequency analysis and recording (DIFAR) and the vertical line array directional frequency and recording (VLAD) sonobuoys is provided below. • The DIFAR sonobuoy is an improved passive acoustic sensing system that is programmed prior to deployment using EFS circuitry. The newest versions of DIFAR sonobuoys use a directional or an omnidirectional antenna to detect sound waves. They also incorporate the command function selection (CFS) capability. The CFS allows an operator to turn the system on or off, change modes of operation, adjust depths, and change RF channels. The DIFAR sonobuoy provides a magnetic bearing to a target and can be used for search, detection, and classification operations. When the buoy receives an acoustic signal, the unit will convert the pressure wave into an amplified electronic signal. Additionally, a magnetic reference for each received signal is provided by flux gate compass. This capability lowers the number of DIFAR sonobuoys needed to fix the location of a target. A block diagram of a DIFAR sonobuoy is shown in Figure 4-13. • The VLAD sonobuoy is a passive directional sensor that is used to detect and localize a submerged target. The VLAD deploys a vertical line array that consists of directional or omnidirectional hydrophones. The VLAD sonobuoy can be programmed prior to deployment through the use of EFS circuitry. The VLAD sonobuoy also incorporates CFS capability. What makes the VLAD sonobuoy unique is the ability of the system to detect a target in an area of high ambient noise. Detection is accomplished by using beamforming technology. The beamforming technology gives the unit the ability to search, detect, and classify a target at extended ranges Figure 4-13 — Block diagram of a DIFAR sonobuoy. with minimal expenditure. Active Sonobuoys The active sonobuoy uses a transducer to radiate a sonar pulse that is reflected back from the target. The time interval between the ping (sound pulse) and the echo return to the sonobuoy is measured using the Doppler effect. The time-measurement data is used to calculate both range and speed of a target in relation to sonobuoy. An overview of the directional command activated sonobuoy system (DICASS) is provided below. • The DICASS sonobuoy and the monitoring unit signal processor equipment provides active sonar ranging, bearing, and Doppler information on submerged target. The unit incorporates 4-11 CFS capability and is designed to develop and maintain attack criteria. These sonobuoys are normally deployed in multiple patterns but they were designed to permit a single buoy attack criteria. When an ultrahigh frequency (UHF) command signal is received, the DICASS sonobuoy will emit a continuous wave of frequency modulated ping. The transducer array emits omnidirectional pulses on the horizontal plane and beam formed on the vertical plane. When a signal is received it is amplified and filtered prior to assigning a magnetic bearing reference. The signal is then transmitted to the monitoring platform. This flexibility of the sonobuoy and the signal processor equipment allows for the control of a wide range of environments and target conditions. Special-Purpose Sonobuoys Special purpose sonobuoys are not designed for use in target detection, identification, or localization. An overview of the bathythermograph (BT) sonobuoy is provided below. • The BT sonobuoy is an expendable thermal gradient measurement unit that provides a continuous reading of temperature versus depth. Once the BT buoy enters the water, a thermistor probe descends automatically at a constant 5 feet per second. The BT sonobuoy will provide the operator with updated data exceeding depths of 2,000 feet. The temperature gradient is converted to an electrical signal and is applied to the preset carrier frequency. SONOBUOY RECEIVERS A typical sonobuoy receiver set uses radios to receive, demodulate, and amplify sonobuoy transmissions in the VHF spectrum bands. A typical receiver system relays acoustic data to other units (ships or aircraft) via a datalink system. The acoustic data is also routed to a spectrum analyzer for processing and display onboard the aircraft. It is possible to receive and demodulate signals from sonobuoy units at the same time. The operator can select any of the channels for aural monitoring. A typical sonobuoy receiver system can use anywhere from four to twenty individual receivers. Each of the receivers can operate independently on a channel selected by an operator or a computer. Additionally, the receivers are capable of being tuned to any of the 99 available sonobuoy transmission channels. Analog and digital RF signals received from sonobuoys are applied to the receiver modules where they are tuned and filtered. The signals are then amplified, filtered, and mixed to produce an audio output. The audio output is then routed to a spectrum analyzer and the aircraft data link system. The spectrum analyzer processes the signals which allow the operator to monitor the data. ARR-78(V) Advanced Sonobuoy Communication Link Receiver Set The ARR-78(V) advanced sonobuoy communication link (ASCL) receiver set is installed in the Patrol (P)-3 Orion aircraft. The ASCL consists of the following components: • RF preamplifier • Receiver assembly • Indicator-control unit • RF status panel • On top position indicator (OTPI) control unit 4-12 Radiofrequency Preamplifier The RF preamplifier assembly contains two identical preamplifier modules that are capable of driving two receiver assemblies. Each preamplifier accepts and amplifies FM signals in the VHF bands with signal levels between 0.5 and 100,000 microvolts. Receiver Assembly The receiver assembly consists of the following components: • Receiver chassis assembly • 20 synthesizer receivers • Built-in-test equipment modules • Dual power supplies • Automatic direction finder preamplifier/amplifier/multicoupler • Reference oscillator • Clock generator • Computer interface Each acoustic receiver is identical and is capable of receiving FM or frequency shift key (FSK) modulated RF signals. Additionally, the receivers are capable of producing outputs for audio monitoring, RF monitoring, and OTPI. Indicator-Control Unit The indicator-control unit provides the operator with a centralized control and display of the selected receiver modes. Radiofrequency Status Panel The RF status panel continuously displays the control mode (computer or manual), RF channel assignment, and the intermediate frequency level for the active processing acoustic receiver. On Top Position Indicator Control Unit The OTPI uses the ARC-143 radio control set to the interface with the OTPI receiver. The OTPI system operates in conjunction with the direction finder system to provide sonobuoy bearing in relation to aircraft position (relative bearing). The operator can manually tune the OTPI receiver (Figure 414) to any of the selectable VHF channels. Figure 4-14 — OTPI receiver control. 4-13 ACOUSTIC PROCESSING SYSTEM Acoustic processing systems take the data received from the deployed sonobuoys and extracts and converts the information into a usable format. A typical acoustic processing system processes the received audio in active and passive modes to provide long range search, detection, localization, and identification of targets. The processed signals are converted and sent to displays and recorders for use by the operator. Additionally, a typical acoustic processing system generates audio command tones to control active sonobuoys. UYS-1 Single Advanced Signal Processor System The UYS-1 Single Advanced Signal Processor (SASP) system is installed in the P-3 Orion aircraft. It is important to note that while there are number of versions of the SASP in use they all operate in a similar manner. The SASP consists of the following components: • Spectrum analyzer • Power supply • Control-indicator Spectrum Analyzer The spectrum analyzer is a high-speed processor that extracts acoustic target information from the received signals of active and passive sonobuoys. The spectrum analyzer determines the frequency, amplitude, bearing, Doppler, and range of the acoustic targets. Power Supply The power supply converts 115 volts alternating current (ac) into 120 volts direct current (dc) operating voltages. The dc power is further converted into low level voltages used to operate individual circuits. The power supply has a power interrupt unit installed to protect against the loss of target data during transient power interruptions that can occur during operation. Control-Indicator The control-indicator (Figure 4-15) is used to provide the SASP system with power control options and monitoring. The control-indicator also contains a caution section that will display the appropriate thermal warning when an overheat condition exists in the system. Figure 4-15 — SASP control-indicator. 4-14 AIRBORNE SONAR SYSTEM A typical sonar dipping set is a lightweight, echo ranging systems installed in a helicopter. They are used to detect, track, and classify moving and stationary underwater objects. Additionally, a typical sonar dipping set can provide the capabilities for underwater voice communication, bathythermograph recordings, and echo-ranging. Airborne sonar dipping sets are normally installed in helicopters. A typical sonar dipping set consists of the following components: • Azimuth-range indicator • Sonar receiver • Sonar data computer • Multiplexer • Dome control • Reeling machine • Cable and reel assembly • Sonar transducer Azimuth-Range Indicator The azimuth-range indicator (Figure 4-16) is typically installed at the sensor operator station. It is used to provide a visual representation of target range and bearing information. Typical azimuth-range indicators contain controls that are used to adjust display settings, audio settings, target range thresholds, and initiate operational tests. Figure 4-16 — Typical azimuth-range indicator. Sonar Receiver The sonar receiver generates the transmit signal and receives and processes sonic signals from the transducer for display on the azimuth range indicator. The sonar receiver also provides the audio output for aural monitoring of acoustic signals. Sonar Data Computer The sonar data computer is a programmed array processor that provides operation of the dipping sonar. Additionally, the sonar data computer processes signals received from passive and active sonobuoys. Multiplexer The multiplexer provides the electrical interface between the sonar set units and the sonar transducer. 4-15 Dome Control The dome control provides the operator with the controls for raising and lowering the sonar transducer. Additionally, the dome control provides indicators for monitoring the sonar transducer and reeling machine. Reeling Machine The reeling machine is a hydraulic hoist is used to raise and lower the sonar transducer. A typical reeling machine operates at a pressure of 3,000 pounds per square inch (PSI). Cable and Reel Assembly The cable and reel assembly (Figure 4-17) houses the sonar cable that is normally between 1,500 to 1,600 feet in length. A typical sonar cable uses a jacketed cable with a metal armor braid used as the strength component. Electrical wiring is installed inside the cable assembly and is used to route signals between the transducer and multiplexer. Figure 4-17 — Typical cable and reel assembly. Sonar Transducer The sonar transducer (Figure 4-18) generates and transmits sonar pulsed energy or voice signals under the water. The transducer also acts as a listening device and converts the received sound energy into electrical signals. The transducer is attached to the cable and reel assembly. There is a tail assembly installed on the transducer that provides hydrodynamic stability when being raised and lowered into the water. The sonar transducer is the most important component in a dipping sonar system. Modes of Operation A typical sonar set offers the following modes of operation: • Dipping sonar-active – commands the transducer to actively ping to locate, identify, and track a target. • Dipping sonar-passive – commands the transducer to listen for target sounds. • Sonobuoy-active – interfaces with deployed DICASS sonobuoys to actively locate, identify, and track targets. • Sonobuoy-passive – interfaces with DIFAR and VLAD sonobuoys to locate targets by noise signatures. • Underwater voice communication – uses the sonar transducer to transmit and receive voice signals to and from other similarly equipped units. • Bathythermograph recording – commands the transducer to record the differences in water temperature versus depth. This mode can be used to interface with deployed BT sonobuoys. 4-16 Figure 4-18 — Typical sonar transducer. ASQ-22 Airborne Low Frequency Sonar The Navy currently uses the ASQ-22 Airborne Low Frequency Sonar (ALFS) system (Figure 4-19), which is installed in the Multi-Mission Helicopter (MH)-60R Seahawk helicopter. The ALFS provides longer detection ranges and improved detection capabilities over previous sonar dipping sets. The improvements are provided by the use of lower frequencies, less signal attenuation, longer pulse lengths, and increased transmission power. The system also uses an enhanced modular signal processor for improved sonobuoy processing capabilities. Figure 4-19 — MH-60R Seahawk using the ALFS system. MAGNETIC ANOMALY DETECTION Modern submarines rely on stealth to accomplish their missions while operating in open waters. Operating using stealth can make locating a submarine a difficult endeavor even with the use of enhanced radar, thermal, and acoustics systems. However, nature has provided an advantage. The earth is covered in a magnetic field also known as the geomagnetic field. A MAD system provides another option in detecting a submerged submarine. Detection is accomplished by aircraft using specialized equipment designed to identify a disturbance (anomaly) in the geomagnetic field. Principles of Magnetic Detection Light, radar, and sound energy cannot pass from air into water and return to the air in any degree that is useful in the airborne detection of submarines. However, the magnetic lines of force are able to transition through both mediums nearly undisturbed because the magnetic permeability of water and air are fundamentally the same. The lines of force in the geomagnetic field pass through the surface of the ocean unchanged and undiminished in strength. Therefore, an object under the water can be detected from a position in the air above if the object has magnetic properties that distort the geomagnetic field. A submarine with sufficient ferrous mass and electrical equipment can cause an anomaly in the geomagnetic field. The function of MAD equipment is to detect this anomaly. Magnetic Anomaly The lines comprising the natural geomagnetic field do not always run straight north and south. If the lines of force are traced along a typical 100 mile path they twist at places to the east and west, and assume different angles in the horizontal. The angles of change in the east-west direction are known as variation angles. The angles between the lines of force and the horizontal are known as dip angles and are shown in Figure 4-20. The relationship between the Earth’s surface and the magnetic lines of force, at any given point between the equator and the magnetic poles, is between 0 and 90 degrees. Dip angle was 4-17 determined by drawing an imaginary line tangent to the Earth’s surface and to the point at where the line of force intercepts the surface of the Earth. It is important to note that dip angles are considerably steeper in the extreme northern and southern latitudes than they are near the equator. If the same lines are traced only a short distance (short-trace), for example 300 feet, their natural variation and dip over this distance are almost impossible to measure. However, in the area of a large mass of ferrous material, short-trace and dip can be measured by using a highly sensitive anomaly detector. The angular direction at which the natural lines of magnetic force enter and leave the Earth is shown in Figure 4-21, View A. An area of undisturbed natural magnetic strength is show in Figure 4-21, View B. The submarine is shown distorting the natural magnetic field in Figure 4-21, View C and Figure 4-21, View D. The natural dip angle is also affected, but only very slightly. Figure 4-20 — Dip angles. Figure 4-21 — Simplified comparison of natural field density and a submarine anomaly. 4-18 Submarine Anomaly The maximum range at which a submarine may be detected is a function of both the intensity of its magnetic anomaly and the sensitivity of the detector. A submarine’s magnetic moment (magnetic intensity) (Figure 4-22) determines the intensity of the anomaly. It is dependent mainly on the alignment of the submarine in the geomagnetic field, the latitude at which it is detected, its size, and the degree of its permanent magnetization. Although MAD equipment is designed to be very sensitive, a submarine’s anomaly, even at short distances is normally very weak. The strength of the complex magnetic field varies as the inverse cube of the distance from the anomaly. If the detectable field strength of the anomaly has a given value at a given distance and that distance is doubled, the detectable strength of the anomaly will be one-eighth of its former value. Figure 4-22 — Submarine magnetic moment. Based on the above information, two things are clear. First, MAD equipment must be operated at a very low altitude to have the best chance to detect a submarine. Second, the searching aircraft should fly a predetermined route and follow a clear search pattern. This pattern will ensure that a systematic approach is used to reduce the chance of missing existing anomalies. Anomaly Strength Up to this point, the inferred strength of a submarine anomaly has been exaggerated for purposes of explanation. Its actual value is usually so small that MAD equipment must be capable of detecting a distortion of approximately 1 part in 60,000. It is important to understand that that the direction of alignment of the earth’s magnetic lines of force is rarely changed more than one-half of one degree by a submarine anomaly. A contour map displaying the degree of anomaly caused by a submarine is shown in Figure 4-23, View A. The straight line, which is approximately 800 feet, represents the flight path of an aircraft searching the area. If a submarine was not present in the area the undisturbed magnetic area, due to natural characteristics, would be 60,000 gamma. (The gamma, which is symbolized by the Greek letter, γ, is a measure of magnetic intensity). All the variations in the magnetic field, when the submarine is present, would be above or below the natural intensity. The 60,000γ measurement is displayed in Figure 4-23, View C as the zero reference drawn on the moving paper by the recording device shown in Figure 4-23, View B. Any noise or disturbance in the aircraft or its equipment that could produce a signal on the recorder is classified as a magnetic noise. In an aircraft there are many sources of magnetic fields, such as engines, struts, control cables, equipment, and ordnance. Many of these fields are of sufficient strength to seriously impair the operation of MAD equipment. Some means must be employed to compensate for magnetic noise fields. Magnetic noise sources fall into two major categories: maneuver noises and dc circuit noises. 4-19 Figure 4-23 — Contour map and anomaly indications. Maneuver Noises The magnetic field of the aircraft is changed when an aircraft maneuvers, which causes a change in the total magnetic field at the detecting element. The major frequencies that are generated by aircraft maneuvers are significant enough to be built into bandpass components of MAD equipment. Maneuver noises may be caused by induced magnetic fields, eddy current field, or the permanent field. When the aircraft changes heading it induces a magnetic field that is detected by the magnetometer (detecting head). The change in heading causes the aircraft to present a varying size to the geomagnetic field, and only the portion of the aircraft parallel to the field is available for magnetic induction. Eddy current fields produce maneuver noise because of the electrical current that flow in the skin of the aircraft and structural members. An eddy current flow is caused by the aircraft maneuvers and it generates a magnetic field. If the aircraft maneuvers at a slow rate the effect of the eddy current field in negligible. When an aircraft’s maneuver causes an eddy current flow, a magnetic field is generated. The eddy current field is a function of the rate of the maneuver. If the maneuver is executed slowly, the effect of the eddy current field is negligible. The structural parts of the aircraft exhibit permanent magnetic fields, and, as the aircraft maneuvers, its composite permanent field remains aligned with it. The angular displacement between the permanent field and the detector magnetometer during a maneuver produces a changing magnetic field, which the detector magnetometer is designed to detect. 4-20 Direct Current Circuit Noise The dc circuit noise in an aircraft comes from the standard practice in aircraft design of using a singlewire dc system, with the aircraft skin and structure as the ground return. The resulting current loop from generator to load to generator serves as a large electromagnet that generates a magnetic field similar to a permanent magnetic field. Whenever the dc electrical load of the aircraft is abruptly changed, there is an abrupt change in the magnetic field at the detector. Compensation A magnetic field may be defined in three axial coordinates (longitudinal, lateral, and vertical) regardless of its source, strength, or direction. That is, it must act through all or any of the three possible directions in relation to the magnetometer. Induced fields and eddy current fields for a given type of aircraft are constant. There is little difference between the magnetic fields from one aircraft to another of the same type. Magnetic noise must be compensated to provide a magnetically clean environment so that detection systems are not limited by the magnetic fields generated by an aircraft. The aircraft magnetic field can be expected to remain constant, unless significant structural changes are made, throughout the life of the aircraft. Based on this information, aircraft manufacturers provide compensation for the induced fields and eddy current fields. Eddy current compensation is normally achieved by placing the magnetometer in a relatively magnetically quiet area of the aircraft. In some aircraft, the magnetometer is placed at least 8 feet away from the fuselage of the aircraft. This can be done by placing the magnetometer in a fixed boom (Figure 4-24, View A). In comparison, helicopters use a cable attached to the fuselage to tow a magnetometer as shown in Figure 4-24, View B. Figure 4-24 — Types of magnetometers. Induced magnetic field compensation can be accomplished by using Permalloy strips. The magnetic moment is measured by rotating the aircraft to different compass headings. The polarity and variation of the magnetic moment are noted for each of the compass headings. Permalloy strips are placed near the magnetometer to compensate for the field changes created by the magnetic rotation of the aircraft. Additional compensation is required on the longitudinal axis and is provided by the development of outrigger compensators of Permalloy strips near the detecting element. Permanent field compensation must be done in all three dimensions. Compensation is accomplished by three compensating coils mounted mutually perpendicular to one another (Figure 4-25). The adjustments to the field strength are accomplished by controlling the amount of dc that flows through a particular coil. 4-21 Compensation for the dc magnetic field is achieved through the use of electromagnetic compensating loops. The loops are arranged to provide horizontal, vertical, and longitudinal fields. The loops are adjusted to be equal and opposite to the dc magnetic field caused by the load current. The loops are connected across a variable resistor in a particular load center, and are adjusted to allow electrical current flow that is proportional to the load current for correct compensation. An aircraft may have several sets of compensating loops based on the number of electrical distribution centers. Ground wires are used in newer aircraft to minimize the loop size. The procedure for the adjustment of the dc compensation system makes use of aircraft straight and level flight on the four cardinal headings (north, south, east, and west). For example, the actuation of a cowl flap will cause dc field changes representative of Figure 4-25 — Arrangement of compensating those caused by any nacelle load. When the coils. load is energized, the size and the polarity of the signal are noted, and the compensation control is adjusted. The process is then repeated and the compensation control is re-adjusted. This process continues until the resulting signals from the dc field are minimized. Under ideal conditions, all magnetic fields that act on the magnetometer would be completely counterbalanced. In this state, the effect on the magnetometer is the same as if there were no magnetic fields at all. This state could only exist if the following conditions exist: • The aircraft is flying through a magnetically quiet geographical area. • Electrical and electronic circuits are not turned on or off during compensation. • The proper intensity and direction of dc voltages has been set to flow through the compensation coils, so that all stray fields are balanced. The compensation of MAD equipment is normally performed in flight and at sea to approximate the above conditions. The objective of compensation is to gain a state of total magnetic force balance around the magnetometer. If there are any sudden shifts in one of the balanced forces (the geomagnetic field) it will upset the total balance. This sudden shift will be indicated by MAD recording equipment along with any shift in a balanced magnetic force. Shift in any of the forces other than the geomagnetic field are regarded as noise. 4-22 End of Chapter 4 Antisubmarine Warfare Review Questions 4-1. What term describes equipment that transmits and receives sound energy propagated through water? A. B. C. D. 4-2. What characteristic of a sound can be determined by counting the number of wavelengths that occur per second? A. B. C. D. 4-3. Rip Surface Coastal Longshore How many times faster do sound waves travel through water than through air? A. B. C. D. 4-6. Medium High Very high Ultra high Which of the following ocean currents can contribute to greater sound loss? A. B. C. D. 4-5. Amplitude Polarity Frequency Propagation What type of pressure is created by the outward movement of a transducer diaphragm? A. B. C. D. 4-4. Sonar Radar Sounding Depth testing 2 4 6 8 What total number of factors can cause sound wave transmission loss? A. B. C. D. 3 5 7 9 4-23 4-7. Sound waves will travel in what direction from the surface of the ocean? A. B. C. D. 4-8. Sound will travel at what speed, in feet per second, near sea level? A. B. C. D. 4-9. Up Down Straight Horizontal 1,020 1,040 1,060 1,080 What type of thermal gradient occurs when the surface temperature is cooler than the layers beneath it? A. B. C. D. Positive Negative Neutral Transverse 4-10. What term describes a constant water temperature layer? A. B. C. D. Epipelagic Isothermal Hadalpelagic Thermocline 4-11. Sonar equipment uses what total number of basic sounds? A. B. C. D. One Two Three Four 4-12. What term describes sound waves generated by sonar equipment? A. B. C. D. Pong Ping Beep Ring 4-13. What total length is a typical sonobuoy, in feet? A. B. C. D. 3 5 7 9 4-24 4-14. What typical sonobuoy component modulates the received signals? A. B. C. D. Transmitter Synchronizer Oscillator Modulator 4-15. Electronic function select capable sonobuoys have what total number of selectable channels? A. B. C. D. 66 77 88 99 4-16. What radiofrequency band does a typical sonobuoy use to transmit data? A. B. C. D. High Very high Ultrahigh Super high 4-17. Other than type, what number will be stamped on the end of each non-electronic function select sonobuoy? A. B. C. D. Lot Series Model Channel 4-18. What minimum number of sonobuoys is typically used in a tactical search pattern? A. B. C. D. Two Three Four Five 4-19. What part of the tactical pattern is affected when rotochute and parachute sonobuoys are mixed? A. B. C. D. Speed Depth Spacing Arrangement 4-20. A sonobuoy will start transmitting in what total time, in minutes? A. B. C. D. 1 3 5 7 4-25 4-21. What type of suspension cable isolates the hydrophone from wave action? A. B. C. D. Rigid Elastic Electrical Composite 4-22. Most sonobuoys are equipped with what type of battery? A. B. C. D. Thermal Lithium Seawater Nickel cadmium 4-23. The directional frequency analysis and recording sonobuoy provides what type of bearing? A. B. C. D. Magnetic Visual Radar Relative 4-24. The directional frequency analysis and recording sonobuoy amplifies what type of wave into an electronic signal? A. B. C. D. Modulated Pressure Compressed Sinusoidal 4-25. The vertical line array directional frequency and recording sonobuoy uses what type of technology to detect sounds? A. B. C. D. Array forming Wave forming Terraforming Beamforming 4-26. What type of data does a typical sonobuoy receiver relay to other units? A. B. C. D. Electrical Acoustic Digital Analog 4-26 4-27. The radiofrequency preamplifier in a sonobuoy receiver accepts signals at what maximum number of microvolts? A. B. C. D. 100,000 200,000 300,000 400,000 4-28. Other than frequency modulated, what other frequency signals are sonobuoy receivers capable of receiving? A. B. C. D. Single key Silent key Shift key Sliding key 4-29. What component displays the operating mode of a sonobuoy receiver? A. B. C. D. Receiver assembly Indicator-control unit Radiofrequency preamplifier Radiofrequency status panel 4-30. What component of a sonobuoy receiver consists of a clock generator? A. B. C. D. Receiver assembly Indicator-control unit Radiofrequency preamplifier Radiofrequency status panel 4-31. What component of a sonobuoy receiver accepts frequency modulated signals in the very high frequency bands? A. B. C. D. Receiver assembly Indicator-control unit Radiofrequency preamplifier Radiofrequency status panel 4-32. The single advanced signal processor system power supply converts 115 volts alternating current into what number of volts direct current? A. B. C. D. 105 110 115 120 4-27 4-33. Which type of warning is the single advanced processor signal system control-indicator capable of providing to the operator? A. B. C. D. Electrical Acoustic Thermal Proximity 4-34. A typical sonar dipping set consists of what total number of components? A. B. C. D. Eight Nine Ten Eleven 4-35. What typical sonar dipping set component uses a programmed array processor? A. B. C. D. Multiplexer Sonar receiver Sonar data computer Azimuth-range indicator 4-36. What typical sonar dipping set component provides the audio output for aural acoustic signal monitoring? A. B. C. D. Multiplexer Sonar receiver Sonar data computer Azimuth-range indicator 4-37. What typical sonar dipping set component provides the electrical interface between units and the transducer? A. B. C. D. Multiplexer Sonar receiver Sonar data computer Azimuth-range indicator 4-38. A typical dipping sonar reeling machine operates at how many pounds per square inch? A. B. C. D. 1,000 2,000 3,000 4,000 4-28 4-39. What typical sonar dipping assembly provides for the hydrodynamic stability of the transducer? A. B. C. D. Tail Tether Rein Lead 4-40. What is another term used to describe a disturbance in the magnetic field? A. B. C. D. Variance Anomaly Irregularity Abnormality 4-41. What angles are between the magnetic lines of force and the horizontal? A. B. C. D. Dip Force Variation Magnetic 4-42. Other than the sensitivity of the detector, what characteristic of a magnetic anomaly will affect the maximum detection range? A. B. C. D. Depth Speed Intensity Wavelength 4-43. The difference between the Earth’s surface and the magnetic lines of force at the equator and the magnetic poles is 0 and what maximum number of degrees? A. B. C. D. 40 30 60 90 4-44. At what altitude should magnetic anomaly detection equipment be operated to improve the odds of detecting anomalies? A. B. C. D. Very low Low High Very high 4-29 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. If you have an idea for improving this manual, or if you find an error, a typographical mistake, or an inaccuracy in CNATT manuals, please write or e-mail us, using this form or a photocopy. Be sure to include the exact chapter number, topic, detailed description, and correction, if applicable. 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CHAPTER 5 INDICATORS Indicators are components used to display navigation, attack, and situational information to the operator. However, many of the indicators in modern aircraft do more than to display information. Multipurpose displays can provide the operator with control of other systems and subsystems. This chapter provides an overview of the types of indicators installed in the Patrol (P)-3 Orion and Fighter/Attack (F/A)-18 series aircraft. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Describe the operating principles of a typical aircraft navigation indicator. 2. Describe the operating modes of a typical aircraft head-up display (HUD). 3. Describe the operating principles of typical aircraft tactical displays. AIRCRAFT NAVIGATION INDICATORS The electronic flight display system (EFDS) is installed in the P-3 Orion and provides the operator with the following information: • Aircraft course • Bearing • Heading • Distance Additionally, the EFDS displays aircraft pitch and roll information and the steering commands necessary to fly a designated course. The EFDS also displays indications that assist the operator while using an instrument approach to land the aircraft. All of the indications and symbology for the EFDS are displayed on the electronic horizontal situation indicator (EHSI). Electronic Flight Display System Interfaces The EFDS receives signals from the following systems: • Digital data computer • Navigation simulator • Tactical air navigation (TACAN) set • Multi-mode receiver • Direction finder group • Global positioning system (GPS) • Inertial navigation system (INS) • Low frequency automatic direction finder group 5-1 Digital Data Computer The digital data computer receives signals from the INS and computes command course to assist in tactical maneuvering and to provide drift angle information. Navigation Simulator The navigation simulator (Figure 5-1) allows the EFDS to operate when the aircraft is on the ground by supplying power to relays in the navigation interconnection box. When the relays are engaged, the EFDS will display simulated heading information to the operator. Tactical Air Navigation Set The TACAN set provides the EFDS with the distance and bearing information to a compatible station. Course deviation and tofrom information is computed internally and displayed as symbology on the EHSI. Figure 5-1 — Navigation simulator. Multi-Mode Receiver The multi-mode receiver incorporates signals received for the very high frequency (VHF) omnidirectional radio range (VOR), instrument landing system (ILS), glideslope receiver, and marker beacon systems. The signals collected by the multi-mode receiver are routed to EFDS when the appropriate mode of operation is selected. Direction-Finder Group The direction-finder group consists of the ultrahigh frequency (UHF) direction-finder and the on-top position indicator (OTPI) systems. When one of the systems is selected by the operator, the appropriate symbology is displayed on the EHSI. Global Positioning System The aircraft GPS provides the following data to the EFDS: • Bearing • Latitude • Longitude • Waypoint • Altitude • Distance • Speed 5-2 Inertial Navigation System The INS provides the EFDS with magnetic or true heading signals. Magnetic heading signals are supplied to the EHSI in normal operating modes. When a tactical mode of operation is selected, the aircraft true heading is supplied to and displayed on the EHSI. Low Frequency Automatic Direction Finder Group The low frequency automatic direction finder group routes signals through the navigation interconnection box. The low frequency automatic direction finder signals will be displayed as either a bearing pointer 1 or bearing pointer 2 on the EHSI. Electronic Flight Director System Components The EFDS uses the following components to operate and to display situational information to the operator: • EFDS control • Multifunction display Electronic Flight Director System Control The EFDS control provides the operator with the interface to select and change the operational setting for the EFDS. The EFDS control is illustrated in Figure 5-2. Multifunction Display There are five multifunction displays installed in the P-3 Orion aircraft. Each of the multifunction displays provides the operator with the interfaces to select the following indicator display modes: • EHSI • EHSI map mode • Electronic flight director indicator (EFDI) • Primary flight display Figure 5-2 — EFDS control box. NOTE In addition to the EFDS, the P-3 Orion multifunction display provides the operator with control and display of numerous avionics systems and subsystems installed within the aircraft. 5-3 Figure 5-3 — EHSI symbology. The following numbered items provide an overview of the EHSI (Figure 5-3) and symbology. 1. Pilot heading – is controlled by the heading knob on the pilot EFDS control box. The pilot heading bug is colored magenta. 2. Heading reference – indicates the heading reference used (magnetic or true) when the selected navigation mode is the flight management system, VOR, or TACAN. 3. Track indicator – is colored green and rotates around the compass card to reflect the ground track that is computed by the flight management system. 4. Heading index/readout – indicates the current heading of the aircraft with a digital readout. 5. Bearing pointer 1 – is associated with the bearing source selected on the pilot EFDS control box. The bearing pointer 1 is colored magenta. 6. Copilot heading – is controlled by the heading knob on the copilot EFDS control box. The copilot heading bug is colored cyan. 7. Bearing pointer 2 – is associated with the bearing source selected on the copilot EFDS control box. The bearing pointer 2 is colored cyan. 5-4 8. Wind indicator – uses a modified Beaufort scale to show wind display and direction and is colored green. The wind indicator rotates around the compass card to show the current wind direction. 9. Flight management system navigation source – displays the current source of the navigation solution. 10. Flight management system distance – is displayed regardless of the selected navigation source. The distance resolution is 0.1 mile below 100 miles and 1.0 mile above 100 miles up to 999 miles. 11. Active waypoint identification – displays the active waypoint identifier and is displayed below the flight management distance readout. 12. Course arrow – is a segmented white arrow that represents the desired track and is controlled by an external source. A digital readout of the course arrow position is displayed in 1-degree increments. 13. To-from indicator – is displayed towards the nose or tail of the aircraft. The indicator is a white triangle-shaped symbol and is removed from the display when a localizer frequency is selected by the operator. 14. Course deviation bar – indicates the deviation relative to the course arrow position. The deviation is indicated by the course deviation bar deflecting across a four dot reference scale. 15. Navigation source – indicates the source of the course data. 16. Navigation source submode – displays the submode based on the localizer frequency and back course conditions. 17. Course/Desired track indicator – indicates the current selected navigation source course or desired track. A digital readout of the course arrow position is displayed in 1-degree increments below the course/desired track label. 18. Assigned altitude – is processed and displayed in a digital numeric readout with a resolution of 100-foot increments when manually entered into the navigation system. 19. Compass card – is a full 360-degree compass with north, east, south, and west designating the cardinal points and numerical marks at 30-degree intervals. Fixed cardinal marks are displayed at 45-degree intervals around the perimeter of the compass card. 20. Bearing pointer 1 source – indicates the bearing pointer source selected by the pilot. 21. Bearing pointer 2 source – indicates the bearing pointer source selected by the copilot. 22. Command heading – displays the heading currently set by the heading knob on the EFDS control box. 23. Wind – displays a digital readout of the wind direction and speed data received from the flight management system. 24. Aircraft symbol – is stationary and is displayed in the center of the compass card. 25. Course deviation dots – indicate the course deviation in degrees relative to the course arrow position. 26. TACAN channel – displays the selected TACAN channel. 27. TACAN distance measuring equipment – displays the distance from the current selected station. 5-5 Figure 5-4 — EFDI symbology. The following numbered items provide an overview of the EFDI (Figure 5-4) and symbology. 1. Sky/Ground pitch and attitude display – indicates the aircraft pitch and roll through the relationship of the blue upper half and brown lower half of the display. Roll is a continuous 360degree display and pitch is a 90-degree display. 2. Heading tape – is a white heading readout showing current heading with 15 degrees displayed on each side of the center area of the indicator. 3. Roll attitude index – indicates when a no-roll condition of the aircraft exists. 4. Roll attitude indicator – provides the positon of the moving roll pointer with reference to the bank scale. 5-6 5. Pitch tape – provides the positon of the pitch tape with reference to the nose of the aircraft. 6. Marker beacon annunciation – represents the outer, middle, and inner instrument landing beacons when the discrete signal is detected. 7. Crosshair indicator – is used as a pilot/copilot centering cue during a TACAN/VOR/ILS localizer approach and is green in color. 8. Pitch and roll command bar – moves up and down in 15-degree increments and rotates 45 degrees about the center of the display. The pitch and roll command bars are magenta with shading and black outline. 9. Horizon – displays the aircraft pitch and roll attitude in relation to the horizon. 10. Aircraft symbol – is the reference source for the pitch and roll indicators. 11. Navigation source – indicates the selected navigation source. 12. Navigation source submode annunciations – displays the submode of the selected navigation source. 13. Course/Localizer deviation indicator and scale – is located on the bottom center of the display and consists of a green pointer that moves a maximum of 2.5 dots. The scale consists of two white dots on both sides of a white center index. 14. Rate-of-turn indicator and scale – displays the calculated rate-of-turn based on the rate of change of the aircraft heading. 15. Glideslope deviation indicator and scale – consists of a center horizontal bar and a series of vertical white dots. Each of the dots above and below the center bar represents ¼-degree displacement from the center of the glideslope beam. 16. Glideslope annunciation – displays when the pilot has selected a compatible navigation mode and the signal is valid and reliable. HEAD-UP DISPLAY The F/A-18 series HUD is a primary flight instrument that displays essential flight and essential weapons system information. The HUD projects symbology into the operator field-of-view through the use of a combiner glass assembly. The HUD projects the following information: • Aircraft attitude • Steering cues • Navigation data • Air-to-air data • Air-to-ground data • Weapons data Controls and Indicators The F/A-18 series aircraft HUD uses the following controls and indicators (Figure 5-5): • HUD symbology normal/reject 1/reject 2 (HUD SYM-NORM/REJ 1/REJ 2) switch • HUD SYM-brightness (HUD SYM-BRT) control • HUD SYM DAY/AUTO/NIGHT switch 5-7 • Altitude (ALT) switch • Attitude (ATT) switch • Course (CRS) set switch • Heading (HDG) set switch Figure 5-5 — HUD control switches. Head-Up Display Symbology Normal/Reject 1/Reject 2 Switch The HUD SYM NORM/REJ 1/REJ 2 is a three-position toggle switch. Symbology is provided to the HUD when the switch is in the NORM positon. The REJ 1 and REJ2 positions do the following: • REJ 1 – removes the ground cue, aircraft Mach number, airspeed box, altitude box, aircraft G label and digits, and bank scale and bank scale indicator from the HUD field-of-view. • REJ 2 – removes all of the REJ 1 symbology and the heading scale, command heading, heading box, heading caret, navigation range, bank angle scale, bank angle pointer, and time window from the HUD field-of-view. Head-Up Display Symbology Brightness Control The HUD SYM-BRT control is used to turn the HUD to the on position. The HUD SYM-BRT control also allows the operator to vary the intensity of the display to the ambient light. Head-Up Display Symbology Day/Auto/Night Switch The HUD SYM DAY/AUTO/NIGHT is a three-position toggle switch. When the switch is set to the DAY position, the HUD control setting is set to the maximum symbol brightness. When the switch is set to the AUTO position, the HUD contrast is controlled by the brightness control circuit. When the switch is set to the NIGHT position, the HUD symbology is set to a reduced brightness level. Altitude Switch The ALT switch has two positions: barometric (BARO) and radio detection and ranging (radar) with the position being labeled as RDR. When the switch is set to the BARO position, the aircraft displays the computed barometric altitude on the HUD. When the switch is set to the RDR position, the aircraft displays the radar altitude that is computed by the electronic altimeter set on the HUD. Attitude Switch The ATT switch has three positions: INS, automatic (AUTO), and standby (STBY). Each setting designates a different primary data source to compute attitude. In the INS position, unfiltered INS data is used; in the AUTO position, filtered INS data is used; and in the STBY position, the aircraft attitude reference indicator is used. 5-8 Course Set Switch The CRS set switch is used by the operator to manually set the aircraft course that will displayed on the HUD. Heading Set Switch The HDG set switch is used by the operator to manually set the aircraft heading that will be displayed on the HUD. Modes of Operation The F/A-18 series aircraft uses three master mode of operation: navigation, air-to-air, and air-toground. Navigation Master Mode The navigation master mode is the default mode of operation for the F/A-18 aircraft. When the navigation master mode is selected, it provides the operator with basic flight data, steering/landing data, and advisory data displayed on the HUD. The optical center of the HUD is placed, in height, between the Mach number and the aircraft gravitational forces (G) value. The following numbered items provide an overview of the navigation master mode (Figure 5-6) and symbology. Figure 5-6 — Navigation master mode HUD symbology. 1. Heading scale – displays either the magnetic or true heading through the use of a movable 30degree heading scale. 5-9 2. True heading reference – When true heading is selected, a “T” is displayed below the heading scale. 3. Vertical velocity – displays the aircraft vertical velocity, in feet per minute, above the attitude navigation box when the navigation master mode is selected by the operator. The descent of the aircraft is displayed in negative numbers. 4. Altitude – is displayed on the right-hand side of the HUD. The displayed altitude can be either the barometric or radar altitude. 5. Barometric setting – displays the barometric setting used by the aircraft air data computer. The barometric setting display is available in all master modes of operation. 6. Closing velocity – is displayed, in knots, on the HUD when a valid closing velocity exists. 7. Range window – displays the target range when it is available. 8. Ghost velocity vector – is displayed when the velocity vector is caged on the right-hand side of the HUD. 9. Flight path pitch ladder – displays the aircraft position referenced to the velocity vector to provide both pitch and flight path information. 10. Bank scale – is displayed at the bottom of the HUD with tick marks at 5 degrees, 15 degrees, 30 degrees, and 45 degrees. The bank angle scale is not displayed in the air-to-air and air-toground master modes. 11. Peak aircraft G’s – are displayed anytime the aircraft exceeds 4.0 G’s. 12. Aircraft G’s – display the normal acceleration of the aircraft below the Mach number indicator. 13. Mach number – displays the aircraft Mach immediately below the digital angle of attack indicator. 14. Angle of attack – the true angle of attack is displayed at the left center of the HUD in degrees. 15. Required ground speed cue – is displayed when sequential steering and time on target has been selected by the operator. If a pointer is displayed to the right of the reference mark, the aircraft is flying too fast. If a pointer is displayed to the left of the reference mark, the aircraft is flying too slow. 16. Air speed – displays the calibrated air speed that is calculated by the air data computer. Air-to-Air Master Mode The air-to-air master mode is highly automated to reduce the amount of operator tasks in selecting air-to-air weapons, managing sensors, and selecting attack modes. The air-to-air master mode is optimized for the effective beyond-visual-range, head-down attack capability. The air-to-air mode additionally provides for the short-range attack capability using the aircraft guns, and short- to medium-range missiles. The automatic features of the air-to-air mode allow the operator to concentrate on the primary requirement of air-to-air combat. If the air-to-air mode is deselected by the operator, the aircraft will default to the navigation master mode of operation. The following numbered items provide an overview of the air-to-air master mode (Figure 5-7) and symbology. 1. Target locator line – assists the operator in quickly locating a target designation box or a designation diamond. 2. Shoot cue – indicates that the selected weapon has acquired an acceptable firing solution. 5-10 Figure 5-7 — Air-to-air master mode HUD symbology. 3. Multiple target cue – indicates that multiple targets exist in the target designation box line-ofsight window. 4. Target designator – is a 25-milliradian square that identifies the line-of-sight to the selected target. The target designator is displayed for all air-to-air weapons modes. 5. Sensor – indicates the selected sensor being employed for air-to-air weapons launch and steering data. 6. Target aspect cue – provides a head-up indication of the launch and steering target aspect angle. 7. Target range rate – indicates the target range in knots whenever the target data is valid. 8. Target range – is displayed only for air-to-air missiles whenever the target data is valid. The target range is displayed to the nearest 10th of a nautical mile. 9. Selected weapon/count – is used to display the selected weapon and the quantity installed on the aircraft. 10. Master arm cue – displays an “X” through the selected weapon when the aircraft master arm switch is placed in the safe position. 11. Alternate line-of-sight – displays a small “x” that represents a second designated target’s lineof-sight. 5-11 12. Breakaway “X” – indicates to the operator when to break off the engagement or to alter the attack position to achieve a positive weapons delivery solution. The breakaway “X” is displayed for all air-to-air weapons when the range to the target is less than the minimum computed range for the selected weapon. 13. Steering dot – is displayed on the HUD whenever an air-to-air missile is selected and a target has been designated and is located within 76 degrees of the aircraft boresight. Air-to-Ground Master Mode The air-to-ground master mode is used for delivering conventional and laser-guided bombs, GPS weapons, mines, guided weapons, and rockets. Weapons delivery is assured through the use of backup features and redundant fail-safe systems. The focal point for air-to-ground weapons delivery is the aircraft stores management system. The aircraft mission computer and the stores management system control the air-to-ground weapons delivery and weapons programming while providing vital advisory data and cueing to assist in an attack. The following numbered items provide an overview of the air-to-ground master mode (Figure 5-8) and symbology. 1. Steering pointer – is displayed on the HUD heading scale when the air-to-ground mode is activated by the operator. The pointer provides a visual steering cue to a selected waypoint or offset aim point. When a target is designated, the steering cue is replaced by a diamond that indicates the designation status. Figure 5-8 — Air-to-ground master mode HUD symbology. 5-12 2. Pull-up cue – is displayed on the HUD when the selected air-to-ground weapon is a mine, conventional bomb, or rocket. The distance between the velocity vector and the pull-up cue provides the operator with a relative indication of ground avoidance or the dud altitude. 3. Breakaway “X” – is displayed when the pull-up cue intersects with the velocity vector. When this condition occurs, the breakaway “X” flashes on the HUD. 4. Delta (Δ) time-of-fall cue – is displayed when the weapons time-of-fall exceeds 128 seconds. The Δ time-of-fall cue indicates that the mission computer is unable to accurately determine the impact point of the weapon. 5. Dud cue – is displayed when the bomb time-of-fall is less than the dud time for the fuze code that is entered into the stores management system with the stores fuze option selected. The dud cue is also displayed when any of the aircraft fuzing options are not selected. 6. Navigation designation range – is displayed when a steering mode or offset aim point is selected by the operator. The navigation designation range is displayed to the nearest 10th of a nautical mile. 7. Continuously computed impact point – indicates the impact point of the selected weapon if the weapon release was immediately pressed by the operator. If the current weapon impact point is not in the HUD field-of-view, the continuously computed impact point will not be displayed. 8. Displayed impact line (continuously computed impact point) – provides the operator with a steering cue to position the continuously computed impact point cross onto the selected target. AIRCRAFT TACTICAL DISPLAYS The F/A-18 series of aircraft multipurpose display group (MDG) displays all the information required by the operator to carry out the mission. Maintenance technicians also use the MDG to view the status of various aircraft systems and to troubleshoot and isolate system discrepancies. Multipurpose Display Group The MDG (Figure 5-9) system provides the displays for the following aircraft functions: • Aircraft attitude • Navigation • Air-to-air • Air-to-ground • Warnings, cautions, and advisories • Aircraft checklists • Built-in tests The MDG receives digital data signals from the mission computer system and the radar system. The digital data is used by the MDG system to produce the symbology and indications required for the selected display. The MDG system also receives the composite video from the aircraft radar system. Video is provided from the armament computer to the MDG to display forwardlooking infrared (FLIR) and compatible weapons video. 5-13 Figure 5-9 — Typical multipurpose display group. The MDG provides the required digital or analog interface with the following systems: • Mission computer • Radar • Stores management • Flight incident recording and monitoring • Video recording The physical components used by the MDG to display information are as follows: • Left digital data indicator (LDDI) • Right DDI (RDDI) • Multipurpose color display (MPCD) • HUD Digital Data Indicators The purpose of both digital data indicators (DDIs) is to display color alphanumeric symbology, a variety of raster video inputs, deflection voltages, raster/stroke video, and digital serial data to other displays. The DDIs contain circuits that generate calligraphic stroke letters, numbers, and symbols on the display area. The DDIs receive command signals from the aircraft mission computer system via a dual avionics multiplex bus. The DDIs also contain one channel that is used to display radar digital data, which is under the control of the mission computer system. An interface is provided for discrete and analog inputs and outputs. A composite video switch matrix accepts up to five external video inputs and one internal test video input. Left Digital Data Indicator When the LDDI is operating in normal mode, it provides the operator with the following displays: • Stores status • Weapon video • Built-in test status • Aircraft engine monitoring • Cautions and advisories The LDDI also can reproduce aircraft navigation information through an interface with the mission computer system. The LDDI is also the main component to generate symbology for the HUD. The LDDI and RDDI are physically and electrically identical; therefore, they are interchangeable. Right Digital Data Indicator When the RDDI is operating in normal mode, it provides the operator with radar and weapons video displays. The RDDI is also capable of displaying the operator-requested information and provides the interface between the HUD and the mission computer system. If the LDDI fails for any reason, the RDDI is able to produce the symbology for the HUD. However, the RDDI will operate in a degraded mode. A typical DDI is illustrated in Figure 5-10. 5-14 Figure 5-10 — Typical digital data indicator. Multipurpose Color Display When the MPCD is operating in normal mode, it provides the operator with steering and navigation displays. The MPCD is also the main interface for the digital map system. The digital map system provides the operator with a colored map overlay that displays the aircraft’s current position based on the data received from the INS. Head-Up Display The HUD is the primary flight instrument that displays essential flight and tactical systems information. 5-15 End of Chapter 5 Indicators Review Questions 5-1. What electronic flight display system interface allows the system to operate with the aircraft on the ground? A. B. C. D. 5-2. What electronic flight display system interface provides the bearing and distance to a compatible station? A. B. C. D. 5-3. Four Five Six Seven What color is the electronic horizontal situation indicator copilot heading symbol? A. B. C. D. 5-6. Navigation simulator Digital data computer Tactical air navigation set Multi-mode receiver How many multifunction displays are installed in the P-3 Orion aircraft? A. B. C. D. 5-5. Navigation simulator Digital data computer Tactical air navigation set Multi-mode receiver What electronic flight display system interface incorporates the signals from various navigation systems? A. B. C. D. 5-4. Navigation simulator Digital data computer Tactical air navigation set Multi-mode receiver Red Green Cyan Magenta What color is the electronic horizontal situation indicator pilot heading symbol? A. B. C. D. Red Green Cyan Magenta 5-16 5-7. The electronic horizontal situation indicator assigned altitude is a numeric readout with a resolution in increments of how many feet? A. B. C. D. 5-8. The electronic flight director roll attitude indicator provides the position of the roll pointer in reference to what scale? A. B. C. D. 5-9. 100 150 200 250 Pitch Attitude Horizon Bank The head-up display control panel symbology switches both have how many selectable positions? A. B. C. D. Two Three Four Five 5-10. What type of glass makes up the head-up display? A. B. C. D. Acrylic Ballistic Combiner Tempered 5-11. Other than barometric, what is the other head-up display altitude switch position? A. B. C. D. Radar Pressure Indicated Atmospheric 5-12. The head-up display attitude switch has what number of positions? A. B. C. D. Two Three Four Five 5-17 5-13. What head-up display mode of operation displays basic flight data? A. B. C. D. Steering Air-to-air Navigation Air-to-ground 5-14. What head-up display mode of operation is optimized for beyond-visual-range target engagement? A. B. C. D. Steering Air-to-air Navigation Air-to-ground 5-15. What symbol is shown on the head-up display when an acceptable weapons solution has been acquired? A. B. C. D. Shoot cue Target range cue Target designator Multiple target cue 5-16. The delta time-of-fall cue is displayed on the head-up display when the weapon time-of-fall exceeds how many seconds? A. B. C. D. 108 118 128 138 5-17. What system is the focal point for air-to-ground weapons delivery? A. B. C. D. Radar Navigation Communication Stores management 5-18. The digital data indicator contains circuits that generate what type of letters? A. B. C. D. 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CHAPTER 6 INFRARED The term infrared (IR) is a Latin word that means beyond the red. The process of detecting or sensing IR radiation from a target without being in physical contact with that target is known as remote sensing. Active and passive systems are both used for remote sensing. Active systems send a signal to the target and receive a return signal. A radar set is an example of an active system because it requires a return signal to process target data. Passive systems detect a signal or disturbance originating at the target. The signal may be emitted by either the target or another source. Photography using natural light is an example of a passive system. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Recognize the functions of IR imaging. 2. Identify the characteristics of IR imaging. 3. Recognize the components of IR imaging. 4. Describe the operating principles of IR imaging. 5. Recognize the components of a typical Forward Looking Infrared (FLIR) system. 6. Describe the operating principles of a typical FLIR system. ELECTROMAGNETIC SPECTRUM Humans can see only a small part of the entire electromagnetic spectrum. However, there are other parts of the spectrum that contain useful information. The IR band exists in a small portion of the electromagnetic spectrum, and IR radiation is a form of electromagnetic energy. IR waves have certain characteristics similar to those of light and radio frequency waves. These characteristics include reflection, refraction, absorption, and speed of transmission. IR waves differ from light, radio frequency, and other electromagnetic waves only in wavelengths and frequency of oscillation. The IR frequency range is from about 300 gigahertz (GHz) to 400 terahertz (THz). Its place in the electromagnetic spectrum (Figure 6-1) is between visible light and the microwave region used for high-definition radar. The IR region of the electromagnetic spectrum lies between wavelengths of 0.72 and 1,000 micrometers (µm) Discussion of the IR region is usually in terms of wavelength rather than frequency. Figure 6-1 — Electromagnetic spectrum. 6-1 THERMAL IMAGING IR radiation is also known as thermal or heat radiation. Most materials emit, absorb, and/or reflect radiation in the IR region of the electromagnetic spectrum. For example, an aircraft parked on a sunlit runway absorbs and radiates varying amounts of IR radiation. After the sun sets, the aircraft continues to radiate the absorbed heat, making detection at night possible. Even if the aircraft is moved, detection is possible because the runway surface, which was directly below the aircraft, will be cooler than the surrounding runway. Thermal imaging is referenced in terms of temperature instead of reflectivity (radar) or color (visible light). Variations of the temperature in a scene tend to correspond to details that can be visually detected. The IR imaging system processes this information and converts it into information that the system operator can use. Currently, the types of imaging systems generally used are mechanical scanning, fast-framing devices. They use a frame rate (information update rate) that is similar to television. These devices are commonly known as Forward Looking Infrared (FLIR) systems. Before a target can be detected, it must exchange energy with its environment, be self-heating, have emissivity differences, and reflect other sources. The FLIR system uses thermal sensitivity, image sharpness, spectral response, contrast, and magnification to produce a visual image of the thermal scene. The operator of the system uses training, experience, and image interpretation skills to detect and identify targets. INFRARED RADIATION The atmosphere is a poor transmitter of IR radiation because of the absorption properties of carbon dioxide (CO2), water (H2O), and ozone (O3). IR radiation is grouped into four regions by wavelength, as shown in Table 6-1. The transmission spectrum of the atmosphere is shown in Figure 6-2. The best transmission areas for IR radiation are between 3 and 5 µm, and between 8 and 14 µm. The range between these wavelengths is known as a window. IR imaging devices are designed to operate in one of these two windows, usually the 8 to 14 µm window. Table 6-1 — Characteristics of IR Radiation NAME ACRONYM WAVELENGTH Near Infrared NIR Middle Infrared MIR Far Infrared FIR 0.72 – 3 µm Extreme Infrared XIR Infrared Radiation Sources 3 – 6 µm 6 – 15 µm 15 – 1000 µm All matter whose temperature is above absolute zero (-273 degrees Celsius (°C) or -460 degrees Fahrenheit (°F)) emits IR radiation. The amount of the radiation emitted is a function of heat. The emissivity of various objects is measured on a scale of 0 to 1. Theoretically, a perfect emitter is a black body with an emissivity of 1. Realistically, the best emissivity is somewhere closer to 0.98. The total energy emitted by an object at all wavelengths is directly dependent upon its temperature. If the temperature of a body is increased 10 times, the IR radiation emitted by the body is increased 10,000 times. If the energy emitted by a black body and its wavelength is plotted on a graph, a hill-shaped curve results (Figure 6-3). The graph shows that the energy emitted by short wavelengths is low. As the wavelength size increases, the amount of energy increases until it reaches a peak amount. After the peak is reached, the energy emitted by the body drops off sharply with a further increase in wavelength. 6-2 Figure 6-2 — Transmission spectrum of the atmosphere. Infrared Optics Many of the materials commonly used in visible light optics are opaque at IR frequencies. Therefore, these materials would not be suitable for IR imaging systems. The optical material used in IR imaging systems should have a majority of the following qualities: • Be transparent at the wavelengths on which the system is operating • Be opaque to other wavelengths • Have a zero coefficient of thermal expansion to prevent deformation and stress problems in optical components • Have high surface hardness to prevent scratching the optical surfaces • Have high mechanical strength to allow the use of thin lenses (high-ratio diameter to thickness) • Have low volubility with water to prevent damage to optical components by atmospheric moisture • Be compatible with antireflection coatings to prevent separation of the coating from the optical component Figure 6-3 — Black body radiation. 6-3 None of the materials currently used for IR optics have all of these qualities. However, silicon, germanium, zinc selenide, and zinc sulfide have many of them. Infrared Detectors The detector is the most important component of the IR imaging system. There are many types of detectors, each having a distinct set of operating characteristics. Bolometers, Golay cells, mercurydoped germanium, lead sulfide, and phototubes are the most commonly used types of detectors. Detectors can be characterized by their optical configuration or by the energy-matter interaction process. There are two types of optical configurations: elemental and imaging. Elemental Detectors Elemental detectors average the portion of the image of the outside scene falling on the detector into a single signal. To detect the existence of a signal in the field-of-view (FOV), the detector builds up the picture by sequentially scanning the scene. Therefore, the elemental detector requires time to develop the image because the entire scene must be scanned. Imaging Detectors Imaging detectors yield the image directly. Each of the detectors responds to a discrete point on the image. Therefore, the imaging detector produces the entire image instantaneously. A good example of an imaging detector is photographic film. Energy-Matter Interaction There are two basic types of energy-matter interaction. They are the thermal effect and the photon effect. Thermal Effect The thermal effect type of energy-matter interaction involves the absorption of radiant energy in the detector. Absorption results in a temperature increase in the detector element. Radiation is detected by monitoring the temperature increase in the detector. Both the elemental and imaging forms of detectors use the thermal effect. Photon Effect In the photon effect type of energy-matter interaction, the photons of the radiant energy interact directly with the electrons in the detector material. Usually, detectors using the photon effect are made out of semiconductor materials. There are three specific types of photon effect detection. They are photoconductivity, photoelectric, and photo-emissive. • Photoconductivity is the most widely used photon effect. Radiant energy changes the electrical conductivity of the detector material. An electrical circuit is used to measure the change in the conductivity. • In the photoelectric effect (also referred to as photovoltaic), an electric potential difference across a semiconductor P material and N material (PN) junction is caused by the radiant signal. The photocurrent (current generated by light) is added to the dark current (current that flows with no radiant input). The total current is proportional to the amount of light that falls on the detector. • The photo-emissive effect is also known as the external photo effect. The action of the radiation causes the emission of an electron from the surface of the photocathode to the 6-4 surrounding space. The electron is photo-excited from the Fermi level above the potential barrier at the surface of the metal. Infrared Imaging Systems An IR imaging system has the following components: detectors, a scene dissection system, front end optics, a refrigeration system, and an image processing system. Detectors Detectors convert the IR radiation signal into an electrical signal that is processed into information used by the operator. Detectors can be arranged in many different configurations for their use in an IR imaging system. Detector Array Only a small portion of the image scene is needed by a detector (or detectors) to achieve maximum resolution. A large number of detector elements can be grouped together to form an array (Figure 6-4, View A). The elements of this array are packed closely together in a regular pattern. Therefore, the image of the scene is spread across the array like a picture or a mosaic. Each detector element views a small portion of the total scene. The disadvantage of this type of system is that each detector element requires a supporting electronic circuit to process the information that it provides. In addition, each detector element requires a preamplifier to boost the signal to a usable level. Single Detector Another method that is used to provide the operator with information is the single detector (Figure 6-4, View B). Here, there is one detector requiring one set of supporting circuitry. In this type of system, the detector is scanned across the image so that the detector can see the whole image. An optical system is required that can supply the scanning. This type of system is adequate if real-time information is not needed, or if the object of interest is stationary or not moving quickly. Scene Dissection System The scene dissection system is used to scan the scene image. Many types of scanning mechanisms are associated with each type of detector array. When a single detector with one axis of fast scan and one axis of slow scan is used, the scene is scanned rapidly in the horizontal direction and slowly in the vertical direction. As a result, the line is scanned horizontally; then the next line is scanned horizontally, and so on. A vertical linear array is scanned rapidly in the horizontal direction (Figure 6-4, View C). One detector element scans one line of the 6-5 Figure 6-4 — Detector arrays. image. In the linear array, there is a space, one element wide, between each element. The scan pattern is one axis with an interlace. A vertical linear array is scanned rapidly in the horizontal direction. After each horizontal scan, the mechanism shifts the image upward or downward one detector element width so that on the next scan, the lines that were missed are covered. Each system has an optimum configuration of detector array and image dissection. If the number of elements in the detector increases, the system becomes more complicated. In addition, the cost of the system increases, while the reliability of the system decreases. If the number of detectors decreases, the amount of information that can be processed is reduced. A compromise between a large number of elements (increased cost) and a smaller number of elements (reduced information) is the linear array that scans in one direction only. Each detector scans one line of the scene image. The complexity of the electronics is reduced, and the amount of information that is processed is increased. Therefore, the size of the scene to be viewed and the detail increases. Many types of mechanisms can be used to scan the scene. When you scan with two axes, the two scanning motions must be synchronized. The electronic signal that controls the sampling of the detectors must also be synchronized with the scanning motions. Front-End Optics The front-end optics collects the incoming radiant energy and focuses the image at the detectors. An example of front-end optics on a targeting pod is shown in Figure 6-5. The optics may be reflective or refractive, or a combination of both. Many systems offer a zoom capability, allowing a continuous change in magnification of the image without changing the focus. Spectral filters are used to restrict the wavelength of light entering the system. Spectral filters prevent unwanted wavelengths of light from reaching the detector and interfering with the imaging process. Refrigeration System A refrigeration system is needed in imaging systems because many types of IR detectors require low temperatures to properly operate. The two types of detector cooling systems that are used are the open-cycle and the closed-cycle types. Figure 6-5 — Front-end optics. In the open-cycle type of cooling, a reservoir of liquefied cryogenic gas is provided. The liquid is forced to travel to the detector, where it is allowed to revert to a gas. As it changes from a liquid to a gas, a great deal of heat is absorbed from the surrounding area and the detector. In the closed-cycle type of cooling, the gas is compressed, and the heat generated by the compression is radiated away through the use of a heat exchanger. The gas is then returned to the compressor, and the cycle repeats itself. Image Processing Systems The image processing system is used to convert the data collected by the detectors into a video display. Data from the detectors is multiplexed so that it can be handled by one set of electronics. The data is then processed so that the information coming from the detectors is in the correct order of serial transference to the video display. At this point, any other information that is to be displayed is 6-6 added. The signals from the detectors in many image processing systems are amplified and sent to light emitting diode (LED) displays. FORWARD LOOKING INFRARED SYSTEM The AN/ASQ-228 Advanced Targeting Forward Looking Infrared (ATFLIR) system (Figure 6-6) provides the operator with real-time, passive thermal and visible imagery during day and night operations. The ATFLIR system can be used to detect, classify, track, and designate both air-to-air and air-to-surface targets of interest that would be concealed from either visual observation or radar detection. The system was designed to give the operator the ability to deliver precision-guided ordnance at a standoff distance outside of anti-air weapon envelopes. The ATFLIR system scans an operator-selected portion of the terrain along the aircraft’s flight path and displays a televised image of the IR and visible patterns of the terrain. In addition, the ATFLIR system does not emit transmissions that can be detected by enemy forces. Although various types of FLIR systems used in the Navy, the ATFLIR system is a good example of the components and operational capabilities of other systems currently in use. Figure 6-6 — AN/ASQ-228 ATFLIR system. ATFLIR System Components The ATFLIR system consists of 25 different Weapons Replaceable Assemblies (WRAs). The WRAs are listed below and described in the following paragraphs: • Electro-optical sensor unit (EOSU) • Environmental control valve (ECV) • Eurocard modules • Laser electronics unit • Laser transceiver unit 6-7 • Advanced Navigation Forward Looking Infrared (ANFLIR) sensor • Pod adapter unit • Pod electronics housing • Power interrupt protector • Roll drive amplifier • Roll drive motor • Roll drive unit Electro-Optical Sensor Unit The EOSU (Figure 6-7) is a self-contained component designed to protect and seal the optics and laser equipment from moisture, contaminants, and electromagnetic interference. Housed within the EOSU are the ATFLIR midwave IR receiver, gimbal-mounted telescope, laser spot tracker, and visible electro-optical (EO) camera. All optical components are mounted on a one-piece, beryllium aluminum optical bench. The bench was designed to eliminate alignment errors when individual optical components are removed for maintenance. The outer structure of the EOSU is designed to withstand the wind loads of mach plus velocities associated with high-speed aircraft. The outer structure includes the windscreen, multispectral, and laser spot tracker windows. The optical bench is suspended in the outer structure on four vibration isolators and gimbals. The EOSU interfaces with many of the power supply and processor Eurocard modules. Figure 6-7 — ATFLIR electro-optical sensor unit. Environmental Control Valve The environmental control valve (ECV) regulates the aircraft cooling air for the installed components within the ATFLIR pod. In addition, the ECV enables airflow for the pod when the pod is operated on the ground. The ECV is a vital component to the ATFLIR system, especially in warmer operating areas. Eurocard Modules Eurocard modules (Figure 6-8) are individual circuit cards that are responsible for managing and routing a variety of signals to control the operational functions of the ATFLIR system. Some examples of the signals being routed and exchanged are pod control, temperature management, and video signal correction. The Eurocard modules are mounted in a cooled card cage within the pod electronics housing for easier maintenance access. 6-8 Laser Electronics Unit The laser electronics unit is the primary interface between the laser transceiver unit, the aircraft, and the pod. The laser electronics unit interfaces with the aircraft for discrete laser arming signals. The laser electronics unit contains three functional subunits for interface and power. Laser Transceiver Unit The laser transceiver unit provides the energy for laser generation, which enables the operator to deliver precision-guided ordnance on target, the first time. This component is purged with dry air and sealed to protect against contamination. The laser transceiver unit provides a Figure 6-8 — ATFLIR Eurocard modules. boresight reference source in the form of a laser diode, which produces a low-power signal that is precisely aligned to be parallel with the main beam output wavelengths. The unit delivers laser energy at repetition rate of 20 hertz (Hz) at a wavelength of 1.064 µm. The actual power output level of the laser energy being generated by the transceiver unit is classified information. Advanced Navigation Sensor The ANFLIR sensor is a self-contained FLIR imaging system that provides IR imagery (Figure 6-9) used by the operator to maneuver and navigate safely at low altitudes and high air speeds. The imagery delivered by the ANFLIR sensor is comparable to flying during daylight operations while operating at night. Pod Adapter Unit The pod adapter unit provides the mounting and interface for the aircraft, pod electronics housing, and ANFLIR sensor. When a pod is installed on the aircraft, the pod adapter unit provides the connection point for power, signal routing, and cooling air for the ATFLIR system. 6-9 Figure 6-9 — ANFLIR video. Pod Electronics Housing The pod electronics housing (Figure 6-10) provides mounting and interface for the pod adapter unit, laser transceiver, laser electronics unit, and environmental control valve. In addition, the pod electronics housing provides interface and mounting for the roll drive unit, roll drive amplifier, and Eurocard module cooled card cage and backplane. The pod electronics housing contains a singlepanel maintenance door for access to WRAs. Power Interrupt Protector Figure 6-10 — ATFLIR pod electronics housing. The power interrupt protector provides the ATFLIR system with three-phase, 400 Hz rectified power for 50 milliseconds when power from the aircraft is interrupted. Roll Drive Amplifier The roll drive amplifier (Figure 6-11, View A) is attached to the pod electronics housing and to the roll drive motor. The roll drive amplifier provides the drive power to the roll drive motor. Roll Drive Motor The roll drive motor (Figure 6-11, View B) is mounted to the roll drive unit. It is a brushless motor with an integral tachometer. Position readout is received with anti-backlash gearing and measuring pinion and ring gear position. The roll drive motor electrical interface is provided by the pod electronics housing. Figure 6-11 — ATFLIR roll drive amplifier and motor. 6-10 Roll Drive Unit The roll drive unit is the mechanical and electrical attachment between the EOSU and the pod electronics housing. Roll drive unit mechanical aspects include a cooling air path for the EOSU and ring gear drive. Roll axis rotation, and radial and axial alignment are also provided to the EOSU by the roll drive unit. ATFLIR Operational Capabilities The subsystems listed and described below will help you understand the operational capabilities of the ATFLIR system: • IR video • EO video • FOV and zoom • Point control • Track control • Laser and FLIR align • Laser energy • Laser range • Eyesafe • Laser spot tracker • ANFLIR • IR marker • Pod ECV • Built-in test Figure 6-12 — IR video. Infrared Video This subsystem provides the IR video (Figure 6-12) for the tactical aircrew display. IR, visible, and laser energy enters the telescope and is relayed off the pitch gimbal to beam splitters on the optical bench. The separated IR energy passes through the relay, the derotation mechanism, and then through the imager to the 640 X 480 element array. Nonuniformities in the raw image are corrected by the digital nonuniformity and scene-based digital nonuniformity modules before reticules are added by the video processor (VP). The VP also provides manual and automatic gain, level, and polarity control and then converts the digital video to standard RS-170 analog video for display in the cockpit. Electro-Optical Video This subsystem provides visible imagery for use by the operator. The EO camera is boresighted to the FLIR and laser optical path to ensure accuracy. Visible energy is separated from the laser and IR spectrums by beamsplitters and routed to a charge coupling device (CCD) camera. The CCD camera contains a mechanism to ensure the image being displayed maintains the correct horizon orientation. Video for the CCD camera is digitally corrected before being routed to the VP, where reticules are 6-11 added and control functions implemented before being converted to RS-170 analog video. The EO output utilizes the same video lines to the cockpit displays as the IR video subsystem. Field of View and Zoom There are three levels of optical FOV available for the operator using the ATFLIR system. They are the wide, medium, and narrow FOVs. The wide FOV is optically fixed at 1X magnification. The medium and narrow FOVs are optically fixed at 1X with a 2X magnification zoom capability. All three FOVs are implemented in the reflective telescope of the EOSU with switch in mirrors. Point Control The pointing and stabilization functions for the ATFLIR system are provided by the line of sight stabilization mirrors and the inertial measurement unit. These components interact with servos and servo controllers to enable the operator to point the ATFLIR system optics (IR, visible, and laser) at a designated area. Track Control The track control functions include both air-to-air and air-to-surface autotracking functions. The signal processor and pod controller WRAs command the line of sight through the point control and stabilization subsystem to maintain the tracked target where designated. Figure 6-13 shows an example of the ATFLIR system using track control. Laser and FLIR Align The laser and FLIR align is the autoalignment element in the point control and stabilization function. The ATFLIR contains alignment sources to each of the FLIR detector arrays, the CCD camera, and the laser line of sight. Auto-alignment occurs on a continual basis to ensure that the laser, FLIR, and CCD camera are co-aligned to the ATFLIR telescope line of sight. This process is vital to the precision delivery of guided ordnance. Laser Energy This subsystem controls when the laser energy is started and stopped by the laser transceiver. In addition, the subsystem manages the laser energy shutter to facilitate the built-in sampling of laser energy output parameters. Laser Range The laser range function provides target distances to the operator. Figure 6-13 — ATFLIR track control function. 6-12 Eyesafe Eyesafe enables the operator to place the laser transceiver into a training mode of operation. The training mode of laser operation simulates all of the tactical aspects of laser employment without emitting any laser energy. The training mode can be used in both the air-to-air and air-to-surface modes of operation. Laser Spot Tracker The laser spot tracker subsystem detects and receives ground or “buddy” designated laser energy. Advanced Navigation The ANFLIR subsystem (Figure 614) is a separable WRA that mounts inside the pod adaptor unit. The ANFLIR WRA provides the operator with the navigation capabilities that were described earlier. When installed, the WRA receives power and cooling air from the pod adaptor unit. This subsystem uses a dedicated RS-170 connection to provide navigational video. Infrared Marker The function of the IR marker is to provide a laser reference whose return energy can be seen by personnel equipped with night vision goggles. This function makes the infrared marker useful for night attacks where personnel on the ground can confirm that the correct target is being designated. Pod Environmental Control Unit Figure 6-14 — ANFLIR weapons replaceable The pod ECV regulates the airflow from the aircraft while in flight and assembly. allows the ground cooling fan to operate when the aircraft is on the ground. In addition, closed-loop cooling is provided by an air-to-air heat exchanger to the sealed optics in the EOSU and the laser assemblies. Built-In Test The built-in test (Figure 6-15) subsystem provides the operator with the ability to test the functionality of the ATFLIR system and components. Three separate built-in test functions are listed below: • Operational readiness test (ORT) • Initiated built-in test (IBIT) • Periodic built-in test (PBIT) 6-13 Figure 6-15 — Typical built-in test and fail code displays. Operational Built-In Test ORT occurs automatically when power is applied to the ATFLIR system. ORT is a test of system readiness that, when completed, will provide the operator with an overall status of the ATFLIR. Initiated Built-In Test IBIT provides the operator with a detailed end-to-end test of the ATFLIR system. The purpose of IBIT is to aid in isolation of suspected faulty component(s). Periodic Built-In Test PBIT is done continuously during the tactical operation of the ATFLIR system. However, PBIT will not start until the pod cool-down cycle is complete. Any failures detected during the PBIT cycle will be recorded and can be used in isolating faulty components. 6-14 End of Chapter 6 Infrared Review Questions 6-1. Natural light photography is an example of what type of remote sensing? A. B. C. D. 6-2. What is the infrared frequency range? A. B. C. D. 6-3. Temperature Reflectivity Visible light Color Infrared energy is separated into how many regions? A. B. C. D. 6-6. 1.00 and 7,200 nanometers 1.00 and 7,200 micrometers 0.72 and 1,000 nanometers 0.72 and 1,000 micrometers In what terms is thermal imaging referenced? A. B. C. D. 6-5. 300 megahertz to 400 gigahertz 400 megahertz to 300 gigahertz 300 gigahertz to 400 terahertz 400 gigahertz to 300 terahertz The infrared region exists between what electromagnetic spectrum? A. B. C. D. 6-4. Active only Passive only Inactive Active and passive One Two Three Four Matter emits infrared radiation above what temperature? A. B. C. D. -273 degrees Celsius -273 degrees Fahrenheit 0 degrees Celsius 0 degrees Fahrenheit 6-15 6-7. Which of the following qualities is desired in optical material used in infrared imaging systems? A. B. C. D. 6-8. What component in an infrared imaging system is the most important? A. B. C. D. 6-9. Transparent to visible light High coefficient of thermal expansion Low mechanical strength High surface hardness Detectors Optics Receiver Sensor Photographic film is an example of what type of detector? A. B. C. D. Elemental Imaging Photon Thermal 6-10. What type of energy-matter interaction involves the absorption of radiant energy in the detector? A. B. C. D. Thermal effect Photon effect Elemental Imaging 6-11. What type of photon effect occurs when radiant energy changes the detector materials electrical conductivity? A. B. C. D. Photo-emissive Photoelectric Photoconductivity Photon effect 6-12. What type of photon effect occurs when the radiant signal causes a difference of potential across a P material and N material (PN) semiconductor junction? A. B. C. D. Photo-emissive Photon effect Photoconductivity Photoelectric 6-16 6-13. What component collects the incoming energy and focuses the image at the detectors? A. B. C. D. Scene dissection system Front end optics Image processing system Detectors 6-14. What component converts the data collected by the detectors into a video display? A. B. C. D. Scene dissection system Front end optics Image processing system Detectors 6-15. What type of detector cooling systems uses a heat exchanger and a compressor? A. B. C. D. Single cycle Quad cycle Closed cycle Open cycle 6-16. What is the nomenclature of the Advanced Targeting Forward Looking Infrared system? A. B. C. D. AN/ASQ-228 AN/ASQ-328 AN/ASQ-441 AN/ASQ-501 6-17. What component is described by the EOSU acronym? A. B. C. D. Electrically operated sensor unit Electro-optical sensor unit Environment oxygen siphon unit Element oxidizing separating unit 6-18. Other than the midwave infrared receiver, gimbal-mounted telescope, and laser spot tracker, what component does the electro-optical sensor unit house? A. B. C. D. Environmental control valve Eurocard modules Roll drive unit Power interrupt protector 6-19. The optics bench is made from what type of material? A. B. C. D. Titanium Carbon steel Aluminum Iron 6-17 6-20. What component is responsible for managing and routing pod control and video correction signals? A. B. C. D. Gimbal-mounted telescope Laser transceiver unit Pod adapter unit Eurocard modules 6-21. Energy for precision ordnance guidance is provided by what component? A. B. C. D. Pod adapter unit Laser transceiver unit Eurocard module Windscreen 6-22. What component provides three-phase, 400 hertz rectified power to the pod when power flow is interrupted? A. B. C. D. Eurocard module Roll drive amplifier Laser transceiver Power interrupt protector 6-23. What component provides power to the roll drive motor? A. B. C. D. Power interrupt protector Eurocard module Roll drive unit Roll drive amplifier 6-24. What subsystem generates visible imagery for use by the operator? A. B. C. D. Infrared/video Electro-optical/video Point control Infrared marker 6-25. What subsystem auto-aligns the pod optics to ensure the accuracy of target designation? A. B. C. D. Infrared/video Electro-optical/video Laser/Forward Looking Infrared align Track control 6-18 6-26. What subsystem provides a laser reference that can be seen by personnel using night vision goggles? A. B. C. D. Infrared/video Electro-optical/video Point control Infrared marker 6-27. What Weapons Replaceable Assembly can be installed into the pod to provide the operator with low-level navigation imagery? A. B. C. D. Point control Electro-optical/video Advanced Navigation Forward Looking Infrared Pod environmental control valve 6-28. What type of built-in test is initiated by the operator? A. B. C. D. Periodic Operational System Initiated 6-29. What type of built-in test continually occurs after pod cool-down is complete? A. B. C. D. Periodic Operational System Initiated 6-30. Other than the periodic built-in test, what test can help isolate a suspected faulty component? A. B. C. D. Periodic Operational System Initiated 6-19 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. If you have an idea for improving this manual, or if you find an error, a typographical mistake, or an inaccuracy in CNATT manuals, please write or e-mail us, using this form or a photocopy. Be sure to include the exact chapter number, topic, detailed description, and correction, if applicable. Your input will be brought to the attention of the Technical Review Committee. Thank you for your assistance. Write: CNATT Rate Training Manager 230 Chevalier Field Avenue Pensacola, FL 32508 E-mail: Refer to NKO ATO rate training Web page for current contact information. 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CHAPTER 7 WEAPONS SYSTEMS As a result of major developments in current aircraft design and computer technology, modern aircraft are able to deliver sophisticated weapons to a target automatically and with unprecedented accuracy. Aircraft are designed and built as a completely integrated weapons system. In other words, the weapons subsystems are interconnected and dependent on each other or on other aircraft systems. When aviation electronics technicians are testing, troubleshooting, or performing maintenance on an avionics system, they must be aware of the effects the system can have on ordnance. To illustrate this fact, this chapter will provide you with some examples of the types of weapons being employed in the fleet. In addition, three different types of aircraft armament systems and controls will be discussed. They are the Fighter/Attack (F/A)-18E/F Super Hornet, the Patrol (P)-3 Orion, and the Multi-Mission Helicopter (MH)-60R Seahawk. The three platforms represent aircraft being used to support the strike, fighter, Antisubmarine Warfare (ASW), and Anti-Surface Warfare (ASUW) mission areas. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Identify the different homing-missile guidance systems. 2. Recognize the common weapons being employed in the fleet. 3. Recognize the armament systems and subsystems used in strike fighter aircraft. 4. Describe the functions of strike fighter aircraft armament systems and subsystems. 5. Recognize the armament systems and subsystems used in ASW and ASUW aircraft. 6. Describe the functions of ASW and ASUW aircraft armament systems and subsystems. COMMON WEAPONS Aviation electronics technicians are routinely tasked with performing armament release and control checks. Therefore, it is important to identify some basic concepts about weapon guidance, and to recognize some common weapons in order to better understand armament control systems. Guidance and Control Missile guidance systems include electronic sensing equipment that initiates the guidance orders and the control system that carries them out. Homing-type, air-launched, guided missiles are currently used. A homing guidance system is one in which the missile seeks out the target, guided by some physical indication from the target itself. Homing systems are classified as active, semi-active, and passive. Active In the active homing system (Figure 7-1), target illumination is supplied by a component carried in the missile, such as a radar transmitter. The radar signals transmitted from the missile are reflected off the target and back to the receiver in the missile. These reflected signals give the missile information such as the target's distance and speed. This information lets the guidance section compute the correct angle of attack to intercept the target. The control section that receives electronic commands 7-1 Interaction Available from the guidance section controls the missile’s angle of attack. Mechanically manipulated wings, fins, or canard control surfaces are mounted externally on the body of the weapon. They are actuated by hydraulic, electric, or gas generator power, or combinations thereof, to alter the missile's course. Semi-Active In the semi-active homing system (Figure 7-2), the missile gets its target illumination from an external source, such as a transmitter carried in the launching aircraft. The receiver in the missile receives the signals reflected off the target, computes the information, and sends electronic commands to the control section. The control section functions in the same manner as previously discussed. Interaction Available Interaction Available Figure 7-1 — Active homing system. Figure 7-3 — Passive homing system. Figure 7-2 — Semi-active homing system. Passive In the passive homing system (Figure 7-3), the directing intelligence is received from the target. Examples of passive homing include homing on a source of infrared rays (such as the hot exhaust of jet aircraft) or radar signals (such as those transmitted by ground radar installations). Like active homing, passive homing is completely independent of the launching aircraft. The missile receiver receives signals generated by the target, and then the missile control section functions the same. 7-2 Air-to-Air Weapons The following paragraphs provide an overview of the Air-launched, Aerial Intercept Guided Missile (AIM)-9, AIM-7, and AIM-120 air-to-air (A/A) missiles. AIM-9 Sidewinder Series AIM-9M Sidewinder missiles are supersonic, A/A weapons with passive infrared target detection, proportional navigation guidance, and torque-balanced control systems. The AIM-9M offers improved defense against infrared countermeasures and enhanced background discrimination capability. The latest variant of the Sidewinder missile is the AIM-9X (Figure 7-4). The AIM-9X is a supersonic, A/A, short-range guided weapon that is capable of both offensive and defensive counter-air missions in day/night operations. The AIM-9X provides extremely high off-boresight acquisition and launch envelopes, enhanced maneuverability, and improved target acquisition ranges. Figure 7-4 — AIM-9X Sidewinder. AIM-7 Sparrow The AIM-7 Sparrow is a radar-guided, A/A missile that contains a high-explosive warhead. The AIM-7 has all-weather, all-altitude operational capability and uses a semi-active guidance system to seek out and destroy a target. Semi-active guidance systems are dependent on interface and input from a host aircraft for target information and intercept guidance. AIM-120 Advanced Medium-Range Air-to-Air Missile The AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) (Figure 7-5) is an all-weather weapon that has beyond-visual-range targeting capability. The AIM-120 was designed and produced to serve as follow-on to the AIM-7 Sparrow missile series. The AIM-120 uses semi-active guidance until it approaches its target. When the missile is close enough, it switches to an internal radar system (active guidance) to intercept the target. The proximity active guidance capability allows an AIM-120compatible aircraft to engage several targets simultaneously. Figure 7-5 — AIM-120 AMRAAM. 7-3 Air-to-Ground Weapons The following paragraphs provide an overview of guided bomb units (GBUs), the High-Speed AntiRadiation Missile (HARM), the Maverick missile, the Hellfire missile, and torpedoes. Guided Bomb Units The Navy employs a variety of precision GBUs to disable and destroy enemy targets. Most GBUs are general-purpose bombs that are retrofitted with a guidance package. Examples of the variety of GBUs being employed operationally are described below. • The GBU-10/12/16 series employs laser guided, general-purpose bombs outfitted with a computer control group and guidance fins. • The GBU-24 Paveway III series employs 2,000-pound laser-guided bombs designed to be hard target penetrators. The GBU-24 is a general-purpose bomb outfitted with a computer control group and guidance fins. • The Joint Direct Attack Munition (JDAM) (Figure 7-6) series bombs are general-purpose weapons outfitted with an inertial navigation system and global positioning system guidance sets. The JDAM is used for precision strike capabilities in all weather conditions. Figure 7-6 — Joint Direct Attack Munition. AGM-88 High-Speed Anti-Radiation Missile The Air-Launched, Surface Attack, Guided Missile (AGM)-88 HARM (Figure 7-7) is a supersonic, airto ground, guided missile. The HARM is used to detect, attack, and destroy enemy radar systems. The HARM uses a proportional guidance system to target and destroy enemy radar sites. Figure 7-7 — AGM-88 HARM. 7-4 AGM-65 Maverick The AGM-65 Maverick is an air-to-surface tactical missile designed for close air support, interdiction, and defense suppression. The AGM-65 is effective against a wide range of tactical targets, including armor, air defenses, ships, ground transportation, and fuel storage facilities. The AGM-65 missile variants use laser or infrared guidance. AGM-114 Hellfire The AGM-114 Hellfire (Figure 7-8) missile is an air-to-ground (A/G), laser-guided, subsonic missile with significant antitank capacity. The AGM-114 missile can be employed against tanks, structures, bunkers, and slow-moving aircraft. An AGM-114 missile can be guided to a target either from inside the aircraft or by laser energy outside the aircraft. Figure 7-8 — AGM-114 Hellfire. Torpedoes The Navy employs three types of torpedoes as the primary weapons for ASW operations. They are the Mark (MK) 46, MK 50, and MK 54. • The MK 46 torpedo is a dual-speed, active or active/passive weapon with enhanced target acquisition, and improved maintainability and reliability. • The MK 50 torpedo is a highly capable weapon designed to counter the fast, deep-diving, double-hulled nuclear submarine threat. MK 50 torpedoes offer increased lethality, speed, depth, and endurance characteristics. • The MK 54 torpedo uses existing torpedo hardware and software from the MK 46, MK 50, and MK 48 (used by submarines) torpedo programs and integrates state-of-the-art digital signalprocessing technology. F/A-18E/F SUPER HORNET The F/A-18 series of aircraft are all-weather, multirole fighter/attack aircraft. The Navy tactically uses five variants of the F/A-18 series (Figure 7-9). They are the F/A-18A/C/E/F and the EA-18G. There is commonality of weapons systems, avionics, and software among F/A-18 variants. Therefore, the following paragraphs focus on the armament systems and subsystems of the F/A-18E/F. The F/A18E/F Super Hornet provides significant improvements in combat range, payload, and survivability in comparison to legacy F/A-18 aircraft. Armament System Basic Controls The following paragraphs provide an overview of the F/A-18E/F armament system. The armament system basic controls consist of the following components: armament system circuit breakers, landing 7-5 gear control panel, armament safety override switch, mission computers (MCs), armament computer, and signal data convertor. Interaction Available Armament System Circuit Breakers The armament system circuit breakers are located on the power distribution panels behind the right- and left-hand maintenance access doors. Landing Gear Control Panel The landing gear control handle in the DOWN Figure 7-9 — F/A-18 variants. position disables normal weapons release, launch, and fire signals. In the UP position, 28 volts direct current is directed from the main landing gear weight-off-wheels relay to the master arm circuit breaker. Armament Safety Override Switch The armament safety override switch is on the nose wheel well maintenance panel. In the OVERRIDE position, it provides a parallel path for master arm power for ground operations of the armament release and control systems. Mission Computers Two digital data computers make up the MC system and control the avionics systems. They interface with the armament computer and allow power routing to signal data convertor controls for weapon release. Power to the digital data computers is controlled by the MC switch on the MC/hydraulic isolation (MC/HYD ISOL) panel. Armament Computer The armament computer (Figure 7-10) interfaces with and is controlled by the MC. The armament computer interfaces Figure 7-10 — Armament computer. 7-6 with and controls the weapon station signal data control converters; monitors and controls gun fire rates; and provides electric fuzing voltage. The armament computer contains the digital weapon insertion panel (WIP) used to enter the weapon type and fuzing requirements for each station loaded. The weapon-type code entered for each loaded station must match the weapon loaded, and the nose/tail fuze code entered must be compatible. Otherwise, the armament computer will not allow it to release normally. For weapons without nose/tail fuzes, the codes in the armament computer must still match the weapon loaded. In addition, the quantity of rounds loaded in the M61 gun system is also entered using the WIP. Signal Data Converter Control The signal data converter control provides interface with the armament computer and weapons loaded. The seven pylon converter controllers are identical. The two fuselage converter controllers are identical and also provide interface to the wing tip launchers. In addition, the signal data converter controllers provide release voltage and weapons/rack/launcher status to the armament computer. Cockpit Basic Controls The following paragraphs provide a brief overview of the basic controls and displays used to control armament systems in the F/A-18E/F. Digital Display Indicators Cockpit digital display indicators (DDIs) are located on the main instrument panel (left and right). DDIs are identical and display the same information, although not at the same time. The stores management system (SMS) uses the DDIs to display weapon, function, and option. The operator makes a selection on the DDIs by using the 20 pushbuttons around the edge of the display screen and by using the up-front control display (UFCD) for quantity, multiple, and interval selection. Upon initiation of the stores display, the number, station, master arm status, and type of weapons loaded are shown in the wing form display. The wing form (Figure 7-11) is an outline of the aircraft that identifies type, station, number, and status of weapons loaded on the aircraft. A weapon is identified by entering a code on the armament computer WIP. Data is transmitted to the MC system, which displays the entered code as an acronym. The acronym is displayed in the wing form for the station in which the code was entered. The operator makes a weapons selection for A/G weapons by pressing the pushbutton switch next to the acronym of the desired weapon. When this switch is pressed, a box appears around the weapon acronym, indicating that weapon is selected. Figure 7-11 — Typical wing form display. 7-7 Up-Front Control Display UFCD is a touch-sensitive display that provides the keypad, option select, scratchpad, and option displays. The option select display allows selection of quantity (QTY), multiple (MULT), and interval (INT) options. After selecting an option, the operator uses the keypad option to enter a number, which will be displayed on the scratchpad display. After verifying the number on the scratchpad display as correct, the operator presses the keypad option enter (ENT) to transmit the number to the MC system. The MC provides the data to the armament computer for storage and display on the DDIs. Head-Up Display Located on the pilot’s main instrument panel, the head-up display (HUD) allows for weapon displays and visual markers. Master Arm Control Panel The master arm control panel (Figure 7-12) assembly allows the operator to select the A/A, A/G, and MASTER modes. The panel also contains the emergency jettison (EMRG JETT) and push to jettison (PUSH TO JETT) switches. Rear Cockpit Basic Controls An overview of the rear cockpit armament basic controls of the F/A-18F series aircraft is described in the following paragraphs. Digital Display Indicators The DDIs are located on the rear cockpit instrument panel. The rear DDIs provide independent displays but are also capable of providing the same display as the cockpit. Rear Advisory and Threat Warning Indicator Panel The rear advisory and threat warning indicator panel assembly contains the A/A and A/G switches, and on lot numbers 166449 and up, the MASTER ARM annunciator and LASER arm annunciator. Left- and Right-Hand Controllers The rear left- and right-hand controllers contain numerous switches for weapons control, and on lot numbers 166449 and up, they contain selection, launch, and release of weapons. Armament Subsystems Figure 7-12 — Master arm control panel. The next section of this chapter provides an overview of the armament subsystems associated with the F/A-18E/F and will include the following systems: air-air missile, air-to-ground weapons control, jettison, gun control, and integrated defensive electronic countermeasures dispensing. 7-8 Air-to-Air Missile Control Systems The A/A missile control systems provide the ability to select and launch A/A missiles, including the AIM-7 Sparrow, AIM-9 Sidewinder, and AIM-120 AMRAAM. Some of the A/A missile controls are located on the aircraft controller grip, as shown in Figure 7-13. The cockpit switches associated with the A/A weapons system are described below. • The A/A weapons select switches are four-position switches used to select the A/A weapons loaded on the aircraft. • The CAGE/UNCAGE switch is used to control the selected AIM-9M seeker head position. • The A/A missile trigger switch is a two-position switch. The first detent initiates the HUD camera, and the second detent initiates A/A weapons launch. • The A/A weapons release switch is located on the rear cockpit right-hand controller of the F/A-18F and is a single pushbutton switch used to initiate A/A missile launch. • The infrared cool (IR COOL) switch is a threeposition switch that controls the flow of coolant/high-pressure pure air to the AIM/CATM-9M seeker head. • The weapon (WPN) volume control is used to control the volume of the AIM-9 lock-on tone. • The radar control switch controls power to the radar system. The radar system is used to interface and control the AIM-7 and AIM-120 missiles. Figure 7-13 — Aircraft controller grip. Air-to-Ground Weapons Control System The A/G weapons control system provides the ability to select, launch, fire, or release A/G missiles, bombs, and rockets. Some of the A/G weapons controls are on the left and right throttle grips, shown in Figure 7-14. Cockpit switches and displays used in the A/G weapons subsystem are described below. • The CAGE/UNCAGE switch is used to control the seeker head functions of the Maverick missile system. The switch can also be used to initiate functions of the HARM missile. • The throttle designator control (TDC) switch is used to control the position of video-capable weapons targeting crosshairs. • The designator control switch is used to control the positon of video-capable weapons targeting crosshairs in the F/A-18F rear cockpit. • The HARM sequence/forward looking infrared field-of-view/raid (FLIR FOV/RAID) switch is used to switch the sequences between HARM targets. 7-9 • The multi-function switch is a three-position switch used for weapons control. The forward position sequences between HARM targets. The aft position cages/uncages selected seekers. The down position functions as the RAID/FLIR switch. • The A/G weapons release switch initiates launch, firing, or release of all selected A/G weapons. • An UFCD is used to enter the quantity, multiple, and interval options for A/G weapons data for the MC system. • The electrical fuzing system provides the voltage to arm electrically fuzed A/G weapons. The system supplies the selected proximity (VT), instantaneous (INST), delay 1 (DLY 1), or delay (DLY 2) voltage when the bomb rack hooks open for weapons release. Figure 7-14 — Left and right throttle grips. Jettison System The Jettison system provides a method of jettisoning weapons/stores from the aircraft. The following paragraphs describe controls and indicators of the jettison system. • Emergency jettison is a mode of jettisoning all weapons/stores from the seven pylon stations. o The EMERG JETT PUSH TO JETT switch (Figure 7-15) initiates emergency jettison from all pylon stations. • Selective jettison is a mode of individually jettisoning the left fuselage missile, right fuselage missile, racks, launchers, and stores. o The SELECT JETT switch is a five-position switch used to select the station or type of jettison needed. o The JETT STATION SELECT switches are seven pushbutton switch/indicators that correspond to the aircraft left outboard (LO), left midboard (LM), left inboard (LI), center (CTR), right inboard (RI), right midboard (RM), and right outboard (RO), and are used to select the pylon station for selective jettison or auxiliary release. 7-10 Figure 7-15 — Typical emergency jettison switch. • Auxiliary release is a gravity mode of jettison used on selected pylon stations when emergency and selective jettison fails. o The auxiliary release (AUX REL) switch is a two-position switch used to enable or inhibit auxiliary release. The ENABLE position enables auxiliary release. The normal (NORM) position inhibits auxiliary release. o The SELECT JETT, JETT switch initiates select jettison or auxiliary release of the selected stations. Gun System Controls The gun system provides the means to select, arm, and fire the M61 gun in A/A and A/G modes. Firing voltage, round count, and rate of fire are all controlled by the armament computer. Cockpit controls for the gun system are described below. • The A/A weapons select switch is a four-position switch used to select A/A weapons. The aft position of the switch selects the gun. • The A/A missile trigger switch is a two-position switch. When the gun has been selected, the switch initiates the HUD camera at the first detent and fires the gun at the second detent. Integrated Defensive Electronic Countermeasures (IDECM) Dispensing Systems The integrated defensive electronic countermeasures (IDECM) dispensing systems include the AN/ALE-47 and AN/ALE-50A integrated countermeasures system. The systems used in the IDECM are described below. • The AN/ALE-47 dispensing system provides for threat-adaptive, reprogrammed computer- or manual-controlled dispenses of decoys to confuse and jam enemy electronic tracking, missile guidance, and homing systems. The system ejects expendable payloads of chaff, flares, or radio-frequency (RF) jammers from four dispenser magazines located on the lower fuselage aft of the engine intakes. • The AN/ALE-50A dispensing system provides for reprogrammable, computer- or manual-controlled dispenses of an active RF transmitting towed decoy (Figure 7-16). The magazine with three decoys is installed in the lower fuselage between the main landing gear doors. Figure 7-16 — AN/ALE-50 towed decoy. 7-11 P-3 ORION The P-3 Orion (Figure 7-17) is a four-engine, low-wing aircraft designed for patrol and ASW. The armament system consists of equipment for loading, carrying, and releasing weapons and search stores. Weapons include bombs, mines, torpedoes, missiles, and rocket launchers. Search stores include sonobuoys, parachute flares, smoke markers, bathythermograph buoys, and signal underwater sound (SUS). Armament Systems Basic Controls The basic P-3 ASW weapons system consists of the equipment and accessories necessary for carrying and releasing kill stores and search stores. Armament basic controls consist of the following components: pilot armament control panel, armament control box, weapons release switches, armament safety circuit safety disable switch, forward interconnection box, aft interconnection box, and armament circuit breaker panel. Figure 7-17 — P-3 Orion. Pilot Armament Control Panel The pilot armament control panel (Figure 7-18) provides the pilot with control of all kill and search stores. The switches and controls that are found on the armament control panel are as follows: • The ARM HAZARD warning light warns the pilot of a malfunction of any of the 18 weapon release buffer relays. • The MASTER ARM switch controls power for enabling arming and normal release of the wing and bomb bay stores. • The MASTER ARM cue light advises pilot to change the position of the MASTER ARM switch in response to action by the tactical coordinator (TACCO) or computer. Figure 7-18 — Pilot armament control panel. • The BOMB BAY door switch controls opening and closing of the bomb bay doors. • The BOMB BAY cue light advises the pilot to change position of the BOMB BAY door switch in response to action by the TACCO or computer. • The search power (SRCH PWR) switch allows the pilot final control over the release of all search stores; the computer monitors the position of this switch. 7-12 • The SRCH PWR cue light, when illuminated, tells the pilot to turn the search power switch ON; it lights only when the switch must be moved from OFF to ON; there is no offline function of this light. • The KILL READY cue light advises the pilot that preparations are completed for release of the weapon/store. • The JETTISON switch initiates release of all wing and bomb bay weapons/stores in a safe (unarmed) condition. • The manual armament select (MANUAL ARMT SEL) panel provides the TACCO with controls necessary for manual mode of operation. Armament Control Box In some series of P-3 Orion aircraft, the pilot armament control panel, wing jettison, and special weapon armament panel have been replaced by an armament control box (ACB). The ACB is located on the center pedestal at the flight station. The ACB combines the functionality of the two panels and provides the pilot with command control of all kill and search stores. Weapon Release Switches Both the pilot and copilot have switches for the release of weapons. The switches are located on the inboard side of the control wheels and are labeled stores release (STORES REL). Weapons release can also be made by depressing the release (REL) switch located on the TACCO manual armament select panel. Armament Safety Circuit Disable Switch The armament safety circuit disable switch is a momentary contact switch used to bypass the landing gear lever switch to permit operation of the weapons system when the aircraft is on the ground. Forward Interconnection Box A395 The forward interconnection box A395 contains eight subassemblies that provide control circuitry for selection, arming, torpedo presetting, and release of weapons loaded in the bomb bay and jettison of weapons loaded at bomb bay and wing stations. Aft Interconnection Box A269 The aft interconnection box A269 contains four subassemblies that provide control circuitry for selection, arming, and release of weapons loaded at wing stations. Armament Circuit Breaker Panel The armament circuit breakers on the forward load center supply power to the armament circuit breakers located on the forward electronics circuit breaker panel. Armament Subsystems The following paragraphs provide general information on the aircraft armament subsystems, components, and armament subsystems, to include torpedo system, Harpoon system, Maverick system, jettison system, and defensive countermeasure systems. 7-13 Torpedo System Basic Controls The aircraft’s torpedo system consists of the following basic controls: • The torpedo presetter (TORP Presetter) panel provides the controls and indicators for manual or automatic preset of Mk 46, Mk 50, and Mk 54 torpedoes. • Torpedo MK 50 heater control panel provides selection of Mk 50 heater power. • DIRECTED SEARCH MODE selector panel (Figure 7-19) provides directed search capability for Mk 46, Mk 50, and Mk 54 torpedoes. Figure 7-19 — DIRECTED SEARCH MODE selector panel. Harpoon System Basic Controls The Harpoon missile system basic controls are described below. • The Harpoon aircraft command launch control (HACLC) panel provides power application, controls, and displays for the Harpoon missile. The controls and displays are used for manually defining missile selection/deselection, target range, relative bearing, attack seeker modes, aircraft true airspeed, and altitude inputs. • The data processor computer is a general-purpose, stored program, digital computer that provides the digital communications link between the HACLC and the Harpoon missile. The data processor computer serves as an interface unit to obtain control and data information from existing aircraft systems. It performs the launch interlocks and prelaunch computations for missile initialization and control of the launch sequence. Maverick Missile Control System Basic Controls The Maverick missile control system (MMCS) provides the capability to individually identify and track up to four separate targets with missiles loaded on wing stations 10, 11, 16, and 17. The MMCS is composed of the following basic controls. • The missile interface box is the heart of the MMCS and is the one component through which all signals used to control the MMCS are routed. • The missile armament panel (Figure 7-20) provides the TACCO with the status of the MMCS and allows the TACCO to control various missile functions. The TACCO can select up to four missiles to enter the launch mode (land or ship), initiate missile cooling, and activate the missile. • The missile/infrared detection set (IRDS) status panel provides missile and IRDS control status indicators. • The missile controllers are two identical and interchangeable joysticks used to provide missile and IRDS turret controls to the missile interface box. 7-14 Figure 7-20 — Missile armament panel. Jettison System All kill stores on the aircraft will be jettisoned in an unarmed condition when the pilot places the JETTISON switch on the pilot armament control panel in the ACTUATED position. Kill stores are jettisoned from the aircraft within a 20-second period. Components and functions of the jettison system are described below. • The wing jettison and special weapon armament panel provides the pilot with a means of jettisoning stores from wing stations only in an emergency and secondary release of bomb bay stations 2C, 4C, and 8C. • The secondary rack lock panel, 962046-10, is used to unlock bomb bay racks at stations 2C, 4C, and 8C. The panel is used with the wing jettison and special weapon armament panel. Defensive Countermeasures The AN/ALE-39 and AN/ALE-47 countermeasures dispensing systems and controls are described below. • The AN/ALE-39 countermeasures dispensing system, in conjunction with the AN/AAR-47 missile warning set (MWS), is designed to protect the aircraft from infrared guided missiles. The countermeasures dispenser (CMD) system installed in this aircraft was designed to only dispense flare payloads. o The CMD control panel provides the functional interface to the ALE-39 countermeasures dispensing system. o The AN/ALE-39 CMD programmer generates control signals for programmed or single ejection of payload sequences controlled by the CMD control and initiated manually or automatically by the MWS. • The AN/ALE-47 countermeasures dispensing system, in conjunction with the AN/AAR-47 MWS, is designed to protect the P-3C Anti-Surface Warfare Improvement Program (AIP) aircraft from surface-to-air and air-to-air missiles. The AN/ALE-47 system has the capability to automatically dispense a combination of chaff, flare, or jammer payloads. An example of the ALE-47 cockpit controls is shown in Figure 7-21. o The dispenser housings are located underneath the aircraft and are designed to remain installed in the aircraft for quick loading and unloading of the magazine assemblies. o The magazine assemblies are loaded into each dispenser housing. Each magazine is partitioned into two sections, tubes 1 through 10 and tubes 11 through 30. MH-60R SEAHAWK Figure 7-21 — AN/ALE-47 cockpit controls. The MH-60R Seahawk (Figure 7-22) helicopter primary mission areas are ASW and ASUW. Secondary missions include fleet support, surveillance, search and rescue, medical evacuation logistics, vertical replenishment, and communication relay. The following paragraphs provide a brief description of the aircraft armament systems and jettison systems. 7-15 Armament System Basic Controls The MH-60R armament system basic controls consist of the following components: weight-onwheels (WOW) switch, disabling switch for armament safety circuit, data handling system, primary mission/flight computer, SMS, and processing interface units. Weight-on-Wheels Switch The WOW switch functions as a safety interlock by disabling release and jettison circuits while the aircraft is on deck. Disabling Switch for Armament Safety Circuit This switch functions as an override to disable the WOW switch when the aircraft is on deck. The purpose of this switch is to allow operational testing of the armament system. Figure 7-22 — MH-60R Seahawk. Data Handling System The data handling system provides for the operator interface, processing, and display of all avionics and weapons systems. Primary Mission/Flight Computer The primary mission/flight computer is a digital computer that interfaces with all weapons and avionics systems and performs all processing for displays, built-in-test (BIT), and armament system functions. Stores Management System The SMS provides for the interface, control, and release functions of weapons and stores from the aircraft weapon stations and launchers. Processing Interface Units The processing interface units provide the interface between the weapons/stores and the primary flight/mission computer and other onboard avionics systems. Cockpit Basic Controls The following paragraphs provide a brief overview of the armament displays, controls, and components to include armament control indicator, mission displays, and control indicators. Armament Control Indicator Figure 7-23 — Armament control indicator. The armament control indicator (ACI) panel (Figure 7-23) is located on the lower console and is a component of the SMS. The ACI contains the covered MASTER ARM and ARM SAFE indicators. In 7-16 addition, the ACI contains control functions for the jettison, sonobuoy, and Hellfire armament subsystems. Mission Displays The mission displays are located on both pilot and copilot instrument panels and are components to the data handling system. The displays provide BIT, caution/advisory indications, and other SMS selectable information. Information and data are selectable with the 22 pushbutton switches located around the display bezel. Control Indicators Control indicators are located on both the pilot and copilot lower console and are components to the data handling system. Control indicators consist of three keyboards and are used to interface with aircraft avionics systems. Sensor Operator Station Basic Controls The following paragraphs provide a brief overview of the displays located at the sensor operator station. Mission Display The sensor operator mission display is located on the sensor operator console. The display performs the same functions as the pilot/copilot display. Control Indicator The sensor operator control indicator is located on the sensor operator console and oriented horizontally instead of vertically. This component provides interaction with avionics systems from the sensor operator console. Armament Subsystems This section discusses the armament subsystems associated with the MH-60R platform. This section discusses the armament subsystems associated with the MH-60R platform and describes the following subsystems: torpedo release system, sonobuoy launch system, AGM-114 Hellfire missile system, defensive countermeasures, and jettison system. Torpedo Release System The torpedo release system is capable of controlling and releasing up to four torpedoes. Torpedo system station and type selection, moding, and all other presetter functions are performed through the use of indications and alerts displayed by the data handling subsystem control indicators and mission displays. The torpedo release system consists of the following components: • The signal data convertor provides MK 50 torpedo heater power. • The hand control unit contains the RELEASE CONSENT switch that enables the release of torpedoes. Sonobuoy Launch System The sonobuoy launch system is capable of controlling and launching up to 25 sonobuoys. The system consists of the following components: • The sonobuoy launcher provides a housing and launch platform for 25 sonobuoys. 7-17 • The pneumatic supply module and manifold consists of a pressure bottle, pressure gauge, manual dump valve, and a SAFE/ARM lever. The supply module provides the pneumatic charge that ejects the selected sonobuoy. • The distribution module connects the compressed air supply with the selected launcher tube by way of a rotary valve. Stepper motor drives the rotary valve to the selected tube and is stopped by a position potentiometer. A selection knob on the distribution module provides manual selection of a sonobuoy tube. A distribution valve lock allows the rotary valve to be locked in any tube or vent position and indicator window. • The signal data converter is a component of the SMS that provides power to the sonobuoy launch system. • The BUOY LAUNCH RDY AWAY switch and indicator are used to manually launch a sonobuoy from a loaded launch tube. An example of the MH-60R sonobuoy launch system is shown in Figure 7-24. Figure 7-24 — Sonobuoy launch system. AGM-114 Hellfire Missile Control System The AGM-114 Hellfire missile control system provides for the carriage and launch of the AGM-114 Hellfire missile. The Hellfire missile system consists of the following basic components and controls: • The extended pylon is located on the port side aft of the aircraft and provides for the carriage of the Hellfire missile. • The AN/AAS-44 FLIR subsystem provides the capability to detect targets, determine target range, and laser designate the target for Hellfire guidance. FLIR system displays are provided on the mission displays. • The rotor overspeed and FLIR switch assembly panel contains the LASER and GIMBLE ENABLE/DISABLE switches. The switches either enable or inhibit laser firing and FLIR turret slewing. The FLIR laser can also be enabled and disabled from the sensor operator utility light panel. • The hand control unit provides the operator interface for the FLIR and to launch Hellfire missiles. • The signal data converter provides the power control and interface for the M299 Hellfire launcher. 7-18 • The M299 Hellfire launcher is installed on the extended pylon and is used to mount and launch the Hellfire missile. Jettison System The system is capable of jettisoning all weapons/stores or selected weapons/stores. The jettison system will be armed when the aircraft is in a weight-off-wheels condition or by engaging the armament safety bypass circuit. Activating the emergency jettison panel ALL STORE JETT switch will jettison all weapons/stores with the exception of jettisonable AN/ALE-47 countermeasures dispensing system expendables. Selecting the MASTER ARM switch on the ACI, then selecting the appropriate weapon station or system, and actuating the SELECT JETTISON switch selectively jettisons weapons, stores, or AN/ALE-47 countermeasures dispensing system expendables. Defensive Countermeasure System The MH-60R uses the AN/ALE-47 countermeasures dispensing system (Figure 7-25) to protect the aircraft against anti-air threats. The AN/ALE-47 countermeasures dispensing system provides for threat-adaptive, reprogrammable, computer-controlled dispensing of decoys to confuse and jam enemy electronic tracking, missile guidance, and homing systems. The system ejects expendable payloads consisting of chaff, flares, or RF jammers in manual, semiautomatic, or automatic modes based on software-controlled programs from two 32-round dispenser magazines located on the tail pylon. The AN/ALE-47 consists of the following components: • The AN/ALE-47 programmer functions as the central processor for the AN/ALE-47 system; it contains dispense programming software and controls dispensing for all modes of operation. • The dispenser magazine identification (ID) switches consist of two four-position (A–D and 1–4) rotary switches that indicate specific expendable payload load outs for decoding and to be used by the programmer. • The AN/ALE-47 safety switch/pin is opened by inserting AN/ALE-47 safety pin, which inhibits AN/ALE-47 dispenses. Figure 7-25 — AN/ALE-47 countermeasures dispensing system. 7-19 End of Chapter 7 Weapons Systems Review Questions 7-1. What type of homing-missile guidance uses a component inside the missile to illuminate a target? A. B. C. D. 7-2. What type of homing-missile guidance uses directing intelligence received from the target? A. B. C. D. 7-3. AIM-7 Sparrow AIM-9M Sidewinder AIM-120 Advanced Medium-Range Air-to-Air Missile AIM-9X Sidewinder What air-to-air missile offers improved defense against infrared countermeasures? A. B. C. D. 7-6. Active only Semi-active Passive only Active and passive What air-to-air missile provides for an extremely high off-boresight target acquisition window? A. B. C. D. 7-5. Active only Semi-active Passive only Active and passive What type of homing-missile guidance receives target illumination from an external source? A. B. C. D. 7-4. Active only Semi-active Passive only Active and passive AIM-7 Sparrow AIM-9M Sidewinder AIM-120 Advanced Medium Range Air-to-Air Missile AIM-9X Sidewinder What guided bomb unit series are 2,000 pounds and designed to penetrate hard targets? A. B. C. D. 10 12 16 24 7-20 7-7. What air-to-ground missile is designed for close air support and defense suppression? A. B. C. D. 7-8. What air-to-ground missile can be used to target and destroy slow-moving aircraft? A. B. C. D. 7-9. AGM-65 Maverick AIM-9M Sidewinder AGM-88 High Speed Anti-Radiation Missile AGM-114 Hellfire AIM-9M Sidewinder AGM-65 Maverick AGM-88 High Speed Anti-Radiation Missile AGM-114 Hellfire What F/A-18E/F basic armament component disables 28 volts direct current to master arm circuits when in down position? A. B. C. D. Armament system circuit breakers Landing gear control panel Mission computers Armament safety override switch 7-10. What F/A-18E/F basic armament component is located on the nose wheel well maintenance panel? A. B. C. D. Armament safety override switch Armament system circuit breakers Landing gear control panel Mission computers 7-11. What F/A-18E/F basic armament component provides release voltage and weapons/rack/launcher status to the armament computer? A. B. C. D. Landing gear control handle Mission computers Signal data converter control Armament safety override switch 7-12. How many digital data computers in the F/A-18E/F make up the mission computer system? A. B. C. D. One Two Three Four 7-21 7-13. What panel is used to enter weapon-type codes and nose/tail fuze codes into the armament computer? A. B. C. D. Code insertion Landing gear control Master arm control Weapon insertion 7-14. On the F/A-18E/F aircraft, what four-position switch selects the air-to-air weapons loaded? A. B. C. D. CAGE/UNCAGE Air-to-air weapons select Air-to-air missile trigger Air-to-air weapon release 7-15. What switch in the F/A-18E/F is used to control the selected AIM-9M seeker head position? A. B. C. D. CAGE/UNCAGE Air-to-air weapons select Air-to-air missile trigger Air-to-air weapon release 7-16. What type of display in the F/A-18E/F is used to enter the quantity, multiple, and interval of airto ground weapons? A. B. C. D. Digital data Head-up Up-front control Countermeasure 7-17. What system in the F/A-18E/F provides target data for the AIM-7 Sparrow and AIM-120 Advanced Medium Range Air-to-Air Missiles? A. B. C. D. Communications Electronic warfare Navigation Radar 7-18. In the F/A-18E/F, in addition to proximity and delay 1, the electrical fuzing supplies what selected fuzing voltages? A. B. C. D. Instantaneous and delay Instantaneous and delay 2 Instantaneous, delay, and delay 2 Delay and delay 2 7-22 7-19. What light on the P-3 Orion pilot armament control panel warns the pilot of a malfunction in one of the weapon release buffers? A. B. C. D. KILL READY ARM HAZARD MASTER ARM JETTISON 7-20. What P-3 Orion interconnection box contains eight subassemblies that provide circuitry control? A. B. C. D. Port Starboard Forward Aft 7-21. On the P-3 Orion, what panel provides the controls for manual or automatic preset of MK 46, MK 50, and MK 54 torpedoes? A. B. C. D. TORP presetter DIRECTED SEARCH MODE selector Pilot armament control panel Armament control box 7-22. What P-3 Orion component provides the digital communications link between the Harpoon aircraft command launch control and the missile? A. B. C. D. DIRECTED SEARCH MODE selector Armament control box Data processor computer Missile interface box 7-23. How many separate targets can the Maverick missile control system individually identify and track? A. B. C. D. One Two Three Four 7-24. What armament function(s) are disabled by the MH-60R weight-on-wheels switch when the aircraft is on deck? A. B. C. D. Weapon identification Release only Jettison only Release and jettison 7-23 7-25. What MH-60R armament system provides the interface between the weapons/stores and the primary flight/mission computer? A. B. C. D. Data handling system Processing interface units Stores management system Weight-on-wheels switch 7-26. What is the total number of pushbuttons located around the MH-60R mission display? A. B. C. D. 10 12 18 22 7-27. What component of the MH-60R consists of three keyboards and allows the aircrew to interface with the avionics systems? A. B. C. D. Control indicator Mission displays Armament control indicator Processing interface units 7-28. How many sonobuoys is the MH-60R sonobuoy launch system capable of controlling? A. B. C. D. 11 13 15 25 7-24 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. If you have an idea for improving this manual, or if you find an error, a typographical mistake, or an inaccuracy in CNATT manuals, please write or e-mail us, using this form or a photocopy. Be sure to include the exact chapter number, topic, detailed description, and correction, if applicable. Your input will be brought to the attention of the Technical Review Committee. Thank you for your assistance. Write: CNATT Rate Training Manager 230 Chevalier Field Avenue Pensacola, FL 32508 E-mail: Refer to NKO ATO rate training Web page for current contact information. 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CHAPTER 8 COMPUTERS Computers are used in many facets of everyday life. This fact is especially true in the Navy and in aviation. A basic computer can be described as an instrument used to perform mathematical operations, such as addition, subtraction, and so on, at very high speeds. However, computers in today’s world are used for more than mathematical calculations. Computers have ensured the successful advances in military, scientific, and commercial applications. Modern aircraft use advanced computer systems to perform high-level avionics system calculations to ensure the success of the mission. As an aviation electronics technician (AT), you will be tasked to troubleshoot and diagnose computer-related failures. This chapter will provide a basic overview on computers and their relationship to avionics systems. Additionally, the typical mission computer system used in the Fighter/Attack (F/A)-18 series aircraft will be provided as an example. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Describe computer hardware components. 2. Describe computer software. 3. Recognize the functions of a computer. 4. Identify the applications of a computer. 5. Recognize the types of computers. 6. Describe the methods of data transmission. 7. Recognize peripheral avionics systems. 8. Identify the integrated components in a typical mission computer system. BASIC COMPUTERS Many different models and sizes of computers are designed to perform various functions. However, computers are, generally speaking, all functionally the same no matter what size or purpose they are designed to meet. The speed and processing power of a computer is determined by the technology (components) used within the computer. The following paragraphs will provide an overview of basic computers. General Terms Two general terms are used to define the makeup of a basic computer: hardware and software. Hardware The electronic and physical components of a computer are commonly called hardware (Figure 8-1). Examples of computer hardware are microchips, printed circuit Figure 8-1 — Typical computer hardware. 8-1 cards, power supplies, and so on. All basic computers require the following hardware components: • Input device – allows the operator to enter data into a computer system • Output device – displays data and other information • Mass storage device – permanently stores large amounts of data • Memory – temporarily stores data and applications • Central processing unit (CPU) – serves as the main component of the computer system A basic computer block diagram is illustrated in Figure 8-2. Figure 8-2 — Basic computer block diagram. Software Computer software is a set of programs and procedures used by a computer to perform a particular function. Software includes compilers, assemblers, operating systems, and so on. Compiler software is used to transform the source code of one programming language into another computer program language. Assembler software enables developers to access, manage, and alter computer hardware architecture. Operating systems are designed to support a computer’s basic functions, such as running applications or controlling input/output (I/O) devices. Advances in software have led to the development of a wide variety of specialized programming languages such as C++, Java, and many others. Specialized programming languages allow the operator to design and implement applications to solve problems or to meet a specific need. Perhaps the best use of software has been in the area of real-time processing. Real-time processing is a situation where the data is submitted to a computer, and an immediate response is obtained. The capability of an aircraft mission computer to perform real-time processing could determine the success or failure of an assigned mission. Computer Functions All computers can perform the following operations: gather, process, store, disseminate, and display data (Figure 8-3). Figure 8-3 — Basic computer functional diagram. Gather Data A computer must first gather information before it can process the information. A computer can gather data using one or a combination of the following methods: • Manual – information is inputted by an operator either directly or through the use of an external device. The information is stored, disseminated, or displayed depending on the operational program. 8-2 • Automatic – information is received from another system, subsystem, or equipment. The information is either immediately used by the computer or stored for future use. NOTE Many computer systems are designed to use a combination of both methods to gather data. Process Data The processing of data is the main function of a computer system. Other components can collect data for the system, but the computer is going to exclusively process the information. The CPU is the main component in the computer system used to process data. Store Data Computer systems can store information either internally or externally. The computer uses memory to store information internally. In contrast, a number of options can be used to store data externally. For example, information can be transferred to an external hard drive to be archived for later use. Disseminate Data Computer systems use I/O sections to route data to other components such as printers, storage devices, or displays. Display Data Computer systems normally display two general types of data: data related to the mission of the system and information related to the operation of the system. Computers rely on external devices to display the processed information. Computer Application The uses for a computer fall into a large variety of categories that are too numerous to realistically cover in this chapter. Therefore, an overview of some of the common applications of a computer is provided below. Database A computer can be used to index and retrieve information. The information is stored in the computer system under a keyword or heading. When an operator enters that specific keyword or heading, the application calls up the data and displays the information. Simulation Computer systems can be used to simulate the operation of any type of system being designed. Simulations will identify shortfalls and flaws in the new system that can be corrected before building the final product. Business Computers are designed to perform complex calculations at a high speed and accuracy. The ability to perform complex calculations makes a computer the perfect choice for use in business applications. Some examples of the applications of computers in business are accounting, payroll, and customer support. 8-3 Process Control Controlling a process in real-time is another good example of the application of a computer system. When the system detects a change in the process, an immediate corrective action can be initiated. The applications and functions of a computer are virtually endless. Computers enable people to do more than they could do in the past. For example, computations that required years to be calculated by human methods are now accomplished in a matter of moments by a modern computer. Types of Basic Computers In general, there are two basic types of computers: analog and digital. Analog Computers Analog computers (Figure 8-4) are all designed to meet a special purpose. For example, an analog computer can be used to measure continuous electrical or physical conditions, such as current, voltage, flow, temperature, or pressure. The data collected by the Figure 8-4 — Analog computer. analog computer is converted into a related mechanical or electrical quantity. Analog computers can be used to adjust the control of a machine or to manage a process. To accomplish these applications an analog computer must be capable of converting analog data to digital data, process the data, and reverse the conversion process. The applications of analog computers are limited because of their dependence on a physical connection to a device. Digital Computers Digital computers are devices that are used to solve problems by manipulating numerical equivalents of information by using mathematical and logical processes. A typical digital computer may use binary numbers, octal numbers, decimal numbers, etc. as the required numerical equivalent. An electronic digital computer typically uses binary numbers that are expressed as a 0 (OFF) or 1 (ON). The 0 and 1 functions are adjusted within the logic circuits by the voltage value and current applied to the computer hardware. Digital computers are capable of accepting a wide variety of instructions and responding in a specific manner. This process, in general terms, is called programming. Programming is the modification or arrangement of instructions in a predictable manner to a given situation. Digital computers are more versatile than their analog equivalents because they are easily altered to meet changing conditions. There are two basic types of digital computers: special purpose and general purpose. • Special-purpose digital computers (Figure 8-5) are designed to follow a specific set of instruction sequences that are fixed at the time they are manufactured. The actual construction of a special-purpose computer must be changed to alter its operational purpose. • General-purpose digital computers (Figure 8-6) follow instruction sequences that are read into and stored in memory prior to the calculation being performed. This type of computer operation can be altered by inputting a different set of instructions. Since the operation of generalpurpose digital computers can be changed with relative ease, they provide far greater usage flexibility than a special-purpose digital computer. 8-4 Figure 8-6 — General-purpose digital computer. Figure 8-5 — Specialpurpose digital computer. Peripheral Devices A peripheral device (Figure 8-7) is any device that can be connected to a computer for input, output, or communication functions. Peripherals that are under the control of the computer are defined as being online. In contrast, devices that operate independently or are not under direct control of the computer are defined as being offline. The following is a list of some of the common computer peripherals: • Printer • Scanner • Keyboard • Mouse • Monitor • Speakers DATA TRANSMISSION Figure 8-7 — Common computer peripheral devices. Computers use I/O sections to communicate with peripheral devices. Data is transmitted to the computer, processed, and transferred as output. The I/O process is accomplished through the use of electrical or optical cables that carry data and signals to and from the device to the computer. The exchange of data and signals occurs on an I/O channel. There are two general types of I/O channels: simplex and duplex. • Simplex operations occur in one direction only. A device that uses simplex communication would only be able to transmit or receive data, but not both. Because of this characteristic, 8-5 simplex peripheral devices are seldom used because a return path is normally required to control information flow or to generate an error signal. • A duplex channel is capable of both sending and receiving information. There are two types of duplex channels: half-duplex and full-duplex. o Half-duplex – is capable of transmitting and receiving signals but only in one direction at a time o Full-duplex – is capable of simultaneously transmitting and receiving data Figure 8-8 — Types of computer I/O channels. An illustration of the types of I/O channels is shown in Figure 8-8. Digital Data Transmission Methods A number of different methods can be used to receive and transmit digital data. However, this discussion will focus on the three methods that are typically used in Navy aircraft: serial, parallel, and fiber optic. Serial Mode Serial mode uses three wires for transmission: one to transmit data, one to receive data, and one to act as a ground wire. In a serial system, digital data is transmitted one bit at a time using one pair of transmission lines. Serial data transmission can be a good option to use in circumstances where a computer and a peripheral are separated by a long physical distance. Parallel Mode Interaction Available Parallel mode uses a single wire for each bit of information that will be transmitted or received. The data is transmitted via the wires simultaneously. Based on this fact, it would require six wires to transfer six bits of information using the parallel mode of transmission. The serial and parallel modes of transmission are illustrated in Figure 8-9. Figure 8-9 — Digital transmission modes. 8-6 Fiber Optic Fiber optic systems transmit light photons through a specially designed glass medium to send and receive digital information. The light photons in a fiber optic system are created by either a light emitting diode (LED) or a laser diode. There are three basics functions of a fiber optic data link: • To convert an electrical input into an optical signal • To transmit the optical signal over an optic fiber • To convert the optic signal back into an electrical signal A typical fiber optic system uses four main components: transmitter, optical fiber, connectors/splices, and receiver. • Transmitter – coverts the electrical signal into an optical signal and sends it through the optical fiber cabling. Fiber optic transmitters in aircraft are normally embedded into Weapons Replaceable Assemblies (WRAs). The photo-emitters in the fiber optic transmitter are chosen specifically to meet an application. The primary differences in the photo-emitters include the type (laser or LED), infrared (IR) wavelength, output power, and optical launch. Optical launch describes the transmitter’s ability to launch the light photons down the fiber optic cabling. • Optical fiber – is a three-part structure that includes a core, cladding, and a coating. The optical transport layer of a fiber optic cable is made up of a glass strand that consists of a core region surrounded by a cladding region. The protective layer in aircraft fiber optic cables is typically a polyimide coating that is 10- to 20-micrometers thick. • Connectors/Splices – are used to physically connect the optical fiber cable to the transmitter and receiver sections of the data link. The most common connector used in aircraft fiber optic systems is the military specification (MIL)-DTL-38999 series-III connector (Figure 8-10). The MIL-DTL-38999 series-III connector is compatible with both electronic and fiber optic pins and sockets. Figure 8-10 — MIL-DTL-38999 series-III fiber optic connector. Figure 8-11 — Light transmission through a fiber optic cable. 8-7 Interaction Available • Receiver – converts the optical signal into an electrical signal and routes the signal to the appropriate equipment for processing. Fiber optic receivers, like transmitters, are embedded into WRAs. The photodetectors in an aircraft fiber optic system are also chosen to meet the specific application. The photodetectors vary by size and sensitivity to the IR wavelength (near IR to mid IR). The transmission path of light through a fiber optic cable is illustrated in Figure 8-11. A typical fiber optic system incorporates all of the above components into one unit that is called a transceiver. Fiber optic systems in aircraft are designed to be more rugged than fiber optic systems on land. Aircraft fiber optic cables are normally 300 feet or less, contain less than five cables, and may be incorporated with other aircraft wiring systems. Fiber optic data systems are progressively being used to replace traditional electrical data transmission systems in aircraft. PERIPHERAL AVIONICS SYSTEMS The aircraft computer is the most important avionics system component used to ensure the assigned mission is completed successfully. However, the success of the computer depends upon the interface with external sensors or other avionics systems. The quality of the input data from the peripheral systems to the computer determines the quality of the output from the computer. The following paragraphs will provide an overview of some of the typical avionics systems that interface with the aircraft computer system. The systems are as follows: navigation, radio detection and ranging (radar), weapons, and data link. Navigation Navigation systems are designed to constantly update the operator with the current position of the aircraft in space. Measuring equipment is used to gather navigational data such as station reference points and geographic location. The navigational data is routed to the aircraft computer system where it is compared, processed, and outputted out to other systems. Examples of the general classifications of navigation systems are as follows: • Global positioning • Inertial navigation • Tactical air navigation • Automatic direction finder Radar Radar systems are designed to provide the operator with enhanced situational awareness. A typical radar system can determine whether a target is moving, stationary, a land mass, an aircraft, and other situational data. The radar system maintains communication with the aircraft computer system to provide the operator with a steady flow of real-time information. Examples of the general classifications of radar systems are as follows: • Search • Intercept • Fire control • Navigation • Airborne early warning • Antisubmarine warfare Weapons Many of the advanced weapons employed today require detailed target information before being fired or released from an aircraft. The detailed information is provided to the weapons via the aircraft computer system and associated peripheral armament components. The use of computer systems 8-8 has significantly increased the chances of successfully destroying or disabling a target the first time. Examples of the general classifications of weapons systems are as follows: • Precision bombs • Guided missiles • Antisubmarine warfare Data Link Modern aircraft use complex avionics equipment that is capable of providing the operator with realtime tactical information. The real-time information is received from outside sources via a data link system and is processed by the aircraft computer and peripheral equipment. The real-time information can provide the operator with a distinct tactical advantage while on an assigned mission. Examples of the general classifications of data link systems are as follows: • Multifunctional information distribution • Instrument landing • Navigation F/A-18 MISSION COMPUTER SYSTEM The F/A-18 Hornet mission computer system is the heart of the aircraft and will be used as an example of peripheral avionics systems interface. The mission computer system oversees the control of aircraft subsystems, which, in turn, greatly increases the ability to accomplish a mission. The following paragraphs will provide an overview of a typical mission computer system installed in the F/A-18 Hornet series aircraft. The mission computer system enables the following processes: • Computes and controls the displays sent to the multi-purpose display system • Computes and produces missile launch and weapons release commands • Provides mode control and option select output for various avionics systems • Provides mode control and option select output from the multi-purpose display group to avionics systems for control and computation • Outputs built-in-test (BIT) initiate signals to various avionics systems and monitors the status System Components The F/A-18 mission computer system consists of the following components: • Digital data computer no. 1 (Figure 8-12) • Digital data computer no. 2 (Figure 8-12) • Control-convertor • Electronic equipment control • Mission computer (MC)/hydraulic isolation Figure 8-12 — Digital data computer. 8-9 (HYD ISOL) control panel assembly • Right mux bus impedance matching network • Left mux bus impedance matching network Digital Data Computers The two digital data computers (mission computers) are generalpurpose computers with core memory. A typical computer core memory consists of tiny doughnut-shaped rings that are made out of ferrite (iron) and Figure 8-13 — Typical aircraft mux bus system wiring. are strung on a grid of very thin wires. The digital data computers communicate with other avionics equipment by using six independent avionics multiplex channels. Each channel consists of two independent “X” and “Y” buses. The wiring used in a typical aircraft mux bus system is illustrated in Figure 8-13. The “X” bus is the primary bus and is used to communicate with all equipment on that particular avionics mux channel. If there is an equipment communication failure on the “X” bus, all communications are switched to the “Y” bus. The redundancy is the same with the avionics equipment on the “Y” bus. The digital data computers communicate with equipment not on the mux bus network through the control-convertor. If one of the digital data computers fails for any reason, the other automatically defaults to control the aircraft navigation functions. Both digital data computer systems use 115 volts alternating current (vac), 400 hertz (Hz), and 3phase power to operate. The power is provided via the aircraft electrical or ground power systems. Both digital data computers have internal self-protection modules installed to protect the computer hardware during input power failures. Both digital data computers are divided into four functional subsystems, which enable the control of the operations between the aircraft avionics systems. The four functional subsystems of the digital data computer are as follows: • Processor – is configured with two modules that are further divided into seven sections • Memory – contains the main data storage for the computers through the use of two core memory modules • I/O – contains six independent channels to process both inputs and outputs • Power conversion – is used to convert 115 vac into direct current (dc) power used by the digital data computer modules Both digital data computers are installed with specific software suites that control various mission functions of the aircraft. The following is a basic overview of the software suites installed in each digital data computer. Digital data computer no. 1 has software installed that controls the following: • Navigation • Navigation head-up display • Engine monitor • Avionics BIT • Data link 8-10 • Navigation controls and displays (Figure 814) • Inflight monitor and recording • Non-avionics BIT • Support controls and displays • Display format manager • Math subroutines • Test support and monitoring • Instrumentation support and monitoring Digital data computer no. 2 has software installed that controls the following: • Air-to-air weapons • Weapon delivery head-up display • Air-to-ground weapons • Tactical controls and displays (Figure 8-15) • Display format manager • Self-test • Math subroutines • Test support and monitoring • Instrumentation support and monitoring Figure 8-14 — Typical navigation display. Control-Convertor The control-convertor is the interface unit between the following components: • Electronic equipment control • Digital computers no. 1 and no. 2 • Non-mux avionics systems The control-convertor contains a central processing unit and a fixed software program, which is controlled by the digital computers or the electronic equipment control. The control-convertor sends option, scratch pad (input display), and communication display outputs to the electronic equipment control in response to commands. Commands transmitted from the electronic equipment control or the digital computers are decoded by the control-convertor for non-mux capable avionics system control. The inputs received from the digital computer are reformatted 8-11 Figure 8-15 — Typical tactical weapons delivery status display. and supplied to non-mux capable equipment as control-convertor outputs. The following signals are reformatted and transmitted over the avionics mux bus by the control-convertor: • Synchro • Analog • Discrete • Status • Digital inputs Electronic Equipment Control The electronic equipment control (Figure 8-16) contains the switches and display functions required to control the following systems: • Communication • Navigation • Identification The electronic equipment control also provides for the manual entry of program data and option selection. The systems enabled by the function select switch are as follows: • Electronic flight control • Identification friend or foe (IFF) • Tactical air navigation • Instrument landing • Data link • Radar beacon Figure 8-16 — Typical electronic equipment control. The selected system is turned on and off via the ON/OFF switch on the electronic equipment control. When the system is activated, the status is displayed on the electronic equipment control by two alphanumeric characters. There are five preset options and a four-character alphanumeric display associated with each selected system. The control and power for the electronic equipment control is provided by the control-convertor. The electronic equipment control also provides for the selection of voice communication channels and volume controls. MC/HYD ISOL Control Panel Assembly The MC switch on the panel assembly has three-positions and is electrically latched in either positon other than center. Power is removed from digital data computer no. 1 when the switch is placed in the 1 OFF position. Further, power is removed from digital data computer no. 2 when the switched is placed in the 2 OFF position. In the normal (NORM) position, power is applied to both digital data computers. Right and Left Mux Bus Impedance Matching Networks The mux bus impedance matching networks are used to terminate the six dual bus avionics mux channels in their characteristic impedance. 8-12 Mission Computer System Interface Digital data computers no. 1 and no. 2 use six avionics mux channels, the control-convertor channel, and the electronic equipment control interface to receive input and supply output data to avionics components. Avionics Mux Channel 1 Avionics mux channel 1interfaces with the following components: • Air data computer • Armament computer • High-Speed Anti-Radiation Missile (HARM) command launch computer • Control-convertor • Left digital display indicator • Communication (COMM) no. 1 receiver-transmitter • COMM no. 2 receiver-transmitter • Flight control computer (FCC) A • FCC B • Signal data computer • Signal data recorder • Aircraft instrumentation internal subsystem Avionics Mux Channel 2 Avionics mux channel 2 interfaces with the following components: • Computer-power supply • Controller-processor • Inertial navigation group • Data link system receiver-transmitter-processor • Right digital display indicator • Electronic countermeasures computer • Advanced Targeting Forward Looking Infrared (ATFLIR) pod • Aircraft instrumentation internal subsystem Avionics Mux Channel 3 Avionics mux channel 3 is used to interface and provide a direct communication line between digital data computer no. 1 and digital data computer no. 2. Avionics Mux Channel 4 Avionics mux channel 4 provides the interface to digital data computers no. 1 and no. 2 for the mission data loader system. The mission data loader system allows the operator to automatically populate mission-specific data into both digital data computers. For example, an operator can 8-13 configure all of the mission-specific radio frequencies onto a mission card that will load that information into the digital data computers. Avionics Mux Channel 5 Avionics mux channel 5 provides a communication path between digital computer no. 1, digital computer no. 2, right digital display indicator, and the aircraft instrumentation internal subsystem. Avionics Mux Channel 6 Avionics mux channel 6 provides a communication path between digital data computer no. 1, digital data computer no. 2, left digital display indicator, and the digital map computer. Control-Convertor Channel The following components are interfaced through the control-convertor channel: • Embedded global positioning system (GPS)/inertial navigation system (INS) • Engine monitor indicator • Left hand (LH) advisory and threat warning indicator panel • Caution light indicator panel • Instrument landing system pulse decoder • Intercommunication amplifier-control • Antenna selector • Electronic equipment control • Head-up display unit • IFF receiver-transmitter • Lock/Shoot light assembly • IFF computer-transponder • Automatic direction finder system • Interference blanker • Attitude reference indicator • Radar beacon receiver-transmitter • Radar beacon receiver • Electronic altimeter height indicator • Electronic altimeter receiver-transmitter • Digital data computers no. 1 and no. 2 • COMM 1 and COMM 2 receiver-transmitter 8-14 Electronic Equipment Control Interface The electronic equipment control receives input data and supplies output data to the following components: • Control-convertor • Antenna selector • IFF system receiver-transmitter • Cockpit electric light control • Intercommunication amplifier-control A block diagram of the mission computer system and the six avionics mux channels is shown in Figure 8-17. Figure 8-17 — Mission computer system and avionics mux channels block diagram. 8-15 End of Chapter 8 Computers Review Questions 8-1. The speed and processing power of a computer is determined by what internal characteristic? A. B. C. D. 8-2. What hardware component allows the operator to enter data into the system? A. B. C. D. 8-3. Memory Output device Input device Central processing unit What type of software application processing could determine the success or failure of a mission? A. B. C. D. 8-6. Memory Output device Input device Central processing unit What hardware component is the most important part of the computer system? A. B. C. D. 8-5. Memory Output device Input device Central processing unit What hardware component temporarily stores data and applications? A. B. C. D. 8-4. Size Power Scope Components Static Arithmetic Real-time Read-only What component does a computer use to store information internally? A. B. C. D. Input Output Memory Processor 8-16 8-7. C++ and Java are examples of what type of programming language? A. B. C. D. 8-8. What type of software is used to transform the source code of a programming language? A. B. C. D. 8-9. Localized Specialized Generalized Randomized Compiler Assembler Application Operating system What type of software is used to support a computer’s basic functions? A. B. C. D. Compiler Assembler Application Operating system 8-10. Other than manual, what method can a computer use to gather data? A. B. C. D. Logical Automatic External Semi-automatic 8-11. What is the main function of a computer? A. B. C. D. Process data Gather data Display data Disseminate data 8-12. What computer function involves the routing of data to external components? A. B. C. D. Process data Gather data Display data Disseminate data 8-13. What computer function is dependent on the use of peripheral devices? A. B. C. D. Process data Gather data Display data Disseminate data 8-17 8-14. What computer function occurs first? A. B. C. D. Process data Gather data Display data Disseminate data 8-15. What application of a computer is used to index and retrieve information? A. B. C. D. Business Database Simulation Process control 8-16. Design and testing of a system occurs using what application of a computer? A. B. C. D. Business Database Simulation Process control 8-17. The ability to perform high-speed and accurate calculations is most suitable for which of the following applications? A. B. C. D. Business Database Simulation Process control 8-18. When a deficiency is encountered, what application of a computer enables the initiation of an immediate corrective action? A. B. C. D. Business Database Simulation Process control 8-19. The two basic types of computers are analog and what other type? A. B. C. D. Mission Digital Desktop Electrical 8-18 8-20. Other than mechanical, the data collected by an analog computer is converted into what type of quantity? A. B. C. D. Sound Electrical Pressure Temperature 8-21. Binary code uses what set to represent an ON and OFF signal respectively? A. B. C. D. 0 and 0 0 and 1 1 and 0 1 and 1 8-22. What term is used to describe the modifying of computer instructions based on a situation? A. B. C. D. Operating Manipulating Disseminating Programming 8-23. Binary code in computer hardware is adjusted by current and what other value? A. B. C. D. Time Voltage Quotient Numerical operator 8-24. The operation of what type of digital computer can be easily changed? A. B. C. D. All-purpose Multi-purpose General-purpose Special-purpose 8-25. Printers and keyboards are examples of what types of devices? A. B. C. D. Internal Peripheral Dependent Independent 8-26. A device using what type of data transmission will only be able to either receive or transmit? A. B. C. D. Simplex Duplex Full-duplex Half-duplex 8-19 8-27. A device using what type of data transmission can send and receive data at the same time? A. B. C. D. Simplex Multiplex Full-duplex Half-duplex 8-28. A device using what type of data transmission can transmit and receive signals, but in only one direction at a time? A. B. C. D. Simplex Duplex Full-duplex Half-duplex 8-29. Data is transmitted one bit at a time using what mode of digital transmission? A. B. C. D. Serial Parallel Fiber optic Series-parallel 8-30. Data is transmitted simultaneously using what mode of digital transmission? A. B. C. D. Serial Parallel Fiber optic Series-parallel 8-31. Other than a laser diode, what type of diode can be used to generate photons in a fiber optic system? A. B. C. D. Gunn Zener Avalanche Light-emitting 8-32. Fiber optic data link systems convert an electrical signal into what type of signal? A. B. C. D. Visual Optical Acoustical Mechanical 8-33. The protective layer of a fiber optic cable is typically how many micrometers thick? A. B. C. D. 10 to 20 20 to 30 30 to 40 40 to 50 8-20 8-34. Automatic direction finders are an example of what type of peripheral avionics system? A. B. C. D. Radar Weapons Navigation Data link 8-35. Radar systems provide the operator with what type of awareness? A. B. C. D. Tactical Situational Operational Environmental 8-36. The F/A-18 mission digital data computers use what type of memory? A. B. C. D. Core Logical Volatile Non-volatile 8-37. Each digital data computer multiplex channel consists of how many buses? A. B. C. D. One Two Three Four 8-38. If one digital data computer fails, the other will default to what mode of operation? A. B. C. D. Radar Weapon Navigation Communication 8-39. The F/A-18 digital data computer is divided into how many functional subsystems? A. B. C. D. Three Four Five Six 8-40. What avionics mux channel is reserved for digital computer-to-computer communication? A. B. C. D. 1 2 3 4 8-21 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. 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CHAPTER 9 AUTOMATIC CARRIER LANDING SYSTEM/INSTRUMENT LANDING SYSTEM One of the most demanding tasks facing aircrew is landing an aircraft onto an aircraft carrier. The Automatic Carrier Landing System (ACLS) and Instrument Landing System (ILS) are great aids to the aircrew to accomplish this task. In the fleet, aviation electronics technicians (ATs) routinely troubleshoot discrepancies with the ACLS and ILS. Therefore, basic knowledge of the systems and the carrier landing process is vital to the successful diagnosis and repair of the system. This chapter will provide an overview of basic aerodynamics, ACLS carrier systems, ACLS aircraft systems, and the ILS. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Recognize the basic forces that affect flight. 2. Recognize the components used in the ACLS. 3. Describe the operating principles of the ACLS. 4. Describe the aircraft carrier landing sequence. AIRFOIL An airfoil is defined as that part of an aircraft that produces lift or any other desirable aerodynamic effect as it passes through the air. The wings and the propeller blades of a fixed-wing aircraft and the rotor blades of a helicopter are examples of airfoils. Airfoil Terminology The shape of an airfoil and its relationship to the airstream are important. The following are some of the common terms that are used to describe airfoils. • The leading edge is the front edge or surface of the airfoil (Figure 9-1). • The trailing edge is the rear edge or surface of the airfoil (Figure 9-1). • The chord line is an imaginary straight line from the leading edge to the trailing edge of an airfoil (Figure 9-1). • The camber is the curve or departure from a straight line (chord line) from the leading edge to the trailing edge of the airfoil (Figure 9-1). Figure 9-1 — Airfoil terminology. 9-1 • Relative wind is the direction of the airstream in relation to the airfoil (Figure 92). • Angle-of-attack (AOA) is the angle between the chord line and the relative wind (Figure 9-2). FORCES AFFECTING FLIGHT Figure 9-2 — AOA. An aircraft in flight is in the center of a continuous battle of forces. The conflict of these forces is the key to all maneuvers performed in the air. There is nothing mysterious about these forces because they are definite and known. The direction in which each of the forces acts can be calculated. The aircraft is designed to take advantage of each force. These forces are lift, weight, thrust, and drag. Lift Lift is the force that acts in an upward direction to support the aircraft in the air. Lift counteracts the effects of weight and must be greater than or equal to weight if flight is to be sustained. Weight Weight is the force of gravity acting downward on the aircraft and everything in the aircraft, such as crew, fuel, and cargo. Thrust Thrust is the force developed by the aircraft's engine. Thrust acts in the forward direction and must be greater than or equal to the effects of drag for flight to begin or to be sustained. Drag Drag is the force that tends to hold an aircraft back. Drag is caused by the disruption of the airflow about the wings, fuselage, and all protruding objects on the aircraft. Drag resists motion as it acts parallel and in the opposite direction in relation to the relative wind. The direction in which these forces act in relation to the aircraft is shown in Figure 9-3. Figure 9-3 — Forces affecting flight. ROTATIONAL AXES Any vehicle, such as a ship, a car, or an aircraft, is capable of making three primary movements (roll, pitch, and yaw). The vehicle has three rotational axes that are perpendicular (90 degrees) to each other. The axes are referred to by their direction: longitudinal, lateral, and vertical. 9-2 Longitudinal Axis The longitudinal axis is the pivot point about which an aircraft rolls. The movement associated with roll is best described as the movement of the wing tips (one up and the other down). The longitudinal axis runs fore and aft through the length (nose to tail) of the aircraft. This axis is parallel to the primary direction of the aircraft. The primary direction of a fixed-wing aircraft is always forward. The roll axis is shown in Figure 9-4, View A. Interaction Available Vertical Axis The vertical axis runs from the top to the bottom of an aircraft. The vertical axis runs perpendicular to both the roll and pitch axes. The movement associated with the vertical axis is yaw. Yaw is best described as the change in aircraft heading to the right or left of the primary direction of an aircraft. The yaw axis is shown in Figure 9-4, View B. Lateral Axis The lateral axis is the pivot point about which the aircraft pitches. Pitch can best be described as the up and down motion of the nose of the aircraft. The pitch axis runs from the left to the right of the aircraft (wingtip to wingtip). The pitch axis is perpendicular to and intersects the roll axis and is shown in Figure 9-4, View C. AUTOMATIC CARRIER LANDING SYSTEM COMPONENTS Figure 9-4 — Motion about the axes. The ACLS consists of multiple components installed in the aircraft and systems located onboard an aircraft carrier. The following paragraphs will provide an overview of both the typical ACLS aircraft carrier and aircraft components and systems. Aircraft Carrier Automatic Carrier Landing System Components Aircraft carriers are equipped with two radar systems that provide landing aircraft with critical information and guidance during the landing cycle. There are the SPN-41 Instrument Carrier Landing System (ICLS) and the SPN-46(V)3 Precision Approach Landing System (PALS). SPN-41 Instrument Carrier Landing System The ICLS radar transmits the glidepath pulse-coded under the K frequency band (Ku) information from the aircraft carrier to the aircraft. The ICLS is located on the carrier and uses two antennas. One antenna is used to transmit azimuth information, and the other transmits elevation information. Both signals are processed by the receiver-decoder group on the aircraft. 9-3 SPN-46(V)3 Precision Approach Landing System The PALS (Figure 9-5) was designed to be an automatic landing system but it has the capability to operate in manual modes. The PALS uses two modes to receive and transmit data: display and voice. The PALS operates in three modes: mode I, mode II, and mode III. • Mode I is the automatic control mode of operation. The PALS transmits command and error signals to the aircraft via the aircraft data link system. The approaching aircraft receives command and error signals and automatically corrects the approach to remain in the narrow flight envelope. • Mode II is a manual control mode with information relayed to aircraft displays. The operator is provided with cockpit visual indications of command and error signals relayed by the PALS. • Figure 9-5 — SPN-46(V)3 PALS antenna. Mode III is a manual control mode with voice communications. The PALS provides a voice link for ship-to-aircraft voice communications to provide talkdown guidance. Aircraft Automatic Carrier Landing System Components Aircraft ACLS systems do not use one system or one component. The aircraft ACLS is an integration of multiple aircraft systems that work together to guide the aircraft safely to a carrier landing. The following paragraphs will describe a typical aircraft ACLS system and its components. Instrument Landing System The ILS (Figure 9-6) provides the data for visual steering commands that assist the aircrew for the last 25 miles before carrier touchdown. The ILS interacts with the ICLS and decodes the azimuth and elevation signals. The decoded signals are provided to the aircrew via the head-up display (HUD) and the standby attitude reference indicator (ARI). The ILS consists of the following components: radio receiver, pulse-decoder, Ku-band antenna, and Ku-band waveguide assembly. • The radio receiver mixes, detects, and amplifies azimuth and elevation microwave signals from the ICLS to provide a coded-pulse train to the pulse-decoder. Figure 9-6 — Typical instrument landing aircraft-toaircraft-carrier communication. 9-4 • The pulse-decoder receives and decodes the coded-pulse train and uses the signal to route the elevation and azimuth errors to the HUD and ARI. • The Ku-band antenna receives the Ku-band azimuth and elevation signals transmitted from the ICLS. • The Ku-band waveguide assembly provides the path to route the azimuth and elevation signals from the Ku-band antenna to the radio receiver. Standby Attitude Reference Indicator A typical standby ARI (Figure 9-7) is designed to assist the aircrew in determining the attitude of the aircraft in instances where the natural horizon is not visible. A typical standby ARI uses a miniature representation of an aircraft that represents the nose (pitch) and wing (bank) attitude. The bank pointer on the indicator face shows the degree of aircraft bank in the following manner: • 10-degree increments up to 30 degrees • 30-degree increments up to 90 degrees The upper half of the indicator is a light color that represents the sky. The bottom half of the indicator is a dark color that is used to represent the ground. Calibration marks on the sphere are used to represent the pitch of the aircraft in 5- to 10-degree increments. Every attitude reference indicator consists of a control to adjust the pitch trim adjustment or a pull-to-cage knob which the operator uses to center the artificial horizon as necessary. Figure 9-7 — Typical standby attitude reference indicator. The standby ARI automatically displays ILS steering when the ILS system is turned on by the operator. The ILS steering cues use the miniature representation of the aircraft as a reference. The horizontal needle indicates an ILS approach that is above or below the glideslope. The vertical needle indicates an ILS approach that is left or right of the glideslope. The aircraft is at the optimal approach conditions when the horizontal and vertical needles are centered on the standby ARI. A typical standby ARI uses pitch and roll information obtained via the aircraft inertial navigation system. The sphere inside the standby ARI is gimbal-mounted and capable of 360 degree rotation. Automatic Flight Control System A typical automatic flight control system (AFCS) is made up of a number of components and systems. A typical AFCS is used to provide the interface between the correction signals received from the data link and the aircraft flight control surfaces. The AFCS provides switching and signal conditioning, engage logic, command signal limiting, and failsafe interlocks. The failsafe interlocks are required to couple and process data link signals to the pitch and bank channels of the AFCS. Automatic synchronization is provided in all three axes. 9-5 Automatic Throttle Control Similar to the AFCS, the automatic throttle control (ATC) system encompasses a number of different components and subsystems. The ATC system is used during the landing sequence to maintain the appropriate AOA by electrically adjusting the output power of the engines. The ATC also manipulates the engine controls to keep the aircraft traveling at a constant rate of airspeed. Head-up Display The aircraft HUD displays the same cues as the standby ARI but in a digital format. The ILS steering cues on the HUD are referenced to velocity vector (center of the display) and the artificial horizon. The elevation deviation bar (Figure 9-8) indicates an ILS approach that is above or below the glideslope. The azimuth deviation bar (Figure 9-8) indicates an ILS approach left or right of the glideslope. The aircraft is at the optimum approach conditions when both the elevation and azimuth bar are centered within the velocity vector and the artificial horizon. Receiving-Decoding Group A typical receiving-decoding group converts the Figure 9-8 — HUD ILS steering display. glidepath error signals received from the ship’s ICLS and converts the signals into visual indications for the operator. The receiving-decoding group is also used for the airborne monitoring of ACLS mode I and mode II aircraft carrier approaches. Radar Beacon The radar beacon has two modes of operation: normal and automatic carrier landing (ACL). The normal mode is used to extend the range of the surface tracking radar. When in the ACL mode the radar beacon receives conically scanned above the K frequency band (Ka) signals from the SPN-46 radar system. The signals are used to derive the range, angle tracking, and position error for aircraft data link guidance. There are five components to the radar beacon system: • The radar receiver is used during both the normal and ACL modes. The radar receiver detects when the aircraft is out of position. The radar receiver produces an amplitude modulated (AM) envelope called spin error. The amplitude of the spin error is directly proportional to the amount of position error. The spin error signal is then applied to the radar receiver-transmitter. • The radar receiver-transmitter (Figure 9-9) receives the X-band signals that are transmitted by the SPN-46 PALS. The main purpose of the radar receiver-transmitter is to improve the aircraft tracking while operating in the ACL mode. When the radar receiver9-6 Figure 9-9 — Radar beacon receivertransmitter. transmitter receives the spin error signal from the radar receiver it produces X-band reply signals. The SPN-46 PALS additionally uses the X-band replies for aircraft angle tracking and range information. • The Ka-band antenna receives the Ka frequency band signals and routes the signals to the radar receiver. • The X-band antenna receives the X-band signals and routes the signals to the radar receivertransmitter. • The Ka-band coaxial cable and waveguide assembly is used to route the received Ka-band signals to the radar receiver. Angle-of-Attack Indexer The AOA indexer is located on the left hand side of the HUD in the Fighter/Attack (F/A)-18 series aircraft. The AOA indexer uses lighted symbols to visually indicate the aircraft AOA. AUTOMATIC CARRIER LANDING SYSTEM OPERATION The all-weather combination AFCS and ACLS provides the automatic, semiautomatic, or manual operation for aircraft carrier landings with minimum use of airborne electronic subsystems. The aircraft control commands are generated by shipboard computers so that the necessary pitch and bank signals can be transmitted to the aircraft AFCS via the one-way data link system. This closedloop operation between aircraft and aircraft carrier can provide the aircraft with automatic control from approach to touchdown. The ACLS is the final approach and landing medium for carrier-based aircraft during daylight or darkness, severe weather and sea states, and in low ceiling and low visibility conditions. There are three selectable modes of operation for the ACLS: mode I, mode II, and, mode III. • Mode I is a fully automatic approach from entry point to touchdown on the flight deck. • Mode II requires manual control of the aircraft. In this mode, the aircrew controls the aircraft by observing the crew station displays. • Mode III is manual aircrew control with talkdown guidance by a shipboard controller that provides verbal information for aircrew control to visual minimums. NOTE The operator can use full mode I capability with mode II and mode III as backups. Landing Sequence The following paragraphs will provide an overview of the mode I landing sequence. The landing sequence (Figure 9-10) begins when the aircraft is at the marshaling point under control of the Carrier Air Traffic Control Center (CATCC). The sequence has two phases: approach and descent. • Approach consists of the flight of the aircraft from the marshaling point to the radar acquisition window. • Descent consists of the flight of the aircraft from the radar acquisition window until landing on the aircraft carrier flight deck. 9-7 The transition from the approach phase to the descent phase is accomplished with minimal crew station switching operations. The minimal switching operations are intended to reduce the task loading during the landing sequence. Mode I Landing Operation The aircraft is held at a marshalling point by CATCC, before transitioning into a mode I landing approach. The aircraft will remain at the marshal point until CATCC has determined the landing priorities. When the aircraft is selected to begin its approach, CATCC assigns a data link channel, which is entered into the aircraft data link system by the aircrew. The aircrew is cleared for approach to the aircraft carrier when the landing check (LDG CHK) indicator illuminates in the crew station of the aircraft. At this point in the sequence the Figure 9-10 — Carrier landing sequence. operator ensures all required mode I landing systems are in the correct mode of operation. The aircraft then begins the initial descent towards the aircraft carrier. When the aircraft passes the acquisition radar window (approximately 4 miles astern of the aircraft carrier) the ACL ready (ACL RDY) indicator will illuminate in the crew station. The PALS system begins to transmit lateral and vertical error signals after the aircraft passes the acquisition radar system window. The lateral and vertical signals represent the actual position of the aircraft in comparison to the approach path to the aircraft carrier. Next, the PALS transmits a COUPLE discrete signal to the aircraft. The COUPLE discrete signal indicates that the AFCS system is being provided with pitch and roll commands. The pitch and roll commands are transmitted by the AFCS to the aircraft control surfaces. The aircrew places the aircraft into landing configuration and ensures the aircraft is within aircraft carrier landing approach parameters. The ICLS sends a 10 second discrete message (10 SEC) when the aircraft is approximately 12 seconds away from landing on the aircraft carrier flight deck. The 10 SEC discrete message informs the operator that the motion of the flight deck is being added to the glideslope commands. The ICLS freezes the transmission of compensation messages when the aircraft is approximately 1.5 seconds from touchdown. At the same time, the AFCS in combination with the ATC holds the aircraft altitude. Safety Provisions The ACLS was designed with the safety of the aircrew and aircraft as a core component. The ACLS uses the following provisions to ensure safety: 9-8 • The ICLS uses an independent monitoring link to ensure the aircraft is within a safe glidepath position. Additionally, the monitoring link allows the operator to monitor the position of the aircraft in relation to the transmitted glidepath. • The COUPLE discrete message transfer is terminated any time the aircraft exceeds the control envelope. The operator can continue the landing approach to the aircraft carrier but only in ACLS modes II or III. If at any point during the coupled landing sequence the aircraft requires a large maneuver to get back on course and into the flightpath, an automatic WAVEOFF signal is generated. The automatic WAVEOFF signal automatically disengages the aircraft ACLS to allow the operator to execute the waveoff maneuver. The ACLS mode I approach is illustrated in Figure 9-11. Figure 9-11 — ACLS mode I approach. 9-9 End of Chapter 9 Automatic Carrier Landing System/Instrument Landing System Review Questions 9-1. Which of the following terms describe the part of an aircraft that produces lift as it passes through the air? A. B. C. D. 9-2. What term describes an imaginary line from the leading edge to the trailing edge of an airfoil? A. B. C. D. 9-3. Camber Chord line Trailing edge Leading edge What force is defined as gravity acting downward on an aircraft? A. B. C. D. 9-6. Camber Chord line Trailing edge Leading edge What term describes the curve from the leading edge to the trailing edge of an airfoil? A. B. C. D. 9-5. Camber Chord line Rotational Longitudinal What term describes the front edge of an airfoil? A. B. C. D. 9-4. Airfoil Engines Fuselage Landing gear Lift Drag Thrust Weight What force is developed by an aircraft’s engine? A. B. C. D. Lift Drag Thrust Weight 9-10 9-7. What force has the tendency to hold an aircraft back? A. B. C. D. 9-8. What force acts in an upward direction to support an aircraft in the air? A. B. C. D. 9-9. Lift Drag Thrust Weight Lift Drag Thrust Weight What rotational axis runs from the top to the bottom of an aircraft? A. B. C. D. Lateral Vertical Diagonal Longitudinal 9-10. What rotational axis is the pivot point around which an aircraft pitches? A. B. C. D. Lateral Vertical Diagonal Longitudinal 9-11. What rotational axis is the pivot point around which the aircraft rolls? A. B. C. D. Lateral Vertical Diagonal Longitudinal 9-12. What frequency band does the SPN-41 radar use to transmit information to an aircraft? A. B. C. D. K X K-over K-under 9-13. The precision approach landing system has how many modes of operation? A. B. C. D. Two Three Four Five 9-11 9-14. What modes can the precision approach landing system use to receive and transmit data? A. B. C. D. Analog and digital Input and output Display and voice Electrical and mechanical 9-15. What system provides the data for visual steering commands at about 25 miles away from the aircraft carrier? A. B. C. D. Weapons Communication Global positioning Instrument landing 9-16. What does the upper half of a typical attitude reference indicator represent? A. B. C. D. Sky Ground Bank Pitch 9-17. Calibration marks on a typical attitude reference indicator represents aircraft pitch in increments of how many degrees? A. B. C. D. 5 to 10 5 to 20 5 to 30 5 to 40 9-18. What system provides the interface between data link signals and aircraft control surfaces? A. B. C. D. Radar beacon Automatic throttle Receiving-decoding Automatic flight control 9-19. What system is used to keep the aircraft traveling at a constant speed? A. B. C. D. Radar beacon Automatic throttle Receiving-decoding Automatic flight control 9-20. What radar beacon component detects when the aircraft is out of position? A. B. C. D. Receiver Antenna Receiver-transmitter Coaxial cable 9-12 9-21. How many selectable modes are in an automatic carrier landing system? A. B. C. D. Two Three Four Five 9-22. What are the two phases in the aircraft carrier landing sequence? A. B. C. D. Marshal and descent Marshal and approach Transition and approach Approach and descent 9-23. The aircrew will begin the approach to the aircraft carrier when what indicator illuminates? A. B. C. D. COUPLE WAVEOFF LDG CHK AUTOMATIC CARRIER LANDING 9-24. The acquisition radar window is approximately how many miles astern of the aircraft carrier? A. B. C. D. 3 4 5 6 9-25. What signal is generated when an aircraft requires a large maneuver to get back into the safe glideslope? A. B. C. D. COUPLE WAVEOFF LDG CHK AUTOMATIC CARRIER LANDING 9-13 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. If you have an idea for improving this manual, or if you find an error, a typographical mistake, or an inaccuracy in CNATT manuals, please write or e-mail us, using this form or a photocopy. Be sure to include the exact chapter number, topic, detailed description, and correction, if applicable. Your input will be brought to the attention of the Technical Review Committee. Thank you for your assistance. Write: CNATT Rate Training Manager 230 Chevalier Field Avenue Pensacola, FL 32508 E-mail: Refer to NKO ATO rate training Web page for current contact information. 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CHAPTER 10 ELECTROSTATIC DISCHARGE The electrical noise generated in a radio or radar receiver is often confused with electrical noise generated external to and coupled into the receiver. The internally generated noise is the result of circuit deficiencies in the receiver itself, and can be eliminated by replacing the defective component or replacing the entire receiver. Electrical noise produced external to the receiver enters the receiver by various means. The noise causes interference in the receiver, as well as poor reception. In early naval aircraft, electrical noise interference was not a major problem because there were fewer external sources of electrical noise. Receiver sensitivities were low, and the aircraft control components were manually operated. In today’s aircraft, however, there are considerably more sources of externally generated electrical noise. The aircraft now contains numerous receivers with higher sensitivities, and aircraft controls are operated by various electrical and/or mechanical devices. These devices include control surface drive motors, fuel and hydraulic boost pumps, alternating current (ac) inverters, and cabin pressurization systems. In addition, pulsed electronic transmitters, such as Tactical Air Navigation (TACAN), radar, and Identification Friend or Foe (IFF), can be sources of electrical noise interference. Listening to electrical noise interference in the output of a radio receiver can cause nervous fatigue in aircrew personnel. Electrical noise may also reduce the performance (sensitivity) of the receiver. For these reasons, electrical noise should be kept at the lowest possible level. The overall objective of this chapter is to assist you in recognizing various types of electrical/ electronic noise, their effects on radio and radar receivers, and what the electrostatic discharge program means to you as an aviation electronics technician (AT). This chapter also provides you with information for keeping electrical noise interference as low as possible in electronic equipment aboard naval aircraft. LEARNING OBJECTIVES When you have completed this chapter, you will be able to do the following: 1. Recognize the effects of natural electrical interference. 2. Recognize the effects of man-made electrical interference. 3. Identify the sources of electrical noise. 4. Recognize the effects of electrical noise. 5. Identify various types of electrical interference caused by coupling. 6. Describe methods to reduce electrical interference caused by coupling. 7. Identify components that are used to reduce radio interference caused by electrical noise. 8. Describe the purpose of bonding. 9. Identify the hazards to electrostatic discharge sensitive devices. 10. Identify materials used to package and protect electrostatic discharge sensitive devices. 11. Explain the proper handling techniques when packaging electrostatic discharge sensitive devices. 10-1 TYPES AND EFFECTS OF RECEIVER NOISE INTERFERENCE The types of electrical noise interference that enter aircraft receivers are broadly categorized as natural interference and man-made interference. Natural Interference Radio interference caused by natural electrical noise is separated into three types: atmospheric static, precipitation static, and cosmic noise. Each type is discussed below. Atmospheric Static Atmospheric static is a result of the electrical breakdown between masses (clouds) of oppositely charged particles in the atmosphere. An extremely large electrical breakdown between two clouds or between the clouds and ground is called lightning (Figure 10-1). Atmospheric static is completely random in nature, both as to rate of recurrence and as to intensity of individual discharges. Atmospheric static produces irregular popping and crackling in audio outputs and false indications on visual output devices. Its effects range from minor annoyance to complete loss of receiver usefulness. Atmospheric interference is seldom of a crippling intensity at frequencies from 2 to 30 megahertz (MHz). Above 30 MHz, the noise intensity decreases to a very low level. At frequencies below 2 MHz, natural static is the principal limiting factor on usable receiver sensitivity. Figure 10-1 — Example of atmospheric static. The intensity of atmospheric static varies with location, season, weather, time of day, and the frequency to which the receiver is tuned. It is most intense at the lower latitudes, during the summer season, during weather squalls, and at the lower radio frequencies. Many schemes have been devised to minimize the effects of atmospheric static. However, the best technique is to avoid those frequencies associated with intense static, if possible. Precipitation Static Precipitation static is a type of interference that occurs during dust, snow, or rain storms. The principal cause of precipitation static is the corona discharge of high voltage charges from various points on the airframe. These charges may reach several hundred thousand volts before discharge occurs. The charge can be built up in two ways. First, an electrostatic field existing between two oppositely charged thunderclouds induces bipolar (positive and negative) charges on the surfaces of the aircraft as it passes through the charged clouds. Second, a high unipolar charge on the entire airframe occurs from frictional charging by collision of atmospheric particles (low altitudes) or fine ice particles (high altitudes) with the aircraft’s surface. The effects of corona discharge vary with temperature. The effects increase as altitude and airspeed increase. Doubling airspeed increases the effect by a factor of about 8; tripling airspeed increases the effect by a factor of about 27. 10-2 The effect of precipitation static is a loud hissing or frying noise in the audio output of a communication receiver and a corresponding false indication on a visual output device. The radio frequency range affected by precipitation static is nearly the same as for atmospheric static. When present, precipitation interference is severe, and often totally disables all receivers tuned to the low and medium frequency bands. Cosmic Noise Cosmic noise is usually heard in the ultrahigh frequency band and above, but it is occasionally heard at frequencies as low as 10 MHz. Cosmic noise is a byproduct of the radiation of stars. Although its effect is generally unnoticed, at peaks of cosmic activity, cosmic noise interference could conceivably be a limiting factor in the sensitivity of navigational and height finder radar receivers. Man-Made Interference Man-made interference is generally categorized according to the spectrum of its influence, such as broadband and narrow band. Each type of man-made interference is discussed below. Broadband Interference Broadband interference is generated when the current flowing in a circuit is interrupted or varies at a rate that departs radically from a sinusoidal rate. A current whose waveform is a sine wave is capable of interfering only at a single frequency. Any other waveform contains harmonics of the basic frequency. The steeper the rise or fall of current, the higher the upper harmonic frequency will be. A perfect rectangular pulse contains an infinite number of odd harmonics of the frequency represented by its pulse recurrence rate. Typical types of electrical disturbances that generate broadband interference are electrical impulses, electrical pulses, and random noise signals. For purposes of this discussion, impulse is the term used to describe an electrical disturbance, such as a switching transient that is an incidental product of the operation of an electrical or electronic device. The impulse recurrence rate may or may not be regular. Pulse is the term used to describe an intentional, timed, momentary flow of energy produced by an electronic device. The pulse recurrence rate is usually regular. Switching transients or impulses result from the make or break of an electrical current. They are extremely sharp pulses. The duration and peak value of these pulses depend upon the amount of current and the characteristics of the circuit being opened or closed. The effects are sharp clicks in the audio output of a receiver and sharp spikes on an oscilloscope trace. The isolated occasional occurrence of a switching transient has little or no significance. However, when repeated often enough and with sufficient regularity, switching transients are capable of creating intolerable interference to audio and video circuits, and degradation of receiver performance. Typical sources of sustained switching transients are ignition timing systems, commutators of direct current (dc) motors and generators, and pulsed navigational lighting. Pulse interference is normally generated by pulsed electronic equipment. This type of interference is characterized by a popping or buzzing in the audio output device and by noise spikes on an oscilloscope. The interference level depends upon the pulse severity, repetition frequency, and regularity of occurrence. Pulse interference can trigger beacons and IFF equipment and cause false target indications on the radar screens. In certain types of navigational beacons, these pulses cause complete loss of reliability. Random noise consists of impulses that are of irregular shape, amplitude, duration, and recurrence rate. Normally, the source of the random noise is a variable contact between brush and commutator bar or slip ring, or an imperfect contact or poor electrical isolation between two surfaces. 10-3 Narrow Band Interference Narrow band interference is almost always caused by oscillators or power amplifiers in receivers and transmitters. In a receiver, the cause is usually a poorly shielded local oscillator stage. In a transmitter, several of the stages could be at fault. The interference could be at the transmitter operating frequency, a harmonic of its operating frequency, or at some spurious frequency. A multichannel transmitter that uses crystal-bank frequency synthesizing circuits can produce interference at any of the frequencies present in the synthesizer. Narrow band interference in a receiver can range in severity from a heterodyne whistle in the audio output to the complete blocking of received signals. Narrow band interference affects single frequencies or spots of frequencies in the tuning range of the affected receiver. SOURCES OF ELECTRICAL NOISE Any circuit or device that carries a varying electrical current is a potential source of receiver interference. The value of the interference voltage depends upon the amount of voltage change. The frequency coverage depends upon the abruptness of the change. The principal sources of man-made interference in aircraft include rotating electrical machines, switching devices, pulsed electronic equipment, propeller systems, receiver oscillators, nonlinear elements, and ac power-lines. Each of these sources of noise is discussed in the following sections. Rotating Electrical Machines Rotating electrical machines are a major source of receiver interference because of the large number of electric motors used in the aircraft. Rotating electrical machines used in aircraft may be divided into three general classes: dc motors, ac motors and generators, and inverters. Direct Current Motors Modern aircraft use dc motors in great numbers, such as in flight control actuators, armament actuators, and flight accessories. Most electronic equipment on the aircraft include one or more dc motors for driving cycling mechanisms, compressor pumps, air circulators, and antenna mechanisms. Each of these motors can generate voltages capable of causing radio interference over a wide band of frequencies. Types of interfering voltages generated by dc motors are as follows: • Switching transients generated as the brush moves from one commutator bar to another (commutation interference) • Random transients produced by varying contact between the brush and the commutator (sliding contact interference) • Audio frequency hum (commutator ripple) • Radio frequency and static charges built up on the shaft and the rotor assembly The dc motors used in aircraft systems are of three general types: the series-wound motor, the shuntwound motor, and the compound type. The field windings of both series- and shunt-wound motors afford some filter action against transient voltages generated by the brushes. The compound motor has the characteristics of both series and shunt dc motors. The size of a dc motor has little bearing upon its interference-generating characteristics. The smallest motor aboard the aircraft can be the worst offender. Alternating Current Generators and Motors The output of an ideal ac generator is a pure sine wave. A pure sine wave voltage is incapable of producing interference except at its basic frequency. However, a pure waveform is difficult to 10-4 produce, particularly in a small ac generator (Figure 10-2). Nearly all types of ac generators used in naval aircraft are potential sources of interference at frequencies other than the output power frequency. Interference voltages are produced by the following sources: • Harmonics of the power frequency. Generally, the harmonics are caused by poor waveform. • Commutation interference. This condition originates in a series-wound motor. • Sliding-contact interference. This condition originates in an alternator and in a serieswound motor. Generally, an ac motor without brushes does not create interference. Inverters An inverter (Figure 10-3) is a dc motor with armature taps brought out to slip rings to supply an ac voltage. The ac output contains some of the interference voltages generated at the dc end, as well as the brush interference at the ac end of the inverter. Figure 10-2 — Brush type, three-phase ac generator. Switching Devices A switching device makes abrupt changes in electrical circuits. Such changes are accompanied by transients capable of interfering with the operation of radio and other types of electronic receivers. The simple manual switch (occasionally operated) is of little consequence as a source of interference. Examples of switching devices (frequently operated) capable of causing appreciable or serious interference are the relay and the thyratron. Relays A relay is an electromagnetically operated remote control switch. Its main purpose is to switch high current, high voltage, or other critical circuits. Since the relay is used almost exclusively to control large amounts of power with relatively small amounts of power, the relay is always a potential source of Figure 10-3 — Typical aircraft inverter. interference. This is especially true when the relay is used to control an inductive circuit. Relay actuating circuits should not be overlooked as possible interference sources. Even though the actuating currents are small, the inductances of the actuating coils are usually quite high. It is not unusual for the control circuit of a relay to produce more interference than the controlled circuit. 10-5 Thyratrons A thyratron is a gas-filled, grid-controlled, electronic switching tube used mainly in radar modulators. The current in a thyratron is either on or off; there is no in between. Since the time required to turn a thyratron on is only a few microseconds, the current waveform in a thyratron circuit always has a sharp leading edge. As a result, the waveform is rich in radio interference energy. The voltage and peak power in a radar modulator are usually very high, and the waveforms are intentionally made as sharp and flat as possible. Although these factors are essential for proper radar operation, they also increase the production of interference energy. Pulsed Electronic Equipment Pulse interference is generated by pulsed electronic equipment. Types of systems that fall within this category include radar, transponders, coded-pulse equipment, and beacons. Radar In radar equipment, range resolution depends largely on the sharpness of the leading and trailing edges of the pulse. The ideal pulse is a perfect square wave. Target definition is also dependent on the narrowness of the pulse. Both the steepness and the narrowness of a pulse determine the number and amplitudes of harmonic frequencies. With respect to the shape of a radar pulse, the better the radar is working, the greater the interference it is capable of producing. Most of the interference is produced at frequencies other than those leaving the radar antenna, except in receivers operating with the radar band. Radar interference at frequencies below the antenna frequency severely affects all receivers in use. Principal sources of such interference are the modulator, pulse cables, and transmitters. Transponders, Coded-Pulse Equipment, and Beacons This group includes IFF, beacons, TACAN, teletype, and other coded-pulse equipment. The interference energy produced by this group is the same as that produced by radarpulsing circuits. The effects of this interference energy are lessened because the equipment is usually self-contained in one shielded case, and uses lower pulse power. The effects are increased because the radiating frequencies are lower, which allows fundamental frequencies and harmonics to fall within the frequency bands used by other equipment. Each piece of equipment is highly capable of producing interference outside the aircraft where it can be picked up by receiver antennas. Propeller Systems Propeller systems, whether hydraulically or electrically operated, are potent generators of radio interference (Figure 10-4). The sources of interference include propeller pitch control motors and solenoids, governors and Figure 10-4 — Typical propeller system. 10-6 associated relays, synchronizers and associated relays, deicing timers and relays, and inverters for synchro operation. Propeller control equipment generates clicks and transients as often as 10 per second. The audio frequency envelope of commutator interference varies from about 20 to 1,000 hertz (Hz). The propeller deicing timer generates intense impulses at a maximum rate of about 4 impulses per minute. Values of current in the propeller system are relatively high; consequently, the interference voltages generated are severe. They are capable of producing moderate interference at frequencies below 100 kilohertz (kHz) and at frequencies above 1 MHz. However, the interference voltages can cause severe interference at intermediate frequencies. Receiver Oscillators Either directly or through frequency multipliers or synthesizers, the local oscillator in a superheterodyne receiver generates a radio frequency signal at a given frequency. The local oscillator signal is mixed with another radio frequency signal to produce an intermediate frequency signal. Depending on receiver design, the frequency of the local oscillator signal is either above or below the frequency of the radio frequency signal by a frequency equal to the intermediate frequency. The amount of interference leaving the receiver through its antenna is roughly proportional to the ratio of the tuned input frequency to the intermediate frequency. For any tuning band on the receiver, oscillator leakage is highest at the low end of the band. In addition, the lower the intermediate frequency is, the greater the leakage probability. Although the receiver antenna is the principal outlet of oscillator leakage, leakage can occur from other points. Any path capable of introducing interference into a receiver is also capable of carrying internally generated interference out of the receiver. The paths of entry are discussed in more detail later in this chapter. Oscillator leakage from a single communications receiver in an aircraft is not likely to be a direct source of interference, except in a very large aircraft where two or more frequencies in the same band are used simultaneously. However, high order harmonics of the oscillator frequency can become problematic in the very high frequency band and above. Oscillator leakage from a swept-tuning receiver can produce interference in any receiver aboard the aircraft. This is done directly (on harmonics) or by nonlinear mixing, as shown in the following example: • Receiver A, operating at a frequency of 2,100 kHz, with an intermediate frequency of 500 kHz, has oscillator leakage at 2,600 kHz (or 1,600 kHz). • Receiver B, operating at 150 MHz, with an intermediate frequency of 10 MHz, has oscillator leakage at 160 MHz (or 140 MHz). • Receiver C, sweeping a frequency band from 200 to 300 MHz, with an intermediate frequency of 30 MHz, has oscillator leakage across the band 170 to 270 MHz (or 230 to 330 MHz). Each receiver is capable of interfering with the other receivers at the oscillator frequency and its harmonics. In addition, with the presence of a nonlinear detector, the leakage signals from the three receivers can be mixed and interfere with the following frequencies: • Receivers A and B, after nonlinear mixing, can produce interference at 160 ± 2.6 MHz. • Receivers A and C can similarly produce interference at any frequency from 200 ± 2.6 MHz to 300 ± 2.6 MHz; receivers B and C between 200 ± 160 MHz to 300 ± 160 MHz. 10-7 Nonlinear Elements A nonlinear element is a conductor, semiconductor, or solid state device whose resistance or impedance (opposition to current flow) varies with the voltage applied across it. Consequently, the resultant voltage is not proportional to the original applied voltage. Typical examples of nonlinear elements are metallic oxides, certain non-conducting crystal structures, semiconductor devices, and electron tubes. Nonlinear elements that could cause radio interference in aircraft systems are overdriven semiconductors, oxidized or corroded joints, cold solder joints, and unsound welds. In the presence of a strong signal, a nonlinear element acts like a detector or mixer. It produces sum and difference frequencies and any harmonics from the signal applied to it. These spurious frequencies are called external cross-modulation. The external cross-modulations can be expected to cause interference problems when the combined products of their field strength exceed 1 millivolt. A common example of this action is the entry of a strong off radio frequency voltage into the mixer stage of a superheterodyne receiver. By the time the interfering signal has passed through the preselector stages of the receiver, it has undergone distortion by clipping. Therefore, the interfering signal is essentially a rectangular wave that is rich in harmonics. Frequency components of the wave beat both above and below the local oscillator frequency and its harmonics, and produce, at the output of the mixer, signals that are acceptable to the intermediate frequency amplifier. Power- Lines Alternating current power sources have already been briefly discussed as broadband interference. Even though they are conducting a nearly sinusoidal waveform, ac signals on power-lines are capable of interfering with audio signals in receivers. In such cases, only the power-line frequency appears. However, where multiple sources of ac power are present, these signals are capable of being mixed in the same manner as discussed under receiver oscillators. Sum and difference frequencies will appear. In ac-powered equipment, ac hum can appear at the power frequency or at the rectification ripple frequency. The rectification ripple frequency is twice the power frequency times the number of phases. Normally, aircraft systems use only single- and three-phase sources at a nominal frequency of 400 Hz. Full-wave rectification with single-phase 400 Hz power gives a ripple frequency of 800 Hz. A three-phase source would give a 2,400 Hz ripple. This ripple produces interference varying from problematic to complete unreliability of equipment, depending upon the severity and its coupling to susceptible elements. INTERFERENCE COUPLING Openings in the outer shields of equipment are necessary for the entrance of power leads, control leads, mechanical linkages, ventilation, and antenna leads. Interference entering these openings is amplified by various amounts, depending upon the point of entry into the equipment’s circuits. Coupling between the entry path and the sensitive points of the receiver can be in any form. Conductive Coupling Interference is often coupled from its source to a receiver by metallic conduction. Normally, this is done by way of mutual impedance, as shown in Figure 10-5. Note in the figure that “A” is the power source (the battery), “B” the receiver, and “C” the interference source. The interference is greatest at (C) and attenuates rapidly to a relatively low value at (A). This occurs because of the very low impedance of the battery. It is apparent from the size of the arrows that the nearer the current flow of (B) to (C), the greater the amplitude of interfering current in the “BC” loop. 10-8 Interaction Available Figure 10-5 — Path of conducted interference. Inductive-Magnetic Coupling Every current-carrying conductor is surrounded by a magnetic field whose intensity variations are faithful reproductions of variations in the current in the conductor. When another parallel conductor is cut by the lines of force of this field, the conductor has a current induced into it. The amplitude of the induced current depends upon the following factors: • The strength of the current in the first conductor • The nearness of the conductors to each other • The angle between the conductors • The length through which the conductors are exposed to each other The amount of the variation in the current that directly affects variation in the magnetic field surrounding the conductor depends upon the nature of the current. When the conductor is a power lead to an electric motor, all the frequencies and amplitudes associated with broadband interference are present in the magnetic field. When the lead is an ac power lead, a strong sinusoidal magnetic field is present. When the lead is carrying switched or pulsed currents, extremely complex broadband variations are present. As the magnetic field cuts across a neighboring conductor, a voltage replica of its variation is induced into the neighboring wire. This causes a current to flow in the neighboring wire. When the neighboring wire leads to a sensitive point in a susceptible receiver, serious interference with that receiver’s operation can result. Similarly, a wire carrying a steady, pure dc of high value sets up a magnetic field capable of affecting the operation of equipment whose operation is based upon the earth’s magnetic field. Shielding a conductor against magnetic induction is both difficult and impractical. Nonferrous shielding materials have little or no effect upon a magnetic field. Magnetic shielding that is effective at low frequencies is prohibitively heavy and bulky. In aircraft wiring, the effect of induction fields should be minimized. This can be done by use of the proper spacing and coupling angle between wires. The degree of magnetic coupling diminishes rapidly with distance. Interference coupling is least when the space between active and passive leads is at a maximum, and when the angle between the leads approaches a right angle. 10-9 Inductive-Capacitive Coupling Capacitive (electric) fields are voltage fields. Their effects depend upon the amount of capacitance existing between exposed portions of the noisy circuit and the noise-free circuit. The power transfer capabilities are directly proportional to frequency. Thus, high-frequency components are more easily coupled to other circuits. Capacitive coupling is relatively easy to shield out by placing a grounded conducting surface between the interfering source and the susceptible conductor. Coupling by Radiation Almost any wire in an aircraft system can, at some particular frequency, begin to act like an antenna through a portion of its length. Inside an airframe, however, this occurs only at very high frequencies. At high frequencies, all internal leads are generally well shielded against pickup of moderate levels of radiated energy. Perhaps the only cases of true inside-the-aircraft radiation at high frequency and below occur in connection with unshielded or inadequately shielded transmitter antenna leads. Complex Coupling Some examples of interference coupling involve more than one of the types (conduction, induction, or radiation) just discussed. When more than one coupling occurs simultaneously, corrective actions, such as bonding, shielding, or filtering, used to correct one type of coupling can increase the coupling capabilities of another type. The result may be an increase in the transfer of interference. For example, an unfiltered dc motor can transfer interference to a sensitive element by conduction, inductive coupling, capacitive coupling, and radiation. Some frequencies are transmitted predominately by one form of coupling and some frequencies by others. At still other frequencies, all methods of transmission are equally effective. On the motor used in the example above, bonding almost always eliminates radiation from the motor shell. It also increases the intensity in one of the other methods of transmission, usually by conduction. The external placement of a low-pass filter or a capacitor usually reduces the intensity of conducted interference. At the same time, it may increase the radiation and induction fields. This occurs because the filter appears to interference voltages to be a low-impedance path across the line. Relatively high interference currents then flow in the loop formed between the source and the filter. For complex coupling problems, multiple solutions may be required to prevent the interference. RADIO INTERFERENCE REDUCTION COMPONENTS Radio interference reduction at the source may be accomplished to varying degrees by one or more of the following methods: short-circuiting, dissipation, open-circuiting, or a combination of all three. Discrete components are normally used to achieve interference reduction at the source. Capacitors, resistors, and inductors are used to short-circuit, dissipate, and open-circuit the interference, respectively. Capacitors Short-circuiting of interference is done by using capacitors connected across the source. The perfect capacitor looks like an open-circuit to dc or the power frequency, and progressively as a short-circuit to ac as the frequency is increased. Function The function of a capacitor in connection with radio interference filtering is to provide a lowimpedance radio frequency path across the source. When the reactance of the capacitor is lower than the impedance of the power-lines to the source, high-frequency voltages see the capacitor as a 10-10 shorter path to ground. The capacitor charges to the line voltage. It then tends to absorb transient rises in the line voltage and to provide energy for canceling transient drops in the line voltage. Limitations The efficiency of a perfect capacitor in bypassing radio interference increases in indirect proportion to the frequency of the interfering voltage, and in direct proportion to the capacitance of the capacitor. All capacitors have both inductance and resistance. Any lead for connecting the capacitor has inductance and resistance as a direct function of lead length and inverse function of lead diameter. Some resistance is inherent in the capacitor itself in the form of dielectric leakage. Some inductance is inherent in the capacitor, which is usually proportional to the capacitance. The effect of the inherent resistance in a high-grade capacitor is negligible as far as its filtering action is concerned. The inherent inductance, plus the lead inductance, seriously affects the frequency range over which the capacitor is useful. The bypass value of a capacitor with inductance in series varies with frequency. At frequencies where inductive reactance is much less than capacitive reactance, the capacitor looks very much like pure capacitance. As the frequency approaches a frequency at which the inductive reactance is equal to the capacitive reactance, the net series reactance becomes smaller until the resonant frequency, a point of zero impedance, is reached. At this point, maximum bypass action occurs. At frequencies above the resonant frequency, the inductive reactance becomes greater than the capacitive reactance. The capacitor then exhibits a net inductive reactance, whose value increases with frequency. At frequencies much higher than the resonant frequency, the value of the capacitor as a bypass becomes lost. The frequency at which the reversal of reactance occurs is controlled by the size of the capacitor and the length of the leads. For instance, the installation of a very large capacitor frequently requires the use of long leads. Table 10-1 is representative of a typical 4-microfarad (µF) capacitor whose inherent inductance is 0.0129 henrys. Table 10-1 — Lead Length Changes LEAD LENGTH CROSSOVER FREQUENCY 1 inch 0.47 MHz 2 inches 0.41 MHz 3 inches 0.34 MHz 4 inches 0.30 MHz 6 inches 0.25 MHz Note that for the 4 µF capacitor, each additional inch of lead causes the capacitance-inductance crossover point to be reduced. Notice in Figure 10-6 the capacitance-to-inductance crossover frequencies for various lead lengths of a 0.05 µF capacitor. Also, notice the difference in the crossover frequencies for the 3-inch lead for the 4 µF capacitor, discussed above, and for the 3-inch lead for the 0.05 µF capacitor, shown in Figure 10-6. Coaxial Feedthrough Capacitors Coaxial feedthrough capacitors are available with capacitances from 0.00005 to about 2 µF. These capacitors work well up to frequencies several times those at which capacitors with leads become useless. The curves in Figure 10-7 compare the bypass value of a feedthrough capacitor of 0.05 µF with that of a hypothetically perfect capacitor of the same capacitance. The feedthrough capacitor 10-11 differs from the capacitor with leads in that the feedthrough capacitor type forms a part of both the circuit being filtered and the shield used to isolate the filtered source. Lead length has been reduced to zero. The center conductor of the feedthrough capacitor must carry all the current of the filtered source and must have an adequate current rating to ensure against dc loss or power frequency insertion loss. The internal constructions of feedthrough and conventional capacitors are shown in Figure 10-8. Notice the differences in the two types. Figure 10-6 — Crossover frequency of a 0.05 µF capacitor with varied lead lengths. Figure 10-7 — Crossover frequency of a 0.05 µF feedthrough capacitor. 10-12 Figure 10-8 — Internal construction of feedthrough and conventional capacitor. Selection of Capacitors Capacitors used for filtering circuits in aircraft should be selected for characteristics such as physical size, high temperature and humidity tolerances, and physical ruggedness. The capacitors should have an adequate voltage rating (at least twice that of the circuit to be filtered), and should be installed with minimum lead length. Application of Capacitive Filters Every circuit carrying an unintentionally varying voltage or current capable of causing radio interference should be bypassed to ground by suitable capacitors. When the nature of the variations is such that interference is caused at both high and low frequencies, a capacitor should be chosen and installed to provide an adequate insertion loss at the lowest frequency where interference exists. When the overall capacitance required at low frequency provides inadequate insertion loss at high frequencies, it should be bridged in the shortest and most direct manner possible by a second capacitor. A capacitive filter should be installed as near as possible to the actual source of interference. Lead length should be held to an absolute minimum for two reasons. First, the lead to the capacitor carries interference that must not be allowed to radiate. Second, the lead has inductance that tends to lower the maximum frequency for which the capacitor is an effective bypass. To the extent possible, a filter capacitor should be installed to make use of any element of the filtered circuit that provides a better filtering action. The use of filter capacitors is shown in Figure 10-9. Capacitive Filtering in an Alternating Current Circuit The radio interference generated in slip ring ac motors and generators is a transient caused by sliding contacts plus high-frequency energy from other internal sources. For this reason, filtering should be aimed at reducing high-frequency and very-high-frequency noise components with the use of lowcapacitance, high-grade capacitors. Wherever possible, feedthrough capacitors should be used. Capacitances should be chosen low enough in value to represent high impedance at the power frequency and to avoid resonance with the internal inductances of the filtered unit. Voltage ratings should be at least twice the peak voltage across the capacitors. 10-13 Figure 10-9 — Capacitive filtering of a three-phase attenuator. In a four-wire electrical system, the neutral lead carries all three phases; a large quantity of the third harmonic of the power frequency is present. This frequency must be considered in setting capacitance limits and in filtering the return lead. Normal values of capacitance for filtering 400 Hz leads vary from 0.05 to 0.1 µF. Capacitive Filtering of Switching Devices Normally, a capacitor should not be used by itself as a filter on a switch in a dc system. In the open position, the capacitor bridging the switch assumes a charge equal to the line voltage. When the switch closes, the capacitor discharges at such a rapid rate that it generates a transient energy, whose interference value exceeds that caused by the opening of the unfiltered circuit. The capacitor across a switch should have enough series resistance to provide a slow discharge when the capacitor is shorted by the switch. Resistive-Capacitive Filters A resistive-capacitive (RC) filter is an effective arc and transient absorber. The RC filter reduces interference in two ways: by changing the waveform of transients and by dissipating transient energy. An example of a RC filter connected across a switch is shown in Figure 1010. Without the RC filter, the voltage appearing across the switch at the instant the switch is opened is equal to the sum of the line voltage and an inductive voltage of the same polarity. The amplitude of the inductive surge depends upon the inductance of the line and the amplitude of the closed-circuit current. Figure 10-10 — RC filter connected across a switch. When the sum of the voltages appearing across the switch is great enough, arcing occurs. When the capacitance is large enough, the capacitor absorbs sufficient transient energy to reduce the voltage to below arcing value. During the charging time of the capacitor, the resistor is passing current and dissipating some of the transient energy. For maximum absorption of the circuit opening transients, resistance should be small and capacitance should be large. Good representative values are resistance = 1/5 load resistance and capacitance = 0.25 µF. 10-14 Two RC filters used to absorb the transient interference resulting from the opening of a relay field are shown in Figure 10-11. In circuit “A,” the value of “Ra” should be low enough to provide a resistance path to ground less than the line impedance and high enough to lower the value of the charge (Q) sufficiently. The capacitor should be at least 0.25 µF with a voltage rating several times the lone voltage. Circuit “B” has the advantages of reducing the capacitor and coil leads to absolute minimum and reducing the relay field current. It has the disadvantage of carrying the dc coil current. Normal values of each resistance (Rb) in circuit “B” is 5 percent of the dc resistance of the coil. The capacitor is normally 0.25 µF. Circuit “B” serves as both a damping load and a high-loss transmission line. Figure 10-11 — Methods for using RC filters in relay circuits. Inductive-Capacitive Filters Filtering of radio interference is done by means of an inductor inserted in series with the ac power source. The inductor offers negligible impedance to the ac or power- line frequency and an increasingly high impedance to transient interference as frequency is increased. Combinations of inductance and capacitance are widely used to reduce both broadband and narrow band interference. Filters come in a large variety of types and sizes. Filters are classified as to their frequency characteristics such as low-pass, high-pass, bandpass, and band-rejection filters. Filters are also classified as to their applications, such as power-line, antenna, and audio filters. The type most often used in aircraft is the low-pass, power-line filter. Low-Pass Filters A low-pass filter is used in an aircraft to power leads coming from interference sources. The filter prevents the transmission of interference voltages into the wiring harness, and blocks transmission or reception of radio-frequency energy above a specified frequency. The ideal low-pass filter has no insertion loss at frequencies below its cutoff frequency, but has infinite insertion loss at all higher frequencies. Practical filters fall short of the ideal in three ways. First, a filter of acceptable physical size and weight has some insertion loss, even under dc conditions. Second, because of the lack of a pure 10-15 Figure 10-12 — Insertion loss curve of a low-pass power-line filter. inductor, the transition from low to high impedance is gradual instead of abrupt. Third, the impedance is held to a finite value for the same reason. The insertion loss of a typical low-pass filter as compared to a hypothetical ideal filter is shown in Figure 10-12. The arrangement and typical parameters of a lowpass filter that has a design cutoff frequency of 100 kHz is shown in Figure 10-13. Inductor “L” must carry load current. It must be wound of wire large enough that its dc insertion loss is negligible. Therefore, filters are rated to maximum current. In addition, the capacitors “C1” and “C2” must withstand the line voltage. Therefore, filters are also rated as to maximum voltage. Figure 10-13 — Low-pass filter circuit. At frequencies immediately below cutoff, the filter looks capacitive to both the generator and the load. Inductive reactance has very little influence, and no filtering action takes place. However, at frequencies above cutoff, the series reactance of coil “L” becomes increasingly higher. The series reactance of coil “L” is limited only by the resistance of the coil and its distributed capacitance. Coil “L” then functions as a high-frequency disconnect. The bypass values of both capacitors “C1” and “C2” become increasingly higher, and are limited only by the inductance of the capacitors and their leads. As a result of these two actions, high-frequency isolation between points “A” and “B” is achieved. High-Pass Filters In almost all radio transmitters operating at high frequencies and above, the master oscillator signal is generated at a submultiple of the output frequency. By using one or more frequency multipliers, the basic oscillator frequency is raised to the desired output frequency. At the input to the antenna, an overdriven output amplifier may output the output frequency and harmonics of the output frequency. A high-pass filter is very effective in preventing the undesired harmonics from reaching the antenna and being radiated. High-pass filters are also useful for isolating a highfrequency receiver from the influence of energy of Figure 10-14 — Schematic diagram of a highsignals of lower frequencies. A typical high-pass pass filter section. filter being used to reduce radio noise interference is shown in Figure 10-14. In symmetrical high-pass filter sections, the total opposition to current flow in is equal to the total opposition to current flow out. The series combination of “C1” and “L” should resonate at √2 times the desired cutoff frequency. The impedance and current flow ratio that is chosen should have a square root equal to the terminal impedance. Bandpass Filters Bandpass filters provide very high impedance above and below a desired set of frequencies within that band. 10-16 Bandpass filters find their greatest application in the following manners: • Decoupling the receiver from shock and overload by transmitters operating above and below the receiver band • Multiplexing and decoupling two or more receivers or transmitters using the same antenna A bandpass filter can be one of many forms and configurations, depending upon its application. For filtering antennas, a bandpass filter normally consists of one or more high-pass filter sections, followed by one or more low-pass filter sections. The configuration of sections is normally selected so the upper limit of the pass band approaches or exceeds twice the frequency of the lower limit of the pass band. Typical arrangements for bandpass filters are shown in Figure 10-15. Figure 10-15 — Examples of bandpass filter circuits. Band-Rejection Filters A band-rejection (band-stop) filter is used to reject or block a band of frequencies from being passed. This filter allows all frequencies above and below this band to be passed with little or no attenuation. The band-stop filter circuit consists of inductive and capacitive networks combined and connected to form a definite frequency response characteristic. The band-stop filter is designed to attenuate a specific frequency band and to permit the passage of all frequencies not within this specific band. The frequency range over which attenuation or poor transmission of signals occurs is called the attenuation band. The frequency range over which the passage of signals readily occurs is called the bandpass. The lowest frequency at which the attenuation of a signal starts to increase rapidly is known as the lower cutoff frequency. The highest frequency at which the attenuation of a signal starts to increase rapidly is known as the upper cutoff frequency. The basic configurations into which the band-reject filter elements can be arranged or assembled are known as the half-section, the pisection, and the T-section configurations. These configurations are illustrated in Figure 10-16. BONDING Aircraft electrical bonding is defined as the process of obtaining the necessary electrical conductivity between all the metallic component parts of the aircraft. Bonding successfully brings all items of empennage and internal conduction objects to essentially the same dc voltage level appearing on the basic structure of the fuselage. However, bonding for radio frequencies is not quite so simple. Only direct bonding between affected components can accomplish the desired results at all frequencies. Only when direct bonding is impossible or operationally impracticable should bonding jumpers be 10-17 Figure 10-16 — Examples of band-reject filter circuits. used. Regardless of its dc resistance, any length of conductor has inductive reactance that increases directly with frequency. At a frequency for which the length of a bond is a quarter wavelength, the bond becomes high impedance. The impedance of such a resonant lead becomes greater without limit as the dc resistance becomes lower. Multiple bonding using the same length of bonding jumper increases the impedance at the resonant frequency, but also tends to sharpen the high impedance area around the resonant frequency. This sharpening is done by the rapid fall of impedance on each side of resonance. Purposes of Bonding Bonding must be designed and executed to obtain the following results: • Protect the aircraft and personnel from hazards associated with lightning discharges • Provide power-current and fault-current return paths • Provide sufficient uniformity and stability of conductivity for radio frequency currents affecting transmission and reception • Prevent development of ac potentials on conducting frames, enclosures, cables of electrical and electronic equipment, and conducting objects adjacent to unshielded transmitting antenna lead-ins • Protect personnel from the shock hazard resulting from equipment that experiences an internal power failure • Prevent the accumulation of static charges that could produce radio interference or be an explosion hazard due to periodic spark discharge Bonding for Lightning Protection Close-riveted skin construction that divides any lightning current over a number of rivets is considered adequately bonded to provide a lightning discharge current path. Control surfaces and flaps should have a bonding jumper across each hinge. A typical bonding arrangement on an aircraft surface is shown in Figure 10-17. To protect the control cables and levers, additional jumpers should be connected between the control surface and the structure. The length of a discharge path through the control system should be at least 10 times the length of the path of the jumper or jumpers. 10-18 All external electrically isolated conducting objects (except antennas) should have a bonding jumper to the aircraft to ensure a low-impedance path. This is done so the voltage drop developed across the jumper system by the lightning discharge is minimized. The bonding jumpers must be kept as short as possible. When practical, a bonding jumper should not exceed 3 inches. ELECTROSTATIC DISCHARGE Figure 10-17 — Typical aircraft bonding arrangement. The sensitivity of electronic devices and components to electrostatic discharge (ESD) has recently become clear through use, testing, and failure analysis. The construction and design features of current microtechnology have resulted in devices being destroyed or damaged by ESD voltages as low as 20 volts. An example of the type of damage caused by ESD is shown in Figure 10-18. Technologies are trending toward greater complexity, increased packaging density, and thinner dielectrics between active elements. Ultimately, this will result in devices becoming more sensitive to ESD. It is highly important that Figure 10-18 — ESD damaged components. you learn the effects of ESD because limiting the effects is critical to naval aviation. Various devices and components are susceptible to damage by electrostatic voltage levels commonly generated in production, test, and operation, and by maintenance personnel. The devices and components include the following: • All microelectronic and most semiconductor devices, except various power diodes and transistors • Thick and thin film resistors, chips and hybrid devices, and crystals All subassemblies, assemblies, and equipment containing these components and devices without adequate protective circuitry are ESD sensitive (ESDS). You can protect ESDS items by implementing simple, low-cost ESD controls. Lack of implementation has resulted in high repair costs, excessive equipment downtime, and reduced equipment effectiveness. The operational characteristics of a system may not normally show these failures. However, under internal built-in test 10-19 monitoring in a digital application, they become pronounced. For example, the system functions normally on the ground, but when placed in an operational environment, a damaged component might further degrade, causing its failure. Normal examination of these parts will not detect the damage unless you use a curve tracer to measure the signal rise and fall times, or check the parts for reverse leakage current. Table 10-2 — List of Triboelectric Substances TRIBOELECTRIC SUBSTANCES Acetate Static Electricity Glass Static electricity is electrical energy at rest. Some substances readily give up electrons while others accumulate excessive electrons. When two substances are rubbed together, are separated, or flow relative to one another (such as gas or liquid over a solid), one substance becomes negatively charged and the other positively charged. An electrostatic field or lines of force emanate between a charged object and an object at a different electrostatic potential or ground. Objects entering this field will receive a charge by induction. Human hair Nylon Wool Fur Aluminum Polyester Paper The capacitance of the charged object relative to another object or ground also has an effect on the field. If the capacitance is reduced, there is an inverse linear increase in voltage since the charge must be conserved. As the capacitance decreases, the voltage increases until a discharge occurs via an arc. Cotton Wood Steel Acetate fiber Nickel, copper, silver Causes of Static Electricity Generation of static electricity on an object by rubbing is known as the triboelectric effect. A list of substances in the triboelectric series is shown in Table 10-2. The list is arranged in such an order that when any two substances in the list contact one another and then separate, the substance higher on the list assumes a positive charge. Brass, stainless steel The size of an electrostatic charge on two different materials is proportional to the separation of the two materials. Electrostatic voltage levels generated by nonconductors can be extremely high. However, air will slowly dissipate the charge to a nearby conductor or ground. The more moisture in the air, the faster a charge will dissipate. The typical measured charges generated by personnel in a manufacturing facility are shown in Table 10-3. Note the decrease in generated voltage with the increase in humidity levels of the surrounding air. Rubber Acrylic Polystyrene foam Polyurethane foam Saran Polyethylene Polypropylene PVC (vinyl) KEL-F Teflon® Table 10-3 — Typical Measured Electrostatic Voltages VOLTAGE LEVEL @ RELATIVE HUMIDITY MEANS OF STATIC GENERATION LOW 10-20% HIGH 65-90% WALKING ACROSS CARPET 35,000 1,500 WALKING OVER VINYL FLOOR 12,000 250 WORKER AT BENCH 6,000 100 VINYL ENVELOPS FOR WORK INSTRUCTIONS 7,000 600 COMMON POLY BAG PICKED UP FROM BENCH 20,000 1,200 WORK CHAIR PADDED WITH URETHANE FOAM 18,000 1,500 10-20 Effects of Static Electricity The effects of ESD are not easily recognized. Failures due to ESD are often analyzed as being caused by electrical overstress due to transients other than static. Many failures, often classified as other, random, or unknown, are actually caused by ESD. Misclassification of the defect is often caused by not performing failure analysis to the proper depth. Component Susceptibility Some solid state devices with the exception of various power transistors and diodes are susceptible to damage by discharging electrostatic voltages. The discharge may occur across their terminals or through subjection of these devices to electrostatic fields. Latent Failure Mechanisms ESD overstress can produce a dielectric breakdown of a self-healing nature when the current is unlimited. When this occurs, the device may retest good, but contain a hole in the gate oxide. With use, metal will eventually migrate through the puncture, resulting in a shorting of this oxide layer. Another structure mechanism involves highly limited current dielectric breakdown from which no apparent damage is done. However, this reduces the voltage at which subsequent breakdown occurs to as low as one-third of the original breakdown value. ESD damage can result in a lowered damage threshold at which a subsequent lower voltage ESD will cause further degradation or a functional failure. ESD Elimination The heart of an ESD control program is the ESD protected work area and ESD grounded work station. When you handle an ESDS device outside of its ESD protective packaging, you need to provide a means to reduce generated electrostatic voltages below the levels at which the item is sensitive. The greater the margin between the levels at which the generated voltages are limited and the ESDS item sensitivity level, the greater the probability of protecting that item. Prime Generators All common plastics and other generators should be prohibited in the ESD protected work area. Carpeting should also be prohibited. If you must use carpet, it should be of a permanently antistatic type. It is important to perform weekly static voltage monitoring where carpeting is in use to lower the risk of an ESD incident. PERSONAL APPAREL AND GROUNDING An essential part of the ESD program is grounding personnel and their apparel when handling ESDS material. Means of doing this are described in this section. Smocks Personnel handling ESDS items, such as circuit cards and individual electronic components, should wear long sleeve, ESD protective smocks (Figure 10-19). They should also wear short sleeve shirts or blouses so that ESD protective gauntlets can be banded to the bare wrist and extend toward the elbow. If these items are not available, use other antistatic material (such as cotton) that will cover sections of the body that could contact an ESDS item during handling. 10-21 Personnel Ground Straps Personnel ground straps should have a minimum resistance of 250,000 ohms. Based upon limiting leakage currents to personnel to 5 milliamperes, this resistance will protect personnel from shock from voltages up to 125 volts rms. The wrist, leg, or ankle bracelet end of the ground strap should have some metal contact with the skin. Bracelets made completely of carbon-impregnated plastic may burnish around the area in contact with the skin, resulting in the impedance to ground being too high. ESD PROTECTIVE MATERIALS There are two basic types of ESD protective material, conductive and antistatic. Conductive materials protect ESD devices from static discharges and electromagnetic fields. Antistatic materials are nothing more than a non-staticgenerating material. Therefore, antistatic materials do not offer any other protection to ESD devices other than not generating static. Figure 10-19 — ESD protective smocks. Conductive ESD Protective Materials Conductive ESD protective materials consist of metal, metal-coated, and metal-impregnated materials. The most common conductive materials used for ESD protection are steel, aluminum, and carbon-impregnated polyethylene and nylon. The latter two are opaque, black, flexible, heat sealable, electrically conductive plastics. These plastics are composed of carbon particles, impregnated in the plastic, that provide volume conductivity throughout the material. Antistatic ESD Protective Materials Antistatic materials are normally plastic-type materials (such as polyethylene, polyolefin, polyurethane, and nylon) that are impregnated with an antistatic substance. The antistatic substance migrates to the surface and combines with the humidity in the air to form a conductive sweat layer on the surface. This layer is invisible, and although highly resistive, it is amply conductive to prevent the buildup of electrostatic charges by triboelectric methods in normal handling. Simply stated, the primary asset of an antistatic material is that it will not generate a charge on its surface. However, this material will not protect an enclosed ESD device if it comes into contact with a charged surface. This material is of a pink tint, which is a symbol of it being antistatic. Antistatic materials are designed to be used as the inner wrapping packaging. However, antistatic materials are not used unless components and/or assemblies are contained in conductive packaging. Hybrid ESD Protective Bags Lamination of different ESD protective material is available. This combination of conductive and antistatic materials provides the advantages of both types in a single bag. 10-22 ESDS DEVICE HANDLING The following are general guidelines applicable to the handling of ESDS devices: • Make sure that all containers, tools, test equipment, and fixtures used in ESD protected areas are grounded before and during use. • Personnel handling ESDS items must avoid physical activities that are friction producing in the vicinity of ESDS items. Some examples are putting on or removing smocks, wiping feet, and sliding objects over surfaces. • Personnel handling ESDS items must wear cotton smocks and/or other antistatically treated clothing. • Avoid the use or presence of plastics, synthetic textiles, rubber, finished wood, vinyl, and other static-generating materials where ESDS items are handled out of their ESD protective packaging. • Place the ESD protective material containing the ESDS item on a grounded work bench surface to remove any charge before opening the packaging material. • Personnel must ground themselves before removing ESDS items from their protective packing by attaching their personnel ground straps to an approved grounding location. • Remove ESDS items from ESD protective packaging with fingers or metal grasping tools only after grounding, and place on the ESD grounded work bench surface. • Make periodic electrostatic measurements in accordance with local procedures or applicable maintenance instructions at all ESD protected areas. This assures the ESD protective properties of the work station and all equipment contained have not degraded. • Perform periodic continuity checks of personnel ground straps, ESD grounded work station surfaces, conductive floor mats, and other connections to ground in accordance with local procedures or applicable maintenance instructions. ESDS DEVICE PACKAGING Before an ESDS item leaves an ESD protected area, package the item in one of the following ESD protective materials: • Ensure shorting bars, clips, or non-corrective conductive materials are correctly inserted in or on all terminals or connectors. • Package ESDS items using only approved packaging materials and prepare the items for shipment as per MIL-HDBK-773. • Mark the packaged unit with the ESD symbol and caution as shown in Figure 10-20 as required. 10-23 Figure 10-20 — ESDS symbols. 10-24 End of Chapter 10 Electrostatic Discharge Review Questions 10-1. During what season is atmospheric interference the greatest? A. B. C. D. Spring Summer Fall Winter 10-2. Other than dust or snow, what type of natural event can create precipitation static? A. B. C. D. Rain Wind Hail Sleet 10-3. Corona discharge can occur at what voltage level from the airframe of an aircraft? A. B. C. D. Low Negative High Positive 10-4. Cosmic noise can be heard on what frequency band? A. B. C. D. Very high Ultra high Low Voice 10-5. What type of radar receiver other than navigational can be potentially limited by cosmic noise? A. B. C. D. Height finder Fire control Search Doppler 10-6. The two general types of man-made interference are broadband and what other type? A. B. C. D. Medium band Low band Narrow band High band 10-25 10-7. Broadband interference is generated by impulses, pulses and what other type of electrical disturbance? A. B. C. D. Fixed noise Random noise Linear noise Cosmic noise 10-8. What type of electronic equipment can generate pulse interference? A. B. C. D. Impulse Transient Mixed Pulsed 10-9. Pulse interference can trigger beacons and what other avionics system? A. B. C. D. Identification Friend or Foe Tactical Air Navigation Radar Automatic Direction Finder 10-10. What type of motor commutators can cause sustained switching transients? A. B. C. D. Hydraulic Pneumatic Alternating current Direct current 10-11. What type of direct current motor has the characteristics of both the series and shunt types? A. B. C. D. Hybrid Compound Complex Fusion 10-12. When uninstalled, which component of alternating current motors should NOT cause interference? A. B. C. D. Coils Brushes Commutator Slip rings 10-13. What type of dc motor is capable of supplying ac voltage? A. B. C. D. Inverter Convertor Transformer Modifier 10-26 10-14. What type of switching device is made out of a gas-filled, electronic switching tube? A. B. C. D. Relay Remote Thyratron Transistor 10-15. What characteristic of harmonic frequencies determines the narrowness of radar pulses? A. B. C. D. Bandwidth Voltage Current Amplitude 10-16. Other than Identification Friend or Foe and beacons what other type of equipment uses codedpulses? A. B. C. D. Teletype Intercommunication systems Telephone Radio transmitter 10-17. What high electrical value generates severe interference voltages in propeller systems? A. B. C. D. Resistance Capacitance Current Impedance 10-18. Nonlinear elements include semiconductors, solid state devices and what other devices? A. B. C. D. Conductors Resistors Capacitors Inductors 10-19. What type of signal on power-lines is capable of interfering with audio signals? A. B. C. D. Analog Digital Alternating current Direct current 10-20. What method of conduction often couples a source to a receiver? A. B. C. D. Inductive Metallic Thermal Magnetic 10-27 10-21. It is difficult and impractical to shield conductors against what type of induction? A. B. C. D. Metallic Thermal Magnetic Electrical 10-22. What frequency band components are most easily coupled to other circuits? A. B. C. D. Low High Ultra high Super high 10-23. When externally placed, what type of filter normally reduces the intensity of conducted interference? A. B. C. D. High-pass Low-pass Bandpass Band-stop 10-24. When frequency is increased in an alternating current component, a perfect capacitor would appear as what circuit malfunction? A. B. C. D. Open-circuit Short-circuit Closed-circuit Parallel-circuit 10-25. At resonant frequency, the bypass value of which of the following components is lost? A. B. C. D. Resistor Conductor Transistor Capacitor 10-26. What distance should a capacitive filter be installed from a source of interference? A. B. C. D. Far as possible Middle distance Near as possible Opposite side 10-27. In a four-wire electrical system, what wire carries all three phases of power? A. B. C. D. Neutral Phase A Phase B Phase C 10-28 10-28. What should a capacitor NOT be used for in a direct current system? A. B. C. D. Resistor Inductor Semiconductor Filter 10-29. What type of capacitor is an effective arc and transient absorber? A. B. C. D. Inductive-capacitive Resistive-capacitive Low-pass High-pass 10-30. What type of filter has no insertion loss at frequencies below cutoff but infinite loss at higher frequencies? A. B. C. D. Low-pass Bandpass High-pass Band-rejection 10-31. What other configuration can a band-rejection filter be besides half-section and pi-section? A. B. C. D. I-section U-section R-section T-section 10-32. What type of filter provides very high impedance above and below a desired set of frequencies? A. B. C. D. Bandpass High-pass Low-pass Band-rejection 10-33. What process brings all metal and internal components of an aircraft to essentially the same direct current voltage level? A. B. C. D. Mixing Compounding Potting Bonding 10-34. A bond becomes high impedance at what frequency size? A. B. C. D. One-quarter One-third One-fifth One-half 10-29 10-35. What length of bonds will increase the impedance at the resonant frequency? A. B. C. D. One-quarter One-half Same Varied 10-36. Which of the following aircraft components does NOT require electrical isolation by a bonding jumper? A. B. C. D. Flap Slat Landing gear Antenna 10-37. Bonding must be designed to protect personnel against shock from what type of equipment failure? A. B. C. D. Sensitivity Control Power Input 10-38. Sensitive electronic devices are susceptible to what type of hazard? A. B. C. D. Electrostatic absorption Electrostatic discharge Electrostatic induction Electrostatic repulsion 10-39. What type of field emanates from a charged object to an object that has a different electrical potential? A. B. C. D. Reactive Electrostatic Inductive Magnetic 10-40. Misclassification of Electrostatic Discharge damage is often caused by NOT performing what type of analysis to the proper depth? A. B. C. D. Design Cost Failure Statistical 10-30 10-41. What common type of material is considered a prime generator of static electricity? A. B. C. D. Wood Glass Metal Plastic 10-42. Personnel ground straps are designed to protect workers from exposure to what maximum voltage level? A. B. C. D. 25 volts root mean square 50 volts root mean square 75 volts root mean square 125 volts root mean square 10-43. The most common conductive materials are steel, aluminum, carbon-impregnated polyethylenes, and what other material? A. B. C. D. Cotton Nylon Rayon Teflon® 10-44. What color material is identified as being antistatic? A. B. C. D. Yellow Red Pink Orange 10-45. Prior to being used in an Electrostatic Discharge protected area, tools and equipment must go through what process? A. B. C. D. Inventory Inspection Grounding Replacement 10-31 RATE TRAINING MANUAL – USER UPDATE CNATT makes every effort to keep their manuals up-to-date and free of technical errors. We appreciate your help in this process. If you have an idea for improving this manual, or if you find an error, a typographical mistake, or an inaccuracy in CNATT manuals, please write or e-mail us, using this form or a photocopy. Be sure to include the exact chapter number, topic, detailed description, and correction, if applicable. Your input will be brought to the attention of the Technical Review Committee. Thank you for your assistance. Write: CNATT Rate Training Manager 230 Chevalier Field Avenue Pensacola, FL 32508 E-mail: Refer to NKO ATO rate training Web page for current contact information. Rate ____ Course Name _____________________________________________ Revision Date __________ Chapter Number ____ Page Number(s) ___________ Description _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ (Optional) Correction _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ (Optional) Your Name and Address _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ 10-32 APPENDIX I GLOSSARY A/A—Air-to-air. A/G—Air-to-ground. ABSOLUTE ZERO—Measured at -273 degrees Celsius or -460 degrees Fahrenheit. ABSORPTION—In IR systems, the loss of energy that is turned into heat, which results in a temperature increase in a detector element. In sonar, sound energy that is absorbed while passing through the water. The absorption of sound can depend on the sea state. When the winds are high enough to produce whitecaps and a concentration of bubbles at the surface level, the absorption level of sound energy will be higher. In addition, the absorption of sound energy is greater at higher frequencies. AC—Alternating current—An electrical current that encompasses a constant change in amplitude and regular intervals of change in polarity. ACB—Armament control box. ACCELERATION—The increase in the rate or speed of an object. ACCELEROMETERS—A device that used to produce a voltage proportional to the aircraft acceleration input. Accelerometers provide output signals proportional to the total accelerations experienced along the three axes of the stable element. ACCURACY—In radar, the ability of a radar system to determine the correct range, bearing, and in some cases, altitude of a target. ACI—Armament control indicator—Installed in the MH-60R Seahawk helicopter and contains the control functions for the jettison, sonobuoy, and Hellfire armament subsystems. ACL RDY—Automatic carrier landing ready. ACLS—Automatic carrier landing system—Consists of multiple components installed in the aircraft and systems located onboard an aircraft carrier. Aircraft carriers are equipped with two radar systems that provide landing aircraft with critical information and guidance during the landing cycle. Aircraft ACLSs do not use one system or one component; they are an integration of multiple aircraft systems that work together to guide the aircraft safely to a carrier landing. ACOUSTIC—Pertaining to sound or the study of sound. ACTIVE SONAR—Equipment that depends on a transmitted sound wave and the return of an echo. ADF—Automatic direction finder—Provides a bearing to a selected station by using a specific frequency to transmit and receive signals that are processed by compatible equipment. In some cases ADF systems are incorporated as an operational mode of aircraft radio communications systems. ADVANCED NAVIGATION SENSOR—See ANFLIR. AF—Audio frequency. AFCS—Automatic flight control system—In ACLS, is made up of a number of components and systems. A typical AFCS is used to provide the interface between the correction signals received from the datalink and the aircraft flight control surfaces. The AFCS provides switching and signal conditioning, engage logic, command signal limiting, and failsafe interlocks. The failsafe interlocks are AI-1 required to couple and process data link signals to the pitch and bank channels of the AFCS. Automatic synchronization is provided in all three axes. AGM—Air-launched, surface attack, guided missile. AIM—Air-launched, aerial intercept, guided missile. AIP—Anti-surface warfare improvement. AIRFOIL—A part of an aircraft that produces lift or any other desirable aerodynamic effect as it passes through the air. ALFS—Airborne low frequency system—A sonar dipping set that is installed in the MH-60R Seahawk helicopter. The ALFS provides longer detection ranges and improved detection capabilities over previous sonar dipping sets. ALIGNMENT, CARRIER—An INS process that uses SINS to provide aircraft with reference data. SINS data is supplied to the aircraft via a cable assembly or by aircraft data link. See also SINS. ALIGNMENT, GROUND—An INS process that analyzes latitude and longitude data manually entered into the aircraft. ALIGNMENT, INFLIGHT—An INS process that uses inputs and reference data from avionics systems to either preserve an existing alignment or to start a new alignment. During the inflight alignment, air data dead reckoning is used for navigation and for maintaining the current existing position. ALPHA ANGLE—The angular difference between an INS platform heading and true north. ALTIMETER, ABSOLUTE—Uses pulse range-tracking RF energy that measures the surface of terrain clearance below the aircraft. Absolute altimeters are reliable in the altitude range of 0 to 5,000 feet. Absolute altimeters are also known as radar altimeters. ALTIMETER, PRESSURE—An aneroid barometer calibrated to indicate feet of altitude instead of pressure using pointers that are connected by a mechanical linkage to a set of aneroid cells. ALTITUDE, ABSOLUTE—The height above terrain that is computed by subtracting terrain elevation from true altitude. ALTITUDE, CALIBRATED—The indicated altitude corrected for installation or positional error. ALTITUDE, DENSITY—The pressure altitude corrected for temperature. ALTITUDE, INDICATED—The value of altitude that is displayed on the pressure altimeter. ALTITUDE, PRESSURE—The height of the aircraft above the standard datum plane. ALTITUDE, TRUE—The actual vertical distance above mean sea level, measured in feet. ALTITUDE—The vertical distance of a level, a point, or an object measured from a given surface. AM—Amplitude modulation—Any method of varying the amplitude of an electromagnetic carrier to maintain a constant amplitude in the output waveform. AMBIENT NOISE—The naturally occurring noise in the sea and the noise resulting from man’s activity, but excluding self-noise and reverberation. AMPLIFICATION—The process of enlarging a signal, such as voltage or current. Also, the ratio of output magnitude to input magnitude in a device that is intended to produce an output that is an enlarged reproduction of its input. AMPLITUDE—The size of a signal as measured from a reference line to a maximum value above or below the line. Generally used to describe voltage, current, or power. AI-2 AMRAAM, AIM-120—Advanced medium-range air-to-air missile—An all-weather weapon that has beyond-visual-range targeting capability that uses a semi-active guidance system. ANALOG COMPUTER—A type of computer that is designed to meet a special purpose. For example, an analog computer can be used to measure continuous electrical or physical conditions, such as current, voltage, flow, temperature, or pressure. ANFLIR—Advanced navigation forward looking infrared—A self-contained FLIR imaging system that provides IR imagery used by the operator to maneuver and navigate safely at low altitudes and high air speeds. ANGLE-OF-ATTACK—The angle between the chord line and the relative wind. ANOMALY—In magnetic detection systems, a disturbance in the natural magnetic field. ANTENNA, RADAR—Routes the RF energy from the transmitter and radiates the energy in a highly directional beam. The return or received RF energy is routed to the receiver for processing. ANTENNA—A conductor or system of conductors used to collect or radiate RF energy. ANT-SEL—Antenna select—A panel installed in the F/A-18 series aircraft. The ANT-SEL panel is used to electrically change the transmitting/receiving antenna position. ARI—Attitude reference indicator—Designed to assist the aircrew in determining the attitude of the aircraft in instances where the natural horizon is not visible. A typical standby ARI uses a miniature representation of an aircraft that represents the nose (pitch) and wing (bank) attitude. The standby ARI automatically displays ILS steering when the ILS system is turned on by the operator. The ILS steering cues use the miniature representation of the aircraft as a reference. The horizontal needle indicates an ILS approach that is above or below the glideslope. The vertical needle indicates an ILS approach that is right or left of the glideslope. The aircraft is at optimal approach conditions when the horizontal and vertical needles are centered on the standby ARI. ARMAMENT COMPUTER—Installed in the F/A-18 series aircraft. The armament computer provides for the control and release of weapons and is controlled by the mission computer system. ARMAMENT CONTROL PANEL, PILOT—Installed in the P-3 Orion aircraft and provides the pilot with control of all the kill and search stores installed on the aircraft. ARRAY, DETECTOR—A large number of elements closely grouped together to form an array. The elements of this array are packed closely in a regular pattern. This allows the image of the scene to spread across the array like a picture or mosaic. Each detector in the array views a small portion of the scene. The main disadvantage to a detector array is that each element requires a supporting electronic circuit to process the information that the element provides. ASCL—Advanced sonobuoy communication link receiver set—Sonobuoy receiver system that is installed in the P-3 Orion aircraft. ASTROLABE—An inaccurate navigation device that was used by early explorers. ASUW—Anti-surface warfare. ASW—Antisubmarine warfare—Operations conducted against submarines; their supporting forces, and bases. ATC—Automatic throttle control—In ACLS, encompasses a number of different components and subsystems. The ATC system is used during the landing sequence to maintain the appropriate angleof-attack by electrically adjusting the output power of the engines. The ATC also manipulates the engine controls to keep the aircraft traveling at a constant rate of airspeed. AI-3 ATFLIR—Advanced targeting forward looking infrared—Provides the operator with real-time, passive thermal and visible imagery during day and night operations. The ATFLIR system is used to detect, classify, track, and designate both air-to-air and air-to-surface targets of interest. The ATFLIR system also provides the ability to deliver precision-guided ordnance at a stand-off distance outside anti-air weapons envelopes. ATMOSPHERIC STATIC—The result of the electrical breakdown between two masses of oppositely charge particles in the atmosphere. ATTENUATION—The reduction of radio signal strength due to atmospheric or system loss conditions. AUX REL—Auxiliary release. AXIS—A straight line, either real or imaginary, passing through a body, around which the body revolves. AZIMUTH—Angular position or bearing in a horizontal plane, usually measured clockwise from true north. Azimuth and bearing are often used synonymously. AZIMUTH-RANGE INDICATOR—In airborne sonar systems, provides a visual representation of target range and bearing information. In addition, azimuth-range indicators contain controls that are used to adjust display settings, audio settings, and target range thresholds, and initiate operational tests. BAND—The radio frequencies existing between two definite limits and used for a definite purpose; for example, the standard broadcast band extending from 550 to 1600 kHz. BANDWIDTH—The total frequency width of a channel or band of frequencies. BATHYTHERMOGRAPH—A recording thermometer for obtaining a permanent graphical record of water temperature in degrees Fahrenheit or Celsius at different water depths, in feet, as it is lowered or dropped into the ocean. See also SONOBUOY, BATHYTHERMOGRAPH. BATTERY—A device for converting chemical energy into electrical energy. BEACON—A radio or radar signal station that provides navigation and interrogation information for ships and aircraft. BEAMWIDTH—The width of an electromagnetic beam, measured in degrees on an arc that lies in a plane along the axis of propagation, between points of equal field strength. It may be measured in the horizontal or vertical plane. BEARING, RELATIVE—Measured in a clockwise direction using the centerline of the measuring device (antenna, aircraft, etc.) as a reference point. BEARING, TRUE—The angle between true north and the reference line pointed directly at a target. True bearing is measured in the horizontal plane in a clockwise direction from true north. BEARING—Horizontal direction from one point to another, usually measured clockwise from true north. See also AZIMUTH. BINARY—A number system that uses two digits, a 1 and 0, that define a characteristic such as a selection or condition in which there are only two possibilities. BINARY CODE—A method of representing one of the two possible conditions, such as on or off, high or low, or one or zero. BIT—Built-in-test. AI-4 BLACKBODY—An ideal object that absorbs all incident light, and therefore appears perfectly black at all wavelengths. BOLOMETER—A small resistive element used in the measurement of low and medium RF power. It is characterized by a large temperature coefficient of resistance that is capable of being properly matched to a transmission line. BONDING, ELECTRICAL—Process of obtaining the necessary conductivity between the metallic component parts of an aircraft. Bonding successfully brings all items of empennage and internal conduction objects to essentially the same dc voltage level appearing on the basic structure of the fuselage. Bonding is designed to protect aircraft and personnel from the hazards associated with lightning discharges, provide power-current and fault-current return paths, provide stable conductivity for RF currents, prevent the development of ac potentials, prevent shock hazards and reduce the accumulation of static electricity. BONDING, JUMPER—A device used on an aircraft surface, such as control surfaces or flaps, that provides a lightning discharge current path. BOTTOM BOUNCE—That form of sonar sound transmission in which sound rays strike the ocean bottom in deep water at steep angles and are reflected back to the surface and returned, which allows the obtaining of target information at long distances. BOX, ARMAMENT CONTROL—Installed in some P-3 Orion aircraft and incorporates the functions of the pilot armament control panel, wing jettison, and special weapon armament panel. BOX, INTERCONNECTION AFT—Installed in the P-3 Orion aircraft and contains four subassemblies that provide control circuitry for the selection, arming, and release of weapons loaded on wing stations. BOX, INTERCONNECTION FORWARD—Installed in the P-3 Orion aircraft and contains eight subassemblies that provide control circuitry for the selection, arming, torpedo presetting, and release of weapons. BRIDGE CIRCUIT—Any one of a variety of electric circuit networks, one branch of which, the “bridge” proper, connects two points of equal potential, and hence carries no current when the circuit is properly adjusted or balanced. BRUSHES—Sliding contacts, usually made from carbon, that make the electrical connection to the rotating part of a motor or generator. BUS—System that is used to transfer data between components by using low voltage electrical signals. CABLE AND REEL ASSEMBLY—In airborne sonar systems, houses the sonar cable, which is normally between 1,500 to 1,600 feet in length. A typical sonar cable uses a jacketed cable with a metal armor braid as the strength component. Electrical wiring is installed inside the cable assembly and is used to route signals between the transducer and multiplexer. CAMBER—The curve or departure from a straight line (chord line) from the leading edge to the trailing edge of the airfoil. CAPACITANCE—The property of an electrical current that opposes changes in voltage. CAPACITIVE REACTANCE—The opposition, expressed in ohms, offered to the flow of an alternating current by capacitance. CAPACITOR, COAXIAL FEEDTHROUGH—A type of capacitor that works well up to high frequencies. AI-5 CAPACITOR—A device that can be used to short-circuit interference, when it is connected across the source. The function of a capacitor in connection with radio interference is to provide to a lowimpedance radio frequency path across the source. When the reactance of the capacitor is lower than impedance of the power-lines to the source, high-frequency voltages see a capacitor as a shorter path to ground. CARRIER SIGNAL, L1 AND L2—In GPS, are used to transmit position, velocity, and time signals for use by compatible equipment. The L1 carrier signal operates in the 1575.42 MHz frequency range. The L2 carrier signal operates in the 1227.6 MHz frequency range. CAS—Close air support—A mission conducted by aircraft in support of friendly forces on the ground. CATCC—Carrier air traffic control center. CATHODE—A negative electrode. CCA—Carrier-controlled approach—A type of approach radar system used on board aircraft carriers to guide aircraft to safe landings in poor visibility conditions. CCD—Charge coupled device—A light-sensitive integrated circuit that stores and displays the data for an image so that each picture element is converted into an electrical charge that relates to the intensity of a color in the color spectrum. CENTRAL PROCESSING UNIT, COMPUTER—Serves as the main component of the computer system. CENTRIPETAL FORCE—Force that acts on an object moving in a circular path and is directed toward the center around which the object is moving. CFS—Command function selection—In sonobuoys, allows the operator to turn the system on or off, change modes of operation, adjust depths, and change RF channels. CHANNEL—A carrier frequency assignment, usually with a fixed bandwidth. CHORD LINE—An imaginary straight line from the leading edge to the trailing edge of an airfoil. CIRCUIT—The complete path of an electric current. CLADDING—Material used in fiber optics to reduce the loss of light for the core into the surrounding air, reduce scattering loss at the surface of the core, protect fiber from absorbing surface contaminants, and add mechanical strength. CMD—Countermeasures dispenser. CODER-SYNCHRONIZER, IFF—Synchronizes the reception of IFF responses and radar signals so that they will not occur at the same time. COMM CONT—Communications control—Installed in the F/A-18 series of aircraft. The COMM CONT panel is used to provide ground crews with the ability to communicate with the aircrew in the cockpit. COMM—Communications. COMMUTATOR BAR—A device in a dc motor used to change the direction or frequency of the current flow through the windings. COMMUTATOR—A mechanical device that reverses armature connections in motors and generators at the proper instant so that current continues to flow in only one direction. COMPASS ROSE—A circle that is used to represent the horizon and is divided into 360 degrees. COMPOSITE VIDEO—The total video signal that consists of picture information, blanking pulses, and sync pulses. AI-6 COMPRESSION—In sonar, describes the action that occurs when a transducer diaphragm moves outward creating a high-pressure wave. COMPUTER CODE—Code by which data is represented within a computer system; for example, binary coded decimal. COMPUTER, ANALOG—See ANALOG COMPUTER. COMPUTER, DIGITAL—See DIGITAL COMPUTER. COMPUTER—A mechanism or device that performs mathematical operations. There are many different models and sizes of computers designed to perform various functions. However, computers are, generally speaking, all functionally the same no matter what size or purpose they are designed to meet. See also ANALOG COMPUTER and DIGITAL COMPUTER. CONTINUOUS WAVE—Method of transmission that directs a continuously transmitted wave of RF energy at a target. A shift in the frequency when a target moves toward or away from the transmitted RF energy. The shift in frequency is known as the Doppler effect. See also DOPPLER EFFECT. CONTROL SEGMENT—Part of the global positioning network that is responsible for tracking, monitoring, and managing the satellite constellation. CONTROL, GUN SYSTEM—Installed in the F/A-18 series aircraft and provides the means to select, arm, and fire the M61 gun system in A/A and A/G modes. CONTROL, SIGNAL DATA CONVERTOR—Installed in the F/A-18 series aircraft and provides the interface between the armament computer and the loaded weapons and stores. CORE MEMORY, COMPUTER—Consists of tiny doughnut-shaped rings that are made out of ferrite (iron) and are strung on a grid of very thin wires. CORIOLIS FORCE—A false acceleration caused by the Earth rotating around its polar axis as related to inertial space. CORONA DISCHARGE—An electrical discharge brought on by ionization. COSMIC NOISE—The byproduct of the radiation of the stars. Cosmic noise is usually heard in the ultrahigh frequency range and above. COUNTERMEASURES—Devices and/or techniques intended to impair the operational effectiveness of enemy activity. COUPLING, COMPLEX—Interference coupling that is caused by more than one of the following types of transfer: conduction, induction, or radiation. When more than one coupling occurs at the same time, corrective actions, such as shielding, or filtering, can increase the coupling capabilities of another type. COUPLING, CONDUCTIVE—Interference that is coupled from a source to a receiver by metallic conduction. Normally, conductive coupling occurs by way of mutual impedance. COUPLING, INDUCTIVE-CAPACITIVE—Interference caused by high-frequency components that occurs based on the amount of capacitance. The effect of inductive-capacitive coupling depends on the amount of capacitance existing between exposed portions of a noisy circuit and a noise-free circuit. The power transfer capabilities are directly proportional to frequency. COUPLING, INDUCTIVE-MAGNETIC—Interference caused by the variations in a magnetic field. When another parallel conductor is cut by the lines of force of this field, the conductor has a current induced into it. The amount of variation in the current that directly affects variation in the magnetic field surrounding the conductor depends on the nature of the current. As a magnetic field cuts across AI-7 another conductor a voltage replica of its variation is induced into that conductor. Inductive-magnetic coupling can result in serious interference. COUPLING, RADIATION—Interference caused when aircraft wiring acts like an antenna by directing RF energy. Inside-the-aircraft radiation at high frequency and below normally occurs in unshielded or inadequately shielded transmitter antenna leads. COURSE—The intended horizontal direction of travel. CRT—Cathode-ray tube—An electron tube that has an electron gun, a deflection system, and a screen. A CRT is used to display visual electronic signals. CRYSTAL—A natural substance, such as quartz or tourmaline, that is capable of producing a voltage when under physical stress or a physical movement when a voltage is applied. CURRENT—The movement of electrons past a reference point. Also, the passage of electrons through a conductor, which is measured in amperes. DARK CURRENT—Current that flows without any radiant input. DATA HANDLING SYSTEM—Is installed in the MH-60R helicopter and provides for the operator interface, processing, and display of all avionics and weapons systems. DATA LINK—A system that is used for the electronic exchange of secure data between two capable and participating units. DATABASE—Application of a computer that can be used to index and retrieve information. When an operator enters a specific keyword or heading, the computer system calls up the data and displays the information. DC—Direct current—An electric current that flows in one direction only. DCS—Digital communication system—Used to lower the workload of the operator during CAS missions by visually displaying mission information in a text format. DDIs—Digital data indicators—Are installed in the F/A-18 series of aircraft and used to display tactical and situational information to the operator. DEAD RECKONING—Determining the position of an aircraft by estimating the direction and the speed data relative to a previous position. DECIBEL—Unit used to measure the intensity of sound or the power level of an electrical signal. DETECTION—The separation of low frequency (audio) intelligence from the high frequency carrier. DETECTOR—In IR systems, converts the IR radiation signal into an electrical signal that is processed into information used by the operator. DETECTOR, SINGLE—A single detector is scanned across an image so that the detector can view the whole image. A single detector requires one set of supporting circuitry. The single detector system is adequate if real-time information is not needed, or the object of interest is stationary or not moving quickly. DETECTORS, ELEMENTAL—Type of IR detector that averages the portion of the image outside the scene that falls on the detector into a single signal. DETECTORS, IMAGING—Type of IR detector that yields the image directly by responding to a discrete point on the image. DETECTORS, INFRARED—Thermal devices for observing and measuring IR radiation, such as the bolometer, thermopile, pneumatic cell, photocell, photographic plate, and photoconductive cell. IR AI-8 detectors convert IR radiation signals into electrical signals that are processed into information that is used by the operator. DEVICES, SWITCHING—Make abrupt changes in electrical circuits that create transients capable of interfering with operation of radio and other electronic receivers. Examples of switching devices capable of causing serious interference are the relay and the thyratron. DICASS—Directional command activated sonobuoy system—An active sonobuoy that provides active sonar ranging, bearing, and Doppler information on a submerged target. DIELECTRIC—An electrical insulator. DIFAR—Directional frequency analyzing and recording—An improved passive sonobuoy acoustic sensing system that is programmed prior to deployment using EFS circuitry. DIFAR sonobuoys use a directional or omnidirectional antenna to detect sound waves. DIFFUSION—The spread of energy or particles from high concentration to low concentration due to random velocity and scattering. DIGITAL COMPUTER—A type of computer that is used to solve problems by manipulating numerical equivalents of information by using mathematical and logical processes. A typical digital computer may use binary numbers, octal numbers, decimal numbers, etc. as the required numerical equivalent. DIGITAL COMPUTER, GENERAL-PURPOSE—Follows instruction sequences that are read into and stored in memory prior to a calculation being performed. General-purpose digital computers can be altered by inputting a different set of instructions. Since the operation of general-purpose digital computers can be changed with relative ease, they provide far greater usage flexibility than a specialpurpose digital computer. DIGITAL COMPUTER, SPECIAL-PURPOSE—Designed to follow a specific set of instruction sequences that are fixed at the time that they are manufactured. The actual construction of a specialpurpose digital computer must be changed to alter its operational purpose. DIODE—An electron tube that contains two electrodes: a cathode and a plate. Diodes are primarily used as switching devices. DIP ANGLE—In magnetic anomaly detection, is determined by drawing an imaginary line tangent to the Earth’s surface to the point at which the line of force intercepts the surface of the Earth. DIRECTION—Is the position of one point in space relative to another without reference to the distance between them. DISABLING SWITCH FOR ARMAMENT SAFETY CIRCUIT—Installed in the MH-60R Seahawk helicopter and functions as a safety interlock by disabling release and jettison circuits while the aircraft is on deck. DISPLAY, MISSION—Installed in the MH-60R Seahawk helicopter and provides BIT, caution/advisory, and other situation information to the aircrew. DISTANCE—The spatial separation between two points, measured by the length of a line joining them. DISTORTION—The production of an output waveform that is not a true reproduction of the input waveform. Distortion may consist of irregularities in amplitude, frequency, phase, etc. DIVERGENCE—Energy loss caused by the spreading of a sound wave in all directions. The farther a target is from a sonar transducer, the weaker the sound waves will be when they reach that target. DLY—Delay. AI-9 DME—Distance measuring equipment—A transponder-based radio navigation technology used in TACAN that measures slant range distance by timing the propagation delay of an RF signal. DOME CONTROL—In airborne sonar systems, provides the operator with the controls for raising and lowering the sonar transducer. Additionally, the dome control provides indicators for monitoring the sonar transducer and reeling machine. DOPPLER EFFECT—An apparent change in the frequency of a sound wave or electromagnetic wave reaching a receiver when there is relative motion between the source and the receiver. When the frequency of the received waves increases, the target is moving towards the transmitter or transducer. If the frequency of the waves decreases, the target is moving away from the transmitter or transducer. If the frequency remains the same, the target may be stationary or passing through the transmitted wave at a right angle. DRAG—The force that tends to hold an aircraft back. Drag is caused by the disruption of the airflow about the wings, fuselage, and all protruding objects on the aircraft. Drag resists motion as it acts parallel and in the opposite direction in relation to the relative wind. DRIFT—Net change in characteristics of electronic components or parameters, resulting from external or incidental conditions. DROGUE—In sonobuoys, a termination mass that is used to stabilize a hydrophone at a selected depth. DUPLEX—Data transmission method that is capable of both sending and receiving information. See also HALF-DUPLEX and FULL-DUPLEX. DUPLEXER, RADAR—An electronic switch that allows a radar system to use the same antenna to alternate between transmitting and receiving RF energy. A duplexer must be capable of switching between the two cycles rapidly to improve the detection of short range targets. ECHO—In sonar, a sound wave that strikes a target. Or, the RF signal reflected back from a radar target. ECV—Environmental control valve—Used to regulate the aircraft cooling air for the installed components with the ATFLIR pod system. EDDY CURRENT—Induced circulating currents in a conducting material that are caused by a varying magnetic field. EFDS—Electronic flight display system—Installed in the P-3 Orion aircraft and provides the operator with aircraft course, bearing, heading, and distance. The EFDS also displays aircraft pitch and roll commands necessary for the operator to fly a designated course. EFFECT, PHOTOELECTRIC—The electric potential difference across a semiconductor that is caused by a radiant signal. The total current is proportional to the amount of light that falls on a detector. EFFECT, PHOTO-EMISSIVE—The action of radiation that causes the emission of an electron from the surface of the photocathode to the surrounding space. EFFECT, PHOTON—A type of energy-matter interaction in which photons of radiant energy interact directly with the electrons of IR detector material. EFFECT, THERMAL—A type of energy-matter interaction that involves the absorption of radiant energy in an IR detector. EFFECT, TRIBOELECTRIC—Describes the process of generating static electricity by rubbing an object. AI-10 EFS—Electronic function select—A system that provides a sonobuoy with 99 selectable channels, 50 life settings, and 50 depth settings. EHF—Extremely high frequency—The band of frequencies from 30 to 300 GHz. EHSI—Electronic horizontal situation indicator. ELECTRODE—The terminal at which electricity passes from one medium into another, such as in an electrical cell where the current leaves or returns to the electrolyte. ELECTROLYTE—A solution of a substance that is capable of conducting electricity. A typical electrolyte may be in the form of a liquid or a paste. ELECTROMAGNETIC FIELD—The combination of an electric and a magnetic field. ELECTROMAGNETIC RADIATION—The radiation of radio waves into space. ELECTROMAGNETIC SPECTRUM—The range of wavelengths and frequencies over which electromagnetic radiation extends. ELECTROMAGNETIC—Of or relating to the interrelation of electric currents or fields or magnetic fields. ELECTRONIC SWITCH—A circuit that causes a start and stop action or a switching action by electronic means. ELEMENTS, NONLINEAR—Conductors, semiconductors, or solid state devices whose resistance or impedance varies with the voltage that is applied across the device. ELF—Extremely LF—The band of frequencies up to 300 Hz. EMERG—Emergency. EMISSIVITY—The ratio of the energy radiated from a material’s surface to that radiated from a blackbody at the same temperature and wavelength under the same viewing conditions. EMRG JETT—Emergency jettison. EO—Electro-optical—An electronic device that is used to emit, modulate, transmit, or sense light or other wavelengths. EOSU—Electro-optical sensor unit—In the ATFLIR system, a self-contained component designed to protect and seal the ATFLIR optics and laser equipment from moisture, contaminants, and electromagnetic interference. EQUATOR—A great circle that is located midway between the north and south poles. ERROR, HYSTERESIS—In pressure altimeters, a lag in attitude indication due to the elastic properties of the material within the altimeter. This can occur when the aircraft makes a large, rapid altitude change. ERROR, INSTALLATION/POSITION—In pressure altimeters, is caused by airflow around the static pressure measuring ports on an aircraft. The error varies with the type of aircraft, airspeed, and altitude. ERROR, MECHANICAL—In pressure altimeters, is caused by misalignments in gears and levers that transmit the aneroid cell expansion and contraction to the pointers in the altimeter. ERROR, REVERSAL—In pressure altimeters, is caused by inducing false static pressure into the system that can occur during abrupt or huge pitch changes. ERROR, SCALE—In pressure altimeters, is caused by the irregular expansion of the aneroid cells. AI-11 ESD—Electrostatic discharge—A transfer of electrostatic charge between objects at different potentials caused by direct contact or induced by an electrostatic field. ESDS—Electrostatic discharge sensitive—Used to describe components or devices that are sensitive to electrostatic discharge. EXTERNAL PHOTO EFFECT—See EFFECT, PHOTO-EMISSIVE. EYESAFE—In ATFLIR systems, enables the operator to place the laser transceiver into a training mode that simulates all of the tactical aspects of laser employment without emitting any laser energy. The training mode can be used in both air-to-air and air-to-surface modes of operation. F/A—Fighter/Attack. FAC—Forward air controller—An operator on the ground that directs a combat aircraft onto a specific target or location. FACSIMILE—A process, commonly called fax, used to transmit photographs, charts, and other graphic information electronically. Images are scanned by a photoelectric cell and transmitted to the receiver. At the receiver, a signal operates a recorder the reproduces the scanned images. Fax signals may be transmitted by landline or radio. FADING—The variation of signal strength at a receiver due to the difference in phase relationships. FARAD—The basic unit of capacitance. FEEDBACK NETWORK—A component of an oscillator that is used to route parts of the signal back to the frequency determining network to maintain oscillation. FEEDBACK—The return of a portion of the output of a circuit stage to the input of that stage or a preceding stage, such that there is either an increase (regeneration) or a reduction (degeneration) in amplification, depending on the relative phase of the returned signal with the input. FERMI LEVEL—The top of the collection of electron energy levels at absolute zero. FERRITE—A hard and brittle crystalline substance made from a mixture of powdered materials, including iron oxides; it has special magnetic properties of particular value in computers and in many other applications. FERROUS—A material that is related to or contains the element iron. FIBER OPTIC CORE—Located in the center of the optical fiber along the longitudinal axis and is bound by the cladding. The core is the region with the highest index of refraction and is the light photon conducting part of the fiber. FIBER OPTIC—System that transmits light photons through a specifically designed glass medium to send and receive digital information. The light photons in a fiber optic system are created by either a light emitting diode or a laser diode. FIDELITY—The extent to which a system, or a portion of a system, accurately reproduces at its output the essential characteristics of the signal that is impressed upon its input. FILTER, BANDPASS—Used to provide a very high impedance above and below a desired set of frequencies within a specified band. Bandpass filters can be used to decouple the receiver from shock and overload by transmitters operating above and below the receiver band. In addition, bandpass filters are used in multiplexing or to decouple two or more receivers or transmitters using the same antenna. FILTER, BAND-REJECTION—Used to reject or block a band of frequencies from being passed with little to no attenuation. A band-rejection filter consists of inductive and capacitive networks combined and connected to form a definite frequency response characteristic. A band-rejection filter is designed AI-12 to attenuate a specific frequency band and to permit the passage of all frequencies not within this specific band. Band-rejection filters can be arranged as half-section, pi-section and T-section configurations. FILTER, HIGH-PASS—Used to prevent the undesired harmonics from reaching an antenna and being radiated. High-pass filters are useful for isolating high-frequency receiver from the influence of energy of signals of lower frequencies. In symmetrical high-pass filters sections, the total opposition to current flow in is equal to the total opposition to current flow out. FILTER, INDUCTIVE-CAPACITIVE—Are widely used components to reduce both broadband and narrow band interference. Inductive-capacitive filters come in a large variety of types and sizes. FILTER, LOW-PASS—Used in aircraft to power leads coming from interference sources. The lowpass filter prevents the transmission of interference voltages into a wiring harness, and blocks transmission or reception of RF energy above a specified frequency. FILTER, RESISTIVE-CAPACITIVE—An effective arc and transient absorber. A resistive-capacitive filter reduces interference in two ways: by changing the waveform of transients and by dissipating transient energy. FILTER, SPECTRAL—In imaging systems, are used to restrict the light wavelength from reaching an IR detector. FILTER—A selective network of resistors, capacitors, and inductors that offer little opposition to certain frequencies, while blocking or attenuating other frequencies. FIR—Far IR. FIXED NOTCH FILTER—A component of the MIDS that limits the number of transmitted TACAN channels by the upper antenna. FLIR—Forward Looking IR. FLOAT—In sonobuoys, the buoyant section of a sonobuoy that follows the motion of the waves. FLUX DENSITY—The number of magnetic lines of force passing through a given area. FM—Frequency modulation—Angle modulation in which the modulating signal causes the carrier frequency to vary. The amplitude of the modulating signal determines how far the frequency changes, and the frequency of the modulating signal determines how fast the frequency changes. FOV—Field-of-view. FREQUENCY DETERMING NETWORK—A component of an oscillator that is an inductive or capacitive circuit containing a natural or man-made crystal. FREQUENCY MODULATION—Radiates RF energy whose frequency increases and decreases from a fixed reference frequency. In radar, the frequency of the returned signal differs from the radiated signal by the amount of time it takes for the signal to travel to the target and return. FREQUENCY SHIFT KEYING—Frequency modulation somewhat similar to continuous-wave keying in AM transmitters. The carrier is shifted between two differing frequencies by opening and closing a key. FREQUENCY, SOUND WAVE—Determined by counting the number of wavelengths that occur per second. FREQUENCY—The number of Hz (cycles per second) of ac. FULL-DUPLEX—Data transmission method that is capable of transmitting and receiving data simultaneously. AI-13 FUNCTIONS, COMPUTER—All computers can perform the following operations: gather, process, store, disseminate, and display data. G—Gravitational force—A measurement of the type of acceleration that indirectly causes weight. GAMMA—A measure of magnetic intensity. GBU—Guided bomb unit—General-purpose bombs that are retrofitted with a precision guidance package. GCA—Ground-controlled approach—A type of approach radar system that is used in land-based applications. GENERATORS, PRIME—Common plastics and other materials that should be prohibited in an ESD protected work area. GEOMAGNETIC FIELD—The natural magnetic field that surrounds the entire Earth. GHz—Gigahertz. GIGA—A prefix meaning one billion. GIMBAL—A frame in which the gyro wheel spins that allows the gyro wheel to have certain freedom of movement. It permits the gyro rotor to incline freely and retain that position when the support is tipped or repositioned. GPS—Global positioning system—A space-based radio navigation system that provides continuous, all-weather, passive operation anywhere in the world. GRADIENT, NEGATIVE THERMAL—Describes the colder temperatures that occur with the increase in the depth of water. A negative thermal gradient will cause a sound wave to be refracted in a downward angle. GRADIENT, POSITIVE THERMAL—Occurs when the surface temperature of a body of water is cooler than the layers beneath it. This condition rarely occurs, but when a positive thermal gradient occurs it will cause a sound wave to travel at a sharp upward angle. GRADIENT, THERMAL—The direction and the rate of temperature changes in a particular location. GREAT CIRCLE—A plane that intersects through the center of a sphere. GREENWICH MERIDIAN—The prime meridian that passes through Greenwich, England and is used to measure longitude from east or west. GROUND STRAPS, PERSONNEL—Used to ground personnel; should have a minimum resistance of 250,000 ohms and should protect personnel from shock voltages up to 125 volts root mean square. GUIDANCE, ACTIVE—Uses an internal component, such as a radar transmitter, to illuminate a target to provide target distance and speed. GUIDANCE, PASSIVE—Uses the information from the target to determine distance and speed. GUIDANCE, SEMI-ACTIVE—Uses the information from an external source to provide the distance and speed of a target. GYROSCOPE—Mechanical device that contains a spinning mass that is universally mounted allowing it to assume any position in space. Gyroscopes are also commonly known as gyros. HACLC—Harpoon aircraft command launch control—Installed in the P-3 Orion aircraft and is used to provide power, control, and display for the Harpoon missile. HALF-DUPLEX—Data transmission method that transmits or receives data in one direction at a time. HARDWARE, COMPUTER—Electronic and physical components that make up a computer system. AI-14 HARM, AGM-88—High-speed anti-radiation missile—A supersonic, A/G, guided missile designed to detect, attack, and destroy enemy radar systems. HARMONICS—The multiples of the basic or fundamental frequency. Harmonics can be even and odd numbers. Harmonics are expressed as the fundamental frequency times an even or odd number. HAVEQUICK—Mode that provides line-of-sight, jam resistant, ultrahigh frequency, and amplitude modulated band voice communications. HEADING—Horizontal direction in which an aircraft is pointed. HELLFIRE, AGM-114—An A/G, laser guided, subsonic missile with significant antitank capacity. The Hellfire missile was designed to be employed against tanks, structures, bunkers, and slow-moving aircraft. HENRY—The electromagnetic unit of inductance or mutual inductance. HETERODYNE—To mix two different frequencies in the same circuit; they are alternately additive and subtractive, thus producing two beat frequencies, which are the sum of, and difference between, the two original frequencies. HF—High frequency—The frequency bands from 3 to 30 MHz. HORIZONTAL PLANE—A horizontal plane is tangent to the surface of the earth. Every plane parallel to the horizontal plane is likewise a horizontal plane. HUD—Head-up display—In ACLS, displays the same steering cues as the standby ARI but in digital format. The ILS steering cues are referenced to the velocity vector (center of the display) and the artificial horizon. The elevation deviation bar indicates an ILS approach that is above or below the glideslope. The azimuth deviation bar indicates an ILS approach left or right of the glideslope. The aircraft is at the optimum approach conditions when both the elevation and azimuth bar are centered within the velocity vector and the artificial horizon. HYDROPHONE—An acoustic device that receives and converts underwater sound energy into electrical energy. Hz—Hertz—A unit of frequency equal to 1 cycle per second. I/O CHANNEL—The line of communication that carries data into a computer and out to an output or a peripheral device; may be simplex or duplex. See also SIMPLEX and DUPLEX. I/O—Input/Output—Process of transmitting data to a computer, processing the data, and transferring the data to an output or peripheral device. I/P—Identification of positon. IAC—Intercommunication amplifier-control—Installed in the F/A-18 series of aircraft. The IAC is used to amplify audio outputs and to provide the aircrew with communication-, navigation-, and identification-related warnings and advisories. IBIT—Initiated BIT. ICLS—Instrument carrier landing system—In ACLS, the radar system that transmits the glidepath pulse-coded under the K frequency band (KU)-band information from the aircraft carrier to the aircraft. The ICLS is located on board the aircraft carrier and it uses two antennas. One antenna is used to transmit azimuth information, and the other antenna transmits elevation information. Both signals are processed by the receiver-decoder group on the aircraft. IDECM—Integrated defensive electronic countermeasures. IFF—Identification friend or foe—Provides a means for identifying friendly aircraft from enemy aircraft. AI-15 IF—Intermediate frequency—A lower frequency to which an RF echo is converted for ease of amplification. ILS—Instrument landing system—Provides the data for visual steering commands that assist the aircrew for the last 25 miles before touchdown onto the aircraft carrier. The ILS interacts with the ICLS and decodes the azimuth and elevation signals. The decoded signals are provided to the aircrew via the HUD and the standby ARI. IMAGING PROCESSING SYSTEMS—Used to convert the data collected by the detectors into a video display. Data from the detectors is multiplexed so that it can be handled by one set of electronics. The data is then processed so that the information coming from the detectors is in the correct order of serial transference to the video display. The signals from the detectors in many imaging processing systems are amplified and sent to light emitting diode (LED) displays. IMAGING, THERMAL—The use of specialized heat-sensing equipment to detect targets. IMPEDANCE—Measure of electrical opposition in a circuit when current of voltage is applied. INDICATOR, CONTROL—Installed in the MH-60R Seahawk helicopter and is the main interface to access the data handling system. INDICATOR—Provides the operator with a visual display of the returned echo signals that show the bearing, range, or the altitude of a target. INDUCTANCE—The property of a circuit that tends to oppose a change in the existing current flow. INDUCTIVE REACTANCE—The opposition to the flow of an alternating current caused by the inductance of a circuit, expressed in ohms. INERTIA—The physical tendency of a body in motion to remain in motion and a body at rest to remain at rest unless acted upon an outside force. INFRARED MARKER—In ATFLIR, provides a laser reference whose return energy can be seen by personnel equipped with night vision goggles. The IR marker function makes it useful for night attacks where personnel on the ground can confirm that the correct target is being designated. INPUT DEVICE, COMPUTER—Allows an operator to enter data into a computer system. INS—Inertial navigation system—Detects the motion of an aircraft and provides acceleration, velocity, present position, pitch, roll, and true heading data. The INS continuously measures aircraft accelerations to compute aircraft velocity and change in present position. INST—Instantaneous. INTELLIGENCE—The message or information conveyed, as by a modulated radio wave. INTERFACE—A concept involving the specification of the interconnection between equipment or systems. The specifications include the type, quantity, and function of signals to be interchanged via those circuits. Also a device that converts or translates any type of information from one given medium into signals of another given medium; for example, electrical signals to fluidic signals, fluidic signals to electronic signals, etc. INTERFERENCE, BROADBAND—Generated when the current flowing in a circuit is interrupted or varies at a rate that departs radically from a sinusoidal rate. INTERFERENCE, COMMUTATION—A condition that occurs in a series-wound motor. INTERFERENCE, NARROW BAND—Caused by oscillators or power amplifiers in receivers and transmitters that have a poorly shielded local oscillator stage. Narrow band interference can range in severity from a heterodyne whistle in audio output to completely blocked signals. Narrow band AI-16 interference affects single frequencies or spots of frequencies in the tuning range of the affected receiver. INTERFERENCE, SLIDING-CONTACT—A condition that occurs in an alternator and in a serieswound motor. INTERROGATOR, IFF—Responds to coded pulse signals from a challenger. The challenger can be another aircraft, ship, or ground station. INU—Inertial navigation unit. INVERTER—A dc motor with armature taps brought out to slip rings to supply an ac voltage. The alternating output contains some of the interference voltages generated at the direct current end, as well as brush interference at the ac end of the inverter. IONIZATION—Process by which an atom or molecule loses or gains electrons, which results in creation of an electrical charge or change to an existing charge. IONOSPHERE—A layer of electrically charged particles at the top of the Earth’s atmosphere that result from strong solar radiation. IR—Infrared—A Latin word that means “beyond the red”. IR is invisible waves in the portion of the electromagnetic spectrum lying between visible light and radio frequencies. The IR frequency range is from about 300 GHz to 400 THz and between wavelengths of 0.72 and 1,000 micrometers. ISOTHERMAL—A condition where the temperature gradient is equal throughout a layer of a body of water. ISOTHERMAL LAYER—A layer of water in which there is no appreciable change of temperature with depth. JDAM—Joint direct attack munition—General-purpose weapons that are outfitted with INS and GPS guidance sets. The JDAM is used for precision strike capabilities in all weather conditions. KALMAN FILTERING—A statistical estimation that is used by INS to obtain an alignment. The INS platform outputs and reference data are compared to external reference data inputs. Kalman filtering estimates the errors in the compared data to correct platform heading, velocity, and attitude. KHz—Kilohertz. KILO—A prefix meaning one thousand. KNOT—Nautical miles per hour. LASER SPOT TRACKER—In ATFLIR, a subsystem that detects and receives ground or “buddy” designated laser energy. LASER—Light amplification by the stimulated emission of radiation. LATERAL AXIS—The pivot point about which the aircraft pitches. LATITUDE—Angular distance measured north or south of the equator along a meridian, 0 through 90 degrees. LDDI—Left digital data indicator. LDG CHK—Landing check. LEADING EDGE—The front edge or surface of the airfoil. LED—Light emitting diode—A P material and N material (PN)-junction diode that emits visible light when it is forward biased. LF—Low frequency—The band of frequencies from 30 to 300 kHz. AI-17 LIFT—The force that acts in an upward direction to support an aircraft in the air. Lift counteracts the effects of weight and must be greater than or equal to weight if flight is to be sustained. LINE OF FORCE—A line in an electric or magnetic field that shows the direction of the force. LOGIC CIRCUITS—Digital computer circuits used to store information signals and/or to perform logical operations on those signals. LONGITUDE—The angular distance east or west of the Greenwich meridian, measured in the plane of the equator or of a parallel from 0 to 180 degrees. LONGITUDINAL AXIS—The pivot point about which an aircraft rolls. The longitudinal axis runs fore and aft through the length of the aircraft and is parallel to the primary direction of the aircraft. The primary direction of an aircraft is always forward. LOOP ANTENNA—One or more complete turns of wire used with a radio receiver. Loop antennas are also used with direction-finding equipment. LOS—Line-of-sight—The straight-line distance from a reference point to the horizon. Line-of-sight represents the radio and radar VHF and UHF transmission range limits under normal conditions. MACH—The ratio of the speed of a body to the speed of sound in the surrounding medium. Mach is normally used to indicate the speed of sound. MAD—Magnetic anomaly detection—The detection of slight distortions in the earth’s magnetic field. MAGNETIC FIELD—The region in space in which a magnetic force exists, caused by a permanent magnet or as a result of current flowing in a conductor. MAGNETOMETER—A device that is used to detect anomalies in the geomagnetic field. MAGNETRON—A microwave oscillator that uses an electron tube (consisting of a cathode and an anode), a strong axial magnetic field, and resonant cavities. MANUAL ARMT SEL—Manual armament select. MASS STORAGE DEVICE, COMPUTERS—Used to permanently store large amounts of data. MAVERICK, AGM-65—An air-to-surface tactical missile designed for close air support, interdiction, and defense suppression. MC/HYD ISOL—Mission computer/hydraulic isolation—A panel installed in the F/A-18 series aircraft. The MC/HYD ISOL panel is used to turn the power off to either mission computer (1 or 2) installed in the aircraft. MC—Mission computer—Oversees the control and interface of aircraft subsystems and peripheral components. A typical mission computer controls displays, produces weapons launch and release commands, and provides control and option select for various avionics systems. MDG—Multipurpose display group—Installed in the F/A-18 series aircraft and displays all the information required by the operator to carry out the mission. The MDG also is used by maintenance technicians to view the status of various aircraft systems to troubleshoot and isolate system discrepancies. The MDG is made up of the LDDI, RDDI, MPCD, and HUD. MEAN SEA LEVEL—The average of the sea levels of high and low water. MEGA—A prefix meaning one million. MEMORY UNIT—In computers, a device used for storing data for possible use in computation. MEMORY, COMPUTER—Used to temporarily store data and applications in a computer system. MERIDIAN—A great circle drawn through the north and south poles. AI-18 MF—Medium frequency—The band of frequencies from 300 kHz to 3 MHz. MH—Multi-mission helicopter. MHz—Megahertz. MICRO—A prefix meaning one-millionth. MICROMETER—A unit of length equal to 1 millionth of a meter. MICROWAVES—Electromagnetic waves of extremely high frequency (between 300 MHz and 300 GHz). MIDS—Multifunctional information distribution system—Is designed to improve the situational awareness of aircrew and to improve the effectiveness of command and control centers. The MIDS uses secure digital communications to display the location and status of friendly air and surface units. MILE, RADAR—The time it takes for a RF pulse to travel from a radar antenna to a target and back. A radar mile is normally expressed as the time interval of 12.36 microseconds. MILLI—A prefix meaning one-thousandth. MILLIRADIAN—One-thousandth of a radian. MIR—Middle IR. MMCS—Maverick missile control system—Installed in the P-3 Orion aircraft and provides the capability to identify and track up to four separate targets when Maverick missiles are installed on the aircraft. MMR—Multi-mode radar. MODE 1—In IFF systems, provides for the general identification of military aircraft only; has 32 different codes. MODE 2—In IFF systems, identifies specific military aircraft; has 4,096 different codes. MODE 3/A—In IFF systems, is used by both military and civilian air traffic control to identify aircraft; has 4,096 different codes. MODE 4—In IFF systems, a classified secure mode of operation used only by military aircraft. MODE 5—In IFF systems, a secured cryptological mode that uses two methods of data transmission, level 1 and level 2. MODE I—In ACLS, the automatic control mode of operation from aircraft entry point to touchdown on the flight deck. The PALS transmits command and error signals to the aircraft via the aircraft data link system. The approaching aircraft receives command and error signals and automatically corrects the approach to remain in the narrow flight envelope. MODE II—In ACLS, the manual control mode with information relayed to aircraft displays. The operator is provided with cockpit visual indications of command error signals relayed by the PALS. In mode II, the aircrew controls the aircraft by observing the crew station displays. MODE III—In ACLS, a manual control mode with voice communications. The PALS provides a voice link for ship-to-aircraft voice communications to provide talkdown guidance. MODE SELECTIVE INTERROGATION (S)—In IFF systems, a civilian air traffic control capability that reduces the number of unwanted IFF replies. Each aircraft is assigned a unique and permanent mode S address that allows air traffic control to direct interrogations and to send data messages to the desired aircraft. AI-19 MODULATION—The process of varying the amplitude or frequency of a carrier wave in accordance with other signals to convey intelligence. The modulating signal may be an audiofrequency signal, a video signal (as in television), or even electrical pulses or tones to operate relays. MODULATOR—A device that varies the amplitude, frequency, or phase of an ac signal. MODULE—In electronic terminology, a group or cluster of circuits/components usually mounted together. MODULES, EUROCARD—In ATFLIR, are individual circuit cards that are responsible for managing and routing a variety of signals to control the operational functions of the system. For example, some of eurocard modules manage temperature and correct video signals. Eurocard modules are mounted in a cooled card cage within the pod electronics housing. MOTOR, ALTERNATING CURRENT—Can be a source of interference at frequencies other than the output power frequency. MOTORS, DIRECT CURRENT—Can generate voltages that are capable of causing radio interference over a wide band of frequencies. There are three types of dc motors generally used in aircraft: series-wound, shunt-wound, and the compound type. MPCD—Multipurpose color display—In the F/A-18 series aircraft, it is a color display that provides the operator with steering and navigation displays. The MPCD is also the main interface for the digital map system, which provides the operator with a colored map overlay displaying the current position of the aircraft. MULTIPLEXER—In sonar, provides the electrical interface between the sonar set units and a sonar transducer. Or, a system that converts analog and digital signals and transmits the converted signal using a single line or wire. Also known as mux. MULTIPLEXING—A method for simultaneous transmission of two or more signals over a common carrier. MWS—Missile warning set. NATOPS—Naval air training and operating procedures standardization. NATURAL INTERFERENCE—Radio interference caused by natural electrical noise that is separated into atmospheric static, precipitation static, and cosmic noise. NAUTICAL MILE—Distance of measurement that is equivalent to 6,076.10 feet. NAVIGATION, RELATIVE—MIDS mode of operation that improves the navigational accuracy of a host aircraft. Relative navigation compares the location of other MIDS network participants to the current aircraft location by measuring the time it takes for a participant to receive a message. NIR—Near IR. NOISE—Any undesired disturbance within the useful frequency band; also, that part of the modulation of a received signal (or an electrical or electronic signal within a circuit) representing an undesirable effect of transient conditions. NOISE, RANDOM—Consists of impulses that are of irregular shape, amplitude, duration, and recurrence rate. Normally, the source of the random noise is a variable contact between brush and commutator bar or slip ring, or an imperfect contact or poor electrical isolation between surfaces. NULL—A point or position where a variable-strength signal is at its minimum value (or zero). NUTATING—Moving an antenna feed point in a conical pattern so that polarization of the beam does not change. AI-20 OHM—The unit of electrical resistance. OMNIDIRECTIONAL—Transmitting or receiving a signal in all directions. OPAQUE—In optics, not able to be seen through or not having the characteristic of being transparent. OPER—Operate. OPERATING SYSTEM—In computers, are designed to support a computer’s basic functions, such as running applications or controlling I/O devices. OPTICAL FIBER—Consists of a thin cylindrical dielectric (non-conductive) waveguide used to send light energy for communication. Optical fiber is a three-part structure in a fiber optic system that includes a core, a cladding, and a coating. The choice of optical fiber materials and fiber design depends on the operating conditions and the intended application. OPTICAL FIBER COATING—Typically has a 10- to 20-micrometer-thick protective polyimide coating. The coating tolerates extreme temperatures and protects the glass fiber from penetration by moisture and other contaminants. The coating is softer than the glass fiber. OPTICAL LAUNCH—The fiber optic transmitter’s ability to launch the light photons down the fiber optic cabling. OPTICS, FRONT-END—Used to collect the incoming radiant energy to focus an image at detectors. The optics may be reflective, refractive, or a combination of both. Many systems offer a zoom capability, allowing a continuous change in the magnification of an image without changing the focus. Spectral filters are used on front-end optics to restrict the wavelength of light from reaching the detector and interfering with the imaging process. OPTICS, INFRARED—Materials that are specifically designed to filter out all electromagnetic wavelengths in order to focus the reception of IR wavelengths. ORT—Operational readiness test. OSCILLATOR—A component that provides a constant frequency for radio transmitters and receivers. OTPI—On top position indicator—A navigation system that provides the operator with the bearing of a sonobuoy in relation to the aircraft. OUTPUT DEVICE, COMPUTER—Displays computer data and other information to the operator. OVHT—Overheat. P—Patrol. PALS—Precision approach landing system—Designed to be an automatic landing system but has the capability to operate in manual modes. The PALS uses two modes to receive and transmit data: display and voice. The PALS operates in three modes: mode I, mode II, and mode III. PANEL, ARMAMENT CIRCUIT BREAKER—Installed in the P-3 Orion aircraft and supplies power to the armament circuit breakers located on the forward electronics circuit breaker panel. PANEL, KEYFILL—Located on an aircraft, a panel into which cryptological keys can be inputted to allow access to secure functions and systems. PANEL, LANDING GEAR CONTROL—Installed in the F/A-18 series aircraft. The landing gear control panel acts as a safety interlock for the armament control system. When the landing gear is in the down position, the armament release system is disabled. AI-21 PANEL, MASTER ARM CONTROL—Installed in the F/A-18 series aircraft and allows the operator to select the A/A, A/G MASTER modes of operation. The master arm control panel allows the operator to arm the selected weapon and to jettison stores from the aircraft. PARALLEL MODE—Digital transmission method that uses a single wire for each bit of data to be transmitted or received. The data is transmitted via the wires simultaneously. PARASITIC ELEMENT—The passive element of an array antenna array that is connected to neither the transmission line nor the driven element. PASSIVE SONAR—Equipment that uses the sound generated by the target as the source of the echo. PBIT—Periodic BIT. PERIPHERAL DEVICE—Any device that can be connected to a computer for input, output, or communication functions. PERMALLOY—A material used for compensation of magnetic field changes created by the magnetic rotation of an aircraft. PHASE—The angular relationship between two alternating currents or voltages when the voltage or current is plotted as a function of time. When the two are in phase, the angle is zero; both reach their peak simultaneously. When the two are out of phase, one will lead or lag the other; that is at the instant when one of the two is at its peak the other will not be at a peak value. This characteristic is dependent on the phase angle and may differ in polarity as well as magnitude. PHOTOCONDUCTIVITY—The most widely used photon effect. Radiant energy changes the electrical conductivity of the detector element. An electrical circuit is used to measure the change in conductivity. PHOTOCURRENT—A term used to describe electrical current generated by light. PHOTON—A particle of electromagnetic energy or a quantum of light. PHOTOVOLTAIC—See EFFECT, PHOTOELECTRIC. PIEZOELECTRIC EFFECT—Effect of producing a voltage by placing stress, either by compression, expansion, or twisting, on a crystal and conversely, producing a stress in a crystal by applying a voltage to it. PING—A term used to describe the sound wave that is generated by sonar equipment. PITCH—The up and down motion of the nose of the aircraft. The pitch axis runs from the left to the right of the aircraft (wingtip to wingtip). PLANES OF ALTITUDE—Are made up of indicated altitude, calibrated altitude, pressure altitude, density altitude, true altitude, and absolute altitude. POD ELECTRONICS HOUSING—In ATFLIR, provides the mounting and interface for the pod adapter unit, laser transceiver, laser electronics unit, and environmental control valve. POLARIZATION—In electronics, a term used in specifying the direction of the electric vector in a linearly polarized electromagnetic wave as radiated from a transmitting antenna, or as picked up by a receiving antenna. POSITION—A location that is defined by stated or implied coordinates. POWER SUPPLY, RADAR—Provides the radar system with the regulated voltages and signal routing for operation. AI-22 POWER—The rate of doing work or the rate of expending energy. The unit of electrical power is the watt. PRECESSION—The slow movement of the axis of a spinning body around another axis due to a torque acting to change the direction of the first axis. Precession is seen in a circle slowly traced out by the pole of a spinning gyroscope. PRECIPITATION STATIC—A type of interference that occurs during dust, snow, or rain storms. Precipitation static is caused by the corona discharge of high voltage charges from various points on the airframe of an aircraft. PRF—Pulse repetition frequency—In radar, the rate at which pulses are transmitted, given in Hz or pulses per second. PRF is expressed as the reciprocal of PRT. PROCESS CONTROL—Application of a computer that detects a change in a system or process and initiates an immediate corrective action. PROCESSING SYSTEM, ACOUSTIC—Takes the data received from deployed sonobuoys and extracts and converts the information into a usable format. PROGRAMMING LANGUAGE—Used by an operator to design and implement computer applications to solve problems or to meet a specific need. PROPAGATION—Extending the action of, transmitting, or carrying forward as in space or time or through a medium (as the propagation of sound, light, or radio waves). PRT—Pulse repetition time—In radar, the interval between the start of one pulse and the start of the next pulse. PRT is expressed as the reciprocal of PRF. PUBIT—Power-up BIT. PULSE—A momentary sharp surge of electrical voltage, current, or energy. PULSE INTEREFERENCE—Normally generated by pulsed electrical equipment. This type of interference is characterized by a popping or buzzing in an audio output device or by the display of noise spikes on an oscilloscope. The interference level depends upon the pulse severity, repetition frequency, and regularity of occurrence. Pulse interference can cause complete loss of reliability in certain types of navigational beacons. PULSE MODULATION—A method of transmission that uses very short and powerful bursts of RF energy. In radar, the time duration of pulse travel time is measured and used to calculate range. PULSE WIDTH—In radar, the duration of time between the leading and trailing edges of a pulse. PULSE-DOPPLER—Uses the Doppler effect to track the movement of a target by comparing the transmitted and received frequencies. PUSH TO JETT—Push to jettison. PVT—Positon, velocity, and time. Q—Figure of merit of efficiency of a circuit or coil. Or, the ratio of inductive reactance to resistance in servos. Or, the relationship between stored energy (capacitance) and the rate of dissipation in certain types of electric elements, structures, or materials. QUANTUM—A quantity of energy that is proportional in magnitude to the frequency of the radiation that it represents. RADAR—Radio detecting and ranging—A system that operates by transmitting and receive an RF pulse to determine the range, bearing, and altitude of a target. AI-23 RADAR BEACON—In ACLS, receives conically scanned above-the-K-frequency band (Ka) signals from the PALS. The received signals are used to derive the range, angle tracking, and position error for aircraft data link guidance. RADAR, AIR SEARCH—Is used to detect and determine the position, course, and speed of air targets. There are two types of air search radar systems: two-dimensional and three-dimensional. Two-dimensional air search radar systems provide the range and bearing of a target. Threedimensional air search radar systems provide the range, bearing, and altitude of a target. RADAR, AIRBORNE—Is designed to meet the strict weight and space limitations necessary to be installed into aircraft. Airborne radar systems have the same characteristics and performance as land or ship-based systems. RADAR, APPROACH—Used to guide aircraft to a safe landing in all weather conditions. RADAR, MISSILE GUIDANCE—Used to guide a missile to a target. There are three basic type of missile guidance radar: beam-rider, homing, and passive. Beam rider missiles follow a beam of directed continuous wave of RF energy to intercept a target. Homing missiles detect the reflected radar energy off of a target and use it to intercept a target. Passive missiles intercept a target by using the energy radiated from the target. RADAR, SEARCH—Designed to scan a volume of space in order to detect any target within that space. RADAR, SURFACE SEARCH—Used to determine the range and bearing of surface targets or lowflying aircraft. Surface search radar systems generate a pattern for all objects within a line-of-sight distance from the antenna. RADAR, SURFACE SEARCH HEIGHT FINDING—Used to provide accurate range, bearing, and altitude of air targets detected by air search radar systems. RADAR, TRACKING—Also known as fire control radar. Used to provide continuous positional data of a target by using a narrow, circular RF beam. RADIAN—A unit of plane angular measurement that is equal to the angle at the center of a circle subtended by an arc whose length equals the radius or approximately 57.3 degrees. RADIO TERMINAL UNIT—The main physical component of MIDS. RADIOFREQUENCY SPECTRUM—The spectrum of electromagnetic frequencies that are used for communications. The RF spectrum also includes frequencies that are used in radar and other systems. RADIOTELEGRAPH—Device that operates by opening and closing a switch to separate a continuously transmitted wave into dots and dashes based on Morse code. RADIOTELEPHONE—Device better known as a radio and one of the most useful methods of communication in military applications. One of the key disadvantages to a radio is that effective transmission and receiving range is limited. RANGE—The distance of an object from an observer. RANGE, MAXIMUM—In radar, maximum range is dependent on the signal carrier frequency, peak power of the transmitted pulse, pulse repetition frequency, and the sensitivity of the receiver. RANGE, MINIMUM—In radar, minimum range is dependent on the timing, pulse width, and recovery time of the radar system. RAREFACTION—In sonar, the action that occurs when a transducer diaphragm moves inward creating a low-pressure wave. AI-24 RASTER—The illuminated rectangular area scanned by the electron beam on a display. RDDI—Right digital data indicator. RDP—Radar data processor—A general purpose dual processor digital computer that functions as a radar management control, data processor, and a performance monitor. A typical RDP provides target information, display conditions, and BIT commands to the operator. RECEIVER DETECTION—Occurs when the receiver separates an AF from the RF carrier signal by using a detector circuit. RECEIVER OSCILLATOR—A local oscillator in a superheterodyne receiver that generates an RF signal at a given frequency. The local oscillator signal is mixed with another RF signal to produce an IF signal. Depending on the receiver design, the frequency of the local oscillator signal is either above or below the frequency of the RF signal by a frequency equal to the IF. RECEIVER RECEPTION—Occurs when an RF wave passes through the receiver antenna and induces a voltage level into the antenna. RECEIVER REPRODUCTION—Process of converting the electrical signal into an audio output signal. RECEIVER SELECTION—Ability of a receiver to select a particular station frequency from the rest of the frequencies. RECEIVER, FIBER OPTIC—Converts optical signals into electrical signals and routes the signal to the appropriate equipment for processing. RECEIVER, RADAR—Amplifies the weak echoes returned by the target and reproduces the echoes into a video pulse that is routed to an indicator. One of the primary functions of a radar receiver is to convert the frequency of the echo into a lower frequency that is easier to amplify. RECEIVER, RADIO—Equipment that has the capability to decode RF energy into a usable form. RECEIVER, SONOBUOY—Uses radios to receive, demodulate, and amplify sonobuoy transmissions in the very high frequency spectrum bands. A typical sonobuoy receiver system relays acoustic data to other units (ships or aircraft) via a datalink system. The data from a sonobuoy receiver is routed to a spectrum analyzer. RECEIVING-DECODING GROUP—In ACLS, converts the glidepath error signals received from the ship’s ICLS and converts the signals into visual indications for the operator. The receiving-decoding group is also used for the airborne monitoring of ACLS mode I and mode II aircraft carrier approaches. RECOVERY TIME—In radar, the time interval between the end of a transmitted pulse and the time when the echo signals are no longer attenuated by the transmission/reception gap. REELING MACHINE—In airborne sonar systems, a hydraulic hoist that is used to raise and lower the sonar transducer. A typical reeling machine operates at a pressure of 3,000 pounds per square inch. REFLECTION, SOUND—Sound waves transmitted in the sea eventually reach either the surface or the bottom. Since these boundaries are abrupt and very different in sound transmitting properties from the water, sound energy along a path striking these boundaries will be returned (reflected) through the water. Because the density of the water is 800 greater than the density of air nearly all sound waves are reflected to the surface. See also BOTTOM BOUNCE. REFRACTION—The deflection or change in the direction of a wave as they travel through space at different speeds. AI-25 REFRACTION, SOUND—The bending of a sound wave caused by the variations of temperature. A sound beam would travel in a straight line if there were no temperature differences in the water. The path of a sound wave will bend away from an area of high temperature and towards an area of lower temperature. The characteristics of sound refraction can significantly lower the detection range of an undersea target. RELATIVE MOTION—The apparent movement of an object in relation to another object. RELATIVE WIND—The direction of the airstream in relation to the airfoil. RELAY—An electromagnetically operated remote control switch used to switch high current, high voltage, or other critical circuits. Since the relay is used almost exclusively to control large amounts of power with relatively small amounts of power, the relay is always a potential source of interference. This is especially true when the relay is used to control an inductive circuit. RESISTANCE—The opposition a device or material offers to the flow of current. The effect of resistance is to raise the temperature of the material or device carrying the current. RESISTOR—An electrical component that offers resistance to the flow of current. It may be a coil of fine wire or a composition rod. RESOLUTION—In radar, is the ability of a radar system to distinguish between targets. RESOLUTION, BEARING—In radar, is the ability of a radar system to distinguish between two targets that are at the same range but at different bearings. RESOLUTION, RANGE—In radar, is the ability of a radar system to distinguish between two targets that are on the same bearing but at different ranges. RESOLUTION, TARGET—In radar, is the ability of a radar system to distinguish between two targets that are close together in either range or bearing. RESONANCE—The condition in a circuit containing inductance and capacitance, which is resonant at one frequency. REVERBERATION—Multiple reflections of a sound wave. In the ocean reverberations are caused by irregularities in the ocean bottom, surface, and suspended natural matter. Each of the scattered sound waves produces a small echo that may be returned to a transducer. The combinations of these echoes from the cumulative disturbances are reverberations. Under these conditions, an emitted sound wave maybe received as a muffled echo due to sound interference. RF—Radiofrequency—Any frequency of electromagnetic energy capable of propagation into space. The frequencies that fall between 3 kHz and 300 GHz are used for radio communications. ROOT MEAN SQUARE—The most common method of defining the effective voltage or current of an ac wave. ROTOCHUTE—A rotating blade assembly that slows the descent of an airborne deployed sonobuoy to reduce the water-entry shock to the device. RTTY—Radio teletypewriter. See also TELETYPEWRITER. SALINITY—The amount of salt content in seawater. Salinity can affect the travel of a sound wave through a body of water. The higher the salt content, the faster the sound wave will travel through the body of water. SASP—Single advanced signal processor—An acoustic processing system that is installed in the P-3 Orion aircraft. SCANNING SONAR—Sonar that transmits sound pulses in all directions simultaneously. AI-26 SCANNING, BEAM—Consists of two methods: mechanical and electronic. Mechanical beam scanning moves the entire antenna in a desired scanning pattern. Electronic beam scanning changes the scanning pattern by electronically switching a multi-element array or by switching between a set of energy sources. SCANNING, STATIONARY-LOBE—The simplest form of scanning system, which uses a single beam that is stationary in reference to the antenna. SCATTERING—Reflection losses from foreign matter that is suspended in the water. Foreign matter in the water scatters the sound beam and causes the loss of sound energy. The practical result of scattering is the reduction of the echo strength especially at long ranges. SCENE DISSECTION SYSTEM—Used to scan the scene image. Each system has an optimum configuration of detector array and image dissection. Many types of mechanisms can be used to scan the scene. When two axes are scanned, the two scanning motions must be synchronized. In addition, the electronic signal that controls the sampling of the detectors must be synchronized with the scanning motions. SCHULER TUNING (LOOP)—In INS, torques the platform to a position normal to the gravity vector by signals received from a computing loop. The Schuler-tuned loop is a closed loop circuit between the accelerometer, velocity integrator, and stable element. The Schuler-tuned loop prevents large velocity and distance errors caused by misalignment of the stable element. SELECTIVITY—The degree of distinction that a receiver can make between the desired and unwanted signals. SEMI-SYNCHRONOUS ORBIT—An orbit with a period equal to half the average rotational period of the body (Earth) being orbited, and in the same direction as that body’s rotation. SENSITIVITY—The ability of a receiver to reproduce a weak input signal into a useable output signal. In receivers, the greater the sensitivity, the weaker the signal can be reproduced. SENSOR—A component that senses variables and produces a signal derived from that variable. Some examples of sensors are temperature, sound, heat, and light. SERIAL MODE—Digital data transmission method that transmits data one bit at time on a single transmission line. SHF—Super high frequency—The band of frequencies from 3 to 30 GHz. SIDEWINDER, AIM-9 SERIES—Supersonic, A/A weapons with passive IR target detection, proportional navigation guidance, and torque-balanced control systems. SIMPLEX—Data transmission that occurs in one direction (transmit or receive) only. SIMULATION—A computer application used to simulate the operation of any type of system being designed. SINE WAVE—The basic synchronous alternating waveform for all complex waveforms. Also known as a sinusoidal wave. SINGCARS—Single channel ground and airborne radio system—Mode that provides line-of-sight, jam resistant, very high frequency, frequency-modulated band voice communications. SINS—Ship’s INS—Provides ship’s velocity, position, and attitude data to aircraft via a cable assembly or by an aircraft datalink system. SINUSOIDAL—Having a magnitude that varies as the sine of an independent variable. SLEW—To change the position of an indicator mark on a display. AI-27 SMALL CIRCLE—Any intersection of a plane that does not pass through the center of a sphere. SMS—Stores management system—Provides the interface for the selection, control, and release of weapons and stores from aircraft weapons stations and launchers. SOFTWARE—A set of programs and procedures used by a computer to perform a particular function. Software includes compilers, assemblers, operating systems, and so on. SOFTWARE, ASSEMBLER—Used to access, manage, and alter computer hardware architecture. SOFTWARE, COMPILER—Used to transform the source code of one programming language into another computer programming language. SOFTWARE, REAL-TIME PROCESSING—Data is submitted to a computer, and an immediate response is obtained. SONAR—Sound navigation and ranging—Equipment that transmits and receives sound energy propagated through water. SONAR DATA COMPUTER—In airborne sonar systems, a programmed array processor that provides the operator of the dipping sonar. Additionally, the sonar data computer processes signals received from passive and active sonobuoys. SONAR RECEIVER—In airborne sonar systems, generates the transmit signal and receives and processes sonic signals from the transducer for display on the azimuth-range indicator. The sonar receiver also provides the audio output for aural monitoring of acoustic signals. SONAR SYSTEM, AIRBORNE—A lightweight sonar dipping set that is installed in ASW helicopters. SONOBUOY—Cylindrical metal tubes that are about 3 feet in length and 5 inches in diameter and can weigh from 20 to 39 pounds. Sonobuoys are expendable devices that are used to detect, localize, and identify submarines. Sonobuoys fall into three general categories: active, passive, or special purpose. SONOBUOY REFERENCE SYSTEM—The system used to determine the position of deployed sonobuoys relative to aircraft position. SONOBUOY, ACTIVE—Uses a transducer to radiate a sonar pulse that is reflected back from the target. Active sonobuoys use the Doppler effect to calculate both the range and the speed of a target. SONOBUOY, BATHYTHERMOGRAPH—A special purpose sonobuoy that provides a continuous reading of temperature versus depth. The bathythermograph sonobuoy uses a thermistor to provide the operator with temperature data. SONOBUOY, PASSIVE—Are listen-only devices. SONOBUOY, SPECIAL PURPOSE—Are not designed for use in target detection, identification, or localization of a target. SOUND CHANNEL—Condition when two layers of water with near equal temperatures produce a sound channel. Sound between the two layers is refracted by the layers, stays between them, and travels for great distances. SPACE SEGMENT—Consists of the global positioning system constellation that encompasses 21 operational and 3 spare satellites positioned approximately 12,550 miles high in a semi-synchronous orbit around Earth. The satellites are in six orbital planes with three or four operational satellites in each plane. There are a minimum of four satellites observable from anywhere in the world. SPARROW, AIM-7—An all-weather, all-altitude missile that uses a semi-active guidance system to seek out and destroy a target. AI-28 SPECTRUM ANALYZER—In sonar, a high-speed processor that extracts acoustic information from the received signals of active and passive sonobuoys. A spectrum analyzer determines the frequency, amplitude, bearing, Doppler, and range of an acoustic target. SPEED OF LIGHT—Measured at approximately 186,000 statute miles per second. SPREAD SPECTRUM—A technique used by GPS satellites to improve the availability of transmitted signals and to improve the resistance against jamming and natural interference. SRCH PWR—Search power. SSB—Single sideband. STABLE ELEMENT—In INS, mounts in the gimbal structure of an INU unit so that, regardless of aircraft maneuvers, the platform maintains the original orientation. Additionally, the stable element serves as a level mount for the accelerometers. STANDARD DATUM PLANE—A theoretical plane where the atmospheric pressure is 29.92 inches of mercury (Hg) and the temperature is 15 degrees Celsius or 59 degrees Fahrenheit. The standard datum plane is the zero-elevation level of an imaginary atmosphere known as the standard atmosphere. STANDARD LAPSE RATES—A list of altitudes, temperatures, and pressure that was determined by the average readings obtained over a period of years. STATIC ELECTRICITY—Electrical energy at rest. STATUTE MILE—Measurement that is equivalent to 5,280 feet. STBY—Standby. SUBHARMONICS—The submultiple of the fundamental frequency. Subharmonics are expressed in even or odd terms and as a fraction of a number (1/2, 1/4, etc.) of the fundamental frequency. SUPPRESSION—The electrical elimination of an undesired portion of a radio signal. SUS—Signal underwater sound. SWITCH, ARMAMENT SAFETY CIRCUIT DISABLE—Installed in the P-3 Orion aircraft and is used to bypass the landing gear lever switch to permit the operation of the weapons systems when the aircraft is on the ground. SWITCH, ARMAMENT SAFETY OVERRIDE—Installed in the F/A-18 series aircraft and is used to enable the armament control system when the aircraft is on the ground. SWITCHABLE NOTCH FILTER—A component of the MIDS that prevents interference between RF transmissions. SYNCHRONIZER, RADAR—Supplies the signals that time the transmitted pulses, the indicator, and other associated circuits. A synchronizer sets the interval between transmitted pulses to ensure the pulsed RF energy is the proper length. SYSTEM, AIR-TO-AIR MISSILE CONTROL—Installed in the F/A-18 series of aircraft and provides the ability to select and launch A/A missiles, such as the AIM-9 Sidewinder, AIM-7 Sparrow, and the AIM-120 AMRAAM. SYSTEM, AIR-TO-GROUND WEAPONS CONTROL—Installed in the F/A-18 series aircraft and provides the ability to select, launch, fire, or release A/G missiles, bombs, mines, and rockets. SYSTEM, DEFENSIVE COUNTERMEASURES—Used to protect the aircraft from anti-air threats by dispensing flares, chaff, or RF jammers in manual, semiautomatic, or automatic modes of operation. AI-29 SYSTEM, HELLFIRE MISSILE CONTROL—Installed in the MH-60R Seahawk helicopter and provides for the carriage and launch of the AGM-114 Hellfire missile. SYSTEM, JETTISON—Provides the interface and control to jettison selected stores from the aircraft. The jettison system also provides for the selection of an emergency mode that will jettison all stores from the aircraft. SYSTEM, REFRIGERATION—In imaging systems, is required to keep IR detectors cooled to the low temperatures required for effective operation. Refrigeration systems are either open-cycle or closedcycle types. Open-cycle systems require a reservoir of liquefied cryogenic gas. A closed-cycle system recycles the compressed gases to cool the IR detectors. SYSTEM, SONOBUOY LAUNCH—Installed in the MH-60R Seahawk helicopter and is capable of launching and controlling up to 25 sonobuoys. SYSTEM, TORPEDO RELEASE—Installed in the MH-60R Seahawk helicopter and provides for the control and release of up to four torpedoes. TACAN—Tactical Air Navigation—A polar coordinate type radio air-navigation system that provides distance information and bearing information to a compatible station. TACCO—Tactical coordinator. TDC—Throttle designator control. TELETYPEWRITER—A device that transmits and translates letters, figure, and symbols by landlines, radio, or cable, that are entered using a keyboard similar to a typewriter keyboard. TEMPERATURE—The most important factor that can affect the speed of a sound wave traveling in seawater. One degree of temperature change can increase the speed of sound in seawater by 4 to 8 feet per second. TERA—A prefix meaning one trillion. THERMISTOR—A solid-state, semiconducting device whose resistance varies with temperature. THERMOCLINE—The layer in a body of water where the temperature decreases continuously with depth. THRUST—The force developed by the aircraft’s engine or engines. Thrust acts in the forward direction and must be greater than or equal to the effects of drag to begin or sustain flight. THYRATRONS—A gas-filled, grid-controlled, electronic switching tube used mainly in radar modulators. Since the time required to turn a thyratron on is only a few microseconds, the current waveform in a thyratron circuit always has a sharp leading edge. As a result, the waveform is rich in radio interference energy. THz—Terahertz. TIME—In air navigation, either the hour of the day or an elapsed interval. TORPEDO, MK 46—Dual-speed active or active/passive weapon with enhanced target acquisition and improved reliability. TORPEDO, MK 50—A highly capable weapon designed to counter the fast, deep diving, doublehulled nuclear submarine threat. TORPEDO, MK 54—Uses existing torpedo hardware and software and integrates state-of-the-art digital signal processing. TORP—Torpedo. AI-30 TORQUE—A force tending to cause rotational motion; the product of the force applied times the distance from the force to the axis of rotation. TRAILING EDGE—The rear edge or surface of the airfoil. TRANSCEIVER, FIBER OPTIC—Incorporates transmission and reception capabilities into one unit. TRANSDUCER, SONAR—A device that converts an electrical signal into acoustical energy and vice versa. Transducers are watertight and act in the same manner as a loudspeaker when used to transmit a sound and as a microphone when receiving the transmitted echo. A typical transducer uses a diaphragm to create areas of low and high pressure underwater. The mechanical action of the diaphragm creates two types of sound waves: rarefaction and compression. TRANSIENTS, SWITCHING—Result from the make or break of an electrical current and are extremely sharp pulses. The duration and peak value of these pulses depend upon the amount of current and the characteristics of the circuit being opened or closed. The effects of switching transients are shape clicks in the audio output of a receiver and sharp spikes on an oscilloscope trace. Typical sources of sustained switching transients are ignition timing systems, commutators of dc motors, or pulsed navigational lighting. TRANSMITTER, FIBER OPTIC—Converts electrical signals into optical signals and sends it through optical fiber cabling. TRANSMITTER, RADAR—Generates RF energy in the form of short and powerful pulses. Transmitters use oscillators to turn a low-power RF signal into a high-power output signal. TRANSMITTER, RADIO—Equipment that is responsible for generating the proper amount of RF energy to transmit information from one point to another. TRANSPONDER, IFF—Receives the challenge signals from an interrogator unit and transmits the properly coded response. TRIGGERING—In electronics, the initiation of starting action in another circuit; the triggered circuit will then operate for a period of time under its own control. TTY—Teletypewriter. TUNED CIRCUIT—A tuned circuit acts as a filter in a radio communication system by allowing or rejecting specific frequency ranges. UFCD—Upfront control display—A touch sensitive display that provides the keypad, option select, scratch pad, and option displays. UHF—Ultrahigh frequency—The band of frequencies from 300 MHz to 3 GHz. UNIT, LASER ELECTRONICS—In the ATFLIR system, the primary interface between the laser transceiver unit, the aircraft, and the pod. The laser electronics unit interfaces with the aircraft for discrete laser arming signals. UNIT, LASER TRANSCEIVER—In the ATFLIR system, provides the energy for laser generation for the system. UNIT, POD ADAPTER—In the ATFLIR system, provides the mounting and interface for the aircraft, the pod electronics housing, and the ANFLIR sensor. UNIT, PROCESSING INTERFACE—Installed in the MH-60R Seahawk helicopter and provides the interface between the weapons/stores and the primary flight/mission computer and other onboard avionics systems. USER SEGMENT—The equipment used to receive, decode, and process global positioning system information. AI-31 VARACTOR—Consists of a semiconductor diode whose capacitance is varied with the amount of applied voltage. A varactor is used to vary the frequency output of an oscillator. VARICAP—See VARACTOR. VELOCITY—A vector quantity that includes both magnitude (speed) and direction in relation to a given frame of reference. VERTICAL AXIS—Runs from the top to the bottom of the aircraft. The vertical axis runs perpendicular to both the roll and pitch axes. The movement associated with the vertical axis is yaw. VERTICAL PLANE—A vertical plane is perpendicular to the horizontal plane, and is the reference from which bearings are measured. VF—Voice frequency. VHF—Very high frequency—The band of frequencies from 30 to 300 MHz. VLAD—Vertical line array directional frequency and recording—A passive directional sonobuoy that deploys a vertical line array that consists of directional or omnidirectional hydrophones. VLAD sonobuoys are normally deployed in areas that have high ambient noise. VLF—Very LF—The band of frequencies from 3 to 30 kHz. VOR—VHF omnidirectional radio range—A type of short-range radio navigation systems that uses a series of radio beacons. WAVE PROPAGATION—Radiation, as from an antenna, of RF energy into space, or of sound energy into a conducting medium. WAVEGUIDE—Metal tubes or dielectric cylinders capable of propagating electromagnetic waves through their interiors. The dimensions of these devices are determined by the frequency to be propagated. Metal guides are usually rectangular or circular in cross section; they may be evacuated, air filled, or gas filled, and may or may not be pressurized. Dielectric guides consist of solid dielectric cylinders surrounded by air. WAVELENGTH—Distance traveled by a wave during the time interval of one complete cycle. It is equal to the velocity divided by the frequency. WEIGHT—The force of gravity that acts downward on the aircraft, and everything in the aircraft, such as crew, fuel, and cargo. WING FORM—A digital outline of an aircraft that identifies type, weapons station, number, and status of weapons that are loaded on the aircraft. WIP—Weapons insertion panel—Component of the F/A-18 armament computer that is used to enter weapon type and fuzing codes for each loaded weapon station. The weapons code entered for each loaded station must match the loaded weapon. In addition, the nose/tail fuze code must be compatible. If these conditions are not met the aircraft will not allow the weapon to fire or release. WOW—Weight-on-wheels—A switch that indicates that the aircraft is on the ground. WPN—Weapon. WRA—Weapons replaceable assembly. XIR—Extreme IR. YAW—The change in aircraft heading to the right or to the left of the primary direction of the aircraft. ZERO COEFFICIENT—A lack of relationship between one property and another property. AI-32 APPENDIX II SYMBOLS, FORMULAS, AND TABLES Figure AII-1 — Electrical symbols. AII-1 Figure AII-1 — Electrical symbols (continued). AII-2 Figure AII-1 — Electrical symbols (continued). AII-3 Figure AII-1 — Electrical symbols (continued). AII-4 Figure AII-1 — Electrical symbols (continued). AII-5 Figure AII-1 — Electrical symbols (continued). AII-6 Figure AII-1 — Electrical symbols (continued). AII-7 Figure AII-1 — Electrical symbols (continued). AII-8 Table AII-1 — Common Electrical Formula Symbols Electrical Symbol General Description I Current is measured in amperes E Voltage is measured in volts R Resistance is measured in ohms P Power is measured in watts L Inductance is measured in henrys X Reactance is measured in ohms t Measure of time EP Voltage in a transformer primary ES Voltage in a transformer secondary NP Number of turns in a transformer primary NS Number of turns in a transformer secondary Eave Value of average voltage Emax Value of maximum voltage Eeff Value of effective voltage F Measure of magnetomotive force ᶲ (flux) Measure of magnetic flow R (reluctance) Measure of magnetic opposition H Measure of magnetic force intensity dB Measure of intensity (sound or electrical) AII-9 Figure AII-2 — Common electrical calculations formula wheel. AII-10 Ohm’s Law for Direct Current Circuits I= E P P = = � R E R E P E2 R= = 2= I I P E = IR = P = √PR I E2 P = EI = = I2 R R Resistors in Series R T = R1 + R 2 … Resistors in Parallel Two resistors: R1 R2 RT = 1 R + R2 More than two: 1 1 1 = + +⋯ RT R1 R 2 Resistive-Inductance (RL) Circuit Time Constant L (in henrys) = t (in seconds), or R (in ohms) L (in microhenrys) = t (in microseconds) R (in ohms) Resistive-Capacitive (RC) Circuit Time Constant R (ohms) × C (farads) = t (seconds) R (megohms) × C (microfarads) = t (seconds) R (ohms) × C (microfarads) = t (microseconds) AII-11 R (megohms) × C (picofarads) = t (microseconds) Capacitors in Series Two capacitors: CT = C1 C2 C1 + C2 More than two: 1 1 1 = + +⋯ CT C1 C2 Capacitors in Parallel CT = C1 + C2 + ⋯ Capacitive Reactance XC = 1 2πfC Impedance in an RC Circuit (Series) Z = �R2 + (XC )2 Inductor in Series LT = L1 + L2 + ⋯ (No coupling between coils) Inductors in Parallel Two inductors: LT = L1 L2 (No coupling between coils) L1 + L2 More than two: 1 1 1 = + + ⋯ (No coupling between coils) LT L1 L2 AII-12 Inductive Reactance XL = 2πfL Q of a Coil Q= XL R Impedance of an RL Circuit (Series) Z = �R² + (XL )² Impedance with R, C, and L in Series Z = �R² + (XL − XC )² Parallel Circuit Impedance Z= Z1 Z2 Z1 + Z2 Sine-Wave Voltage Relationships Average value: Eave = 2 × Emax = 0.637Emax π Effective or rms value: Eeff = Emax √2 = Emax = 0.707Emax = 1.11Eave 1.414 Maximum value: Emax = �2 (Eeff) = 1.414Eeff = 1.57Eave Voltage in an alternating circuit: E = IZ = P I × PF AII-13 Current in an alternating circuit: I= P E = E × PF Z Power in Alternating Current Circuit Apparent power: P = EI True power: P = EI cos θ = EI × PF Power factor: P = cos θ EI true power cos θ = apparent power PF = Transformers Voltage relationship: Np Ep Ns = or Es = Ep × Es Ns Np Current relationship: Ip Ns = Is Np Induced voltage: Eeff = 4.44 × BAfN × 10−8 Turns ratio: Np Zp = � Ns Zs Secondary current: Is = Ip × AII-14 Np Ns Secondary voltage: Es = Ep × Ns Np Three-phase Voltage and Current Relationships With wye connected windings: Eline = √3 (Ecoil ) = 1.732Ecoil Iline = Icoil With delta connected windings: Eline = Ecoil Iline = 1.732Icoil With wye or delta connected winding: Pcoil = Ecoil Icoil Pt = 3Pcoil Pt = 1.732Eline Iline (To convert to true power, multiply by 𝐜𝐜𝐜𝐜𝐜𝐜 𝛉𝛉) Resonance At resonance: XL = XC Resonant frequency: F0 = 1 2π√LC Series resonance: Z (at any frequency) = R + j (XL − XC ) Z (at resonance) = R AII-15 Parallel resonance: Zmax (at resonance) = XL XC XL2 L = = QXL = CR R R Bandwidth: ∆= F0 R = Q 2πL Tube Characteristics Amplification factor: ∆ep (i constant) ∆eg p µ= µ = g m rp Alternating current plate resistance: ∆ep (e constant) ∆ip g rp = Grid-plate transconductance: gm = ∆ip (e constant) ∆eg p Decibels NOTE Wherever the expression “log” appears without a subscript specifying the base, the logarithmic base is understood to be 10. Power ratio: dB = 10 log P2 P1 Current and voltage ratio: dB = 20 log AII-16 I2 �R 2 I1 �R1 dB = 20 log E2 �R1 E1 �R 2 NOTE When R1 and R2 are equal they may be omitted from the formula. When reference level is 1 milliwatt: dBm = 10 log P (when P is in watts) 0.001 Synchronous Speed of a Motor rpm = 120 × frequency number of poles Wavelength wavelength (in meters) = λ= 300 frequency (in megahertz) 300 f MHz AII-17 BRIDGE CIRCUIT CONVERSION FORMULAS Pi to Tee R1′ = R1 R 2 R1 + R 2 + R 3 R 3′ = R2R3 R1 + R 2 + R 3 R 2′ = Tee to Pi R1 = R2 = R3 = R1 R 3 R1 + R 2 + R 3 R1′ R 2′ + R 2′ R 3′ + R1′ R 3′ R3 R1′ R 2′ + R 2′ R 3′ + R1′ R 3′ R2 R1′ R 2′ + 𝑅𝑅2′ 𝑅𝑅3′ + 𝑅𝑅1′ 𝑅𝑅3′ R1 AII-18 Calculating RT for Bridge 1. Redraw. 2. Convert Pi network made up of resistors R3, R4, R5 to Tee network made up of R3’, R4’, R5’. R 3′ = R3R5 R3 + R4 + R5 R 5′ = R3R4 R3 + R4 + R5 R 4′ = R4R5 R3 + R4 + R5 AII-19 3. Redraw circuit. 4. Simplify circuit by combining. 5. Simplify again. 6. Solve for RT. R1′ = R1 + R 3′ R 2′ = R 2 + R 4′ R 6′ = R1′ R 2′ R1′ + R 2′ R T = R 6′ + R 5′ AII-20 Table AII-2 ─ Law of Exponents Numbers Powers of Ten 1012 1,000,000,000,000 9 1,000,000,000 10 1,000,000 106 Prefixes Symbol tera T giga G mega M 10 3 kilo k 100 10 2 hecto h 10 10 deka da deci d 1,000 -1 0.1 10 0.01 10-2 centi c 10 -3 milli m 10 -6 micro µ 10 -9 nano n 10 -12 pico p 10 -15 femto f 0.000000000000000001 10 -18 atto a 0.001 0.000001 0.000000001 0.000000000001 0.000000000000001 To multiply like (with same base) exponential quantities, add the exponents. In the language of algebra the rule is 𝐚𝐚𝐦𝐦 × 𝐚𝐚𝐧𝐧 = 𝐚𝐚𝐦𝐦 + 𝐧𝐧 . 𝟏𝟏𝟏𝟏𝟒𝟒 × 𝟏𝟏𝟏𝟏𝟐𝟐 = 𝟏𝟏𝟏𝟏𝟒𝟒 + 𝟐𝟐 = 𝟏𝟏𝟏𝟏𝟔𝟔 𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 × 𝟖𝟖𝟖𝟖𝟖𝟖. 𝟐𝟐 = 𝟑𝟑 × 𝟏𝟏𝟏𝟏−𝟑𝟑 × 𝟖𝟖. 𝟐𝟐𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟐𝟐 = 𝟐𝟐𝟐𝟐. 𝟕𝟕𝟕𝟕𝟕𝟕 × 𝟏𝟏𝟏𝟏−𝟏𝟏 = 𝟐𝟐. 𝟒𝟒𝟒𝟒𝟒𝟒𝟒𝟒 To divide exponential quantities, subtract the exponents. In the language of algebra the rule is: 𝐚𝐚𝐦𝐦 = 𝐚𝐚𝐦𝐦−𝐧𝐧 𝐨𝐨𝐨𝐨 𝟏𝟏𝟏𝟏𝟖𝟖 ÷ 𝟏𝟏𝟏𝟏𝟐𝟐 = 𝟏𝟏𝟏𝟏𝟔𝟔 𝐧𝐧 𝟑𝟑, 𝟎𝟎𝟎𝟎𝟎𝟎 ÷ 𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 = 𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 = (𝟑𝟑 × 𝟏𝟏𝟏𝟏𝟑𝟑 ) ÷ (𝟏𝟏. 𝟓𝟓 × 𝟏𝟏𝟏𝟏−𝟐𝟐 ) = 𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟓𝟓 = 𝟐𝟐𝟐𝟐𝟐𝟐, 𝟎𝟎𝟎𝟎𝟎𝟎 To raise an exponential quantity to a power, multiply the exponents. In the language of algebra: (𝐱𝐱 𝐦𝐦 )𝐧𝐧 = 𝐱𝐱 𝐦𝐦𝐦𝐦 (𝟏𝟏𝟏𝟏𝟑𝟑 )𝟒𝟒 = 𝟏𝟏𝟏𝟏𝟑𝟑 ×𝟒𝟒 = 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 𝟐𝟐, 𝟓𝟓𝟓𝟓𝟓𝟓𝟐𝟐 = (𝟐𝟐. 𝟓𝟓 × 𝟏𝟏𝟏𝟏𝟑𝟑 )𝟐𝟐 = 𝟔𝟔. 𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟔𝟔 = 𝟔𝟔, 𝟐𝟐𝟐𝟐𝟐𝟐, 𝟎𝟎𝟎𝟎𝟎𝟎 Any number (except zero) raised to the zero power is 1. In the language of algebra: 𝐱𝐱 𝟎𝟎 = 𝟏𝟏 𝐱𝐱 𝟑𝟑 ÷ 𝐱𝐱 𝟑𝟑 = 𝟏𝟏 𝟏𝟏𝟏𝟏𝟒𝟒 ÷ 𝟏𝟏𝟏𝟏𝟒𝟒 = 𝟏𝟏 AII-21 Any base number with a negative exponent is equal to 1 divided by the base with an equal positive exponent. In the language of algebra: 𝐱𝐱 −𝐚𝐚 = 𝟏𝟏 𝐱𝐱 𝐚𝐚 𝟏𝟏 𝟏𝟏 = 𝟐𝟐 𝟏𝟏𝟏𝟏 𝟏𝟏𝟏𝟏𝟏𝟏 𝟓𝟓 𝟓𝟓𝟓𝟓−𝟑𝟑 = 𝟑𝟑 𝐚𝐚 𝟏𝟏 (𝟔𝟔𝟔𝟔)−𝟏𝟏 = 𝟔𝟔𝟔𝟔 To raise a product to a power, raise each factor of the product to that power. 𝟏𝟏𝟏𝟏−𝟐𝟐 = (𝟐𝟐 × 𝟏𝟏𝟏𝟏)𝟐𝟐 = 𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟐𝟐 𝟑𝟑, 𝟎𝟎𝟎𝟎𝟎𝟎𝟑𝟑 = (𝟑𝟑 × 𝟏𝟏𝟏𝟏𝟑𝟑 )𝟑𝟑 = 𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟗𝟗 To find the nth root of an exponential quantity, divide the exponent by the index of the root. Therefore, 𝐦𝐦 the nth root of 𝐚𝐚𝐦𝐦 = 𝐚𝐚 ⁄𝐧𝐧 . 𝟑𝟑 �𝐱𝐱 𝟔𝟔 = 𝐱𝐱 𝟔𝟔� 𝟐𝟐 = 𝐱𝐱 𝟑𝟑 �𝟔𝟔𝟔𝟔 × 𝟏𝟏𝟏𝟏𝟑𝟑 = 𝟒𝟒 × 𝟏𝟏𝟏𝟏 = 𝟒𝟒𝟒𝟒 Joint Electronics Type Designation System The Joint Electronics Type Designation System (JETDS) was developed to standardize the identification of electronic material and equipment. There is a three letter designation assigned to complete sets of electronic equipment that describes where they are used, the type of equipment, and purpose of that equipment. For example, the designator APG would represent piloted aircraft (A), radar (P), fire control or searchlight directing (G), or an airborne fire control radar system. The three letter system is provided as a reference to explain aircraft electronics systems designations and is shown on the following page in Table AII-3. AII-22 Table AII-3 — JETDS Installation Class Type of Equipment Purpose A Piloted aircraft A Invisible light, heat radiation A Auxiliary assembly B Underwater mobile, submarine B Communications security B Bombing C Cryptographic C Carrier (electronic wave/signal) C Communications (receiving and transmitting) D Pilotless carrier D Radiac D Direction finder, reconnaissance and surveillance F Fixed ground E Laser E Ejection and/or release G General ground use F Fiber optics G Fire control or searchlight directing K Amphibious G Telegraph or teletype H Recording/reproducing M Mobile (ground) I Interphone and public address K Computing P Portable J Electromechanical or inertial wire covered M Maintenance/test assemblies S Water K Telemetering N Navigational aids T Transportable (ground) L Countermeasures Q Special or combination U General utility M Meteorological R Receiving/passable detection V Vehicular (ground) N Sound in air S Detecting/range and bearing, search W Water surface and underwater combined P Radar T Transmitting Z Piloted-pilotless airborne vehicles combined Q Sonar and underwater sound W Automatic flight or remote control R Radio X Identification and recognition S Special or combination Y Surveillance (search, detect, and multiple target tracking ) and control T Telephone (wire) Z Secure V Visual and visible light W Armament (peculiar not already covered) X Facsimile or television Y Data processing or computer Z Communications AII-23 Table AII-4 — Greek Alphabet Name Capital Lower Case Designation Alpha Α α Angles, coefficient of thermal expansion Beta Β β Angles, flux density Gamma Γ γ Conductivity Delta Δ δ Variation of quantity, increment Epsilon Ε ε Base of natural logarithms (2.71828) Zeta Ζ ζ Impedance, coefficient, efficiency, magnetizing force Eta Η η Hysteresis coefficient, efficiency, magnetizing force Theta Θ θ Phase angle Iota Ι ι Kappa Κ κ Dielectric constant, coupling constant, susceptibility Lambda Λ λ Wavelength (lower case) Mu Μ μ Permeability, micro, amplification factor Nu Ν ν Reluctivity Xi Ξ ξ Omicron Ο ο Pi Π π 3.1416 Rho Ρ ρ Resistivity (lower case) Sigma Σ σ Summation symbol (capital) Tau Τ τ Time constant, time-phase displacement Upsilon Υ υ Phi Φ φ Chi Χ Χ Psi Ψ Ψ Dielectric flux, phase difference Omega Ω ω Ohms (capital), angular velocity (2 π f) Angles, magnetic flux AII-24 APPENDIX III REFERENCES NOTE Although the following references were current when this NRTC was published, their continued currency cannot be assured. When consulting these references, keep in mind that they may have been revised to reflect new technology or revised methods, practices, or procedures; therefore, you need to ensure that you are studying the latest references. If you find an incorrect or obsolete reference, please use the Rate Training Manual User Update Form provided at the end of each chapter to contact the CNATT Rate Training Manager. Chapter 1 Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012. Navy Electricity and Electronics Training Series, Module 17—Radio-Frequency Communications Principles, NAVEDTRA 14189A, Center for Surface Combat Systems, Dahlgren, VA, April 2013. Chapter 2 Air Navigation, NAVAIR 00-80V-49, Office of the Chief of Naval Operations, Washington, DC, 15 March 1983. Electronics Installation and Maintenance Book (EIMB), General, NAVSEA SE000-00-EIM-100, Commander, Naval Sea Systems Command, Washington, DC, April 1983. Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. Navy Electricity and Electronics Training Series, Module 17—Radio-Frequency Communications Principles, NAVEDTRA 14189A, Center for Surface Combat Systems, Dahlgren, VA, April 2013. Chapter 3 Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. Navy Electricity and Electronics Training Series, Module 18—Radar Principles, NAVEDTRA 14190A, Center for Surface Combat Systems, Dahlgren, VA, April 2013. Chapter 4 Aviation Electricity and Electronics, Undersea Warfare, NAVEDTRA 14340, Center for Naval Aviation Technical Training, Pensacola, FL, April 2003. Integrated Sensor Station 1 and 2, Update III and Block Mod Upgrade Program, Navy Model P-3C Aircraft, NAVAIR 01-75PAC-2-15, Commander, Naval Air Systems Command, Patuxent River, MD, 1 May 1993, Change 16, 15 September 2013. AIII-1 Maintenance Instructions, Organizational, Integrated Flight Station Systems, Navy Model P-3C Aircraft, NAVAIR 01-75PAC-2-9, Commander, Naval Air Systems Command, Patuxent River, MD, 1 May 1993, Change 16, 1 September 2013. Sonobuoys, Navy Models P-3 (Series), SH-60 (Series), S-3B, P-8A Aircraft and All Navy Vessels, NAVAIR 28-SSQ-500-1, Commander, Naval Air Systems Command, Patuxent River, MD, Revision 2, 1 October 2011. Chapter 5 Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. Maintenance Instructions, Organizational, Integrated Flight Station Systems, Navy Model P-3C Aircraft, NAVAIR 01-75PAC-2-9, Commander, Naval Air Systems Command, Patuxent River, MD, 1 May 1993, Change 16, 1 September 2013. NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012. Chapter 6 Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. Interactive Electronic Technical Manual (IETM), A1-F/A-18E/F/G. NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012. Chapter 7 Airborne Weapons/Stores Loading Manual, Navy Model F/A-18E/F and EA-18G Aircraft, A1-F18EALWS-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 January 2014. Airborne Weapons/Stores Loading Manual, Navy Model MH-60R Helicopter, A1-H60RA-LWS-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2014. Airborne Weapons/Stores Loading Manual, Navy Model P-3 Aircraft, NAVAIR 01-75PAC-75, Commander, Naval Air Systems Command, Patuxent River, MD, 1 September 2014. Aviation Ordnanceman, NAVEDTRA 14313A, Center for Naval Aviation Technical Training, Pensacola, FL, March 2011. Chapter 8 Installation and Repair Practices, Aircraft Fiber Optic Cabling, NAVAIR 01-1A-505-4, TO 1-1A-14-4, TM 1-1500-323-24-4, Commander, Naval Air Systems Command, Patuxent River, MD, 13 August 2012. Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. Navy Electricity and Electronics Training Series, Module 22—Digital Computing, NAVEDTRA 14194A, Center for Surface Combat Systems, Dahlgren, VA, May 2013. Navy Electricity and Electronics Training Series, Module 24—Fiber Optics, NAVEDTRA 14196A, Center for Surface Combat Systems, Dahlgren, VA, June 2014. AIII-2 Chapter 9 Aeronautical Information Manual, U.S. Department of Transportation, Federal Aviation Administration, Washington, DC, 3 April 2014. CV NATOPS Manual, NAVAIR 00-80T-105, Commander, Naval Air Systems Command, Patuxent River, MD, 15 September 2013. Fundamentals of Aviation and Space Technology, Institute of Aviation, University of Illinois, Savoy, IL, 1974. Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D. NATOPS Flight Manual, Navy Model, F/A-18A/B/C/D 161353 and Up Aircraft, A1-F18AC-NFM-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012. NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012. Chapter 10 Electronics Installation and Maintenance Book (EIMB), General Maintenance, NAVSEA SE000-00EIM-160, Commander, Naval Sea Systems Command, Washington, DC, January 1981. Electronics Installation and Maintenance Book (EIMB), General, NAVSEA SE000-00-EIM-100, Commander, Naval Sea Systems Command, Washington, DC, April 1983. Installation and Repair Practices, Volume 1, Aircraft Electric and Electronic Wiring, NAVAIR 01-1A505, TO 1-1A-14, TM 1-1500-323-24-1, Commander, Naval Air Systems Command, Patuxent River, MD, 15 April 2014. AIII-3 APPENDIX IV Answers to End of Chapter Questions Chapter 1 ─ Communications 1-1. B 1-13. D 1-25. B 1-2. C 1-14. A 1-26. D 1-3. D 1-15. B 1-27. A 1-4. A 1-16. A 1-28. D 1-5. B 1-17. D 1-29. C 1-6. A 1-18. B 1-30. B 1-7. C 1-19. C 1-31. A 1-8. D 1-20. B 1-32. D 1-9. A 1-21. C 1-33. D 1-10. D 1-22. D 1-34. A 1-11. B 1-23. A 1-35. C 1-12. C 1-24. C 1-36. C Chapter 2 ─ Navigation 2-1. B 2-8. A 2-15. D 2-2. C 2-9. C 2-16. C 2-3. A 2-10. D 2-17. B 2-4. D 2-11. A 2-18. C 2-5. C 2-12. C 2-19. A 2-6. B 2-13. B 2-20. C 2-7. D 2-14. C AIV-1 Chapter 3 ─ Radar 3-1. C 3-21. D 3-41. C 3-2. B 3-22. D 3-42. A 3-3. D 3-23. A 3-43. D 3-4. A 3-24. C 3-44. A 3-5. B 3-25. D 3-45. D 3-6. D 3-26. A 3-46. C 3-7. C 3-27. B 3-47. A 3-8. C 3-28. C 3-48. B 3-9. A 3-29. B 3-49. C 3-10. B 3-30. A 3-50. A 3-11. D 3-31. D 3-51. C 3-12. A 3-32. A 3-52. B 3-13. C 3-33. D 3-53. A 3-14. D 3-34. C 3-54. D 3-15. C 3-35. A 3-55. D 3-16. A 3-36. C 3-56. C 3-17. D 3-37. D 3-57. B 3-18. B 3-38. B 3-58. D 3-19. C 3-39. A 3-59. C 3-20. B 3-40. B AIV-2 Chapter 4 ─ Antisubmarine Warfare 4-1. A 4-16. B 4-31. C 4-2. C 4-17. D 4-32. D 4-3. B 4-18. B 4-33. C 4-4. A 4-19. C 4-34. A 4-5. B 4-20. B 4-35. C 4-6. C 4-21. B 4-36. B 4-7. B 4-22. C 4-37. A 4-8. D 4-23. A 4-38. C 4-9. A 4-24. B 4-39. A 4-10. B 4-25. D 4-40. B 4-11. C 4-26. B 4-41. A 4-12. B 4-27. A 4-42. C 4-13. A 4-28. C 4-43. D 4-14. C 4-29. D 4-44. A 4-15. D 4-30. A Chapter 5 ─ Indicators 5-1. A 5-7. A 5-13. C 5-2. C 5-8. D 5-14. B 5-3. D 5-9. B 5-15. A 5-4. B 5-10. C 5-16. C 5-5. C 5-11. A 5-17. D 5-6. D 5-12. B 5-18. C AIV-3 Chapter 6 ─ Infrared 6-1. B 6-11. C 6-21. B 6-2. C 6-12. D 6-22. D 6-3. D 6-13. B 6-23. D 6-4. A 6-14. C 6-24. B 6-5. D 6-15. C 6-25. C 6-6. A 6-16. A 6-26. D 6-7. D 6-17. B 6-27. C 6-8. A 6-18. B 6-28. D 6-9. B 6-19. C 6-29. A 6-10. A 6-20. D 6-30. D Chapter 7 ─ Weapons Systems 7-1. A 7-11. C 7-21. A 7-2. C 7-12. B 7-22. C 7-3. B 7-13. D 7-23. D 7-4. D 7-14. B 7-24. D 7-5. B 7-15. A 7-25. B 7-6. D 7-16. C 7-26. D 7-7. A 7-17. D 7-27. A 7-8. D 7-18. B 7-28. D 7-9. B 7-19. B 7-10. A 7-20. C AIV-4 Chapter 8 ─ Computers 8-1. D 8-15. B 8-29. A 8-2. C 8-16. C 8-30. B 8-3. A 8-17. A 8-31. D 8-4. D 8-18. D 8-32. B 8-5. C 8-19. B 8-33. A 8-6. C 8-20. B 8-34. C 8-7. B 8-21. C 8-35. B 8-8. A 8-22. D 8-36. A 8-9. D 8-23. B 8-37. B 8-10. B 8-24. C 8-38. C 8-11. A 8-25. B 8-39. B 8-12. D 8-26. A 8-40. C 8-13. C 8-27. C 8-14. B 8-28. D Chapter 9 ─ Automatic Carrier Landing System/Instrument Landing System 9-1. A 9-10. A 9-19. B 9-2. B 9-11. D 9-20. A 9-3. D 9-12. D 9-21. B 9-4. A 9-13. B 9-22. D 9-5. D 9-14. C 9-23. C 9-6. C 9-15. D 9-24. B 9-7. B 9-16. A 9-25. B 9-8. A 9-17. A 9-9. B 9-18. D AIV-5 Chapter 10 ─ Electrostatic Discharge 10-1. B 10-16. A 10-31. D 10-2. A 10-17. C 10-32. A 10-3. C 10-18. A 10-33. D 10-4. B 10-19. C 10-34. A 10-5. A 10-20. B 10-35. B 10-6. C 10-21. C 10-36. D 10-7. B 10-22. B 10-37. C 10-8. D 10-23. B 10-38. B 10-9. A 10-24. B 10-39. B 10-10. D 10-25. D 10-40. C 10-11. B 10-26. C 10-41. D 10-12. B 10-27. A 10-42. D 10-13. A 10-28. D 10-43. B 10-14. C 10-29. B 10-44. C 10-15. D 10-30. A 10-45. C AIV-6 INDEX A A/A weapons, 7-3 AIM-120 advanced medium-range air-to-air missile (AMRAAM), 7-3 AIM-7 Sparrow, 7-3 AIM-9 Sidewinder series, 7-3 A/G weapons, 7-4 AGM-114 Hellfire, 7-5 AGM-65 Maverick, 7-5 AGM-88 high-speed anti-radiation missile, 7-4 guided bomb units, 7-4 torpedoes, 7-5 Absorption and scattering, 4-3 Accelerometers, 2-15 Acoustic processing , 4-14 to 4-15 Active and passive sonar, 4-1 Active sonobuoys, 4-12 Advanced targeting forward looking infrared (ATFLIR) operational capabilities, 6-11 advanced navigation, 6-13 built-in test, 6-13 electro-optical video, 6-12 eyesafe, 6-13 field of view and zoom, 6-12 infrared marker, 6-13 infrared video, 6-11 initiated built-in-test, 6-14 laser and FLIR align, 6-12 laser energy, 6-12 laser range, 6-12 laser spot tracker, 6-13 operational built-in test, 6-14 periodic built-in test, 6-14 pod environmental control unit, 6-13 point control, 6-12 track control, 6-12 Airborne navigation systems, 2-11 to 2-17 Airborne radar, 3-10 Airborne sonar system, 4-15 to 4-18 azimuth-range indicator, 4-16 cable and reel assembly, 4-17 dome control, 4-16 modes of operation, 4-17 multiplexer, 4-16 reeling machine, 4-17 sonar data computer, 4-16 sonar receiver, 4-16 sonar transducer, 4-17 Aircraft automatic carrier landing system components, 9-4 Index-1 angle-of-attack indicator, 9-7 automatic flight control system, 9-6 instrument landing system, 9-4 radar beacon, 9-7 receiving-decoding group, 9-7 standby attitude reference indicator, 9-5 Aircraft carrier automatic carrier landing system components, 9-4 SPN-41 instrument carrier landing system, 9-4 SPN-46 (V) 3 precision approach landing system, 9-4 Aircraft communications systems, 1-12 to 1-17 Aircraft global positioning systems, 2-13 Aircraft identification friend or foe systems, 3-18 Aircraft radar systems, 3-10 to 3-17 Aircraft tactical displays, 5-13 Airfoil, 9-1 to 9-2 airfoil terminology, 9-1 Air-to-air (A/A) master mode, 5-10 Air-to-ground (A/G) master mode, 5-9 Altimeters, 2-8 absolute (radar) altimeters, 2-10 pressure altimeter, 2-9 Altitude and atmosphere, 2-6 planes of altitude, 2-8 standard datum plane, 2-6 Amplitude modulated receiver, 1-10 Amplitude modulated transmitter, 1-6 Anomaly strength, 4-21 Antisubmarine warfare, 4-1 APG-73 radar system, 3-10 components, 3-10 controls and indicators, 3-11 modes of operation, 3-12 APN-234 color weather radar system, 3-16 components, 3-16 controls and indicators, 3-16 modes of operation, 3-16 Application of capacitive filters, 10-13 bandpass filters, 10-16 band-rejection filters, 10-17 capacitive filtering in an alternating current circuit, 10-13 high-pass filters, 10-16 inductive-capacitive filters, 10-15 low-pass filters, 10-15 resistive-capacitive filters, 10-14 Approach radar, 3-9 APX-123(V) IFF transponder system, 3-18 components, 3-18 modes of operation, 3-18 ARC-210 communication system, 1-12 antenna selector, 1-13 ANT-SEL COMM 1 switch, 1-13 Index-2 communications antennas, 1-13 VHF/UHF receiver/transmitter no. 1 and no. 2, 1-12 ARR-78(V) advanced sonobuoy communication link receiver set, 4-13 indicator-control unit, 4-14 on top position indicator control unit, 4-14 radiofrequency preamplifier, 4-13 radiofrequency status panel, 4-14 receiver assembly, 4-13 ASQ-22 airborne low frequency sonar, 4-18 ATFLIR system components, 6-7 advanced navigation sensor, 6-9 electro-optical sensor unit, 6-8 environmental control valve, 6-8 eurocard modules, 6-8 laser electronics unit, 6-9 laser transceiver unit, 6-9 pod adapter unit, 6-9 pod electronics housing, 6-10 power interrupt protector, 6-10 roll drive amplifier, 6-10 roll drive motor, 6-10 roll drive unit, 6-11 Atmospheric static, 10-2 Automatic carrier landing system, 9-1 components, 9-4 to 9-8 operation, 9-8 to 9-11 Automatic direction finder, 2-11 B Basic computers, 8-1 to 8-6 analog, 8-5 digital, 8-5 Basic transmitter and receiver terms, 1-4 antenna, 1-4 attenuation, 1-5 fading, 1-5 harmonics, microphone, 1-5 oscillator, 1-5 speaker, 1-5 subharmonics, 1-6 suppression, 1-5 tuned circuits, 1-5 varactors, 1-5 Beam scanning, 3-8 Bonding, 10-17 to 10-19 bonding for lightning protection, 10-18 purpose of bonding, 10-18 Broadband interference, 10-3 Index-3 C Capacitive filter, application, 10-13 Capacitor selection, 10-13 Capacitors, 10-10 coaxial feedthrough capacitors, 10-11 function, 10-10 limitation, 10-11 Common weapons, 7-1 Communications, 1-1 Complex coupling, 10-10 Computer applications, 8-4 business, 8-4 database, 8-4 process control, 8-4 simulation, 8-4 Computer functions, 8-3 display data, 8-4 disseminate data, 8-4 gather data, 8-3 process data, 8-4 store data, 8-4 Computer terms, 8-1 Computers, 8-1 Conductive coupling, 10-8 Continuous wave, 3-7 Control segment, 2-14 Cosmic noise, 10-3 Coupling by radiation, 10-10 D Data link, 1-16 A507 data terminal set communications interface 2, 1-17 C-7790A data terminal set control-monitor, 1-17 CV-2528 data terminal set convertor-control, 1-17 PP-6140 data terminal set power supply, 1-17 Data transmission, 8-7 to 8-10 Detectors, 6-4 elemental detectors, 6-4 imaging detectors, 6-4 Digital communications system, 1-14 Digital data indicators, 5-14 Digital data transmission, 8-8 fiber optic, 8-9 parallel mode, 8-9 serial mode, 8-8 Direction, 2-2, 2-5 Direction-finder group, 5-2 Distance, 2-2, 2-5 Divergence, 4-5 Doppler effect, 3-7, 4-7 Index-4 Doppler effect and sonar, 4-7 Drag, 9-2 E Earth's size and shape, 2-2 to 2-11 Electrical communications, 1-1 facsimile, 1-2 radiotelegraph, 1-1 radiotelephone, 1-2 teletypewriter, 1-2 Electrical noise, 10-4 to 10-8 nonlinear elements, 10-8 power-lines, 10-8 sources of, 10-4 to 10-8 Electromagnetic spectrum, 6-1 Electronic flight director system components, 5-3 electronic flight director systems control, 5-3 multifunction displays, 5-3 Electronic flight display system, 5-1 to 5-7 Electronic flight display system interfaces, 5-1 to 5-3 Electronic horizontal situation indicator, 5-1 digital data computer, 5-2 direction finder group, 5-2 global positioning system, 5-2 inertial navigation system, 5-2 low frequency automatic direction finder group, 5-2 multi-mode receiver, 5-2 navigation simulator, 5-2 tactical air navigation set, 5-2 Electrostatic discharge, 10-1, 10-19 to 10-21 Electrostatic discharge elimination, 10-21 Electrostatic discharge protective materials, 10-22 antistatic electrostatic discharge protective materials, 10-22 conductive electrostatic discharge protective materials, 10-22 hybrid electrostatic discharge protective materials, 10-22 Electrostatic discharge sensitive device handling, 10-23 Electrostatic discharge sensitive device packaging, 10-23 Energy-matter interaction, 6-4 alternating current generators and motors, 10-4 direct current motors, 10-4 inverters, 10-5 photon effect, 6-4 propeller systems, 10-6 pulsed electrical equipment, 10-6 radar, 10-6 receiver oscillators, 10-7 relays, 10-5 rotating electrical machines, 10-4 switching devices, 10-5 thermal effect, 6-4 thyratrons, 10-6 Index-5 transponders, coded-pulse equipment, and beacons, 10-6 F F/A-18 mission computer system, 8-12 to 8-19 control-convertor, 8-14 digital data computers, 8-13 electronic equipment control, 8-15 MC/HYD ISOL control panel assembly, 8-16 right and left mux bus impedance matching networks, 8-16 systems components, 8-12 F/A-18E/F Super Hornet, 7-5 to 7-11 A/A missile control systems, 7-9 A/G weapons control systems, 7-9 armament computer, 7-6 armament safety override switch, 7-6 armament subsystems, 7-8 armament system basic controls, 7-5 armament system circuit breakers, 7-6 cockpit basic controls, 7-7 digital display indicators, 7-7, 7-8 gun systems controls, 7-11 head-up display, 7-8 integrated defensive electronic countermeasures dispensing systems, 7-11 jettison systems, 7-10 landing gear control panel, 7-6 left- and right-hand controllers, 7-8 master arm control panel, 7-8 mission computers, 7-6, 8-12 to 8-19 rear advisory and threat warning indicator panel, 7-8 rear cockpit basic controls, 7-8 signal data converter control, 7-7 up-front control display, 7-8 Facsimile, 1-2 Factors affecting the sound wave, 4-3 Forces affecting flight, 9-2 drag, 9-2 lift, 9-2 thrust, 9-2 weight, 9-2 Forward looking infrared system, 6-7 to 6-14 Frequency modulated receiver, 1-11 Frequency modulated transmitter, 1-7 Frequency modulation, 3-7 Front-end optics, 6-6 G General computer terms, 8-1 hardware, 8-1 software, 8-2 Global positioning system, 2-13, 5-2 aircraft GPS, 2-14 Index-6 control segment, 2-14 space segment, 2-13 user segment, 2-14 Great circles, 2-2 H Head-up display, 5-7 to 5-13 altitude switch, 5-8 attitude switch, 5-8 controls and indicators, 5-7 course set switch, 5-8 day/auto/night switch, 5-8 heading set switch, 5-8 modes of operation, 5-8 symbology brightness control, 5-8 symbology normal/reject 1/reject 2 switch, 5-8 I Identification friend or foe, 3-17 to 3-19 modes of operation, 3-17 system components, 3-17 systems principles, 3-17 to 3-19 Image processing system, 6-6 Indicators, 5-1 Inductive-capacitive coupling, 10-10 Inductive-magnetic coupling, 10-9 Inertial navigation system, 2-14, 5-3 accelerometers, 2-15 alignment, 2-16 basic components, 2-14 inertial corrections, 2-15 Infrared, 6-1 Infrared imaging systems, 6-5 detector array, 6-5 detectors, 6-5 front-end optics, 6-6 image processing system, 6-6 refrigeration system, 6-6 scene dissection system, 6-5 single detector, 6-5 Infrared radiation, 6-2 to 6-7 optics, 6-3 sources, 6-2 Instrument landing system, 9-1 Intercommunication system, 1-15 COMM CONT panel, 1-16 intercommunication amplifier-control, 1-16 Interference coupling, 10-8 to 10-10 Index-7 L Landing sequence, 9-8 mode I landing operation, 9-9 safety provisions, 9-10 Lateral axis, 9-3 Latitude, 2-3 direction, 2-5 distance, 2-4 latitude, 2-3 longitude, 2-3 Left digital data indicator, 5-14 Lift, 9-2 Longitude, 2-3 Longitudinal axis, 9-3 Low frequency automatic direction finder group, 5-3 M Magnetic anomaly, 4-19 Magnetic anomaly detection, 4-19 to 4-25 Magnetic detection principles, 4-19 Maneuver noises, 4-22 Man-made interference, 10-3 broadband interference, 10-3 narrow band interference, 10-4 MH-60R Seahawk, 7-15 to 7-19 AGM-114 Hellfire missile control system, 7-18 armament control indicator, 7-16 armament subsystems, 7-17 armament system basic controls, 7-16 cockpit basic controls, 7-16 control indicator, 7-17 data handling system, 7-16 defensive countermeasure system, 7-19 disabling switch for armament safety circuit, 7-16 jettison system, 7-19 mission displays, 7-17 primary mission and flight computer, 7-16 processing interface unit, 7-16 sensor operator station basic controls, 7-17 sonobuoy launch system, 7-17 stores management system, 7-16 torpedo release system, 7-17 weight-on-wheels switch, 7-16 Missile guidance radar, 3-9 Mission computer system interface, 8-16 avionics mux channel 1, 8-16 avionics mux channel 2, 8-16 avionics mux channel 3, 8-17 avionics mux channel 4, 8-17 avionics mux channel 5, 8-17 Index-8 avionics mux channel 6, 8-17 control-convertor channel, 8-17 electronic equipment control interface, 8-18 Multifunctional information distribution system, 1-14 fixed notch filter, 1-15 radio terminal unit, 1-14 remote power supply, 1-15 switchable notch filter, 1-15 Multi-mode radar system, 3-14 components, 3-14 controls and indicators, 3-15 modes of operation, 3-15 Multi-mode receiver, 5-2 Multipurpose color display, 5-15 Multipurpose display group, 5-13 N Narrow band interference, 10-4 Natural interference, 10-2 atmospheric static, 10-2 precipitation static, 10-2 cosmic noise, 10-3 Navigation, 2-1 Navigation master mode, 5-9 Navigation simulator, 5-2 Navigational terms, 2-1 to 2-2 direction, 2-2 distance, 2-2 position, 2-1 time, 2-2 Navy frequency band use, 1-2 to 1-4 medium frequency (MF) and high frequency (HF) band communications, 1-3 very high frequency (VHF) and ultrahigh frequency (UHF) band communications, 1-4 very low frequency (VLF) and low frequency (LF) band communications, 1-3 Nonlinear elements, 10-8 P P-3 Orion, 7-12 to 7-15 aft interconnection box A269, 7-13 armament circuit breaker panel, 7-13 armament control box, 7-13 armament safety circuit disable switch, 7-13 armament subsystems, 7-13 armament systems basic controls, 7-12 defensive countermeasures, 7-15 forward interconnection box A395, 7-13 harpoon system basic controls, 7-14 jettison system, 7-15 maverick missile control system basic controls, 7-14 pilot armament control panel, 7-12 torpedo system basic controls, 7-14 Index-9 weapons release switch, 7-13 Passive sonobuoys, 4-11 Peripheral avionics systems, 8-11 data link, 8-12 navigation, 8-11 radar, 8-11 weapons, 8-11 Peripheral devices, 8-6 Personal apparel and grounding, 10-21 to 10-22 personnel ground straps, 10-22 smocks, 10-22 Planes of altitude, 2-8 Position, 2-1 Power-lines, 10-8 Precipitation static, 10-2 Prime generators, 10-21 Principles of magnetic detection, 4-19 anomaly strength, 4-21 compensation, 4-23 direct current circuit noise, 4-23 magnetic anomaly, 4-19 maneuver noises, 4-22 submarine anomaly, 4-21 Propeller systems, 10-6 Pulse modulation, 3-7 Pulsed electrical equipment, 10-6 radar, 10-6 transponders, coded-pulse equipment, and beacons, 10-6 Pulse-doppler, 3-7 R Radar, 3-1 Radar accuracy, 3-4 atmospheric conditions, 3-4 pulse shape, 3-4 Radar altimeters, 2-10 Radar bearing, 3-3 relative bearing, 3-4 true bearing, 3-4 Radar principles and operation, 3-1 to 3-10 Radar range, 3-2 maximum range, 3-3 minimum range, 3-3 Radar resolution, 3-4 bearing resolution, 3-4 range resolution, 3-4 target resolution, 3-4 Radar system components, 3-5 antenna, 3-6 duplexer, 3-6 indicator, 3-6 Index-10 power supply, 3-6 receiver, 3-6 synchronizer, 3-5 transmitter, 3-6 Radio communications, 1-1 Radio interference reduction components, 10-10 to 10-16 application of capacitive filters, 10-13 bandpass filters, 10-16 band-rejection filters, 10-17 capacitive filtering in an alternating current circuit, 10-13 capacitors, 10-10 coaxial feedthrough capacitors, 10-11 high-pass filters, 10-16 inductive-capacitive filters, 10-15 low-pass filters, 10-15 resistive-capacitive filters, 10-14 selection of capacitors, 10-13 Radio receiver characteristics and components, 1-9 characteristics, 1-9 components, 1-9 Radio receiver types, 1-10 to 1-11 amplitude modulation receiver, 1-10 frequency modulation receiver, 1-11 Radio receivers, 1-9 detection, 1-9 reception, 1-9 reproduction, 1-9 selection, 1-9 Radio transmitter and receiver fundamentals, 1-4 Radio transmitter types, 1-6 to 1-8 amplitude modulation transmitter, 1-6 frequency modulation transmitter, 1-7 single sideband transmitter, 1-7 Radiofrequency transmission methods, 3-6 continuous wave, 3-7 frequency modulation, 3-7 pulse modulation, 3-7 pulse-doppler, 3-7 Radiotelegraph, 1-1 Radiotelephone, 1-2 Receiver noise, 10-2 to 10-4 Receiver oscillators, 10-7 Reflection, 4-3 Refraction, 4-6 Refrigeration system, 6-6 Reverberation, 4-4 Right digital data indicator, 5-14 Rotating electrical machines, 10-4 alternating current generators and motors, 10-4 direct current motors, 10-4 inverters, 10-5 Index-11 Rotational axes, 9-3 lateral axis, 9-3 longitudinal axis, 9-3 vertical axis, 9-3 S Salinity, 4-6 Scanning methods, 3-8 beam scanning, 3-8 stationary-lobe scanning, 3-8 Scene dissection system, 6-5 Search radar, 3-8 Selection of capacitors, 10-13 Single detector, 6-5 Single sideband transmitter, 1-7 Small circles, 2-2 Sonar principles, 4-1 to 4-8 absorption and scattering, 4-3 active and passive sonar, 4-1 divergence, 4-5 Doppler effect, 4-7 Doppler effect and sonar, 4-7 factors affecting the sound wave, 4-3 reflection, 4-3 refraction, 4-6 reverberation, 4-4 salinity, 4-6 temperature, 4-5 transducers, 4-2 Sonobuoy classifications, 4-11 active sonobuoys, 4-12 passive sonobuoys, 4-11 special-purpose sonobuoys, 4-13 Sonobuoy receivers, 4-13 to 4-14 Sonobuoys, 4-8 to 4-13 deployment, 4-10 description and components, 4-8 external markings, 4-9 frequency channels, 4-9 operating life, 4-11 principles of operation, 4-9 water entry and activation, 4-10 Sound wave, 4-3 Space segment, 2-13 Special-purpose sonobuoys, 4-13 Standard datum plane, 2-6 Static electricity, 10-20 causes of static electricity, 10-20 component susceptibility, 10-21 effects of static electricity, 10-21 latent failure mechanisms, 10-21 Index-12 Stationary-lobe scanning, 3-8 Submarine anomaly, 4-21 Switching devices, 10-5 relays, 10-5 thyratrons, 10-6 T Tactical air navigation, 2-11 bearing and distance information, 2-12 radiation pattern, 2-12 tactical air navigation principles, 2-12 tactical air navigation pulse-pairs, 2-12 Tactical air navigation set, 5-2 Teletypewriter, 1-2 Temperature, 4-2 Thermal imaging, 6-2 Thrust, 9-2 Time, 2-2 Tracking radar, 3-9 Transducers, 4-2 Transmitter and receiver fundamentals, 1-4 to 1-12 U User segment, 2-14 UYS-1 single advanced signal processor system, 4-14 control-indicator, 4-15 power supply, 4-15 spectrum analyzer, 4-15 V Vertical axis, 9-3 W Weapons guidance and control, 7-1 active, 7-1 passive, 7-2 semi-active, 7-2 Weapons systems, 7-1 Weight, 9-2 Index-13 End of Book Questions Chapter 1 Communications 1-1. What type of communication is relatively slow and requires experienced operators? A. B. C. D. 1-2. What type of communication is susceptible to wave propagation characteristics? A. B. C. D. 1-3. Teletypewriter Radiotelephone Facsimile Radiotelegraph Other than commercial broadcasting stations, what other frequencies are included in the medium and high frequency bands? A. B. C. D. 1-6. Photoreactive Photoemissive Photoelectric Photoconductive What type of communication system is used for high-speed automatic communications across oceans? A. B. C. D. 1-5. Teletypewriter Radiotelephone Facsimile Radiotelegraph What type of cell is used by a facsimile system to scan an image? A. B. C. D. 1-4. Teletypewriter Radiotelephone Facsimile Radiotelegraph Guard receive International distress Radio telegraphy Frequency broadcasting Other than very low frequency, what frequency band was originally used for radio telegraphy? A. B. C. D. High Low Very low Ultra low 1-7. Other than medium frequency, what frequency band includes international distress frequencies? A. B. C. D. 1-8. At what distance above the earth does the ionosphere begin, in miles? A. B. C. D. 1-9. Low High Very high Ultra high 17 27 37 47 The characteristics of the ionosphere vary the most during what hours? A. B. C. D. Day Evening Twilight Night 1-10. What characteristic of a facsimile scanning cell is varied according to the light and dark areas of an image? A. B. C. D. Thermal Photo Electrical Mechanical 1-11. What component must have the ability to filter unwanted transmissions? A. B. C. D. Transmitter Receiver Antenna Speaker 1-12. What term describes the variation of signal strength at the receiver? A. B. C. D. Suppression Attenuation Varactor Fading 1-13. What device converts sound energy into electrical energy? A. B. C. D. Speaker Microphone Antenna Oscillator 1-14. What component is a semiconductor diode used to vary frequency outputs? A. B. C. D. Varactor Antenna Oscillator Crystal 1-15. What frequency is also known as the fundamental frequency? A. B. C. D. Advanced Combined Basic Single 1-16. What type of transmitter varies the radiofrequency output to the proportion of the modulating signal? A. B. C. D. Frequency modulating Amplitude modulating Single sideband Radar 1-17. What component of a frequency modulating transmitter is used to vary the frequency of the modulating signal? A. B. C. D. Varactor Oscillator Antenna Microphone 1-18. What single sideband transmitter component creates the upper sideband? A. B. C. D. Amplifier Multiplier Generator Filter 1-19. What frequency modulating transmitter component increases a signal to the desired transmission output level? A. B. C. D. Amplifier Multiplier Generator Filter 1-20. What term can describe heterodyning? A. B. C. D. Separating Mixing Isolating Dividing 1-21. What process occurs when a receiver separates an audio signal from a radiofrequency signal? A. B. C. D. Reception Reproduction Selection Detection 1-22. What process occurs when a receiver converts an electrical signal into an audio signal? A. B. C. D. Reception Reproduction Selection Detection 1-23. What term describes a receiver’s ability to replicate an input signal? A. B. C. D. Sensitivity Noise Fidelity Selectivity 1-24. What component of an amplitude modulating receiver filters the intermediate frequency? A. B. C. D. Detector Amplifier Mixer Antenna 1-25. What component of a frequency modulating receiver combines the radiofrequency and local oscillator signals? A. B. C. D. Discriminator Limiter Mixer Amplifier 1-26. What ARC-210 component is a radiofrequency switching unit? A. B. C. D. Receiver-transmitter Antenna selector ANT-COMM 1 switch Data link 1-27. What multifunctional information distribution system component limits the number of transmitted tactical air navigation channels? A. B. C. D. Remote power supply Fixed notch filter Switchable notch filter Radio terminal unit 1-28. What multifunctional information distribution system component provides secure and plain voice communications? A. B. C. D. Remote power supply Fixed notch filter Switchable notch filter Radio terminal unit 1-29. What frequency in megahertz is the guard frequency? A. B. C. D. 108.00 118.00 121.50 225.00 1-30. What ARC-210 frequency mode allows the operator to select 57 preset channels? A. B. C. D. Fixed Maritime Anti-jam Havequick 1-31. What ARC-210 frequency mode provides jam resistant ultrahigh frequency band communications? A. B. C. D. Havequick Maritime Fixed Guard 1-32. What aircraft communications system is used to lower the operator’s workload during close air support missions? A. B. C. D. Analog communications Digital communications Voice communications Multifunctional information distribution 1-33. A brief containing how many lines of text is provided to the operator to decrease miscommunication during a close air support mission? A. B. C. D. 3 6 9 11 1-34. What multifunctional information distribution system function improves the navigation accuracy of the host aircraft? A. B. C. D. Secure data link Secure voice Tactical navigation Relative navigation 1-35. What function of the multifunctional information distribution system allows participants to exchange real time tactical data? A. B. C. D. Data link Secure voice Relative navigation Tactical air navigation 1-36. What system provides the intercommunication amplifier-control with secure voice audio? A. B. C. D. Identification friend or foe Landing gear Stores management Multifunctional information distribution End of Book Questions Chapter 2 Navigation 2-1. What is the navigational term for a location defined by stated or implied coordinates? A. B. C. D. 2-2. At the equator, the diameter of the Earth is how many nautical miles? A. B. C. D. 2-3. Two Four Six Eight Latitude is measured up to what maximum number of degrees? A. B. C. D. 2-6. Axis Quadrant Apogee Meridian Meridians are divided into how many sections? A. B. C. D. 2-5. 6,750.25 6,864.57 6,887.91 6,950.78 What geographic term describes a great circle drawn through the north and south poles? A. B. C. D. 2-4. Time Position Distance Direction 30 60 90 180 Longitude is measured up to what maximum number of degrees? A. B. C. D. 30 60 90 180 2-7. What unit is a subdivision of degree of arc? A. B. C. D. 2-8. One minute of arc on the earth’s equator is equal to how many nautical miles? A. B. C. D. 2-9. Nanoseconds Minutes Microseconds Milliseconds 1 2 3 4 What factor determines the rate of change in position? A. B. C. D. Height Speed Direction Course 2-10. Compass roses are divided into how many degrees? A. B. C. D. 30 90 180 360 2-11. In the numerical system of navigation, what numerical value represents north? A. B. C. D. 000 090 180 270 2-12. What true direction is defined as the horizontal direction of one point to another? A. B. C. D. Course Heading Bearing Track 2-13. What true direction is defined as the horizontal direction in which an aircraft is pointed? A. B. C. D. Course Heading Bearing Track 2-14. What is the pressure, in inches of mercury, at 0 feet in the standard atmosphere? A. B. C. D. 26.82 27.82 28.86 29.92 2-15. What altitude reference plane is defined as pressure altitude corrected for temperature? A. B. C. D. Calibrated Density Pressure True 2-16. What altitude reference plane is defined as the actual vertical distance above mean sea level? A. B. C. D. Calibrated Density Pressure True 2-17. What measurement of altitude does the pointer position indicate on a pressure altimeter? A. B. C. D. Feet Meters Yards Acres 2-18. What are the altitude increments, in feet, indicated on the counter-pointer altimeter two-digit display? A. B. C. D. 10 100 1,000 10,000 2-19. What category of pressure altimeter error is caused by the irregular expansion of aneroid cells? A. B. C. D. Scale Installation Mechanical Hysteresis 2-20. What category of pressure altimeter error results in a lag of altitude indication? A. B. C. D. Scale Installation Mechanical Hysteresis 2-21. Radar altimeters are reliable up to what maximum feet in altitude? A. B. C. D. 1,000 3,000 5,000 7,000 2-22. Radar altimeter systems are in what condition when the aircraft is weight-on-wheels? A. B. C. D. Enabled Disabled Synched Stowed 2-23. What airborne navigation system detects bearing only? A. B. C. D. Automatic direction finder Global positioning Inertial navigation Tactical air navigation 2-24. What airborne navigation system detects bearing and range? A. B. C. D. Automatic direction finder Global positioning Inertial navigation Tactical air navigation 2-25. A tactical air navigation system uses how many two-way operating channels? A. B. C. D. 100 115 126 133 End of Book Questions Chapter 3 Radar 3-1. Radiofrequency energy travels at approximately how many feet per microsecond? A. B. C. D. 3-2. A radar mile equals how many total microseconds? A. B. C. D. 3-3. Pulse repetition time Pulse repetition width Pulse repetition sensitivity Pulse repetition frequency What type of mile does the Navy use to calculate a radar mile? A. B. C. D. 3-6. True Inertial Relative Magnetic What is the primary limiting factor when determining the maximum range of a radar system? A. B. C. D. 3-5. 10.36 11.36 12.36 13.36 What type of bearing is measured in a clockwise direction using the centerline of the radar antenna? A. B. C. D. 3-4. 684 784 884 984 Statute Nautical Imperial Standard What typical radar system component supplies the signals that time the transmitted pulses? A. B. C. D. Duplexer Receiver Transmitter Synchronizer 3-7. Most modern aircraft use what type of display to show radar data? A. B. C. D. 3-8. Which of the following terms describes radiofrequency energy processed by a radar receiver? A. B. C. D. 3-9. Adaptable Versatile Dedicated Multipurpose Echo Eche Ecru Ecco What characteristic of pulses is directly related to the pulse repetition frequency? A. B. C. D. Width Height Timing Duration 3-10. What type of radar lobe scanning is the simplest? A. B. C. D. Single Active Parasitic Stationary 3-11. Other than electronic, what other beam scanning method can be found in modern radar systems? A. B. C. D. Automatic Stationary Mechanical Motorized 3-12. How many dimensions are indicated by target range and bearing? A. B. C. D. Two Three Four Five 3-13. What type of missile guidance radar uses energy radiated from the target? A. B. C. D. Beam Passive Homing Unguided 3-14. What APG-73 radar component uses a two-axis gimbal assembly? A. B. C. D. Receiver Transmitter Antenna Processor 3-15. What APG-73 radar component commands the position of the antenna? A. B. C. D. Servo Planar Gimbal Waveguide 3-16. What type of gain does the APG-73 radar planar array use when directing a radiofrequency pencil beam? A. B. C. D. Low Medium High Truncated 3-17. The APG-73 radar receiver converts a radiofrequency signal into what type of signal? A. B. C. D. Low Intermediate Modulated Transitional 3-18. The APG-73 power supply converts aircraft power into what type of power for use by the system? A. B. C. D. Direct Indirect Ancillary Immediate 3-19. How many radar switch positions are available on the sensor control panel? A. B. C. D. Three Four Five Six 3-20. The APG-73 radar system has how many main modes of operation? A. B. C. D. Three Four Five Six 3-21. What APG-73 air-to-ground sub mode of operation offers three different resolution options? A. B. C. D. Real beam Sea surface Doppler beam Precision velocity 3-22. What is the APG-73 radar default main mode of operation? A. B. C. D. Air Map Ground Navigation 3-23. What component of the multi-mode radar system radiates X-band radiation? A. B. C. D. Antenna Receiver Transmitter Interrogator 3-24. What component of the multi-mode radar system houses the Identification Friend or Foe interrogator? A. B. C. D. Dias Platform Pedestal Support 3-25. What component of the multi-mode radar system interfaces with the mission computer system? A. B. C. D. Data director Data handler Data controller Data processer 3-26. What multi-mode radar assembly directs the X-band energy to be radiated from the antenna? A. B. C. D. Receiver Processor Waveguide Transmitter 3-27. The multi-mode radar system has how many general modes of operation? A. B. C. D. Three Four Five Six 3-28. The multi-mode radar Identification Friend or Foe antenna uses what frequency band? A. B. C. D. L K X C 3-29. What multi-mode radar mode of operation is useful for low-visibility navigation? A. B. C. D. Navigation Target designate Long-range search Short-range search 3-30. What type of radar does the multi-mode radar system use to capture an image of a surface target? A. B. C. D. Natural aperture Synthetic aperture Genuine aperture Artificial aperture 3-31. What aircraft uses the multi-mode radar system? A. B. C. D. MH-60R Seahawk P-3 Orion F/A-18E Super Hornet E-2 Hawkeye 3-32. What component of the APN-234 radar system is 10 inches and flat in shape? A. B. C. D. Receiver-transmitter Waveguide assembly Data processor Antenna assembly 3-33. In what frequency range, in hertz, does the APN-234 radar system transmit a constant level pulse? A. B. C. D. 200 to 400 200 to 600 200 to 800 200 to 900 3-34. Other than target range, what information is displayed on the APN-234 indicator-controller? A. B. C. D. Velocity Bearing Altitude Attitude 3-35. What component of the APN-234 radar system processes received reflected microwave pulses? A. B. C. D. Antenna assembly Waveguide assembly Planar array Receiver-transmitter 3-36. What information does the APN-234 radar system provide to the operator? A. B. C. D. Altimetry Weather Guidance Surveillance 3-37. What level of detected moisture will return high levels of microwave energy? A. B. C. D. Low Intermediate Transitional High 3-38. When the APN-234 detects open ground, what color is displayed on the indicator? A. B. C. D. Red Yellow Blue Green 3-39. What APN-234 mode of operation displays flashing red areas on the indicator? A. B. C. D. Map Search Weather Weather alert 3-40. What APN-234 mode of operation is used to track surface objects over water? A. B. C. D. Map Search Weather Weather alert 3-41. When the APN-234 is in map mode, what condition of water will NOT return a signal? A. B. C. D. Calm Rough Shallow Swirling 3-42. What component of an Identification Friend or Foe system times radiofrequency pulse to avoid interference with radar? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-43. What component of an Identification Friend or Foe system receives the challenge signals and transmits a response? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-44. What component of an Identification Friend or Foe system initiates the trigger pulse when an unidentified aircraft has been detected? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-45. What component of an Identification Friend or Foe system responds to coded-pulse signals? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-46. What component of an Identification Friend or Foe system initiates a radar video signal? A. B. C. D. Interrogator Transponder Search radar unit Coder-synchronizer 3-47. A typical Identification Friend or Foe system has how many modes of operation? A. B. C. D. Four Five Six Seven 3-48. What Identification Friend or Foe mode is used by both military and civilian air traffic controllers? A. B. C. D. 1 2 3/A C 3-49. What Identification Friend or Foe mode provides for the general identification of only military aircraft? A. B. C. D. 1 2 3/A C 3-50. What Identification Friend or Foe mode has a total of 2,048 different code options? A. B. C. D. 1 2 3/A C 3-51. What Identification Friend or Foe mode is used to identify a specific military aircraft? A. B. C. D. 1 2 3/A C 3-52. Other than mode 3/A, what Identification Friend or Foe mode has a total of 4,096 different code options? A. B. C. D. 1 2 3/A C 3-53. Identification Friend or Foe mode 1 typically has what total number of code options? A. B. C. D. 32 42 52 62 3-54. What type of altimeter does mode C use to report altitude? A. B. C. D. Radar Density Pressure Compression 3-55. What APX-123(V) Identification Friend or Foe component is used to select system functions? A. B. C. D. Antenna Interrogator Transponder Control display units 3-56. What are APX-123(V) secure modes of operation? A. B. C. D. 1 and 3 2 and 4 3 and C 4 and 5 3-57. How many levels are available in mode 5? A. B. C. D. Two Three Four Five 3-58. The APX-123(V) has how many operational testing modes? A. B. C. D. Two Three Four Five 3-59. What APX-123(V) operational test automatically starts when the system is turned to the on position? A. B. C. D. Initiated Periodic Special Power up 3-60. What APX-123(V) operational test provides the operator with up-to-date status indications? A. B. C. D. Initiated Periodic Special Power up End of Book Questions Chapter 4 Antisubmarine Warfare 4-1. What type of sonar equipment depends on a transmitted sound wave and a return echo? A. B. C. D. 4-2. What characteristic can be determined by identifying the point of a reflected sound echo? A. B. C. D. 4-3. Low Medium High Very high What transmission loss characteristic causes the reduction of echo strength at long ranges? A. B. C. D. 4-6. Receiver Transducer Microphone Loud speaker What type of pressure is created by the inward movement of a transducer diaphragm? A. B. C. D. 4-5. Range Speed Bearing Wavelength What typical sonar component is used to transmit and receive sound echoes? A. B. C. D. 4-4. Active Passive Homing Semi-active Absorption Scattering Divergence Reverberation Water is how many more times denser than air? A. B. C. D. 200 400 600 800 4-7. What transmission loss characteristic is caused when a sound wave hits an object? A. B. C. D. 4-8. What transmission loss characteristic is described as the multiple reflections of a sound wave? A. B. C. D. 4-9. Reflection Scattering Absorption Divergence Scattering Absorption Divergence Reverberation At depths greater than 450 feet, water can vary what total number of degrees, in Fahrenheit? A. B. C. D. 10 20 30 40 4-10. What transmission loss characteristic can be described as the bending of sound waves caused by the variations in temperature? A. B. C. D. Salinity Refraction Divergence Reverberation 4-11. A typical sonobuoy is what diameter, in inches? A. B. C. D. 3 5 7 9 4-12. What NAVAIR technical manual provides detailed information on storing, handling, and setting sonobuoys? A. B. C. D. 26-SSL-500-1 27-SSQ-500-1 28-SSQ-500-1 28-SSR-500-1 4-13. Other than spring, pneumatic, and free-fall, what method is used to deploy a sonobuoy from an aircraft? A. B. C. D. Casing Cartridge Container Magazine 4-14. Sonobuoys can be deployed from an aircraft traveling up to what speed, in knots? A. B. C. D. 310 330 350 370 4-15. What component of a sonobuoy is used to stabilize the hydrophone at the selected depth? A. B. C. D. Float Drogue Anchor Cabling 4-16. What type of sonobuoy can be used to detect a target in high ambient noise areas? A. B. C. D. Bathythermograph Directional command activated Directional frequency analysis and recording Vertical line array directional frequency and recording 4-17. What type of sonobuoy allows for the control of a wide range of environments? A. B. C. D. Bathythermograph Directional command activated Directional frequency analysis and recording Vertical line array directional frequency and recording 4-18. What type of sonobuoy uses a flux gate compass to provide a magnetic direction to a target? A. B. C. D. Bathythermograph Directional command activated Directional frequency analysis and recording Vertical line array directional frequency and recording 4-19. What type of sonobuoy is classified as special purpose? A. B. C. D. Bathythermograph Directional command activated Directional frequency analysis and recording Vertical line array directional frequency and recording 4-20. A bathythermograph probe descends at what constant speed, in feet per second? A. B. C. D. 1 3 5 7 4-21. What sonobuoy receiver component contains dual power supplies? A. B. C. D. Receiver assembly Indicator-control unit Radio frequency status panel On top position indicator-control unit 4-22. What sonobuoy receiver uses the ARC-143 radio control set for interface? A. B. C. D. Receiver assembly Indicator-control unit Radio frequency status panel On top position indicator-control unit 4-23. What sonobuoy receiver component is capable of producing audio outputs used in monitoring? A. B. C. D. Receiver assembly Indicator-control assembly Radio frequency status panel On top position indicator-control unit 4-24. What single advanced signal processor component extracts acoustic target information from received signals? A. B. C. D. Power supply Control-indicator Spectrum analyzer Receiver-transmitter 4-25. What single advanced signal processor component protects against the loss of data? A. B. C. D. Power supply Control-indicator Spectrum analyzer Receiver-transmitter 4-26. What typical sonar dipping set component provides the output for aural monitoring of signals? A. B. C. D. Multiplexer Sonar receiver Sonar data computer Azimuth-range indicator 4-27. What typical sonar dipping set component contains controls to initiates operational tests? A. B. C. D. Multiplexer Sonar receiver Sonar data computer Azimuth-range indicator 4-28. What typical sonar dipping set component is the most important? A. B. C. D. Dome control Reeling machine Sonar transducer Cable and reel assembly 4-29. What typical sonar dipping set component is used to route signals between the transducer and the multiplexer? A. B. C. D. Dome control Reeling machine Sonar transducer Cable and reel assembly 4-30. What type of metal braid is used to strengthen the cable of a typical sonar dipping set? A. B. C. D. Plait Loop Armor Shield 4-31. A typical sonar dipping set cable is between what lengths, in feet? A. B. C. D. 1,200 to 1,300 1,300 to 1,400 1,400 to 1,500 1,500 to 1,600 4-32. A typical sonar dipping set offers how many modes of operation? A. B. C. D. 6 7 8 9 4-33. The MH-60R Seahawk helicopter uses what sonar dipping set? A. B. C. D. ASQ-20 ASQ-21 ASQ-22 ASQ-23 4-34. What characteristics do modern submarines rely on to accomplish their missions? A. B. C. D. Stealth Speed Depth Camouflage 4-35. Other than air, what medium allows magnetic lines of force to pass through, relatively undisturbed? A. B. C. D. Ice Rock Water Earth 4-36. What magnetic angles change in an east to west direction? A. B. C. D. Deviation Variation Geometric Aberration 4-37. Other than variation, what natural magnetic characteristic is almost impossible to measure over short distances? A. B. C. D. Dip Amplitude Frequency Wavelength 4-38. What submarine magnetic characteristic determines the intensity of the anomaly? A. B. C. D. Profile Contour Instant Moment 4-39. How does the strength of the complex magnetic field vary mathematically with respect to the distance from the anomaly? A. B. C. D. Inverse cube Constant Multiple Percentage 4-40. What Greek letter is used to measure magnetic intensity? A. B. C. D. Alpha Beta Gamma Delta 4-41. Other than maneuver noise, what is the other category of magnetic noise sources? A. B. C. D. Direct current Eddy current Alternating current Magnetic current 4-42. What rate of aircraft maneuvering reduces the effect of the eddy current field? A. B. C. D. Fast Slow Rapid Gentle 4-43. At what distance, in feet, from the aircraft fuselage should magnetometers be installed? A. B. C. D. 2 4 6 8 4-44. What variable component is used to connect compensation loops in a load center? A. B. C. D. Resistor Inductor Varactor Capacitor 4-45. What types of wires are used in newer aircraft to minimize the compensation loop size? A. B. C. D. Single Ground Twisted Shielded End of Book Questions Chapter 5 Indicators 5-1. What electronic flight display system interface receives signals from the inertial navigation system and calculates command course information? A. B. C. D. 5-2. What electronic flight display system interface incorporates signals from other systems such as the instrument landing and the marker beacon? A. B. C. D. 5-3. True Relative Indicated Electronic The fixed cardinal marks on the electronic horizontal situation indicator are displayed around the compass card at intervals of how many degrees? A. B. C. D. 5-5. Navigation simulator Digital data computer Multi-mode receiver Tactical air navigation set The aircraft inertial navigation system provides the electronic flight display system with magnetic and what other type of heading? A. B. C. D. 5-4. Navigation simulator Digital data computer Multi-mode receiver Tactical air navigation set 25 35 45 55 The electronic horizontal situation indicator bearing pointer 1 is selected by which of the following operators? A. B. C. D. Pilot Copilot Navigator Maintainer 5-6. The electronic flight director crosshair indicator provides a centering cue during what type of approach? A. B. C. D. 5-7. What symbol is used as a reference source for the electronic flight director pitch and roll indicators? A. B. C. D. 5-8. Aircraft Horizon Heading Navigation The electronic flight director pitch tape provides the position of the pitch tape in reference to what area of the aircraft? A. B. C. D. 5-9. Level Manual Localizer High speed Tail Nose Left wing Right wing The electronic flight director heading tape shows the current heading with how many degrees displayed on each side of the center of the indicator? A. B. C. D. 5 10 15 20 5-10. When the head-up display attitude switch is placed in AUTO, what type of inertial navigation data will be used as the primary source? A. B. C. D. Raw Calculated Unfiltered Filtered 5-11. How many master modes can be displayed on the head-up display? A. B. C. D. Three Four Five Six 5-12. The head-up display air speed box displays what type of air speed? A. B. C. D. Indicated Relative Calibrated Unfiltered 5-13. The head-up display vertical velocity section displays the aircraft vertical velocity in what measurement per minute? A. B. C. D. Feet Miles Kilometers Yards 5-14. The head-up display target designator is a square that encompasses how many milliradians? A. B. C. D. 10 15 20 25 5-15. An “X” displayed through a selected weapon on the head-up display indicates that the master arm switch is in what position? A. B. C. D. Arm Safe Auto Manual 5-16. What cue is displayed on the head-up display when NONE of the fuzing options have been selected for an air-to-ground weapon? A. B. C. D. Dud Breakaway Time to impact Delta time of fall 5-17. What cue is displayed on the head-up display when the selected weapon is a mine, conventional bomb, or rocket? A. B. C. D. Breakaway Time to impact Pull up Delta time of fall 5-18. What type of data signals are received by the multipurpose display group from the mission computer and radar systems? A. B. C. D. Digital Analog Raster Composite 5-19. The digital data indicators receive command signals from the mission computer system via what type of avionics multiplex bus? A. B. C. D. Single Dual Composite Redundant 5-20. The multipurpose color display is the main interface for what system? A. B. C. D. Radar Navigation Digital map Communication End of Book Questions Chapter 6 Infrared 6-1. What type of infrared radiation sensing uses both active and passive systems? A. B. C. D. 6-2. Infrared radiation is a form of what type of energy? A. B. C. D. 6-3. Two Three Four Five Thermal imaging is referenced in which of the following terms? A. B. C. D. 6-6. Frequency Duration Wavelength Amplitude Infrared radiation is divided into how many categories? A. B. C. D. 6-5. Kinetic Electromagnetic Electrical Potential What term is used when discussing the infrared region of radiation? A. B. C. D. 6-4. Intermediate Close Remote Far Reflectivity Color Aural Temperature Forward Looking Infrared devices use what speed of image framing? A. B. C. D. Slow Medium Fast Extreme 6-7. What term is used to describe the space between infrared radiation wavelengths? A. B. C. D. 6-8. On an emissivity scale of 0 to 1, what number is representative of the perfect emitter? A. B. C. D. 6-9. Window Drawer Cabinet Door 0.25 0.50 0.75 1 Infrared optics should be compatible with what type of coating? A. B. C. D. Antireflection Anticorrosive Anti-jam Antielectron 6-10. The total energy emitted by an object at all wavelengths is dependent on what characteristic? A. B. C. D. Translucency Capacitance Temperature Inductance 6-11. Infrared detectors can either be elemental or what type of optical configuration? A. B. C. D. Devising Carving Etching Imaging 6-12. What detector averages the portion of the image to the outside scene into a single signal? A. B. C. D. Elemental Imaging Geothermal Magnetic 6-13. Elemental and imaging detectors both use what type of effect? A. B. C. D. Photon Thermal Magnetic Cryogenic 6-14. What type of current flows without a radiant input? A. B. C. D. Light Translucent Dark Opaque 6-15. The external photo effect is also known as what type of effect? A. B. C. D. Photovoltaic Photoconductive Photo-reactive Photo-emissive 6-16. What type of system is used to scan an entire image? A. B. C. D. Detector Detector array Scene dissection Single detector 6-17. The Advanced Targeting Forward Looking Infrared system uses what type of thermal and visual imagery? A. B. C. D. Active Passive Inactive Semi-active 6-18. How many different WRAs make up the Advanced Targeting Forward Looking Infrared system? A. B. C. D. 10 15 20 25 6-19. What component of the electro-optical sensor unit was designed to eliminate optical errors associated with maintenance? A. B. C. D. Windscreen Laser spot tracker Infrared midwave receiver Optical bench 6-20. What component of the Advanced Targeting Forward Looking Infrared system manages the flow of aircraft cooling air? A. B. C. D. Electro-optical sensor unit Eurocard module Environmental control valve Power interrupt protector 6-21. What unit is the primary interface between the Advanced Targeting Forward Looking Infrared system, the aircraft, and the laser transceiver unit? A. B. C. D. Laser electronics unit Pod adapter unit Gimbal mounted telescope Electro-optical camera 6-22. The laser transceiver unit delivers laser energy at 20 hertz and at what wavelength, in micrometers? A. B. C. D. 0.064 1.064 5.056 12.36 6-23. What unit provides the mounting and interface between the Advanced Targeting Forward Looking Infrared system and the aircraft? A. B. C. D. Electro-optical sensor unit Pod electronics housing Pod adapter unit Roll drive motor 6-24. What component provides interface and mounting for the roll drive amplifier and motor? A. B. C. D. Environmental control valve Pod adapter unit Laser transceiver Pod electronics housing 6-25. The separated infrared imagery passes through what size of element array before being sent to the video processor? A. B. C. D. 250 X 500 350 X 350 640 X 480 800 X 500 6-26. What type of camera is used in the Advanced Targeting Forward Looking Infrared system to provide visible energy? A. B. C. D. Charged coupled device Photoelectric Closed-circuit Infrared 6-27. How many levels of optical field of view are available in the Advanced Targeting Forward Looking Infrared system? A. B. C. D. One Two Three Four 6-28. What subsystem controls air-to-air and air-to-surface autotracking functions? A. B. C. D. Laser and Forward Looking Infrared align Track control Point control Advanced Navigation Forward Looking Infrared 6-29. What subsystem of the Advanced Targeting Forward Looking Infrared system is useful for confirming target designation with ground personnel? A. B. C. D. Laser spot tracker Infrared marker Laser range Field of view 6-30. The Advanced Targeting Forward Looking Infrared system has how many built-in test options? A. B. C. D. One Two Three Four End of Book Questions Chapter 7 Weapons Systems 7-1. What homing-missile guidance, similar to active homing, is completely independent of the launching aircraft? A. B. C. D. 7-2. Other than gas generators and hydraulics, what power source can a homing missile use to control fins to alter course? A. B. C. D. 7-3. Passive only Semi-active Active only Passive and active What air-to-air missile is a radar-guided weapon that uses a high-explosive warhead? A. B. C. D. 7-6. Target detector Receiver Warhead Rocket motor What type of guidance system does the AIM-120 Advanced Medium-Range Air-to-Air Missile use until it approaches a target? A. B. C. D. 7-5. Electrical Mechanical Thermodynamic Fluid What component of a semi-active homing missile computes target information and sends electronic commands to the control section? A. B. C. D. 7-4. Active Semi-active only Passive only Semi-active and passive AIM-9M Sidewinder AIM-9X Sidewinder AIM-120 Advanced Medium-Range Air-to-Air Missile AIM-7 Sparrow What air-to-ground missile is used to detect and destroy enemy air defense systems? A. B. C. D. AGM-65 Maverick AGM-84 Harpoon AGM-88 High-Speed Anti-Radiation Missile AGM-114 Hellfire 7-7. What air-to-surface tactical missile can use infrared or laser guidance? A. B. C. D. 7-8. What air-to-ground missile can be guided to a target by laser energy either inside or outside the aircraft? A. B. C. D. 7-9. AGM-65 Maverick AGM-84 Harpoon AGM-88 High-Speed Anti-Radiation Missile AGM-114 Hellfire AGM-65 Maverick AGM-84 Harpoon AGM-88 High-Speed Anti-Radiation Missile AGM-114 Hellfire What torpedo uses existing hardware and software from other torpedo programs? A. B. C. D. MK 46 MK 48 MK 50 MK 54 7-10. How many variants of the F/A-18 series are currently being used tactically by the Navy? A. B. C. D. Four Five Six Seven 7-11. What type of path does the F/A-18E/F armament safety override switch provide for master arm power when engaged? A. B. C. D. Ground Series only Parallel only Series and parallel 7-12. How many volts direct current are directed from the F/A-18E/F main landing gear weight-offwheels relay to the master arm circuit breaker when the landing gear is in the UP position? A. B. C. D. 10 15 22 28 7-13. What F/A-18E/F computer system contains the weapons insertion panel? A. B. C. D. Armament Mission Air data Flight control 7-14. What digital data display form shows the type, number, and status of weapons loaded on the F/A-18E/F? A. B. C. D. Weapon Wing Configuration Bomb 7-15. What display is touch sensitive and provides the keypad, option select, scratchpad, and option displays? A. B. C. D. Head-up Digital data Weapon insertion Up-front control 7-16. What F/A-18E/F switch controls the flow of coolant/high-pressure pure air to the AIM-9M seeker head? A. B. C. D. AIR-TO-AIR WEAPONS SELECT CAGE/UNCAGE INFRARED COOL WEAPON VOLUME CONTROL 7-17. What F/A-18E/F air-to-ground system switch initiates the functions of the AGM-88 missile? A. B. C. D. AIR-TO-GROUND WEAPON SELECT CAGE/UNCAGE THROTTLE DESIGNATOR CONTROL DESIGNATOR CONTROL 7-18. When other jettison modes have failed, what F/A-18E/F jettison mode uses gravity to jettison stores/weapons from selected pylon stations? A. B. C. D. Emergency Selective Auxiliary Starboard 7-19. The F/A-18E/F M61 gun system has how many firing modes? A. B. C. D. One Two Three Four 7-20. What light on the P-3 armament control panel indicates the weapon/store is prepared for release? A. B. C. D. ARM HAZARD MASTER ARM KILL READY JETTISON 7-21. What P-3 interconnection box contains four subassemblies that provide control circuitry? A. B. C. D. Port Starboard Forward Aft 7-22. What P-3 component is the heart of the Maverick missile control system? A. B. C. D. Missile/Infrared detection set status panel Missile armament panel Missile interface box Missile controllers 7-23. After jettison is initiated, how many seconds does it take for the kill stores to jettison from the P-3? A. B. C. D. 10 20 30 40 7-24. What MH-60R armament system provides for the interface, processing, and display of all avionics and weapons systems? A. B. C. D. Primary mission/flight computer Processing interface units Stores management Data handling unit 7-25. What switch on the MH-60R hand control unit enables the release of torpedoes? A. B. C. D. RELEASE CONSENT TORPEDO RELEASE MASTER ARM ARMAMENT OVERRIDE 7-26. What valve does the sonobuoy stepper motor drive to the selected sonobuoy tube? A. B. C. D. Lock Distribution Manual dump Rotary 7-27. When the MH-60R gimbal switch is placed in the disable position, what happens to the forward-looking infrared turret? A. B. C. D. Turret defaults to stow. Turret slew is set to high speed. Turret slew is inhibited. Turret slew is set to low speed. 7-28. How many 32-round countermeasures dispenser magazines are located on the tail pylon of the MH-60R? A. B. C. D. One Two Three Four End of Book Questions Chapter 8 Computers 8-1. What internal characteristic of a computer determines the processing speed and power? A. B. C. D. 8-2. What hardware component is the key part of a computer? A. B. C. D. 8-3. Memory Input device Mass storage device Central processing unit Java is an example of what type of programming language? A. B. C. D. 8-6. Memory Input device Mass storage device Central processing unit What hardware component is used by an operator to manually enter data? A. B. C. D. 8-5. Memory Input device Mass storage device Central processing unit What hardware component is used to permanently store large amounts of data? A. B. C. D. 8-4. Size Power Scope Components Localized Specialized Generalized Randomized What type of software enables a developer to alter computer hardware architecture? A. B. C. D. Compiler Assembler Application Operating system 8-7. What type of software is used to translate the source code of one computer language into another computer language? A. B. C. D. 8-8. What type of software is used to run computer applications? A. B. C. D. 8-9. Compiler Assembler Application Operating system Compiler Assembler Application Operating system A computer can use what methods to gather data? A. B. C. D. Automatic only Manual and automatic Manual and semi-automatic Automatic and semi-automatic 8-10. What computer function uses memory or external storage devices? A. B. C. D. Store Display Process Disseminate 8-11. What computer function routes data to peripheral devices? A. B. C. D. Store Display Process Disseminate 8-12. What computer function allows an operator to view processed data? A. B. C. D. Store Display Process Disseminate 8-13. What computer function involves the calculation and manipulation of data? A. B. C. D. Store Display Process Disseminate 8-14. Accounting and payroll are examples of what application of a computer? A. B. C. D. Business Database Simulation Process control 8-15. What application of a computer involves an operator entering a keyword and viewing specific information? A. B. C. D. Business Database Simulation Process control 8-16. What application of a computer uses real-time data to initiate immediate corrective action? A. B. C. D. Business Database Simulation Process control 8-17. Analog computers must be able to convert analog data into what type of data? A. B. C. D. Digital Electrical Electronic Mechanical 8-18. What type of digital computer is designed to follow a specific set of instructions? A. B. C. D. All-purpose Multi-purpose Special-purpose General-purpose 8-19. A 0 and 1 in binary code represent what two signals in a computer respectively? A. B. C. D. ON and OFF OFF and ON ON and ON OFF and OFF 8-20. What is the term used to describe any device that is connected to a computer for input, output, and communication? A. B. C. D. Internal Dependent Peripheral Independent 8-21. Binary code in a computer is adjusted by voltage and what other value? A. B. C. D. Time Current Quotient Numerical operator 8-22. Peripheral devices NOT under direct control of a computer are described as being what? A. B. C. D. Inline Online Offline Outline 8-23. Other than electrical, what type of cable can be used to carry data and signals? A. B. C. D. Virtual Optical Mechanical Environmental 8-24. What type of data transmission channel requires a signal return path to control information? A. B. C. D. Simplex Multiplex Full-duplex Half-duplex 8-25. What type of data transmission is capable of transmitting and receiving information, but only in one direction at a time? A. B. C. D. Simplex Multiplex Full-duplex Half-duplex 8-26. What type of data transmission can simultaneously transmit and receive data? A. B. C. D. Simplex Multiplex Full-duplex Half-duplex 8-27. What method of digital data transmission uses photons to transmit and receive information? A. B. C. D. Serial Parallel Fiber optic Series-parallel 8-28. What method of digital data transmission uses a single wire to transmit and receive information? A. B. C. D. Serial Parallel Fiber optic Series-parallel 8-29. A typical fiber optic system incorporates transmitting and receiving capabilities into one unit called what? A. B. C. D. Oscillator Modulator Transceiver Transformer 8-30. Aircraft fiber optic cables are normally a maximum of how many feet? A. B. C. D. 200 300 400 500 8-31. What type of military specification connectors are used in aircraft fiber optic systems? A. B. C. D. MIL-DTL-38899 MIL-DTL-38989 MIL-DTL-39899 MIL-DTL-38999 8-32. Fire control components represent what category of peripheral avionics systems? A. B. C. D. Radar Data link Weapons Navigation 8-33. Aircraft instrument landing components represent what category of peripheral avionics systems? A. B. C. D. Radar Data link Weapons Navigation 8-34. Global positioning components represent what category of peripheral avionics systems? A. B. C. D. Radar Data link Weapons Navigation 8-35. A typical F/A-18 series aircraft mission computer system uses how many mux bus impedance matching networks? A. B. C. D. Two Three Four Five 8-36. What designator is used to identify the primary mux bus for all avionics mux channels? A. B. C. D. V W X Y 8-37. Each module in the processor section of the digital data computer is divided into how many sections? A. B. C. D. Four Five Six Seven 8-38. What component of a typical F/A-18 mission computer system uses a fixed software program and a central processing unit? A. B. C. D. Control-convertor Digital data computer Electronic equipment control Mission computer/hydraulic isolation assembly 8-39. A typical F/A-18 mission computer system uses how many avionics mux channels to receive and transmit data? A. B. C. D. Four Five Six Seven 8-40. What avionics mux channel is used to interface with the mission data loader system? A. B. C. D. 1 2 3 4 End of Book Questions Chapter 9 Automatic Carrier Landing System/Instrument Landing System 9-1. What characteristic of an airfoil and its relationship to the airstream is important? A. B. C. D. 9-2. What is the term used to describe the rear surface of an airfoil? A. B. C. D. 9-3. Camber Chord line Angle of attack Relative wind What is the term used to describe the straight line from the leading edge to the trailing edge of an airfoil? A. B. C. D. 9-6. Camber Chord line Angle of attack Relative wind What is the term used to describe the departure from a straight line from the leading edge to the trailing edge of an airfoil? A. B. C. D. 9-5. Camber Chord line Trailing edge Leading edge What is the term used to describe the direction of the airstream in relation to the airfoil? A. B. C. D. 9-4. Width Length Weight Shape Camber Chord line Angle of attack Relative wind What force counteracts the effects of weight? A. B. C. D. Lift Drag Mass Thrust 9-7. What force resists motion, as it acts in parallel and in the opposite direction in relation to the relative wind? A. B. C. D. 9-8. What force must be greater than or equal to the effects of drag for flight to begin or to be sustained? A. B. C. D. 9-9. Lift Drag Mass Thrust Lift Drag Mass Thrust What rotational axis is parallel to the primary direction of the aircraft? A. B. C. D. Lateral Vertical Diagonal Longitudinal 9-10. What rotational axis is perpendicular to and intersects the roll axis? A. B. C. D. Lateral Vertical Diagonal Longitudinal 9-11. Other than azimuth information, what information is transmitted by the SPN-41 instrument carrier landing system? A. B. C. D. Speed Direction Elevation Angle of attack 9-12. What instrument landing system component detects and amplifies the microwave signals from the instrument carrier landing system? A. B. C. D. Radio receiver Pulse-decoder Ku band antenna Ku band waveguide assembly 9-13. What instrument landing system component routes the elevation and azimuth error signals to the aircraft displays? A. B. C. D. Radio receiver Pulse-decoder Ku band antenna Ku band waveguide assembly 9-14. What instrument landing system component provides the path for signal routing? A. B. C. D. Radio receiver Pulse-decoder Ku band antenna Ku band waveguide assembly 9-15. The standby attitude reference indicator uses a gimbal-mounted sphere capable of rotating how many degrees? A. B. C. D. 180 270 360 450 9-16. What automatic flight control system interlock is required to couple and process data link signals to the pitch and bank channels? A. B. C. D. Safety Failsafe Electrical Acquisition 9-17. A typical automatic flight control system provides synchronization in how many axes? A. B. C. D. Three Four Five Six 9-18. What radar beacon component produces the X-band reply signals? A. B. C. D. Receiver Receiver-transmitter Ka band coaxial cable Ka band waveguide assembly 9-19. The radar beacon receiver produces what type of modulated signal envelope, called spin error? A. B. C. D. Amplitude Frequency Alternating Wavelength 9-20. How many components make up the radar beacon system? A. B. C. D. Three Four Five Six 9-21. What automatic carrier landing system mode is a fully automatic approach from entry point to touchdown? A. B. C. D. I II III IV 9-22. What automatic carrier landing system mode uses talkdown guidance from a shipboard controller? A. B. C. D. I II III IV 9-23. Apart from descent, what is the other phase of the aircraft carrier landing sequence? A. B. C. D. Marshal Approach Transition Conversion 9-24. What channel is assigned to the aircrew when the aircraft has been cleared to approach the aircraft carrier? A. B. C. D. Radar Data link Detector Communication 9-25. The instrument carrier landing system freezes compensation messages to the aircraft at approximately how many seconds before touchdown? A. B. C. D. 1.5 2.5 3.5 4.5 End of Book Questions Chapter 10 Electrostatic Discharge 10-1. Atmospheric static is the most critical at what frequency? A. B. C. D. 500 kilohertz 25 megahertz 50 megahertz 500 megahertz 10-2. What is the large electrical breakdown between two clouds or the ground? A. B. C. D. Corona discharge Precipitation static Lightning Electrical noise 10-3. What audio output results from atmospheric static? A. B. C. D. Low humming High-pitched squeal Solid tone Irregular popping 10-4. Precipitation static is a severe problem at what frequency band(s)? A. B. C. D. Low and medium Low only Ultra high Medium only 10-5. Broadband random noises consist of what characteristics? A. B. C. D. Constant in voltage and duration only Irregular in shape and duration Constant in voltage, duration, shape, and recurrence rate Regular in shape and duration 10-6. What type(s) of broadband interference are characterized by a buzzing in an audio output device? A. B. C. D. Impulse only Random noise Pulse only Pulse and impulse 10-7. What type of interference could result in the complete blocking of received signals? A. B. C. D. Narrow band Broadband Atmospheric Precipitation 10-8. What type of interference is created when a brush moves from one commutator bar to another? A. B. C. D. Static charge Sliding contact Audio- frequency hum Commutation 10-9. Which of the following has little influence on the interference-generating capability of a direct current motor? A. B. C. D. Speed Voltage Size Field windings 10-10. What type of sine wave is the ideal output of an alternating current generator? A. B. C. D. Square Pure Narrow Basic 10-11. What circuit is the likely cause of radio interference from an operating radar system? A. B. C. D. Indicator Modulator Receiver Synchronizer 10-12. What switch acts as an electromagnetically operated remote control? A. B. C. D. Relay Power Electronic Pulse 10-13. Propeller control equipment generates what maximum number of clicks and transients per second? A. B. C. D. 10 20 30 40 10-14. What signal is mixed with another radio frequency to create an intermediate frequency? A. B. C. D. Harmonic Sinusoidal Local oscillator Noise 10-15. What strength of signal can cause a nonlinear element to act like a detector or mixer? A. B. C. D. Mixed Strong Weak Interfering 10-16. Typical aircraft single- and three-phase power systems operate in what nominal frequency? A. B. C. D. 200 hertz 400 hertz 800 hertz 1,200 hertz 10-17. High order harmonics become a problem in what frequency band? A. B. C. D. Low High Very high Ultra high 10-18. Which of the following actions will reduce inductive magnetic coupling in aircraft wiring? A. B. C. D. Decreasing the spacing between wires Reducing the bend angle of the wires Increasing the spacing between wires Replacing all wires with shielded wiring 10-19. What type of shielding material has little to no effect upon a magnetic field? A. B. C. D. Magnetic Nonferrous Ferrous Composite 10-20. What characteristic of a battery lowers the effect of coupled interference? A. B. C. D. Low impedance Low operation frequency High impedance High operation frequency 10-21. At certain frequencies, almost all of the wiring in an aircraft can act like what type of equipment? A. B. C. D. Relay Oscillator Antenna Beacon 10-22. At which of the following points in the tuning band(s) of a receiver can oscillator leakage be the greatest? A. B. C. D. High and low end Low end only Middle range High end only 10-23. What coupling problem may require the use of multiple solutions to solve? A. B. C. D. Simple Inductive-magnetic Inductive-capacitive Complex 10-24. What discrete component is used to short-circuit radio interference across the source? A. B. C. D. Resistor Capacitor Inductor Transistor 10-25. At what frequency is the value of a capacitor as a bypass lost? A. B. C. D. Above resonant only Below resonant only Above and below resonant Resonant 10-26. What is the crossover frequency of a typical 4-microfarad capacitor with 3-inch leads? A. B. C. D. 0.25 megahertz 0.30 megahertz 0.34 megahertz 0.47 megahertz 10-27. How many times greater than the voltage of the circuit being filtered should the capacitor voltage be? A. B. C. D. Two Three Five Ten 10-28. What type of energy can be created when a capacitor discharges at a high rate? A. B. C. D. Kinetic Potential Chemical Transient 10-29. To ensure maximum absorption of transients, a resistive-capacitive filter should have what characteristics? A. B. C. D. Resistance should be high and capacitance low. Resistance should be low and capacitance high. Resistance and capacitance should be equal. Resistance and capacitance should be high. 10-30. The ideal low-pass filter has no insertion loss at which of the following frequency levels? A. B. C. D. At cutoff Above cutoff only Above and below cutoff Below cutoff only 10-31. A high-pass filter is very effective at keeping which of the following items from reaching an antenna and being radiated? A. B. C. D. Peak voltage Undesired harmonics Low amperage Sine waves 10-32. What type of filter is used to reject or block a band of frequencies from being passed? A. B. C. D. High-pass Bandpass Band-stop Resistive-capacitive 10-33. What type of aircraft bonding is defined as the process of obtaining conductivity between metal parts? A. B. C. D. Hydrostatic Mechanical Wavelength Electrical 10-34. Which of the following bonding methods is considered ideal for all radio frequencies? A. B. C. D. Direct Indirect Simplex Multiple 10-35. What process protects personnel and aircraft from the hazards associated with lightning discharges? A. B. C. D. Cementing Fixing Binding Bonding 10-36. What characteristic of a conductor increases directly with frequency? A. B. C. D. Inductive capacitance Inductive reactance Inductive impedance Inductive voltage 10-37. What length should a bonding jumper never exceed? A. B. C. D. 1 1/2 inches 3 inches 4 inches 6 inches 10-38. What minimum voltage can result in a device being damaged or destroyed by electrostatic discharge? A. B. C. D. 20 volts 50 volts 75 volts 100 volts 10-39. Which of the following terms describes the generation of static electricity? A. B. C. D. Dielectric effect Prime charge Electrostatic charge Triboelectric effect 10-40. In which of the following conditions is generated static electricity decreased? A. B. C. D. Humid air Hot air Dry air Cold air 10-41. Which of the following substances will retain a positive charge when rubbed against aluminum? A. B. C. D. Paper Fur Saran Rubber 10-42. What maximum number of electrostatic volts can be generated when a person walks across a carpet on a low humidity day? A. B. C. D. 1,200 1,500 20,000 35,000 10-43. Which of the following testing methods should be used to verify that equipment was damaged by electrostatic discharge? A. B. C. D. Visually inspect Use equipment built-in test Verify output voltages Check for reverse current leakage 10-44. What is the minimum resistance of personnel ground straps? A. B. C. D. 25,000 ohms 150,000 ohms 250,000 ohms 500,000 ohms 10-45. What type of electrostatic discharge protective material normally consists of metal and metalcoated materials? A. B. C. D. Conductive Reactive Antistatic Inductive 10-46. What type of electrostatic discharge protective material is pink tinted? A. B. C. D. Reactive Conductive Inductive Antistatic 10-47. What type of clothing material should be worn when electrostatic discharge protective smocks are unavailable? A. B. C. D. Polyester Cotton Linen Wool 10-48. What electrostatic discharge protective material protects equipment from both static and conduction? A. B. C. D. Antistatic Conductive Hybrid Inductive 10-49. What type of periodic check should be conducted on personnel ground straps? A. B. C. D. Voltage Continuity Temperature Capacitance 10-50. Which of the following publications provides guidance on packaging electrostatic discharge sensitive materials? A. B. C. D. NAVSEA OP 3565 OPNAVINST 3750.6R MIL-HDBK-773 NAVSUP 723