Download Level 4 Aviation Review Package Lessons Covered: M431.01

Level 4 Aviation Review Package
Lessons Covered:
M431.01-Explain Features of Wing Design
M431.02-Describe Flight Instruments
M432.01-Describe Fuel Systems
M432.02-Describe Propeller Systems
M432.03-Describe Engine Instruments
M436.01-Describe Winds
M436.02-Describe Air Masses and Fronts
M437.01-Describe Air Navigation Terms
M437.02-Explain the Magnetic Compass
M431.01
Airfoils:
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slow aircraft have thick airfoils
fast aircraft have thin airfoils
Camber: The average curvature of a wing/airfoil
Chord line connects leading and trailing edge of the wing (This is the basis of all Theory of
Flight. You must know what the chord is)
Mean Average Chord (MAC) is the average chord of the wing
Boundary Layer is the thin layer of air flowing over the wing. Near the front it is smooth, called
the laminar layer. Near the read it is not smooth, called the turbulent layer. (this is caused by
skin friction) The point between these two layers is called the transition point.
The transition point moves forward as speed and angle of attack increase
A conventional airfoil is thickest 25% from the front
A laminar airfoil is thickest in the middle (50%)
A laminar wing/airfoil reduces drag by maintaining laminar airflow, and moving the transition
point further back from the leading edge. (Hence the name)
Planform is the shape of the wing as seen as above. There are three types
Rectangular, Elliptical (rounded ends), Delta (sweptback triangle shape)
Aspect Ratio: Calculated by dividing the wing span by the Average chord (MAC)
Angle of Incidence: the angle at which the wing is permanently inclined to the longitudinal axis
of the aircraft
Angle of Incidence affects the flight visibility, Takeoff/Landing Characteristics, drag in straight
and level flight
Wash-in/Wash-out: The angle of incidence at the wing tip is different than at the Wing root
Wash-in: Increasing the angle of incidence towards the wing-tips
Wash-out: Decreasing the angle of incidence towards the wing-tips (Don’t confuse the two)
Improving Flight Characteristics:
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Wing tip fuel tanks, wing droops, and winglets help reduce induced drag, and increase lift
Wing fences improve low speed stall and handling characteristics
Slots: Permanent slots near the leading edge of the wing that help stall characteristics at high
angles of attack.
Slats: Perform the same roll as slats, but close when the aircraft is not at high angles of attack.
Flaps: located on the trailing edge of the wing, can be lowered or raised to change the MAC. This
allows for better lift characteristics, with increased drag when lowered.
Spoilers and Dive Brakes:
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Spoilers are plates that pop-up on the upper surface of the wing. They increase Drag and reduce
lift
Dive Brakes are plates that pop-up on the bottom surface of the wing. They increase drag, but
have very little effect on lift.
M431.02
Pitot Static System
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uses pitot pressure and static pressure to produce readings
Pitot pressure is the pressure read by the Pitot tube. It consist of static pressure (air pressure)
and dynamic pressure (movement pressure)
Static pressure is the air pressure without any movement related factors (wind, thrust,
turbulence, etc)
Air Speed Indicator uses the difference between static and pitot pressure to give the speed of
the aircraft, relative to the air.
The vertical speed indicator uses the rate of change of static pressure to give the rate of ascent
or descent of the aircraft.
The Altimeter uses static pressure to tell the pilot how high the aircraft is above sea level.
ASI
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Red line indicates ‘never exceed’ speed. The maximum speed at which the aircraft is allowed to
operate.
Yellow arc indicates the caution range, its goes from the maximum structural cruise line to the
Vne (red) line.
Green arc indicates the normal operations range. It ends at the maximum structural cruise line.
White arc indicates which speeds fully extended flaps can be used at.
Density Error is caused because the ASI is calibrated to 19.92’ Hg. As altitude increases, density
decreases which can cause the ASI to be inaccurate
Position error: The position of the pitot tube on the aircraft may cause it to read incorrectly
because of turbulence, or different wind speeds caused by parts of the aircraft. Ex. the propeller
Lag error: error caused by friction between component parts that makes the instrument lag
Compression error: caused by the compression of air. Only relevant over Mach 1 speeds
icing error/water error/obstructions: if the pitot tube is blocked in any way it will read
differently because it is not receiving accurate readings.
Remind me to go over ‘ICE-T P.C.D’
Altimeter
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Errors may be caused when you fly into areas of different pressure, such as a different air mass,
a low pressure area caused by mountains, or abnormally cold/warm areas that cause the
pressure to change.
Density Altitude is Pressure altitude (what is shown on the altimeter) corrected for Temperature
VSI- will generally lag
Gyroscopic Instruments
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A spinning wheel set on a gimbal that allows it to point in any direction.
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Gyroscopic inertia is the tendency of a rotating object to remain in its plane of rotation. This
causes the gimbal to move around the spinning wheel.
Precession is the tendency of a rotating body, once a force is applied perpendicular to its plane
of rotation, to turn in the direction of the force 90o and take up a new plane of rotation parallel
to the force applied
Gyros are driven either through a vacuum system (low altitudes) or electrically (high altitude).
Vacuums can either be created using a venturi tube or through negative air pressure from the
engine.
Any air in a gyro must always be filtered to protect it. They should be handled with care
Instruments that use Gyros are: Heading indicators (must be reset using magnetic compass ever
15 min-in straight and level flight), Attitude Indicator (inaccurate during
acceleration/deceleration)
Turn and slip indicator (AKA. Turn coordinator): a needle indicates the angle and direction of
bank (attached to a Gyro). A ball indicates either a slip or skid, and is controlled by centripetal
forces, as well as gravity.
Angle of attack indicator indicates your angle of attack (dumb statement). It warns you when
approaching your critical angle of attack. A stall horn is often used in lieu of this in small
aircraft, but the indicator is what’s talked about in the lesson.
Mach indicator: indicates the ratio of your airspeed to the local speed of sound.
The Mach number is indicated by dividing your speed by the speed of sound. (ie. Mach 2 is twice
the speed of sound)
M432.01
The Fuel System
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An aircraft fuel system stores and delivers fuel during all phases of flight
Parts include: Fuel tanks, selector valve, lines, filters, fuel primer
A Pressure System uses pumps to force the fuel to the engine. This is used on aircraft with lots
of fuel, low wings, or aircraft that will perform acrobatic maneuvers
A Gravity System allows gravity to deliver the fuel from the tanks to the engines. It’s used in high
wing aircraft.
A selector valve allows pilots to choose which tank fuel is taken from, or block fuel flow entirely
Fuel Types
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Fuel must burn slowly to prevent it from exploding in the cylinders
Octane has minimum detonating qualities (burns slow)
Heptane has maximum detonating qualities (burns fast)
Aviation fuel is mostly Octane. The Octane rating of a fuel is calculated by the ratio of Octane to
Heptane
Octane rating is expressed in a percentage. (Ex. Grade 73 is 73% Octane, 27% Heptane)
Octane rating can only go to 100, above this is the “anti-knock” rating. (Not likely to be on the
test, I’ve never heard of Anti-Knock, and have no clue what it is)
Rating is expressed in two numbers, where the first Is the lean mixture rating, and the second is
the rich mixture rating. (reminder: rich means higher fuel:air ratio, Lean has a lower fuel:air
ratio-see below)
Carburetors
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They control the fuel to air mixture before entering the engine
Enriched mixture allows for more fuel to enter the engine with the airflow
Lean mixture allows little fuel to enter the engine with the airflow
A rich mixture cools the engine because there is more fluid to absorb heat
A lean mixture allows the engine to run hot. If the engine gets too hot, pre-detonation occurs.
Pre-ignition is when the heat of the engine causes the fuel to detonate before the spark plug
fires, because the engine is too hot. This is very bad for engine life and efficiency.
Throttle controls a valve that determines how much fuel:air mixture can enter the engine at any
one time. This controls the power output of the engine
Rich mixtures: used for high power settings (ie. climbing)
Lean mixtures: used for low power settings (ie. Cruising)
A mixture control valve controls how much fuel enters the relative airflow as it enters the
engine.
Carburetor icing occurs between -5 and 30 degrees C and can cause numerous parts of the
carburetor to become blocked with ice
Fuel Injection System
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Essentially does the same as a carburetor except there is no carburetor.
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instead separate lines run the fuel straight to the cylinders, and injects the fuel there
This allows for: more uniform distribution of fuel, and prevents the danger of carburetor icing.
M432.02
Describe Propeller Systems
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A propeller works the same as a wing, but is turned on its side. It generates “lift” in a forward
direction, as it rotates through the air. This creates thrust throughout the entire propeller
Pitch is the angle of the propeller, similar to the angle of a wing. The greater the pitch the
greater the forward thrust produced. Pitch is measured in how far the propeller moves forward
within one full rotation.
variation in the angle of attack an pitch along the length of the propeller insures uniform thrust
is maintained through the entire blade
Theoretical pitch would be the greatest distance a propeller could move forward if all conditions
were perfect. Practical pitch is how far it actually moves forward. (in feet)
Fine pitch: low angle of attack, less thrust, less drag, better for landing and take-off
Coarse pitch: high angle of attack, more thrust, more drag, better for cruising
Fluttering: when the propeller is completely coarse, the props go straight back.
Prop. Types
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Fixed Pitch: It has one type of pitch that cannot be adjusted
Variable Pitch: Can be changed
Adjustable pitch prop: can be changed on the ground, not during flight
controllable pitch prop: can be changed in flight
Constant speed prop: automatically adjust pitch to maintain a constant speed set by the pilot
Props can be adjusted inflight mechanically, hydraulically, or electronically
Hydraulic depends on oil pressure. If oil pressure is lost in flight the prop will automatically
revert to a fine pitch propeller
M432.03
Describe engine instruments
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The two most important engine instruments are oil pressure an oil temperature gauges
oil pressure gauge reads the oil pressure of the oil lubricating the engine
Oil Temp gauge reads the temperature of the oil (dumb statement again)
You should always check oil pressure immediately after starting the engine
Cylinder head temperature gauge
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It shows the temperature of the cylinder heads (….)
If temperature is too high may cause pre-ignition or detonation
Pre-Ignition: premature ignition of the fuel mixture due to glowing carbon particles
Detonation: A rapid burn of the fuel mixture due to extreme heat
Tachometer:
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It shows the rpm’s of the engines crankshaft. It has three ‘ranges’ marked on it
Green range indicates normal operation
Yellow range indicates the caution range
Red range should never be exceeded
Manifold pressure gauge
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It indicates the pressure in the manifold in PSI (between the carburetors and the pistons)
Uses red, yellow, and green ranges as well
A drop in manifold pressure could indicate carburetor icing
When the engine is not running, it will indicate atmospheric pressure
Please Note: Aircraft power decreases with altitude (lower density) due to less air being taken in.
M436.01
Surface Winds
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Wind blows from high pressure areas to low pressure areas
Surface friction slows down winds within the first thousand feet from the earth, which in turn
causes lower wind speeds than would be expected by the pressure gradient
Ana (Anabatic winds) went up the hill during the day and kicked the Kat (Katabatic winds) down at night
Mountain Waves go up the side of the mountain, then pour down the other side, creating large ripples
that can extend for many miles.
Gust: A rapid and Irreguar fluctuation in wind direction and speed for a shor period of time. (a few
seconds)
Squall: Same as a Gust, but for a longer period of time. (a minute max)
Jet streams: A narrow band of fast moving air that flows from West to East. They exist only in high areas
of the atmosphere
CAT (clear air turbulence) is turbulence encountered in a cloudless sky. It is usually felt above jet
streams.
M436.02
Air masses
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An air mass is a large section of the troposphere with uniform properties of temperature and
moisture in the horizontal
weather is determined be moisture content, the cooling process, and the stability of the air
Moist air has clouds, dry air does not
Cooled air has clouds, slow cooling air will not
Stability determines cloud type (stratus or cumulus)
Cold Air Mass
Unstable Air
Turbulence
High Visibility
Cumulous Clouds
Showers and Storms
Warm Air Mass
Stable Air
Smooth Air
Low Visibility
Stratoform Clouds
Drizzle
Fronts
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A front is the transition between two air masses
Cold Front: Cold air mass advances and undercuts the warm air mass as it advances
Warm Front: A retreating cold air mass is followed by warm air, which pushes up the side of it
All fronts are determined by the movement of the cold air mass (retreating or advancing)
A continental mass forms over land and has dry air
A maritime air mass forms over water and has moist air
Warm air masses are less dense and therefore rise. Cold air masses are more dense, and sink
M437.01
Meridians of Longitude
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Run 180o East and West, from the Prime Meridian (0 degrees) to the International Date line (180
degrees)
Semi-great circles joining the two poles
Measured in degrees, minutes, and seconds
Parallels of Latitude
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Run 90o North and South from the equator
Are parallel to the equator
Measured in degrees, minutes, and seconds
Every degree is divided into 60 minutes. Every minute is divided into 60 seconds. (distance, not time)
24hrs=360 degrees
1hr = 15 degrees
1 minute (time) = 15minutes (distance)
Great Circles: A circle on the surface of a sphere, which passes through the center, cutting it in two equal
parts.
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They represent the shortest distance between any two points
You must adjust your heading periodically in order to follow the arc of a great circle
Exception: When you are travelling North/South or straight East/West along the equator
A great circle does not cut meridians at the same angle
Rhumb line: A line that passes through all meridians at the same angle.
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It is a straight line on a map (2D), but curved on a globe(3D)
Allows for a constant heading during the flight, which is why they are used for short flights
Headings and Bearings
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Direction is always measured clockwise from the North.
North= 0 East= 90 South=180 West= 270
Heading is the direction you are travelling in.
Bearing gives the position of another object relative to you
M437.02
The earth is a giant magnet. It causes compasses to point to magnetic north.
A magnetic compass consist of a lubber line, a compass card, a compass bowl, a pivot, a magnetic
needle, and clear liquid
Variation
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The angle between magnetic north and true north. It is different dependent on where you are.
Isogonic lines join places of equal magnetic variation
Agonic lines join places with no variation
West is best, East is least. When calculating your magnetic heading (where you want to be
pointing on the compass) from your true heading, (the direction you seek to go on a map)
you add westerly deviation and subtract Easterly deviation
Deviation
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Changes in the direction of the compass caused by the metal in the aircraft
Corrected by recording the deviation in the aircraft every 30degrees and placing it on the
compass correction card, which is in the aircraft.
T.V. Makes Dumb Cadets
T (true)
corrected for
V(variation
gives
M(magnetic)
corrected for
D(deviation)
gives
C(compass)
Magnetic Dip: the compass will dip near the poles since the magnetic fields go down into the Earth.
Northerly Turning error: When turning from a northern course, the compass will lag. When turning from
a southern course, the compass will lead.
Acceleration/Deceleration errors:
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Accel: causes the compass to read a turn towards the North
Decel: causes the compass to read a turn towards the South