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AVIATION HISTORY Lecture 6: Flight Environments Earth's atmosphere The Earth's atmosphere is a thin layer of gases that surrounds the Earth. Importance of Atmosphere?? •Source of oxygen and carbon dioxide. •Maintains the temperature and climate that sustain life on earth. •Protection for the human on the Earth from the harmful cosmic ray, solar radiation and ultraviolet (UV) ray. Atmosphere Layers The Earth’s atmosphere is divided into 5 layerstroposphere is where all weather changes take place, the stratosphere is where aircraft fly and has ozone layer, then the mesosphere, ionosphere and finally the thermosphere, which is the topmost layer IONOSPHERE Troposphere The troposphere is the lowest layer of Earth's atmosphere. The troposphere starts at Earth's surface and goes up to a height of 11 km above sea level. Between 0-36’000 feet. Almost all weather occurs within this layer (below 15’000 feet). Air pressure and the density of the air are also less at high altitudes. Stratosphere The stratosphere is the second layer of Earth's atmosphere. The stratosphere occurring between about 11 km to 50km or (36’000 feet160’000 feet) Ozone is primarily found in this layer (Ozone layer). It is important to protect living earth from the harmful effects of the sun's ultraviolet (UV) radiation. Without the ozone layer life could not exist on the Earth's surface. Mesosphere The mesosphere is the third layer of Earth's atmosphere. It starts about 50 km above the ground and goes all the way up to 80 km high. Ionosphere Ionosphere is the layer of ionized gasses. It can be a conductor. Ionosphere layer can act as reflector of radio waves. Thermosphere The last atmospheric layer has an altitude greater than 80 kilometers and is called the thermosphere. The space shuttle orbits in the thermosphere of the Earth. Weather & Aviation Weather & Aviation Weather has large influences over our lives and we have absolutely no control over. Most of the weather that occurs on our planet happens below 15,000 feet. Weather is the utmost consideration of all pilots when planning a flight. Aviation is Weather Sensitive Thunderstorms Turbulence Aircraft Icing Wind Shear Thunderstorms Thunderstorms Thunderstorms is a violent storm of thunder and lightning. Thunderstorms are usually accompanied by hailstone , strong winds, and heavy rain. Hazards Of Flying In Thunderstorms 1. Lightning Lightning is the natural high-voltage electrical discharge between a cloud and the ground. Lightning affect the aircraft by build up the static electricity in the airframe. Thus, could lead to the loss of radio communications , damage the aircraft’s structure, making instrument reading impossible and affect the crew's vision Hazards Of Flying In Thunderstorms 2. Hailstone Hailstone is a small pellet of ice which falls from clouds. Can cause serious damage to an airplane. 3. Strong wind Can cause the aircraft crash during take-off or landing. 4. Heavy Rain Can reduce the visibility, produce the visual illusion, affect the braking action needed for landing. Turbulence Turbulence Turbulence is caused by rapid, irregular motion of the air. In severe turbulence, shortly throw an airplane out of control and can cause structural damage. Wake turbulence generated behind large aircraft. Jetstream wind (high winds that encircle the globe) How to avoid turbulence? Get weather reports before and during flights Weather displays will show areas of turbulence to note or to avoid. How to avoid thunderstorm? Don't fly under a thunderstorm even if you can see through to the other side. Avoid by at least 20 miles any thunderstorm identified as dangerous Don't land or take off in the face of an approaching thunderstorm. Aircraft Icing Aircraft Icing Icing is the accumulation of ice on the exposed surfaces of aircraft. Icing occur above the freezing level where the water droplets are super cooled. Pilots and controllers need to be aware of the icing process. Effect of the icing 1. Can reduce the aircraft efficiency. Aircraft’s efficiency reduce because lift decrease, thrust decrease while weight and drag increases. Effect of the icing 2. Can make aircraft loss of control Ice forming on the rudder, elevator aileron, brakes & landing gear could make aircraft loss of control 3. Can affect the aircraft engine performance. Ice forming on the engine’s inlet prevents the air intake & could affect the aircraft engine performance. 4. Cause an aircraft loss of radio communications. Ice forming on the radio antenna will cause an aircraft loss of radio communications. 5. Can lead to false indications giving by flight instruments. (Ice forming on Pitot-Static System) How to avoid icing Contact the weather office to obtain a forecast about expected icing. Avoid flight into an area where icing conditions are known to exist. (Example: wet snow when the temperature is near 0°C). Change altitude to get out of the icing as rapidly as possible. Protection from Icing Anti-icing: To prevent ice from forming. De-icing: To remove ice after it has formed Anti-icing The process of spraying a glycol solution on the parts of an aircraft to prevent the formation of ice during inclement weather conditions Anti-icing Electrical systems for keeping critical areas free of ice. De-icing De-icing is the process of removing snow & ice from an aircraft surface. Wind Shear Wind shear Wind shear is a quick change in the wind speed & direction that can cause aircraft lose in control. If an aircraft experiences a sudden decrease in wind speed, it can reduce the lift on its wings to dangerously low values. How to avoid wind shear Aircraft must be equipped with radar/ sensors that can alert pilots to windshear hazards. Many airports now have wind shear detection equipment near the ends of runways to warn aircraft if it is too dangerous to land. Why do Airplanes Fly at High Altitudes? Flying High Depending upon the length of the flight and the type of aircraft, cruising altitudes typically vary between approximately 25,000 feet and 40,000 feet (FL 250-400). This altitude allows the aircraft To: Avoid bad weather Increase engine efficiency and save fuel Avoid obstacles/mountains Have clear Visibility Avoid collision with another aircraft Flying High 1. To avoid bad weather Most of the weather that occurs on our planet happens below 15,000 feet. There are generally fewer clouds and less turbulence at high altitudes. Beside that, the air is thinner at high altitude. So, there is also less ice accumulation at high altitudes. Thus, flying high is safer region from bad weather. Flying High 2. To increase engine efficiency and save fuel The higher the aircraft altitude the thinner the air. As the air becomes thinner, it creates less resistance to objects flying through it. Therefore, less thrust is needed to move the aircraft forward at a given speed. As a result, airplanes can fly more efficiently at higher altitudes with less fuel. Flying High 3. To avoid obstacles/mountains Himalayan mountain includes over 100 mountains exceeding 7,200 m (23,622 ft). Aircraft flying high in order to avoid the collision with the high mountain. Flying High 4. To have clear Visibility The higher the altitude the smoother the air, thus the visibility is always better. Flying low makes aircraft too close to the clouds. This may make it hard for the pilot to see. Flying low means more bug and insects on the wind shield which again can make it hard for the pilot to see in front and reduce visibility. Flying High 4. To avoid collisions with another aircraft The high altitudes are also great for separation of flights to avoid collisions. At high altitudes (above 29,000 feet) planes are required to have at least 2000 ft of vertical separation (it is usually 1000 ft when below 29,000 ft).