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EASA PART-66 MODULE 8.1 : PHYSICS OF ATMOSPHERE

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EASA PART-66 MODULE 8.1 : PHYSICS OF ATMOSPHERE

1. 1. 8.1 PHYSICS OF THE ATMOSPHERE www.part66.blogspot.com
2. 2. AERODYNAMICSThe study of objects in motion through air and the forces that produce such motion. THE ATMOSPHERE
3. 3. ATMOSPHERIC CONTENT• Composition of air :-  78% - Nitrogen  21% - Oxygen  1% - Other Gases (argon, carbon dioxide, hydrogen, helium, neon, etc.)OXYGEN Human breathing Fuel combustion  keep aircraft flying THE ATMOSPHERE
4. 4. PRESSURE ‘Air has weight’ Pressure  weight (force) Column of air pressing down on a given extending from area sea level upward Weight decreases with increasing height Sea level atmospheric pressure under standard condition ( 15° C / 59° F )  14.69 psi or  29.92 in Hg. or  1013.25 millibars or  101.325 kPa PRESSURE
5. 5. Atmospheric pressure decreases with altitude PRESSURE
6. 6. TEMPERATURE o Decrease with increasing altitude o Constant (-55˚C) above 55 000 ft (12 km) o Decrease at a lapse rate of 1.98˚C per 1000 ft o Standard day temperature at seaSun radiate level  15˚C / 59˚Fheat o Temperature does not affect muchthrough on aircraft in flight but it does affectatmosphere the variations of humidity o Humidity affect flight operationEarth absorbheat (increase Warm air rises, expands, coolsair temperatureon surface) TEMPERATURE
7. 7. Change of temperature with height TEMPERATURE
8. 8. Effect of temperature on take-off run and Rate of Climb COLD WINTER DAY HOT SUMMER DAY• Aircraft requires longer runway for takeoff on damp day than on dry day HUMIDITY
9. 9. DENSITY ‘Air is compressible’ Compressed air  more dense (less space occupied by air) Density = measure of air thickness Density varies directly with pressure Low altitude  more dense High altitude  less dense Density at sea level is 1.225 kg/m3 DENSITY
10. 10. Density affect the aerodynamic performance of aircraft ALTITUDE HIGH Altitude LESS Density Greater speed and distance LOW Altitude GREATER Density Same Horsepower Less speed and less distance DENSITY
11. 11. HUMIDITY Amount of water vapor in air (condition of moisture or dampness) Temperature influence the maximum amount of water vapor that the air can hold Higher air temperature  absorb more water vapour Density of air varies with humidity Density on damp day (hot day) is less than density on dry day (cold day) HUMIDITY
12. 12. THE ATMOSPHEREThe whole mass of air extending upward for hundreds of miles from the earth (320 km in depth) THE ATMOSPHERE
13. 13. LAYERS OF ATMOSPHERE THE ATMOSPHERE
14. 14. INTERNATIONAL STANDARD ATMOSPHERE (ISA)o Atmospheric conditions TEMPERATURE vary around the world • 15˚C due to changes in the • 59˚F properties of the PRESSURE atmosphere • 14.69 psi • 29.92 in Hgo Established to provide a • 1013.25 milibar common reference for • 101.325 kPa temperature, pressure • 1 atm and density at varying DENSITY altitudes • 1.225 kg/m3 ISA
15. 15. Q CODE• To similarise the altitude reference of all aircraft• Due to variable atmospheric condition around the world• 3 type of code : – QFE : aircraft height above airfield – QNH : Aircraft height above sea level (local condition) – QNE : Aircraft height above sea level (ISA condition)
16. 16. AIRSPEED• Speed of sound is 331m/s at sea level with temperature 0oc• Mach number as reference to speed of sound at that altitude• Speed of sound reduce with reduce in temperature• Indicated Airspeed(IAS) is direct reading from gauge measured by dynamic air pressure of aircraft• True airspeed(TAS) is true flying speed base on actual atmospheric condition.• IAS is less thab TAS in altitude.