Part 66 Preparation: Airframe Structures

PHYSICS OF THE ATMOSPHERE

2. AERODYNAMICS Study of objects moving through the air and the forces that produce said movement. THE ATMOSPHERE

3. ATMOSPHERIC CONTENT • Air composition: - 78% - Nitrogen 21% - Oxygen 1% - Other gases (argon, carbon dioxide, hydrogen, helium, neon, etc.) OXYGEN Human respiration Fuel combustion keeps airplanes flying THE ATMOSPHERE

4. PRESSURE "Air has weight" Weight pressure (force) Column of air pressing down on a given area extending from sea level up  Weight decreases with increasing height

Atmospheric pressure at sea level under standard conditions (15 ° C / 59 ° F) 14.69 psi or 29.92 in Hg. o 1013.25 millibars o 101.325 kPa PRESSURE

5. Atmospheric pressure decreases with altitude PRESSURE

6. TEMPERATURE o Decreases with increasing altitude from Constant (-55˚C) above 55,000 feet (12 km) o Decreases at a fall rate of 1.98 1.C per 1000 feet o Standard daytime temperature in the sea Solar irradiation level 15 / C / 59˚Heat o Temperature does not affect the aircraft much in flight, but humidity variations do affect the atmosphere o Humidity affects flight operation The earth absorbs heat (increases Hot air increases, expands, cools the air temperature on the surface)

7. Temperature change with height TEMPERATURE

8. Effect of temperature on takeoff run and rate of climb COLD WINTER DAY HOT SUMMER DAY • The aircraft requires a longer runway to take off on a humid day than on a dry day HUMIDITY

9. DENSITY "Air is compressible" Dense compressed air (less space occupied by air) Density = measure of air thickness Density varies directly with pressure Low altitude denser High altitude less dense Density at the level of the sea is 1,225 kg / m3 DENSITY

10. Density affects the aerodynamic performance of the aircraft HIGH ALTITUDE Altitude LESS Density Higher speed and distance LOW Altitude HIGHER density Same power Less speed and less distance DENSITY

11. HUMIDITY Amount of water vapor in the air (humid or humid condition) Temperature influences the maximum amount of water vapor that the air can hold Higher air temperature absorbs more water vapor Density of air varies with humidity  Density on a humid day (hot day) is less than the density on a dry day (cold day) HUMIDITY

12. THE ATMOSPHERE All air mass that extends upwards for hundreds of miles from the earth (320 km deep) THE ATMOSPHERE

13. LAYERS OF ATMOSPHERE THE ATMOSPHERE

14. INTERNATIONAL STANDARD ATMOSPHERE (ISA) o Atmospheric conditions TEMPERATURE vary throughout the world • 15˚C due to changes in the • 59˚F properties of the atmosphere PRESSURE • 14.69 psi • 29.92 in Hgo Established for provide a common reference • 1013.25 millibars for • 101.325 kPa temperature, pressure • 1 atm and density at different altitudes DENSITY • 1.225 kg / m3 ISA

15. Q CODE • To simulate the altitude reference of all aircraft • Due to variable atmospheric conditions around the world • 3 types of code: - QFE: height of the aircraft above the aerodrome - QNH: height of the aircraft above sea level (local condition) - QNE: Height of the aircraft above sea level (ISA condition)

16. AIR VELOCITY • The speed of sound is 331 m / s at sea level with a temperature of 0ºC • The Mach number as a reference to the speed of sound at that altitude • The speed of sound is reduced with the reduction of temperature • Indicated airspeed (IAS) is a direct meter reading measured by the aircraft's dynamic air pressure • Actual airspeed (TAS) is true flight speed based on actual atmospheric condition • IAS is lower than TAS at altitude.