The Atmosphere Flashcards
Why is a discussion of the atmosphere important for aviation?
It affects flight success and preparation of flight plans.
Who developed the barometer, and what does it measure?
Pascal and Torricelli; it measures atmospheric pressure.
What happens to air density as altitude increases?
Density diminishes rapidly with altitude.
What is the composition of the atmosphere?
A mixture of gases and foreign matter like pollen, dust, and bacteria.
At what altitude is air too thin to support respiration?
Six miles up.
What is the tropopause?
The point in the atmosphere where the decrease in temperature with altitude ceases.
Name the four layers of the atmosphere.
- Troposphere
- Stratosphere
- Ionosphere
- Exosphere
What characterizes the troposphere?
Large changes in temperature and humidity; turbulent conditions.
What is the standard atmospheric pressure at sea level?
14.7 pounds per square inch (14.7 psi).
How does atmospheric pressure change with altitude?
It decreases with increased altitude.
What is the function of a mercury barometer?
It measures atmospheric pressure by balancing mercury against air pressure.
What is density altitude?
The altitude at which the air density is the same as standard density for that altitude.
Fill in the blank: Absolute humidity is the actual amount of ______ in a mixture of air and water.
water vapor.
What defines relative humidity?
The ratio of actual water vapor present to the amount needed for saturation.
What is the dew point?
The temperature at which humid air becomes saturated.
What is vapor pressure?
The portion of atmospheric pressure exerted by moisture in the air.
What is the U.S. Standard Atmosphere used for?
It provides standard reference conditions for aircraft performance calculations.
What are the standard sea level conditions for pressure in the U.S. Standard Atmosphere?
Pressure at 0 altitude (P0) = 29.92 ‘Hg.
What happens to temperature as altitude increases up to about 7 miles?
It gets steadily colder.
What occurs in the ionosphere?
Presence of ions and free electrons; electrical phenomena.
How does humidity affect aircraft performance during takeoff?
It reduces allowable takeoff gross weight and may require increased manifold pressure.
What is the temperature range in the exosphere?
Temperature is fairly constant at 2,500° Kelvin.
What is a significant characteristic of the stratosphere?
It extends from the upper limits of the troposphere to an average altitude of 60 miles.
True or False: The atmosphere’s composition remains constant from sea level to its highest levels.
False.
What is the effect of fog on engine performance?
It can decrease horsepower output and prevent detonation.
What happens to oxygen molecules in the atmosphere at 50 to 65 miles altitude?
They begin to break down under solar radiation.
What is the significance of water vapor in the atmosphere?
It affects humidity, aircraft performance, and combustion efficiency.
What is the U.S. Standard Atmosphere?
A set group of standards used as a point of reference for average atmospheric conditions in the U.S.
At what latitude is the standard atmosphere approximated?
40° latitude
What is the pressure at sea level (0 altitude) in the U.S. Standard Atmosphere?
29.92 “Hg
What is the temperature at sea level (0 altitude) in the U.S. Standard Atmosphere?
15 °C or 59 °F
What is the gravity at sea level (0 altitude) in the U.S. Standard Atmosphere?
32.174 fps/s
True or False: The U.S. Standard Atmosphere is in agreement with the ICAO Standard Atmosphere over their common altitude range.
True
What organization has adopted the ICAO Standard Atmosphere as standard?
Most of the principal nations of the world
