The Atmosphere Flashcards
Name the principal gases which constitute the atmosphere
78% nitrogen
21% oxygen
1% argon
0.4% other
Name the principal gases which constitute the atmosphere
78% nitrogen
21% oxygen
1% argon
0.4% other
Define air density
Influenced by,
Atmospheric pressure
Air temperature
Moisture content, humidity
Explain how air density varies with altitude within the atmosphere
The higher you go the less weight and therefore pressure the air has
State the relationship between pressure/temperature and the density of an air mass.
The warmer the air the less dense it becomes
Describe how pressure,temperature and density normally vary within the atmosphere
The combined effects mean that,
With altitude, the pressure falls off, which reduces density
With altitude, the temperature falls off, which tends to increase density.
Because the pressure effect has by far the greater influence it can be said that with altitude, density decreases.
Explain the basis for the International Standard Atmosphere
These are baseline, average conditions for density that recognise the following,
Sea level pressure at 1013.25hPa
Sea level air temp at 15 degrees Celsius
Temperature lapse rate is 1.98 degrees per 1000ft up to 36,090 ft where it is accepted the temp is -56.6 Celsius
Explain high pressure altitude
When pressure ( QNH) is lower than usual at any given altitude we have less density and therefore performance is reduced.
It’s as if we were at a higher altitude, hence the term high pressure altitude.
Explain high density altitude
It’s to do with temperature
If we have higher than normal temps at a given altitude the air is less dense and will affect performance.
It as if we were at a higher altitude and hence the name High Density Altitude
Review 2
1. The three elements that determine air density are——,—— and ——
Height - altitude
Heat - temperature
Humidity - moisture
Review 2
2. Air pressure is the result of the ———- of a column of air above ———
Weight, datum
Review 2
3. with increasing altitude, air pressure——, which causes air density to——-
Decreases
Decrease
Review 2
4. The atmosphere is warmed from above or below?
Below
Review 2
5. With increasing altitude, air temperature ( increases, decreases) and this tends to ( increase, decreases) air density
Decreases
Increase
Review 2
6. The combined effect of pressure and temperature changes with increasing altitude causes air density to ( increase, decrease)
Decrease
