The Atmosphere Flashcards
The density (or mass) of air at sea level is about ...................kg/cubic metre. By contrast, the density of fresh water is ...................kg/cubic metre.
The density (or mass) of air at sea level is about 1.225kg/cubic metre. By contrast, the density of fresh water is 1,000kg/cubic metre.
Air density, which is vital to aerodynamic and engine performance, is difficult to measure directly. Fortunately, there are two other properties of air that give a good indication of air density and are easy to measure. They are ……………….and ……………….
Air density, which is vital to aerodynamic and engine performance, is difficult to measure directly. Fortunately, there are two other properties of air that give a good indication of air density and are easy to measure. They are PRESSURE and TEMPERATURE.
In aviation, atmospheric pressure is normally measured in ………………., abbreviated to ……………….
In aviation, atmospheric pressure is normally measured in HECTOPASCALS, abbreviated to hPa.
If atmospheric temperature is normal but the pressure is high, you would expect the air density to be (higher/lower) than normal?
If atmospheric temperature is normal but the pressure is high, you would expect the air density to be HIGHER than normal?
If atmospheric pressure is about normal but the temperature is high, you would expect the air density to be (higher/lower) than normal?
If atmospheric pressure is about normal but the temperature is high, you would expect the air density to be LOWER than normal?
The International Standard Atmosphere (ISA) sea level:
a) Pressure is ……………….hPa
b) Temperature is ……………….°C
a) Pressure is 1013.2 hPa
b) Temperature is 15 °C
ISA conditions assume:
a) A pressure lapse rate of ……………….hPa for every ……………….ft gain in altitude from sea-level up to about 5,000 ft
b) A uniform temperature lapse rate of ……………….°C (or approximately ……………….°C) up to the tropopause which is assumed to be at about ……………….feet
a) A pressure lapse rate of 1 hPa for every 30 ft gain in altitude from sea-level up to about 5,000 ft
b) A uniform temperature lapse rate of 1.98 °C (or approximately 2 °C) up to the tropopause which is assumed to be at about 36,090 ft
Atmospheric air density reduces at?
a) A steady rate up to the tropopause
b) At a rapid rate initially, and then at a reducing rate as altitude is gained
c) At a rate that is solely dependent on pressure
b) At a rapid rate initially, and then at a reducing rate as altitude is gained
By comparison with sea-level values, pressure and density in the atmosphere are generally reduced to:
a) ……………….% by 8 - 10,000 ft
b) ……………….% by 18 - 22,000 ft
c) ……………….% by 34 - 41,000 ft
a) 75% by 8 - 10,000 ft
b) 50% by 18 - 22,000 ft
c) 25% by 34 - 41,000 ft
In actual atmospheric conditions, the altitude of the tropopause varies between about ……………….ft over the poles to a maximum of about ……………….ft over the equator.
In actual atmospheric conditions, the altitude of the tropopause varies between about 30,000ft over the poles to a maximum of about 60,000ft over the equator.
By comparison with lSA conditions, which are used to rate aerodynamic and engine performance:
a) A high temperature will indicate (high/low) density, and therefore (better/poorer) performance
b) A low temperature will indicate (high/low) density, and therefore (better/poorer) performance
c) A high pressure will indicate (high/low) density, and therefore (better/poorer) performance
d) A low pressure will indicate (high/low) density, and therefore (better/poorer) performance
a) A high temperature will indicate LOW density, and therefore POORER performance
b) A low temperature will indicate HIGH density, and therefore BETTER performance
c) A high pressure will indicate HIGH density, and therefore BETTER performance
d) A low pressure will indicate LOW density, and therefore POORER performance
The best density (and therefore performance) conditions are those with a (high/low) pressure and (high/low) temperature.
The best density (and therefore performance) conditions are those with a HIGH pressure and LOW temperature.
The worst density (and therefore performance) conditions are those with a (high/low) pressure and (high/low) temperature.
The worst density (and therefore performance) conditions are those with a LOW pressure and HIGH temperature.
Density altitude is the altitude in the ……………….that has the same density as the actual altitude.
Density altitude is the altitude in the INTERNATIONAL STANDARD ATMOSPHERE (ISA) that has the same density as the actual altitude.
Two locations have the same atmospheric temperature and pressure. At one, however, the air is very dry, while at the other, humidity is high. Aircraft performance will be better at the (dry/humid) location.
Two locations have the same atmospheric temperature and pressure. At one, however, the air is very dry, while at the other, humidity is high. Aircraft performance will be better at the DRY location.
