2.4: Altimeter Flashcards
What is the function of the altimeter?
The altimeter measures the height of the airplane above a given level.
What is AGL?
Absolute altitude is the altitude above the surface. (Above Ground Level)
What is Absolute altitude?
Absolute altitude is the altitude above the surface. AGL - Above Ground Level
What is MSL?
True altitude is the actual distance above mean sea level. MSL is not susceptible to variation with atmospheric conditions.
What is Density altitude?
Density altitude is pressure altitude corrected for nonstandard temperatures variations.
What is Pressure altitude?
The altitude indicated when the barometric pressure scale is set to 29.92 on the altimeter.
It is the height above the standard datum plane of 29.92 in. of mercury.
Under what condition is Pressure altitude and Density altitude the same value?
at standard temperature
What are the International Standard Atmosphere (ISA) for temperature and pressure at sea level?
15 degree C (59 degree F) and 29.92 in of mercury (Hg).
What is True altitude?
True altitude is the actual altitude above mean sea level (MSL).
Altimeter setting is the value to which the barometric pressure scale of the altimeter is set so the altimeter indicates
true altitude at field level.
Under what condition is indicated altitude the same as true altitude?
When at sea level under standard conditions.
Under which condition will pressure altitude be equal to true altitude?
When standard atmospheric conditions exist.
If it is necessary to set the altimeter from 29.15 to 29.85, what change occurs?
700-foot increase in indicated altitude.
If a pilot changes the altimeter setting from 30.11 to 29.96, what is the approximate change in indication?
Altimeter will read 150 feet lower.
If a flight is made from an area of low pressure into an area of high pressure without the altimeter setting being adjusted, the altimeter will indicate
lower than the actual altitude above sea level.
If a flight is made from an area of high pressure into an area of lower pressure without the altimeter setting being adjusted, the altimeter will indicate
higher than the actual altitude above sea level.
Which condition would cause the altimeter to indicate a lower altitude than true altitude?
Air temperature warmer than standard.
Under what condition will true altitude be lower than indicated altitude?
In colder than standard air temperature.
Remember that altimeter readings are adjusted for changes in barometric pressure but not for changes in temperature. When one flies from warmer to cold air and keeps a constant indicated altitude at a constant altimeter setting, the plane has actually descended.
How do variations in temperature affect the altimeter?
Pressure levels are raised on warm days and the indicated altitude is lower than true altitude.
