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In aviation, pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is 29.921 inches of mercury (1,013.2 mbar; 14.696 psi) as measured by a barometer. [2] It indicates altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances ...
Flight level. In aviation, a flight level ( FL) is an aircraft's altitude as determined by a pressure altimeter using the International Standard Atmosphere. It is expressed in hundreds of feet or metres. The altimeter setting used is the ISA surface pressure of 1013 hPa or (29.92 inHg ).
Altimeter setting. Altimeter setting is the value of the atmospheric pressure used to adjust the scale of a pressure altimeter so that it indicates the height of an aircraft above a known reference surface. [ 1] This reference can be the mean sea level pressure ( QNH ), the pressure at a nearby surface airport (QFE), or the "standard pressure ...
With this system flights nearing 40,000 ft (12,192 m) were possible, but the lack of atmospheric pressure at that altitude caused the pilot's heart to enlarge visibly, and many pilots reported health problems from such high altitude flights. [44] Some early airliners had oxygen masks for the passengers for routine flights.
The density altitude is the altitude relative to standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation. In other words, the density altitude is the air density given as a height above mean sea level. The density altitude can also be considered to be the pressure altitude ...
True airspeed. An analog true airspeed indicator for an airplane. The pilot sets the pressure altitude and air temperature in the top window using the knob; the needle indicates true airspeed in the lower left window. Here the speed is displayed both in knots (kn) and miles per hour (mph). The true airspeed ( TAS; also KTAS, for knots true ...
Reference pressure of about 29.92 inHg (1013 hPa) is showing in the Kollsman window. An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. [ 1] The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water.
Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...