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Diagram showing the face of the "three-pointer" sensitive aircraft altimeter displaying an altitude of 10,180 ft (3,100 m). 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]
A chart showing how much the true altitude of an aircraft is below the altimeter reading ("indicated altitude") without correcting for temperature. The colder the ambient temperature, the lower the plane is — thus the saying "From hot to cold, look out below". [8] Modern aircraft use a "sensitive altimeter".
Above the TA, the aircraft altimeter pressure setting is changed to the standard pressure setting of 1013 hectopascals (equivalent to millibars) or 29.92 inches of mercury, with the aircraft altitude will be stated as a flight level instead of altitude. In the United States and Canada, the transition altitude is 18,000 ft (5,500 m). [5]
QFE - is the barometric altimeter setting that causes an altimeter to read zero when at the reference datum of a particular airfield (in practice, the reference datum is either an airfield center or a runway threshold). In ISA temperature conditions the altimeter will read the height above the airfield/runway in the vicinity of the airfield.
It indicates altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances in which the aircraft’s altimeter would be unable to give a useful altitude readout. Examples would be landing at a high altitude or near sea level under conditions of exceptionally high air pressure.
Indicated altitude is the reading on the altimeter when it is set to the local barometric pressure at mean sea level. In UK aviation radiotelephony usage, the vertical distance of a level, a point or an object considered as a point, measured from mean sea level ; this is referred to over the radio as altitude .(see QNH ) [ 2 ]
An aeronautical chart is a map designed to assist in the navigation of aircraft, much as nautical charts do for watercraft, or a roadmap does for drivers. Using these charts and other tools, pilots are able to determine their position, safe altitude, best route to a destination, navigation aids along the way, alternative landing areas in case of an in-flight emergency, and other useful ...
Thus the standard consists of a tabulation of values at various altitudes, plus some formulas by which those values were derived. To accommodate the lowest points on Earth, the model starts at a base geopotential altitude of 610 meters (2,000 ft) below sea level, with standard temperature set at 19 °C.