Pressure altitude

pressure altitude

The altitude that corresponds to a given value of atmospheric pressure according to the ICAO standard atmosphere.

For aircraft flying above 18 000 feet MSL, it is the indicated altitude of a pressure altimeter at an altimeter setting of 1013.2 mb (29.92 in. of mercury); therefore, it is the indicated altitude above the 1013.2-mb constant-pressure surface. Aircraft flying below 18 000 feet MSL use the current altimeter setting as measured at the nearest airport and reported by air traffic control.

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1. A measure (or condition) of height, especially of great height, as a mountain top or aircraft flight level.

Value of the atmospheric pressure used to adjust the subscale of a pressure altimeter so that it indicates the height of an aircraft above a known reference surface.