Pressure altitude

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In aviation, pressure altitude is the indicated altitude when an altimeter is set to 1013 hPa (29.92 inHg US and Canada). It is primarily used in aircraft performance calculations, and in high-altitude flight (Class A airspace in the United States, which is controlled airspace at or above 18,000 feet).

The relation between static pressure and pressure altitude is defined in terms of the properties of the International Standard Atmosphere (ISA). Up to 36,090 ft this relation can be expressed as:

[z =\left (1-\left(\frac\right)^ \right ) \times \frac]

Where:

z = pressure altitude (feet)
[P_o] = static pressure (hPa)

Pressure altitude

See also