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Meteorology

3.3.6.4 Pressure altitude and density altitude

In meteorology, there are many definitions of altitude.

When discussing aircraft performance at various altitudes, this is usually

expressed in relation to the standard atmosphere.

This altitude is called ISA (International Standard Atmosphere).

If standard values are not available when flying (which is rarely the case), the

current values can be converted to the corresponding altitude in ISA.

There are two steps in this calculation. First, we calculate our current altitude

in relation to the standard pressure of 1013 hPa.

This gives us: pressure altitude.

If we look at the temperature at this pressure altitude, it follows the standard

atmosphere’s values, meaning pressure altitude also corresponds to the
standard atmospheric conditions (molecular distance is as it should be at this

altitude).

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 238