Page 239 - PPL-engelsk 2025

Meteorology

If it gets warmer, the air expands, causing the molecular distance to become

larger, corresponding to a higher altitude in the standard atmosphere.

If the temperature decreases, the air contracts, and the molecules are closer

together, making conditions match those at a lower altitude in the standard
atmosphere.

When calculating the effect of temperature on pressure altitude, we get:

density altitude.

Pressure altitude is the altitude relative to 1013 hPa - i.e. the altitude

reading of an altimeter when set to 1013.25 hPa

Pressure altitude is also called Pressure Altitude, PA

If a temperature correction is made to this altitude, the density altitude is

obtained.

Density altitude is the altitude that the current altitude corresponds to

in the standard atmosphere.

Density altitude is also called Density Altitude or ISA (altitude in the

International Standard Atmosphere)

We use both parts, for example to calculate take-off and landing distance.

Example, pressure altitude:

Given:

o
1000 ft: 13 C

o
MSL: 993 hPa, 15 C

Set up it looks like this

Calculate standard atmospheric conditions (ISA)

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 239