Page 771 - PPL-engelsk 2025

Aircraft general knowledge

The static pressure causes the diaphragm can to either contract or expand.

The lower the pressure, the more the can will expand.

The instrument in the instrument panel looks like this.

There are 3 pointers for:
- Hundred feet

- Thousand feet

- Ten thousand feet

There is a rotary knob at the bottom of the altimeter. You set the desired

pressure (QNH, QFE or standard setting)

If it is set to the current pressure at sea level, it will show the altitude of the place
above sea level or above MSL (Mean Sea Level).

8.12.6.1 QNH

In the small window (Colesmann window) you can see that this altimeter has

inserted the value 1013, which is the pressure in the standard atmosphere at sea

level.

If the atmospheric conditions are standard, you can rely on the altimeter.

Over a long flight, the pressure at sea level changes, and it is necessary to set a

new value in the altimeter window.

This value is called QNH. QNH = pressure at sea level.

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 771