Page 741 - PPL-engelsk 2025

Aircraft general knowledge

If the aircraft was equipped with an EGT, you could see the temperature rise as

the mixture lever is pulled out (as you make rich mixture leaner, the EGT rises).

At a point when you have reached the mixture ratio of 1 kg of gasoline to 15 kg

of air, the temperature reaches its maximum (peak), and if you continue to lean

the mixture, the EGT falls! Now you cool the engine with excess air.

If you fly with a lean mixture at 4500 feet and goes down to 3000 feet, the

mixture ratio needs to be changed, and the mixture lever needs to… well what

does it need to do? Should it be pulled out or pushed in?

You are flying down to an altitude where there is more air. This will cause the

mixture to become too lean. So, you have to push the mixture lever in to get

more fuel.

As we climb to a higher altitude, the air becomes thinner. The less oxygen makes

the mixture rich.

This requires that we lean the mixture by reducing the amount of fuel. Follow
the instructions in the aircraft manual.

We lean by pulling the mixture lever out very carefully. When we can feel that

the engine is starting to run unevenly, we push the lever in until we have

maximum rpm (best PWR).

The diagram here shows when we should use

a rich mixture and when we should use a lean

mixture.

You should lean according to what is stated in the aircraft manual.

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 741