Page 745 - PPL-engelsk 2025

Aircraft general knowledge

8.9.6.2 Dry sump

If you are going to fly upside down and still be able to use the engine, it is

necessary to change the design so that instead of a “wet sump” you use a “dry

sump”.

In a wet sump, the oil collects at the bottom of the engine and is pumped from

there (as described in the previous section).

But if you fly upside down, this is not possible.

You then have the oil in a tank and

pump it around to all the

lubrication points in the engine.

A return pump sends the oil back
to the tank.

This is called a dry sump.

The principle is basically the same

as in a wet sump, except that the oil is enclosed.

8.9.6.3 Oil

Special aircraft oil is used. For engine break-in, pure mineral oil is used. Once the
engine has been run-in, you can switch to a self-cleaning oil.

A thicker oil is used in the summer than in the winter, unless you use a

combination oil, such as SAE 15W-50. In our aircraft, we use 15W50, which in

o
the winter (-18 C) has a viscosity of SAE 15, while SAE 50 is reached when the oil
o
is 100 C.

The higher the SAE number the oil has, the thicker it is.

Only use the right type of oil. There is usually a label on the dipstick that shows

which type of oil the aircraft in question uses.

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 745