Page 744 - PPL-engelsk 2025

Aircraft general knowledge

The principle of the wet sump can

be seen here.

The oil is sucked from the sump

through a filter to the suction side

of the engine-driven oil pump,

from here on to the pressure side
of the pump.

The oil is put under pressure, which is determined by a valve's opening spring,

and comes to the oil filter. The oil is led from the filter via a relief valve to the

cooler, which has a thermostatically controlled bypass valve that determines
whether the oil should pass or run around the cooler.

The oil then continues into the engine's oil channels for lubricating the crankcase
bearings, main bearings, connecting rod bearings, camshaft, valve lifters. It also

cools and lubricates cylinders, pistons, etc.

From the various lubrication points, the oil flows back to the sump.

The pump presses oil through the oil filter through the oil valve. If the filter is

clogged, the bypass valve opens, and the valve in the filter itself closes.
Unfiltered oil now circulates to the engine, but lubrication with dirty oil is better

than no lubrication. With the pressure valve at the top right, you can adjust the

oil pressure.

In the cabin we have the opportunity to check the oil temperature and pressure.

Normal oil pressure: 65-85 Psi.

o
o
Oil temperature: 45 C to 100 C

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 744