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Aircraft general knowledge
8.8.1.5 Compression ratio
The compression ratio is the engine's performance. It indicates how many times
the displacement volume must be compressed to make room in the combustion
chamber between the cylinder head and the cylinder top.
The compression ratio is found as:
displacement / combustion chamber volume
For gasoline engines, the compression ratio is approximately 10:1, for diesel
engines approximately 20:1.
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8.8.2 Aeroplane engine
The engine in a gasoline-powered aircraft is typically an engine with horizontally
opposed cylinders. The engine is an air-cooled 4-stroke piston engine with 4, 6
or 8 horizontal opposed cylinders with 2, 3 (as shown here) or 4 cylinders on each
side of the crankcase, respectively.
The carburetor is located at the bottom, and the air filter is located below it.
8.8.2.1 Cylinders
Engines can be constructed with cylinders
arranged in a V-shape, as shown here. However,
this is not practical to have in the nose of an aircraft
and is only rarely used.
It is far better to make engines with “horizontally
opposed cylinders”.
Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 725
