Definition
A method of engine cooling in which heat produced by combustion is removed by air flowing directly over the outside of the cylinders, rather than by a circulating liquid coolant. Most light aircraft reciprocating engines are air cooled, with finned cylinder surfaces and engine baffling that direct ram air from the propeller and forward motion across the hottest parts of the engine.
Plain English
The engine is kept from overheating by air blowing across it, instead of by a water or coolant system like in a car.
Context Anchor
Seen in discussions of aircraft reciprocating engines, engine temperature, climb performance, and ground operation.
Why Pilots Care
Air-cooled engines are lighter and simpler than liquid-cooled ones, which is why most light aircraft use them, but they require monitoring of cylinder temperatures to avoid overheating.
Grounding Statement
When the airplane is moving, air flows through the engine area and carries heat away from the engine.
Intuition Check
Air cooled does not mean the engine stays cool just because it is outdoors. It means the engine is built so moving air carries heat away from specific hot parts.
Example Sentence 1
Because the engine is air cooled, the pilot lowered the nose slightly during the climb to increase airflow and keep the cylinder head temperatures in the green.
Example Sentence 2
Preflight inspection includes checking the cooling fins on an air-cooled engine for cracks or debris.