Definition
Describes an engine that dissipates the heat produced by combustion by passing outside air directly over the cylinders and surrounding metal fins, rather than circulating a liquid coolant through the engine.
Plain English
An air-cooled engine gets rid of its heat using moving outside air instead of using liquid like the radiator system in a car.
Context Anchor
Seen in airplane engine descriptions, preflight inspection, climb operation, and engine temperature discussions.
Derivation
Straightforward compound: 'air' as the cooling medium, 'cooled' meaning heat is carried away. The phrase tells you the cooling method directly.
Why Pilots Care
Air-cooled engines depend on airflow to stay within safe temperature limits. On the ground, during prolonged climbs, or at low airspeeds with high power, cooling airflow drops and cylinder head temperatures can rise quickly. Pilots manage this by limiting ground time, adjusting climb speeds and pitch attitude, and watching engine instruments.
Intuition Check
Air-cooled does not mean the engine cools itself no matter what. It means the engine depends on a steady flow of outside air over its hot parts to carry heat away.
Example Sentence 1
Most light training airplanes use an air-cooled piston engine, which is why prolonged ground operations on a hot day require careful attention to engine temperatures.
Example Sentence 2
During high-power operations, pilots of air-cooled engines watch cylinder head temperature closely to avoid overheating.