Plain English Meaning

Small adjustable flaps on the engine cover that the pilot can open or close to let more or less air pass over the engine, controlling how cool or warm the engine stays.

Full Definition

Hinged, movable doors on the engine cowling that the pilot opens or closes to control the amount of cooling air flowing around an air-cooled piston engine. Opening them increases airflow through the engine compartment to remove heat; closing them reduces airflow to keep the engine warm and reduce drag.

Context Anchor

Seen in aircraft engine cooling procedures, especially during climbs, descents, and - operations.