Plain English Meaning

How many times something spins all the way around in one minute. In a small airplane, it usually means how fast the engine — and on simpler aircraft, the propeller — is turning.

Full Definition

A unit of rotational speed expressing how many full turns a rotating component completes in one minute. In piston-engine airplanes, RPM most commonly refers to the speed of the engine crankshaft (and, on a fixed-pitch propeller, the propeller, since they turn together). On constant-speed propeller installations, engine RPM and propeller RPM are governed separately, and the tachometer typically displays propeller RPM.

Context Anchor

Seen on the engine-speed gauge and in engine starting, warm-up, and .