Definition
A unit of rotational speed expressing the number of complete turns a rotating component makes in one minute. In aviation, RPM most commonly refers to the rotational speed of an engine's crankshaft or a propeller, and is displayed on the tachometer in the cockpit.
Plain English
How many full turns something makes every minute. In an aircraft, it usually tells you how fast the engine or propeller is spinning.
Context Anchor
Seen on engine instruments, aircraft checklists, operating handbooks, and instructor explanations when setting or checking engine speed.
Derivation
From Latin 'revolvere' (to turn back, roll around) — the same root as 'revolve.' A revolution is one complete turn. 'Per minute' simply sets the time window for counting those turns.
Why Pilots Care
Correct RPM keeps the engine producing the right power without damage, ensures adequate thrust for takeoff and climb, and supports efficient fuel use in cruise.
Intuition Check
Here, revolution means one complete turn, not a political change. RPM is a spinning speed; by itself, it is not the same thing as engine power.
Example Sentence 1
During the run-up, the pilot set the engine to 1,700 RPM and checked each magneto for a normal drop.
Example Sentence 2
During the engine run-up the student verified that the RPM dropped smoothly when the magneto switch was moved to each position.