Plain English Meaning

A piston engine. Pistons move up and down inside cylinders, and that movement is turned into the spinning motion that drives the propeller.

Full Definition

An internal combustion engine in which pistons move back and forth inside cylinders, and that linear motion is converted into rotary motion by a crankshaft to turn the propeller. Fuel and air are burned inside each cylinder, the resulting expansion pushes the piston down, and the crankshaft converts the up-and-down motion into the rotation that drives the propeller.

Context Anchor

Seen in airplane fuel, oil, engine-start, warm-up, and preflight discussions for many training airplanes.