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.
Plain English
A piston engine. Pistons move up and down inside cylinders, and that movement is turned into the spinning motion that drives the propeller.
Context Anchor
Seen in airplane fuel, oil, engine-start, warm-up, and preflight discussions for many training airplanes.
Derivation
From Latin reciprocare, meaning 'to move back and forth.' The name describes exactly what the pistons do — they reciprocate (travel back and forth) inside the cylinders, unlike a turbine engine where parts spin continuously.
Why Pilots Care
Most light training aircraft use reciprocating engines; pilots must understand mixture, throttle, and oil management to operate them safely and avoid engine damage.
Analogy
It works on the same principle as a car engine: pistons going up and down inside cylinders, with a crankshaft turning that motion into rotation. The main difference is that the crankshaft turns a propeller instead of wheels.
Intuition Check
Do not read “reciprocating” as “responding” or “giving back.” In this engine term, it means back-and-forth piston motion.
Example Sentence 1
The Cessna 172 is powered by a four-cylinder reciprocating engine driving a fixed-pitch propeller.
Example Sentence 2
The student adjusted the mixture control to maintain smooth operation of the reciprocating engine at cruise altitude.