Definition
A powerplant configuration consisting of one piston-driven internal combustion engine, in which fuel-air mixture is ignited inside cylinders to drive pistons up and down, with that linear motion converted into rotational motion that turns the propeller.
Plain English
The aircraft has just one engine, and that engine works by burning fuel inside cylinders to push pistons back and forth, which turns the propeller.
Context Anchor
Seen in light-sport aircraft descriptions, aircraft specifications, and rules that describe what kinds of aircraft qualify as light-sport aircraft.
Derivation
Reciprocating comes from the Latin reciprocare, meaning 'to move back and forth.' That is exactly what the pistons do inside the engine — they travel up and down repeatedly, and that back-and-forth motion is what eventually spins the propeller.
Why Pilots Care
Affects whether an aircraft meets light-sport aircraft criteria and influences training, maintenance, and operating limitations.
Intuition Check
Do not read “single reciprocating engine” as “one piston” or “one cylinder.” It means the aircraft has one piston-type engine.
Example Sentence 1
To qualify as a Light-Sport Aircraft, the airplane must be powered by a single reciprocating engine.
Example Sentence 2
Preflight inspection of the single reciprocating engine includes checking oil level and magneto timing.