Definition
A cylindrical metal component that moves up and down inside the cylinder of a reciprocating engine. Driven by the expanding gases of combustion on the power stroke, the piston transfers that force through the connecting rod to the crankshaft, converting the straight-line motion into rotary motion that ultimately turns the propeller.
Plain English
A solid metal plug that slides up and down inside an engine cylinder. When fuel burns above it, the pressure pushes it down, and that pushing motion is what makes the engine turn.
Context Anchor
Seen in piston-engine descriptions, engine inspections, compression checks, and maintenance discussions about cylinders, rings, and engine wear.
Derivation
From the French 'piston' and Italian 'pistone,' meaning a large pestle — the heavy rod used to pound or press something inside a container. The image fits: a piston pounds and presses inside the cylinder with each stroke.
Why Pilots Care
Understanding pistons helps pilots grasp how reciprocating engines produce power and why maintenance is critical for reliability.
Analogy
Think of a bicycle pump handle moving inside the pump barrel. The piston in an engine moves the same way inside its cylinder — except instead of you pushing it, burning fuel pushes it.
Intuition Check
A piston is not the whole engine and not the cylinder itself. It is the moving part inside the cylinder that gets pushed by combustion.
Example Sentence 1
During the overhaul, the mechanic measured each piston for wear before fitting new rings.
Example Sentence 2
During overhaul, the mechanic inspected the piston for scoring and wear.