Definition
An engine in which fuel is burned inside enclosed cylinders, and the heat and pressure from that burning fuel push pistons that turn a crankshaft to produce mechanical power. In most piston-powered aircraft, the crankshaft drives the propeller.
Plain English
An engine that burns its fuel inside itself, using the resulting pressure to push moving parts that turn the propeller.
Context Anchor
Seen when learning how piston airplane engines produce power and why they need fuel, air, ignition, cooling, and oil.
Derivation
Internal means 'on the inside,' and combustion comes from the Latin combustio, meaning 'burning.' The name distinguishes it from external combustion engines (like a steam engine), where fuel burns outside the engine and heats a separate fluid. In an internal combustion engine, the burning happens inside the working part of the engine itself.
Why Pilots Care
Pilots rely on this engine type for reliable power in most light aircraft; understanding its operation supports proper fuel management, temperature control, and recognition of power loss.
Analogy
A typical car engine is also an internal combustion engine: fuel burns inside the engine, and that power turns moving parts. In an airplane, that power is used to turn the propeller.
Intuition Check
“Internal” does not mean the engine is inside the airplane. It means the burning that creates power happens inside the engine itself.
Example Sentence 1
The trainer is powered by a four-cylinder internal combustion engine driving a fixed-pitch propeller.
Example Sentence 2
A pilot must understand the internal combustion engine to diagnose rough running during climb.