Definition 1 of 2
Definition
The process of starting combustion of the fuel-air mixture in an engine cylinder by means of an electric spark produced at the spark plug. In a piston aircraft engine, ignition is supplied by magnetos, which generate the high-voltage current that jumps the spark plug gap and lights the mixture at the correct moment in the engine cycle.
Plain English
Ignition is how the engine lights the fuel inside its cylinders. A spark jumps across the spark plug at exactly the right moment, setting fire to the mixture of fuel and air so the engine runs.
Context Anchor
Seen in aircraft engine discussions, starting procedures, magneto checks, and troubleshooting when an engine is hard to start or runs rough.
Derivation
From the Latin 'ignis,' meaning fire. The word literally means 'the act of setting on fire' — which is exactly what the spark plug does inside the cylinder.
Why Pilots Care
Reliable ignition is essential for engine starting and continued smooth operation; any failure can prevent takeoff or cause in-flight issues.
Intuition Check
Ignition does not just mean turning a key or switch. In an aircraft engine, it means the actual lighting of the fuel-air mixture inside the engine.
Example Sentence 1
During the run-up, the pilot checked each magneto by switching the ignition from BOTH to L, then to R, watching for a normal RPM drop on each side.
Example Sentence 2
Before takeoff the ignition switch was set to both to ensure both magnetos were operating.