Definition
A method of igniting the fuel-air mixture in a reciprocating engine cylinder by using an electrical spark, produced by a spark plug, to start combustion at a precise point in the engine's operating cycle.
Plain English
The engine burns its fuel by lighting it with an electric spark, the same way a car engine fires each cylinder.
Context Anchor
Seen in discussions of reciprocating engine operation, spark plugs, ignition systems, and how the engine produces power.
Derivation
From 'spark' (a small electrical discharge) and 'ignition' (the act of setting something alight). The name describes exactly how combustion begins: a spark sets the mixture alight.
Why Pilots Care
Spark ignition systems are central to engine reliability; pilots must understand them to interpret magneto checks, troubleshoot rough running, and recognize the difference from diesel compression-ignition engines.
Analogy
Similar to the spark that lights a gas stove burner each time you turn the knob.
Intuition Check
Spark ignition does not mean the engine only gets one spark when it starts. It means sparks are repeatedly made at the right time while the engine is running.
Example Sentence 1
Most light aircraft use spark ignition engines, which is why a magneto check is part of every runup.
Example Sentence 2
During the annual inspection the mechanic replaced the spark plugs to restore proper spark ignition performance.