Definition
A spark plug misfire condition caused by an excessively rich fuel-air mixture, in which unburned fuel and combustion deposits accumulate on the spark plug electrodes and short out the spark, preventing ignition in that cylinder.
Plain English
When too much fuel and not enough air reaches a cylinder, the extra fuel and soot build up on the spark plug and stop it from sparking. The plug is 'blown out' by the rich mixture.
Context Anchor
Seen in turbine engine start, acceleration, and flameout troubleshooting discussions.
Derivation
Rich' refers to a fuel-air mixture with too much fuel relative to air. 'Blowout' borrows the everyday sense of a flame being put out — here the spark, not a flame, is being killed off by fuel fouling.
Why Pilots Care
Can prevent engine start or cause sudden shutdown if the mixture is not leaned correctly.
Analogy
A fire needs both fuel and air. If the fuel overwhelms the available air, the fire can go out instead of burning stronger.
Grounding Statement
In a rich blowout, fuel is present, but there is not enough air in the burning area for the flame to continue.
Intuition Check
“Rich” does not mean better or stronger here. It means fuel-heavy: too much fuel compared with the air available for burning.
Example Sentence 1
Extended ground operation at full rich mixture can lead to rich blowout, leaving one cylinder running rough until the plugs are cleaned.
Example Sentence 2
Leaning the mixture early prevented a rich blowout during taxi.