Definition
A flameout in a turbine engine caused by a fuel-to-air ratio that is too low to sustain combustion. The mixture contains too little fuel relative to the air passing through the combustion section, and the flame goes out.
Plain English
The fire inside a jet engine goes out because there isn't enough fuel mixed with the air to keep it burning.
Context Anchor
Seen in turbine-engine operation and emergency procedures, especially when fuel flow is too low for the amount of air entering the engine.
Derivation
Lean refers to a fuel-air mixture with relatively little fuel compared to air. Flameout is just what it sounds like: the flame goes out. Combined, the term names the cause and the result.
Why Pilots Care
A lean flameout in flight can lead to an engine failure requiring immediate action such as restarting or emergency landing.
Grounding Statement
Picture a burner with a strong flow of air but very little fuel: the fire can no longer stay lit.
Intuition Check
Lean does not mean the engine is simply saving fuel. Here it means there is so little fuel compared with air that combustion can stop.
Example Sentence 1
The instructor explained that pulling the throttle back too aggressively at high altitude could cause a lean flameout.
Example Sentence 2
Pilots prevent lean flameout by enriching the mixture before the engine stops completely.