Definition
An engine stoppage caused by a fuel-air mixture that has become too lean to sustain combustion. With insufficient fuel relative to the air entering the cylinders, the mixture fails to ignite reliably and the engine quits.
Plain English
The engine stops because there is too much air and not enough fuel in the mixture being burned. With the mixture this thin, it can no longer keep firing and the engine shuts down.
Context Anchor
Seen in engine operation, carburetor adjustment, idle mixture checks, and mixture-control discussions.
Derivation
"Lean" in engine language means a mixture with relatively less fuel and more air than the ideal ratio. "Die-out" is plain English for the engine quitting. Together: the engine dies because the mixture went too lean to burn.
Why Pilots Care
Recognizing lean die-out prevents an unexpected engine stoppage and guides proper mixture adjustment to restore power.
Intuition Check
“Lean” here does not mean the aircraft is tilted or the engine is physically leaning. It means the fuel-air mixture has too little fuel to burn properly.
Example Sentence 1
The instructor demonstrated how aggressively pulling the mixture control toward idle cutoff at cruise power could lead to a lean die-out.
Example Sentence 2
During the preflight leaning test the mechanic noted the RPM drop that signaled lean die-out.