Definition
A position on the mixture control of a reciprocating aircraft engine in which the flow of fuel to the cylinders is completely shut off while the engine is still running. Moving the mixture lever to idle cut-off starves the engine of fuel and is the normal method used to shut it down.
Plain English
The setting on the mixture lever that stops fuel from reaching the engine, allowing it to run out of fuel and stop cleanly. It is the standard way pilots turn off a piston engine.
Context Anchor
Seen in engine start, shutdown, and emergency checklists for piston aircraft.
Derivation
The phrase combines 'idle' (the lowest running speed of the engine) and 'cut-off' (to stop or sever something). The position sits past the idle setting on the mixture control, where fuel flow is cut off entirely.
Why Pilots Care
Ensures the engine stops cleanly without residual fuel that could cause after-firing or damage during shutdown.
Analogy
Like turning off the valve on a propane grill so the flame dies out completely rather than just lowering the heat.
Grounding Statement
Idle cut-off is a fuel shutoff position, not a throttle setting.
Intuition Check
Do not read “idle” here as simply low engine speed. In idle cut-off, the engine is not being set to idle; its fuel supply is being stopped.
Example Sentence 1
After parking on the ramp, the pilot pulled the mixture control to idle cut-off and the engine wound down to a stop.
Example Sentence 2
The shutdown checklist calls for setting the mixture to idle cut-off before switching off the magnetos.