Definition
A mixture control position that completely stops the flow of fuel to the engine cylinders, used to shut the engine down. Moving the mixture control to idle cutoff leans the fuel-air mixture to the point where no fuel is delivered, causing combustion to cease while the ignition is still on.
Plain English
The setting on the mixture control that turns off the fuel supply, so the engine runs out of fuel and stops. It is the normal way to shut down a piston aircraft engine.
Context Anchor
You encounter this during engine shutdown, when the checklist tells you to move the mixture control to idle cutoff.
Derivation
Called 'idle cutoff' because the mixture control is moved to the cutoff position while the engine is at idle power. 'Cutoff' simply means the fuel is cut off — stopped at its source.
Why Pilots Care
Proper use prevents engine damage from after-firing and ensures a controlled shutdown.
Intuition Check
Idle cutoff does not mean the engine is set to idle power. It means the fuel is cut off so the engine will stop.
Example Sentence 1
After taxiing back to parking, the pilot pulled the mixture control to idle cutoff and the engine wound down to a stop.
Example Sentence 2
The shutdown procedure requires verifying idle cutoff before switching off the ignition.