Definition 1 of 2
Definition
The lowest stable engine speed setting used while an aircraft is on the ground. For a turbine engine, it is the minimum RPM at which the engine runs reliably during taxi and ground operations, producing very little thrust. For a piston engine, it is the lowest RPM at which the engine continues to run smoothly with the throttle fully closed.
Plain English
The slowest the engine is allowed to run while the aircraft is on the ground without stopping or running rough. It produces just enough power to keep the engine alive and the aircraft moving slowly during taxi.
Context Anchor
Seen in engine operating procedures, taxi procedures, and aircraft manuals that distinguish ground idle from flight idle.
Derivation
Idle' comes from the Old English idel, meaning 'empty' or 'doing no work.' An idling engine is running but not producing useful work. 'Ground idle' specifies the idle setting used on the ground, distinguishing it from flight idle, which is set higher so the engine can spool up quickly if needed in the air.
Why Pilots Care
Proper use prevents engine overheating, excessive fuel consumption, or damage during ground operations and ensures safe transitions between ground and flight modes.
Intuition Check
Ground idle does not mean the engine is shut down. It means the engine is running at its lowest normal power setting for ground use.
Example Sentence 1
After landing, the pilot pulled the power lever back to ground idle for the taxi to the ramp.
Example Sentence 2
In hot weather, maintaining ground idle helped keep the engine temperatures within limits during extended ground holds.