Definition
The thrust produced by a turbine engine when its power lever is set to the lowest operating position with the engine still running. It is the minimum thrust the engine produces in normal operation, used as a defined reference point for certification, performance calculations, and certain flight phases such as approach and landing.
Plain English
The small amount of forward push a jet engine still produces when the throttle is pulled all the way back but the engine is left running.
Context Anchor
Used when discussing turbine engine power settings during taxi, descent, approach, and landing rollout.
Derivation
Idle comes from the Old English idel, meaning 'empty' or 'doing nothing.' Thrust comes from the Old Norse thrysta, 'to push.' Together the term describes the small push the engine still produces even when it is, in effect, doing nothing useful.
Why Pilots Care
Pilots need to know idle thrust to predict descent rates accurately and manage speed on approach without excessive drag.
Analogy
Like a car engine idling at a light: it is running and could move the vehicle with a slight brake release, but it is not accelerating.
Intuition Check
Do not read idle as off. Idle thrust means the engine is still running and still producing some push, just at the lowest normal power setting.
Example Sentence 1
The pilot brought the throttles to idle thrust during the descent to slow the aircraft for the approach.
Example Sentence 2
On final approach the aircraft continued with idle thrust, allowing speed to decrease naturally without additional drag.