Definition
A mechanical device used to connect or disconnect a driving shaft from a driven shaft, allowing power transmission to be engaged or interrupted without stopping the driving source.
Plain English
A part that lets one spinning shaft turn another, or lets it stop turning it, without having to switch off the engine or motor driving it.
Context Anchor
Seen in aircraft engine, starter, accessory, and helicopter drive-system discussions.
Derivation
From the Old English clyccan, meaning to grasp or seize. The mechanical clutch 'grips' the driving shaft to the driven shaft when engaged, and releases its grip when disengaged.
Why Pilots Care
Correct clutch use prevents sudden loads on the engine and transmission, reducing risk of damage during startup and shutdown.
Intuition Check
Do not think of clutch only as a hand grabbing something. In aviation mechanics, a clutch is the part in a machine that engages or disengages power between moving parts.
Example Sentence 1
The pilot waited for engine RPM to stabilize before engaging the rotor clutch.
Example Sentence 2
During shutdown the clutch was disengaged so the rotors could coast to a stop independently of the engine.