Definition
A control on certain gyroscopic instruments — most commonly the attitude indicator and the directional gyro — that locks the gyro mechanism in a fixed position. Pulling or pushing the knob secures the gyro so it will not tumble during unusual attitudes, ground handling, or while spinning up. On older or simpler instruments, the caging knob is also used to manually re-erect the gyro to a level reference after it has been disturbed.
Plain English
A small knob on the front of a gyro instrument that lets the pilot lock the spinning part inside it. Locking it keeps the instrument from getting confused during rough manoeuvres, and it can also be used to reset the instrument to a known starting position.
Context Anchor
Seen when discussing errors in reading or setting the attitude indicator during instrument flight.
Derivation
From 'cage', meaning to confine or hold in place. The gyro is mechanically 'caged' — held still inside its housing — so it cannot move freely. 'Uncaging' releases it so it can spin and sense aircraft movement again.
Why Pilots Care
Protects delicate gyros from damage during ground handling and restores accurate pitch and bank indications after they have tumbled or drifted.
Intuition Check
Do not think of the caging knob as a pitch control or trim control. It only affects the attitude instrument, not the airplane’s actual nose position.
Example Sentence 1
After the instrument tumbled during a steep turn, the pilot used the caging knob to re-erect the attitude indicator to level flight.
Example Sentence 2
After a steep bank the attitude indicator showed an incorrect pitch attitude, so the pilot pressed the caging knob to re-erect the gyro.