Definition
A condition in which the gyroscopic instruments (such as the attitude indicator and heading indicator) have been mechanically locked in place by their caging mechanism, preventing the gyro rotors from responding to aircraft movement. While caged, the instruments cannot provide accurate attitude or heading information.
Plain English
The gyro instruments have been locked in place with a knob or lever, so they are frozen and cannot show the airplane's actual attitude or heading until they are unlocked.
Context Anchor
Seen in instrument takeoff checks and error discussions, especially with older attitude or heading instruments that have a cage or uncage control.
Derivation
A 'cage' in mechanical terms is a frame that holds something in a fixed position. To 'cage' a gyro means to lock its spinning rotor and gimbals in a centered position so they cannot move freely. The aviation term comes directly from this mechanical sense.
Why Pilots Care
Attempting flight with gyros caged produces false attitude and heading indications, which is a common cause of loss of control on instrument takeoffs.
Grounding Statement
Before an instrument takeoff, the pilot confirms the gyro instruments are free to operate so they can show the aircraft’s movement as soon as the takeoff begins.
Intuition Check
Caged does not mean the gyros are safely ready for flight. Here it means locked or restrained; for normal instrument flying, they must be released and operating correctly.
Example Sentence 1
During the pre-takeoff check, the pilot noticed the attitude indicator was frozen and realized the gyros were still caged.
Example Sentence 2
Before taxiing across the rough ramp, the instructor confirmed the gyros were caged to avoid damage.