Plain English Meaning

A spinning wheel that is partly locked to the aircraft instead of being free to point any direction. Because it can only move a little, when the aircraft turns or tilts, the gyro feels that movement and the instrument shows it.

Full Definition

Gyroscopes mounted so the spin axis is held in a fixed position relative to the aircraft, with limited freedom of movement in only one or two axes. Because the gyro is partly tied to the airframe, it senses motion of the aircraft about the axis (or axes) in which it is restricted, rather than maintaining a free reference in space. Turn indicators and turn coordinators use this type of mounting.

Context Anchor

Seen in discussions of , especially when explaining how an instrument’s gyro is mounted inside the case.