Turn indicators/coordinators rely on which gyro characteristic?

• A. Rigidity
• B. Precession
• C. Inertia
• D. Nutation

Answer: (B)

Turn indicators and coordinators use the gyroscope’s precession. When the aircraft begins to turn, torque is applied to the spinning gyro. With the gyro mounted on a tilted axis, that torque causes the spinning axis to precess, deflecting the gimbal and the indicator in the direction of the turn. The tilt lets the device sense both yaw and roll, giving a readable rate-of-turn cue during a banked turn.

Rigidity in space would keep the axis fixed rather than moving in response to turn-rate torque, so it wouldn’t produce the deflection used for signaling. Nutation is a brief wobble that isn’t the steady deflection used for indicating turn rate, and inertia is simply resistance to change rather than the mechanism that drives the visible indication.