What electro-mechanical device can be used to move a control surface?

• A. Servo
• B. Gyroscope
• C. Altimeter
• D. Relay

Answer: (A)

A servo is the electromechanical device used to move a control surface. It combines a small motor, gears, and a feedback mechanism to convert electrical signals into precise angular movement, allowing a flight controller to position a surface like an aileron, elevator, or rudder accurately. The controller sends a signal that specifies the desired angle, and the servo moves to that position while using feedback to hold or adjust as needed. The other options don’t fit this role: a gyroscope measures rotation, not movement of surfaces; an altimeter measures altitude; a relay is just a switch to control power and doesn’t directly move a surface.