What is a servo trim tab?

• A. It is an auxiliary control positioned by cockpit movement and designed to create aerodynamic forces to assist in moving a control surface.
• B. It is a device that measures airspeed.
• C. It is a high lift device on the wing.
• D. It is a mechanism for retracting the landing gear.

Answer: (A)

A servo trim tab is a small auxiliary control surface on the trailing edge of a primary control surface that's moved by a cockpit-controlled servo mechanism. When you move the control, the servo tab deflects, and the aerodynamic force created by the tab’s deflection helps move the larger control surface. This reduces the effort the pilot must exert to reposition the surface and helps hold the airplane in the desired attitude with less manual force. It’s not a device for measuring airspeed, it’s not a high lift device like flaps, and it’s not involved in retracting landing gear.