What is a servo tab?

• A. A navigation aid used to align the aircraft with runway heading.
• B. An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite the primary control to provide an aerodynamic assist in the movement of the control.
• C. A tab on the vertical stabilizer that reduces yaw.
• D. A secondary control lever used for altitude hold.

Answer: (B)

A servo tab is an auxiliary surface mounted on a primary flight control surface that automatically moves in the opposite direction to the pilot’s input to provide aerodynamic assistance. When you deflect a control, the servo tab deflects the other way, creating a pressure difference that helps move the main surface in the desired direction, reducing the force you must exert. This make-control feel lighter, especially on large or high-load surfaces, and is distinct from a trim tab, which is set to hold a surface in a chosen attitude without automatically helping to move it. It’s also not a navigation aid or altitude-hold device—those serve different functions.