What is the general purpose of secondary flight controls such as balance tabs, anti-servo tabs, servo tabs, and spring tabs?

• A. To reduce drag at high speed.
• B. To trim and assist in moving the flight controls.
• C. To increase lift.
• D. To provide structural support.

Answer: (B)

Secondary flight controls are there to lighten the pilot’s workload by helping to set and hold the airplane in a desired attitude. They do this by shaping how the primary control surfaces respond, making it easier to move them and to maintain a steady flight condition.

Balance tabs take some aerodynamic load off the primary surface by moving opposite to the surface’s deflection, easing the effort to move the control. Servo tabs move in response to the pilot’s input in a way that causes the main surface to move with less force from the pilot. Anti-servo tabs, on the other hand, move with the primary surface to increase the feel and stability, requiring a little more effort to move but helping prevent overcontrol and making the handling steadier. Spring tabs use a spring-driven bias to help return toward center and to contribute a trimming effect, reducing sustained control pressure.

Together, these devices trim the aircraft and assist in moving the flight controls, rather than directly increasing lift, reducing drag, or providing structural support.