Which of the following is a secondary flight control surface?

• A. Ailerons and elevators
• B. Spoilers and flaps
• C. Trim tabs and horizontal stabilizer system
• D. Slats and leading edge devices

Answer: (C)

Secondary flight control surfaces are those that adjust the aircraft’s stability and trim rather than directly commanding an attitude change. Trim tabs and the horizontal stabilizer system fit this role because they provide a subtle, continuous adjustment to balance the airplane and maintain a desired pitch without the pilot having to apply constant force. The trim tabs change the tailplane’s incidence to produce the necessary pitching moment, while the horizontal stabilizer system can set the overall tailplane angle to hold a steady flight condition.

In contrast, primary controls like the ones that control roll and pitch directly—ailerons and elevators—are used for immediate attitude changes in response to pilot input. Spoilers and flaps primarily modify lift and drag to aid speed management and landing, not to maintain trim. Slats and other leading edge devices are high-lift devices used to enhance takeoff and landing performance, not to provide trim or stability adjustments.