Which of the following is a primary flight control surface?

• A. Aileron
• B. Wing Flaps
• C. Spoilers
• D. Trim Systems

Answer: (A)

Primary flight controls are the surfaces you actively move to change the aircraft’s attitude in flight. The surface that controls roll is the aileron, located on the trailing edge of the wings. When one aileron goes up and the other goes down, it creates differential lift between the wings, causing the aircraft to roll to one side.

Wing flaps are high-lift devices used to increase lift at lower speeds, mainly for takeoff and landing, not for actively steering the aircraft in flight. Spoilers can help reduce lift or assist with roll stress, and they’re often considered secondary controls rather than the main means to change roll. Trim systems adjust the control surfaces to hold a steady attitude with less pilot input, but they don’t provide the immediate attitude change you get from a primary control surface.

So the primary flight control surface responsible for rolling the aircraft is the aileron.