Which statement correctly describes the function of ailerons?

• A. They control pitch about the lateral axis.
• B. They control roll about the longitudinal axis and are mounted on the trailing edge near the wing tips.
• C. They control yaw.
• D. They are fixed surfaces with no control effect.

Answer: (B)

The main idea is that ailerons produce a rolling motion about the aircraft’s front-to-back axis (the longitudinal axis) by changing lift on the two wings. They are hinged on the trailing edge of each wing, typically toward the outer portions near the tips. When you deflect one aileron up and the other down, the wing with the up aileron loses lift while the other wing gains lift, causing the aircraft to roll to one side. This is different from pitch, which is controlled by the elevator about the lateral axis, and from yaw, controlled by the rudder about the vertical axis. Ailerons are movable surfaces, not fixed, and their location near the wing tips provides a longer moment arm to create the rolling effect. So describing them as controlling roll about the longitudinal axis and being mounted on the trailing edge near the wing tips is the correct description.