What is the primary function of an aileron on an airplane?

The primary function of an aileron on an airplane is to control roll. Ailerons are hinged or movable surfaces located on the outer wings of an aircraft, and they operate in opposition to one another. When one aileron is deflected upwards, the corresponding aileron on the opposite wing is deflected downwards. This differential movement creates a difference in lift between the wings, causing the aircraft to roll in the direction of the lifted wing.

This rolling motion is essential for maneuvering during flight, allowing pilots to bank the airplane into turns or to stabilize it. Unlike other control surfaces, such as elevators which control pitch (up and down movement) or rudders which control yaw (left and right movement), ailerons specifically facilitate the aircraft's ability to roll. Therefore, this clearly makes the control of roll the primary function of ailerons on an airplane.