What is the function of ailerons on an aircraft wing?

Ailerons are essential control surfaces located on the trailing edge of an aircraft's wings. Their primary function is to create aerodynamic forces that facilitate rolling, which is the rotation of the aircraft around its longitudinal axis. When a pilot moves the control yoke or stick to one side, one aileron moves upward while the other moves downward. This differential movement alters the airflow over the wings. The wing with the upward-moving aileron experiences decreased lift and increased drag, while the wing with the downward-moving aileron experiences increased lift. This differential lift causes the aircraft to roll towards the side where the aileron is down, allowing for coordinated turns and maneuvers in the air.

The other options, while related to aircraft performance, do not accurately describe the primary purpose of ailerons. Ailerons do not specifically increase drag for high-speed flight nor do they directly provide lateral stability, which is more associated with dihedral angle and other design features. Additionally, ailerons do not reduce lift during landing; that function is primarily performed by flaps and other flight control systems designed for landing configurations. Understanding the specific role of ailerons in creating roll helps clarify their importance in aircraft control and maneuverability.