What is the purpose of a flap on an aircraft?

The purpose of a flap on an aircraft is primarily to improve lift at lower speeds. Flaps are movable surfaces on the wings that extend and retract, and when deployed, they increase the camber of the wings, as well as their surface area. This change in wing shape allows the aircraft to generate more lift at slower airspeeds, which is especially beneficial during takeoff and landing phases of flight.

By enhancing lift at lower speeds, flaps enable the aircraft to safely operate at the slower speeds required for those critical phases. This increased lift allows for shorter takeoff and landing distances, providing improved aircraft performance and safety.

In contrast, options such as increasing stall speed, enhancing control surface stability, or reducing drag at high speeds do not align with the primary function of flaps. Instead, flaps are designed to maximize lift in lower-speed flight, making them a vital component in an aircraft's ability to perform during critical phases of flight.