What is the main purpose of wing washout?

The main purpose of wing washout is to ensure that the root of the wing stalls before the tip. This design feature is crucial for maintaining aileron control during the stall phase. When washout is incorporated, the angle of incidence is reduced towards the tip of the wing compared to the root. As the aircraft approaches a stall condition, the root experiences a stall first, allowing the pilot to retain control through the ailerons, which remain effective at the tips. This sequence of stall progression helps prevent a full stall that could lead to a loss of control, particularly important in aircraft that may face situations requiring quick recovery or maneuverability.

While increasing lift at low speeds, reducing drag during cruise flight, and improving control during descent are important considerations in wing design, these factors are not the primary function of washout. The emphasis on stall characteristics uniquely positions washout as a critical design element for safety and control.