Wind striking an aileron from below couples with the edge of the aileron, directing airflow from the underside of the wing to the upper surface of the aileron. Aileron deflected down increases the angle of attack on that part of the wing; force can be increased by deflecting the aileron to a greater degree. The upward-moving aileron has the opposite effect as its leading edge extends into the airflow below the wing. Upwind aileron spoils lift on that wing, and deflections cause the aircraft to roll into the wind.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the effect of wind on an aileron?
Wind striking an aileron from below produces an upward force. When the aileron is in the downward position, wind strikes it from below and produces an upward force. When the aileron is in the upward position, wind strikes it from above and produces a downward force. The edge of the aileron directs airflow from the underside of the wing to the upper surface of the aileron, creating a lifting force added to wing lift. Form drag is produced as airflow strikes the exposed leading edge of the aileron.
What is the function of ailerons on takeoff? Ailerons allow the aircraft to bank left or right by altering the lift on each wing. Aileron deflection changes the effective shape of the airfoil of the outer wing portion. Aileron begins fully deflected and is reduced as it becomes more effective with increased airspeed. As the aircraft accelerates during takeoff, the pilot reduces aileron deflection after the ailerons become effective to maintain wings level.
How should ailerons be positioned when landing in a crosswind?
When landing in a crosswind, you keep the upwind aileron deflected into the wind through roundout, touchdown, and rollout. Ailerons control lateral position over the runway and maintain flight track along the centerline. After touchdown position ailerons fully into the wind, this keeps the upwind wing from lifting and keeps the aircraft laterally aligned with the runway. As the aircraft slows down you need to increase crosswind control inputs, not decrease them. Full aileron deflection into the wind is held as you slow to taxi speed.
I use the aileron to keep the wing-low stance. I intensify the aileron movement into the breeze which blocks the windward airfoil from emerging and guarantees the aircraft stays steered into the breeze.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
