Flap (aircraft) - Physics Explanation

Physics Explanation

The general airplane lift equation demonstrates these relationships:

where:

• L is the amount of Lift produced,
• is the air density,
• V is the indicated airspeed of the airplane or the Velocity of the airplane, relative to the air
• S is the planform area or Surface area of the wing and
• is the lift coefficient which is determined by the camber of the airfoil used, the chord of the wing and the angle at which the wing meets the air (or angle of attack).

Here, it can be seen that increasing the area (S) and lift coefficient allow a similar amount of lift to be generated at a lower airspeed (V).

Extending the flaps also increases the drag coefficient of the aircraft. Therefore, for any given weight and airspeed, flaps increase the drag force. Flaps increase the drag coefficient of an aircraft because of higher induced drag caused by the distorted spanwise lift distribution on the wing with flaps extended. Some flaps increase the planform area of the wing and, for any given speed, this also increases the parasitic drag component of total drag.