Flaps vs Ailerons
Any aircraft is controlled mainly by the moveable surfaces fixed at the edges of the aircraft wings. Changing the position of any surface creates an unbalanced force or a couple around the center of the gravity of the aircraft and aircraft moves accordingly. There are two important moveable surfaces mounted on the main wings. The pair of surfaces mounted closer to the body of the aircraft is known as the flaps while the pair mounted outboard on the wing is known as the Ailerons. Even though they are mounted on the same wing they perform very different tasks in terms of controlling the aircraft.
More about Ailerons
As said earlier, Ailerons are control surfaces mounted at the trailing edge of the aircraft and used to roll; that is to rotate the aircraft around the axis through the nose and the tail of the aircraft, which is technically known as the X-axis of the inertial frame. Aileron is one of the fundamental control surfaces required for the maneuverability of the aircraft, although other methods can be employed for the roll control, they are not as effective as the ailerons.
The movement of the ailerons creates an angle in the lift vector by changing the pressure differences at the wings. Ailerons are fixed in a way such that one moves opposite of the direction of the other. This action creates a difference in the pressure on the upper surface of the wing; one creates a higher pressure and the other a lower pressure resulting in a difference in the lift created by the wings.
In modern aircrafts, the aircraft wing design is complex due to requirements (such as supersonic aircrafts) and other control surfaces are combined with the aileron. A control surface created by combining the aileron and the flaps is known as the flaperon while, in delta wing designs, aileron is combined with the elevator and that is known as the elevon.
More about Flaps
Flaps are two moving surfaces mounted at the trailing edge of the wing near the wing root. The sole purpose of the flaps is to increase the amount of lift created by the wing during the take off and the landing by increasing the effective area of the wings. In some commercial airliners, flaps are also installed at the leading edge.
This additional lift allows the aircraft to decrease the velocity and increase the angle of descent for landing. Since the wings generate more lift with flaps down, the stalling speed of the aircraft also goes down hence the wing can be tilted more than the usual, with which the aircraft can maintain a high angle of attack without stalling when the flaps are extended.
Many variants of the flaps exist, designed for operational variations of aircraft size, velocity, and complexity of the design of the aircraft.
What is the difference between Flaps and Ailerons?
• Ailerons are control surfaces, while flaps are not.
• Ailerons provide the lateral control of the aircraft, while flaps change the lift characteristics; i.e. Aircraft manoeuvring is assisted by ailerons, while flaps assist the way the aircraft take-off from the ground and while landing.
• Flaps are installed towards the wing root of both wings, while ailerons are installed at the wing tips.
• Flaps move in the same angle and direction (usually), while ailerons are designed to move in the opposite directions, to create the opposite effect on each wing.