Types of ailerons

Types of Ailerons

Rolling motion by Ailerons

What are Ailerons?

Ailerons are located at the rear side of aircraft wings. They are typically rectangular in shape with well defined length and made of metal to achieve stability and rigidity. The ailerons function by working in opposite directions, i.e, when one moves in the upward direction the other moves in downward direction. They are generally used to alter the lift on aircraft. Ailerons can be used to either increase or decrease the lift, which happens as they are deflected from the center line of the wing. As a result, the ailerons contribute in tilting the aircraft either left or to the right. The aircraft tilts towards the aileron which is tilted in the upward direction, as a result of the force build up on the wing pointing down.

During the flight, the wings' ailerons do not deflect with the same magnitude, the directions are opposite and the displacement of the ailerons also is unequal. This contributes to the fact that the nose of the aircraft can be tilted in such a way that it can counteract any adverse yaw formation when the airplane is banking at an angle.

Adverse yaw is the condition achieved by an aircraft, when there is a difference between the desired and the actual direction of the nose which it is pointing towards, while turning. This phenomenon can be visualized or observed better by noting the movement of the tail of the aircraft which is a more obvious sign. The cause of this adverse yaw is the aileron that is deflected downwards which causes additional drag compared to the other aileron. As a result, this drag tends to pull the aircraft out of the turn path.
Hence, the main aim of the designers becomes to reduce the effect of this adverse yaw on the aircraft, for which, they have come up with few moderations;

TYPES OF AILERONS

• DIFFERENTIAL TYPE AILERONS
• FRISE TYPE AILERONS

I) DIFFERENTIAL TYPE AILERONS

Differential type Ailerons

A typical differential aileron operates and functions in a process which is quite identical to that of a symmetrical or traditional aileron except for the part where the aileron which gets deflected upwards is deflected at a greater distance than the one which is deflected in the downward direction.
This is done, mainly to contradict the symmetrical ailerons where the aileron that is deflected upwards tends to cause a reduction of a significant amount of lift as it reduces the camber. Subsequently, the downward deflected wing leads to an increase in both camber and lift force. This increase in lift also contributes in increasing the overall drag on the aircraft which ultimately tends to turn or yaw the aircraft in flight around an imaginary vertical axis.
To tackle this situation, the differential ailerons are designed in a way, such that the drag induced by the descending wing balances the lift-induced drag of the second wing as a function of the angle which it is deflected to. Hence, this tends to greatly decrease the adverse yaw.

II) FRISE TYPE AILERONS

Frise Type Ailerons

Another phenomenon introduced to tackle the consequences of the adverse yaw is the frise type aileron. The arrangement is made in a manner to reduce the adverse yaw. The design or the shape of the frise type ailerons is such that when the aileron is bent in the downwards direction, the whole of the upper surface of the main aircraft and the aileron tend to have a no-rough and uninterrupted contour, which ultimately results in having a reduced drag. In the meanwhile, the aileron which is deflected in the upwards direction causes an excessive drag as it projects the bottom surface of the aircraft.

Therefore, the contour of the aileron surface is itself improved in frise type ailerons. The objective is achieved when the drag created by the lower aileron equalizes with the opposite wing, resulting in a reduction of adverse yaw.

This type of aileron also produces to develop a slot in the system so that the air can flow smoothly over the lower aileron. With this, the system becomes even more effective at higher angles of attack.

Note: Even after these moderations, a gentle rudder action is still needed whenever ailerons are brought into action.

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