Text 3. Flaps

The flaps are auxiliary surfaces of the wing. They are hinged to the trailing edge of the wing. The flaps are located between the ailerons and the fuselage. The flaps are used during take off and landing. In order to leave the ground the airplane must have enough lift to support its weight. The lift may be increased by increasing the speed, by changing the attitude of the wing or by increasing the camber of the wing. During take-off it is necessary for the speed to be as high as possible in order to shorten the take-off run and get into the air as quickly as possible. It is dangerous for the airplane to increase the angle of attack too much. So it is possible to increase lift by using flaps. When the flaps are lowered the camber of the wing is increased. It increases drag. That is why during take off the flap angle should be small.

In landing flaps play a very important role. If the flap is well down the increase in drag will be considerable and the gliding angle will be greater. So we can see that the flaps permit slower and safer flight, lower landing speeds, steeper angles of descent. The flaps permit landing on short fields.

We may classify flaps according to their mechanical nature into plain flaps, split flaps, Fowler flaps and slotted flaps. In the plain flap the trailing edge is deflected downward. In the split flap the shape of the upper surface of the wing is unchanged when the flap is lowered. The split flap creates more drag than the plain flap The Fowler flap moves backward on a track. The slotted flap provides a slot or opening between the wing and the leading edge of the flap.