The wing flaps are movable panels on the inboard trailing
edges of the wings. They are hinged so that they may be extended downward
into the flow of air beneath the wings to increase lift and drag. Their
purpose is to permit a slower airspeed and a steeper angle of descent during
a landing approach. In some cases they are also used to shorten the takeoff
|The flap operating control may be an electrical or hydraulic control
on the instrument panel, or it may be a lever located on the floor to the
right of the pilot's seat. In any case, the control may be placed in various
positions by the pilot; UP, which raises flaps if they are in an extended
position; NEUTRAL, which allows the flaps to remain in whatever intermediate
position they may be at that time; and DOWN, which lowers the flaps if
they are in the retracted or intermediate position (Fig. 4-8). In addition
to the flap operating control, there is usually an indicator which shows
the actual position of the flaps. On most general aviation airplanes the
extent of travel of the flaps is approximately 30 to 40 degrees.
Extending and retracting the flaps has a very noticeable effect on the airplane's performance. With a constant power setting while maintaining level flight, the airspeed will be lower with flaps extended because of the drag they create. If power is adjusted to maintain a constant airspeed while in level flight, the airplane's pitch attitude will usually be lower with flaps extended.
When the flaps are extended, the airspeed should be at or below the airplane's maximum flap extended speed (Vfe), because if they are extended above this airspeed, the force exerted by the airflow may result in damage to the flaps. If the airspeed limitations are exceeded unintentionally with the flaps extended, they should be retracted immediately regardless of airspeed.
It is extremely important that the pilot form the habit of positively identifying the flap control before attempting to use it to raise or lower the flaps. This will prevent inadvertently operating the landing gear control and retracting the gear instead of the flaps, particularly when on or near the ground.
A complete discussion of the use and effect of flaps is provided in the chapter describing Landing Approaches and Landings.