by Jonathan M. Stern
Secondary Flight Controls
The flaps and trim tabs are secondary flight controls. Spoilers, found on the Flight Simulator Lear 35, are also secondary flight controls.
Flaps serve two purposes. By increasing the amount of lift that the wing produces at a given speed, they decrease the necessary speed required for landing and, in some cases, takeoff. They also create drag, which can be beneficial when a relatively short runway has obstacles near the landing threshold (see Figure 2.7).
Figure 2.7. Flaps lower the stall speed and increase drag. The arrow points to the lowered flap.
The added drag allows a relatively steep descent to be made without a substantial increase in airspeed. Flaps are usually hinge-mounted onto the trailing edge of the wing inboard of the ailerons. Unlike ailerons, flaps move up and down together. They can be actuated hydraulically, mechanically, or electrically from controls in the cockpit. In the Flight Simulator Cessna 182RG, the wing flaps are electrically controlled and can be set to 10, 20, 30, or 40 degrees of deflection.
Flaps may be selected by clicking with the mouse the flap control lever at the desired setting or with the keyboard in accordance with the following table:
|Control||Keyboard (F keys on top)||Keyboard (F keys left side)|
The purpose of trim tabs is to relieve control pressures that the pilot otherwise has to maintain in steady flight. The trim tab is a miniature airfoil mounted on a primary control surface. The tab is moved up or down (or side to side on a rudder) as necessary to relieve pressure on the control (yoke or rudder pedal).
The Flight Simulator Cessna is equipped with an elevator trim tab, although some aircraft also have rudder and aileron trim. The elevator trim is controlled by pressing Keypad 1 for up trim or Keypad 7 for down trim.
Spoilers spoil lift by disrupting smooth airflow over the wings. Spoilers provide a means, in addition to flaps, of increasing rate of descent without increasing speed. With the Lear 35A and the Schweizer 2-32, spoilers are extended and retracted by clicking with the mouse on the spoiler position indicator or by pressing the slash (/) key.