The fuselage is the portion of the airframe to which the wings and empennage are attached. The fuselage houses the cockpit and contains the controls for the glider, as well as a seat for each occupant. Glider fuselages can be formed from wood, fabric over steel tubing, aluminum, fiberglass, Kevlar® or other composites, or a combination of these materials. [Figure 2-7]
Wings and Components
Glider wings incorporate several components that help the pilot maintain the attitude of the glider and control lift and drag. These include ailerons and lift and drag devices, such as spoilers, dive brakes, and flaps. Glider wings vary in size and span from 12.2 meters (40 feet) to 30 meter (101.38 feet).
A wing may consist of a single piece attached to the fuselage to as many as four pieces (on one side).
The ailerons control movement around the longitudinal axis, known as roll. The ailerons are attached to the outboard trailing edge of each wing and move in opposite directions.
Moving the aileron controls with the control stick to the right causes the right aileron to deflect upward and the left aileron to deflect downward. The upward deflection of the right aileron decreases the effective camber (curvature of the wing surface), resulting in decreased lift on the right wing. [Figure 2-8] The corresponding downward deflection of the left aileron increases the effective camber, resulting in increased lift on the left wing. Thus, the increased lift on the left wing and decreased lift on the right wing causes the glider to roll to the right.
Gliders are equipped with devices that modify the lift/drag of the wing. These high drag devices include spoilers, dive brakes, and flaps. Spoilers extend from the upper surface of the wing, interrupting or spoiling the airflow over the wings. This action causes the glider to descend more rapidly. Dive brakes extend from both the upper and lower surfaces of the wing and help to increase drag.
Flaps are located on the trailing edge of the wing, inboard of the ailerons, and can be used to increase lift, drag, and descent rate. [Figure 2-9] Each flap type has a use depending on aircraft design. When the glider is cruising at moderate airspeeds in wings-level flight, the flaps can sometimes be set to a negative value (up from trail or level) for high speed cruising in some high efficiency gliders. When the flap is extended downward, wing camber is increased, and the lift and the drag of the wing increase.
Gliders are generally equipped with simple flaps and these flaps can generally be set in three different positions which are trail, down or negative. [Figure 2-10] When deflected downward, it increases the effective camber and changes the wing’s chord line, which is an imaginary straight line drawn from the leading edge of an airfoil to the trailing edge. Both of these factors increase the lifting capacity of the wing.
Negative flap is used at high speeds at which wing lift reduction is desired to reduce drag. When the flaps are extended in an upward direction, or negative setting, the effective camber of the wing is reduced, resulting in a reduction of lift produced by the wing at a fixed angle of attack and airspeed. This action reduces the down force, or balancing force, required from the horizontal stabilizer.