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  Figure 2-8.  The wing camber remains the same physically, but the  ailerons change the “effective” camber of the wing and increase  or decrease lift to change lift vectors to affect turns. Figure 2-9.  Types of lift/drag devices. 2-5 Lift/Drag Devices Chord Lower camber Thickness Upper camber Chord length Leading edge Trailing edge Dive brake Dive brake Spoiler Spoiler Flap Flap