If a glider with tapered wings, as shown in  Figure 3-14,  were  to begin a slip to the left with the left wing lower, the left  wing will have a relative wind more aligned with its chord  line and effectively higher airflow (airspeed) that generates  more lift as compared to the higher right wing with angled  relative wind, resulting in lower effective airflow (airspeed)  over that wing. This differential in airflow or relative airspeed  of the wings when taken to the extremes of the flight envelope  results in the higher wing stalling and often an inverted spin.  Depending on the exact wing shape, an elliptical wing can  have characteristics more like a tapered wing.  [Figure 3-14] Pilots should always consult the GFM and know what the  gliders limitations are concerning slips. the pressure on the rudder is released abruptly, the nose swings  too quickly into line and the glider tends to acquire excess speed. Because of the location of the pitot tube and static vents,  airspeed indicators in some gliders may have considerable  error when the glider is in a slip. The pilot must be aware of  this possibility and recognize a properly performed slip by  the attitude of the glider, the sound of the airflow, and the  feel of the flight controls. The use of slips has limitations. Some pilots may try to  lose altitude by violent slipping, rather than by smoothly  maneuvering, exercising good judgment, and using only a  slight or moderate slip. In short-field landings, this erratic  practice invariably leads to trouble since enough excess speed  may prevent touching down anywhere near the proper point,  and very often results in overshooting the entire field. The forward slip is a slip in which the glider’s direction of  motion is the same as before the slip was begun.  [Figure 3-30] The primary purpose of a forward slip is to dissipate altitude  without increasing the glider’s speed, particularly in gliders  not equipped with flaps, or if the spoilers are inoperative.  There are many circumstances requiring the use of forward  slips, such as a landing approach over obstacles and short- field landings, in which it is always wise to allow an extra  margin of altitude for safety in the original estimate of the  approach. In the latter case, if the inaccuracy of the approach  is confirmed by excess altitude when nearing the boundary of  the selected field, slipping can dissipate the excess altitude. If there is any crosswind, the slip is much more effective if  made toward the wind. If a slip is used during the last portion of a final approach,  the longitudinal axis of the glider must be aligned with the  runway just prior to touchdown so that the glider touches  down headed in the direction in which it is moving over  the runway. This requires timely action to modify the slip  and align the glider’s longitudinal axis with its direction of  travel over the ground at the instant of touchdown. Failure  to accomplish this imposes severe sideloads on the landing  gear and imparts violent ground looping tendencies. Assuming the glider is originally in straight flight, the wing  on the side toward which the slip is to be made should be  lowered by use of the ailerons. Simultaneously, the airplane’s  nose must be yawed in the opposite direction by applying  opposite rudder so that the glider’s longitudinal axis is at an  angle to its original flightpath. The degree to which the nose  is yawed in the opposite direction from the bank should be  such that the original ground track is maintained. The nose  should also be raised as necessary to prevent the airspeed  from increasing. Discontinuing the slip is accomplished by leveling the wings  and simultaneously releasing the rudder pressure, while  readjusting the pitch attitude to the normal glide attitude. If  Forward Slip Slideslip Figure 3-30.  A comparison of a forward slip to a sideslip. 3-16 Forward Slip