to the glider pilot. However, the pilot still needs proficiency  in performance of forward slips to correct for possible errors  in judgment of the landing approach. The  forward slip is a slip in which the glider’s direction of  motion remains the same as before the slip was begun. If there  is any crosswind, the slip is much more effective if made into  the wind. If the glider is originally in straight flight, the wing  on the side that the slip is to be made should be lowered by  using the ailerons. Simultaneously, the glider’s nose must  be yawed in the opposite direction by applying opposite  rudder so 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.  The primary purpose of forward slips is to dissipate altitude  without increasing the glider’s airspeed, particularly in  gliders not equipped with flaps or those with inoperative  spoilers/dive brakes. There are many circumstances requiring  the use of forward slips, such as in a landing approach over  obstacles and in making off-field landings. 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 may dissipate the  excess altitude. The use of slips has definite 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 off-field landings, this erratic  practice invariably leads to trouble since enough excess  speed may result in preventing touchdown anywhere near  the touchdown point, and very often results in overshooting  the entire field. A sideslip, as distinguished from a forward slip, is one  during which the glider’s longitudinal axis remains parallel  to the original flightpath, but in which the flightpath  changes direction according to the steepness of the bank.  [Figure 7-28]  The sideslip is important in counteracting  wind drift during crosswind landings and is discussed in the  crosswind landing section of this chapter. Sideslip 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 the glider touches down  in the direction in which it is moving. This requires timely  action to decrease the slip to maintain ground track alignment  with the landing zone. Failure to accomplish this alignment  imposes severe sideloads on the landing gear and imparts  violent ground looping tendencies. Decreasing 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 the pressure on the rudder is released abruptly, the nose  swings too quickly into line and the glider tends to acquire  excess airspeed. 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. Common errors when performing a slip include: •  Improper glidepath control. •  Improper use of slips. •  Improper airspeed control. •  Improper correction for crosswind. 7-26 Figure 7-28.  Forward slip and sideslip. Forward slip Sideslip