Skip navigation

Drift

The drift, crabbing and flying on course exercise is taught so students can develop an awareness of the effects of the wind speed and direction on the groundpath of the aircraft and the proper technique to counteract these. This usually requires an understanding of how the wind will alter the ground path of an aircraft, relative to the direction it is flying in free-flight. Start these exercises in the circuit, or on high wind days when the ground drift will be more apparent. It is important to point out to the student that while flying ‘across’ the wind, that the wings can be level, the yaw string straight back, and no rapid swinging motion will be seen with respect to the horizon. All of the most noticeable motion will be relative to objects on the ground as opposed to the horizon.

To fly on course, (e.g. a ground path straight along the downwind during crosswind conditions) requires picking an object on the ground in the distance to aim for, and then turning the aircraft towards the wind and levelling off. The students then look off in the distance at the ground object and determine if it does not appear to shift to the left or right. Two effects are involved in the resulting ‘crab’. When the pilot looks ahead over the nose of the glider to the horizon there is no apparent swinging motion and no banking; there is no turn. When the pilot looks off in the distance at the ground object it is only gets larger and does not move to the left or right.  The outline for this exercise is:

  1. Student performance on rest of flight checked as required.
  2. Instructor reviews straight and level flight. 
  3. Instructor chooses a crosswind course, and directs the student to fly with the wings level.
  4. Instructor directs student’s attention to a reference that draws attention to a point on the horizon.  Student asked to observe the drift off of this reference.
  5. Instructor coaches student to assume a crab to correct this drift. Directs student to observe the aircraft’s condition while crabbing. The wings should be level and the yaw string straight back.
  6. Crabbing in the circuit coached by the instructor.