Tow rope strikes ASK 21 wing on slack release during tow-position demo
The right wing of an ASK 21 was marked by the tow rope at Bex Aérodrome (Switzerland) after a slack-rope release during a tow-position demonstration; the instructor and student were uninjured. After a Piper PA-18 aerotow from RWY 33 the instructor demonstrated extreme tow positions to the student on downwind. With the glider offset to the left of the tug, the rope went slack and the instructor released it. The rope whipped up, struck the right wing and broke, and a piece jammed in the partially extended right airbrake. He rejoined RWY 33 by the shortest path and landed in a field at the runway edge, rolling out onto the runway.
- Aerotow r33, extreme-tow demo: On 27 June 2015 an instructor and a student launched an ASK 21 from runway 33 at Bex on a Piper PA-18 aerotow. On the downwind leg the instructor began an exercise to demonstrate extreme tow positions to the student: first he placed the glider below the tug so the student could feel the turbulence, then offset to the right and climbed to the tug's height and slightly above, still offset right.
- Tug deviates left mid-exercise: The instructor saw the tug deviating left from its axis. To avoid an emerging critical position he repositioned the glider on the tug's axis, slightly above it, and waited for the tug's path to stabilise before continuing the exercise.
- Slack rope with glider left of tug: Continuing the exercise the instructor placed the glider to the left of the tug and observed the tow rope going slack. He judged the situation to be becoming critical.
- Instructor releases slack rope: The instructor released the tow rope at the glider end.
- Rope strikes wing, jams airbrake: The released rope whipped up and struck the right wing of the glider. It broke on impact; a piece jammed in the partially extended right airbrake.
- Short return, field landing on r33: The instructor announced his intentions by radio and chose the shortest path back to runway 33. The glider touched down in a field at the runway edge and rolled out onto runway 33. Damage was limited to marks of the cable ring on the right wing; both occupants were uninjured.