ASW 19 B rises above DR 400/180 R on aerotow; towplane crashes

A towplane pilot was seriously injured when he lost control of the towplane and crashed after the glider it was towing rose high and would not release at Mollis; towplane destroyed, the glider lightly damaged and its pilot unhurt. On a familiarization aerotow (glider pilot ~46 h total / 0 h on type; a previous attempt had been aborted for the same reason), the glider oscillated after liftoff and rose high above the towplane. The pilot reported operating the release, but the rope did not release. The continued overshoot lifted the towplane's tail; it lost control, banked left, and crashed wing-first onto the grass.

1. Familiarization aerotow on type: This was a second type-familiarization aerotow after a first attempt was aborted for the same reason; any difficulty was briefed to be aborted by releasing the tow rope.
2. Unsuitable preparatory training: Between the aborted attempt and the accident flight, the pilot flew a short mixed sequence of aerotow and winch training with a five-week gap before returning — an unsuitable preparation.
3. Aerotow takeoff from rwy 01: Takeoff at 16:44 LT from rwy 01 at Mollis. The glider's flight path after liftoff was unsteady (observers described 'wave motion', 'pumping', 'oscillation').
4. Glider overshoots above tug: The glider rose above the towplane, then dropped hard onto the runway, then rose above the towplane again and held the high tow position.
5. Release operated but rope not released: The pilot reported operating the release handle to abort, but the rope did not release and the towplane remained attached; the release mechanism was found in acceptable condition.
6. Tug LOC from continued overshoot: The glider's continued high position lifted the towplane's tail; the towplane pilot lost control, banked left, and crashed wing-first onto the grass.
7. Tug destroyed; glider lightly damaged: The towplane was destroyed and its pilot seriously injured; the glider landed hard, was steered back to the centerline, and stopped with light damage, its pilot uninjured.