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

On a familiarization aerotow from Mollis (pilot ~46 h total / 0 h on type; previous attempt 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; the towplane lost control, banked left, and crashed wing-first onto the grass. Contributing factors: inadequate glider control inputs, unsuitable preparatory training, release mis-operation, limited situational awareness. Towplane destroyed; its pilot seriously injured. Glider lightly damaged; its pilot uninjured.

1. Familiarization aerotow on type: Second type-familiarization aerotow on ASW 19 B HB-1714 behind Robin DR 400/180 R HB-EZX, both owned by Segelfluggruppe Glarnerland at Mollis (LSMF). Glider pilot 46:43 h total, 0 h on this type. The first familiarization attempt on 8 Apr 2017 had been aborted for the same reason (glider rose above tug after liftoff). The pre-flight brief specified that any difficulty must be aborted by releasing the tow rope.
2. Unsuitable preparatory training: Between the aborted first familiarization attempt and the accident flight: two dual ASK 21 aerotow flights same day (8 Apr), four dual ASK 21 winch-launch flights on 14 Apr, then a 5-week gap. SUST cause finding identified this training mix as unsuitable for addressing the glider pilot's aerotow-position-holding difficulties.
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 glider pilot reported operating the tow release handle to abort, as briefed. However the rope did not actually release — the towplane remained attached. SUST identified mis-operation of the release as one of the contributing factors; the release mechanism itself was found in acceptable technical 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: Towplane destroyed; towplane pilot seriously injured. Glider landed hard on the grass a few meters left of the runway, then was steered back onto the centerline and came to a stop after passing the displaced threshold of rwy 19; lightly damaged (fuselage underside); glider pilot uninjured. SUST contributing factors: inadequate glider control inputs, unsuitable preparatory training, mis-operation of release, limited situational awareness. No safety recommendations issued.