Accident de K 7 lors d'un remorquage aérien à Melchtal entraîne des blessures graves

Le 2 août 1969, un planeur K 7 a été impliqué dans un accident lors d'un remorquage aérien près de Melchtal, en Suisse. Le planeur, transportant un pilote et un passager, était remorqué par un avion à moteur lorsqu'il a rencontré des turbulences et des courants descendants. Le câble de remorquage s'est rompu à basse altitude, et le planeur a tenté un atterrissage en campagne avec le câble encore attaché. L'atterrissage a échoué, entraînant le crash du planeur et des blessures graves pour les deux occupants. Le planeur a été détruit, mais il n'y a eu aucune perte de vie.

1. Aerotow into valley: The K 7 glider with pilot and passenger was aerotowed from Sarnen-Kägiswil into the Melchtal, climbing along the valley flanks to use expected updrafts.
2. Low entry altitude: The tow entered the Melchtal at a relatively low height above terrain compared with local recommendations, leaving limited safety margin in the narrow valley.
3. Downdrafts and turbulence: After initial climb in weak lift, the tow encountered zones of downdraft around 3–6 m/s and strong turbulence, causing frequent towrope slack and altitude loss.
4. Towrope weak link breaks: Shortly after a steep 180° turn near the village of Melchtal, the front 540 kg weak link on the 60 m towrope failed following a rope slack and re-tension event at low height.
5. Emergency landing attempt: With the rope still attached, the glider pilot initiated a right turn toward the right valley flank to attempt an uphill emergency landing on a selected field, reportedly operating the release handle but not shedding the rope.
6. Rope contacts power line: During the low-altitude maneuvering, the slack towrope hung from the glider and contacted the lower 9 kV power line, abruptly pulling the glider toward the slope and into a steep descending right turn.
7. Crash - serious injury: The glider impacted the valley slope in a steep right turn, overturned, and was destroyed, with both occupants sustaining serious injuries.