K 7 accident during aerotow in Melchtal results in severe injuries
On August 2, 1969, a K 7 glider experienced an accident during an aerotow near Melchtal, Switzerland. The glider, carrying a pilot and a passenger, was towed by a motor aircraft when it encountered turbulence and downdrafts. The tow rope broke at a low altitude, and the glider attempted an emergency landing with the rope still attached. The landing failed, resulting in the glider crashing and both occupants suffering severe injuries. The glider was destroyed, but there were no fatalities.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Crash - serious injury: The glider impacted the valley slope in a steep right turn, overturned, and was destroyed, with both occupants sustaining serious injuries.