Factual Information
On 14 July 1983, a Segelflugzeug Ka 6 CR, registration HB-766, operated by Segelfluggruppe Lenzburg, was involved in an accident on the northwest slope of the Diablerets massif in Switzerland. The pilot, a Swiss citizen born in 1926, held a glider pilot license issued on 22 September 1971, with endorsements for winch launch and passenger flights. His total flight experience was 305 hours and 16 minutes with 314 landings, including approximately 25 hours on the accident type. His last medical examination on 19 August 1980 found him fit without restrictions.
The glider was manufactured in 1964 by Alexander Schleicher, with a certificate of airworthiness valid until 31 March 1984. At the time of the accident, its maximum takeoff weight of 300 kg was exceeded by 5 kg, but the center of gravity was within limits. The aircraft had accrued 2,823 hours and 25 minutes with 1,763 landings.
Narrative
The pilot was participating in an alpine gliding camp in Zweisimmen. On the day before the camp closed, he took off at 1126 local time in a towed launch, intending a long flight. When he had not returned by 1800, a search was initiated, but no trace was found that evening. The following day, around noon, the wreckage was discovered by a helicopter crew from the Federal Office of Civil Aviation (FOCA) on the northwest slope of the Diablerets at an elevation between 2,500 and 2,900 m. Recovery operations began immediately.
Witness accounts provided limited information about the flight. Witness A saw HB-766 around 1400 at about 3,000 m in the same area, both flying east-west along the slope, with the accident glider 20–30 m lower. Cloud cover was 6/8 with base just above 3,000 m, and thermals were 2–3 m/s. Witness B saw a glider, identified as HB-766, shortly after 1600 at 2,800 m between Sex Rouge and the Diablerets. At that time, point 3109 was in clouds, and the cable car station at 2,940 m was occasionally in fog. Witness B noted a long rotor cloud with surprising formation of cloud patches extending downward from west of the Diablerets to Col de la Croix. He observed that the glider did not avoid these cloud patches. Witness C reported hearing that HB-766 had made cloud flying transmissions. Witness D saw two yellow gliders between 1200 and 1400 near Wispile that reported cloud flying by radio and disappeared into a cloud; one may have been HB-766. Based on witness B's statements, the impact likely occurred around 1645.
Wreckage and Injuries
The glider collided with a steep rock face at an elevation of about 2,900 m, coordinates 281 250 / 129 100. The aircraft was completely destroyed, with fragments scattered over a height of 300 m. The forward fuselage was shattered, the rear fuselage broken behind the main spar, the tail surfaces torn off, the right wing broken outside the main fitting and shredded, and the left wing broken into three parts. The seat belts remained intact but were pulled from their anchors. The radio was not found, and the battery box and central wheel were found 300 m below the impact point in snow. Instruments except the compass and turn coordinator were broken; the turn coordinator switch was on. No functional defects were detected in the remaining parts.
The pilot sustained fatal injuries due to massive blunt force trauma, including an open skull and brain injury and a torn heart muscle. Toxicology tests showed no alcohol or drugs, and carbon monoxide was within normal range. No organic disease that could have caused the accident was found. No fire occurred.
Cause
According to the investigation, the collision with the rock wall resulted from the pilot not avoiding cloud patches and very probably flying in clouds without the required training.