What happened
On July 5, 1968, a pilot initiated a training flight from Altenrhein Airport in a Diamant-18 glider, registration HB-914. The flight was intended to be a familiarization session, with the aircraft scheduled to be relocated to Sweden shortly thereafter. The flight proceeded via Rheineck and Heered toward Rorschacherberg. At approximately 17:15 CET, while at an altitude of roughly 1,000 meters, the pilot released from the tow plane unexpectedly. Following the release, the glider appeared to enter a circling pattern before descending rapidly. The aircraft eventually struck the steep northern slope of the Bischofsberg near Heiden at a high rate of speed. The impact was nearly vertical, and the pilot was killed.
The investigation
The investigation examined the aircraft's maintenance history, the pilot's experience, and the environmental conditions at the time of the accident. The HB-914 had recently undergone significant maintenance, including the installation of new reinforced camber flaps. While witnesses reported seeing the wings flutter and hearing metallic noises—leading to initial speculation of a collision with a nearby ski lift—forensic analysis of the wreckage and paint traces ruled out any contact with external structures. Investigators also reviewed the pilot's medical history and the cockpit environment, noting that the aircraft lacked an upgraded ventilation system, which could have led to extreme heat within the cockpit during the summer afternoon.