What happened
On June 23, 2019, an ASG 32 glider, registration HB-3497, departed from Sion Airport (LSGS) for a private flight. After being towed into the air, the glider separated from the tow plane near Mayens-de-la-Zour. The flight, which included a pilot and one passenger, proceeded through a period of weak thermal activity and ridge soaring.
During the final stages of the flight, the pilot attempted to maintain altitude by flying close to the terrain along the ridge between Prabé and Crê_ta-Besse. At approximately 15:40, the aircraft crossed a ridge line at a height of only about 30 meters. While executing a left-hand turn with a 40-degree bank angle, the glider's trajectory brought it back across the ridge toward the terrain. Shortly after 15:41, the aircraft struck a steep rocky wall at an altitude of 2,337 meters, approximately 20 meters below the crest. The impact was severe, and the wreckage slid roughly 100 meters down the slope. Both the pilot and the passenger, both experienced glider pilots, sustained fatal injuries.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) analyzed flight data from the onboard LX9000 flight computer, the Flarm collision avoidance system, and Open Glider Network (OGN) tracking. The investigation examined the aircraft's technical condition, the pilot's experience, and the meteorological environment. Investigators reviewed the aircraft's weight and balance, confirming the ASG 32 was within prescribed limits. The investigation also looked into the pilot's decision-making process regarding flight tactics in poor thermal conditions and the lack of an Emergency Locator Transmitter (ELT) on the aircraft.