What happened
On April 10, 2012, a DG-800 B glider, registration HB-2331, departed from Hausen am Albis for a cross-country flight. The pilot, flying solo under VFR conditions, initially climbed to approximately 2,000 meters. After navigating through various regions including the Sihltal and towards the Wägitalersee, the flight path directed the aircraft toward the Bockmattlipass area.
During the final phase of the flight, the aircraft entered a steep, rising terrain feature. Flight data logs indicate that in the final 20 seconds of the flight, the aircraft experienced a significant loss of altitude of approximately 45 meters and a reduction in ground speed of about 25 km/h. The DG-800 B subsequently collided with a steep, snow-covered slope at an altitude of approximately 1,720 meters. The pilot sustained injuries that ultimately led to death from hypothermia, as the wreckage remained undiscovered under snow for 18 days.
The investigation
Investigators examined flight logs, aircraft data from a FLARM device and a GPS logger, and meteorological records. The investigation focused on the flight path, the meteorological conditions at the time of the accident, and the aircraft's technical state. The wreckage was found by a group of mountaineers nearly three weeks after the occurrence. The investigation also looked into the pilot's medical history and the effectiveness of the search and rescue response.
Findings
- The pilot chose a flight trajectory that led into a steep terrain chamber at an insufficient altitude.
- Severe downdrafts associated with the prevailing Föhn weather conditions were underestimated.
- The pilot likely attempted a flight maneuver that resulted in a stall.
- The aircraft was operating within its weight and center of gravity limits, and no pre-existing technical defects were found.
- The pilot's previous stroke had not been reported to the medical examiner, meaning required follow-up evaluations had not been conducted.
- The emergency locator transmitter (ELT) carried on board was non-functional.
- A delay in reporting the pilot as overdue—seven and a half hours after the scheduled return—significantly hindered the chances of a timely rescue.