What happened
On August 22, 2004, a DISCUS B glider, registration HB-1949, crashed into a mountainside in the municipality of Obergesteln, Switzerland. The pilot was participating in a national advanced cross-country flight training course in the Alps. After completing several supervised flights with an instructor, the pilot was assigned a solo local flight.
The flight began at approximately 13:28 local time, following a 15-minute aero-tow from Münster airfield. During the flight, the aircraft entered an uncontrolled state at a low altitude. Eyewitnesses reported seeing the glider descending vertically with high rotational and vertical velocity, striking a 30-degree slope at an elevation of approximately 2,200 meters. The impact resulted in the fatal loss of the pilot and the total destruction of the aircraft.
The investigation
Investigators examined the wreckage and the flight conditions at the time of the accident. The aircraft's maintenance records were found to be complete, with the last annual inspection having been conducted in March 2004. The investigation confirmed that the aircraft was within its weight and balance limits, specifically noting that the center of gravity was at the most forward allowable position.
Technical analysis of the wreckage showed no evidence of pre-existing mechanical failures, assembly errors, or defects in the control surfaces. Medical examinations of the pilot revealed no evidence of sudden health impairment or intoxication that could have contributed to the accident. Furthermore, the pilot's GPS logger provided no significant data regarding the final moments of the flight.
Findings
- The aircraft was flying with a forward center of gravity, a configuration which, according to the manufacturer, makes a spin unlikely but can lead to a spiral dive if the minimum airspeed is lost.
- Meteorological conditions involved weak and localized thermal activity, which limited the available lift and the operational altitude to approximately 2,600 meters.
- The pilot was flying at a speed near the minimum sink rate, a common tendency in weak thermals, which reduced the margin for error.
- The aircraft entered an uncontrolled flight state, likely due to the aerodynamic effects of turbulence or falling below the minimum flying speed, leaving insufficient altitude to recover before hitting the terrain.