What happened
On July 13, 2003, a DG-400 motor glider, registration HB-2127, crashed on the southwest flank of Weissfluhjoch in the Canton of Graubünden. The pilot had departed from St. Gallen-Altenrhein earlier that morning, intending to fly toward the Engadin and Valais regions.
At approximately 12:18 local time, the aircraft was observed approaching the Weissfluhjoch-Weissfluhgipfel cable car lines from the Davos direction. While flying at an altitude of roughly 100 m AGL, the pilot initiated a sharp, steep right-hand turn approximately 100 meters before reaching the cable car wires. During this maneuver, the aircraft experienced a stall, leading to a sudden loss of control and a subsequent impact with the terrain. The impact and following fire destroyed the aircraft and caused the death of the pilot.
The investigation
Investigators examined the wreckage and interviewed witnesses who observed the flight path and the final maneuver. The investigation confirmed that the cable car wires were properly marked with orange spheres and documented on both Swiss glider and ICAO aeronautical charts at an altitude of 100 m AGL.
Technical inspections of the DG-400 revealed that the engine was in the retracted position and the aircraft's center of gravity was within limits. While a required airworthiness directive had not been implemented, this was not considered a factor in the accident. Medical examinations of the pilot showed no presence of drugs or alcohol; however, the presence of ketones in the urine suggested a state of ketosis, potentially indicating hypoglycemia or a lack of food intake.
Findings
- The primary cause of the accident was a collision with the terrain resulting from a loss of control following a stall during an avoidance maneuver.
- Strong downdrafts were present near the terrain due to wind gusts of up to 16 knots.
- The pilot's physiological state, specifically potential hypoglycemia or dehydration, may have contributed to poor decision-making or inadequate airspace monitoring.
Safety action
To prevent similar occurrences, the investigation noted that inadequate hydration or low blood sugar can impair a pilot's ability to maintain situational awareness. It is recommended that pilots carry sufficient fluids and snacks to avoid such conditions.