What happened
On May 16, 1985, a Robin DR400-180R with registration HB-KAE departed Sion Airport at 08:26 local time for an alpine flight. The aircraft carried the pilot and three passengers with no prior aviation experience. After climbing to approximately 11,500 feet and flying past Evolène, the pilot attempted to cross the Col d'Hérens toward the Zmutt valley.
Approximately one kilometer before the pass, while approaching the Glacier de Ferpècle, the aircraft encountered strong downdrafts and lost altitude rapidly. The pilot initiated a left turn to return to the valley behind them. During this maneuver, the plane struck the snow-covered glacier surface with its right wingtip, which broke off. The aircraft then cartwheeled on the snow before coming to rest upside down. No fire occurred.
The pilot sustained serious facial injuries, likely exacerbated by the lack of shoulder harnesses. The three passengers escaped uninjured. Rescue operations were delayed by deteriorating weather but eventually evacuated all occupants via helicopter.
The investigation
The Federal Commission for Aviation Accident Investigation examined the technical condition of the aircraft, the pilot's qualifications, and the meteorological data. Technical inspections revealed no mechanical failures; the airframe was within weight and balance limits, and maintenance records were current. The pilot held a private license with 75 total flight hours, including only 12 hours on the Robin type.
Meteorological forecasts had predicted relatively stable conditions with light winds at altitude, which the investigation deemed overly optimistic for the actual mountain terrain encountered. Witness statements and flight reconstruction indicated the pilot had stopped monitoring his altimeter after passing Evolène, relying instead on visual assessment of sufficient clearance over the pass.
Findings
The collision with the ground was caused by a failed turnaround attempt at low altitude following unexpected turbulence. Contributing factors included:
- HB-KAE (the aircraft) encountered severe downdrafts not anticipated by the pilot.
- The pilot's mountain flying tactics were flawed, specifically the decision to ignore altimeter readings in favor of visual estimation.
- Overconfidence due to previous successful crossings of the same pass with this aircraft type.
- Reduced pilot performance potential due to altitude effects, though no incapacitation was confirmed.
Safety action
The report highlighted the danger of relying on optimistic weather forecasts for mountain flying and the critical importance of maintaining situational awareness regarding altitude in turbulent terrain. It noted that the absence of shoulder harnesses contributed to the severity of the pilot's injuries.