What happened
On July 13, 1968, a Pilatus PC-6/340 Porter, registration HB-FAV, was performing a cargo transport mission in the Swiss Alps. The aircraft, operated by the Club d’Aviation des Placettes, was tasked with delivering supplies, including food and heating fuel, to the Plan Névé mountain hut near the Grand Muveran.
During the final approach to the glacier, the pilot attempted to adjust the flight path to utilize the full length of a flat area on the glacier. However, the aircraft arrived too low and struck a patch of ice with significant force. This impact caused the aircraft to skid uncontrollably down the slope. The pilot applied full power in an attempt to regain directional control, which caused the nose to point uphill, but the momentum of the heavy load caused the plane to slide over 200 meters down the glacier. The descent ended when the tailwheel struck a moraine, leaving the fuselage parallel to the slope.
The investigation
Investigators examined the flight conditions, the aircraft's technical state, and the pilot's maneuvers. The investigation established that the aircraft was carrying approximately 500 kg of cargo and 100 kg of additional gear, bringing the total weight to roughly 1950 kg. The investigation also noted that the pilot encountered turbulence near a rocky ridge during the approach, which likely contributed to the loss of altitude.
Findings
- The primary cause of the accident was that the pilot landed too short of the intended landing area on unsuitable terrain.
- The aircraft landed on a patch of ice, which triggered the lateral skid.
- The landing conditions were considered marginal due to the narrowness of the glacier and the specific configuration of the landing site.
- The aircraft sustained heavy structural damage, with repair costs estimated at approximately 55% of the aircraft's value.
- There were no injuries to the pilot or the passenger, the latter of whom exited the moving aircraft during the slide.