What happened
On April 4, 1973, a commercial pilot was conducting ski lift and transport operations near Gstaad, Switzerland, using an Agusta Bell 206 B, registration HB-XCF. After successfully transporting a group of skiers to a ridge north of Staldenhorns, the pilot attempted a second flight to deliver another group to the Obere Stalde area, approximately 200 meters below the previous landing site.
The pilot initiated a direct approach toward the valley, flying parallel to the slope with a tailwind. As the aircraft approached a small, flat area on a steep snow slope, the pilot encountered a strong gust from the rear left that pushed the helicopter toward the mountain. In an attempt to correct the drift by pulling the aircraft to the left, a second gust from above struck the helicopter. This caused the main rotor to strike the steep slope, resulting in the rotor blades breaking off below the rotor head. The fuselage dropped approximately half a meter into the snow, coming to rest on its belly.
The investigation
The investigation examined the pilot's credentials, the aircraft's mechanical state, and the environmental conditions at the time of the accident. The pilot was a professional with 1,946 total flight hours, including 86 hours on this specific model, and held valid mountain landing qualifications. No health issues were identified. The Agusta Bell 206 B was found to be airworthy, with weight and balance within limits, and no pre-existing mechanical defects were noted.
Weather conditions were sunny with 3/8 cloud cover and visibility exceeding 10 km. However, light to moderate turbulence was present near the slope due to the terrain, and recent heavy snowfall had left 10–30 cm of loose new snow on the ground. The landing site was an authorized mountain landing area but lacked permanent facilities or markings, and the fresh snow provided no visual reference points like ski tracks.
Findings
While the decision to approach with a tailwind was appropriate for the terrain, the investigation established that the landing was made difficult by the lack of visual references on the unmarked, snow-covered slope. It is unlikely that turbulence alone caused the collision. Instead, the investigation concluded that the pilot likely drifted toward the right while attempting to stabilize the aircraft due to a lack of visual cues. This movement disturbed the fresh snow, further reducing visibility and leading to the main rotor striking the steep slope.