Background
The aircraft involved was an SA 315B Lama, registration HB-XGE, operated by Air Zermatt SA of Zermatt. The pilot, a Swiss national born in 1956, held a professional pilot license and had accumulated 917 total flight hours, including 167 on type. The accident occurred at the landing site "Unteres Aeschjoch" on the upper part of the Rothorn glacier, at an elevation of 3560 meters. The time was 1125 local time (UTC+2). The flight was a commercial ski transport operation.
Flight Narrative
At 1030, the pilot departed Zermatt with two passengers and a mountain guide for the "Unteres Aeschjoch." Upon arrival, poor visibility prevented landing, and he returned to base. Shortly thereafter, a second group of skiers with guide Y arrived. The pilot flew some passengers to Testa Grigia (Monte Rosa) where conditions were better. On return, he saw the landing site in sunlight and informed his base. He then picked up guide Y and one client, departing at 1115 for the Aeschjoch. Visibility was acceptable but deteriorating. A wind indicator flag showed a south wind, so the pilot approached into the wind. Guide Y decided to remain on the ridge to relay weather by radio.
At 1119, the pilot took off again from Zermatt with three skiers from the first attempt. He contacted guide Y, who reported similar conditions with no wind. Approaching the glacier, the pilot saw guide Y in red clothing and his client. The pilot positioned the helicopter in a hover at about 1 meter above ground, using guide Y as a visual reference for landing. A tailwind gust suddenly pushed the helicopter forward. Guide Y, who was holding the left skid with his right hand and standing with his back to the helicopter to protect himself from blowing snow, moved sideways, disappearing from the pilot's view. The pilot lost forward visibility due to the snow cloud; he could not see the wind flag or the skier. Hesitating to land due to fear of a skidding landing that could tip the helicopter or injure the people nearby, he decided to move backward. During this maneuver, the helicopter ascended slightly and entered a fog patch, leading to spatial disorientation. The pilot lost control, and the helicopter struck the glacier with a pronounced lateral inclination approximately 80 meters from the intended landing point.
Injuries and Damage
The pilot and two passengers sustained serious injuries; one passenger was slightly injured or unharmed. The helicopter was destroyed.
Cause
The investigation determined that the accident was caused by loss of control due to loss of external visual references.