What happened
On February 17, 2011, an Eurocopter AS 350 B2, registration HB-ZHI, was performing a commercial VFR flight to transport passengers to the Glacier de Tsanfleuron in the Swiss Alps. The flight, operated by Heliswiss, involved transporting a mountain guide, a ski instructor, and several guests.
As the helicopter approached the landing site near the Glacier 3000 ski area, the pilot encountered challenging meteorological conditions, including patches of fog and low visibility. During the landing attempt, the pilot attempted to hover near a slope marker to maintain visual references. However, the passengers and the mountain guide began to intervene verbally, expressing concern about the proximity of nearby rocks and urging the pilot to abort the landing. Distracted and irritated by these intense communications, the pilot decided to execute a go-around. During this maneuver, the helicopter lost necessary visual references and collided with the rising terrain, causing the aircraft to overturn. The impact resulted in four serious injuries and two light injuries among the occupants, while the aircraft was destroyed.
The investigation
SUST examined the flight sequence, the meteorological conditions, and the operational oversight of the operator. The investigation established that the pilot had calculated the aircraft's weight to be within the limits for a hover out of ground effect (HOGE) at the altitude of the glacier, but the actual visibility was significantly compromised by fog. Investigators also looked into the level of supervision provided by the helicopter operator to the pilot during this specific seasonal deployment.
Findings
- The primary cause of the accident was the collision with the terrain due to the lack of necessary visual references during a go-around.
- The pilot's decision to attempt an approach under difficult weather conditions left very little margin for error.
- The pilot was distracted by the verbal interventions of the passengers, which led to a high-risk maneuver.
- The operator provided insufficient oversight and supervision for the pilot during the operation.
- The landing site, located within an active ski area, was neither marked nor separated from the ski slopes, presenting a latent risk to third parties.