What happened
On July 1, 2013, an Eurocopter AS350 B3e, registration HB-ZMO, was performing a commercial transport mission in the Swiss Alps. The flight, part of an ongoing project to support renovations at the Kröntenhütte, involved transporting personnel and materials. After picking up a technician at the Leutschachhütte, the pilot intended to drop off a flight assistant at the Kröntenhütte.
During the flight, the pilot entered a valley south of the Kröntenhütte. Witnesses on the ground observed the helicopter flying at a very high speed in a descending path. As the aircraft progressed, it began a significant right-hand turn, following the terrain of a descending ridge. Shortly after the aircraft disappeared behind a ridge, smoke was seen rising from the area. The helicopter struck the terrain at high speed, triggering an intense post-impact fire that destroyed the aircraft and killed all four occupants.
The investigation
SUST investigators examined the wreckage, flight data from the navigation computer, and witness testimonies. The investigation confirmed that the aircraft's weight and balance were within limits and that there were no pre-existing mechanical failures or engine issues. The pilot was found to be in good health, and toxicology reports showed no presence of alcohol or drugs.
Investigators also analyzed the flight path, noting that the pilot had chosen a direct but high-risk route through the terrain. The investigation focused on the sudden loss of control during the high-speed turn near the ground.