Introduction
On 21 March 2012, a Eurocopter AS 350 B3 "Ecureuil", registration HB-ZKK, operated by Heli-Linth AG, was involved in an accident at Claridenfirn, north of the Claridenpass, Switzerland. The flight was a commercial heli-skiing operation.
Flight History
The pilot, a Swiss citizen born in 1979, held a commercial pilot license for helicopters (CPL(H)) issued on 27 October 2011. He had a total flight experience of 240 hours and 32 minutes, with 110 hours and 51 minutes on the accident type. The flight departed Mollis at 09:55 LT and landed at Tierfed to pick up a mountain guide and four passengers. At 10:07 LT, the helicopter departed Tierfed towards the planned landing site on Claridenfirn.
Sequence of Events
During the first approach, the pilot decided to drop a marker sack from a hover of about 1.5 meters above the landing spot to aid visual reference. After dropping the sack, the pilot initiated a second approach. During this approach, a fog bank obscured the rock face used as background reference. The pilot decided to execute a go-around, turning right and asking the guide to report height above ground. The guide warned that the helicopter was close to the snow surface. Shortly afterward, the right skid contacted the snow, causing the helicopter to roll onto its side. This led to the rotor blades striking the snow, severing the tail boom. The cabin came to rest nose-down in soft snow. The guide estimated the snow depth at about 60 cm of powdery, wind-pressed fresh snow.
Injuries and Damage
The helicopter was destroyed. Among the six occupants, four passengers suffered slight injuries. The pilot and one other occupant were uninjured.
Probable Cause
The accident was caused by a collision with the snow surface following a go-around in diffuse light conditions. Contributing factors: delayed decision to abort approach in deteriorating weather and diffuse light, and the pilot's limited experience in mountain operations.