2008 AS350 B3 Logging Accident in Klosters-Serneus (HB-ZDE)

Incident Overview and Aircraft Details On May 30, 2008, at 08:48 local time, a Eurocopter AS350 B3 helicopter, registered as HB-ZDE, was involved in an accident during a commercial logging operation in Monbiel-Bündelti, within the municipality of Klosters-Serneus in the Swiss canton of Graubünden. The aircraft, manufactured in 2001, was owned by Rhein-Helikopter AG and operated by Air Grischa Helikopter AG. The helicopter was in a hovering flight phase at an altitude of 1,250 meters above sea level. ## Operational Context and Sequence of Events The pilot, a Swiss national born in 1973, was conducting a commercial VFR flight to transport logs from a steep, densely wooded area to a central unloading site. Due to the terrain and high trees, a 50-meter longline was used. During the 29th rotation, a ground handler attached the load to the sling. A forest ranger, positioned outside the designated danger zone, observed that the load initially failed to lift because a branch was jammed. The handler removed the jammed branch. At that moment, a falling branch from a treetop struck the handler on the head. The handler fell forward, hitting his head on a log, and remained unconscious. The forest ranger alerted a second handler, who informed the pilot and released the load. The pilot flew the helicopter to the unloading site, and REGA air ambulance arrived within ten minutes to transport the injured handler to Kantonsspital Chur. ## Meteorological and Technical Factors Weather conditions at the time included light rain, visibility of about 20 km, a southeast wind of 5 kt with gusts to 8 kt, and a temperature of 13 °C. The investigation found no technical problems that could have influenced the accident. The helicopter's weight and center of gravity were within limits, and the pilot held valid licenses. All ground handlers were equipped with protective helmets with integrated radios and protective clothing. ## Findings and Probable Cause The ground handler sustained a vertical skull fracture and concussion. The investigation concluded that the accident was caused by a falling branch, which was most likely dislodged by the helicopter's rotor downwash. The report emphasized that the purpose of the investigation was accident prevention, not the determination of fault or liability.