What happened
On March 18, 2008, a Kaman K-1200 K-MAX helicopter, registration HB-ZGK, was performing timber extraction operations in the Eigental region of Switzerland. The mission, operated by Rotex Helicopter AG, involved transporting logs from a steep, forested mountainside to a landing site located approximately 400 meters away and 120 meters lower in elevation.
During the 66th rotation of the day, the pilot used a 50-meter longline to lift a load consisting of three tree trunks. As the load was being hoisted, a nearby dead tree was knocked over, either by contact with the lifting load or by the rotor downwash. The falling tree struck a forest worker who was acting as the ground crew member at the pickup site. The worker, who was performing dual roles as both a forester and a flight assistant, was severely injured by the impact.
The investigation
The investigation examined the operational conditions, the technical state of the aircraft, and the safety protocols in place at the time of the accident. Investigators reviewed the weather conditions, noting that recent snowfall had left the terrain slippery and the treetops covered in powder snow. The investigation also looked into the ground crew's positioning and the lack of a formal safety briefing prior to the start of the day's operations.
Findings
- The primary cause of the accident was a dead tree falling and striking the forest worker, who was mistakenly positioned within the danger zone.
- The decision to proceed with transport flights despite the challenging weather and slippery ground conditions contributed to the risk.
- The forest worker momentarily lost sight of the load because the rotor downwash had kicked up significant amounts of snow, causing him to turn his gaze away from the lifting operation.
- The worker moved downslope rather than crosswise or upslope, which placed him in a vulnerable position relative to the falling timber.
- There was no formal safety briefing conducted with the ground crew before the day's work began, as the team had performed similar tasks at the same location in previous weeks.
- The forest worker was operating alone at the pickup point, whereas the landing site required at least two people for safety.