What happened
On September 19, 2017, a Kaman K-1200 helicopter, registration HB-ZIH, was performing timber extraction operations in the Faura d’Anzano region of Blenio, Switzerland. The mission involved transporting bark beetle-infested logs from a collection site to an unloading area located approximately 100 meters uphill.
During the penultimate rotation of the day, a ground crew member was preparing a combined load consisting of four logs. As the helicopter transitioned into forward flight to lift the load, a piece of one of the logs, weighing approximately 300 kg, detached from the main mass at an altitude of about 3 meters above the ground. The falling timber struck the ground crew member in the head and upper body, causing serious injuries. The individual was subsequently evacuated by a REGA rescue helicopter to a hospital.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the circumstances of the accident, reviewing statements from the pilot and the ground crew members. The investigation focused on the operational environment, the technical state of the aircraft, and the safety protocols in place during the logging process.
Investigators noted that the terrain at the loading site was extremely challenging, characterized by steep slopes, rocky outcrops, and dense brambles, which made movement difficult. The investigation also looked at the logistics of the operation, noting that the unloading site was positioned uphill from the loading site, which increased the danger zone for the ground crew during the lift.
Findings
- The primary cause of the accident was that the ground crew member maintained an insufficient safety distance and misjudged the distance between himself and the external load.
- In an effort to optimize efficiency, the crew member had attached multiple logs into a single load, which expanded the hazard area and restricted his available escape routes.
- The ground crew member issued the radio command to lift the load while he was still positioned within the danger zone.
- The uphill positioning of the unloading site was identified as a contributing safety risk, as it increased the potential hazard area for the ground crew during the extraction process.
- There were no evidence of technical malfunctions with the K-1200 or pre-existing mechanical issues with the load-securing equipment.