What happened
On the morning of September 29, 2016, a Kaman K-1200 helicopter, registration HB-ZIH, was conducting a heli-logging operation near Fanas, Switzerland. The mission involved transporting timber using a 50-meter longline equipped with ten steel slings.
During the operation, a flight assistant requested an additional ten slings be delivered to the pickup site. As the pilot hovered over the clearing to deliver the load, the flight assistant instructed the pilot to release the slings downward. However, the pilot's view of the ground was obstructed by long shadows caused by the low morning sun and a nearby group of trees.
At that moment, a forester, who was preparing other loads and had momentarily forgotten the incoming delivery, moved toward the flight assistant. As the pilot released the slings from a height of approximately 3 to 4 meters, the heavy metal components struck the forester in the head and torso, throwing him to the ground. The injured worker was airlifted to a nearby hospital by a rescue helicopter.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the actions of the flight crew and ground personnel, as well as the environmental conditions at the time of the accident. The investigation reviewed statements from the pilot, the flight assistant, and the injured forester.
Investigators looked into the communication protocols between the aircrew and the ground team, the visibility conditions created by the morning sun, and the operational procedures regarding the release of loads. The investigation also noted that while the ground personnel were wearing appropriate protective gear, including helmets, the coordination between the external forestry staff and the flight crew lacked a detailed safety briefing for that specific day's tasks.
Findings
- The primary cause of the accident was the autonomous release of the steel slings by the pilot in an area where he did not have a complete view of the ground.
- Inadequate communication regarding the specific height of the release and the location of ground personnel contributed to the incident.
- Low sun angles and heavy shadows significantly hindered the pilot's ability to monitor the landing zone effectively.
- The flight assistant's instructions did not provide necessary height references, and the pilot proceeded to release the load without confirming the safety of the area beneath the slings.