What happened
On May 11, 2012, an Eurocopter AS 350 B3 operated by Heli Rezia SA was performing a commercial cargo operation in Camorino, Ticino. The mission involved transporting a swimming pool weighing approximately 800 kg from a sports field to a nearby location. To facilitate the transport, an 80-meter sling, composed of 20-meter and 60-meter sections joined by a 1.1 kg metal shackle, was utilized.
During the final phase of the operation, the pilot attempted to release the sling at the landing site. The pilot maneuvered the helicopter in a backward hover at an altitude of approximately 25 meters to minimize the risk of the tail rotor contacting the line. As the helicopter descended, the metal shackle was positioned roughly 5 meters above the ground. Without receiving a specific instruction from the ground crew, the pilot released the cargo hook. The falling metal shackle struck a flight assistant who was working nearby, resulting in serious injuries to the individual.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the sequence of events, the technical state of the HB-ZCM, and the communication protocols between the crew and the ground assistants. The investigation focused on the mechanics of the release and the coordination between the pilot and the two assistants present at the site. Investigators also reviewed the pilot's training records and the company's operational procedures regarding external cargo sling (ECS) operations.
Findings
- The primary cause of the accident was the release of the cargo hook without a command from the flight assistant, which caused the metal shackle to fall.
- Inappropriate sling release procedures contributed to the accident, as releasing the line from a significant height (25 meters) increased the risk to personnel in the danger zone.
- A critical lack of coordination and communication was identified, as there was no radio traffic between the pilot and the assistants during the crucial phase of the sling release.
- The pilot's backward flight maneuver significantly restricted visibility of the ground area.
- The injured assistant was not actively involved in the sling release process at that moment but was performing other tasks, placing them within the hazard zone.