Accident to the Airbus AS350 registered HB-ZES on 14/02/2024 at Sierre [Investigation delegated to BEA by the authorities of Switzerland]
Collision with a high-voltage power line during an external sling load operation
As part of an aerial work mission, the pilot conducted a reconnaissance of the landing area, identified a high-voltage power line and then landed in the load pick-up area located below the power line. A task specialist attached the load with a 30-metre sling, while a second task specialist positioned himself at the load put-down area, higher up, at the same altitude as the high-voltage power line.
The pilot was experienced, this was a routine mission for him, and the presence of the high-voltage power line, easily identifiable on arrival, had not given him cause for concern.
As the wait on the ground continued, the pilot began to think about his next job and lost focus on the mission at hand.
Once he received the ‘green light’ from the second task specialist, the pilot took off immediately, without taking the time to conduct a departure briefing or consult a chart. He did not actively check for obstacles on his path and climbed directly to the load put-down point. The first task specialist, who remained on the ground, did not watch the entire take-off.
The flight path taken by the pilot brought the helicopter under the high-voltage power line. The second task specialist realised this and warned the pilot by radio. Upon receiving the message, the pilot attempted to stop the helicopter but was unable to avoid the collision. The damage caused by the collision with two cables made the helicopter difficult to control, and the pilot made an emergency landing, without releasing the load, on a wooded slope below the high-voltage line.
The pilot managed to land in the vegetation with a nose-up attitude, with the tail boom of the helicopter entering the vegetation first in the hope of absorbing the energy of the impact with the rear of the helicopter.
The helicopter was destroyed in the accident and the pilot, although injured, managed to evacuate the aircraft unaided. A fire broke out but quickly extinguished, probably due to the fuel system being unprimed when the helicopter tipped over onto its side.