Background
The helicopter involved was an Airbus Helicopters AS 350 B3, registered as HB-ZCM, owned and operated by Heli Rezia AG of Ambrì. The pilot, a Swiss national born in 1963, held a Commercial Pilot Licence (Helicopter) issued by the Federal Office of Civil Aviation. He had accumulated 7,197 total flight hours, of which 2,571 hours were on the accident type. On 3 December 2018, the pilot was conducting commercial external load flights from the base at San Vittore. The day's program comprised seven missions with a total of 37 rotations, all involving underslung loads.
Flight Sequence
At 14:00, the pilot and flight helper A resumed the final mission. They departed San Vittore at 14:18 and flew toward a pickup site near the village of Claro. The pilot was aware of a high-voltage transmission line in the area, having previously transported paint and material to one of its masts. The pickup site was located 170 m south of the usual landing spot. After landing at 14:23, the crew prepared a 40 m long sling and the load. The pilot then flew solo with the load to a drop-off point, returned, and picked up flight helper A.
At 14:35, the pilot and flight helper A departed Claro for the return flight to San Vittore. The helicopter lifted vertically, turned 270° left, and accelerated in a southeasterly climbing direction. The pilot made blind position reports on the Lodrino airfield frequency.
Collision
The flight helper kept the high-voltage line in sight. He observed that a collision with the earth wire was unavoidable and shouted a warning. At 14:36, the helicopter struck the earth wire at an orange marker ball. The wire broke, the helicopter decelerated sharply, and became difficult to control. It entered a descent, turned 180° left, and landed on a meadow 22 seconds after the collision, with a forward speed of about 40 km/h.
The pilot and flight helper sustained minor injuries. The helicopter was severely damaged. The earth wire was torn, causing short circuits on adjacent power lines.