What happened
On June 25, 2022, an Airbus AS 350 B3 helicopter, registration HB-ZMC, was engaged in a specialized agricultural transport mission near Diemtigen, Switzerland. The task involved retrieving a deceased bovine from the Alp Bodeflue region for transport to a different location. The flight, operated by Swiss Helicopter AG, was part of a routine workload occurring alongside a base open day at Gsteigwiler.
During the operation, the pilot maneuvered the aircraft to a landing site near the 'Underi Heitere' alpine hut. While approaching the chosen landing area, the aircraft's tail rotor struck overhead cables. The impact caused the helicopter to lose stability, spinning clockwise around its vertical axis before striking the ground just a few meters from the landing spot. The collision immediately triggered a fire.
One flight assistant sustained light injuries and managed to exit the burning wreckage to rescue the pilot. The pilot was found unconscious with severe injuries. The aircraft was destroyed in the crash, and a fuel leak caused local ground contamination. The onboard emergency locator transmitter failed to activate upon impact.
The investigation
Investigators examined the aircraft's equipment and the surrounding environment. The HB-ZMC was equipped with a cable cutter system and an obstacle collision warning device. Digital navigation maps on the aircraft showed certain obstacles as red lines; however, while one set of cables was recorded in the official database with a height of 35 meters, a second parallel cable was not listed because its height was below the 25-meter threshold required for database entry.
Findings
- The primary cause of the accident was the tail rotor striking overhead cables during the final approach.
- The pilot selected a landing spot south of the alpine hut, despite a suggestion from a bystander to land in a different area where previous helicopter operations had successfully occurred.
- One of the two cables involved in the collision was not present in the official obstacle database because its height was below the 25-meter reporting threshold.
- The aircraft lacked a crash-resistant fuel system (CRFS), which contributed to the post-impact fire.