What happened
On September 14, 2006, a Eurocopter AS 350 B2, registration LN-ODH, was performing cargo operations near Voss, Norway. The aircraft, operated by Fonnafly AS, had been transporting concrete containers to a mountain site. During a scheduled break between cargo deliveries, the mission profile changed when a passenger transport task was moved forward in the schedule.
As the helicopter departed from the Tråstølen landing site for the passenger flight, a 9.6-meter steel cargo wire remained attached to the underside hook, though no load was attached. During a descending turn while leaving the mountain, the unsecured wire began to swing violently. The cable eventually struck the tail rotor, causing the tail fin and the tail rotor assembly to be torn from the airframe. The loss of the tail rotor rendered the aircraft completely uncontrollable, leading to a fatal impact with the ground. Both the pilot and the passenger were killed in the crash.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the aircraft, the site, and the operational sequence. Investigators found that the engine and rotor systems were functioning normally at the time of the impact and no mechanical failures were identified. The investigation also looked into the pilot's actions and the circumstances leading to the departure.
Findings
- The primary cause of the accident was the unsecured cargo wire swinging into the tail rotor.
- The pilot likely forgot the wire was still attached due to a combination of distractions, including managing a change in schedule, recent roadwork at the site, and the decision to pick up an additional passenger.
- The transition between different types of operations—from external sling loading to passenger transport—created a significant risk factor.
- The aircraft was otherwise in a safe condition for flight, with all weight and balance parameters within limits prior to the structural failure.