What happened
On April 25, 2005, an Eurocopter AS350 B2 helicopter, registration F-GFAQ, operated by Héli Sécurité, was performing external load operations near Tende, France. After completing a mission to deliver personnel and equipment to a dam site at an altitude of over 2,000 meters, the pilot began the return flight to the base camp. During this return leg, near Lake La Minière, the aircraft's 10-meter sling made contact with the tail rotor assembly. Witnesses observed the helicopter spinning on its yaw axis before disappearing from view. The aircraft subsequently struck a tree and caught fire, resulting in one fatality (the pilot).
The investigation
The investigation focused on the wreckage and the flight dynamics of the final moments. Investigators found that the main rotor blades had struck a larch tree, severing it. The wreckage analysis revealed that the tail rotor blade had been lost due to an imbalance caused by the sling striking the rotor. This impact caused the tail rotor drive shaft and the vertical stabilizer to detach from the airframe. Evidence from the cockpit door, which was torn outward by centrifugal force, indicated that the engine was delivering high power at the moment of impact. The investigation also reviewed the operator's procedures and the pilot's recent experience with sling operations in mountainous terrain.
Findings
Several contributing factors led to the accident:
- The use of a 10-meter sling, which exceeded the recommended length for this type of operation.
- The absence of a weight (sinker) at the bottom of the sling to stabilize it.
- An excessive or inappropriate flight speed during the return leg.
- A sudden pitch maneuver that likely caused the sling to swing into the rotor path.
- A potential lapse in situational awareness by the pilot following the successful completion of the primary mission tasks.