What happened
On February 13, 2018, an Airbus Helicopters EC1SB T1, registration F-GOPG, was engaged in a mountain rescue mission in the Tarentaise Valley. After landing on a ski slope near Sainte-Foy-Tarentaise to evacuate an injured skier, the pilot prepared for departure.
Following the medical team's decision to transport the patient to a hospital, the pilot initiated the takeoff procedure. After transitioning into a hover, the pilot began accelerating in a level flight along the ski slope toward the valley. During this phase, the aircraft struck a 7mm diameter metallic cable used for the controlled triggering of avalanches (Catex system). The impact caused severe vibrations and significant structural damage to the rotor mast, the tail boom, and the fenestron. The pilot maintained control of the aircraft and performed an emergency landing in the snow nearby.
The investigation
The BEA examined the aircraft's damage, which included a broken and deformed control linkage for the main rotor blades, a severed upper tail fin, and damaged fenestron components. The investigation focused on the configuration of the Catex cable system, which consisted of a dual-strand loop supported by pylons.
The investigators found that one strand of the cable passed under the rotor disk and snapped upon contact with the rotor mast, while the second strand rubbed against the rotor blades and sliced the top of the tail fin. The investigation also reviewed the pilot's experience, the meteorological conditions, and the operational procedures used during the mission. It was noted that while the pilot had identified some obstacles during the initial approach, a specific section of the cable was not identified during the takeoff phase.
Findings
- The primary cause of the accident was the pilot's choice of an inappropriate takeoff profile and flight path, which led to the collision with the cable.
- The pilot did not perform a vertical takeoff to clear obstacles, opting instead for a level-flight acceleration along the slope.
- The pilot did not consult the available ski area maps or consult with the ski patrollers on-site to verify potential hazards before departing.
- The cable was difficult to detect due to its small diameter and the fact that the supporting pylons were obscured by the local terrain.
- Contributing factors included a potential decrease in vigilance due to fatigue, as the pilot was on the final day of a heavy ten-day work rotation, and the lack of active obstacle searching during the takeoff phase.
- Reduced visibility caused by powdery snow kicked up by the rotor wash and the use of a baseball cap visor, which may have limited the upward field of view, also played a role.