What happened
On January 9, 2018, an Airbus Helicopters AS 350 B3, registration EC-JEA, was performing a commercial heli-skiing operation in the Vall de Ruda, within the Naut Aran municipality of Lleida. The flight, operated by Habock Aviation, involved transporting passengers and a mountain guide to high-altitude points for skiing.
During the final phase of the fourth flight of the day, the pilot attempted to land the aircraft in a clearing at the bottom of the valley. Unlike a previous landing in the same area, which had been performed with a wider approach, this approach was more direct and executed from a southerly heading. During the final moments of the landing, the main rotor blades struck the branches of a tree located behind and to the left of the aircraft.
The impact caused significant damage to the main rotor blades, including structural loss on one blade. The collision triggered intense vibrations throughout the airframe; however, the pilot was able to maintain control and complete the landing safely. The pilot and all passengers were uninjured and were later evacuated by emergency services.
The investigation
The CIAIAC investigation examined the flight tracks, the aircraft's performance, and the pilot's actions. Data from the flight tracking system revealed that the descent rate during the final stages of the accident flight was significantly higher than in the preceding successful landing. While the previous landing maintained a descent rate of approximately 486 ft/min, the accident flight saw a mean descent rate of 1,644 ft/min during the final 15 seconds.
The investigation also reviewed the operator's procedures. It was noted that while the operator's manual provided guidelines for heli-skiing, it lacked specific instructions regarding the minimum required dimensions for landing sites. The landing area used during the accident was found to be smaller than the 2D dimension (twice the aircraft's length) typically recommended for safe operations.
Findings
- The primary cause of the accident was the loss of visual references during the landing.
- The pilot likely focused excessively on the specific tree that was eventually struck, failing to utilize other visual cues to judge the aircraft's separation from the obstacle.
- The selection of a confined landing area with dimensions smaller than the operator's required minimums contributed to the event.
- The approach was characterized by a high rate of descent compared to previous successful maneuvers in the same area.