What happened
On Friday, August 31, 2012, an Eurocopter AS 350 B3, registration F-GPHE, was engaged in a specialized transport mission near the Migouélou power station in Arrens-Marsous, France. The crew, consisting of a pilot and a mechanic, was transporting two painters from a valley helipad to a steep slope near an electrical pylon to facilitate repainting work.
During the initial approach, the pilot attempted to land the aircraft at a pre-identified spot (Point A) located under the power lines. However, the mechanic determined that the slope was too steep to allow the passengers to disembark safely. In response, the pilot repositioned the aircraft a few meters to the right (Point B). As the pilot attempted to depart the site by reversing and performing a turn, the main rotor blades struck the electrical lines. The impact caused a loss of control, and the aircraft crashed into the mountainside. The collision resulted in two injuries (the pilot and mechanic) and the destruction of the helicopter.
The investigation
The investigation focused on the decision-making process during the landing and the discrepancy between the initial reconnaissance and the actual flight. It was established that a reconnaissance flight had been conducted the previous Friday by the pilot alone. During that reconnaissance, the pilot had deemed the initial landing spot (Point A) suitable, believing there was sufficient clearance for a subsequent sling-load operation. Notably, the mechanic was not present during this initial assessment.
On the day of the accident, the presence of different personnel on board—including two representatives from the painting company—led to a different evaluation of the landing site. The investigators also reviewed the operator's Particular Activities Manual (PAM), noting that while it addressed human factors, it lacked specific procedures for conducting reconnaissance in mountainous environments containing obstacles.
Findings
- The accident was caused by an inadequate assessment of the environment at the second landing site, which was selected through an improvised decision-making process.
- The pilot was forced to develop a new flight strategy in real-time after receiving unexpected feedback from the mechanic regarding the slope's gradient.
- The crew composition differed between the reconnaissance phase and the actual mission, leading to inconsistent judgments regarding the safety of the landing spot.
- The lack of specific company procedures for managing unexpected obstacles during mountain landings contributed to the error.