What happened
On June 20, 2009, an Eurocopter AS 350 B2 helicopter, registration F-GTRF, was conducting sightseeing flights as part of an aerial event near the Walibi amusement park. During the ninth rotation of the day, the aircraft was carrying the pilot and six passengers.
At approximately 16:45 UTC, the helicopter departed for a flight toward Mont de Cordon. Witnesses on the ground observed the aircraft flying in a straight line before performing a U-turn with a steep nose-down attitude. The helicopter subsequently disappeared into the trees. The emergency beacon activated at 16:48 UTC, and the wreckage was located shortly after at the edge of a clearing below the mountain.
The accident resulted in one fatality (the pilot) and the destruction of the aircraft. All six passengers survived the impact.
The investigation
The BEA investigation focused on the aircraft's weight and balance, the engine performance, and the condition of the hydraulic systems. Investigators examined the aircraft's maintenance records, which showed the helicopter was being maintained according to standard procedures.
Data was recovered from a maintenance computer (Monit’air) which recorded engine parameters for the flight. The analysis of the engine's gas generator speed, torque, and rotor speed showed that during the final 30 seconds of the flight, the engine was operating at high power, with the gas generator speed reaching 102% of its maximum limit.
Additionally, the investigation included a technical examination of a Servo Command unit. Testing revealed significant non-conformities in the component, including incorrect metering slot dimensions and an unidentified hinge pin that did not meet approved manufacturing standards. However, when the unit was tested with different pins and plates, it operated satisfactorily, suggesting the primary performance issues were related to the internal spool geometry.
Findings
- The aircraft's takeoff mass was within the maximum authorized limit of 2,250 kg.
- The center of gravity was outside the certified flight envelope, as the distribution of passengers and fuel placed the aircraft in an unsafe configuration.
- The pilot's calculation of remaining fuel was inaccurate; while the pilot estimated 50% remaining, the actual amount was higher, though the weight distribution remained critical.
- The passenger weight on the front seat exceeded the company's maximum limit of 154 kg, with the actual weight reaching 160 kg.
- The engine was operating at maximum power limits during the final moments of the flight.