What happened
On 25 April 2006, at approximately 13:45 local time, an Aerospatiale helicopter crashed in the vicinity of La Pobla de Segur, Spain. The aircraft was performing an aerial inspection of power lines when it struck the terrain, resulting in a fatal accident for all four occupants.
The aircraft was flying at low altitude, performing tasks related to the inspection of electrical infrastructure. During the flight, the aircraft experienced a sudden loss of power/control, leading to an impact with the ground. The subsequent fire destroyed much of the wreckage.
Findings
An investigation into the wreckage and the surrounding area revealed that the aircraft's transmission system had failed. Specifically, the freewheel mechanism, which is critical for the power transfer between the engine and the rotor, had become disconnected. This failure caused the main rotor to lose its drive, making controlled flight impossible at the low altitude required for the mission.
Further examination of the wreckage identified that the freewheel assembly had suffered a structural failure. The investigation focused on the condition of the components and the environmental factors present at the time of the accident.