Factual Information
On June 7, 2011, at approximately 9:35 local time, a Bell 407 helicopter, registration EC-IMZ, operated by INAER, was involved in an accident at Puerto de Angulo, in the municipality of Valle de Mena, Burgos, Spain. The helicopter was conducting aerial work for Red Eléctrica de España (REE), performing maintenance inspections of high-voltage power lines. The flight crew consisted of a pilot and a technician specialist.
Sequence of Events
The helicopter had been stationed at the La Jara substation near Güeñes, Biscay. The crew reported for duty at 8:30 and conducted a briefing, noting that weather conditions had improved compared to the previous day, though clouds and drizzle were present over nearby hills. They decided to proceed, coordinating with ground support to meet in Trespaderne if they did not return within 30 minutes.
At 9:03, the helicopter departed from La Jara, climbing to about 500 feet and proceeding at high speed to the starting point of the inspection task, approximately 11 km away. It then reduced altitude and speed to follow the power line, flying southwest through the Ayala valley toward Artziniega and then the Mena valley toward Puerto de Angulo. The flight covered about 24 km over 32 minutes, with altitude increasing to 650 m in the final minutes as it adapted to rising terrain.
Meteorological Conditions
The weather was characterized by cloudy skies and intermittent fog in a mountainous area. The crew had observed clouds and drizzle around the hills near La Jara and anticipated that the Puerto de Angulo pass might be obstructed.
Wreckage and Impact
The helicopter collided with terrain, striking a rocky wall in a controlled flight into terrain (CFIT) event. Both occupants died instantly. No other injuries or damage to property were reported.
Conclusion
The investigation determined that the probable cause was a collision with terrain in controlled flight due to low-altitude flight in adverse weather conditions that reduced visibility in mountainous terrain.