What happened
On May 19, 2015, a Hughes 369D helicopter, registration EC-LXF, operated by Helitrans Pyrinees, was conducting a positioning flight from Huércal-Overa to La Seu d’Urgell. While navigating the Valencia TMA, the pilot encountered intense storm cells. To avoid the weather, the pilot requested and received authorization to fly along the coastline at an altitude of 1000 ft or below.
While flying over the sea near El Saler, the occupants heard a loud metallic noise. The aircraft immediately began a violent leftward rotation while banking to the right. The centrifugal force generated by this rotation was so intense that the helicopter doors detached from the airframe. The pilot initiated an emergency autorotation procedure, successfully reducing the impact force upon hitting the water. The aircraft sank rapidly, but both occupants managed to exit the cabin under their own power.
The investigation
The CIAIAC investigation focused on the mechanical failure and the survival conditions of the occupants. Investigators examined the aircraft's maintenance history, which showed a recent inspection of the main rotor, and the meteorological conditions, which included a cold front and storm cells.
Because the wreckage could not be located on the seabed, investigators relied on the statements of the pilot and the passenger. The investigation also reviewed the regulatory requirements for life jackets and water survival training in Spain, noting a discrepancy between the regulations for airplanes and those for certain types of helicopter operations. The investigation confirmed that the occupants were rescued by a SASEMAR vessel approximately 69 minutes after the initial MAYDAY call.
Findings
- The most probable cause of the accident was an interruption of power transmission from the engine to the main transmission through the connecting shaft.
- The pilot chose to fly at a low altitude over the sea to avoid storms, a route that placed the aircraft beyond the horizontal distance achievable via autorotation to land.
- The aircraft was not equipped with life jackets, and the pilot had not undergone helicopter underwater escape training (HUET), although the passenger's recent HUET training significantly aided the rapid exit from the sinking aircraft.
- Regulatory gaps existed at the time, as Spanish Air Traffic Regulations mandated life jackets for certain airplanes but did not explicitly require them for the specific category of helicopter operation involved in this accident.
- Survival was aided by relatively high water temperatures (19°C) and low wave heights, which prevented immediate hypothermia.