What happened
On July 6, 2013, an Agusta AW 119 MK II helicopter, registration EC-LFL, was engaged in aerial firefighting operations near Quer, Guadalajara. The aircraft, operated by FAASA, was tasked with supporting ground firefighting brigades by transporting and dropping water using a helibucket.
After completing five successful water drops, the pilot attempted a sixth drop near a high-voltage power line. While flying at a speed between 40 and 50 knots, the aircraft's main rotor blades struck one of the electrical cables. The impact caused the cable to break and whip against the following rotor blade, resulting in significant structural damage to the rotor system. The pilot experienced intense vibrations and an "ENGINE OUT" warning on the instrument panel. Following established emergency procedures, the pilot performed a left turn and executed an emergency landing approximately 15 and 150 meters from the point of impact. The pilot exited the aircraft safely, and there were no fatalities.
The investigation
The CIAIAC investigation focused on the mechanical integrity of the aircraft and the sequence of the impact. Investigators examined the engine, finding no evidence of mechanical failure or anomalies that could explain the cockpit warnings. The investigation established that the vibrations reported by the pilot were consistent with the rotor imbalance caused by the impact and the loss of material from the blade.
Physical evidence from the aircraft showed that one rotor blade had a strike on the leading edge, while another had lost a section of its trailing edge measuring approximately 1 meter by 30 cm. The investigation also analyzed the electrical cable, finding clean, transverse cuts that indicated it had been severed by the rotor blades rather than failing due to an electrical arc.
Findings
- The primary cause of the accident was an error in distance estimation by the pilot while operating in close proximity to high-voltage power lines.
- The impact of the rotor blades with the cable caused the cable to strike the subsequent blade, leading to the loss of a portion of the trailing edge.
- The pilot's emergency response, including the use of autorotation techniques and the landing maneuver, was consistent with the aircraft's flight manual.
- Although the pilot did not release the helibucket before landing, the flat terrain prevented further damage during the stop.