What happened
On 23 February 2008, a SIKORSKY S-61N helicopter, registration EC-FVO, operating as part of a search and rescue mission, was engaged in recovering a crewmember who had fallen overboard from a Civil Guard patrol boat near Playa de San Jorge, Spain. The helicopter crew had located the individual in the water and initiated a rescue using the aircraft's external hoist.
As the rescue swimmer had secured the victim to the cable and signaled the pilot to begin the lift, a sudden, high-intensity wave struck both men while they were still in the water. This impact caused the hoist cable to snap. While the rescue swimmer was eventually able to reach the shore and be recovered by the helicopter, the victim was lost to the sea. The individual's body was recovered the following morning.
The investigation
The investigation focused on the mechanical failure of the Goodrich Actuation Systems hoist cable and the operational conditions during the maneuver. Investigators examined the aircraft's maintenance records, the physical condition of the hoist, and the broken cable fragments.
Analysis of the cable's fracture pattern revealed a ductile failure caused by static overload. Metallographic and chemical studies confirmed the cable met all manufacturer specifications and showed no signs of fatigue or corrosion. Furthermore, inspections of the hoist itself confirmed it was in good working order and properly maintained. Investigators also reviewed FLIR camera footage of the incident, which corroborated the sudden appearance of heavy swells during the lifting phase.
Findings
- The primary cause of the cable failure was a static overload occurring when the cable was subjected to extreme tension and a strong compressive force perpendicular to its length.
- The sudden arrival of high-intensity waves during the lifting maneuver forced the hoist to operate outside its designed parameters, specifically exceeding the maximum allowable operating angle of 20 degrees from the vertical.
- The cable broke at the cable entry guide of the hoist, where evidence of friction and compression from over-tensioning was identified.
- The aircraft, hoist, and cable were all properly maintained and met all regulatory and manufacturer requirements at the time of the accident.