What happened
On 8 July 2006, a Sikorsky S-61N helicopter, registration EC-FJJ, was performing a flight near Roque Bermejo in the Canary Islands. During the flight, a structural failure occurred within the main rotor system. One of the main rotor blades, identified as the "black" blade, detached from the rotor head. This sudden loss of a rotor blade caused the helicopter to lose stability and impact the water. The accident resulted in fatalities among the occupants.
The investigation
The CIAIAC investigation focused on the structural integrity of the main rotor blades and the maintenance history of the aircraft. Investigators examined the wreckage and conducted a detailed study of the fracture area on the detached "black" blade. The investigation also reviewed the functionality of the Blade Inspection Method (BIM) system, which is designed to monitor internal pressure within the rotor blade spars to detect potential cracks. Furthermore, the investigators analyzed the maintenance records and the crew's compliance with established emergency procedures following any potential pressure warnings.
Findings
- The primary cause of the accident was the detachment of a main rotor blade from the rotor head.
- The fracture of the "black" blade was characterized by a fatigue-related failure.
- The investigation noted the existence of the Blade Inspection Method (BIM) system, which uses pressure indicators to warn of potential spar damage.
- The investigation considered the implications of the BIM/CBIM warning system and the procedures required when such indications occur.