Incident Summary
During cruise flight, one of the tail rotor blades separated from the helicopter. The pilots reported hearing a 'loud bang,' after which the helicopter 'immediately and violently tucked down and left then rolled inverted and [was] spinning to the right.' The flying pilot righted the helicopter, and the non-flying pilot inflated the emergency floats prior to impacting the ocean.
Examination Findings
The outboard section of one of the tail rotor blades was recovered and examined. Investigators found that a fatigue crack had initiated in the spar in an 'area of round-bottomed corrosion pits 0.001 inch deep.' The two tail rotor blades installed on the helicopter had accumulated 4,644 and 4,913 hours, respectively. The tail rotor blades are life limited at 5,000 hours.