What happened
During cruise flight, a helicopter experienced an in-flight breakup. Witnesses observing the aircraft from the ground reported seeing various components separate from the helicopter while it was in flight. One witness observed that a portion of the tail rotor separated first; as the aircraft pitched to the right, the main rotor subsequently detached. This caused the main fuselage to spin and descend vertically toward the ground.
Another witness reported hearing an audible "pop" followed by observing the main rotor slowing, wobbling, and eventually stopping its rotation before breaking away from the aircraft and traveling forward of the fuselage. The witness further noted that the helicopter pitched nose-forward and fell almost vertically.
The investigation
The wreckage was recovered in several pieces. The main rotor assembly was located approximately 450 feet east of the primary wreckage site, while the tail rotor components were found with the main fuselage wreckage.
A metallurgical examination was performed on the left cluster fitting lugs (P/N 269A2234), which attach to the left tail boom strut. This examination revealed that these components failed due to fatigue.