Accident Overview
A helicopter engaged in long-line operations using a 50-foot long-line in support of a Christmas tree harvest experienced an in-flight failure. The pilot reported that while hovering into the wind over the drop-off point, a loud noise emanated from the rear of the helicopter. The helicopter instantly began to rotate around its vertical axis. Shortly after jettisoning the load, the helicopter impacted terrain.
Post-Accident Examination
Examination of the wreckage revealed that the tail rotor blades and tail rotor gearbox had separated from the helicopter's tail assembly. The tail rotor gearbox and one tail rotor blade were later located in a ditch near the accident site. The second tail rotor blade was found underneath a conifer tree approximately 100 feet east of the wreckage.
Tail Rotor Blade Failure
Inspection of the fractured tail rotor blade determined that the blade failed due to fatigue. The fatigue crack originated from multiple points on the inside surface of the skin near the outboard end of the butt block, approximately 7.6 inches from the inboard end and 1.38–1.6 inches from the leading edge. Several origins were located in pitted areas measuring no deeper than 0.00033 inches.
Component History
According to logbook records, the tail rotor blade had accumulated approximately 1,723 hours since new. The life limit for the tail rotor blade is 2,500 hours.