Incident
During flight, the pilot and passenger heard a bang, which was later determined to be the tail rotor driveshaft failing. The scraping sound inside the tail rotor driveshaft cowling indicated the failure. This resulted in a loss of tail rotor authority. The lack of damage to the tail rotor blades suggested they were nearly stationary at ground impact.
Examination
Manufacturer examination revealed that the driveshaft tube fractured due to fatigue cracking. The fatigue cracks were associated with an area of corrosion pitting on the outside surface of the tube, located adjacent to the second hanger bearing.
Pilot's Actions
After hearing the bang, the pilot slowed the helicopter to make an approach to land and investigate the cause. This caused the helicopter to begin yawing to the right. The pilot then realized they had lost tail rotor authority. They rolled off the throttle to stop the yaw, and as rotor rpm dropped, they were committed to an immediate landing.