ROBINSON HELICOPTER COMPANY R44 II

Full Narrative

On February 11, 2024, about 1130 Alaska standard time, a Robinson Helicopter R44 II, N74868, was substantially damaged when it was involved in an accident near Glacier View, Alaska. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 business flight.
According to the pilot, while in cruise flight, with both aft doors removed, about 700 ft above an area of snow-covered glacial terrain, he heard a loud “boom” noise and felt a slight airframe vibration. The pilot stated that he subsequently lost tail rotor thrust, and he then performed an autorotation to an area of snow-covered, mountainous terrain.
A postaccident inspection, after the helicopter was recovered, revealed that the tail rotor driveshaft was fractured in between the forward and aft flex plates, which resulted in substantial damage to the tail rotor driveshaft system. See Figure 1

Figure 1. Fractured driveshaft assembly. (Photo courtesy of FAA)

A detailed NTSB examination of the helicopter and the fractured tail rotor driveshaft is pending.