Port Orange, FL, USA
N9285
ENSTROM 280
The pilot was conducting a local flight when just prior to touchdown, the helicopter began to spin to the right and made an uncommanded climb and spin to the right. The pilot applied full left rudder pedal, but the helicopter continued to spin to the right. He lowered the collective and landed hard on the skids, which resulted in substantial damage to the fuselage. Postaccident examination of the helicopter revealed the tail rotor driveshaft was separated and free to spin inside the coupling. Metallurgical examination of the driveshaft revealed the bolt holes in the driveshaft were distorted, consistent with torsional shear-stress in the clockwise direction.
On August 21, 2021, about 1330 eastern daylight time, an Enstrom 280C, N9285, was substantially damaged when it was involved in an accident in Daytona Beach, Florida. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91personal flight. According to the pilot, he conducted a local flight around Spruce Creek Airport (7FL6), Daytona Beach, Florida, and was approaching to land. Just prior to touchdown, the helicopter made an uncommanded climb and started to spin to the right. The pilot applied full left pedal, but the helicopter continued to spin to the right. He lowered the collective and the helicopter landed hard on the skids. The left skid was damaged during, fuselage frame, and the tail rotor blades were damaged during the landing. Postaccident examination of the helicopter revealed that the tail rotor driveshaft was free to spin inside the coupling and not connected by a through bolt. The coupling and a section of the drive shaft were forwarded to the National Transportation Safety Board’s Material Laboratory for further examination. The examination revealed that the bolt holes in the drive shaft tube were mechanically distorted consistent with the presence of an axially applied torsional shear-stress in the drive shaft tube in the clockwise direction. Macroscopically, the fracture surface in the drive shaft tube was consistent with overstress due to torsionally applied shear stress (for more information, see Materials Laboratory Factual Report in the public docket for this investigation).
The failure of the tail rotor drive shaft at the coupling due to torsionally applied shear stress.
Source: NTSB Aviation Accident Database
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