NTSB Identification: ERA12LA368
14 CFR Part 91: General Aviation
Accident occurred Thursday, May 24, 2012 in Piney Flats, TN
Aircraft: SCHWEIZER 269C, registration: N760DA
Injuries: 2 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On May 24, 2012, at approximately 1830 eastern daylight time, a Schweizer 269C, N760DA, was substantially damaged during a hard landing, after a loss of tail rotor effectiveness, in Piney Flats, Tennessee. The certificated commercial pilot and his pilot rated passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight operated under Title 14 Code of Federal Regulations Part 91.

According to the pilot, the flight originated at his farm in Piney Flats, Tennessee. After the departure on the local sightseeing flight with his friend they did a visual approach and landing, at Elizabethton Municipal Airport (0A9), Elizabethton, Tennessee, then took off and returned to his farm for landing. While on a short final approach for landing he heard a "high pitched whine", and the tail rotor authority degraded. He immediately initiated a full auto-rotation to landing.

During the landing the helicopter touched down on an uneven grass surface. The struts and main landing gear collapsed, and the tailskid assembly and vertical tail struck the ground. Prior to the event, the pilot did not see any warning lights or note any abnormalities.

Examination of the wreckage revealed that the helicopter was substantially damaged. The landing gear skid and strut assemblies were bent and broken, the forward and aft beam assemblies were bent, the fuselage struts and frames were bent and broken, the forward cabin floor was buckled, the cross beam was bent, the vertical stabilizer was bent and crushed, and the tail skid was bent.

Examination of the flight control system revealed no evidence of any preaccident anomalies or failures. Control continuity existed from the cyclic pitch control and the collective pitch control to the swash plate assembly and main rotor pitch links and from the tail rotor pedals to the tail rotor blade pitch links.

Examination of the drive train revealed however, that the tail rotor driveshaft had become uncoupled from the drive assembly and main rotor belt transmission, and the tail rotor drive shaft could be rotated freely by hand in both a clockwise and counterclockwise direction. Further examination also revealed that the main transmission input (pinion) shaft aft nut, was missing, along with its cotter pin.

Examination of the tail rotor drive shaft end fitting revealed that after coming off of the main transmission input shaft both the main transmission input shaft aft nut, and the cotter pin had been captured in the grease that was contained in the tail rotor drive shaft end fitting grease cavity.

Examination of the main transmission input shaft aft nut revealed that it was intact but exhibited wear on the lands and grooves of the threads.

Examination of the cotter pin revealed that it had fragmented into multiple pieces.

Examination of the main transmission input shaft, and splined drive sleeve revealed the existence of fretting wear, stepping on the faces of the splines, and steel gray colored particulate which when applied to a magnet would adhere to its surface.

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