NTSB Identification: NYC06LA175.
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Accident occurred Saturday, July 15, 2006 in Danville, WV
Probable Cause Approval Date: 04/30/2008
Aircraft: Enstrom 280C, registration: N5691B
Injuries: 1 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
Approximately 7 minutes after takeoff, the pilot of the helicopter heard a "loud snap," and experienced a 5 to 10 degree right yaw. This occurred a second time, 5 to 8 seconds later. The pilot declared an emergency and elected to make a precautionary landing. During the approach, he experienced a third snap sound and yaw movement. The helicopter was at an airspeed below 20 knots, and about 8 to 10 feet above the ground, when the pilot heard a bang, and felt ground contact. The helicopter rolled to the left, and the main rotor blades contacted the ground. Examination of the helicopter confirmed drive train continuity to the main and tail rotor drive shafts. A ground scar, consistent with tail rotor ground contact, was observed about 60 feet from the main wreckage. The tail rotor gear box, drive shaft and blade assembly were located about 250 feet from the main wreckage. Examination of the tail rotor gearbox and adjacent components did not reveal any preexisting damage; however, it also did not reveal any indications of rotational damage. Examination of the override clutch assembly, which drove both the main transmission and the tail rotor system, revealed preexisting damage that occurred at an undeterminable time prior to the accident. The accident helicopter was involved in a previous hard landing accident about 13 months, and 87 hours of operation prior, during which, it had a tail rotor strike, and a fractured tail rotor drive shaft. The override clutch assembly was not removed for inspection after that accident; nor was it specifically required to be removed and inspected per the manufacturer's maintenance guidelines for "Special Inspection for Sudden Stoppage, Main and/or Tail Rotor Blade Strikes."
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A partial failure of the override clutch assembly. A contributing factor to the accident was the manufacturer's inadequate inspection procedures of the override clutch assembly following a tail rotor strike. Full narrative available
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