NTSB Identification: IAD97LA028.
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Accident occurred Wednesday, December 04, 1996 in MAYFIELD, KY
Probable Cause Approval Date: 03/31/1998
Aircraft: Hughes 269C, registration: N1105P
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot stated that the purpose of the flight was to ferry the helicopter. The helicopter had been cruising at 1,200 feet MSL for over an hour, when the nose started to yaw to the right. Unable to control the yaw, the pilot entered an autorotation at about 70 mph to a field. During the forced landing, the helicopter collided with a fence. Examination of the helicopter revealed that the aft pinion nut of the main transmission had disengaged, which allowed the tail rotor splined drive sleeve to disengage from the pinion and tail rotor drive shaft. Investigation did not determined why the aft pinion backed off. The last annual inspection was completed on 6/7/96. The helicopter had accumulated 66 hours of flight time, since the annual inspection.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

disengagement of the main transmission aft pinion nut, allowing the tail rotor splined drive sleeve to disengage from the pinion, which resulted in loss of directional control and an emergency (autorotative) landing.

Full narrative available

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