NTSB Identification: IAD99LA015.
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Accident occurred Thursday, November 12, 1998 in LOUISVILLE, KY
Probable Cause Approval Date: 03/31/2000
Aircraft: Bell 206-B, registration: N32KY
Injuries: 1 Minor,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 reported that while in cruise at 700 feet AGL the helicopter yawed left, followed by a low rotor caution light being illuminated. The pilot executed an autorotation landing under dark night conditions to a flat, wet, muddy surface. During the landing the helicopter's skids began to dig in, and the helicopter began to nose over. The pilot applied aft cyclic in an effort to prevent the nose over during which the rotor blades impacted and severed the tailboom. Post-crash examination revealed 51 gallons of fuel aboard and no spreading deformation to the helicopter's skids. Further examination revealed that the 'B' nut on the PC air line from the power turbine governor to the fuel control unit was backed off about 2-3 'flats.' The engine was successfully operated in a test cell in an 'as received' condition. During subsequent engine runs, the 'B' nut was tightened and loosened to one flat with no variation in engine performance. The 'B' nut was also completely removed resulting in a stagnant start. According to the manufacturer, a breach in the PC air line will allow air pressure to bleed out and result in the fuel control unit automatically shifting to a minimum flow condition (less than idle). The test cell conditions may or may not have duplicated the vibratory conditions in the aircraft's airframe at the time of the power loss.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A loose 'B' nut on the aircraft's PC Air line which resulted in fuel starvation, and the pilot's abrupt application of aft cyclic to prevent a nose over. Contributing factors were soft terrain and dark night conditions. Full narrative available
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