NTSB Identification: FTW98LA084.
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Accident occurred Friday, January 02, 1998 in RIVIERA, TX
Probable Cause Approval Date: 02/16/2001
Aircraft: Hughes 269C, registration: N1091Y
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.
Following a total loss of engine power, during a cattle herding flight, the pilot executed an autorotation to an area confined by trees. Engine examination revealed a broken crankshaft & camshaft. The camshaft exhibited deformation consistent with overload. All four cylinder mounting flanges were fretted & all piston rings showed 'excessive' wear. The #1 & #4 cylinder top compression rings were broken. Main bearing saddle faces of the crankcase showed heavy fretting. The engine manufacturer Materials Laboratory reported the mode of fracture of the crankshaft was fatigue. The fatigue originated from the oil hole (between #3 main & #3 crankpin journals) in the cheek and near the rear fillet radius of the #3 main bearing journal. The cause of the fatigue was not determined. During the overhaul, the crankshaft received a magnaflux inspection & re-nitriding by an inspection facility. The engine was reassembled & returned to service by company maintenance personnel. The engine had 1150.6 hours since overhaul.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The total loss of engine power due to a fatigue failure of the crankshaft for undetermined reason. A factor was the lack of suitable terrain for the forced landing. Full narrative available
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