NTSB Identification: LAX08LA230
14 CFR Part 133: Rotorcraft Ext. Load
Accident occurred Tuesday, July 15, 2008 in Rock Springs, WY
Probable Cause Approval Date: 12/20/2010
Aircraft: BELL UH-1H, registration: N3276T
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.
During an external load operation involving lifting a drill for repositioning, the pilot heard multiple loud reports (compressor stalls) coming from the rear of the helicopter, followed by an adverse yaw. The pilot jettisoned the drill and pointed the helicopter down a hill to avoid nearby ground personnel. The helicopter landed hard on its skids and then rolled onto its left side. During the engine examination investigators noted no movement of the power turbine during the visual examination and metal pieces were found in the exhaust. The compressor turbine leading edge blades and inlet guide vane trailing edges were damaged. Further examination of the engine revealed that the No. 1 bearing and associated hardware showed evidence of over-temperature exposure, but the exact cause for the over-temperature could not be determined. Pieces of bearing cage were found lying loose at the bottom of the reduction gearbox cavity and the ball bearings were grouped to one side and smeared over. While the manufacturer indicated that a bearing cage failure may have initiated the failure of the bearing, the investigation was unable to conclusively determine the cause of the bearing failure.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A total loss of engine power due to the failure of the No. 1 bearing for undetermined reasons. Full narrative available
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