Bell UH-1H N3276T accident near Rock Springs, Wyoming

Probable cause

A total loss of engine power due to the failure of the No. 1 bearing for undetermined reasons.

NTSB analysis

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.

Text from the NTSB. Open the NTSB docket for LAX08LA230 for the full record.