Pilot Debrief

BELL UH-1H near Rock Springs, WY — 2008-07-15

Final reportLAX08LA230
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Date
2008-07-15
Location
Rock Springs, WY, USA
Aircraft
BELL UH-1H
Registration
N3276T
Category
Helicopter
Highest injury
Minor
Fatalities
0
Phase of flight
Hover

Probable cause

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

NTSB narrative

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.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted the lift when hearing loud pops and compressor stalls.

NTSB coding

Evidence available

  • Photos
  • 10 docket documents
View NTSB final reportView NTSB docket

Docket documents10

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