NTSB Identification: DEN99TA031.
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Accident occurred Monday, January 04, 1999 in WOODRUFF, UT
Probable Cause Approval Date: 04/25/2001
Aircraft: Hughes 369D, registration: N5013P
Injuries: 3 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.

As the helicopter was being maneuvered at low altitude, the pilot heard a series of compressor stalls, accompanied by a rapid decay of rotor rpm. The helicopter struck the ground, spun around and rolled over on its right side. The engine was functionally tested and was 20 horsepower below overhaul specifications. The compressor stalled repeatedly. Compressor disassembly disclosed case liner erosion, most noticeably at the 5th and 6th stages, and the rotating labyrinth seal was missing. After replacing the seal and installing a slave compressor module, the engine tested normal.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A partial loss of engine power due to erosion in the compressor assembly module. Factors were a missing rotating labyrinth seal, the installation of which had not been performed by unknown maintenance personnel.

Full narrative available

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