NTSB Identification: LAX90LA171.
The docket is stored on NTSB microfiche number 43631.
Accident occurred Thursday, May 10, 1990 in FIREBAUGH, CA
Probable Cause Approval Date: 11/23/1992
Aircraft: HUGHES 369E, registration: N5217N
Injuries: 1 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.

THE HELICOPTER LOST ENG POWER AND LANDED HARD. THE PLT REPORTED HE HAD JUST COMPLETED RELEASING AN EXTERNAL LOAD. THE HELICOPTER WAS ABOUT 125 FEET AGL IN A CLIMBING LEFT TURN WHEN THE PLT HEARD A LOUD BANG. THE PLT ENTERED AUTOROTATION. THE PLT NOTED THAT THE MAIN ROTOR RPM WAS LOW AND WAS UNABLE TO REGAIN ANY MAIN ROTOR RPM BEFORE THE LANDING FLAIR. AT TOUCHDOWN, THE MAIN ROTOR BLADES FLEXED DOWNWARD AND SEVERED THE TAILBOOM. THE THIRD STAGE COMPRESSOR HAD FAILED, DAMAGING THE REMAINING STAGES OF THE COMPRESSOR. THE COMPRESSOR CASE PLASTIC WAS ERODED. THE ENG HAD UNDERGONE MAJOR MAINTENANCE AT 1,774.5 HOURS WHICH REQUIRED THE REMOVAL OF THE TURBINE SECTION. THERE WAS NO EVIDENCE IN THE ENG LOGBOOKS OF THE COMPRESSOR SECTION BEING INSPECTED AT 1,750 HOURS AS REQUIRED BY THE MANUFACTURER. THE ENGINE MAINTENANCE MANUAL WARNS EROSION WILL CAUSE DAMAGE TO COMPRESSOR BLADES AND VANES.

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

FAILURE BY COMPANY MAINTENANCE TO PERFORM A MANDATORY COMPRESSOR SECTION INSPECTION THAT RESULTED IN THE UNDETECTED EROSION OF THE COMPRESSOR VANES AND ENGINE FAILURE. CONTRIBUTING TO THE ACCIDENT WAS THE FAILURE OF THE PILOT TO MAINTAIN ADEQUATE MAIN ROTOR RPM AT CRITICAL ALTITUDE.

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