NTSB Identification: LAX91FA052.
The docket is stored on NTSB microfiche number 45533.
Accident occurred Sunday, December 09, 1990 in PERRIS VALLEY, CA
Probable Cause Approval Date: 08/06/1993
Aircraft: de Havilland DHC-6-100, registration: N121PM
Injuries: 1 Minor,20 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

AFTER LIFT-OFF, AT ABOUT 100 FT AGL AND 85 KTS, THE LEFT ENG DECELERATED AND THE AIRPLANE BEGAN TO YAW AND ROLL LEFT. THE PIC ABORTED THE TAKEOFF, TURNED LEFT AND LANDED ON A FLAT LEVEL FIELD. THE AIRPLANE STRUCK A FENCE, THEN TREES. EXAMINATION OF THE LEFT ENG REVEALED THE LOSS OF POWER WAS ATTRIBUTED TO A FATIGUE FRACTURE OF A COMPRESSOR TURBINE BLADE, WHICH LED TO SUBSEQUENT BLADE FRACTURES. THE RIGHT ENG WAS EXAMINED AND FOUND TO HAVE ADVANCE WEAR ON THE THROTTLE CAM ASSEMBLY OF THE POWER TURBINE GOVERNOR. IN A TEST CELL, ONLY APRX 28% OF TAKEOFF POWER COULD BE ACHIEVED. THE CAM LOBE WEAR HAD PROGRESSED OVER AN EXTENDED PERIOD OF TIME. THE RIGHT ENGINE PROP GOVERNOR WAS REPLACED 11/18/90, FOLLOWED BY A TEST RUN.

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

A LOSS OF POWER ON THE LEFT ENGINE DUE TO A FATIGUE FAILURE OF A COMPRESSOR TURBINE BLADE LEADING TO FURTHER COMPRESSOR BLADE DAMAGE; A WORN POWER TURBINE GOVERNOR THROTTLE CAM ASSEMBLY WHICH LED TO LOSS OF POWER ON THE RIGHT ENGINE; AND INADEQUATE MAINTENANCE AND INSPECTION BY THE OPERATOR.

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