NTSB Identification: ANC92GA155.
The docket is stored on NTSB microfiche number 52291.
Accident occurred Tuesday, August 25, 1992 in FAIRBANKS, AK
Probable Cause Approval Date: 08/26/1993
Aircraft: BELL 206B, registration: N83139
Injuries: 2 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 public aircraft accident report.

THE STATE OF ALASKA HELICOPTER EXPERIENCED A FUEL LEAK AND AN UNEVENTFUL PRECAUTIONARY LANDING. THE LEAKING FUEL LINE WAS REPLACED IN FIELD MAINTENANCE WITHOUT MANUFACTURER'S REQUIRED SECURING CLAMPS. A SECOND FUEL LEAK, PRECAUTIONARY LANDING AND FUEL LINE REPLACEMENT WAS EFFECTED, AGAIN WITHOUT CLAMPS. A THIRD FUEL LEAK AT THE SAME REPLACEMENT LINE WAS FOLLOWED BY A FIRE FOLLOWING A PRECUATIONARY LANDING. THE NTSB SUPERVISED MANUFACTURER'S ENGINE EXAMINATION REVEALED VIBRATION IN ROTATING COMPONENTS OF 15 TIMES THE ALLOWED LIMITS, AS WELL AS A FATIGUE CRACK IN THE HOT SECTION. THESE VIBRATIONS AND CRACKS WERE NOT DISCOVERED DURING ENGINE MAINTENANCE AND INSPECTIONS BY COMPANY CONTRACT MAINTENANCE PERSONNEL. THE METALLURGICAL EXAMINATION OF THE FUEL LINES IN EACH EVENT REVEALED FATIGUE PROPAGATION AND THE LACK OF CLAMP MARKS ON THE FUEL LINES FROM EVENTS 2 AND 3.

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

POOR MAINTENANCE AND INSPECTION PROCEDURES BY THE CONTRACT MAINTENANCE PERSONNEL, AS WELL AS IMPROPER MAINTENANCE AND INSTALLATION OF THE FUEL LINE BY THE CONTRACT MAINTENANCE PERSONNEL. FACTORS RELATING TO THE ACCIDENT WERE THE TURBOSHAFT ENGINE VIBRATIONS AND THE CRACKED FUEL LINE(S).

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