NTSB Identification: ANC92IA001.
The docket is stored on NTSB microfiche number 46912.
Scheduled 14 CFR
Incident occurred Wednesday, October 02, 1991 in FAIRBANKS, AK
Probable Cause Approval Date: 05/05/1993
Aircraft: PIPER PA-31-350, registration: N200AK
Injuries: 5 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
DURING CRUISE FLIGHT, THE LEFT ENGINE LOST POWER AND OIL PRESSURE. AN ENGINE TEARDOWN ANALYSIS SHOWED THAT THE CRANKSHAFT COUNTERWEIGHTS HAD TWO INCORRECT OF THE FOUR INSTALLED ROLLERS. ALL FOUR ROLLERS WERE PART NO. 73648. ACCORDING TO TEXTRON LYCOMING, THE CORRECT ROLLER CONFIGURATION SHOULD HAVE BEEN 'TWO PART NO. 73648 5.1 ORDER AND TWO PART NO. 76788 6.3 ORDER ROLLERS.' AS CONFIGURED, THE ENGINE WOULD EXPERIENCE UNACCEPTABLE 6TH ORDER TORSIONAL VIBRATIONS.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: INCORRECT INSTALLATION OF CRANKSHAFT COUNTERWWEIGHT ROLLERS BY THE MANUFACTURER DURING REMANUFACTURE OF THE ENGINE. FACTOR WAS THE INADEQUATE SURVEILLANCE OF THE ENGINE ASSEMBLY PROCESS BY THE MANUFACTURER.
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