FAIRBANKS, AK, USA
N200AK
PIPER PA-31-350
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.
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.
Source: NTSB Aviation Accident Database
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