KOKHANOK, AK, USA
N385EH
Bell 206B
THE PILOT EXPERIENCED A SPOOL DOWN ON THE TURBINE ENGINE. EXAMINATION OF THE ENGINE REVEALED THAT THE AIR COMPRESSOR SCROLL TO TEE TUBE ASSEMBLY COMPRESSOR END FITTING HAD BROKEN. METALLURGICAL EXAMINATION OF THE PART SHOWED THAT THERE WERE NO MATERIAL IRREGULARITIES, THAT THE TUBE BEND DEVELOPMENT AND LINEAR MEASUREMENTS VARIED FROM THE ENGINEERING DRAWINGS, AND THAT THE TUBE ASSEMBLY FAILED IN A FATIGUE MODE. THE ORIGIN WAS ON THE TUBE O.D. APPROXIMATELY 0.020 INCH BELOW THE 'B' END FLARE RADIUS.
THE FAILURE OF THE COMPRESSOR END OF THE AIR COMPRESSOR SCROLL TO TEE TUBE ASSEMBLY CAUSING THE ENGINE TO SPOOL DOWN. THE FORCED LANDING IN ENEVEN, UNPREPARED, AND LIGHTLY FORESTED TERRAIN WERE FACTORS.
Source: NTSB Aviation Accident Database
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