WILLIAMSPORT, AK, USA
N1075G
BELL 206B3
THE HELICOPTER PILOT REPORTED A TOTAL LOSS OF POWER AND A SUBSEQUENT HARD AUTOROTATION LANDING. AN EXAMINATION OF THE ENGINE DISCLOSED A FRACTURED PC TUBE FROM THE COMPRESSOR TO THE PC FILTER. FAILURE OF THIS TUBE WILL CAUSE THE ENGINE TO LOSE POWER BELOW IDLE OR FLAME OUT. AN NTSB METALLURGIST WHO EXAMINED THE TUBE BELIEVES THAT THE TUBE FRACTURED DUE TO FRETTING AND FATIGUE, MOST LIKELY PRECIPITATED BY MISALIGNMENT OF THE PC TUBE DURING FIELD MAINTENANCE. ALLISON, THE ENGINE MANUFACTURER, HAS RECENTLY REDESIGNED THE TUBE WITH A THICKER WALL AND A DIFFERENT SHAPE TO FACILITATE MAINTENANCE PROCEDURES IN THE FIELD, AND TO MAKE THE TUBE MORE RESISTANT TO FATIGUE.
THE MANUFACTURER'S INADEQUATE PART DESIGN AND THE IMPROPER MAINTENANCE TECHNIQUES BY THE OPERATOR.
Source: NTSB Aviation Accident Database
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