POSTON, AZ, USA
N8275G
CESSNA 188B
JUST AFTER LIFTOFF ONE PROPELLER BLADE SEPARATED FROM THE HUB NEAR THE OUTBOARD END OF THE ASSOCIATED FERRULE FITTING WHICH INDUCED A FAILURE OF THE CRANCKSHAFT. THE PILOT MADE A FORCED LANDING, OVERRAN THE RUNWAY END AND NOSED OVER. METALLURGICAL ANALYSIS INDICATED THAT THE FAILURE WAS DUE TO A FATIGUE FRACTURE WITH MULTIPLE ORIGIN POINTS CAUSED BY A SCRATCH. THE ANALYSIS ALSO SUGGESTED THAT ALL BUT THE FIRST THREE FERRULE THREADS HAD BEEN REWORKED IN A POST MANUFACTURE HAND GRINDING PROCESS IN ACCORDANCE WITH A MCCAULEY SERVICE BULLETIN SPECIFYING A HAND GRINDING REWORK TO REMOVE SHARP THREADS IN THE FERRULE, WHICH HAD BEEN SHOWN TO PRODUCE PRIOR FATIGUE FRACTURES. IN THE AREA OF THE FATIGUEFRACTURE, THE FIRST THREE THREADS OF THE FERRULE WERE FOUND WITH SHARP EDGES. MAINTENANCE RECORDS DID NOT SHOW THE TOTALTIME ON THIS PROPELLER SINCE MAJOR OVERHAUL.
Source: NTSB Aviation Accident Database
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