Accident Description
Just after liftoff, one propeller blade separated from the hub near the outboard end of the associated ferrule fitting. This separation induced a failure of the crankshaft. The pilot executed a forced landing, during which the aircraft overran the runway end and nosed over.
Metallurgical Analysis
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 that specified a hand grinding rework to remove sharp threads in the ferrule. This bulletin had been shown to produce prior fatigue fractures. In the area of the fatigue fracture, the first three threads of the ferrule were found with sharp edges.
Maintenance Records
Maintenance records did not show the total time on this propeller since major overhaul.