What was found
SIXTY-FIVE PERCENT POWER IN LEVEL FLIGHT, IFR CONDITIONS. CRANKSHAFT BROKE AT FIRST MAIN BEARING AFT NOSE BEARING THROUGH CHEEK. CRANKSHAFT TOTAL TIME, 2,301 HOURS. INSPECTED, MAGNAFLUXED, AND PERFORMED ULTRASONIC INSPECTION AT 1,485 HOURS. SUSPECT FATIGUE AND STRESS FAILURE. SUBMITTER STATED CRANKSHAFT DESIGN NOT ADEQUATE FOR 285 HORSEPOWER RATING. RECOMMEND NR IO520BB FOR THIS HORSEPOWER RATING. MAGNAFLUX AND ULTRASONIC PER SB M87-5 ARE NOT SUFFICIENT TO PREVENT NR IO520BA CRANKSHAFTS FROM BREAKING.