What was found
(AUS) ENGINE CRANKSHAFT FLANGE CRACKED AND LEAKING AROUND FACE. CRACK ORIGINATED AT DOWEL HOLE AND PROGRESSED APPROXIMATELY 75 PERCENT OF THE WAY AROUND THE FLANGE. INVESTIGATION FOUND THAT THE PROPELLER HAD BEEN MODIFIED BY THE FITMENT OF A STEEL INSERT IN THE MAIN BORE OF THE HUB. THE INSERT DID NOT HAVE THE REQUIRED INTERNAL CHAMFER FOR CORRECT MATING WITH THE PROPELLER FLANGE SO THAT WHEN THE PROPELLER BOLTS WERE TORQUED THE RESULTING BENDING LOADS CAUSED THE FLANGE TO CRACK. PERSONNEL /MAINTENANCE ERROR. UNAPPROVED PART.