Forced/precautionary landing involving a Piper PA-28-181, VH-NOR, 2 km north-west of Mittagong (ALA), New South Wales, on 18 April 1998

The pilot advised Flight Service (FS) that the engine had failed, and he was attempting a landing at the Mittagong airstrip. The aircraft subsequently landed approximately 2 km short of the airstrip damaging the left-wing tip and landing gear during the rollout. The pilot advised FS of the situation and that there were nil injuries. The initial maintenance investigation discovered that the crankshaft accessory drive gear positioning dowel had sheared. This in turn had ceased the drive to all the engine accessories and the camshaft, resulting in the engine stopping. The initial reason for the failure of the dowel could not be positively determined. 

Subsequent to the initial investigation, a detailed failure analysis of the failed engine components was carried out. This examination revealed that a significant factor in the failure of the crankshaft gear/crankshaft attachment had been a manufacturing irregularity on the bearing surface of the head of the attaching bolt. The manufacturing irregularity resulted in a reduced clamping force, between the gear and the crankshaft, being established during assembly. The loss of the clamping force had allowed relative movement between the gear and the crankshaft mounted gear positioning dowel. This eventually led to the fatigue failure of the dowel and the loss of integrity of the accessory gear drive assembly.