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Analysis

Summary

The investigation determined that an improper crankcase idler gear shaft bore repair resulted in increased vibration levels and excessive wearing of the accessory gears. These conditions led to various failures in the accessory drivetrain and the eventual failure of the engine. It was inappropriate to repair the crankcase idler gear shaft bore with a bush manufactured from a material with low resistance to plastic deformation, as the bush was subject to significant side loads.

It appeared that the personnel who operated the aircraft did not recognise that the problems they were experiencing were more than merely those of a worn engine. Had a 50-hourly oil filter inspection been carried out, as recommended by the manufacturer, it would have provided an opportunity for the problems in the accessory area to be identified prior to the engine failure.

 
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