What happened
During the initial climb to altitude, the aircraft's right engine experienced an uncommanded shutdown. Following the loss of power, the crew declared an emergency and subsequently completed an uneventful single-engine landing at the departure airport.
The investigation
Post-incident inspections revealed metallic chips on the chip detector. Investigators found that the bearings within the accessory gear housing assembly (P/N 3103601-6) were missing all of their balls, with fragments of these ball bearings located in the bottom of the engine case. An examination of the bearing races showed evidence of pitting and scoring.
According to diagnostics provided by the operator, the disintegration of these bearings caused the gear shaft to drop and make contact with the gears of the accessory drive idler gear assembly. This mechanical failure resulted in the fuel pump drive gear failing to operate, which led to the engine being starved of fuel. Further inspection of the idler gear assembly showed sheared gear teeth.
An examination of the gearbox oiling system showed no evidence of thermal distress or failure occurring prior to the initial bearing failure. It was noted that the engine manufacturer had recently issued Service Bulletins regarding the installation of heavier duty gear assemblies for applicable engine installations.