Incident Description
During initial climb to altitude, the right engine experienced an uncommanded shutdown. The flight crew declared an emergency and subsequently performed an uneventful single-engine landing at the departure airport.
Post-Incident Findings
After the incident, metallic chips were discovered on the chip detector. Examination of the accessory gear housing assembly (part number 3103601-6) revealed that all bearing balls were missing. Fragments of these ball bearings were found in the bottom of the engine case. The bearing races exhibited pitting and scoring.
According to diagnostics performed by the operator, the disintegration of the bearings allowed the gear shaft to drop down and contact the gears of the accessory drive idler gear assembly. This contact resulted in the fuel pump drive gear not being driven, causing the engine to be starved of fuel. Inspection of the idler gear assembly showed sheared gear teeth.
Gearbox Oiling System Examination
Examination of the gearbox oiling system revealed no evidence of failure or thermal distress prior to the initial bearing failure.
Service Bulletins
The engine manufacturer had recently issued Service Bulletins addressing the installation of heavier duty gear assemblies in applicable engine installations.