What was found
THE NR 1 BEARING FAILED RESULTING IN A CATASTROPHIC FAILURE AND AN IN FLIGHT SHUTDOWN. THE ENGINE WAS REMOVED AND SENT FOR REPAIR. DURING THE FAILURE INVESTIGATION, ELECTRICAL ARCING WAS FOUND ON THE NR 1 BEARING, INPUT SHAFT, AND STARTER/GENERATOR DRIVE GEAR. SD ADVISORY NR AV-2007-05 ISSUED THAT STATES ACCUMULATION OF BRUSH DUST CAN CAUSE STARTER GENERATOR ARMATURE LEAKAGE. OUR RESEARCH DOES NOT SHOW ANY PREVENTATIVE MAINTENANCE ACTIONS THAT MAY BE PERFORMED TO THE STARTER GENERATOR TO CHECK FOR ELECTRICAL DISCHARGE. (K)