What was found
(CAN) REDUCTION GEARBOX (RGB) SENT FOR INSPECTION AND REPAIR AFTER THE RGB WAS FOUND MAKING METAL. DISASSEMBLY OF THE RGB REVEALED THE SOURCE OF THE METAL WAS THE SPALLING OF THE NR 15 BEARING. THE SPALLING OF THE NR 15 BEARING APPEARED TO BE DUE TO ELECTRICAL ARCING DAMAGE. HOWEVER, THE LACK OF HIGH MAGNETISM IN THE RGB WAS NOT CHARACTERISTIC OF A LIGHTNING STRIKE. SINCE THERE WERE NO BEARING BORE ALIGNMENT OR LUBRICATION PROBLEMS FOUND, IT APPEARED THAT THE NR 15 BEARING SPALLED DUE TO ELECTRICAL PITTING CAUSED BY STRAY ELECTRICAL DISCHARGE FROM SOME AIRCRAFT COMPONENT. PART TC: 17,903.