What was found
CREW REPORTED AT TOP OF DESCENT WHEN THROTTLES RETARDED, SMOKE FILLED CABIN AND COCKPIT. TURNED OFF NR 1 BLEED AND PACK. SMOKE CLEARED. ENGINE VIBRATION ALSO REPORTED. ENGINE REPLACED AT IAD FOR OIL IN THE GAS PATH. ON ENGINE DISASSEMBLY A FOREIGN OBJECT WAS FOUND IN THE OIL SYSTEM. A PIECE OF CARDBOARD ABOUT ONE INCH SQUARE WAS FOUND LOOSE IN THE NR 1 - NR 2 BEARING COMPARTMENT AREA. THE CARDBOARD WAS REMOVED. THE ENGINE WAS REASSEMBLED, TESTED AND RETURNED TO SERVICE WHERE IT HAS BEEN OPERATING NORMALLY.