What was found
UPON DESCENT INTO TYS POWER LEVERS AT FLT IDLE FLT DECK/CABIN STARTED TO FILL WITH SMOKE WITH BOTH BLEEDS ON. TURNED OFF ENGINE BLEEDS AND SMOKE STARTED TO DISSIPATE. F/A REPORTED THAT THE CABIN GOT VERY WARM AT THIS TIME. INSPECTED NR 1 ENGINE FOR OIL OTY AND FOR LEAKS, OIL QTY BETWEEN 1 QT AND FULL, FOUND OIL LEAK TO BE LEAKING IN DEFUSER TUBE AREA. GROUND RAN A/C WITH CREW, SEE FERRY PERMIT FOR LIMITS (MECHANIC SHOT SINGED). REMOVED AND REPLACED O-RINGS TO BEARING CAVITY AND REMOVED AND REPLACED AIR SWITCHING VALVE NR 1 OPS AND LEAK CHECK GOOD.