What was found
(CAN) ON DESCENT ODOR OF SMOKE VERY STRONG. SMOKE ALARM SOUNDED IN FRONT AND BACK OF AIRCRAFT. ODOR PERSISTED FOR APPROX 10 MINUTES. QRH DRILL CARRIED OUT. ALL PARAMETERS NORMAL. SMOKE ODOR APPEARS TO COME FROM AIR CONDITIONING. OIL FOUND IN THE NR 1 ENGINE LPT SHAFT CREATING SMOKE THROUGH THE FRONT. REAR CONE REMOVED FOR ACCESS. LPT REAR PLUG SEAL REPLACED. WORK COMPLETED AS PER ENGINE MANUAL 72-00-53.