What was found
ON FLIGHT 3306 MAINTENANCE REPORTED SMOKE COMING OUT OF THE FRONT OF THE NR 1 ENGINE ON POST FLIGHT. THE NR 1 ENGINE HAD BEEN SHUT DOWN FOR OVER 10 MINUTES WHEN THIS WAS OBSERVED. ALL SHUTDOWN INDICATIONS HAD BEEN NORMAL. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED NR 1 ENGINE LOW PRESSURE TURBINE SHAFT PLUG IAW ROLLS ROYCE MM 72-59-15. THE OPERATIONAL CHECK AND LEAK CHECKS WERE GOOD. REF NRWC'S 855-DFW-00349 AND 855-DFW-00350. THE AIRCRAFT WAS RETURNED TO SERVICE.