What was found
UPON ROTATION, ENGINE ROUGHNESS WAS NOTED BY PILOT. TOWER REPORTED SMOKE FROM RIGHT ENGINE. LANDING PATTERN WAS ENTERED IMMEDIATELY, AND UNEVENTFUL LANDING MADE. MAINTENANCE COULD NOT DUPLICATE PROBLEM ON GROUND. RUN-UPS AND ENGINE INSPECTIONS SHOWED NO VISUAL EXTERNAL DEFECTS. MAINTENANCE INVESTIGATIONS ARE CONTINUING INTO THE PROBLEM. OCCURRED NOV 19, 1996.