What was found
DURING INITIAL CLIMB-OUT, FLIGHT CREW RECEIVED NR 2 ENGINE 'FIRE ALERT'. INDICATION EXTINGUISHING WHEN NR 2 ENGINE THROTTLE RETARDED TO IDLE. FLIGHT CREW ELECTED TO RETURN TO POINT OF DEPARTURE FOR MAINTENANCE. AIRCRAFT RETURN AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE PERSONNEL PERFORMED VISUAL INSPECTION OF NR 2 ENGINE WITH NO DEFECT NOTED. DURING GROUND TEST, WERE UNABLE TO DUPLICATE FAULT. AS A PRECAUTION, REPLACED NR 2 ENGINE FIRE DETECTION CONTROL UNIT. PERFORMED RETURN TO SERVICE TEST OF UNIT WITH NO FAULT NOTED. PERFORM GROUND RUN OF NR 2 ENGINE TO MAX PERMISSIBLE POWER WITH NO FAULT NOTED. AIRCRAFT RETURN TO SERVICE. (M)