What was found
NR 1 T-HANDLE AND FIRE LIGHT ILLUMINATED WITH AUDIBLE TONE IN FLIGHT. CREW RETURNED TO BASE. MAINTENANCE INSPECTED NR 1 ENGINE AREA AND FOUND NO EVIDENCE OF FIRE. CHECKED SECURITY AND INTEGRITY OF ALL NR 1 ENGINE FIRE DETECTION COMPONENTS AND WIRING WITH NO DEFECTS NOTED. C/W GROUND OPS CHECK WITH NO DEFECTS NOTED. REPLACED NR 1 ENGINE FORE AND AFT FLAME DETECTORS AS A PRECAUTION. PERFORMED OPS CHECK FLIGHT DUE TO INTERMITTENT NATURE. NO FURTHER DEFECTS NOTED.