What was found
AFTER TAKEOFF AT APPROXIMATELY 1500 FT. THE NR 1 ENGINE FIRE WARNING (BOTTLE AND BELL) ACTIVATED. AOM EMERGENCY PROCEDURES PER 2-C-2 COMPLIED WITH. DUMPED APPROXIMATELY 12000 POUNDS OF FUEL PER AOM PROCEDURE 2-A-B-1. RETURNED TO AIRPORT. PREPARED FOR 2 ENGINE FERRY PER MAI FORM 14 B/C AND MM 71-00 224C AND SUBSEQUENT. ACTION TAKEN: INSPECTED ENGINE, FOUND 13 STAGE AIR TUBE RUPTURED CAUSING MELTING OF WIRE HARNESS. REMOVED AND REPLACED NR ENGINE IAW 727-7101 ENGINE CHANGE SHEETS. RUNUP COMPLETED AND AIRCRAFT RETURNED TO SERVICE.