What was found
DURING CRUISE, RECEIVED NR 1 ENG 'FIRE WARNING ALERT'. CREW RETARDED THROTTLE TO FLIGHT IDLE AND ALERT DISCONTINUED. CREW ELECTED TO RETURN. ENGINE WAS CONTINUED TO OPERATE AT FLIGHT IDLE FOR DURATION OF FLT. A/C LANDED W/O FURTHER INCIDENT. MX PERSONNEL GROUND RAN ENGINES AT MAX POWER. ALERT WAS DUP ON GROUND. FOUND BOTH A AND B PYLON FIRE LOOPS FAULTING. BOTH FIRE LOOPS WERE REPLACED. ALL PNEUMATIC DUCTS WERE INSPECTED FOR MALFUNCTIONS. SEVERAL CLAMPS WERE RE-TORQUED. PNEUMATIC 'DECAY CHECK' WAS PERFORMED AND SUCCESSFULLY PASSED. ENGINE WAS AGAIN GROUND RUN WITH NO FAULT INDICATION. A/C WAS TEST FLOWN. NO FAULTS NOTED. A/C WAS RETURNED TO SERV. (M)