What was found
THE NR 2 ENGINE FIRE WARNING LIGHT FOR B-LOOP (A LOOP WAS ON PLACARD) ILLUMINATED TEN MINUTES AFTER TAKEOFF. THE NR 2 ENGINE WAS SHUT DOWN, BOTH FIRE BOTTLES WERE DISCHARGED AND THE AIRCRAFT WAS RETURNED TO LGW WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND NO EVIDENCE OF FIRE. MAINTENANCE FOUND BOTH A AND B FIRE LOOPS CHAFED THROUGH. BOTH LOOPS WERE REMOVED AND REPLACED. IN ADDITION, BOTH FIRE BOTTLES WERE REPLACED.