What was found
DURING CRUISE, THE NUMBER FOUR ENGINE FIRE LIGHT ILLUMINATED AND THE FIRE BELL SOUNDED. THE ENGINE WAS SECURED AND A FIRE BOTTLE WAS DISCHARGED. DURING THE WINDMILLING PROCEDURE, THE FIRE LIGHT FLICKERED MOMENTARILY. THE FLIGHT CONTINUED WITHOUT FURTHER INCIDENT TO ILN. FOUND THE FORWARD UPPER FIRE DETECTOR ELEMENT DEFECTIVE. REMOVED AND REPLACED THE NUMBER FOUR ENGINE FIRE DETECTOR ELEMENT. SYSTEM OPERATIONAL CHECKED GOOD IAW DC-8 MM CHAPTER 26.