vapilot2004,
I believe there is another fire detection system consisting of dual loop detectors consisting of Inconel tubes filled with a salt impregnated ceramic core and a Nickel wire. An AC power supply is connected to the Nickel wire and the Inconel tube is grounded. At low temps, the resistance of the core is high and the capacitance is low.
When the temp increases to a certain set temp along the length of the Fire Detector or a higher set temp along say 30cm of the detector, the resistance decreases and the capacitance increases allowing current flow to ground and actuating the Engine Fire Indication.
McHale.
