14-1Rev. A Sept. 18, 2007

Fire Detection System

Model S64F Helicopter

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Fire Detection System The fire detection system consists of a thermal fire detection

system and an optical surveillance system. They both monitor potential fire zones and have activate

warning indicators in the cockpit. The fire detection system consists of the following components:

a) Fire Warning Test Panelb) Fire Detector Controllerc) Sensing Loopsd) Control Amplifiere) Flame Detector Unitf) Warning Lights

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Fire Detection System

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Component DescriptionFire Warning Test Panel: The fire warning test control panel contains switches for testing

the fire surveillance system. The panel contains a toggle switch, a five position selector switch and three panel lamps.

Sensing Loop

Fire Eyes

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Component DescriptionFire Detector Controller: Two control units, installed in

the attic compartment, monitor the resistance of the sensing elements.

In case of fire or engine over heating, sensing element resistance drops, causing the control unit to signal an alarm.

To prevent false alarms, a delay circuit prevents the warning lights from going on unless the heat continues for more than a moment.

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Sensing Loop: Four temperature-sensitive fire detection element sensing

loops, two for each engine warning circuit, are used in the fire detection system.

The loops are attached to the engine deck and aft firewall. A sensing loop is a hermetically sealed, flexible

temperature sensing element consisting of a center conductor and the outer sheath with two end fittings.

The space between the center conductor and the sheath with contains a salt, which lowers its impedance allowing more current to flow when heated by a fire or overheat condition.

Removal of the heat will reset the system automatically.

Component Description

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Sensing Loops

Sensing Loop

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Control Amplifier: The control amplifiers are

located in the attic on the right side.

They monitor the flame detector output and provide a 28vdc signal to the warning lights in the cockpit.

Component Description

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Component DescriptionFlame Detector Units: The flame detection system consists of 11 detection units. Five flame detectors are located around each engine, and

one at the APP unit. The flame detector is a photo conductive cell that provides

an output signal to the control amplifier when a fire occurs. The detectors react to a light frequency which is unique to a

hydrocarbon flame.

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Flame Detector Units

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Warning Lights: A warning light for each engine, located in the cockpit

overhead quadrant area, goes on whenever a fire is detected.

The warning light has a light capsule with the legend opaque marking on a transparent red background.

Each fire warning has a press to reset function. An APP fire warning is located on the APP Control Panel. In addition, there are two master FIRE warning lights for the

pilot and copilot on the forward instrument panel.

Warning lights

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Warning Lights

Engine Fire Light Master Fire Light

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Theory of Operation The fire detection system provides for two methods of fire

detection. The thermal fire detection system uses heat sensing loops

which allow more current to flow when heated by a fire or overheat condition.

The increased current flow causes the detector controller to send a signal to the warning lights.

The optical warning system uses optical detection units to a light frequency which is unique to a hydrocarbon flame.

This condition completes a circuit in the control amplifier and the amplifier sends a signal the appropriate warning lights.