FIRE PROTECTION - CARGO COMPARTMENT SMOKE DETECTION – INTRODUCTION

FIRE PROTECTION - CARGO COMPARTMENT SMOKE DETECTION – INTRODUCTION

Purpose

The lower cargo compartment smoke detection system gives warnings in the flight deck if there is smoke in a lower cargo compartment. There are warnings for the forward and the aft lower cargo compartments.

General Description

These are the components of the lower cargo compartment smoke detection system:

• Smoke detectors
• Cargo electronic units
• Cargo fire control panel
• Aural warning unit
• Fire warning lights.

The smoke detectors are in a dual loop configuration.

Each smoke detector monitors the cargo compartment for smoke and heat. If the detector senses smoke or heat, a signal goes to the cargo electronic unit. The cargo electronic unit sends a signal to the flight compartment for indications.

These are the indications in the flight compartment:

• FWD or AFT cargo fire light on the cargo fire control panel comes on
• P7 FIRE WARN lights come on
• Bell sound from the aural warning unit.

Component Location

The lower cargo compartments have many cargo smoke detectors and one cargo electronic unit in each compartment.

The forward lower cargo compartment has four smoke detectors. The aft lower cargo compartment has six smoke detectors. The detectors are in the ceiling of the compartments.

You remove a protective guard to get access to a smoke detector.

One cargo electronic unit is in the ceiling on the left side of each cargo compartment, inboard of the cargo door.

You remove a cover to get access to a cargo electronic unit.

LOWER CARGO COMPARTMENT SMOKE DETECTION – SMOKE DETECTOR

The smoke detectors monitor air in the forward and aft lower cargo compartments for smoke and heat.

The smoke detectors are in pans in the ceiling of the forward lower cargo compartment and in the aft lower cargo compartment.

The forward and aft smoke detectors are the same. The smoke detectors have these components:

• Electrical connector
• Smoke detection chamber (internal)
• Electronic circuit (internal).

Functional Description

The smoke detectors use photoelectric cells to detect smoke. The smoke detector gives an alarm signal if it senses smoke or if it senses air temperature more than 230F (110C).

Purpose

The cargo electronic units monitor the forward and aft lower

cargo compartment smoke detectors.

Physical Description

The forward and aft cargo electronic units are identical. The

cargo electronic units have these items:

• Two electrical connectors (at back of unit)
• 16 red light emitting diodes (LEDs)
• Lamp test switch
• System test switch
• Electronic circuits (internal)

General Description

There are four smoke detectors (two in loop A and two in loop

B in the forward cargo compartment. Red LED lights on the

front of the CEU labeled 1A, 1B, 2A and 2B connect to smoke

detectors. The remaining LED lights are active and connect

externally by a jumper cable loop.

There are six smoke detectors (three in loop A and three in loop

B) in the aft cargo compartment. Red LED lights on the front of

the CEU labeled 1A, 1B, 2A, 2B, 3A and 3B connect to smoke

detectors. The remaining LED lights are active and connect

externally by a jumper cable loop.

CARGO COMPARTMENT SMOKE DETECTION - CARGO FIRE CONTROL PANEL

Purpose

The cargo fire control panel monitors the fire protection system

for these conditions:

• Lower cargo compartment smoke
• Lower cargo compartment overheats
• Smoke detector fault conditions
• Cargo fire extinguisher bottle squib condition
• Cargo fire extinguisher bottle discharge.

The cargo fire control panel lets you do these functions:

• Set the mode of operation (single or dual loop smoke detector operation)
• Operate a cargo fire extinguisher bottle
• Do a test of the cargo fire extinguisher bottle squibs
• Do a test of the lower cargo fire protection system
• Do a test of the fault detection circuits.

Physical Description

These are the cargo fire control panel components

:

• Amber DETECTOR FAULT light
• DET SELECT switches
• Green FWD and AFT EXT lights
• Amber DISCH switch light (guarded)
• FWD and AFT cargo fire arm switches
• TEST push-button switch.

General Description

The DETECTOR FAULT amber light comes on if a cargo smoke

detector has a fault.

Each DET SELECT switch has these three positions:

• NORM - both detector loops are necessary to sense a smoke or overheat condition to give a fire indication
• A - only the A loop is necessary to sense a smoke or overheat condition for a fire indication
• B - only the B loop is necessary to sense a smoke or overheat condition for a fire indication.

The green FWD and AFT EXT lights show extinguisher bottle squib continuity.

The DISCH switch light comes on when the bottle pressure is less than 250 psi.

The TEST push button does a check of the cargo smoke detectors and the extinguishing system.

The FWD or AFT red cargo fire lights come on if a fire indication is given by the smoke detectors.