E/E COOLING SMOKE DETECTION -E/E COOLING SMOKE DETECTOR -INTRODUCTION

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E/E COOLING SMOKE DETECTION -E/E COOLING SMOKE DETECTOR -FUNCTIONAL DESCRIPTION

General
The two channels contain identical circuits. The forward cargo smoke detector makes a decision about which channel operates. The operating channel monitors the optical smoke detectors.
Optical Smoke Detectors
The optical smoke detector has these parts:
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Two source light emitting diodes (LEDs)

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Two intensity monitor photodiodes

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Two scatter detector photodiodes.

One set of diodes connects to channel 1. The other set of diodes connects to channel 2.
Inside the smoke detection chamber, air flows between a source LED and a scatter detector photodiode. Normally, only a small amount of light from the lED reaches the scatter detector. If the air has smoke in it, the smoke particles reflect more light onto the scatter detector. This causes a smoke alarm signal.
The intensity monitor photodiode makes sure the source LED is on and keeps the output of the source LED constant. This configuration also finds contamination of the LED and photodiodes.
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BITE
The detector does power-up and periodic BITE tests. The power-up BITE includes these tests:
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Supply voltage

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Source LED intensity

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Optical contamination

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Scatter detector operation.

The periodic BITE test monitors the source LED intensity and the scatter detector operation.
If the operating channel fails, BITE sends a signal to the forward cargo smoke detector. That smoke detector causes the other E/ E cooling smoke detector channel to operate.
Inputs And Outputs
The smoke detector gets these inputs from the forward cargo smoke detector:
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10.5v dc power

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LED 1 and 2 on/off

The smoke detector sends these outputs to the forward cargo smoke detector:
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Smoke alarm, chamber 1, channel 1

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Smoke alarm, chamber 2, channel 1

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Smoke alarm, chamber 1, channel 2

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E/E COOLING SMOKE DETECTION -E/E COOLING SMOKE DETECTOR -FUNCTIONAL DESCRIPTION
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Smoke alarm, chamber 2, channel 2

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Channel 1 BITE test pass/fail

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Channel 2 BITE test pass/fail.

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E/E COOLING SMOKE DETECTION -E/E COOLING SMOKE DETECTOR -FUNCTIONAL DESCRIPTION

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E/E COOLING SMOKE DETECTION -FUNCTIONAL DESCRIPTION

General
The E/E cooling smoke detector connects to the forward lower cargo smoke detector. The cargo smoke detector has two identical electronic channels. Channel 1 controls during one electrical power cycle, channel 2 controls during the next power cycle.
Each channel of the E/E cooling smoke detector connects to the related channel in the forward lower cargo smoke detector. The E/E cooling smoke detector gets these inputs from the cargo smoke detector control channel:
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DC power

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LED 1 and 2 on/off signals.

The E/E cooling smoke detector sends these outputs to the Lower cargo smoke detector control channel:
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Alarm 1 (smoke in detection chamber 1

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Alarm 2 (smoke in detection chamber 2)

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BITE pass/fail.

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Smoke Detection
If there is smoke in one or two detection chambers, the E/E cooling smoke detector sends an alarm signal to the forward cargo smoke detector. The forward cargo smoke detector sends the alarm signal through the ARINC 429 bus to the ASG cards and left ECS miscellaneous card. The ASG cards transmit the alarm signal over the ARINC 629 buses to these systems and components:
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Overhead panel ARINC 629 system (OPAS)

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AIMS

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Right systems cardfile.

The OPAS makes a ground to turn on the E/E cooling override light. The AIMS causes a status message to show. The central maintenance computing function records the event as a flight deck effect for the in-bound flight. In the right systems cardfile, the ASG cards send the alarm signal to the right ECS miscellaneous card. The ECS miscellaneous cards put the equipment cooling system into the override mode. This sends the smoke overboard.
　
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