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747-400 MAINTENANCE MANUAL
LAVATORY SMOKE DETECTION SYSTEM - DESCRIPTION AND OPERATION
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General
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A. Each lavatory has a smoke detector unit installed on or near the lavatory ceiling. When the concentration of smoke at the sensor reaches a preset threshold, the smoke detector unit provides an aural warning to alert the cabin attendants and flight crew.
NOTE: The lavatory smoke detectors may not be triggered by cigarette
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smoke.
Smoke Detector Unit (Fig. 1)
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A. A smoke detector unit is installed on or near the lavatory ceiling in all main deck and upper deck lavatories and receives power from the airplane 28-volt dc bus No. 2 and bus No. 4.
B. The smoke detector uses an ionization sensor to detect smoke. A very small amount of radioactive material ionizes the air between two electrodes allowing current to flow through the air between the electrodes. Any smoke particles present interfere with this current flow. The change in current flow is sensed by a current amplifier which outputs a signal to turn on the alarm horn and alarm indicator light.
C. Each smoke detector unit consists of the following:
(1)
Alarm horn, activated with a continuous tone when smoke is detected.
(2)
Alarm indicator light (red), which comes on when smoke is detected.
(3)
Power-on indicator light (green), which comes on when power is applied to the smoke detector unit.
(4)
Interrupt switch.
(5)
Smoke sensor.
D. All smoke indications go away automatically when the smoke is gone.Operation (Fig. 2)
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A. The detection system is activated automatically when electrical power is applied to the airplane and the system circuit breakers are closed.
B. Each smoke detector will activate an alarm horn, and an alarm indicator light (red) when smoke reaches the preset threshold.
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747-400
MAINTENANCE MANUAL
LAVATORY SMOKE DETECTOR
INTERRUPT
SWITCH POWER INDICATOR (GREEN)
LAVATORY (EXAMPLE) ALARM INDICATOR (RED)
ALARM HORN
SMOKE SENSOR
SMOKE DETECTOR (EXAMPLE)
Lavatory Smoke Detection System - Component Location
Figure 1
B42771
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747-400
MAINTENANCE MANUAL
28V DC BUS 4
28V DC BUS 4
LAV SMOKE
DET 2
P180 DC POWER DISTRIBUTION PANEL
WHEN SMOKE IS DETECTED, HORN IS ACTIVATED
Lavatory Smoke Detection System Simplified Schematic Figure 2
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747-400 MAINTENANCE MANUAL
LAVATORY SMOKE DETECTION SYSTEM - ADJUSTMENT/TEST
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：747-400 AMM 飞机维护手册 防火 FIRE PROTECTION 1(45)
