SENSOR COVER COVER
SENSOR - SMOKE DETECTOR
A
Lavatory Smoke Detector Cleaning
Figure 702
C19079
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26-13-01
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
S 867-018
(7)
Move the blade of the standard screwdriver between the smoke sensor and cover.
S 017-019
(8)
Remove the cover from the smoke sensor.
S 027-047 WARNING: DO NOT DISASSEMBLE THE SENSOR CELL ASSEMBLY DUE TO THE
_______ RADIOACTIVE MATERIAL CONTAINED WITHIN.
CAUTION:_______DO NOT TOUCH THE ELECTRODE INSIDE OF THE SENSOR. DAMAGE TO THE SENSOR COULD OCCUR.
(9)
Pull out the mesh from the smoke sensor. S 967-021
(10)
If the mesh is very dirty, replace it with a new mesh. S 177-022
(11)
If the mesh is dirty, wash the mesh with a synthetic detergent and luke-warm water.
S 167-023
(12)
After you wash the mesh, dry it with compressed air. S 167-024
CAUTION:_______DO NOT BLOW VIOLENTLY INTO THE SMOKE DETECTOR CHAMBER. THIS CAN CAUSE STATIC ELECTRICITY ON THE ELECTRODES.
(13)
Carefully blow out the dust in the chamber. S 417-025
(14)
Install the mesh, smoke sensor, and cover. NOTE: Align the cover with the applicable hole in the sensor top.
____
S 437-026
(15)
Install the detector assembly (Ref 26-13-01/401). S 737-028
(16)
Do the Lavatory Smoke Detection System Test (Ref 26-13-00/501).
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747-400 MAINTENANCE MANUAL
MAIN DECK CARGO COMPARTMENT SMOKE DETECTION SYSTEM - DESCRIPTION AND OPERTION
_____________________________________________________________________________
1. General_______
A. The main cargo compartment is divided into sixteen smoke zones No. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16. Zones 1 through 7 are connected to the FWD venturi ejector and zones 8 through 16 are connected to the AFT venturi ejector. Six smoke sampling ports in each smoke zone are connected to two detectors connected in dual loop "AND" logic configuration. These dual detectors are installed in main deck cargo compartment.
B. The detection systems use dc power from 28-volt dc bus No. 2 and No. 4. The system circuit breaker is located on P7 and P6 overhead circuit breaker panel respectively.
C. The main cargo smoke detection system is a draw-through air sampling system. A venturi ejector using bleed air, creates a vacuum which pulls the sample air through the system. Multiple pick-up points are provided through out the main deck cargo compartment.
2. Smoke Detector (Fig. 1)______________
A. The detector consists of a photocell and pilot light (or Light Emitting Diode) in a light-proof chamber plus associated amplifier, output, and test circuits on a printed circuit board. The detector has inlet and outlet tubes to provide air and smoke.
B. Smoke entering the light-proof chamber reflects the light from the pilot lamp (or Light Emiting Diode) onto a photocell. Then the photocell causes an increase in output voltage and, a signal is relayed to the flight deck. The generated signal illuminates a light on the P5 pilot's overhead panel, creates an EICAS messages, and activates MAWEA.
3. Smoke Detector Ejector (Fig. 1)______________________
A. The vacuum for the main manifold is created by a venturi ejector. There are two ejectors, one located on the aft end of the forward lower cargo compartment, and one on the forward end of the aft lower cargo compartment. The ejectors receive bleed air from the pneumatic system crossover duct.
4. Pressure Switch_______________
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