(4)  
Drill the backup plate and panel for the installation of the blind rivets.

 S 422-074

 (5)  
Install the new flapper and salvaged backup plate. Use the blind rivets.

 (6)  
Install the smoke detector blower (AMM 26-16-02/401).

 S 422-075
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757 MAINTENANCE MANUAL
 S 702-082
 (7)
Do a Check of the Flapper Valve Integrity.

 S 022-094

 (8)
Close cargo door (AMM 52-34-00/201).

 TASK 26-16-05-102-076
 5.  Clean the Flapper Valve_______________________
 A. Reference
 (1)
AMM 26-16-02/401, Smoke Detector Blowers

 (2)
AMM 52-34-00/201, No. 1 and No. 2 Cargo Door

 B. Do the Procedure
 (1)  S 012-095Open main cargo door (AMM 52-34-00/201).
 (2)  S 022-077Remove the applicable smoke detector blower (AMM 26-16-02/401).
 (3)  S 122-078Remove the remaining material on the flapper valve or around the open end of the flapper valve. Use a soft bristle brush and soap and water.
 (4)  S 162-079Let the flapper valve dry.
 (5)  S 422-080Install the smoke detector blower (AMM 26-16-02/401).
 (6)  S 702-083Do a Check of the Flapper Valve Integrity.
 (7)  S 022-096Close cargo door (AMM 52-34-00/201).

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 ALL  ú ú 01 Page 209 ú Jan 28/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757 MAINTENANCE MANUAL
 WHEEL WELL FIRE DETECTION - DESCRIPTION AND OPERATION
_____________________________________________________
 1.  General_______
 A.  A continuous single loop sensor system is installed in the left and right main wheel wells for detecting overheat conditions in those areas. When an overheat temperature is reached, the resistance of the sensor decreases such that a warning alert is provided to the flight crew.
 B.  An overheat condition causes the master warning lights (red) on the glareshield (P7) to come on, the fire bell to sound, the WHEEL WELL FIRE (red) light to come on, and the EICAS indicator (P2) to display WHEEL WELL FIRE. The fire bell and master warning lights are reset by pressing one of the lights. The WHEEL WELL FIRE light and the EICAS display will remain on as long as the overheat condition exists (AMM 31-41-00/001).
 C.  A test switch is provided on the fire/overheat test module at the rear of the pilots' control stand (P8). When operated, the test switch simulates a ground on the continuous loop sensor. The duct leak and wheel well overheat control card detects the ground as being an overheat condition and causes a wheel well fire warning.
 D.  The wheel well fire detection system consists of four sensor elements, two circuit cards, a warning light and test switch. The system utilizes 115 Vac electrical power from the standby bus, and 28 Vdc from the battery bus.
 2.  Component Details (Fig. 1)_________________
 A.  Wheel Well Overheat Detectors
_____________________________
 (1)  
The continuous loop sensor is composed of four elements, two in each wheel well. The sensor loop in each wheel well is mounted around the overhead by silicone bushings. The two elements begin on the inboard bulkhead, and are connected together at the outboard side via the forward and aft bulkheads. The elements are connected via wiring to the other wheel well elements and to the control card (P50).

 (2)  
The overheat sensors contain a thermistor material. The resistance of this material decreases as the temperature of the material increases. At a temperature greater than 400°F | 20°F, the sensor provides an alarm signal (ground) to the control card in the P50 card file. When the temperature of material cools sufficiently, the alarm signal is automatically cancelled.

 B.  Duct Leak and Wheel Well Fire Circuit Cards
___________________________________________
　
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