757
MAINTENANCE MANUAL

 (2)  
Function

 (a)  
Airflow, in the direction of an arrow on the body of the check valve, overcomes the spring force and drives the flappers open. A stop-pin limits the flapper door travel. Reverse airflow will aid the spring in closing the valve flappers, preventing backflow through the valve.

 C.
Galley Ventilation Filter

_________________________
 (1)  
Physical Description

 (a)  
The galley ventilation filter press-fits into a ventilation inlet in each galley. The filter is made of open-weave fiberglass batting. The filter prevents foreign material from being drawn into the overhead ducting.

 3. Operation (Fig 2)
_________
 A. Functional Description
 (1)  
Normal Operation

 (a)  
The operating aft equip/lav/galley vent fan draws air out of the lavatories from beneath the toilet shroud, and out of the galleys through a ventilation filter, into the overhead ducting. The vent fan cools the E/E racks by a draw thru process. The air from all three areas is drawn to the check valve, where it is exhausted in the area of the outflow valve. The fan check valve prevents air from passing back through the non-operating fan.

 (b)  
The Aft Equipment/Lavatory/Galley Ventilation Fan 1 is the primary fan. The Aft Equip/Lav/Galley Vent Fan 1 Relay is energized if the system finds a ground through the fan 1 thermal switches. The energized relay provides 115v ac power to fan 1.

 (c)  
If fan 1 does not run, fan 2 will automatically provide back-up ventilation. The vent fan 2 relay is energized if the thermal switches are closed and the fan 1 fail relay finds a ground. The fan 1 fail relay finds a ground, common to both fans, if the fan 1 relay is relaxed. Once the vent fan 2 relay is energized, it supplies 115v ac power to operate fan 2.

 (2)  
Failure Indication

 (a)  
An EICAS maintenance message AFT EQ EXH FAN 1 will be displayed if fan 1 does not operate. An EICAS maintenance message AFT EQ EXH FAN 2 will be displayed when fan 2 fails to operate.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757
MAINTENANCE MANUAL

P11

ONE SW PER WINDING STORED IN NONVOLATILE MEMORY
Aft Equipment/Lavatory/Galley Ventilation Fans Schematic Figure 2
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 ú  03A  Page 5
 ú  May 20/98 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757 MAINTENANCE MANUAL
 VENTILATION SYSTEM - ADJUSTMENT/TEST
____________________________________
 1.  General_______
 A.  This procedure has instructions to do the operational test for the ventilation system. The ventilation system pulls air from the equipment cooling system, the lavatories, and the galleys, to the cabin pressure outflow valve.
 TASK 21-26-00-705-013
 2.  Operational Test - Ventilation System (Fig. 501)_____________________________________
 A.  References
 (1)  
06-41-00/201, Fuselage, Access Doors, and Panels

 (2)  
06-46-00/201, Entry, Service and Cargo Doors, Access Doors and Panels

 (3)  
24-22-00/201, Electrical Power Control

 (4)  
25-50-02/401, Cargo Compartment Sidewall Panels

 (5)  
25-50-03/401, Bulkhead Lining

 (6)  
31-41-00/201, Engine Indication and Crew Alerting System (EICAS)

 B.  
Prepare for the Test

 S 865-002
 (1)  
Supply the electrical power (Ref 24-22-00).

 S 865-003

 (2)  
Make sure these circuit breakers, on the overhead circuit breaker panel P11, are closed:

 (a)  
EICAS circuit breakers (5 places)

 (b)  
11N11, EQUIP COOLING FAN CONT AFT EXH XFR
　
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