747-400
MAINTENANCE MANUAL
ENGINE BLEED CONTROL MODULE
SEE B
P5 OVERHEAD PANEL
AUXILLARY EICAS DISPLAY
SEE A
DUCT PRESSURE INDICATION
DUCT
PRESSURE TEMP `C INDICATION
F/D
U/D 26 25 OUTFLOW VALVES26 25 MASTER 25
L R ENGINE BLEED AIR
OPA B C D E
OVERPRESSURE
26 25 26 25 26 25 26 25 26 25
WARNING LIGHT
CL FWD
MAN AUTOAFT BULK
26 25 26 25 26 25
HI FLOW HI FLOW 1 PACKS 2 PACKS 3
1 2 3
NORM NORM NORM
OFF A OFF A OFF A
OFF PACK CONTROL A PACK CONTROL B B B B
DUCT EXT AIR DUCT L ISLN R ISLN
PSI PSI
0 28 VALVE VALVE
WING WING
TAI TAI WING WING
TAI TAI
APU
APU
OFF FAULT SYS FAULT SYS ON FAULT SYS FAULT SYS
NAC NAC 1 2 VALVE 3 4
TAI TAI
ON ON ENGINE ON ON
1 ENG 2 3 ENG 4 OFF OFF BLEED OFF OFF
ENGINE BLEED CONTROL MODULE
(EICAS ECS PAGE) AUXILIARY EICAS DISPLAY B
A
Engine Bleed Air Pressure Indication Figure 3
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747-400
MAINTENANCE MANUAL
B51054
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A
747-400
MAINTENANCE MANUAL
B. The bleed air overpressure switch is connected by a pneumatic sense line to a fitting at the precooler outlet. It senses the engine duct pressure for overpressure condition.
(1) When the bleed air pressure goes above 76 psig, the overpressure switch opens. If the switch stays open for more than 65 seconds an input is sent to the ASCTU logic circuits. A "SYS FAULT" light will come on and a BLEED 1, 2, 3 or 4 EICAS advisory message will come into view on EICAS along with its associated BLEED OVPRESS 1, 2, 3 or 4 EICAS status message, when the ECS status display is selected.
5. Bleed Air Pressure Indication and Monitoring System
___________________________________________________
A. The BITE logic continuously monitors the bleed pressure sensor for high or low engine manifold pressure; and also monitors the integrity of the overpressure switch.
B. External air pressure source indication is shown by an EXT AIR message on the EICAS ECS synoptic page when ground air is available to pack 1, pack 2, or pack 3.
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747-400 MAINTENANCE MANUAL
ENGINE BLEED AIR PRESSURE INDICATING SYSTEM - ADJUSTMENT/TEST
_____________________________________________________________
1. General_______
A. This procedure contains one task. It does a system test of the
indicating system for the engine bleed air pressure.
B. This system test completes the requirement of an operational test. A system adjustment is not necessary.
C. It is necessary to open one of the access doors for the air conditioning bay to get access to a duct pressure transmitter.
D. You must use a controlled pressure source (0 to 100 psi) to pressurize the sense port of the duct pressure transmitter.
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