36-10-00
ALL ú ú 02 Page 108 ú Feb 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
ENGINE BLEED AIR SUPPLY SYSTEM - DESCRIPTION AND OPERATION
__________________________________________________________
1. General (Fig. 1)_______
A. The engine bleed air supply system controls the temperature and the pressure of the air that is supplied to the airplane pneumatic ducts. The pneumatic ducts supply the pressurized air to the pneumatically operated airplane systems. The pneumatic system can also be pressurized with the Auxiliary Power Unit (APU) or a ground air source. The system supplies air for the folowing airplane systems:
-airplane pressurization and environmental control system (ECS)
-
wing leading edge and engine cowl thermal anti-ice protection
-
wing leading edge flap drives
-engine cross-starting
-air-driven hydraulic pump operation and reservoir pressurization
-cargo compartment heat
-
potable water tank pressurization.
B.
The primary source of air for the pneumatic system is engine bleed air from the high pressure compressors. The engine bleed control system includes the following components (Fig. 2):
-Intermediate Pressure Check Valve, 36-11-02/401
-Pressure Regulating and Shutoff Valve (PRSOV), 36-11-04/401
-
High Pressure Shutoff Valve (HPSOV), 36-11-05/401
-
High Pressure Controller, 36-11-06/401
-
Pressure Regulating Valve (PRV), 36-11-19/401
-
Pressure Controller, 36-11-20/401
-Air Supply Control and Test Unit (ASCTU), 36-11-30/401
-Engine Bleed Air Precooler, 36-12-01/401
-
Fan Air Temperature Sensor, 36-12-02/401
-
Fan Air Modulating Valve, 36-12-04/401.
C.
There are two sources of bleed air available from each engine: intermediate pressure (8th-stage) and high pressure (15th-stage). During low power engine operation, the three 15th-stage bleed ports supply compressed air. During high power engine operation, the two 8th-stage bleed ports supply compressed air. The intermediate pressure check valve will not permit high stage air to be supplied to the intermediate bleed ports (it is a one-way valve).
D.
The high pressure controller controls the position of the HPSOV. When the valve is open, 15th-stage air is supplied to the engine pneumatic manifold. When the valve is closed, 8th-stage (IP) air is supplied to the engine pneumatic manifold. The pressure controller controls the position of the PRV. The air from the IP/HP bleed ports is regulated to 59-69 psig by the PRV before it enters the precooler.
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36-11-00
ALL ú ú 02P Page 1 ú Feb 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
RESERVOIR AIR DRIVEN ANTI-ICING
PRESSURIZATION HYDRAULIC
PUMPS
Air Supply Distribution System
Figure 1 (Sheet 1)
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36-11-00
ALL ú ú 02P Page 2 ú Feb 10/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
PL 20
PRESSUREOVERPRESSUREPRESSUREPH 57
REGULATOR
CONTROL
SENSOR SWITCH
POPPET AND
TEMPERATURE PRESSURE
NOZZLE
OPEN
CONTROL REGULATION OPEN
REVFAN AIR
POPPETFLOW REV FLOW
OPEN
CONTROL
MODULATING LIMITERLEVER
VALVE CLOSE
STARTERVALVE CLOSE
FROM PRVCONTROLLER
CLOSE FAN AIR WTAI LP FAN AIRTEMPERATURE SENSOR
OPEN HPSOV PRESSURE REGULATING
BLEED AIR
AND SHUTOFF VALVE
OVERTEMPERATURE
OPEN CLOSED
SWITCH
PRECOOLER BLEED AIRTEMPERATURESENSOR TOCLOSED
A/CPRESSURE REGULATING
PACK HP
GROUND
VALVE CONNECTION
APU
SHUTOFF VALVE
HIGH PRESSURE
ISOLATIONVALVE NACELLE
TO
TO PRSOVANTI-ICINGVALVE
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