*
Air supply distribution
*
Indicating.
Two air supply cabin pressure controllers (ASCPC) give control, indication and BITE for all sections of the pneumatic system and for the pressurization system.
See the air pressurization section for more information on the pressurization system (SECTION 21-30)
The controllers also set the amount of air that the air conditioning packs use (flow schedules) and give backup control to the cabin temperature controllers for air conditioning pack flow control and trim air control.
See the air conditioning chapter for more information on air conditioning backup control (CHAPTER 21)
The left ASCPC controls the left engine air supply and the right ASCPC controls the right engine air supply. Both controllers control the isolation valves and APU shutoff valve.
Engine Air Supply
The engine air supply part of the pneumatic system can operate at any one of three levels (modes) of control:
*
Digital (primary control)
*
Analog (backup control)
*
Pneumatic.
See the engine air supply section for more information about the engine air supply (SECTION 36-11).
The engine air supply system supplies the users with bleed air from two stages of the high pressure compressor (HPC). Low pressure bleed air comes from the 8th stage of the HPC. High pressure bleed air comes from the 15th stage of the HPC. These are the specified limits for pressure, temperature, and flow:
*
Pressure -0 through 75 psig (mode dependent)
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Temperature -380F (193C) or 250F (121C) (mode dependent)
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Flow -10 lbs/sec maximum (engine bleed airflow management).
The ASCPCs monitor the user systems to make decisions about how much air to supply. The ASCPCs manage engine bleed airflow three ways:
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Sheds user loads through an ARINC 629 signal (aft and bulk cargo heat, wing anti-ice)
*
Sheds user loads by direct control (air conditioning packs, air conditioning trim air)
*
Keeps engine bleed airflow to a limit.
EFFECTIVITY BEJ ALL 36-00-00
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PNEUMATIC -GENERAL DESCRIPTION
The ASCPCs also monitor the user systems to make decisions about the temperature of air to supply. The ASCPCs manage engine bleed air temperature in two ways:
*
Controls the flow of fan air though the precooler
*
Keeps engine bleed air flow to a limit.
The ASCPCs use the pressure regulating and shutoff valve controller (PRSOVC) and the high pressure and fan air controller (HPFAC) to control the engine bleed air. The PRSOVC and HPFAC usually adjust the positions of the pressure regulating and shutoff valve (PRSOV) and the high pressure shutoff valve (HPSOV) as necessary to regulate pressure and flow. The HPFAC adjusts the position of the fan air modulating valve (FAMV) as necessary to regulate temperature. See the engine air supply section for more information about the engine air supply (SECTION 36-11).
Air Supply Distribution
The air supply distribution system supplies air from the sources to the user systems. The ASCPCs monitor the condition of the airplane, air sources and user systems to make decisions about which source to use and where the air is needed. The ASCPCs open and close the isolation valves and APUSOV as necessary to distribute the air to the user systems.
Indicating
Eight sensors monitor the air in the pneumatic system (right side sensors not shown):
EFFECTIVITY
BEJ ALL
*
Manifold flow sensor (2)
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Manifold pressure sensor (2)
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Manifold dual temperature sensor (2)
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Intermediate pressure sensor (2).
RVDTs monitor valve position for these valves:
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Left, right, and center isolation valves
*
APU shutoff valve
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Left and right fan air modulating valves.
The left and right ASCPCs monitor the sensors for flow, pressure, and temperature data. The ASCPCs monitor the RVDTs for valve position data. The ASCPCs use the data to control these components:
*
Three isolation valves
*
APU shutoff valve
*
Two pressure regulating and shutoff valve controllers (PRSOVC)
*
Two high pressure fan air controllers (HPFAC).
The ASCPCs send information to the airplane information management system (AIMS). The AIMS gives EICAS messages and synoptic and maintenance information.
Interfaces
The pneumatic system has interfaces with these systems and components:
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PNEUMATIC -GENERAL DESCRIPTION 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 气源 Pneumatic(2)
