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following components are discussed in the singular sense to avoid repetition:
• HP Bleed Air Pressure Regulator and Shutoff Valve
• Bleed Air Pressure Regulator and Shutoff Valve
• Fan Air and Fan Air Modulating Valve
• Precooler
• Temperature and Pressure Sensors/Switches
In addition to the above-listed left and right side components, the following
subsystems and components are included:
• Bleed Air Isolation Valve
• APU Bleed Air Distribution
• External Air Distribution
• Door Seal Pressure Distribution
• Total Air Temperature Probe Aspiration
2. Description of Subsystems, Units, and Components:
(See Figure 1, Figure 2 and Figure 3.)
NOTE:
Items A through E are identical to the left and right
sides, therefore only one side will be discussed.
OPERATING MANUAL
2A-36-00 PRODUCTION AIRCRAFT SYSTEMS
Page 2
October 11/02
Revision 8
A. HP Bleed Air Pressure Regulator and Shutoff Valve:
The HP bleed air pressure regulator and shutoff valve (commonly referred
to as the HP valve) is a butterfly-type modulation valve installed in the highstage
bleed air line to regulate, modulate or shut off 12th stage bleed air. It
works in conjunction with the solenoid “A” and “B” HP control valve and the
dual port solenoid shutoff valve to provide three distinct modes of operation
(these modes are described below). The valves receive power from the
Essential 28V DC bus through the L BLEED AIR and R BLEED AIR circuit
breakers, respectively. A description of this valve’s two controlling
components follows:
(1) 12th Stage Servo Controller (Solenoid A and B HP Control Valve):
The 12th stage servo controller (solenoid A and B HP control valve)
provides the necessary commands to the HP bleed air pressure
regulator and shutoff valve to achieve the proper mode of control.
The controller is a remote pressure regulating servo with a solenoid
shutoff feature, a relief valve, and a thermostat connection for
sensing downstream temperature. It is linked to the bleed air
temperature sensor and the bleed air temperature anticipator sensor
via the dual port solenoid shutoff valve.
(2) Dual Port Solenoid Shutoff Valve:
The dual port solenoid shutoff valve is installed to give a desired
mode of system operation. The unit is pneumatically linked between
the 12th stage servo controller (solenoid A and B HP control valve),
the HP bleed air pressure regulator and shutoff valve, and the bleed
air temperature sensor/anticipator sensor control set. Pneumatic
control air is received from the solenoid A and B HP control valve via
the actuator port. Control sensor plumbing is connected to the
control port. The pneumatic signal is then manipulated by the dual
port solenoid shutoff valve to give the proper HP bleed air pressure
regulator and shutoff valve control.
As stated previously, the HP bleed air pressure regulator and shutoff valve
provides three distinct modes of operation. These are the pressure
regulation mode, the temperature modulation mode and the single pack
mode. A description of these modes follows:
(3) Pressure Regulation Mode:
In the regulation mode, the HP bleed air pressure regulator and
shutoff valve opens or closes to regulate bleed air to a constant
pressure. If 7th stage pressure falls below 18 ±2 psi during low
power settings such as idle descent or taxi, solenoid A of the 12th
stage servo controller is energized to regulate the HP bleed air
pressure regulator and shutoff valve and maintain pressure at 18 ±2
psi. During normal operations, the dual port solenoid shutoff valve
remains closed.
It should be noted here that although 18 ±2 psi is a design reference
pressure, it may not always be attainable due to ambient conditions.
Pressures in the range of 12-16 psi at idle power are not considered
abnormal as long as they are stable.
On airplanes Serial Number (SN) 1310 and subsequent and
airplanes SN 1000 through 1309 having Aircraft Service Change
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-36-00
Page 3
October 11/02
Revision 8
(ASC) 313, the rate at which cabin pressure changes during rapid
power reductions at high altitudes is reduced. This ASC provides an
electrical circuit, routed through the 2500 FT AGL horn mute relay, to
reset bleed air pressure regulation from 18 psi to 30 psi when the
power levers are retarded. In a retarded power lever descent
(without anti-icing selected on) manifold pressure is maintained
above 20 psi. Selection of any anti-icing on disables this circuit.
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湾流4操作手册 Gulfstream IV Operating Manual 2(135)
