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two auxiliary hydraulic systems are the electrically-driven Auxiliary system and the
hydraulically-driven Utility system. When accordingly configured, both systems are
capable of automatic operation when certain conditions are satisfied. In addition, they
are capable of manual operation through use of associated control switches.
The Auxiliary and Utility hydraulic systems are described in the following subsections
within this section:
• 2A-29-31: Auxiliary Hydraulic System
Onboard Hydraulic Replenisher
Figure 11
OPERATING MANUAL
2A-29-00 PRODUCTION AIRCRAFT SYSTEMS
Page 24
October 11/02
Revision 8
• 2A-29-32: Utility Hydraulic System
2A-29-31: Auxiliary Hydraulic System
1. General Description:
The Auxiliary hydraulic system (Figure 12) receives pressure from an electrically
driven pump which draws fluid from the Auxiliary chamber of the Combined
hydraulic system reservoir. The pump provides 3000 psi for the operation of the
following systems:
• Wing Flaps
• Ground Spoiler Control Pressure
• Brakes
• Main Entrance Door (see below)
• Parking/Emergency Brakes (see below)
• Landing Gear and Landing Gear Doors (see below)
• Cargo Door (see below)
The Auxiliary hydraulic system functions independently as the only source of
hydraulic power for closing the main entrance door and charging the parking/
emergency brakes accumulator. In addition, the Auxiliary hydraulic system may be
used for ground operation of the landing gear and landing gear doors for
maintenance checks, through the use of a ground service valve.
On aircraft with Aircraft Service Change (ASC) 213 or ASC 354 incorporated, the
Auxiliary hydraulic system also serves as the only source of hydraulic power for
opening and closing the cargo door.
2. Description of Subsystems, Units and Components:
The Auxiliary hydraulic system consists of the following units and components:
A. Auxiliary Reservoir Chamber:
The Combined system reservoir contains two chambers separated by a
bulkhead; one chamber supplies the Combined and Utility systems, and
the other supplies the Auxiliary system. Total capacity of the reservoir is 5.5
gallons (20.8 liters) with an Auxiliary system working volume of 1.75
gallons (6.6 liters). Both chambers are full under normal operating
conditions. An opening at the top of the reservoir bulkhead allows fluid flow
from the Combined chamber to the Auxiliary chamber. Filling of both
chambers can be accomplished using either the fill connection on the
ground test panel (underside of the aircraft, just forward of the tail
compartment door) or a replenishing system (inside the tail compartment).
B. Shutoff Valve:
An electrically operated solenoid shutoff valve controls fluid flow to the
Auxiliary hydraulic pump. Controlled by the same circuits that operate the
Auxiliary hydraulic pump power relay, the shutoff valve receives 28V DC
power from the Essential DC bus through the AUX HYD PUMP circuit
breaker. When the Auxiliary hydraulic pump receives power, the shutoff
valve opens to allow hydraulic fluid from the Auxiliary chamber to the
Auxiliary pump.
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-29-00
Page 25
October 11/02
Revision 8
C. Auxiliary Hydraulic Pump:
The electrically driven Auxiliary hydraulic pump, commonly referred to as
the “Aux pump”, is installed on the aft side of the left main wheel well. It
consists of a fan-cooled 28V DC motor that drives a variable-delivery, axialpiston
type pump.
The Aux pump motor receives 28V DC from the Essential DC bus (via the
Battery Tie bus) through the Aux pump power relay. The power relay, in
turn, receives power from the Essential DC bus through the AUX HYD
PUMP circuit breaker.
When activated, the Aux pump motor initially draws a maximum of 750
amps, decreasing to 66-70 amps as the motor reaches operating speed. If
the motor continuously draws more then 80 amps, the Aux pump overload
sensor trips the AUX HYD PUMP circuit breaker. This de-energizes the Aux
pump power relay and the Aux pump stops.
A thermal switch is installed on the Aux pump case to monitor pump
temperature. If pump temperature reaches 300 ±10°F (149 ±6°C), the
thermal switch closes causing an amber AUXILIARY HYD HOT caution
message to be displayed on the Crew Alerting System (CAS).
D. Pressure Snubber and Transmitter:
A pressure snubber is installed upstream of the pressure transmitter to
damp any pressure surges in order to prevent erratic pressure indications.
The pressure transmitter receives 28V DC power from the Essential DC
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湾流4操作手册 Gulfstream IV Operating Manual 2(45)
