ing gear and flaps by selecting HYD XFLOW
on. It can also provide hydraulic pressure for
brake operation if the main system has failed.
The hydraulic system ground service panel
(GSP) is located on the right side of the fuse-
lage, just aft of the wing trailing edge. The GSP
provides for system servicing, monitoring hy-
draulic system status and contains the ground
servicing valve switch.
MAJOR HYDRAULIC
SYSTEM COMPONENTS
RESERVOIR
The hydraulic reservoir, located forward and
above the tailcone baggage compartment
,
is
serviced through a fill port on the GSP.
Divided into two separate sections, one side
of the reservoir supplies hydraulic fluid to
the engine driven hydraulic pumps for the
main system, and the other side supplies fluid
to the DC motor-driven hydraulic pump for the
auxiliary hydraulic system. The reservoir
holds approximately 7.3 qt. when full. See
Figure 13-1.
The reservoir is pressurized with engine bleed
air regulated to approximately 24 psi. An over-
board relief valve vents excess pressure at ap-
proximately 26.5 psi and provides a vacuum
relief by admitting outside ambient air.
A reservoir fluid level sensor is located on
the auxiliary side of the reservoir (Figure 13-
1). The sensor measures four independent
fluid levels which correspond to the overfull,
reservoir full, add fluid, and auxiliary fluid low
positions on the sensor.
A white “MAIN HYDQTY LO” advisory
CAS message is generated if the reservoir sen-
sor detects fluid at or below the “add fluid” po-
sition (5.8 qt.).
Additionally, if the reservoir quantity sensor
detects low auxiliary fluid, an amber “AUX
HYD QTY LO” caution message (with mas-
ter caution lights and chime) will be displayed
(1.2 qt.). When the sensor detects auxiliary
fluid low, “LOW” is also annunciated on the
EICAS/MFD hydraulic system schematic
(Figure 13-6) and the hydraulic crossflow
valve will close (if open), isolating the auxil-
iary system for brake operation only.
The overfull, full and add positions on the
fluid level sensor provide signals to indicators
on the ground service panel (Figure 13-8),
while the add fluid and auxiliary fluid low
positions on the sensor provide information to
the crew through the EICAS/MFD.
SHUTOFF VALVES
Electrically controlled and motor-driven hy-
draulic shutoff valves are installed in the sup-
ply line to each engine-driven hydraulic pump.
The shutoff valves are activated closed/open
via the engine FIRE PUSH buttons located on
the engine/fuel control panel (center pedestal).
This pushbutton also closes the engine bleed
air valves and shuts off the fuel supply to each
engine. The left and right shutoff valves receive
28 VDC power from the left and right emer-
gency hot busses. The valves are protected by
circuit breakers labeled FWSOV (firewall
shutoff valve) located within the ENGINE
group on the respective left and right circuit
breaker panels.
PUMPS
Engine-Driven Pumps
Variable-volume, constant pressure pumps,
installed on the accessory drive of each engine
supply pressure to the hydraulic system. Each
pump regulates the pressure by changing the
volumetric output as system demands vary.
For example, if the hydraulic pressure de-
creases, then pump output increases to main-
tain balanced system pressure. Conversely,
when hydraulic pressure increases, pump out-
put decreases. The maximum output of each
engine-driven pump is approximately 4.6 gal-
lons per minute.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
13-3
FOR TRAINING PURPOSES ONLY
FlightSafety
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