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in excess of 3700 psi (25,511 kPa).
Pilot’s Manual
3-2 PM-126A
FIREWALL SHUTOFF VALVES
Two motor-driven firewall shutoff valves can stop hydraulic fluid
flow to the main engine-driven hydraulic pumps in the event of an
emergency or engine fire. These valves will also shut off fuel supply
to the engine and close the engine bleed air valves. Each shutoff valve
is operated by the corresponding FIRE switch on the pedestal (ENGINE
panel). (Refer to Engine Fire Extinguishing System, Section II).
The valves operate on 28-vdc supplied through the 3-amp L and R
FWSOV circuit breakers located on the pilot’s and copilot’s circuit
breaker panels (ENGINE group), respectively. Loss of power causes
the shutoff valves to remain in their last position. The firewall shutoff
valves are powered from the hot bus.
SOURCE SELECTOR VALVE
A source selector valve controls the source (main or auxiliary) of hydraulic
pressure to the landing gear and flap systems. To initiate the hydraulic
cross flow function, the auxiliary hydraulic pump must be
running. This is achieved by pressing the AUX PUMP switch (GEAR/
HYD panel). Manual activation of the valve during flight is accomplished
by depressing the alternate-action push button HYD XFLOW
switch (GEAR/HYD panel) which connects the landing gear and flap
systems to the auxiliary hydraulic system. The switch will illuminate
ON to indicate the valve is energized. If the auxiliary fluid level becomes
low, the valve will automatically be deactivated in order to conserve
fluid for the brake system.
The following CAS illumination is specific to the source selector valve:
AUX HYD PUMP CONTROL
The auxiliary dc motor-driven hydraulic pump is automatically controlled
by landing gear position, and manually controlled by the momentary-
action push button AUX HYD switch (GEAR/HYD panel).
The ON legend will illuminate when the pump is activated either manually
or automatically. Normal auxiliary pump operation is based on
the following aircraft configurations:
(1) Pump off when aircraft is powered up.
(2) Manual control prior to gear retraction. AUX HYD
switch should be ON during normal taxi and takeoff.
(3) Automatically off when gear is transitioned up.
(4) Manual control in flight.
(5) Automatically ON when gear is transitioned down.
(6) Manual control after gear extension.
(7) Automatically off when aircraft is powered down.
CAS Color Description
HYD XFLOW ON White Hydraulic crossflow function is selected.
Pilot’s Manual
PM-126A 3-3
The auxiliary pump operates on 28-vdc supplied from the L ESS bus.
Power for the auxiliary pump is provided by the 1-amp PWR circuit
breaker located on the pilot’s circuit breaker panel (GEAR/HYDRAULICS
group [AUX HYD PUMP]). Power for the auxiliary pump control
circuit is provided by 2-amp CTRL circuit breaker located on the pilot’s
circuit breaker panel (GEAR/HYDRAULICS group [AUX HYD
PUMP]). Refer to Airplane Flight Manual for hydraulic pump
limitations.
The following CAS illumination is specific to the auxiliary hydraulic
pump:
MAIN/AUXILIARY SYSTEM PRESSURE
The HYD system page on EICAS contains a schematic display of fluid
flow in the main and auxiliary hydraulic systems. Main system pressure
is sensed by a pressure transducer which provides an analog signal
to the EICAS. Pressure is displayed as a digital readout on the HYD
system page with a range of 0 to 4000 psi (27,580 kPa) and a display resolution
of 10 psi (69 kPa). Low-pressure switches relay information to
CAS for low-pressure indications for the left or right side of the main
hydraulic system, or in the auxiliary system.
The following CAS illuminations are specific to hydraulic system
pressure:
CAS Color Description
AUX HYD PMP LO Amber Auxiliary hydraulic pump is on and pressure
is less than 1900 psi.
CAS Color Description
AUX HYD PMP LO Amber Auxiliary hydraulic pump is on and pressure
is less than 1900 psi.
MAIN HYD PRESS Amber Hydraulic pressure (main system) is not
within the acceptable range (either too high or
too low).
HYD PUMP LOW White Pressure from the associated (L or R)
engine-driven hydraulic pump is low.
Pilot’s Manual
3-4 PM-126A
BRAKE ACCUMULATOR PRESSURE
The brake accumulator provides reserve hydraulic pressure of 3000 psi
(20,685 kPa) for emergency brake operation and for parking brake operation.
The accumulator is designed to provide at least six emergency
brake applications or parking brake pressure for approximately 48
hours. The brake accumulator incorporates a pressure transducer
　
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