by a circuit breaker labeled “MAIN HYD
PRESS” on the pilot circuit breaker panel,
within the GEAR/HYDRAULICS group.
HYDRAULIC SYSTEM
OPERATION
MAIN SYSTEM
The engine-driven hydraulic pumps supply
fluid pressurized to 3,000 psi to the main fil-
ter manifold. Main system pressure is then
available to power the thrust reversers, spoil-
ers/spoilerons, the inboard and outboard brake
systems, and is supplied to the landing gear
control valve module for gear extension/re-
traction and flap operation.
AUXILIARY SYSTEM
When selected, manually or automatically,
auxiliary hydraulic pressure is provided via the
DC motor-driven auxiliary pump to the aux-
iliary filter manifold. Auxiliary hydraulic sys-
tem pressure is then available to the brake
system, and available to the landing gear con-
trol valve module, acting as a backup power
source, should main system pressure mal-
function. Selecting the HYD XFLOW S/I to
ON makes the auxiliary pump pressure avail-
able for gear and flap operation. Auxiliary
hydraulic pressure also recharges the airplane
brake accumulator (Figure 13-3).
HYDRAULIC SYSTEM
INDICATIONS
NORMAL OPERATION
Main hydraulic system pressure and brake ac-
cumulator pressure are displayed as digital
r e a d o u t s o n t h e S U M RY p a g e o f t h e
EICAS/MFD and also on the HYD system
schematic page. MAIN and B-ACUM pres-
sures are displayed in white digits when they
are within the normal range. Normal pressure
with an engine driven pump operating is 2,210
to 3,600 psi. If the main hydraulic pressure de-
creases to below 1,500 psi or increases to
above 3,600 psi, the digits turn amber and are
enclosed with an amber box. If the brake ac-
cumulator (B-ACUM) decreases below 1,200
psi or increases above 3,600 psi, the digits
turn amber and are enclosed in an amber box
(Table 13-2).
The HYD system schematic (Figure 13-6) can
also be selected for display at the bottom of the
E I C A S o r t h e M F D ( F i g u r e 1 3 - 4 ) . T h i s
schematic presents both a graphic and a digi-
tal display of system pressures, quantities and
m a l f u n c t i o n a l e r t i n g . T h e H Y D s y s t e m
schematic has a digital readout of main hy-
draulic system pressure, and a digital and ana-
log indicator of brake accumulator pressure.
These indications also change color when the
operating limits in Table 13-2 are exceeded in
the same manner as on the SUMRY display. The
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
13-9
FOR TRAINING PURPOSES ONLY
FlightSafety
international
Table 13-2. HYDRAULIC DIGITAL PRESSURE INDICATIONS
(SUMRY and HYD System Schematic)
AMBER
WHITE
AMBER
MAIN HYD
PSI
B-ACUM
PSI
< 1,500
> 3,600
1,500 – 3,600
< 1,200
> 3,600
1,200 – 3,600