sure or auxiliary system pressure, provides hy-
draulic fluid to the landing gear and the flaps.
The crossflow valve is solenoid actuated, and
is normally deactivated, allowing main hy-
draulic system fluid to the gear and flaps.
Should main hydraulic system pressure be
lost, the pilot can open the hydraulic crossflow
valve by depressing the HYD XFLOW switch
located on the gear/hydraulic control panel
(Figure 13-2). When the valve is activated,
“ON” is annunciated within the switch. After
opening the crossflow valve, selecting the
AUX HYD pump switch “ON” allows auxil-
iary hydraulic system pressure to be supplied
to the landing gear, gear doors and flaps
(Figure 13-3).
Should the quantity level within the auxiliary
reservoir deplete to a LOW level, the hydraulic
crossflow valve is automatically closed, al-
lowing conservation of auxiliary fluid for the
airplane brake system. A CAS caution mes-
sage, “AUX HYD QTY LO” alerts the crew to
this condition.
The hydraulic crossflow valve is 28 VDC pow-
ered from the left essential bus. It is protected
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
13-8
FOR TRAINING PURPOSES ONLY
FlightSafety
international
CAS Message
Logic Summary
Type
Msg
C
C
A
A
C = Caution
A = Advisory
BRK ACUM PRESS
EMER brk acum pressure < 1,200 or > 3,600 psi.
MAIN HYD PRESS
Main hydraulic pressure < 1,500 or > 3,600 psi.
C
C
AUX HYD PMP LO
Aux hyd pump ON w/press < 1,900 psi.
AUX HYD QTY LO
Low aux hyd reservoir qty, inhibits HYD XFLOW.
MAIN HYDQTY LO
Main hydraulic fluid quantity low.
L R HYD PUMP LOW
L or R engine hydraulic pressure < 1,900 psi.
A
HYD XFLOW ON
Hydraulic Crossflow is open.
Table 13-1. HYDRAULIC SYSTEM CAS MESSAGE DATABASE
SAT
°
C
R
1750
FLAPS
20
6.5
PITCH TRIM
LBS
-15
50.0
80
60
1002
550
75.0
AUX HYD PMP LO
AUX HYD QTY LO
BRK ACUM PRESS
MAIN HYD PRESS
MAIN HYDQTY LO
L R HYD PUMP LOW
END
HYD XFLOW ON
Figure 13-5. Hydraulic System CAS
Messages on EICAS
