B777 Hydraulics
DO NOT USE FOR FLIGHT
Boeing B777 - Systems Summary [Hydraulics]
Hydraulic Panel
1
RAM AIR
TURBINE
2
PRESS
3
UNLKD
HYDRAULIC
4
P
R
I
M
A
R
Y
ELEC
C1
L ENG
ON
5
C2
ON
ON
FAULT
FAULT
R ENG
ON
FAULT
L ELEC
AUTO
ON
D OFF
E
M
A
N
D
FAULT
P
R
I
M
A
R
Y
FAULT
C1
OFF
AIR
AUTO
ON
OFF
FAULT
C2
AUTO
FAULT
6
R ELEC
ON
OFF
AUTO
ON D
E
M
A
N
D
FAULT
OVERHEAD PANEL
1
RAM AIR TURBINE Switch
Push – deploys the RAT.
2
Ram Air Turbine Pressure (PRESS) Light
Illuminated (green) –
• the RAT is deployed
• center system primary flight control hydraulic pressure is greater than
1500 psi.
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7
8
Boeing B777 - Systems Summary [Hydraulics]
3
Ram Air Turbine Unlocked (UNLKD) Light
Illuminated (amber) – the RAT is not in the stowed position.
4
Left/Right Engine (L/R ENG) PRIMARY Pump Switches
ON – the engine–driven hydraulic pump pressurizes the related left or right
hydraulic system when the engine rotates.
Off (ON not visible) – the engine–driven hydraulic pump is turned off and
depressurized.
5
C1/C2 Electrical (C1/C2 ELEC) PRIMARY Pump Switches
ON –
• the electric motor–driven hydraulic pump operates
• pressurizes the center hydraulic system.
Off (ON not visible) – the electric motor–driven hydraulic pump is turned off.
6
Primary Pump FAULT Lights
Illuminated (amber) –
• low primary pump pressure
• excessive primary pump fluid temperature, or
• pump selected OFF.
7
DEMAND Pump Selectors
ON – the pump runs continuously.
AUTO – the pump operates when system and/or primary pump(s) pressure is low,
or when control logic anticipates a large system demand.
OFF – the pump is off.
Note: If both air–driven pumps are selected to ON, only air–driven pump C1
operates; the two air–driven pumps cannot operate simultaneously when
both are selected ON.
8
Demand Pump FAULT Lights
Illuminated (amber) –
• low demand pump output pressure
• excessive demand pump fluid temperature, or
• demand pump is selected OFF.
Page 2
Boeing B777 - Systems Summary [Hydraulics]
Hydraulic System Indications
To view the status display, push the STAT display switch on the display select
panel. To view the hydraulic synoptic, push the HYD synoptic display switch on
the display select panel.
Status Display
HYDRAULIC
L
QTY
PRESS
1
1
C
0.10 LO
2900
0.91
3100
R
0.72 RF
3000
MULTIFUNCTION DISPLAY
Hydraulic Display
QTY –
• displays system reservoir quantity as a percentage of the normal service
level (1.00 is the normal service level)
• LO (amber) – displayed when the reservoir quantity is low
• OF (white) – displayed when the reservoir is over–full (inhibited in flight)
• RF (white) – displayed when the reservoir requires refilling (inhibited in
flight).
PRESSURE – displays hydraulic pressure in pounds per square inch of the pump
with the highest pressure.
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Boeing B777 - Systems Summary [Hydraulics]
Hydraulic Synoptic Display
L REV
FLT CTRL
NOSE GEAR
& STEERING
ISLN
L
ENG
L
ELEC
SOV
P
R
I
M
A
R
Y
ALTN/RSV
BRAKES
MAIN GEAR
& STEERING
R REV
FLT CTRL
FLT CTRL
ISLN
ELEC
C1
P
R
I
M
A
R
Y
ELEC
C2
AIR
C2
AIR
C1
RAT
D
E
M
A
N
D
D
E
M
A
N
D
PRESS
2900
OVHT
R
ENG
R
ELEC
SOV
0.72 RF
0.91
0.10 LO
3100
NORM BRKS
FLAPS
PRESS
3000
MULTIFUNCTION DISPLAY
AIR – air–driven pump
ELEC – electric–driven pump
ENG – engine–driven pump
ISLN – isolation valve
LO – reservoir quantity low
OF – reservoir quantity over–full
OVHT – pump overheat indication
Page 4
RAT – ram air turbine pump
RF – reservoir requires refilling
SOV – shutoff valve
Closed valve –
Failed pump –
Boeing B777 - Systems Summary [Hydraulics]
Miscellaneous Hydraulic System Controls
Engine Fire Panel
ENG BTL
1 DISCH
ENG BTL
2 DISCH
DISCH
1
1
DISCH
2
1
L
E
F
T
R
I
G
H
T
2
AFT AISLE STAND
1
Engine Fire Switches
Pull –
• closes the engine–driven pump hydraulic supply shutoff valve
• depressurizes the engine–driven pump.
Flight Control Hydraulic Power Switches
Note: No flight crew normal or non–normal procedures require operation of the
flight control shutoff switches. These switches are for ground maintenance
use only.
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Boeing B777 - Systems Summary [Hydraulics]
FLT CONTROL HYD POWER
L
1
2
C
TAIL
R
NORM
NORM
SHUT
OFF
SHUT
OFF
VALVE
CLOSED
VALVE
CLOSED
VALVE
CLOSED
WING
VALVE
CLOSED
NORM
NORM
SHUT
OFF
SHUT
OFF
VALVE
CLOSED
VALVE
CLOSED
OVERHEAD MAINTENANCE PANEL
1
Flight Control Hydraulic Power Shutoff Switches
NORM – hydraulic system power is available to the flight control actuators.
SHUT OFF – hydraulic system power to the flight control actuators is shut off.
Note: In flight, the center system flight control shut off valves are isolated from
electrical power and cannot be closed.
2
Flight Control Hydraulic Power VALVE CLOSED Lights
Illuminated (amber) – the related valve is closed.
Page 6
Boeing B777 - Systems Summary [Hydraulics]
Introduction
The airplane has three independent hydraulic systems: left, right, and center. The
hydraulic systems power the:
• wheel brakes
• flight controls
• nose and main gear steering
• leading edge slats
• thrust reversers.
• trailing edge flaps
• landing gear
Flight control system components are distributed so that any one hydraulic system
can provide adequate airplane controllability.
Hydraulic fluid is supplied to each hydraulic pump from the associated system
reservoir. The reservoirs are pressurized by the bleed air system.
Left and Right Hydraulic Systems
The left and right hydraulic systems are identical. They differ only in the
components they power.
The left hydraulic system powers:
• flight controls
• the left engine thrust reverser.
The right hydraulic system powers:
• flight controls
• normal brakes
• the right thrust reverser.
Left and Right Hydraulic System Primary Pumps
The left and right hydraulic systems each have a primary pump. The left and right
primary pumps are engine–driven by the related left and right engines.
Left and Right Hydraulic System Demand Pumps
The left and right hydraulic systems each have a demand pump. The demand
pumps are electric motor–driven. The demand pumps provide supplementary
hydraulic power for periods of high system demand. The demand pumps also
provide a backup hydraulic power source for the engine–driven primary pumps.
The pumps are controlled by the DEMAND L and R pump selectors. In the AUTO
position, the L and R demand pumps operate for takeoff, landing, and when
system or primary pump pressure is low. In the ON position, the demand pump
runs continuously.
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Boeing B777 - Systems Summary [Hydraulics]
Center Hydraulic System
The center hydraulic system powers:
• flight controls
• leading edge slats
• trailing edge flaps
• landing gear actuation
•
•
•
•
alternate brakes
reserve brakes
nose gear steering
main gear steering.
The ram air turbine (RAT) can provide hydraulic power to the center hydraulic
system primary flight control components only.
Center Hydraulic System Primary Pumps
Two electric motor–driven primary pumps are the primary hydraulic power
sources for the center hydraulic system. The PRIMARY C1 and C2 pump
switches control pump operation.
On the ground:
With only a single ground power source, including the APU, the C2 pump will not
run if the C1 pump is selected. The pump will not be load shed if one engine
generator is operating, or the following sources are operating:
• primary external power and secondary external power
or
• APU generator and primary external power.
In flight:
The C2 pump may be load shed by the electrical load management system when
the following conditions exist:
• all other electric pumps are running
• there is a single source of electrical power
• generator capacity is exceeded.
The pump will start automatically when the conditions that shed the pump no
longer exist.
Center Hydraulic System Demand Pumps
The center hydraulic system has two air–driven demand pumps. The demand
pumps provide supplementary hydraulic power for periods of high system
demand. The demand pumps also provide a backup hydraulic power source for the
center system electric motor–driven primary pumps.
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Boeing B777 - Systems Summary [Hydraulics]
The pumps are controlled by the DEMAND C1 and C2 pump selectors. In the
AUTO position, a demand pump operates when system and/or primary pumps
pressure is low, or when system logic anticipates a large demand. In the ON
position, the demand pump runs continuously. Selecting both demand pumps ON
results in only pump C1 operating. Both pumps cannot operate simultaneously
when ON is selected for both pumps.
Center Hydraulic System Non–Normal Operation
If center hydraulic system quantity is sensed to be low and airspeed is greater than
60 knots the:
• reserve brakes are isolated from the center system and remain operable
(the C1 pump and reserve fluid are dedicated to operating reserve brakes
and nose gear steering)
• nose gear actuation and steering are isolated
• leading edge slats are isolated and not allowed to operate in the primary
(hydraulic) mode.
The leading edge slats are reconnected to the center hydraulic system and allowed
to operate in primary mode when:
• center hydraulic fluid quantity recovers to normal for 5 seconds, and
• the system determines that both engines have been running for more than
30 seconds.
Nose gear actuation and steering are reconnected when:
• airspeed decreases below 60 knots, or
• hydraulic pressure to the center system flight controls goes low, or
• the landing gear is selected down, both engines are normal, and both
engine–driven pumps are providing pressure.
Ram Air Turbine (RAT)
The RAT, when deployed, provides hydraulic power only to the primary flight
control components connected to the center hydraulic system. The RAT provides
hydraulic and electrical power throughout the flight envelope. In flight, the RAT
deploys automatically if:
• both engines are failed and center system pressure is low, or
• both AC transfer busses are unpowered, or
• all three hydraulic system pressures are low.
The RAT can be deployed manually by pushing the RAM AIR TURBINE switch.
The hot battery or APU battery bus must be powered. The center hydraulic system
does not need to be powered. The RAT is deployed by a compressed spring. Once
deployed, the RAT cannot be stowed in flight.
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Boeing B777 - Systems Summary [Hydraulics]
Hydraulic Systems Schematic
RAM AIR
TURBINE
HYDRAULIC
P
R
I
M
A
R
Y
ELEC
C1
L ENG
ON
ON
C1
OFF
L REV
FLT CTRL
AIR
AUTO
ON
NOSE GEAR
& STEERING
L
ENG
L
ELEC
DISCH
2
OFF
C2
AUTO
ON
OFF
R ELEC
AUTO
ON D
E
M
A
N
D
NORM BRKS
FLAPS
ISLN
L
E
F
T
R ENG
ON
ON
L ELEC
AUTO
OFF
ON
D
E
M
A
N
D
1
P
R
I
M
A
R
Y
C2
SOV
MAIN GEAR
& STEERING
ALTN/RSV
BRAKES
R REV
FLT CTRL
FLT CTRL
ISLN
P
R
I
M
A
R
Y
ELEC
C1
P
R
I
M
A
R
Y
ELEC
C2
AIR
C2
AIR
C1
D
E
M
A
N
D
RAT
D
E
M
A
N
D
R
ENG
R
ELEC
SOV
LEFT
CENTER
RIGHT
RESERVOIR
RESERVOIR
RESERVOIR
Pump
ISLN
Isolation
valve
Page 10
SOV
Shutoff
valve
Boeing B777 - Systems Summary [Hydraulics]
Hydraulics, Ram Air Turbine EICAS Messages
The following EICAS messages can be displayed.
Message
Level
Aural
Condition
HYD AUTO
CONTROL C
Advisory
Both center demand pump AUTO
functions and all center hydraulic system
indications are inoperative.
HYD AUTO
CONTROL L, R
Advisory
Demand pump AUTO function and all left
or right system indications are inoperative.
HYD OVERHEAT
DEM C1, C2, L, R
Advisory
Demand pump temperature is high.
HYD OVERHEAT
PRI C1, C2, L, R
Advisory
Primary pump temperature is high.
HYD PRESS DEM
C1, C2, L, R
Advisory
Demand pump output pressure is low
when commanded on.
HYD PRESS PRI
C1, C2
Advisory
Primary pump output pressure is low.
HYD PRESS PRI
L, R
Advisory
Primary pump output pressure is low.
HYD PRESS SYS
C
Caution
Beeper
Center hydraulic system pressure is low.
HYD PRESS SYS
L
Caution
Beeper
Left hydraulic system pressure is low.
HYD PRESS SYS
L+C
Caution
Beeper
Left and center hydraulic system pressures
are low.
HYD PRESS SYS
L+C+R
Caution
Beeper
All hydraulic system pressures are low.
HYD PRESS SYS
L+R
Caution
Beeper
Left and right hydraulic system pressures
are low.
HYD PRESS SYS
R
Caution
Beeper
Right hydraulic system pressure is low.
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Boeing B777 - Systems Summary [Hydraulics]
Message
HYD PRESS SYS
R+C
Level
Aural
Caution
Beeper
Condition
Right and center hydraulic system
pressures are low.
HYD QTY LOW C Advisory
Center hydraulic system quantity is low.
HYD QTY LOW
L, R
Hydraulic quantity is low.
Advisory
[AIMS BP2005]
HYD QTY LOW
L+C
Caution
Beeper
Left and center hydraulic system quantities
are low.
HYD QTY LOW
L+C+R
Caution
Beeper
All three hydraulic system quantities are
low.
HYD QTY LOW
L+R
Caution
Beeper
Left and right system quantities are low.
HYD QTY LOW
R+C
Caution
Beeper
Right and center system quantities are low.
RAT UNLOCKED
Advisory
RAT is not stowed and locked.
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