b777 hydraulics

7/27/2019 B777 Hydraulics

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B777

HydraulicsDO NOT USE FOR FLIGHT



Hydraulic 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 than1500 psi.

PRI

MARY

L ENG

L ELEC

RAM AIR

TURBINE

PRESS

UNLKD

ON

ON ON

ON

FAULTFAULT

FAULT

FAULTFAULT

FAULT

FAULT FAULT

AUTO

OFF ON

AUTO

OFF ON

OFF ON

AUTO

OFF ON

AUTO

R ELEC

HYDRAULIC

C2ELECC1

R ENG

PRI

MARY

C2AIRC1

DEMAND

DEMAND

OVERHEAD PANEL

7

6

5

4

1

2

3

8

Boeing B777 - Systems Summary [Hydraulics]

Page 1



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



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 onthe display select panel.

Status Display

1 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 inflight).

PRESSURE – displays hydraulic pressure in pounds per square inch of the pump

with the highest pressure.

PRESS

RF

L RC

QTY 0.91

3100

0.72

3000

0.10

2900

HYDRAULIC

LO

MULTIFUNCTION DISPLAY1


Page 3



Hydraulic Synoptic Display

FLT CTRL

L REVNOSE GEAR

& STEERING FLT CTRL

R REV

NORM BRKS

FLT CTRL

MAIN GEAR

& STEERING

FLAPS

ALTN/RSV

BRAKES

P

R

I

M

AR

Y

D

E

M

A

N

D

P

R

I

M

AR

Y

D

E

M

A

N

D

ENG

ELECELEC

SOVSOV

ENG

ELEC ELEC

AIR AIR

RAT

PRESSPRESS3100 30002900

0.10 LO RF0.72

RL

L

OVHT

R

ISLN ISLN

C1 C2

C1 C2

0.91

MULTIFUNCTION DISPLAY

AIR – air–driven pumpELEC – electric–driven pumpENG – engine–driven pump

ISLN – isolation valveLO – reservoir quantity lowOF – reservoir quantity over–fullOVHT – pump overheat indication

RAT – ram air turbine pumpRF – reservoir requires refillingSOV – shutoff valve

Closed valve – Failed pump –


Page 4



Miscellaneous Hydraulic System Controls

Engine Fire Panel

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.

DISCH DISCH

1 12 2

LEFT

RI

GHT

ENG BTL

1 DISCH

ENG BTL

2 DISCH

AFT AISLE STAND

1


Page 5



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.

FLT CONTROL HYD POWERL

VALVE

CLOSED

VALVE

CLOSED

VALVE

CLOSED

C RTAIL

NORM

SHUT

OFF

NORM

SHUT

OFF

VALVE

CLOSED

VALVE

CLOSED

VALVE

CLOSED

NORM

SHUT

OFF

NORM

SHUT

OFF

WING

OVERHEAD MAINTENANCE PANEL

1

2


Page 6



Introduction

The airplane has three independent hydraulic systems: left, right, and center. The

hydraulic systems power the:

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 systemreservoir. 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.

• flight controls

• leading edge slats

• trailing edge flaps

• landing gear

• wheel brakes

• nose and main gear steering

• thrust reversers.


Page 7



Center Hydraulic System

The center hydraulic system powers:

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.

• flight controls• leading edge slats

• trailing edge flaps

• landing gear actuation

• alternate brakes• reserve brakes

• nose gear steering

• main gear steering.


Page 8



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 ONresults 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 brakesand 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 than30 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 bothengine–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.


Page 9



Hydraulic Systems Schematic

PRIMARY

L ENG

L ELEC AUTO

OFF ON

AUTO

OFF ON

OFF ON

AUTO

OFF ON

AUTO

R ELEC

HYDRAULIC

C2ELECC1

R ENG

PRIMARY

C2AIRC1

D

EMAND

D

EMAND

ON

ON ON

ON

L

E

F

T

DISCH

21

FLT CTRL

L REVNOSE GEAR

& STEERING FLT CTRL

R REV

NORM BRKS

FLT CTRL

MAIN GEAR

FLAPS

ALTN/RSV

BRAKES

P

R

IM

A

R

Y

D

E

M

A

N

D

P

R

IM

A

R

Y

D

E

M

A

N

D

ENG

ELECELEC

SOVSOV

LEFT CENTER RIGHT

ENG

ELEC ELEC

AIR AIR

RAT

L

L

ISLN ISLN

C1 C2

C1 C2

R

R

RESERVOIR RESERVOIR RESERVOIR

& STEERING

RAM AIR

TURBINE

ISLN

SOVPump Isolationvalve

Shutoff valve


Page 10



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 PRIL, 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.


Page 11



[AIMS BP2005]

Message Level Aural Condition

HYD PRESS SYS

R+C

Caution Beeper Right and center hydraulic system

pressures are low.

HYD QTY LOW C Advisory Center hydraulic system quantity is low.

HYD QTY LOW

L, R

Advisory Hydraulic quantity is low.

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.


Page 12

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