Hydraulic System - Use of Back Up Sources

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The hydraulic systemUse of back up power sources

Operational Liaison Meeting


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2The hydraulic system

Summary

Introduction

Why not use the back up power source in all

cases?

Use of PTU

Use of electrical pumps

Use of RAT

Conclusion


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SummaryIn this presentation,

A320 includes A319and A321.


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Introduction All models are fitted with 3 hydraulic systems.

Example: A340


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All models are fitted with 3 hydraulic systems.

Normal operation:

Each system is supplied by one or two engine

driven pump(s) (except blue system on A320 family).

ENG 1 ENG 2

Example: Green

system on A310

Introduction


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Introduction All models are fitted with 3 hydraulic systems.

Normal operation:

Each system is supplied by one or two engine

driven pump(s) (except blue system on A320 family).

Back up:

Each system has one or more back up power

source(s): PTU or RAT or electrical pump.


7/667The hydraulic system

If the normal power source fails In some cases the back up automatically takes

over.

Example:

Failure of the yellowengine driven pump

on A320:

The PTU takes over



If the normal power source fails In some cases, the procedure requests to

activate the back up manually

Example:

Failure of the

blue enginedriven pump on

A310:

The PTU is

manually selected

for approach



If the normal power source fails In some cases, the system is lost. No back up

is used:

Example:On A340, when the ENG 2 pump fails,

the blue system is lost.

The elecpump is

not used



If the normal power source fails When do we use the back up power source?

This depends on the type of back up:

PTU

electrical pump

or, RAT.



If the normal power source fails When do we use the back up power source?

This also depends on the type of failure:

loss of engine driven pump,

overheat,

reservoir low air pressure,

low level

..and on the number of circuits which are

affected.



Summary

Introduction


cases?

Use of PTU


Use of RAT

Conclusion

?



If the normal power source failsWhy notuse the back up power source in all

cases?

On all our models, due to the architecture of

our systems, a single hydraulic failure leadsonly to the loss of some redundancy.

All functions are available.

Therefore, single hydraulic failure is minor,

according to the certification criteria.



If the normal power source fails The objectives are:

keep the procedures as simple as possible,

keep the logics for automatic operation as

simple as possible,

avoid negative effects.



Why not use the back up power source? In case of single failure, all flight controls surfaces

(except some spoilers) remain available.

B GG Y

B Y

THS

Elevators

B

G

Y

Rudder

GY GBBG G Y

YY YY BBB BG GG G

Ailerons Ailerons

spoilers spoilers

Example:

A330/A340

B

G

Y

G

slats flaps


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In case of single failure, all flight controls surfaces


B GG Y

B Y

THS

Elevators

B

G

Y

Rudder

GY GBBG G Y

YY YY BBB BG GG G

Ailerons Ailerons

spoilers spoilers

Example:

A330/A340

Loss of Green

Why not use the back up power source?

B

G

Y

G

slats flaps


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B GG Y

B Y

THS

Elevators

B

G

Y

Rudder

GY GBBG G Y

YY YY BBB BG GG G

Ailerons Ailerons

spoilers spoilers

Example:

A330/A340

Loss of Blue


B

G

Y

G

slats flaps


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B GG Y

B Y

THS

Elevators

B

G

Y

Rudder

GY GBBG G Y

YY YY BBB BG GG G

Ailerons Ailerons

spoilers spoilers

Example:

A330/A340

Loss of Yellow


B

G

Y

G

slats flaps


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Flaps and slats remain available for approach.

The autopilot remains available.



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Summary

Introduction


cases?

Use of PTU Use of electrical pumps

Use of RAT

Conclusion


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When a PTU is available It automatically takes over.

Example:Failure of the yellow

engine driven pump


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Example:

On the opposite,

failure of the green

engine driven pump



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In some cases, the procedure requests to

select it off, to avoid damages.

These cases are: reservoir overheat

reservoir low air pressure, with pressure

fluctuations,

low level.In these two cases, the system

can be recovered for approach

through engine driven pumps.


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It covers the cases of

failure of the engine driven pump, or

engine failure.


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When a PTU is availableWhy does it automatically take over?

Its operation was necessary to avoid the loss of

one elevator in some cases of dual failure

(G+B orY+B). It was not necessary in case of single failure.

However, for simplification, the logic was based

on a single parameter:DP between yellow and green systems.

(so, it is also used in case of single failure)


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The procedure requests to select manually the

PTU for approach

In case of failure

of the blue

engine driven

pump on, or.

When a PTU is available


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The procedure requests to select manually the

PTU for approach

...in case of

failure of the

yellow engine

driven pump .



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As on A320, in case of reservoir overheat or

reservoir low air pressure, the system can be

recovered for approach through engine driven

pumps.

It is not recommended to select the PTU ON in

dual hydraulic failure, with green remaining.

This is to avoid to decrease the reliability of the

remaining green system.



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Summary

Introduction


cases?

Use of PTU


Use of RAT

Conclusion


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When an electrical pump is available

Example:On A340, when the ENG 2 pumpfails, the blue system is lost.

The elecpump is

not used


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When an electrical pump is available

Example:On A340, when the ENG 2 pumpfails, the blue system is lost.

The electrical pump is not used to replace the

engine driven pump.

This applies to all three circuits on A330 and

A340.


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Why not use the electrical pump?

A330/A340 engine

driven pump

delivers about 175 litersper minute

A330/A340 electrical

pump



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Required flow on green system A340

Available with eng pumps

TO climb cruise land

100

200

300

Flight controls

geargear

Flaps/slats

Flaps/slats

L/mindescent

Available with the elec pump


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TO climb cruise land

100

200

300

Flight controls

slats slats

Required flow on blue system A340

Available with eng pumps


descentL/min


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Why not use the electrical pump?Example: control of right outer aileron

In normal operations: P3 is in control

GY

P3S2


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Example: control of right outer aileron


GY

P3S2


In case of G failure on A330/A340:

S2 takes over.


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Example: control of right outer aileron


GY

P3S2

If the green pump is started: P3 takes over again.

If the demand exceeds the available flow, the greenpressure fluctuates around low press threshold.

Switchings between S2 and P3 will occur.

This induces some lateral jerks.

P3S2

P3S2P3S2


In case of G failure on A330/A340:

S2 takes over.


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In case of dual failure, some surfaces may be

lost.

B GG Y

B Y

THS

Elevators

B

G

Y

Rudder

GY GBBG G Y

YY YY BBB BG GG G

Ailerons Ailerons

spoilers spoilers

Example:A330/A340

G+Y failed

G

outer outer

right


B

G

Y

Gslats flaps


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Example:In case of G+Y failure:

The right outer aileron is lost

It moves to its zero hinge moment position

G GB Y



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G GB Y

If the green pressure is recovered through the elec pump: The right outer aileron is recoveredit comes back to normal position




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If the green pressure is recovered through the elec pump: The right outer aileron is recoveredit comes back to normal position

If flight control demand induces green pressure loss:The right outer aileron is lost againIt moves again to its zero hinge moment position

G GB Y




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The elec pump is not designed to replace the

engine driven pumps.

On A330/340, its flow is too low and the normal

use of flight controls leads to pressure drops(ECAM warning triggering, computer switchings

and, if two systems are affected, undesirable

surface movements).

It should not be started in flight, except in some

particular situations.



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When are the elec pumps used in flight? On the blue system, the electrical pump is the

normal power source.

The system is designed for that: the demand iscompatible with the delivered flow.

100


TO climb cruise landdescentL/min


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When are the elec pumps used in flight?

In case of dual failure, if the yellowsystem islost due to the failure of the engine driven

pump :

the procedurerequests to

select manually

the yellow

electrical pump.

(As on blue system, thedemand is compatible with

the flow.)


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On the green system, if the two engine drivenpumps are lost:

the two electricalpumps can be

manually started

for approach.


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When are the elec pumps used in flight? On A340, on green system:

ENG 1 ENG 4


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When are the elec pumps used in flight? On A340, on green system:

ENG 1 ENG 4

At take off, in case of

failure of ENG1 or 4, the

electrical pump is

automatically started for 25seconds at landing gear

retraction.

Then it stops.

Same on A330, when ENG 1 or 2 fails.


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When are the elec pumps used in flight? On A340, on yellowsystem:

ENG 3


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In case of single failure, for spoiler retraction, if

some of them remain extended at the time of

the failure.


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Summary

Introduction


cases?

Use of PTU Use of electrical pumps

Use of RAT

Conclusion


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When do we use the RAT ? The RAT enables to supply:

the yellow system on A300/A310

the blue system on A320 family

the green system on A330/A340.

It is used:

in case of all engine flame out (it is the only

hydraulic source)

in case of dual hydraulic failures.

Use of RAT depends on the failure


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affecting the related system Overheat or

reservoir lowair pressure.

Loss of the

normal power

supply.

Reservoir lowlevel

Do not use the

RAT.

The RAT canbe used.

(system recovered for approach

through normal pump)

On A320:Do not use

the RAT.

On other aircraft:

The RAT can be used.(dedicated fluid reserve)


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When do we use the RAT ?Dual hydraulic failure:

(G+BorB+Y)

RAT MAN ON

is displayed if the bluesystem is lost due to ELEC PUMPLO PR


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(G+Y or B+Y)

RAT MAN ON

is recommended if the yellow engine driven pump is

failed.

It is recommended only for approach in case ofyellow

system low level.


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(G+B)

Only in case of dual low level:

The RAT is automatically extended.RAT MAN ON

is displayed for confirmation.

Why?

This is to cover the case of an engine burst

affecting all the hydraulic circuits.


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(G+B orG+Y)

Only in case of dual low level:

The RAT is automatically extended.RAT MAN ON

is displayed for confirmation.

Why?

This is to cover the case of an engine burst

affecting all the hydraulic circuits.


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When do we use the RAT ?

Dual hydraulic failure:(G+B orG+Y)

In addition, with new FWC standard (K3.2):

CONSIDER RAT MAN USE

is displayed (except in case ofgreen overheat or dual low

level).

Why?

This enables to recover the use of flaps or slats.


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When do we use the RAT ?

A330/A340 engine

driven pump


A330/A340 RAT

delivers about 80 liters

per minute at 175 kt.

Below this speed, the

flow is reduced.


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When do we use the RAT ? When the RAT is used, to keep the hydraulic

flow demand consistent with the RATperformance:

a rate limitation is introduced:

on the green surfaces on A330/340

on blue surfaces on A320 (not on A319 or A321)


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ConclusionSingle failure:

Automatic operation of PTU (Y orG).

Dual failure:

Manual use ofYellow electrical pump.

Manual use ofRAT.


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Manual use ofgreen electrical pumps for

approach only

manual use of PTUs (B orY) for approach only

Dual failure:

Manual use ofRAT.

Manual use ofgreen electrical pump.


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No permanent use of back up power sources.

Dual failure:.

Automatic use ofRAT in a particular case.

In other cases, no permanent use of back up

power sources.


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No permanent use of back up power sources.

Dual failure:.

Automatic or manual use ofRAT.


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ConclusionIn case of dual failure:

the back up power source is used

provided the failure enables its use (Ex: not incase of overheat)

provided its use is convenient (Ex: nopermanent use of electrical pump on A330/340)


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ConclusionIn case of single failure:

the back up power source is

sometimes used, but

never necessary to maintain the normaloperations.

Documents

Hydraulic System - Use of Back Up Sources