Hydraulic System - Use of Back Up Sources

Operational Liaison Meeting 

 Introduction

power source in all  Why not use the back up power cases?  Use of PTU  Use of electrical pumps  Use of RAT  Conclusion

 Introduction

power source in all  Why not use the back up power cases?  Use of PTU  Use of electrical pumps  Use of RAT  Conclusion

In this presentation, A320 includes A319 and A321.

  All models are fitted with 3 hydraulic systems.

Example: A340 

  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). Example: Green system on A310  ENG 1

ENG 2

  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.

 In some cases the back up automatically takes

over. Example: Failure of the yellow  engine driven pump on A320: The PTU takes over 

 In some cases, the procedure requests to

activate the back up manually Example: Failure of the blue engine driven pump on  A310: The PTU is manually selected  for approach

 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 elec pump is not used

 When do we use the back up power source?  This depends on the type of back up:  –

PTU

 –

electrical pump

 –

or, RAT.

 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.

 Introduction

?

 Why not use the back up power source in all

cases?  Use of PTU  Use of electrical pumps  Use of RAT  Conclusion

W h y n o t  use the back up power source in all

cases?  On all our models, due to the architecture of 

our systems, a single hydraulic failure leads only to the loss of some redundancy.  All functions are available.  Therefore, single hydraulic failure is

according to the certification criteria.

minor,

 The objectives are:  keep the procedures as simple as possible,  keep the logics for automatic operation as

simple as possible,  avoid negative effects.

 In case of single failure, all flight controls surfaces

(except some spoilers) remain available. spoilers

spoilers Y Y G

G G

Y

B

B

G

B B

B

Y

G

G

 Ailerons Example:  A330/A340 

G

Y

B

B

G

Y

G

Ailerons

THS slats

B

Y

G

Y

flaps

B G

B

G

G

Elevators

Y

Y

Rudder 

 In case of single failure, all flight controls surfaces

(except some spoilers) remain available. spoilers

spoilers Y Y G

G G

Y

B

B

G

G

B B

B

G

G

 Ailerons slats

Y

B

G

B

Y Y

G

Ailerons

THS B

Example:  A330/A340  Loss of Green

Y

G

Y

flaps

B G

B

G

G

Elevators

Y

Y

Rudder 

 In case of single failure, all flight controls surfaces

(except some spoilers) remain available. spoilers

spoilers Y Y G

G G

Y

B

B

G

G

B B

B

G

G

 Ailerons slats

Y

B

G

B

Y Y

G

Ailerons

THS B

Example:  A330/A340  Loss of Blue

Y

G

Y

flaps

B G

B

G

G

Elevators

Y

Y

Rudder 

 In case of single failure, all flight controls surfaces

(except some spoilers) remain available. spoilers

spoilers Y Y G

G G

Y

B

B

G

G

B B

B

G

G

 Ailerons slats

Y

B

G

B

Y Y

G

Ailerons

THS B

Example:  A330/A340  Loss of Yellow 

Y

G

Y

flaps

B G

B

G

G

Elevators

Y

Y

Rudder 

 In case of single failure, all flight controls surfaces

(except some spoilers) remain available.  Flaps and slats remain available for approach.  The autopilot remains available.

 Introduction  Why not use the back up power source in all

cases?

Use of PTU  Use of electrical pumps  Use of RAT  Conclusion

 It automatically takes over.

Example: Failure of the yellow  engine driven pump

 It automatically takes over.

Example: On the opposite, failure of the green engine driven pump

 It automatically takes over.  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.

 It automatically takes over.

 It covers the cases of  failure of the engine driven pump, or  engine failure.

Why does it automatically take over?  Its operation was necessary to avoid the loss of 

one elevator in some cases of dual failure (G+B or  or Y Y+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)

 The procedure requests to select manually the

PTU for approach

In case of failure of the blue engine driven  pump on, or….

 The procedure requests to select manually the

PTU for approach

...in case of  failure of the yellow engine driven pump .

  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.

 Introduction  Why not use the back up power source in all

cases?  Use of PTU  Use of electrical pumps  Use of RAT  Conclusion

 Example:On A340, when the ENG 2 pump

fails, the blue system is lost.

The elec pump is not used

 Example:On A340, when the ENG 2 pump

fails, 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.

A330/A340 engine driven pump delivers about 175 liters per minute

A330/A340 electrical pump delivers about 35 liters per minute

TO

L/min

climb

cruise

descent

land

 Available with eng pumps

300

200

100

gear 

Flaps/ slats

Flaps/ slats

gear 

Flight controls  Available with the elec pump

TO

L/min

climb

cruise

descent

land

300

200

 Available with eng pumps

100

slats

slats

Flight controls  Available with the elec pump

Example: control of right outer aileron Y

 In normal operations: P3 is in control

G

S2 P3

Example: control of right outer aileron Y

 In normal operations: P3 is in control  In case of G failure on A330/A340:

S2 takes over.

G

S2 P3

Example: control of right outer aileron Y

 In normal operations: P3 is in control  In case of G failure on A330/A340:

S2 takes over.

S2 S2 S2 S2

G

P3 P3 P3 P3

 If the green pump is started: P3 takes over again.  If the demand exceeds the available flow, the green

pressure fluctuates around low press threshold.  Switchings between S2 and P3 will occur.

This induces some lateral jerks.

 In case of dual failure, some surfaces may be

lost. spoilers

spoilers Y Y G

G G

Y

B

B

G

G

B B

B

G

G

outer  Ailerons slats

Y

B

G

B

Y Y

Ailerons

THS B

Example:  A330/A340  G+Y failed 

Y

flaps

G

Y

G

outer  B G

B

G

G

Elevators

Y

right

Y

Rudder 

 Example:In case of G+Y failure: G

B

The right outer aileron is lost It moves to its zero hinge moment position

Y

G

 Example:In case of G+Y failure: G

B

Y

The right outer aileron is lost It moves to its zero hinge moment position If the green pressure is recovered through the elec pump:  The right outer aileron is recovered it comes back to normal position

G

 Example:In case of G+Y failure: G

B

Y

The right outer aileron is lost It moves to its zero hinge moment position If the green pressure is recovered through the elec pump:  The right outer aileron is recovered it comes back to normal position If flight control demand induces green pressure loss: The right outer aileron is lost again It moves again to its zero hinge moment position

G

 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.

 On the blue system, the electrical pump is the

normal power source. The system is designed for that: the demand is compatible with the delivered flow.

L/min

TO

climb

cruise

descent

land

100

 Available with the elec pump

 In case of dual failure, if the yellow system is

lost due to the failure of the engine driven pump : the procedure requests to select manually the yellow electrical pump. ( As on blue system, the demand is compatible with the flow.)

 On the green system, if the two engine driven

pumps are lost:

the two electrical pumps can be manually started for approach.

 On A340, on green system:

ENG 1

ENG 4

 On A340, on green system:  At take off , in case of 

ENG 1

ENG 4

failure of ENG1 or 4, the electrical pump is automatically started for 25 seconds at landing gear  retraction.  Then it stops.

 Same on A330, when ENG 1 or 2 fails.

 On A340, on yellow system:

ENG 3

 On

, on yellow system:  At take off , in case of failure of 

ENG 3

ENG 3, the electrical pump is automatically started for flap retraction.  Then, it is not automatically

stopped.  The FCOM recommends to select

it OFF manually.  Same on A330, when ENG 2 fails.

 In case of single failure, for spoiler retraction, if 

some of them remain extended at the time of  the failure.

 Introduction  Why not use the back up power source in all

cases?  Use of PTU  Use of electrical pumps

Use of RAT  Conclusion

 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.

 Overheat or 

reservoir low air pressure.  Loss of the

normal power  supply.  Reservoir low

level

Do not use the RAT. (system recovered for approach through normal pump)

The RAT can be used. On A320: Do not use the RAT. On other aircraft: The RAT can be used. (dedicated fluid reserve)

Dual hydraulic failure: (G+B or B+Y) RAT ……………………………… MAN ON

is displayed if the blue system is lost due to ELEC PUMP LO PR

Dual hydraulic failure: (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 of yellow system low level.

Dual hydraulic failure: (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.

Dual hydraulic failure: (G+B or G+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.

Dual hydraulic failure: (G+B or G+Y) In addition, with new FWC standard (K3.2): CONSIDER RAT MAN USE is displayed (except in case of green overheat or dual low level).

Why? This enables to recover the use of flaps or slats.

A330/A340 engine driven pump delivers about 175 liters per minute

A330/A340 RAT delivers about 80 liters per minute at 175 kt. Below this speed, the flow is reduced.

 When the RAT is used, to keep the hydraulic

flow demand consistent with the RAT performance: a rate limitation is introduced:  –

on the green surfaces on A330/340

 –

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

Single failure:   Automatic operation of PTU (Y or G).

Dual failure:  Manual use of Yellow electrical pump.  Manual use of RAT.

Single failure:  Manual use of green electrical pumps for 

approach only  manual use of PTUs (B or Y) for approach only

Dual failure:  Manual use of RAT.  Manual use of green electrical pump.

Single failure:  No permanent use of back up power sources.

Dual failure:.   Automatic use of RAT in a particular case.  In other cases, no permanent use of back up

power sources.

Single failure:  No permanent use of back up power sources.

Dual failure:.   Automatic or manual use of RAT.

In case of dual failure:  the back up power source is used  – provided

the failure enables its use (Ex: not in

case of overheat)  – provided

its use is convenient (Ex: no

permanent use of electrical pump on A330/340)