ata 27 efcs troubleshooting tipspdf

8/9/2019 ATA 27 EFCS Troubleshooting Tipspdf

http://slidepdf.com/reader/full/ata-27-efcs-troubleshooting-tipspdf 1/57

A320 Family

Electrical Flight Control SystemELAC/SEC/FCDC/Wiring Interface

TROUBLE SHOOTING TIPS

FOR MAINTENANCE USE

Reference: SEEL5 SA27TM1100002 - 02/201

Aircraft System Maintenance Aids



2

• Prevent unnecessary removals of ELAC and SEC thanks to abetter understanding of:

o ELAC and SEC systems (EFCS)

o ATA 27 Failure message and ECAM Warning

generation

• Provide guidelines and tips to the Maintenance team for a

quicker and more efficient fault resolution

Aim of this handbook

Purpose:

Please note:

• This handbook is valid for the A320 Family aircraft.

• These instructions do not amend or supersede any

information contained in Trouble Shooting Manual and Aircraft Maintenance Manual.

• This document will not be updated on regular basis.

• Enquiries related to this handbook should be addressed to:

Airbus Customer Services

Flight Control Systems – A320 FamilySEEL5

[email protected]

mailto:[email protected]

mailto:[email protected]



CONTENT

Page

0 Index of examples

1 Introduction

1.1 EFCS architecture 9

1.2 Maintenance feature 10

1.3 Available maintenance information 11

1.4 Glossary 13

2 Find the correct TSM task

2.1 How to proceed

o Identification of the correct TSM task 16

o Tips 17

2.2 Fault Examples

o Failure Message

⇒ potential trouble

makers 19

IR1

Failure

Elevator servocontrol faults

o Correlation with the adequate E/W 21

F/CTL

ELAC2

PITCH

FAULT

&

F/CTL

ELEV

SERVO

FAULT

CHECK PRIORITY WIRING

o Flight Control page display and Trouble‐Shooting 23

Detailed content

This booklet contains:

• A reminder on how to find the adequate TSM task corresponding to

a given fault (Chapter 2.)

• A method/guideline to maximise efficiency of the ELAC/SEC system

trouble-shooting (Chapter 3.)

• Recommendations applying in case of difficult and lengthy trouble-

shooting (Chapter 4).

• Many examples of typical failure cases illustrating these general

advices (See Index of Examples in page 6)

3



Page

3 Advanced Trouble-Shooting guidelines

3.1 Advanced T/S procedure

o Why an advanced T/S procedure? 26

o Advanced procedure flowchart 27

3.2 Typical cases and situations

o Specific

cases

not

requiring

T/S 29

Discriminate reset versus genuine failure

ACCLRM fault with ELAC1 / SEC2 / SEC1 under MEL

F/CTL ELEV SERVO FAULT with SEC2 under MEL during taxi with one engine running

AFS: ELAC

x

o How to use PLR and AIRMAN 33

Descriptions

Example: Fault linked to elevator servocontrol

Example: Fault linked to spoiler servocontrol

Example: Multiple XDCR failures

o TFU

linked

to

a TSM

task 39

o Faults without Failure Message 40

Pressure

Switch

issue

4 Diff icul t Trouble-Shooting

4.1 General recommendations

o Intermittent failure 44

o Wiring check 45

4.2 Typical faults

o Discrete interface / grounded signal 47

o F/CTL ALTN LAW & F/CTL DIRECT LAW 49

o Damaging failure 51

4.3 Useful tool for T/S

o Swapping tool (bundle) 54

CONTENT

4



6

Index of examples

0



Index of examples

E/W or Maint. Status Failure Message Refer to page:

F/ CTL Maint. Status ELAC/SEC x COM/MON OR BUS3/2 FROM

IR1/2/3

IR1/2/3 - BUS3/2

R1/2/3

P19

F/ CTL ELAC2 PITCH FAULTF/ CTL maint. status

F/CTL ELEV SERVO FAULT

ELAC2 OR WIRING FROM L G ELEV POSXDCR 34CE1

SEC2 OR WIRING FROM L G ELEV POS

XDCR 34CE1

L G ELEV POS XDCR 34CE1

p20p21

F/CTL ELEV SERVO FAULT L B ELEV MODE XDCR 34CE3 p34

F/CTL SIDESTICK PRIORITY

Or

F/CTL maint. Status

CHECK PRIORITY WIRING p22

F/CTL SIDESTICK PRIORITY +

F/CTL maint. Status

CHECK PRIORITY WIRING p22

F/CTL ELAC/SEC x FAULT ELAC/SEC x p28

F/CTL maint. status SEC1 OR WIRING FROM ACCLRM 1 12CE1

ELAC1 COM/MON OR WIRING FROM

ACCLRM 2 12CE2

ELAC2 COM/MON OR WIRING FROM

ACCLRM 4 12CE4

p30

F/CTL ELEV SERVO FAULT with

SEC2 under MMEL and only one

engine running

No failure message but L G/R Y servo is

boxed on status display

p31

AFS: ELAC x p32

F/ CTL Maint. Status ELAC/SEC x COM/MON OR BUS3/2 FROM

ADR1/2/3

ADR1/2/3 - BUS3/2

ADR1/2/3

p36

F/CTL SPLR FAULT L (R) SPLRx POS ERROR 31CEx p36

F/CTL SPLR FAULT L (R) SPLRx POS XDCR 31CEx p36

F/ CTL ELAC2 PITCH FAULT ELAC1 OR WIRING FROM L B ELEV POS

XDCR 34CE3

ELAC1 OR WIRING FROM R ELEV POS

MON XDCR

p38

F/CTL ELACx FAULT

F/CTL ELACy PITCH FAULT

No Failure message p40

p41

F/CTL ELACy PITCH FAULT CHECK PITCH CHANGE OVER OF ELAC1 p48

F/CTL ALTN LAW multiple failure message p49/50/51

F/CTL DIRECT LAW multiple failure message p49/50/51

F/CTL AIL SERVO FAULT L B AIL MODE VLV 33CE3 p52/53



8

Introduction

1



9

EFCS Description

EFCS architecture



EFCS Description

Failure Message and ECAM Warning (E/W) are

defined by each FCDC (in parallel) based on

information from all ELACs and SECs.

FCDC2

FCDC1

EFCS 2EFCS 1

ELACELAC

21

ELACELAC

SEC

32

1

DMC, FWC, CFDIU, FDIU

ECAM Warning

(E/W) generation

Failure message

generation

Failure Message and E/W are different whether the FAULT is

detected by one or more computers.

This correlation is enabled by the FCDCs.10

Maintenance features



Available Maintenance Information

A fault is characterized by two levels of information (symptoms):

E/W and status display: The purpose of those indications is

to inform the flight crew about system failure. They are

not designed for Trouble Shooting purpose.

Failure Message: They are intended to the maintenance

staff. Maintenance staff has to focus on FailureMessage to initiate the Trouble Shooting, not on the

E/W.

Trouble Shooting shall preferably be initiated using

the Failure Message and not using the E/W or

information from the lower ECAM F/CTL page.

NOTE

ECAM Warnings could be useful for maintenance

team providing that they are adequately correlated

with Failure Messages.

11

Fault Symptoms



Available Maintenance Information

For many systems, analysis of the TSD enables to provide

complementary information on the failure. However, EFCS has

been built so as to provide the most accurate level of information

in the failure message.

The best and sufficient entry point to trouble-shoot an EFCS fault

is the failure message (PFR, PLR, LLR) properly correlated with

the applicable ECAM Warning.

12

Trouble Shooting Data (TSD)

Example of EFCS TSD decoding:

TROUBLESHOOTING DATA

1435 27‐93‐34

FAIL 01 1 0 02 0A.3F.36

INP1 xxxx xxxx xxxx xxxx

INP2 xxxx xxxx xxxx xxxx

STS1 xxxx xxxx xxxx xxxx



STS4

xxxx xxxx xxxx xxxx

UTC / ATA chapter number

FAIL (failure details):

-01: failure number within the last flight leg

-1: failure counter (number of occurrence)

-0: external failure

-02: FWC flight phase

-0A.3F.36: byte1.byte2.byte3 of failure code

Decoding of the failure code: 0A.3F.36

ELAC1 OR WIRING FROM L B ELEV POS XDCR 34CE3

The failure code is the exact translation of the failure message in

a coded language. It does not contain additional data.

Background:



14

Find the correct TSM

task

2



Identification of the

correct TSM task

15

Find the correct TSM task

2.1



Refer to: ‘Correlation with the

adequate E/W’ p17 / p21-22

Refer to: ‘Failure

Message =

potential trouble-

makers’ p19-20

Enter the Failure Message

in AirN@v

This enables to take advantage ofthe FCDC correlation capabilities.

(each couple Failure Message +

E/W has a specific TSM task)

.1) How to proceed

16

How to use AirN@v

In AirN@v, use the advanced tools: ‘Start Troubleshooting’

and open the submenu ‘CFDS Fault Messages’ or ‘Fault

Pattern’. Then follow the above procedure.


If necessary, select the

TSM task corresponding to

the Class of the Failure

Message

Make sure the Failure

Message is associated withthe correct E/W

Find the appropriate TSM

task

Refer to: p17

Identification of the correct TSM task



Fault

symptoms

Tips

Differentiate class1 an class2 messages:

A same failure message might be either:

• Class 1 Failure Messages associated with an ‘ECAM Warning’

• Class 2 Failure Messages associated with a ‘maintenance status F/CTL’

Check failure symptoms of the selected TSM task:


17

.1) How to proceed



• Failure message ⇒ potential trouble makerso IR1 Failure

o Elevator servocontrol faults

• Correlation with the adequate E/Wo F/CTL ELAC2 PITCH FAULT & F/CTL ELEV SERVO FAULT

o CHECK PRIORITY WIRING

• Flight Control page and trouble-shooting

Fault examples

18


2.2

This paragraph aims at illustrating why it is essential to make

sure TSM task applies to the reported fault symptoms. This

enables to direct maintenance crew towards the most probable

trouble-makers.



IR1 Failure

IR1 network structure:

.2) Fault examples: Failure Message potential trouble makers

Case IR1 Fault detected by Failure Message Most probable component

involved

1

One computer unit

Ex: ELAC1 COM

ELAC1 COM OR

BUS3 FROM IR1

Computer or wiring to

first terminal block

2Two computer units on the same

BUS

Ex: ELAC1 COM & SEC 1 COM

IR1 – BUS3 IR1 or wiring to first

terminal block

3 Two

computers on

BUS3

and

two

computer on BUS2 IR1 IR1

Failure messages built by the FCDC:

If there is a failure of the IR1 or IR1 wiring, three different Failure Messages

can be elaborated by the FCDC depending on where the Fault is located

and which computers detect the fault.

19

ELAC 1

MON

COM

SEC 1

MON

COM

ELAC 2

MON

COM

SEC 2

MON

IR1

BUS 2BUS 3First terminal

block

COM


Each Failure Message incriminates the LRU and/or the wiring

which is the most likely at the origin of the FAULT.

SEC 3



.2) Fault examples: Failure Message potential trouble makers

20


Elevator servocontrol faults

Case Fault

detected by Failure Message Most probable component involved

1

ELAC

2

ELAC2 OR WIRING

FROM

L

G

ELEV

POS XDCR 34CE1

ELAC 2 or wiring

to

first

terminal

block

2 SEC 2

SEC2 OR WIRING

FROM L G ELEV

POS XDCR 34CE1

SEC 2 or wiring to

first terminal

block

3 ELAC 2 and

SEC 2

L G ELEV POS XDCR

34CE1 COM E2/S2

Servocontrol or

wiring to first

terminal block

NOTE

If ELAC2 and SEC2 detect the same FAULT (case 3), the FAULT

comes from the servo transducer or the common part of the wiring.

Avoid computer removal.

ELAC 2

SEC 2

L G ELEV

SERVO XDCR

Failure messages associated with L G servocontrol piston rod transducer

ELAC 2

SEC 2

L G ELEV

SERVO XDCR

ELAC 2

SEC2

L G ELEV

SERVO XDCR

Note: L G ELEV SERVO XDCR = Left Green Servocontrol Transducer

In general, each failure message incriminates the LRUs and/or

the wiring which is the most likely at the origin of the FAULT.



F/CTL ELAC2 PITCH FAULT & F/CTL ELEV SERVO FAULT

.2) Fault examples: Correlation with the adequate E/W

NOTE

1. In case of F/CTL ELEVATOR SERVO FAULT, no computer

shall be removed (in accordance with TSM).

2. If the PFR shows ‘F/CTL ELAC2 PITCH FAULT’ E/W

followed by ‘F/CTL ELEV SERVO FAULT’ E/W, this indicates

SEC2 has subsequently detected a FAULT on the same

servo. Accordingly, fault comes from the servocontrol or the

common part of the wiring.For FAULT correlation, use preferably the ‘F/CTL ELEV

SERVO FAULT’ E/W as this will lead you to a more accurate

Trouble Shooting task.

21


Correlating failure message with the corresponding ECAM

Warning aims at identifying the best T/S task.

These logics and design principles have been used to elaborate applicable

TSM tasks. Each fault symptom corresponds to a specific TSM task

Case Fault

detected by Failure Message Most probable component involved

1 ELAC 2 F/CTL ELAC2 PITCH

FAULT

ELAC 2 or wiring

to first terminal

block

2 SEC 2 E/W: F/CTL

SEC 2 or wiring to

first terminal

block

3 ELAC2 and

SEC 2

E/W: F/CTL ELEV

SERVO FAULT

Servocontrol or

wiring to first

terminal block

ELAC2

SEC2

L G ELEV

SERVO XDCR

ELAC2

SEC2

L G ELEV

SERVO XDCR

ELAC2

SEC2

L G ELEV

SERVO XDCR



CHECK PRIORITY WIRING

.2) Fault examples: Correlation with the adequate E/W

In this case,ELAC removal

shall be avoided

In this case, all components of the system

can be involved. But it is more probable that

the FAULT comes from the common part of the system: push button or common wiring.

22


Case Detected by Failure Message ECAM Warning Probable cause

1 At least, one

ELAC

CHECK PRIORITY

WIRING

F/CTL SIDE STICK

PRIORITY ELAC1, ELAC2, wiring

2 At least, one

SEC

CHECK PRIORITY

WIRING F/CTL

SEC1, SEC2, SEC3,

wiring

3At least, one

ELAC and one

SEC

CHECK PRIORITY

WIRING

F/CTL SIDE STICK

PRIORITY and F/CTL

Common wiring, push

button

These logics and design principles have been used to elaborate applicable

TSM tasks. Each fault symptom corresponds to a specific TSM task

Correlating failure message with the corresponding ECAM

Warning aims at identifying the best T/S task.



Mode monitoring on pitch axis

Interpretation of the informationsupplied by the F/CTL page

Left Green Elevator Servo

Control boxed on the F/CTL

page status display

Failure Message

incriminating the Left BlueElevator mode transducer

Why L G servo is boxed on the F/CTL page?

Due to the failed L B Elev mode transducer, ELAC2 and SEC2are not able to check that the L B servo is correctly in damping

mode. As per design, it has been chosen not to actuate the L G

servo to avoid possible force fighting with the L B servo.

Trouble-shooting shall not be initiated using Status display on the

F/CTL page. The maintenance staff has to use the failure message.

.2) Fault examples: Flight Control page display and Trouble‐Shooting

23


UTC

PH

ATA

WARNING

1406

02

270000

F/CTL

ELEV

SERVO

FAULTUTC

PH

ATA

FAULT

MESSAGE

1406 02 279334 L B ELEV MODE XDCR 34CE3

Failure message provides the correct information for Trouble Shooting (L B

Servo faulty). However the L G servo is boxed on the F/CTL page.



24

Advanced Trouble-

Shooting guidelines

3



Advanced T/S

procedure

25

Advanced Trouble‐Shooting guidelines

• Why an Advanced T/S procedure?

• Advanced procedure flowchart

3.1



26

.1) Advanced T/S procedure


Why an

advanced

procedure?

Some failures, particularly intermittent ones, might lead to

different fault patterns notably depending on their duration,

nature, etc ...

For instance, an intermittent failure may not be systematically

detected by all the involved computers inducing inaccurate faultcorrelation and thus rendering trouble-shooting more difficult.

Also, opportunity has been taken to document specific fault

symptoms that might cause incorrect interpretation/action of

maintenance team.

This booklet section details an advanced T/S procedurepermitting to increase the trouble-shooting efficiency.

Adherence to these guidelines will:

• facilitate identification of the most pertinent TSM task

• permit to fix more quickly a fault

• prevent useless computers/parts removals that might

result from lengthy trouble-shooting



Refer to: ‘Specific

cases not requiring

T/S’ p29 to 32

Refer to: ‘How to

use PLR and

AIRMAN’ p33 to 38

Refer to: ‘Faults

without Failure

Message’ p40 to 41

Refer to: ‘TFU

linked to a TSMtask’ p39

.1) Advanced T/S procedure

Advanced procedure flowchart

27


Failure incriminating the

same LRU in PFR/PLR

/AIRMAN ?

Identify failure

symptoms

(E/W & Failure

Message)

No need of T/S

E/W associated with a

Failure MessageDedicated TSM

tasks

yes

Identify if possible

more accurate

failure symptoms

by correlation

yes

Use AirN@v to find

an appropriate

TSM task

Adhere to TFU T/S advices

block when appropriate.

Is the failure due

to specific

conditions∗?

yes

no

Specific conditions

mean:

‘MEL’,

‘reset’,

‘AFS

Failure incriminating theseveral XDCR in PFR/PLR

/AIRMAN ?

no

yes

no

no



• Specific cases not requiring T/SoDiscriminate reset & genuine failure

o ACCLRM fault with ELAC1 / SEC2 / SEC1 under MEL

oF/CTL ELEV SERVO FAULT with SEC2 under MEL

with one engine running

o AFS: ELAC x

• How to use PLR and AIRMANoDescriptions

oExample 1: Fault linked to elevator servocontrol

o

Example 2: Fault linked to ADRoExample 3: Fault linked to spoiler servocontrol

oExample 4: Multiple XDCR failures

• TFU linked to a TSM task

• Faults without Failure MessageoPressure switch issue

Typical cases and

situations

28


3.2



Discriminate reset versus genuine failure

Signature of an ELAC or SEC reset (via Push Button) is similar to a genuine failure.

Accordingly, reset can only be identified by an analysis of the PFR.

If the maintenance staff identifies a FAULT due to a reset, there is no

need of further maintenance action for this specific failure entry.

Furthermore, the failure shall not be used to substantiate a computer

removal.

.2) Typical cases and situations: Specific cases not requiring T/S

Reset of E/W Failure Message

ELAC x F/CTL ELAC x FAULT ELAC x

SEC y F/CTL SEC y FAULT SEC y

29

How to identify a reset:

Above mentioned FAULTs when occurring subsequently to another ATA27 E/W are

very likely attributable to a reset.


Example:

UTC PH ATA WARNING

2351 02 270000 F/CTL ELAC 1 PITCH FAULT

2359 02 270000 F/CTL

ELAC

1

FAULT

UTC PH ATA FAULT MESSAGE

2351 02 279334 ELAC1 COM OR WIRING TO L B ELEV SERVO VLV 34CE3

2359 02 279334 ELAC1

associated withFailure Message

a few minute after

the original fault

signature of an ELAC1

reset

T/S has to be performed based on the earlier Failure Message. In this example: ‘ELAC1COM OR WIRING TO L B ELEV SERVO VLV 34CE3’

Background:



Accelerometer fault mentioned here-above does not requires T/S if the

corresponding computer is under MEL.

Accelerometer fault with ELAC1 / SEC2 / SEC1

under MEL

Case MEL ACCLRM without

power supply Fault

that

does

not

requires

T/S

1 ELAC 1 ACCLRM 1 E/W: F/CTL

Failure Message: SEC1 OR WIRING FROM ACCLRM 1 12CE1

2 SEC 1 ACCLRM 2

E/W: F/CTL

Failure Message: ELAC1 COM/MON OR WIRING FROM

ACCLRM 2 12CE2

3 SEC 2 ACCLRM 4

E/W: F/CTL

Failure Message: ELAC2 COM/MON OR WIRING FROM

ACCLRM 4 12CE4

30



If ELAC1 is under MEL, applicable Circuit Breaker

is opened. Accelerometer 1 is no longer powered

due to system architecture.

SEC1 that acquires the accelerometer data will

subsequently detect a loss of accelerometer

signal.

The PFR will show Failure Message SEC1 OR

WIRING FROM ACCLRM 1 12CE1

ELAC 1 under MEL

SEC 1

ELAC 1

A C C L RM 1

POWER SUPPLY

Circuit Breaker

data

data

supply



31

F/CTL ELEV SERVO FAULT with SEC2 under MEL

during taxi with one engine running

ECAM Warning ‘F/CTL ELEV SERVO FAULT’ will disappear as soon as

PTU operates or 2nd engine is operative.

This failure symptom does not require T/S.

Note: same type of rationale can be built whether engine 1 is off .



NOTE

This is covered by a note in the Operational Procedure of the MEL

Situation Consequence Explanation

1. SEC

2 under

MEL SEC

2

not

able

to

servo

the

R

Y

and

the L G servo

2. Engine 2 off

3. PTU inhibited

Y hydraulic not available

ELAC 2 not able to take over the

pitch axis

ELACs are capable to achieve pitch

control if both ELEVs & THSA are

available

L G Servo is boxed on the status display and the ECAM

Warning ‘F/CTL ELEV SERVO FAULT’ appears

Neither SEC2 nor ELAC2 can

control the L G STCL despite the

availability of the G hydraulic

Engine 1 > GREEN

hydraulics

Engine 2 > YELLOW

hydraulics

SEC 2 under MEL

Example:

F/CTL ELEV SERVO FAULT warning might appear on ECAM when SEC2 is under MEL

during taxi if:

• PTU is inhibited

• only one engine is operating

.

Background:



As long as the ELACs are capable to achieve the Auto Pilot (AP) order, they send to

Auto Flight System (AFS) computers a discrete signals which allows the AP

engagement.

‘AFS: ELAC x’ indicates that one of the computers belonging to the Auto Flight System

does not receive anymore its AP engagement discrete inputs from the ELAC.

This might be an indication of:

• a genuine failure of the discrete input interface

• or the consequence of the inability for ELAC to perform AP order.

32

AFS: ELAC x



UTC

PH

ATA

WARNING

1403 06 290000 HYD B SYS LO PR

1403 06 290000 HYD B ELEC PUMP LO PR

UTC

PH

ATA

FAULT

MESSAGE

1403 02 279334 AFS:ELAC1

UTC

PH

ATA

WARNING

1316 02

270000

F/CTL

ELEV

SERVO

FAULT

UTC

PH

ATA

FAULT

MESSAGE

1316 02 273451 L B ELEV SERVO VLV 34CE3

1316 02 279334 AFS: ELAC1

Examples: inability for ELAC to perform the pitch servo loop:

On the two above examples, ELAC1 cannot take over the pitch axis leading to the

inability of the ELAC1 to correctly perform the AP order. Consequently AP

authorization discrete inputs are not sent by the ELAC1 and ‘AFS: ELAC1’ is

displayed.

1.

2.

Do not use ‘AFS: ELAC1’ or ‘AFS: ELAC2’ Failure Messages to substantiate

an ELAC removal.

If Failure Message is confirmed on ground, apply corresponding TSM task.

Design principle

TSM content:

AP Engagement Authorization discrete inputs are monitored by the ELAC (wrap up).

An ELAC discrete input emission failure would be self-detected by the ELAC leading

to ELAC FAULT. AFS: ELAC1 failure message is thus unlikely attributable to the

ELAC.



33

If a similar fault has already occurred, the maintenance staff:

• shall avoid repeating the same step of TSM task

• may try to find a more accurate TSM task using the other Failure

messages present in PFR / PLR / AIRMAN.

.2) Typical cases and situations: How to use PLR and AIRMAN

How to use PLR and AIRMAN

Descriptions

If the aircraft is experiencing recurring fault symptoms, analysis of previous PFR,

PLR and AIRMAN data might provide valuable information to increase T/S

efficiency.

In particular, this review might enable:

• to identify if different failure modes have been experienced

• and, whenever possible, to select a more appropriate TSM task.

How to proceed:

a. Find failure messages incriminating same LRU in

PFR/PLR/AIRMAN

b. Find failure messages incriminating other XDCR

Refer to:

Example 1 Faul t l inked to elevator servocontro l p34

Example 2 Fault linked to ADR p35Example 3 Faul t linked to spoi ler servocontrol p36

Example 4 Mult iple F/CTL XDCR fai lures p37-38


NOTE

Exploring the aircraft fault history (previous PFR / PLR / AIRMAN)

also enables to check trouble-shooting already accomplished and

avoid repeating same step of the TSM task.



34



Example 1 Fault linked to elevator servocontrol:

For background & pr inciple refer to:

‘elevator servocontrol faults’ in chapter 2

p20 and p21


Elevator servocontrols are controlled and monitored by one ELAC & one SEC.

It might happen that intermittent failures at the level of the servocontrol be not detected

by both computers.

When several Failure Messages involving the same LRU are shown

in PFR/PLR/AIRMAN... comparison of the TSM task content enables

to identify more precisely the common point.

Example:

Original fault symptoms:

F/CTL ELAC 2 PITCH FAULT

ELAC2 OR WIRING FROM L B ELEV MODE XDCR 34CE3

If in previous PFR / PLR / AIRMAN, one of the following fault has already occurred:

• maintenance status F/CTL

• SEC2 OR WIRING FROM L B ELEV MODE XDCR 34CE3

• F/CTL ELEV SERVO FAULT• SEC2 OR WIRING FROM L B ELEV MODE XDCR 34CE3

• F/CTL ELEV SERVO FAULT

• L B ELEV MODE XDCR 34CE3

It can be concluded that the component at the origin of the fault is certainly the

common LRU (in this case L B ELEV MODE XDCR 34CE3) or the common wiring.

Using the Failure Message L B ELEV MODE XDCR 34CE3 will lead you to a more

accurate TSM task.



35



Example 2

Fault linked to ADR





ELAC 1

MON

COM

SEC 1

MON

COM

ELAC 2

MON

COM

SEC 2

MON

ADR1

BUS 2BUS 3First terminal

block

COM

For background & principle

refer to: p19

Example:

Original fault symptoms

ELAC1 COM OR BUS3 FROM ADR1If previous PFR / PLR / AIRMAN show one of the following faults:

ADR1 – BUS3

ADR1

It can be concluded that the component at the origin of the fault is certainly the

common LRU (in this case ADR1) or the common wiring.

Using the Failure Message ADR1 or ADR1 – BUS3 will lead you to a more

accurate TSM task.

SEC 3



36



Example 3

Fault linked to spoiler servocontrol:


SECSV Spoiler

servocontrol

Fault symptoms A:F/CTL SPLR FAULT

L (R) SPLRx POS ERROR 31CEx

Possible causes:• SEC,

• Wiring from SEC to servovalve

• Wiring from position transducer to SEC

• Spoiler servocontrol

Fault symptoms B:F/CTL SPLR FAULT

L (R) SPLRx POS XDCR 31CEx

Possible causes:• SEC,

• Wiring from position transducer to SEC

• Spoiler servocontrol

Analysis

The comparison of the possible causes listed in the TSM tasks enables to ruleout the Wiring from SEC to servovalve. It incriminates more precisely the

spoiler servocontrol transducer interface.




XDCR



37



Example 4 Multiple XDCR failures - Description:


Case

Number of XDCR

Failure

Messages

reported on PFR

/ PLR / AIRMAN

Most probable

component

involved

1

Single XDCR

Failure Message

XDCR, feedback

wiring, or ACS

wiring to first

terminal block

2 Two or more XDCR

Failure Message

Computer or ACS

wiring to first

terminal block

ELAC

XDCR 2

XDCR 1

XDCR

3

ELAC

XDCR 2

XDCR 1

XDCR 3

Each ELAC & SEC supplies their corresponding XDCR. These power supply

circuitries are called Alternating Current Supplies (ACS). If an ACS fault occurs, the

affected ELAC/SEC XDCRs are no longer powered. They are declared faulty by the

concerned computers.

If there is more than one Failure Message ‘ELAC/SEC x or WIRING TO

XDCR’ in PFR, an ACS fault can be suspected. TSM (as shown here-

after) enables to identify the most appropriate TSM task

ACS Wiring

Feedback

Wiring



38



Examples 4


Multiple XDCR failures – Typical PFR:

UTC

PH

ATA

WARNING

1313 02 270000 F/CTL ELAC 1 PITCH FAULT

UTC

PH

ATA

FAULT

MESSAGE

1313 02 279334 ELAC1 OR WIRING FROM L B ELEV POS XDCR 34CE3

1313 02 279334 ELAC1 OR WIRING FROM R ELEV POS MON XDCR

Taken independently thesefailure messages lead you to

different TSM tasks.

When two XDCR Failure

Messages fed by the same ACS

are displayed in the PFR, TSM

enables to identify a specific

TSM task.

Extract of TSM task 27-90-00-810-813:

TSM already proposes such failure message correlation:

NOTE

Review of the PLR and AIRMAN enables to make sure that no other

XDCR fault linked to the same ACS has been previously experienced.



TFU linked to a TSM task

A TFU might be linked to a particular fault symptoms in AirN@v. Maintenance

advice block might contain useful information for trouble-shooting.

Background:

TFU linked to the

ECAM Warning F/CTL

ELAC 1 PITCH FAULT

TFU linked to the CFDS

Fault Message ELAC1 OR

WIRING TO L G ELEV

SERVO VLV 34CE1

39

.2) Typical cases and situations: TFU linked to a TSM task

If a TFU is linked to the TSM task, follow, if applicable, the

recommendations contained in the ‘Maintenance advice’ paragraph

of the TFU.


How to find a TFU linked to a TSM task:



40

.2) Typical cases and situations: Faults without Failure Message

T/S procedure if there is no Failure Messageassociated to a given E/W


Dedicated TSM tasks permitting to address E/W not associated

with a Failure Message can be found in AirN@v.

Some of these tasks are incriminating Pressure Switches andFWCs as a possible cause.

NOTE

It is advisable to check if the E/W has already occurred in PLR /

AIRMAN. If E/W was previously associated with a failure

message, trouble shooting procedure related to this maintenance

message has to be carried out.

Refer to the next page, for

further explanations



41

.2) Typical cases and situations: Faults without Failure Message

Pressure Switch issue


ELAC: For each hydraulic system, the ELACs acquire the hydraulic status

using three different sensors: two pressure switches (P/SW) and

one pressure transmitter (P/XMTR).

Hydraulic status built by the ELACs is voted using the three pieces

of information.

FWC: Flight Warning Computer (FWC) hydraulic information is based onone P/SW information.

P/SW 1

P/XMTR

FWC

P/SW 2

ELAC

Low press.

High

press.

Low press.

ELAC

senses a

Low press.

FCDC

FWC sees:

•High press.

•ELAC not

available for pi tch

Generation of the E/W

‘F/CTL ELAC PITCH

FAULT’.

Per design: no

Failure Message

ELAC not available for pi tch

(due to low pressure detected by the ELAC)

Spurious E/W caused by erroneous P/SW information:

Design & Principle:

Proper identification of the fault symptoms and adherence to the TSM will

direct trouble-shooting towards the failed P/SW or FWC.



42

Difficult Trouble-

Shooting

4



• Intermittent failure

• Wiring Check

General

recommendations

43

4.1

Difficult Trouble-Shooting



44

.1) General recommendations: Intermittent failure

Intermittent failure

Some failures are intermittent and thus not reproducible on

ground.

Trouble-shooting accomplishment is rendered more difficult as

efficiency of the corrective action cannot be confirmed.

In these cases, it is necessary to properly follow-up and monitor

the aircraft in order to make sure that the fault has been properly

cured.

NOTE

If an intermittent failure occurred three times, it is advisable to

apply the fault isolation of the corresponding TSM task step by

step until final resolution.


Intermittent failure requires an accurate follow up of the aircraft.

Tight follow up of the aircraft (including review of the

maintenance record, PLR, AIRMAN) enables to avoid

same step of the TSM repeating (for instance, multipleELAC or SEC removals).



45

.1) General recommendations: Wiring check

Wiring check

It consists of:

1. Continuity check,

2. Quality of the connections,

3. Short circuit / Insulation tests,

4. Resistance check.

Resistance check has to be preferred for intermittent failure (better

than continuity). It may highlight possible corrosion, improper

contact or improper connector locking, contamination, moisture

ingress, etc…

• Compare the resistance of the adjacent wires (Two adjacentwires have in general the same length and same gauge)

• A discrepancy of a few ohms can be a valid indication / positive

finding for an intermittent failure (For calculation of the normal

resistance value, refer to Standard Manual : resistance per meter).

• Do not hesitate to shake moderately the wires while performing

the test. The resistance value should not fluctuates.

How to interpret resistance measurement:

NOTE

To see the resistance fluctuations prefer use an analogical

ohmmeter with a needle (a digital ohmmeter may reduce

these fluctuations and make them invisible on the screen).


Wiring check:



• Discrete interface / grounded signal

• F/CTL ALTN LAW & F/CTL DIRECT LAW

• Damaging failure

Typical faults

46


4.2



MON COM

ELAC 2

47

.2) Typical faults: Discrete interface / grounded signal


Discrete interface / grounded signal

Computers send (receive) discrete signals to (from) other computers. Some failures

mode might be such that an erroneous information can be spread in the concerned

discrete network.

Principle:

NOTE

1. In case of an intermittent failure of the discrete links, the fault may

not be reproduced on ground. In this case replace one by one the

involved computers.

2. As far as F/CTL computers are concerned, discrete inputs corrupted

by internal computer fault are more frequently caused by SECs (failure

of lightning diodes located on discrete inputs).

For the concerned DSI, ELAC2 detects a COM/MON discrepancy. Failure message

will incriminate ELAC2 or wiring from LRUx while SEC2 is at fault.

Most of the time the failure is not detected by the faulty computer (SEC2 in this case).

LRUx

MON COM

DSO x DSO y

Ground detected by

ELAC2 COM

DSI x DSI y DSI x DSI y

Removing SEC2 will remove the

ground point

Ground signal received

Open circuit signal receivedGround sent by the

faulty SEC2 COM

MON COM

SEC 2

Background:

If a failure of the discrete links is suspected, TSM task is 31-32-00-810-

932 is cross-referenced in the applicable TSM task.

This task consists in removing one by one all possibly involved computers

to identify the faulty one (see example here-after).



48

.2) Typical faults: Discrete interface / grounded signal


Discrete interface / grounded signal

Example of TSM task:

TSM task 31-32-00-810-932 cross-

referenced

DSO 09 of ELAC1 is

connected to SEC1 & SEC2

As per TSM task 31-32-00-810-932, SEC1 & SEC2 must be removed from their

rack and the effect on the failure verified.



49

F/CTL ALTN LAW & F/CTL DIRECT LAW

When ‘F/CTL ALTN / DIRECT LAW’ are reported, PFR shall be

reviewed and faults at the origin of the law reversion have to be

identified and troubleshot individually.

.2) Typical faults: F/CTL ALTN LAW & F/CTL DIRECT LAW


‘F/CTL ALTN LAW’ and ‘F/CTL DIRECT LAW’ ECAM

Warnings are a consequence of multiple failures.

These E/W are displayed to inform the pilot on the level

of Flight Control protection available to control the

aircraft.

They do not bring valuable information for T/S purpose.

Correlation with E/W F/CTL ALTN / DIRECT LAW might

not be possible as all possible failure configurations

leading to Law reversion have not been documented in

the TSM.

NOTE

A description of the failure combination leading to ‘F/CTL ALTN /

DIRECT LAW’ reversion can be found in the in FCOM Volume 1

Chapter 27 Section 30.

A copy of this table is provided in the next page.



50


E x t r a c t o f F C O

M

V o l u m e 1 C h a p t e r 2 7

S e c t i o n 3 0

.2) Typical faults: F/CTL ALTN LAW & F/CTL DIRECT LAW



51

When instructed by TSM, checking the wiring for a possible short

circuit before replacing the computer is highly recommended. This

enables to prevent multiple and useless computer replacements.

.2) Typical faults: Damaging failure


Some failures (in particular failures - short-circuit - on wiring

involving solenoid supply) can damage computers.

Consequently, computer swapping may temporally fix the

failure until the new computer get damaged.

When a failure can possibly damage computers, TSM task

contains a caution requesting not to swap computers. Also,

first step of the TSM task consists in checking that there is no

short circuit in the wiring interface

Refer to the next page

depicting an example of

TSM Task involvingsolenoid.

Damaging failure



52

Damaging failure


Example of a TSM task involving solenoid:

Caution: to avoid

swapping.

First step of the TSM

task is a check of

resistances for a

possible short circuit.

.2) Typical faults: Damaging failure



Useful tool for T/S

53

4.3




54

.3) Useful tool for T/S

The Swapping tool

Principle

The swapping tool is an equipment developed by Airbus which simulates on

ground a swapping between two Servo Controls. The swapping tools swap all

Inputs / Outputs from one servocontrol to another servocontrol.

Like a computer swapping which can prove that a computer is or not at the

origin of a fault, the swapping tool can enable to identify if a Servo Control or

the wiring is at the origin of a Fault.

Advantages of using the swapping tool:

• avoid servocontrol removal task while Trouble Shooting

• minimize/optimize wiring check


Computer 1

Computer 2

Servo 1

Servo 2

Swapping

tool

Applicable references:

Elevators AMM 27-34-00-860-079

Ailerons AMM 27-14-00-760-001



55


The Swapping tool

Examples

.3) Useful tool for T/S

ata 27 efcs troubleshooting tipspdf

Documents