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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
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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
DL-CE-DPT-SEEL5@airbus.com
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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
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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
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6
Index of examples
0
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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
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8
Introduction
1
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9
EFCS Description
EFCS architecture
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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
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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
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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
STS2 xxxx xxxx xxxx xxxx
STS3 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:
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14
Find the correct TSM
task
2
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Identification of the
correct TSM task
15
Find the correct TSM task
2.1
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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.
Find the correct TSM task
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
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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:
Find the correct TSM task
17
.1) How to proceed
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• 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
Find the correct TSM task
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.
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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
Find the correct TSM task
Each Failure Message incriminates the LRU and/or the wiring
which is the most likely at the origin of the FAULT.
SEC 3
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.2) Fault examples: Failure Message potential trouble makers
20
Find the correct TSM task
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.
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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
Find the correct TSM task
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
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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
Find the correct TSM task
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.
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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
Find the correct TSM task
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.
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24
Advanced Trouble-
Shooting guidelines
3
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Advanced T/S
procedure
25
Advanced Trouble‐Shooting guidelines
• Why an Advanced T/S procedure?
• Advanced procedure flowchart
3.1
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26
.1) Advanced T/S procedure
Advanced Trouble‐Shooting guidelines
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
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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
Advanced Trouble‐Shooting guidelines
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
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• 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
Advanced Trouble‐Shooting guidelines
3.2
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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.
Advanced Trouble‐Shooting guidelines
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:
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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
Advanced Trouble‐Shooting guidelines
.2) Typical cases and situations: Specific cases not requiring T/S
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
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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 .
.2) Typical cases and situations: Specific cases not requiring T/S
Advanced Trouble‐Shooting guidelines
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:
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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
.2) Typical cases and situations: Specific cases not requiring T/S
Advanced Trouble‐Shooting guidelines
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.
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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
Advanced Trouble‐Shooting guidelines
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.
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.2) Typical cases and situations: How to use PLR and AIRMAN
How to use PLR and AIRMAN
Example 1 Fault linked to elevator servocontrol:
For background & pr inciple refer to:
‘elevator servocontrol faults’ in chapter 2
p20 and p21
Advanced Trouble‐Shooting guidelines
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.
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.2) Typical cases and situations: How to use PLR and AIRMAN
How to use PLR and AIRMAN
Example 2
Fault linked to ADR
Advanced Trouble‐Shooting guidelines
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.
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
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.2) Typical cases and situations: How to use PLR and AIRMAN
How to use PLR and AIRMAN
Example 3
Fault linked to spoiler servocontrol:
Advanced Trouble‐Shooting guidelines
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.
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.
XDCR
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.2) Typical cases and situations: How to use PLR and AIRMAN
How to use PLR and AIRMAN
Example 4 Multiple XDCR failures - Description:
Advanced Trouble‐Shooting guidelines
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
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38
.2) Typical cases and situations: How to use PLR and AIRMAN
How to use PLR and AIRMAN
Examples 4
Advanced Trouble‐Shooting guidelines
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.
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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.
Advanced Trouble‐Shooting guidelines
How to find a TFU linked to a TSM task:
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.2) Typical cases and situations: Faults without Failure Message
T/S procedure if there is no Failure Messageassociated to a given E/W
Advanced Trouble‐Shooting guidelines
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
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.2) Typical cases and situations: Faults without Failure Message
Pressure Switch issue
Advanced Trouble‐Shooting guidelines
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.
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Difficult Trouble-
Shooting
4
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• Intermittent failure
• Wiring Check
General
recommendations
43
4.1
Difficult Trouble-Shooting
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.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.
Difficult Trouble-Shooting
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).
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.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).
Difficult Trouble-Shooting
Wiring check:
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• Discrete interface / grounded signal
• F/CTL ALTN LAW & F/CTL DIRECT LAW
• Damaging failure
Typical faults
46
Difficult Trouble-Shooting
4.2
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MON COM
ELAC 2
47
.2) Typical faults: Discrete interface / grounded signal
Difficult Trouble-Shooting
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).
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.2) Typical faults: Discrete interface / grounded signal
Difficult Trouble-Shooting
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.
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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
Difficult Trouble-Shooting
‘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.
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Difficult Trouble-Shooting
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
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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
Difficult Trouble-Shooting
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
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Damaging failure
Difficult Trouble-Shooting
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
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Useful tool for T/S
53
4.3
Difficult Trouble-Shooting
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.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
Difficult Trouble-Shooting
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
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Difficult Trouble-Shooting
The Swapping tool
Examples
.3) Useful tool for T/S
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