CUSTOMER SERVICES DIRECTORATE

1 ROND POINT MAURICE BELLONTE 

31707 BLAGNAC CEDEX FRANCE 

TELEPHONE + 33 (0)5 61 93 33 33 

ALERT OPERATORS TRANSMISSION - AOT

SUBJECT: ATA 32 – MLG DOOR SLOW OPERATION DETECTION. 

 

AIRCRAFT TYPE: 

A321, A320, A319, A318. 

OUR REF.: A32N001-13 dated 24-Jun-2013. 

1. AIRCRAFT AFFECTED 

A321, A320, A319, A318 aircraft fitted with the following configuration: 

- LGCIU interconnect wiring ARINC 429 (Ref. 1 MOD 39303 or SB A320-32-1409 standard) 

AND 

- 2 LGCIUs PN 80-178-02-88012 (Ref. 2 MOD 37831or SB A320-32-1373 standard) or PN 80-

178-03-88013 (Ref. 3 MOD 152862 or SB A320-32-1401 standard) 

AND 

- MLG door actuators PN 114122006 or PN 114122007 or PN 114122009 or PN 114122010 or 

PN 114122011 or PN 114122012 (pre Ref. 4 MOD 153655 or SB A320-32-1407). 

2. REFERENCED DOCUMENTATION 

2.1 APPENDIX 

- Appendix A 

- Appendix B 

2.2 REFERENCES 

- Ref. 1: MOD 39303 / SB A320-32-1409 – Introduction of LGCIU interconnect wiring 

- Ref. 2: MOD 37831 / SB A320-32-1373 – Introduction of LGCIU PN 80-178-02-88012 

- Ref. 3: MOD 152862 / SB A320-32-1401 – Introduction of LGCIU PN 80-178-03-88013 

- Ref. 4: MOD 153655 / SB A320-32-1407 – Introduction of door actuator PN 114122014 

- Ref. 5: AOT A320-32A1390 

- Ref. 6: SB A320-32-1390 Rev1 – MLG door actuator repetitive inspection 

- Ref. 7: MOD 26353 / SB A320-32-1182 – Introduction of LGCIU PN 664700500A4D 

- Ref. 8: EASA AD 2011-0069 

3. REASON 

Further to in-service reports of A320 family MLG door actuator internal failures leading to slow door 

operation, Airbus has issued in Feb 2011 the Ref. 5 AOT A320-32A1390 requesting operators to 

perform two inspections to detect advance indication of a potential door actuator failure. These 

inspections mandated by EASA AD 2011-0069 (Ref. 8) consist of: 

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ALERT OPERATORS TRANSMISSION - AOT 

• A weekly check for specific pair of CFDS messages, 

• A repetitive MLG door actuator inspection (every 425 FC). 

It has been identified that aircraft equipped with LGCIU interconnect wiring ARINC 429 ( Ref. 1 

standard) and with 2 LGCIUs PN 80-178-0x-8801x (Ref. 2 or Ref. 3 standards) generate different CFDS 

messages than the ones listed in Ref. 5 AOT. 

3.1 FACTS 

Aircraft equipped with LGCIU interconnect wiring ARINC 429 ( Ref. 1 standard) and fitted with 2 LGCIUs 

PN 80-178-0x-8801x (Ref. 2 or Ref. 3 standards) generates CFDS messages which are different 

compared to the messages listed in Ref. 5 AOT . 

3.2 INVESTIGATION 

Investigation revealed that in case of a slow door operation, LGCIUs PN 80-178-0x-8801x (Ref. 2 or 

Ref. 3 standards) equipped with LGCIU interconnect wiring ARINC 429 (Ref. 1 standard) will not 

generate “TGT POS” CFDS fault messages after a 4s confirmation time but will generate different fault 

messages after a 30s confirmation time.

3.3 CONSEQUENCES 

For aircraft fitted with LGCIU interconnect wiring ARINC 429 (Ref. 1 standard) and fitted with 2 LGCIUs 

PN 80-178-0x-8801x (Ref. 2 or Ref. 3 standards), in case of slow door operation, the generation of 

CFDS messages is different compared to the messages listed in Ref 5. AOT and will be triggered after a 

longer confirmation time. As a consequence, the detection of a slow door operation is less efficient.

3.4 AIM 

- This AOT request A320 Family operators to perform a weekly inspection of MLG door actuators 

as per Para 4.2.2 of this AOT pending disconnection of the interconnect wiring as per Para 4.21 

of this AOT. 

- This AOT provides the procedure to disconnect the LGCIU interconnect wiring ARINC 429 on 

aircraft equipped with 2 LGCIUs PN 80-178-0x-8801x (Ref. 2 or Ref. 3 standards). This will 

cancel the weekly door actuator inspection requirement and allow returning to the inspection 

regime of Ref. 5 AOT and Ref. 6 ISB mandated by AD Ref. 8. 

4. SHORT TERM ACTION 

For A320 Family aircraft equipped with LGCIU interconnect wiring ARINC 429 (Ref. 1 standard) and 

fitted with 2 LGCIU PN 80-178-0x-8801x (Ref. 2 or Ref. 3 standards), Airbus request accomplishment of 

a weekly MLG door actuator inspection as per the procedure described in paragraph 4.2.2. of this AOT. 

Airbus recommends to disconnect the LGCIUs interconnect wiring ARINC 429 as per procedure 

mentioned in paragraph 4.2.1 of this AOT to come back, to the generation of CFDS message format in 

accordance with mandated Ref. 5 AOT. 

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ALERT OPERATORS TRANSMISSION - AOT 

The disconnection of the LGCIU interconnect wiring ARINC 429 cancels the requirement of the weekly 

MLG door actuator inspection as per Para 4.2.2. 

This will allow returning to the inspection regime of Ref. 5 AOT and Ref. 6 ISB mandated by AD Ref. 8. 

Interconnection 

wiring installed on a/c 

LGCIU 1 LGCIU 2 Interconnection 

wiring removal? 

Yes 80-178-0x-8801x 80-178-0x-8801x YES 

Yes 664700500A4x 664700500A4x No 

Yes 80-178-0x-8801x 664700500A4x No 

Yes 664700500A4x 80-178-0x-8801x No 

Accomplishment of weekly MLG Door actuator inspection as per Para 4.2.2 of this AOT is also an 

acceptable alternative to the disconnection of the LGCIU interconnect wiring as per Para 4.2.1 of this 

AOT. 

NOTE: The accomplishment of the weekly MLG door actuator inspection as per Para. 4.2.2 of this AOT 

cancels and replace the requirement of weekly CFDS messages check as per Ref 5. AOT. 

NOTE: Operators must ensure aircraft configuration management to assess potential effectivity of this 

AOT to their fleet. 

4.1 PLANNING AND MANPOWER 

4.1.1 ACCOMPLISHMENT TIMESCALE 

• Weekly MLG door actuator inspection: 

The accomplishment of the weekly MLG door actuator inspection mentioned in Para 4.2.2 

must be performed before the accumulation of 800 FC since first flight or no later than two (2) 

weeks from receipt of this AOT at the latest. For all aircraft in the configuration mentioned in 

paragraph 1 of this AOT, repeat the actuator inspection every week (not exceeding 8 days) or 

5 FC whichever occurs later pending disconnection of interconnect wiring as per Para. 4.2.1 

of this AOT. 

4.1.2 MANPOWER 

LGCIU interconnect wiring ARINC 429 disconnection: 

 

Total manhours: 4.0 

Elapsed time (hours): 4.0 

MLG door actuator inspection: 

Total manhours: 1.5 

Elapsed time (hours): 1.0 

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ALERT OPERATORS TRANSMISSION - AOT 

4.2 DESCRIPTION 

4.2.1 DISCONNECTION OF INTERCONNECT WIRING 

WARNING: MAKE SURE THAT YOU OBEY ALL THE WARNINGS AND ALL THE CAUTIONS 

INCLUDED IN THE REFERENCED PROCEDURES. 

CAUTION: ALWAYS OBEY THE PRECAUTIONS THAT FOLLOW TO KEEP 

ELECTRICAL WIRING IN A SATISFACTORY CONDITION (ELECTRICALLY 

 AND MECHANICALLY SERVICEABLE). WHEN YOU DO MAINTENANCE 

WORK, REPAIRS OR MODIFICATIONS, ALWAYS KEEP ELECTRICAL WIRING, 

COMPONENTS AND THE WORK AREA AS CLEAN AS POSSIBLE. TO DO 

THIS: 

- PUT PROTECTION, SUCH AS PLASTIC SHEETING, CLOTHS, ETC; AS 

NECESSARY ON WIRING AND COMPONENTS 

- REGULARLY REMOVE ALL SHAVINGS, UNWANTED MATERIAL AND 

OTHER CONTAMINATION. 

THESE PRECAUTIONS WILL DECREASE THE RISK OF CONTAMINATION 

AND DAMAGE TO THE ELECTRICAL WIRING INSTALLATION. 

IF THERE IS CONTAMINATION, REFER TO ESPM 20-55-00. 

1. Apply Flight Configuration Precautions defined in AMM Task 32-00-00-860-001-A01 “Flight 

Configuration Precautions without Electrical Power” or with AMM Task 32-00-00-860-001-A 

“Flight Configuration Precautions with Electrical Power” if other aircraft systems requires 

power. 

2. Ensure that the following Circuit Breakers have been isolated: 

System FIN Location / panel Name 

LGCIU1 1GA C09 / 49VU LGCIU SYS 1 

LGCIU1 52GA Q34 / 121VU LGCIU SYS 1 GND SPLY 

LGCIU1 58GA R32 / 121VU LGCIU SYS 1 BAT SPLY 

LGCIU2 2GA Q35 / 121VU LGCIU SYS 2 

LGCIU2 59GA R33 / 121VU LGCIU SYS 2 BAT SPLY 

3. Make sure that the aircraft is electrically grounded (Refer to AMM Task 12-34-24-869-002). 

4. Do the preparation procedure as specified in the removal of the LGCIU (Refer to AMM Task 

32-31-71-000-001). 

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Modify the wiring in the FWD Electronics Rack 90VU 

Work Zones and Access Panels 

Zone

120

Access/Work location 

Access Door 811 

Work location Electrical panel 93VU 

Electrical panel 94VU

FIN 5GA1 

1 LGCIU Retain 

2 Put blanking caps on the disconnected connectors. 

FIN 5GA2 

1 LGCIU Retain 

2 Put blanking caps on the disconnected connectors. 

LGCIU Interconnection wiring disconnection: 

Refer to Aircraft Wiring Manual (AWM) 32-31-12 for location. 

- Connector 233VC_A: 

1. Disconnect connector 233VC_A 

2. Remove contacts EN3155-003F2222 from connector 233VC_A cavity 1, 2 

and 3 (please refer to ESPM 20-44-24 §4 for connector and ESPM 20-48-24 

for contact information) using insertion/extraction tool P/N M81969-14-01. 

3. Protect and Stow disconnected cables on the harness per ESPM 20-54-55 

recommendation using shrinking sleeves information (P/N, tooling) depicted 

in ESPM 20-42-12. Size and length to be selected in accordance with 

contact. (E.G:NSA937502-02 or NSA937493-001 or equivalent). 

4. Reconnect connector 233VC_A 

- Connector 213VC_A: 

1. Disconnect connector 213VC_A 

2. Remove contacts EN3155-003F2222 from connector 213VC_A cavity 6, 7 

and 8 (please refer to ESPM 20-44-24 §4 for connector and ESPM 20-48-24 

for contact information) using insertion/extraction tool P/N M81969-14-01. 

3. Protect and Stow disconnected cables on the harness per ESPM 20-54-55 

recommendation using shrinking sleeves information (P/N, tooling) depicted 

in ESPM 20-42-12. Size and length to be selected in accordance with 

contact. (E.G:NSA937502-02 or NSA937493-001 or equivalent). 

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ALERT OPERATORS TRANSMISSION - AOT 

4. Reconnect connector 213VC_A 

Install LGCIU (5GA1 and 5GA2) computers as per AMM Task 32-31-71-400-001. 

Ensure that following LGCIUs Circuit Breakers are enabled: 

System FIN Location / panel Name 

LGCIU1 1GA C09 / 49VU LGCIU SYS 1 

LGCIU1 52GA Q34 / 121VU LGCIU SYS 1 GND SPLY 

LGCIU1 58GA R32 / 121VU LGCIU SYS 1 BAT SPLY 

LGCIU2 2GA Q35 / 121VU LGCIU SYS 2 

LGCIU2 59GA R33 / 121VU LGCIU SYS 2 BAT SPLY 

Test: 

Do the test after the installation of the LGCIU Refer to AMM Task 32-31-71-400-001 and bite test 

refer to AMM Task 32-69-00-740-001-A. 

Close-up: 

References 

Aircraft Maintenance Manual (AMM) Task 32-31-71-400-001 

(a) Make sure that the work areas are clean and clear of tools and other items of equipment. 

(b) Do the close-up procedure as specified in the installation of the LGCIU (Refer to AMM Task 

32-31-71-400-001). 

(c) Return the a/c to the ground configuration in accordance with AMM TASK 32-00-00-860-001-

A01, or AMM TASK 32-00-00-860-001-A. 

4.2.2 MLG DOOR ACTUATOR INSPECTION REQUIREMENTS 

Accomplish the following repetitive inspection every week (not exceeding 8 days): 

GENERAL: 

WARNING: MAKE SURE THAT THE SAFETY DEVICES AND THE WARNING NOTICES ARE 

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IN POSITION BEFORE YOU START A TASK ON OR NEAR: 

- THE FLIGHT CONTROLS 

- THE FLIGHT CONTROL SURFACES 

- THE LANDING GEAR AND THE RELATED DOORS 

- COMPONENTS THAT MOVE. 

MOVEMENT OF COMPONENTS CAN KILL OR INJURE PERSONS. 

WARNING: MAKE SURE THAT THE GROUND SAFETY-LOCKS ARE CORRECTLY INSTALLED 

ON THE LANDING GEAR. 

THIS PREVENTS UNWANTED MOVEMENT OF THE LANDING GEAR. 

WARNING: MAKE SURE THAT YOU OBEY ALL THE WARNINGS AND THE CAUTIONS 

INCLUDED IN THE REFERENCED PROCEDURES. 

NOTE: The procedure that follows is applicable to the LH and RH MLG doors. 

INSPECTION: 

(a) Manually open the LH MLG door by using the door opening control-handle as per AMM 32-

12-00 page block 201, and make sure that: 

- The door opens by gravity alone to at least the point at which the actuator is vertical 

- The movement of the door is smooth and continuous (there are no sudden changes of 

velocity) 

- The door should open from fully closed position to the point at which the door actuator is 

vertical either at, or before, 30 seconds. Timing is to start at the point of initial LG door 

movement away from the "closed" position. 

(b) If the door has not fully opened make sure that: 

- The door can be easily pushed to the fully open position with just one hand 

- The resistance to motion is smooth (hydraulic resistance only) 

(c) With the door fully open, measure the dimension ‘DIM’ shown in the diagram (appendix A). 

- Dimension DIM must be >385mm 

(d) Move the door by hand away from the fully open position for approx 30 degrees and back to 

the fully open position, to make sure that: 

- The resistance to motion is smooth (hydraulic resistance only) 

(e) The LH MLG door actuator must be replaced if any of the checks in steps (a) to (d) fail 

(f) Repeat the work steps (a) to (e) for the RH MLG door 

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4.2.3 FINDINGS 

If a slow door operation or restricted extension is identified during accomplishment of the door actuator 

inspection as per paragraph 4. 2. 2 of this AOT, the following repair procedure must be performed prior 

to further flight of inspected aircraft: 

REPAIR: 

(a) Replacement of the MLG door actuator. 

- Remove the MLG door actuator as per AMM 32-31-35, Page block 401. 

- Install the MLG door actuator as per AMM 32-31-35, Page block 401. 

Report at convenient opportunity to Airbus details of replaced actuator (PN, SN, FC, FH and removal 

reason). 

5. FURTHER INFORMATION 

Independently of this AOT, the recommendations of Ref. 5 AOT and Ref. 6 ISB remain applicable to all 

A320 family aircraft not fitted with MLG door actuator PN 114122014 (pre Ref. 4). 

NOTE: Pending disconnection of LGCIU interconnect wiring as per Para. 4.2.1, the CFDS messages 

mentioned in Ref. 5 AOT will not be generated. However as soon as the interconnect wiring is removed, 

these messages will again be generated allowing to comply with the original Ref. 5 AOT intent to detect 

slow door operation. 

NOTE: Installation of MLG door actuator PN 114122014 (Ref. 4 standard) cancels the requirements of 

this AOT and Ref. 5 AOT and Ref. 6 ISB. 

5.1 FOLLOW-UP PLAN 

It is anticipated that an EASA Airworthiness Directive (AD) will mandate the content of this AOT. 

An Airbus SB will be created to allow restoration of the LGCIUs interconnect wiring for aircraft having 

embodied Ref. 4 introducing the new MLG door actuators PN 114122014. 

5.2 IMPACTED DOCUMENTATION 

None. 

6. AOT APPROVAL 

The technical content of this document is approved under the authority of DOA nr. EASA.21J.031. 

7. REPORTING 

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ALERT OPERATORS TRANSMISSION - AOT 

Questions about this AOT and inspection results with or without findings are to be sent to Airbus 

Customer Services engineering as soon as possible, after the AOT application, to the attention of: 

Jean-Marc LACANETTE 

A380 and A320 Landing Gear Systems - SEEL1 

Customer Support Senior Engineer 

AIRBUS 

Phone: + 33 (0)5 67 19 16 21 

Fax: + 33 (0)5 61 93 32 73 

Mailto:jean-marc.lacanette@airbus.com 

Best Regards. 

Jean-Luc MOUYSSET 

VICE PRESIDENT ENGINEERING SUPPORT 

CUSTOMER SERVICES 

Gilles DE-CEVINS 

VICE PRESIDENT A320 Fam PROGRAMME 

CUSTOMER SERVICES 

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APPENDIX A

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APPENDIX B