# Airbus Alert Operators Transmission A32N025-22 ## Copies (2) Copies the FAA filed in AD dockets on regulations.gov, newest revision first. A newer revision may exist. - Revision 01 ("AOT - A32N025-22 R01 May 10 2023 with appendices"), 9 pages: PDF https://openairdocs.org/files/sha256/c2/d3/c2d392db1513d2c7fd666890d281dc6dba6dd0e7208f4a1915756d3e0e0e5c66; text https://openairdocs.org/service-documents/airbus/aot-a32n025-22/file/c2d392db1513.md. Rights: © Airbus S.A.S. Filed by the FAA in regulations.gov docket FAA-2023-1882; AD 2023-25-05 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - AOT A32N025-22 Dated Feb 24 2022. - with appendices ("AOT A32N025-22 Dated Feb 24 2022. - with appendices"), 9 pages: PDF https://openairdocs.org/files/sha256/8d/9f/8d9fff40e35822d44c7f33a1b6b4065c64b4ac595b2e0ed2306ce49383c614ed; text https://openairdocs.org/service-documents/airbus/aot-a32n025-22/file/8d9fff40e358.md. Rights: © Airbus S.A.S. Filed by the FAA in regulations.gov docket FAA-2022-0389; AD 2022-07-15 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. ## Details - Manufacturer: [Airbus](https://openairdocs.org/service-documents/airbus.md) - Type: Other document (Alert Operators Transmission) - Number: A32N025-22 - Latest revision known: A32N025-22, Revision 01, dated May 10, 2023 (OpenAirDocs) - Page: https://openairdocs.org/service-documents/airbus/aot-a32n025-22 ## ADs that cite it (2) (OpenAirDocs) Newest first, with the revision each names, as OpenAirDocs read it from the AD's text. - [AD 2023-25-05](https://openairdocs.org/ad/2023-25-05.md), effective Feb 7, 2024: Revision 01 - [AD 2022-07-15](https://openairdocs.org/ad/2022-07-15.md), effective May 2, 2022: No revision named Also cited in [1 proposed AD](https://openairdocs.org/service-documents/airbus/aot-a32n025-22/proposed.md). ## Text (9 pages) Revision 01, the newest copy. Rights: © Airbus S.A.S. Filed by the FAA in regulations.gov docket FAA-2023-1882; AD 2023-25-05 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. Some pages are OCR from a scan. OCR can misread letters and numbers. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N025-22 Rev 01 Page 1 of 6 Date: 10-MAY-2023 C80_AOT_FM1104649_v8.0 © AIRBUS S.A.S. 2023. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT SUBJECT: ATA 32 – A320FAM BSCU P/N E21327307 increased rate of BRAKES SYS 1(2) FAULT detected prior to delivery AIRCRAFT TYPE: A319, A320, A321 OUR REF.: A32N025-22 Rev 01 dated 10-MAY-2023 OUR PREVIOUS REF.: A32N025-22 Rev 00 dated 24-FEB-2022 EFFECTIVITY DATE: 15-MAY-2023 0. REASON FOR REVISION This AOT is revised to reflect the new content of EASA AD 2023-0093 issued on the 05-MAY-2023. The revised paragraphs are indicated between ***BEG REV*** and ***END REV***. 1. AIRCRAFT AFFECTED ***BEG REV*** ALL A319-151N, A319-153N, A319-171N, A320-251N, A320-252N, A320-253N, A320-271N, A320- 272N, A320-273N, A321-251N, A321-251NX, A321-252N, A321-252NX, A321-253N, A321-253NX, A321-271N, A321-271NX, A321-272N, A321-272NXorganized into the following groups: Group 1a: Aircraft equipped with BSCU P/N E21327307 and with unsuppressed relays (P/N E0244- 28A0) installed at the 24GG/25GG FIN locations Group 1b: Aircraft equipped with a BSCU having a part number different than P/N E21327307 and with unsuppressed relays (P/N E0244-28A0) installed at the 24GG/25GG FIN locations Group 2: Aircraft that are neither in group 1a nor group 1b Note: All aircraft within the effectivity list of AOT A32N030-23 are considered as if having unsuppressed relays (group 1a or 1b) until the AOT A32N030-23 inspection / corrective actions (if necessary) are performed. Note: All CEO aircraft have been removed from the effectivity of this AOT at revision 01 since all CEO fall into group 2. ***END REV*** 2. REFERENCED DOCUMENTATION 2.1 APPENDIX ***BEG REV*** Appendix 1: Table of Faults Signatures Appendix 2: Flowchart Appendix 3: List of acronyms Note: The appendix list has been updated since Rev. 00 of this AOT as the TSM tasks previously listed have now been updated in TSM Aug 2022 revision. ***END REV*** 2.2 REFERENCES ***BEG REV*** ### Page 2 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N025-22 Rev 01 Page 2 of 6 Date: 10-MAY-2023 C80_AOT_FM1104649_v8.0 © AIRBUS S.A.S. 2023. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT Reference 1: TFU 32.42.00184 A320FAM BSCU P/N E21327307 increased rate of BRAKES SYS 1(2) FAULT detected prior to delivery Reference 2: FOT 999.0010/22 rev 03 ATA 32 – MMEL AND FCOM/QRH UPDATE FOR AIRCRAFT EQUIPPED WITH BSCU P/N E21327307 Reference 3: AMM TASK 32-42-34-000-001-A Removal of the Braking/Steering Control Unit (BSCU) Reference 4: AMM TASK 32-42-34-400-001-A Installation of the Braking/Steering Control Unit (BSCU) Reference 5: AMM TASK 32-46-00-740-003-A BITE Test of the BSCU - LRU Identification Reference 6: Safran Service Letter E21327-32-3504 Reference 7: EASA AD 2023-0093 (superseding EASA AD 2022-0032R1) Reference 8: FAA AD 2022-07-15 issued 29-Mar-2022 equivalent AD EASA 2022-0032 Reference 9: Airbus SB A320-92-1149 Reference 10: Airbus AOT A32N030-23 rev 00 ATA 32 – A320FAM incorrect relay installation at FIN 24GG/25GG during Manufacturing ***END REV*** 3. REASON 3.1 FACTS ***BEG REV*** Airbus informs the operators that an increase of the rate of Braking & Steering Control Unit (BSCU) fault has been detected during the tests performed in A320FAM Flight Line prior to delivery. This increased rate is only reported on aircraft equipped with the latest BSCU standard (P/N E21327307) and with unsuppressed relays (P/N E0244-28A0) installed on the 24GG/25GG positions. ***END REV*** These faults correspond to a loss of the affected BSCU channel(s): Single channel loss: In these cases, BSCU faults are detected and indicated in the cockpit via a BRAKES SYS 1(2) FAULT ECAM alert with no maintenance message coming from the subject BSCU channel. In this scenario there is no impact on Aircraft braking - normal braking remains available. Dual channel loss: While in most of the cases observed only one channel was affected, three cases of dual BSCU channel loss were also reported. In these cases, BRAKES A/SKID N/WS FAULT ECAM alerts were displayed and associated with NO DATA FROM BSCU 1+2 messages triggered by the SDAC. Normal braking, Anti-skid and Nose Wheel Steering were inoperative and the aircraft were safely stopped using Alternate Braking without anti-skid and Thrust Reversers. 3.2 HISTORY/BACKGROUND ***BEG REV*** BSCU P/N E21327307 (MOD 165148) was developed to answer to the obsolescence of some components present in BSCU P/N E21327107 / E21327007. Unsuppressed relays (P/N E0244-28A0) were introduced on A320FAM NEO aircraft via MOD 161939. Since June 2022, these relays are now replaced in production by suppressed relays (P/N E0669D28A0) via MOD 171984. ### Page 3 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N025-22 Rev 01 Page 3 of 6 Date: 10-MAY-2023 C80_AOT_FM1104649_v8.0 © AIRBUS S.A.S. 2023. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT A Modification Service Bulletin SB 92-1149 [ref.9] was first issued in October 2022 and provides guidance to retrofit in-service aircraft and install suppressed relays. Due to a quality escape, some aircraft post MOD 171984 may have been delivered with unsuppressed relays installed, AOT A32N030-23 [ref. 10] has been issued in March 2023 to inspect the potentially affected aircraft and, in case of finding, put the aircraft back to the correct configuration. ***END REV*** 3.3 ROOT CAUSE ***BEG REV*** The root cause investigation concluded that these failures were due to a combination of the following: An increased susceptibility of BSCU -307 to external interferences. During the re-design of the BSCU (P/N E21327307), resistor R438 was removed from the CPU board. This led to the BSCU -307 being more susceptible to external interferences. High voltage interferences on some signals going to the BSCU. These high voltages are generated at the closure of the unsuppressed relays (P/N E0244-28A0) installed at 24GG & 25GG FIN location. ***END REV*** 3.4 INVESTIGATION See paragraph §3.3 3.5 CONSEQUENCES The loss of a single BSCU channel will put the remaining valid channel in control. This second BSCU channel will then perform the Normal Braking, Anti-skid, Autobrake and Nose Wheel Steering Functions. There is no impact on Aircraft braking. If both BSCU channels are lost, then the braking system will swap to the Alternate Braking Mode without Anti-skid. In that case the Normal Braking, Anti-skid, Autobrake and the Nose Wheel Steering functions will be lost and aircraft stopping distance will be increased. The Parking Brake and other deceleration means (such as thrust reverser) are not affected by this issue. 4. OBJECTIVES OF THIS AOT ***BEG REV*** To mitigate the risks that a BSCU affected by this issue could remain on aircraft and experience a dual BSCU channel loss, this AOT demands the following: For aircraft in group 1a: if one of the specific fault signatures listed in appendix 1 is triggered during flight phase 08 or 09, this AOT requires the replacement of the affected BSCU by a serviceable unit For aircraft in group 1b: from the effective date of this AOT revision, this AOT prohibits the installation of a BSCU P/N E21327307. In addition, for group 1a aircraft, in order to mitigate the impact on stopping distance during deceleration phases and to cover the operational aspect of the complete mitigation set, this AOT is to be used in association with FCOM/QRH and MMEL update as explained in FOT 999.0010/22 [ref.2]. ### Page 4 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N025-22 Rev 01 Page 4 of 6 Date: 10-MAY-2023 C80_AOT_FM1104649_v8.0 © AIRBUS S.A.S. 2023. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT This new AOT revision aims to be in line with EASA AD content and alleviate the restrictions for the aircrafts in group 2. ***END REV*** 5. MAINTENANCE PROCEDURE NOTE: This AOT is classified mandatory or expected to be classified mandatory by an Airworthiness Directive (AD). If the instructions of this AOT are marked as Required for Compliance (RC), the operator must follow the instructions as indicated. These instructions are introduced by “in accordance with”. NOTE: The instructions of this AOT include procedures given in other documents or in other sections of the AOT. If the instructions of this AOT are NOT marked as Required for Compliance (RC), the operator can use an alternative procedure accepted by his/her local authority. These instructions are introduced by “refer to”. NOTE: When this AOT gives the access or close-up instructions with no return to service tests, the operator can adapt these instructions to add flexibility to the maintenance operations. The technical intent of this AOT must comply with the set parameters. 5.1 PLANNING (-RC) *** BEG REV *** For Group 1a: If one of the Fault Signatures listed in the table of Appendix 1 is triggered during Flight Phase 8 or Flight Phase 9, the replacement of the BSCU shall be performed before next flight. For Group 1b: Starting from this AOT rev. effectivity date, the installation restriction provided in this AOT shall be applied to all aircraft of group 1b. *** END REV *** 5.2 MANPOWER Estimated time to identify BSCU Part Number is 0.5 Man Hours. Estimated time to replace a BSCU from an A320FAM is 2,5 Man Hours. 5.3 ACCESS Access for Replacement of the BSCU P/N E21327307 (in accordance with AMM TASK 32-42-34-000- 001-A [ref.3] & TASK 32-42-34-400-001-A [ref.4]) Get Access to the Avionics Compartment: (1) Put the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE in position at the access door 811. (2) Open the access door 811. 5.4 INSPECTION N/A 5.5 FINDINGS N/A ### Page 5 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N025-22 Rev 01 Page 5 of 6 Date: 10-MAY-2023 C80_AOT_FM1104649_v8.0 © AIRBUS S.A.S. 2023. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT 5.6 INSTRUCTIONS (-RC) *** BEG REV *** The instructions below are provided for each group of aircraft as defined in §1. To identify the P/N of the BSCU installed on a given aircraft operator can use one of the following means: Inspection of the maintenance records as long as they are complete OR Perform a LRU identification from the MCDU (ref. AMM task 32-46-00-740-003-A [ref.5]) OR Visual inspection of the P/N on the BSCU itself To identify the P/N of the relay installed on the 24GG/25GG FIN locations of a given aircraft operator can use one of the following means: Inspection of the maintenance records as long as they are complete OR Visual inspection of the P/N on the 24GG/25GG FIN locations Note: Unsuppressed relays have P/N E0244-28A0, Suppressed relays have P/N E0669D280. Please refer to AOT A32N030-23 [Ref. 10] to identify the aircraft post MOD 171984 which are potentially equipped with unsuppressed relays due to Quality Escape. For Aircraft in group 1a: If, during any flight, a BSCU fault signature as defined in the AOT Appendix 1 is triggered during flight phase 8 or 9 then proceed with the immediate replacement of the BSCU P/N E21327307 installed (in accordance with AMM task 32-42-34-000-001-A [ref.3] & AMM task 32-42-34-400- 001-A [ref.4] ) prior to any other troubleshooting action (including fault confirmation). Note: if a spare BSCU -006, -106, -007 or -107 is used then the aircraft will be considered as part of group 1b once the replacement of the BSCU is completed. If a spare BSCU -307 is used then the aircraft will remain in group 1a. Place the removed BSCU P/N E21327307 into quarantine and ship it to one of Safran Landing Systems repair stations listed below with the PFR showing the fault attached: DALLAS station: Safran Electronics & Defense, Avionics USA, LLC. 2802 Safran Drive Grand-Prairie TX 75052 Grand-Prairie - USA MASSY Station: Safran Electronics & Defense DSC MRO 13, rue Ampère 91300 MASSY - FRANCE SINGAPORE Station: Safran Electronics & Defense Services Asia Pte Ltd 26 Changi North Rise 498756 Singapore MOLSHEIM Station: Safran Landing Systems 22A route ECOSPACE ZONE MRO 67129 MOLSHEIM - FRANCE Contact Airbus to report the removal and potential further instructions. ### Page 6 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N025-22 Rev 01 Page 6 of 6 Date: 10-MAY-2023 C80_AOT_FM1104649_v8.0 © AIRBUS S.A.S. 2023. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT For Aircraft in group 1b: From the effectivity date of this AOT revision, do not install BSCU P/N E21327307. For aircraft in group 2: No further action in the frame of this AOT *** END REV *** 5.7 SPARES AND TOOLING For logistic & commercial policy please refer to Safran Service Letter E21327-32-3504 [ref.6] PFR showing the Fault Signature will be required for the commercial policy to be applied. 6. ADDITIONAL INFORMATION 6.1 FOLLOW-UP PLAN Follow up of the topic will be provided through TFU 32.42.00184 [ref.1] (In case action is to be amended, subject AOT will be up-issued). 7. AOT APPROVAL The technical content of this document is approved under the authority of the DOA ref.EASA.21J.031. 8. REPORTING Address your inspection results (with or without findings) to Airbus Customer Services through the generic e-mail address inspection.results@airbus.com. Refer to the latest reporting policy (Ref in the OIT 999.0018/16). Give the AOT reference in the mail title, as follows: AOT ref. A32N025-22 Inspection Result You can address your questions about this AOT to Airbus Customer Services through TechRequest on Airbus World, selecting Maintenance & Engineering Domain, Engineering Support Section and ATA 32-42. Best Regards, Ahmed CHABBOUH SENIOR DIRECTOR IN-SERVICE ENGINEERING CUSTOMER CARE CENTER Jean-Pierre GOMEZ VICE PRESIDENT A320FAM PROGRAMME CUSTOMER SERVICES ### Page 7 ALERT OPERATORS TRANSMISSION - AOT Appendix 1 – Table of Fault Signatures AOT ref: A32N025-22 Rev 01 Page A1 Date: MAY-2023 C80_AOT_FM1104649_v8.0© AIRBUS S.A.S. 2022. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT A Fault Signature is composed of 1 ECAM Warning + 1 Maintenance Message coming from a source. In the table below one line is attributed to each fault signature related to AOT A32N025-22. ECAM Warning Maintenance Message Source Flight Phases BRAKES SYS 1 FAULT NO BSCU 1 DATA CFDS 08 or 09 BRAKES SYS 2 FAULT NO BSCU 2 DATA CFDS 08 or 09 BRAKES A/SKID N/WS FAULT AFS: BSCU 1 AFS 08 or 09 BRAKES A/SKID N/WS FAULT AFS: BSCU 2 AFS 08 or 09 BRAKES A/SKID N/WS FAULT NO BSCU 1 DATA CFDS 08 or 09 BRAKES A/SKID N/WS FAULT NO BSCU 2 DATA CFDS 08 or 09 BRAKES A/SKID N/WS FAULT SDAC1: NO DATA FROM BSCU 1+2 ECAM 1 08 or 09 BRAKES A/SKID N/WS FAULT SDAC2: NO DATA FROM BSCU 1+2 ECAM 2 08 or 09 ### Page 8 (OCR) AIRBUS ALERT OPERATORS TRANSMISSION - AOT Appendix 2 - Flowchart Start Is unsuppressed No relay (P/N E0244-28A0) installed on 24GG/25GG FIN location? Yes Is BSCU No P/N E21327307 installed on subject A/C? Yes Aircraft is in group 1a Aircraft is in group 1b Aircraft is in group 2 Yes Is the triggered No Fault Signature listed in table of Appendix 12 Yes Was the Fault No Do not install BSCU P/N recorded in PFR in Flight Phase 8 or Flight Phase 9? E21327307 Yes Replace BSCU before Troubleshoot the fault next flight using applicable TSM task No further action in the frame of this AOT AOT ref: A32N025-22 Rev 01 Page A2 Date: MAY-2023 C80 AOT CUMA9 8 0D AIRBUS SA.S, 2022 AL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY ### Page 9 ALERT OPERATORS TRANSMISSION - AOT Appendix 3 – List of Acronyms used AOT ref: A32N025-22 Rev 01 Page A3 Date: MAY-2023 C80_AOT_FM1104649_v8.0© AIRBUS S.A.S. 2022. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT Acronym Signification AD Airworthiness Directive AFS Auto Flight System AMM Aircraft Maintenance Manual AOT Alert Operators Transmission BSCU Braking & Steering Control Unit CFDIU Centralized Fault Display Interface Unit CFDS Centralized Fault Display System ECAM Electronic Centralized Aircraft Monitoring FIN Functional Item Number FOT Flight Operations Transmission LRU Line Replaceable Unit MMEL Master Minimum Equipment List PFR Post Flight Report RTO Rejected Take Off SDAC System Data Acquisition Concentrator TFU Technical Follow Up TSM Troubleshooting Manual --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain, except the copies of manufacturers’ service documents, which belong to their rights holders.