# Airbus All Operators Transmission A32N024-21: No revision named - Rights: © Airbus S.A.S. Filed by the FAA in regulations.gov docket FAA-2022-1295, the docket of AD 2023-01-01. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Airbus All Operators Transmission A32N024-21](https://openairdocs.org/service-documents/airbus/aot-a32n024-21.md) - Title as filed: AOT A32N024-21 - Pages: 19 - PDF: https://openairdocs.org/files/sha256/de/ec/deecc2a7faf29eefe51265feda25f717d07bda025317030fbcd361728b0854db - Page: https://openairdocs.org/service-documents/airbus/aot-a32n024-21/file/deecc2a7faf2 ## Text Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 CUSTOMER SERVICES DIRECTORATE 2 ROND POINT EMILE DEWOITINE 31700 BLAGNAC FRANCE TELEPHONE + 33 (0)5 61 93 33 33 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 1 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT SUBJECT: ATA 32 – NLG and MLG Sliding Tube Inspection - Overheat damage during overhaul AIRCRAFT TYPE: A318, A319, A320, A321 OUR REF.: A32N024-21 Rev 00 dated 07-OCT-2021 EFFECTIVITY DATE: 21 October 2021 1. AIRCRAFT AFFECTED All A318, A319, A320, A321 Aircraft. A320 Family NEO Aircraft are not affected by the content of this AOT. 2. REFERENCED DOCUMENTATION 2.1 APPENDIX - Appendix 1: List of suspected NLG sliding tubes SN. - Appendix 2: List of suspected MLG sliding tubes SN. - Appendix 3: Inspection reporting sheet (NLG). - Appendix 4: Inspection reporting sheet (MLG). 2.2 REFERENCES - Ref.1: Safran PCS-2110 “Electrolytic Hard Chromium Plating of Steels“ - Ref.2: Safran PCS-3100 “Magnetic Particle Inspection” - Ref.3: Safran PCS-3600 “Etch Inspection of High Strength Steel Parts” - Ref.4: Safran PCS-3700 “Barkhausen Noise Inspection“ - Ref.5: NTM 51-70-00 “Magnetic Particle” - Ref.6: AMM Task 07-11-00-581-001-A “Lifting for Aircraft Maintenance Operations” - Ref.7: AMM Task 07-11-00-581-003-A “Lifting of the Aircraft at the Forward Jacking Point” - Ref.8: AMM Task 07-11-00-586-002-A “Lowering of the Aircraft for Maintenance Operations” - Ref.9: AMM Task 07-11-00-586-001-A “Lowering of the Aircraft at Forward Jacking Point” - Ref.10: AMM Task 32-11-00-100-002 “Cleaning of the Main Landing Gear” - Ref.11: AMM Task 32-21-00-100-002 “Clean of the nose landing gear” - Ref.12: AMM Task 32-21-13-000-001-A “Removal of the NLG Shock Absorber Assy” - Ref.13: AMM Task 32-21-13-000-001-A01 “Removal of the NLG Shock Absorber Assy (with nose jacking only)” - Ref.14: AMM Task 32-21-13-400-001-A “Installation of the NLG Shock Absorber Assy” - Ref.15: AMM Task 32-21-13-400-001-A01 “Installation of the NLG Shock Absorber Assy (with nose jacking only)” - Ref.16: AMM Task 32-11-13-000-001-A “Removal of the MLG Shock Absorber” - Ref.17: AMM Task 32-11-13-400-001-A “Installation of the MLG Shock Absorber” - Ref.18: AMM Task 32-11-13-000-004-A “Removal of the Sliding Tube Sub-Assy of the MLG Shock Absorber” - Ref.19: AMM Task 32-11-13-400-004-A “Installation of the Sliding Tube Sub-Assy of the MLG Shock Absorber” 3. REASON The purpose of this AOT is to inform the operators of a fracture of a NLG sliding tube in service. Investigation has revealed that the rupture originated from an overheat damage to base metal due to an incorrect application of a repair on the chromium plated diameter of the sliding tube during the last overhaul. This AOT recommends the operators with suspected parts as per Appendix 1 and Appendix 2 to perform: - A Detailed Visual Inspection (DVI) of the sliding tube visible chrome surface with the aircraft on jacks. ### Page 2 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 2 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT - A Magnetic Particle Inspection (MPI) and a Barkhausen Noise Inspection (BNI) of the sliding tube entire chrome surface. - As a terminating action, a Magnetic Particle Inspection (MPI) and an Acid Etch inspection on the base metal of the suspected sliding tube to ensure it is free from any crack or overheat damage. 3.1 FACTS An A320 aircraft experienced a NLG collapse during a 180 deg. turn at the end of the runway before take- off. The NLG sliding tube fractured on the lower part of the chrome surface area. Subsequent laboratory investigation has revealed that the rupture originated from an overheat damage to the sliding tube base metal. From this overheat damage a crack initiated and propagated up to final rupture of the sliding tube. Investigation has shown that the overheat damage to the base metal is the result of an incorrect application of a repair on the chromium plated diameter of the sliding tube during the last NLG overhaul. Supplementary investigation has been launched with the Maintenance Repair and Overhaul Organisation (MRO) that performed the overhaul. As a result of this investigation, it has been established that the thermal abuse on the sliding tube is consistent with an incident on a specific machine used for grinding of the chrome during a specific period of time. It was identified that a limited number of NLG sliding tubes and MLG sliding tubes has had the chrome repaired on the same machine during the suspected period of time (refer to the list in Appendix 1 and Appendix 2). As a precaution, Airbus recommend the following inspections of this batch of NLG and MLG sliding tubes repaired by this MRO to ensure that they are free from any crack and overheat damage: - Within the next 250FC from the effectivity date of this AOT, a Detailed Visual Inspection (DVI) of the sliding tube chrome surface with the aircraft lifted on jacks to ensure there is no visible crack on the part, and - Within the next 750FC from the effectivity date of this AOT, a Magnetic Particle Inspection (MPI) of the entire sliding tube chrome surface to ensure there is no crack and a Barkhausen Noise Inspection (BNI) to detect potential overheat damage, and - At the next landing gear overhaul, without exceeding 20000FC or 10 year after the last Landing Gear overhaul (whichever occur first), a Magnetic Particle Inspection (MPI) and Acid Etch inspection of the sliding tube base material to ensure it is free from any crack or overheat damage. This inspection will require to send the sliding tube to a shop to remove the chrome plating. 3.2 CONSEQUENCES Undetected overheat damage to the NLG sliding tube or MLG sliding tube could lead to the opening of a crack and ultimately to the rupture of the sliding tube. 3.3 AIM The aim of this AOT is to recommend operators with suspected NLG sliding tubes as per Appendix 1 and MLG sliding tubes as per Appendix 2 to perform the following Inspections: - A DVI inspection for cracks of the NLG and MLG sliding tube visible chrome surface with the aircraft on jacks. ### Page 3 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 3 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT - A MPI inspection for cracks and BNI inspection for overheat damage of the NLG and MLG sliding tube entire chrome surface. - A MPI and Acid Etch inspection of the base material of the NLG and MLG sliding tube to check for any crack or overheat damage. 4. SHORT TERM ACTION NOTE: This AOT is classified mandatory or expected to be classified mandatory by an Airworthiness Directive (AD). The accomplishment instructions marked as Required for Compliance (RC) must be done to comply with the AD. “RC” is indicating these paragraphs accordingly. NOTE: The accomplishment instructions of this AOT include procedures given in other documents or in other sections of the AOT. When the words ’refer to’ are used and the operator has a procedure accepted by the local authority he belongs to, the accepted alternative procedure can be used. When the words ’in accordance with’ are used then the given procedure must be followed. NOTE: The access and close-up instructions, not comprising return to service tests, in this AOT do not constitute or affect the technical intent of the AOT. Operators can therefore, as deemed necessary, omit or add access and/or close-up steps to add flexibility to their maintenance operations as long as the technical intent of the AOT is met within the set parameters. 4.1 PLANNING AND MANPOWER 4.1.1 ACCOMPLISHMENT TIMESCALE - (RC) a) At the earliest opportunity without exceeding 250FC from the effectivity date of this AOT: Do a check of the Landing Gear and Aircraft maintenance records or physical check as per Paragraph 4.2.2.1, to determine if NLG or MLG sliding tubes are part of the suspected population. And b) At the earliest opportunity without exceeding 250FC from the effectivity date of this AOT: Perform a Detailed Visual Inspection (DVI) on the visible chrome surface of the suspected NLG and MLG sliding tubes with the aircraft on jacks as per the procedure of Paragraph 4.2.2.2 and 4.2.2.5., And c) At the earliest opportunity without exceeding 750FC from the effectivity date of this AOT: Perform a Magnetic Particle Inspection (MPI) and Barkhausen Noise Inspection (BNI) on the entire chrome surface of the suspected NLG and MLG sliding tubes as per the procedure of Paragraph 4.2.2.3 and 4.2.2.6, And d) As a terminating action, at the next Landing Gear overhaul without exceeding 20000FC or 10 year after the last Landing Gear overhaul (whichever occurs first): Perform a Magnetic Particle Inspection (MPI) and an Acid Etch inspection on the base material of the suspected NLG and MLG sliding tubes as per the procedure of Paragraph 4.2.2.4 and 4.2.2.7. NOTE: ### Page 4 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 4 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT - Completion of the MPI and Acid Etch inspections as per paragraph d) but within 250FC cancels the requirement for DVI inspection as per paragraph b) and MPI/BNI inspection as per paragraph c). - Completion of the MPI and Acid Etch inspections as per paragraph d) but within 750FC cancels the requirement for MPI/BNI inspection as per paragraph c). - Completion of the MPI/BNI inspection as per paragraph c) but within 250FC cancels the requirement for DVI inspection as per paragraph b). 4.1.2 MANPOWER The estimated time to perform the access and the DVI inspection of the NLG sliding tube as per Paragraph 4.2.2.2 is 5 Man hours. The estimated time to perform the access and the DVI inspection of the MLG sliding tube as per Paragraph 4.2.2.5 is 5 Man hours. The estimated time to perform the access and the MPI and BNI inspection of the NLG sliding tube as per Paragraph 4.2.2.3 is 15 Man hours. The estimated time to perform the access and the MPI and BNI inspection of the MLG sliding tube as per Paragraph 4.2.2.6 is 25 Man hours. The Acid Etch inspection and MPI of the NLG and MLG sliding tube base metal as per para. 4.2.2.4 and 4.2.2.7 must be done in shop as it requires the prior removal of the chrome plating. 4.2 DESCRIPTION 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 A 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 Ref. ESPM 20-55-00. Standard Practices a) For the identification of zones, refer to AMM 06-20-00, Page Block 001. b) To torque tighten the standard threaded fasteners, refer to AMM Task 20-21-11-911-001. c) Tag all the parts you must remove and retain to make the subsequent installation easier. d) Put all the retained hardware in identified plastic bags and attach the bags to the related unit. e) For wire locking, refer to AMM Task 20-11-11-911-001. f) Do a check of the electrical connectors before you connect them, refer to ESPM 20-52-10. g) During maintenance, it is mandatory to ground (earth) the aircraft when you do maintenance tasks with equipment that is externally supplied from a domestic or industrial network, refer to AMM TASK 12-34-24-869-002-A. ### Page 5 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 5 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT WARNING: BEFORE YOU LIFT THE AIRCRAFT WITH JACKS, MAKE SURE THAT THE WEIGHT OF THE FUEL IS EQUAL ON THE TWO SIDES OF THE AIRCRAFT CENTERLINE. WARNING: MAKE SURE THAT THE AIRCRAFT IS STABLE: -BEFORE YOU PUT IT ON JACKS - DURING ALL THE TIME IT STAYS ON JACKS. WARNING: MAKE SURE THAT THE GROUND SAFETY-LOCKS ARE IN POSITION ON THE LANDING GEAR. THIS WILL PREVENT UNWANTED MOVEMENT OF THE LANDING GEAR, AND THUS POSSIBLE INJURY TO PERSONS AND DAMAGE TO THE AIRCRAFT AND/OR EQUIPMENT. WARNING: WHEN YOU DO THE LEVELING/LIFTING OR LOWERING OF THE AIRCRAFT, MAKE SURE THAT: - YOU USE THE CORRECT LIFTING/LOWERING EQUIPMENT FOR THE CONDITIONS - THE PERSONS WHO OPERATE THE LIFTING/LOWERING EQUIPMENT HAVE THE CORRECT TRAINING AND KNOWLEDGE - THE NECESSARY SAFETY AREA IS IDENTIFIED - THERE ARE NO UNWANTED PERSONS OR EQUIPMENT IN THIS AREA - THERE IS NO WORK IN PROGRESS ON THE AIRCRAFT. IF YOU DO NOT OBEY THESE PRECAUTIONS, INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT CAN OCCUR. WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS. CAUTION: YOU MUST NOT LIFT THE AIRCRAFT WITH THE SAFETY STAY. CAUTION: DO NOT USE THE TAIL SAFETY STAY WHEN THE AIRCRAFT IS ON ITS WHEELS. WARNING: MAKE SURE THAT THE SAFETY DEVICES AND THE WARNING NOTICES ARE IN POSITION BEFORE YOU START A TASK ON OR NEAR: -THE FLIGHT CONTROLS -THE FLIGHT CONTROL SURFACES -THE LANDING GEAR AND RELATED DOORS -COMPONENTS THAT MOVE. MOVEMENT OF COMPONENTS CAN KILL OR CAUSE INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT. WARNING: MAKE SURE THAT, IF THE LANDING GEAR DOORS ARE OPEN, THEY ARE SAFETIED BEFORE YOU INSTALL THE LANDING GEAR SAFETY-DEVICES. IF THE LANDING GEAR DOORS ARE OPEN BUT NOT SAFETIED THERE IS A RISK THAT THEY CAN CLOSE AND CAUSE INJURY. WARNING: MAKE SURE THAT THE TRAVEL RANGES OF THE FLIGHT CONTROLS SURFACES ARE CLEAR. MOVEMENT OF FLIGHT CONTROLS CAN CAUSE INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT. WARNING: MAKE SURE THAT THE CONTROLS AGREE WITH THE POSITION OF THE ITEMS THEY OPERATE BEFORE YOU PRESSURIZE A HYDRAULIC SYSTEM. UNWANTED MOVEMENT OF HYDRAULICALLY OPERATED ITEMS CAN CAUSE SERIOUS INJURY AND/OR DAMAGE. WARNING: PRESSURIZE ONLY THE HYDRAULIC SYSTEM(S) THAT IS (ARE) NECESSARY FOR THE TASK. ISOLATE THE OTHER HYDRAULIC SYSTEM(S) BEFORE YOU SUPPLY HYDRAULIC POWER TO THE AIRCRAFT. WARNING: MAKE SURE THAT ALL THE CIRCUITS IN MAINTENANCE ARE ISOLATED BEFORE YOU SUPPLY ELECTRICAL POWER TO THE AIRCRAFT. UNWANTED ELECTRICAL POWER CAN BE DANGEROUS. WARNING: DO NOT LET COMPRESSED GAS TOUCH YOUR SKIN. THE GAS CAN GO THROUGH THE SKIN AND MAKE BUBBLES IN THE BLOOD. THIS CONDITION CAN KILL YOU. ### Page 6 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 6 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT WARNING: USE PROTECTIVE GOGGLES AND GLOVES WHEN YOU REMOVE OR INSTALL LOCKWIRE. EACH TIME YOU CUT LOCKWIRE, REMOVE AND DISCARD IT IMMEDIATELY. LOOSE LOCKWIRE CAN CUT YOU OR MAKE YOU BLIND, AND/OR CAN CAUSE DAMAGE. WARNING: USE PROTECTIVE GOGGLES WHEN YOU REMOVE OR INSTALL A COTTER PIN. EACH TIME YOU REMOVE A COTTER PIN DURING THE TASK, DISCARD IT IMMEDIATELY. A LOOSE COTTER PIN CAN CUT YOU OR MAKE YOU BLIND. WARNING: BE CAREFUL WHEN YOU REMOVE OR INSTALL THE MLG SHOCK-ABSORBER. ITS WEIGHT CAN BE AS MUCH AS 118kg (260lb). WARNING: DO NOT GET THE FLUID ON YOUR SKIN OR IN YOUR EYES. IF YOU DO: - FLUSH IT AWAY WITH CLEAN WATER -GET MEDICAL AID. CAUTION: MAKE SURE THAT THE FLUID DOES NOT STAY ON THE AIRCRAFT STRUCTURE. IF THE FLUID GETS ON THE AIRCRAFT STRUCTURE, WASH IT OFF IMMEDIATELY WITH SOAP AND WATER. 4.2.1 ACCESS For access, refer to paragraph 4.2.2 and the applicable AMM tasks depending on the inspection to perform. 4.2.2 INSPECTION REQUIREMENTS - (RC) 4.2.2.1 Do a check of the Landing Gear and Aircraft maintenance records NLG sliding tubes Do a check of the Landing Gear and Aircraft maintenance records or physical check on the part to identify the NLG sliding tube Part Numbers (PN) and Serial Numbers (SN), and compare with the Part Numbers (PN) and Serial Numbers (SN) listed in Appendix 1 to determine if NLG sliding tubes are part of the suspected population. If the NLG sliding tubes Serial Numbers (SN) are not listed in Appendix 1, no further action is required. If the NLG sliding tubes Serial Numbers (SN) are listed in Appendix 1, then perform the following inspections: - Within the next 250FC from the effectivity date of this AOT, a DVI inspection for cracks of the NLG sliding tube visible chrome surface with the aircraft on jacks as per paragraph 4.2.2.2. - Within the next 750FC from the effectivity date of this AOT, a MPI inspection and BNI inspection of the NLG sliding tube entire chrome surface as per paragraph 4.2.2.3. - At the next NLG overhaul, a MPI and Acid Etch inspection of the base material of the NLG sliding tube to check for any crack or overheat damage per paragraph 4.2.2.4. MLG sliding tubes Do a check of the Landing Gear and Aircraft maintenance records or physical check on the part to identify the RH and LH MLG sliding tube Part Numbers (PN) and Serial Numbers (SN), and compare with the Part Numbers (PN) and Serial Numbers (SN) listed in Appendix 2, to determine if MLG sliding tubes are part of the suspected population. If the MLG sliding tubes Serial Numbers (SN) are not listed in Appendix 2, no further action is required. ### Page 7 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 7 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT If the MLG sliding tubes Serial Numbers (SN) are listed in Appendix 2, then perform the following inspections: - Within the next 250FC from the effectivity date of this AOT, a DVI inspection for cracks of the MLG sliding tube visible chrome surface with the aircraft on jacks as per paragraph 4.2.2.5. - Within the next 750FC from the effectivity date of this AOT, a MPI inspection and BNI inspection of the MLG sliding tube entire chrome surface as per paragraph 4.2.2.6. - At the next NLG overhaul, a MPI and Acid Etch inspection of the base material of the MLG sliding tube to check for any crack or overheat damage per paragraph 4.2.2.7. 4.2.2.2 Do a DVI inspection of the NLG sliding tube Preparation a) Lift the aircraft on jacks, refer to AMM Task 07-11-00-581-001-A or AMM Task 07-11-00-581- 003-A. Procedure a) Clean the visible chromed surface of the NLG sliding tube, refer to AMM Task 32-21-00-100- 002. b) Do a DVI of the NLG sliding tube visible chromed-surface with the aircraft lifted on jacks in accordance with Fig. 1. If cracks are found: (1) Replace the cracked NLG Sliding Tube before the next flight, refer to appropriate CMM; or replace the NLG shock absorber, refer to AMM Task 32-21-13-000-001-A “Removal of the NLG Shock Absorber Assy” or AMM Task 32-21-13-000-001-A01 “Removal of the NLG Shock Absorber Assy with nose jacking only”. (2) Contact AIRBUS immediately. (3) Put the removed parts in quarantine pending Airbus instructions. Figure 1: NLG sliding tube Area for the DVI inspection (Aircraft on Jacks) ### Page 8 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 8 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT If no cracks are found: (1) Lower the aircraft and put the aircraft back to its initial configuration, refer to AMM Task 07- 11-00-586-002-A or AMM Task 07-11-00-586-001-A. c) Inspection Reporting sheet (Appendix 3) shall be filled and returned to Airbus within 1 month counted from the inspection date even if nil finding. 4.2.2.3 Do a MPI and BNI inspection of the NLG sliding tube Preparation a) Remove the NLG Shock Absorber, refer to AMM Task 32-21-13-000-001-A “Removal of the NLG Shock Absorber Assy” or AMM task 32-21-13-000-001-A01 “Removal of the NLG Shock Absorber Assy with nose jacking only”. Procedure – Magnetic Particle Inspection (MPI) a) Do an MPI of the NLG sliding tube chromed-surface in accordance with Fig. 2: refer to Non Destructive Test Manual (NTM) 51-70-00. If cracks are found: (1) Replace the cracked NLG Sliding Tube before the next flight, refer to appropriate CMM; or replace the NLG shock absorber, refer to AMM Task 32-21-13-000-001-A “Removal of the NLG Shock Absorber Assy” or AMM Task 32-21-13-000-001-A01 “Removal of the NLG Shock Absorber Assy with nose jacking only”. (2) Contact AIRBUS immediately. (3) Put the removed parts in quarantine pending Airbus instructions. Procedure – Barkhausen Noise Inspection (BNI) b) Do a BNI of the NLG sliding tube chromed-surface in accordance with Fig. 2: refer to Safran PCS- 3700. In case of findings: (1) Replace the cracked NLG Sliding Tube before the next flight, refer to appropriate CMM; or replace the NLG shock absorber, refer to AMM Task 32-21-13-000-001-A “Removal of the NLG Shock Absorber Assy” or AMM Task 32-21-13-000-001-A01 “Removal of the NLG Shock Absorber Assy with nose jacking only”. (2) Contact AIRBUS immediately. (3) Put the removed parts in quarantine pending Airbus instructions. If No Crack are found during MPI inspection and Nil findings during BNI inspection: (1) Re-Install the NLG shock absorber, refer to AMM task 32-21-13-400-001-A “Installation of the NLG Shock Absorber Assy” or AMM task 32-21-13-400-001-A01 “Installation of the NLG Shock Absorber Assy with nose jacking only”. c) Inspection Reporting sheet (Appendix 3) shall be filled and returned to Airbus within 1 month counted from the inspection date even if nil finding. ### Page 9 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 9 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT Figure 2: NLG Sliding Tube Area for the MPI and BNI inspection 4.2.2.4 Do an Acid Etch and MPI inspection of the NLG sliding tube base material Preparation a) Remove the NLG Shock Absorber, refer to AMM Task 32-21-13-000-001-A “Removal of the NLG Shock Absorber Assy” or AMM task 32-21-13-000-001-A01 “Removal of the NLG Shock Absorber Assy with nose jacking only”. NOTE: The following inspection must be done in a shop environment as it requires the prior disassembly of the sliding tube from the NLG shock absorber assy to perform the removal of the chrome plating. Procedure a) Remove chromium plate from the NLG sliding tube in accordance with Fig. 3: refer to Safran PCS-2110. NOTE: Chromium must be removed prior to completion of the following inspections. b) Do a magnetic particle inspection (MPI) of the NLG sliding tube in accordance with Fig. 3: refer to Safran PCS-3100 inclusion class 4. - Record any findings and take photos. - For acceptance criteria: refer to Safran PCS-3100 inclusion class 4. c) Do an Acid Etch inspection of the NLG sliding tube in accordance with Fig. 3: refer to Safran PCS- 3600. - Record any findings and take photos. - For acceptance criteria: refer to Safran PCS-3600. ### Page 10 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 10 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT In case of findings during the MPI or the Acid Etch inspection: (1) Contact Safran Landing Systems and Airbus for further instructions before continuing with a repair. If the inspections show nil findings: (1) Restore the NLG sliding tube and re-assemble the shock absorber, refer to relevant CMM. (2) Re-Install the NLG shock absorber, refer to AMM task 32-21-13-400-001-A “Installation of the NLG Shock Absorber Assy” or AMM task 32-21-13-400-001-A01 “Installation of the NLG Shock Absorber Assy with nose jacking only”. d) Inspection Reporting sheet (Appendix 3) shall be filled and returned to Airbus within 1 month counted from the inspection date even if nil finding. Figure 3: NLG sliding tube area to be inspected after chrome removal (MPI + Acid etch) 4.2.2.5 Do a DVI inspection of the MLG sliding tube Preparation a) Lift the aircraft on jacks, refer to AMM Task 07-11-00-581-001-A. Procedure a) Clean the visible chromed surface of the MLG sliding tube, refer to AMM Task 32-11-00-100- 002. b) Do a DVI of the MLG sliding tube visible chromed-surface with the aircraft lifted on jacks in accordance with Fig. 4. If cracks are found: (1) Replace the cracked MLG Sliding Tube before the next flight, refer to AMM Task 32-11-13- 000-004-A “Removal of the Sliding Tube Sub-Assy of the MLG Shock Absorber “ ; or replace the MLG shock absorber, refer to AMM Task 32-11-13-000-001-A “Removal of the MLG Shock Absorber”. (2) Contact AIRBUS immediately. (3) Put the removed parts in quarantine pending Airbus instructions. ### Page 11 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 11 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT If no cracks are found: (1) Lower the aircraft and put the aircraft back to its initial configuration, refer to AMM Task 07- 11-00-586-002-A. c) Inspection Reporting sheet (Appendix 4) shall be filled and returned to Airbus within 1 month counted from the inspection date even if nil finding. Figure 4: MLG sliding tube Area for the DVI inspection (Aircraft on Jacks) 4.2.2.6 Do a MPI and BNI inspection of the MLG sliding tube Preparation a) Remove the MLG Shock Absorber, refer to AMM Task 32-11-13-000-001-A “Removal of the MLG Shock Absorber”. Procedure – Magnetic Particle Inspection (MPI) a) Do an MPI of the MLG sliding tube chromed-surface in accordance with Fig. 5: refer to Non Destructive Test Manual (NTM) 51-70-00. If cracks are found: (1) Replace the cracked MLG Sliding Tube before the next flight, refer to AMM Task 32-11-13- 000-004-A “Removal of the Sliding Tube Sub-Assy of the MLG Shock Absorber “ ; or replace the MLG shock absorber, refer to AMM Task 32-11-13-000-001-A “Removal of the MLG Shock Absorber”. (2) Contact AIRBUS immediately. (3) Put the removed parts in quarantine pending Airbus instructions. Procedure – Barkhausen Noise Inspection (BNI) b) Do a BNI of the MLG sliding tube chromed-surface in accordance with Fig. 5: refer to Safran PCS- 3700. ### Page 12 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 12 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT In case of findings: (1) Replace the MLG Sliding Tube before the next flight, refer to AMM Task 32-11-13-000-004- A “Removal of the Sliding Tube Sub-Assy of the MLG Shock Absorber “ ; or replace the MLG shock absorber, refer to AMM Task 32-11-13-000-001-A “Removal of the MLG Shock Absorber”. (2) Contact AIRBUS immediately. (3) Put the removed parts in quarantine pending Airbus instructions. If No cracks are found during MPI inspection and Nil findings during BNI inspection: (1) Re-Install the MLG shock absorber, refer to AMM Task 32-11-13-400-001-A “Installation of the MLG Shock Absorber”. c) Inspection Reporting Sheet (Appendix 4) shall be filled and returned to Airbus within 1 month counted from the inspection date even if nil finding. Figure 5: MLG sliding tube Area for the MPI and BNI inspection 4.2.2.7 Do an Acid Etch and MPI inspection of the MLG sliding tube base material Preparation a) Remove the Sliding Tube Sub-Assembly of the MLG Shock Absorber, refer to AMM Task 32-11- 13-000-004-A “Removal of the Sliding Tube Sub-Assembly of the MLG Shock Absorber”. NOTE: The following inspection must be done in a shop environment as it requires the prior disassembly of the sliding tube from the MLG shock absorber assy to perform the removal of the chrome plating. Procedure a) Remove chromium plate from the MLG sliding tube in accordance with Fig. 6: refer to Safran PCS-2110. NOTE: Chromium must be removed prior to completion of the following inspections. ### Page 13 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 13 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT b) Do a Magnetic Particle Inspection (MPI) of the MLG sliding tube in accordance with Fig. 6: refer to Safran PCS-3100 inclusion class 4. - Record any findings and take photos. - For acceptance criteria: refer to Safran PCS-3100 inclusion class 4. c) Do an Acid Etch inspection of the MLG sliding tube in accordance with Fig. 6: refer to Safran PCS-3600. - Record any findings and take photos. - For acceptance criteria: refer to Safran PCS-3600. In case of findings during the MPI or the Acid Etch inspection: (1) Contact Safran Landing Systems and Airbus for further instructions before continuing with a repair. If the MPI or the Acid Etch inspections show Nil findings: (1) Restore the MLG sliding tube and re-assemble the shock absorber, refer to relevant CMM. (2) Re-Install the Sliding Tube Sub-Assembly of the MLG Shock Absorber, refer to AMM Task 32-11-13-400-004-A “Installation of the Sliding Tube Sub-Assembly of the MLG Shock Absorber”. d) Inspection Reporting Sheet (Appendix 4) shall be filled and returned to Airbus within 1 month counted from the inspection date even if nil finding. Figure 6: MLG sliding tube area to be inspected after chrome removal (MPI + Acid etch) 4.2.3 FINDINGS - (RC) In case of cracks found during the DVI inspection, the affected sliding tube has to be replaced before next flight. Report the findings immediately to Airbus and put the removed parts in quarantine pending Airbus instructions. ### Page 14 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 14 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT In case of cracks found during the MPI inspection or in case of any finding during the BNI inspection on the chrome surface, the affected sliding tube has to be replaced before next flight. Report the findings immediately to Airbus and put the removed parts in quarantine pending Airbus instructions. In case of cracks found during the MPI inspection or in case of any finding during Acid Etch inspection on the base material, the affected sliding tube must be considered as unserviceable. Report the findings immediately to Airbus and put the removed parts in quarantine pending Airbus instructions. Do not attempt any repair before consulting Airbus or Safran. 4.3 SPARES AND TOOLING For material and tooling necessary for the Removal / Installation of the NLG shock absorber, refer to the AMM Task 32-21-13-000-001-A and AMM Task 32-21-13-400-001-A or AMM Task 32-21-13-000-001- A01 and AMM Task 32-21-13-400-001-A01. For material and tooling necessary for the Removal / Installation of the MLG shock absorber, refer to the AMM Task 32-11-13-000-001-A and AMM Task 32-11-13-400-001-A. For material and tooling necessary for the Removal / Installation of the MLG sliding tube sub-assembly of the shock absorber, refer to the AMM Task 32-11-13-000-004-A and AMM Task 32-11-13-400-004-A. 5. FURTHER INFORMATION 5.1 FOLLOW-UP PLAN It is anticipated that an Airworthiness Directive will be issued by EASA to mandate the content of this AOT. 5.2 IMPACTED DOCUMENTATION N/A 6. AOT APPROVAL The technical content of this document is approved under the authority of the DOA ref.EASA.21J.031. 7. REPORTING Questions about this AOT are to be addressed to Airbus Customer Services through TechRequest on Airbus World, selecting Engineering Domain Section and ATA 32-21. As per latest reporting policy (Ref to OIT 999.0018/16), inspection results (with or without findings) are to be addressed to Airbus Customer Services through the generic e-mail address: inspection.results@airbus.com. For traceability purpose the following information is to be included in the mail title: {AOT ref} {ICAO code} Inspection Result Best Regards, ### Page 15 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 15 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT Christian FREMONT VICE PRESIDENT ENGINEERING SUPPORT CUSTOMER SERVICES Jean Pierre GOMEZ VICE PRESIDENT A320 FAMILY PROGRAMME CUSTOMER SERVICES ### Page 16 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 16 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT APPENDIX 1 List of suspected NLG sliding tubes SN Aircraft type NLG sliding tube Part Number (PN) NLG sliding tube Serial Number (SN) L2338 L2109A318/A319/A320/A321 D66679 CMM 32-27-48, 32-27-21, 32- 27-33 B577-1874 ### Page 17 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 17 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT APPENDIX 2 List of suspected MLG sliding tubes SN Aircraft type MLG sliding tube Part Number (PN) MLG sliding tube Serial Number (SN) B2031-3288 B2029-8097 07B4224X8739 07B4107X14977 B3821-14792 B2615-3747 B2653-3794 B3169-14257 B3187-14276 B3715-14684 B3681-14640 B3486-14535 B3499-14519 B3544-14527 B3410-14459 A318/A319/A320 201371304 (CMM 32-11-33; 32-12-25) 07B4436X15115 ### Page 18 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 18 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT APPENDIX 3 INSPECTION REPORTING SHEET (NLG) PN SN CSN CSO NLG Sliding tube Fitted on A/C MSN DATE OF DVI INSPECTION ON CHROMED SURFACE (AIRCRAFT ON JACKS) YES NO QUESTION ARE CRACKS FOUND ON THE CHROMED SURFACE OF THE SLIDING TUBE? DATE OF MPI INSPECTION ON CHROMED SURFACE YES NO QUESTION ARE CRACKS FOUND ON THE CHROMED SURFACE OF THE SLIDING TUBE? DATE OF BNI INSPECTION ON CHROMED SURFACE YES NO QUESTION ANY FINDING ON THE BASED METAL OF THE SLIDING TUBE? DATE OF MPI INSPECTION ON BASE METAL YES NO QUESTION ARE CRACKS FOUND ON THE CHROMED SURFACE OF THE SLIDING TUBE? DATE OF ETCH INSPECTION ON BASE METAL YES NO QUESTION ANY FINDING ON THE BASED METAL OF THE SLIDING TUBE? PN: Part Number SN: Serial Number CSN: Cycle Since New CSO: Cycle Since Overhaul ### Page 19 ALERT OPERATORS TRANSMISSION - AOT AOT ref: A32N024-21 Rev 00 Page 19 of 19 Date: 07-OCT-2021 © AIRBUS S.A.S. 2021. ALL RIGHTS RESERVED. CONFIDENTIAL AND PROPRIETARY DOCUMENT APPENDIX 4 INSPECTION REPORTING SHEET (MLG) PN SN CSN CSO MLG Sliding tube Fitted on A/C MSN DATE OF DVI INSPECTION ON CHROMED SURFACE (AIRCRAFT ON JACKS) YES NO QUESTION ARE CRACKS FOUND ON THE CHROMED SURFACE OF THE SLIDING TUBE? DATE OF MPI INSPECTION ON CHROMED SURFACE YES NO QUESTION ARE CRACKS FOUND ON THE CHROMED SURFACE OF THE SLIDING TUBE? DATE OF BNI INSPECTION ON CHROMED SURFACE YES NO QUESTION ANY FINDING ON THE BASED METAL OF THE SLIDING TUBE? DATE OF MPI INSPECTION ON BASE METAL YES NO QUESTION ARE CRACKS FOUND ON THE CHROMED SURFACE OF THE SLIDING TUBE? DATE OF ETCH INSPECTION ON BASE METAL YES NO QUESTION ANY FINDING ON THE BASED METAL OF THE SLIDING TUBE? PN: Part Number SN: Serial Number CSN: Cycle Since New CSO: Cycle Since Overhaul --- 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.