# CASA Service Bulletin AOT-CN235-53-0004 ## Copies (2) Copies the FAA filed in AD dockets on regulations.gov, newest revision first. A newer revision may exist. - Revision 3 ("AOT-CN235-53-0004 Rev 3"), 12 pages: PDF https://openairdocs.org/files/sha256/2b/16/2b16dbb7eedd829ff8815025b1475080b1c40a5696b726232c70c383e0ca2e20; text https://openairdocs.org/service-documents/casa/aot-cn235-53-0004/file/2b16dbb7eedd.md. Rights: © CASA. Filed by the FAA in regulations.gov docket FAA-2023-1999, the docket of AD 2023-25-11. Not covered by OpenAirDocs’ CC0 dedication. - Revision 2 ("AOT-CN235-53-0004 R2"), 12 pages: PDF https://openairdocs.org/files/sha256/07/a5/07a59b5c04b139c68575453662c91b5dd0b1c775acc269d24e6a689f0d47861c; text https://openairdocs.org/service-documents/casa/aot-cn235-53-0004/file/07a59b5c04b1.md. Rights: © CASA. Filed by the FAA in regulations.gov docket FAA-2020-1020, the docket of AD 2021-02-18. Not covered by OpenAirDocs’ CC0 dedication. ## Details - Manufacturer: [CASA](https://openairdocs.org/service-documents/casa.md) - Type: Service bulletin (Service Bulletin) - Number: AOT-CN235-53-0004 - Latest revision known: AOT-CN235-53-0004, Revision 2 (OpenAirDocs) - Page: https://openairdocs.org/service-documents/casa/aot-cn235-53-0004 ## Text (12 pages) Revision 3, the newest copy. Rights: © CASA. Filed by the FAA in regulations.gov docket FAA-2023-1999, the docket of AD 2023-25-11. Not covered by OpenAirDocs’ CC0 dedication. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 Ref No.: AOT - CN235 - 53 - 0004 Rev No.: 3 Rev Date: 16/09/2022 SERVICES DIRECTORATE Pº John Lennon s/n 28906 Getafe, Madrid, SPAIN mta.technicalservice@es.airbus.com Alert Operators Transmission Page : 1 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 Aircraft Type: CN - 235 Applicability: ALL Referenced Documents: Ref.1 SB235 - 53 - 0070M - 00 Ref.2 SB235 - 53 - 0070C - 00 NOTE: This AOT is considered by Airbus DS as a Mandatory Action © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document and its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved This Information is of origin Airbus DS Spain and does not contain any export controlled Information 1. REASON FOR REVISION Rev No.1 :  New threshold and grace period added  New inspection method added  Interval inspections added  New areas to be inspected added Rev No.2 : Due to new findings has been detected in nearest areas of the main inspection area, new areas to be inspected has been included. Rev No. 3 : Issue 03 of the present AOT is edited to include the terminating action of the repetitive inspections requested in the AOT and results of investigation. ### Page 2 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 2 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved 2. REASON 2.1 FACTS One CN - 235 operator has found two s trin gers (P0 - LH/ P0 - RH) cracked at Frame 43 area. LH stringer crack had a length of 47mm (profile completely cracked) and RH stringer crack had a length of 45mm (profile partially cracked, crack starts at RH profile edge and extends to the center line). The a ng les and the corresponding fuselage skin panel have been inspected and n o cracks, scratches, corrosion, deformation or other kind of damages have been found in those elements . - A second case was reported by Airbus DS MRO during maintenance tasks in other CN - 235. 2.2 CONSEQUENCES The damage fou nd, if undetected, could potentially grow to dimensions that could affect structural integrity. 2.3 AIM The aim of this comm unication is to inform operators about the instructions to inspect the affected elements . 2.4 INVESTIGATION The root cause of the damages in the stringers is the operation with port door open that induces a big load and bending moment in the stringer and a big stress concentration just at the rivet hole of the last attachment position between the gusset and the stringer. 3. SHORT TERM ACTION 3.1 P LANNING AND MANPOWER 3.1.1 ACCOMPLISHMENT TIMES CALE The inspection described in paragraph 3.2 has to be performed on the affected aircraft according to next information: For Serie 300: - Threshold : 1400 FC/FH or next A - Check (whichever occurs later) . - Grace period : For aircraft with more than 1400 FC/FH the following grace periods are established: o Aircraft with less than 7500 FC/ FH: During next A - check. ### Page 3 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 3 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved o Aircraft between 7500 FC/FH and 15000 FC/FH : 50 FC/FH. o Aircraft with more than 15000 FC/FH : B efore the next flight. - Inspection interval : There are two depending on inspection performed: o 230 FC/FH with a D etailed Visual Inspection (DET) or o 340 FC/FH with a High Frequency Eddy Currents I nspection (HFEC) For Series 10, 100 and 200: - Threshold : 2400 FC/FH. - Grace period : For aircraft with more than 2400 FC/FH inspect during next A - check - Inspection interval : There are two depending on inspection performed: o 69 0 FC/FH with a D etailed Visual Inspection (DET) or o 95 0 FC/FH with a High Frequency Eddy Currents I nspection (HFEC) Note f or aircraft inspected according to Revision 0 and 1 of this AOT : - If NO findings were found, perform inspection according to inspection interva l defined in Revision 2 from last inspection. If this inspection interval has been reached, perform inspection no later than 50FC/FH. Note for aircraft inspected according to Revision 0 and 1 of this AOT and repaired through a RDAS: - P erform the inspection 3 to 5 according to Threshold defined in Revision 2 3.1.2 MANPOWER The esti mated time to get access an d perform the inspection is 2 ma n hour s per aircraft . ### Page 4 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 4 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved 3.2 DESCRIPTION 3.2.1 ACCESS Get access to the internal area ensuring that the aircraft is in safe conditions for maintenance tasks . 3.2.2 INSPECTION REQUIREME NTS Inspection to be performed consists on : - Inspection 1 : Detailed Visual Inspection (DET) or High Frequency Eddy Currents Inspection (HFEC ) of the stringer P0a and P0a’ at the riveted line of the attachment to the gusset and along the stringer head, in particular at the area of the last attachment of the gusset to the stringer in the midpoint between FR43 and FR44. (See Figure 02) - Inspection 2: Detailed V isual I nspection (DET) of the fuselage skin, along the stringers foot - print and surrounding structure and the attachment o f the gusset to the Frame 43 looking for fatigue cracks. (See Figures 03 and 04) - Inspection 3: Detailed Visual Inspection (DET) of the actuator bracket on Frame 43, along the radius of the vertical nerves, inner lugs holes and attachment holes of the bracket to the Frame 43 looking for fatigue cracks. (See Figures 05 and 06) - Inspection 4: Detailed Visual Inspection (DET) of Frame 43, along both sides of the frame, between stringer P1d and P1d’ ( two stringers for each side from the central stringer P0 a) looking for fatigue cracks or broken rivets in the web and joint clips to skin and stringer. - Inspection 5: Detailed Visual Inspection (DET) of the gussets, along the flange which joint the Frame 43 looking for fatigue cracks or broken rivets. Note: In case of doubts, please do not hesitate to contact Airbus DS . 3.2.3 FINDINGS - In case of findings, please contact Airbus DS with a detailed damage report according to SIL - CN235 - 51 - 0001 to get further instructions. - In case of no findings, please contact Airbus DS to confirm no finding results. Note: In Figure 07, 08, 09 there are some examples of findings. 3.3 SPARES AND TOOLING No special tooling is needed. ### Page 5 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 5 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved 4. FURTHER INFORMATION 4.1 FOLLOW - UP PLAN Airbus Defence & Space has dispatched Service Bulletins SB235 - 53 - 0070M - 00 and SB235 - 53 - 0070C - 00 (Ref. [1] and Ref. [2]). 4.2 IMPACTED DOCUMENTATI ON N/A 4.3 TERMINATING ACTION Airbus Defence & Space has dispatched Service Bulletins SB235 - 53 - 0070M - 00 and SB235 - 53 - 0070C - 00 (Ref. [1] and Ref. [2]), these SBs and future revisions are considered the terminating action for the inspections defined in the present AOT. Additionally Airbus Defence & Space has dispatched for some Aircrafts which found findings during AOT accomplishment a perm anent repair via RDAS. These RDAS are also considered the terminating action for the inspections defined in the present AOT. 5. REPORTING Questions about this AOT and inspection results with or without findings are to be sent to : Airbus DS Technical Assistance Center (AMTAC): Telephone: (+34) 91 600 79 99 E - mail: mta.technicalservice@es.airbus.com This AOT is or it is expected to be subject to an Airworthiness Directive or Airworthiness Directive Recommendation Letter. Released by Raul - Angel Garcia - Alvarez Electronically Validated HO Engineering Support Transport “The technical content of this document is approved under the authority of the DOA ref. EASA. 21.J.032.” “ The technical content of this document is approved under the authority of AODM ref ES.PERAM21J/7001/20 . ” ### Page 6 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 6 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved ANNEX 1 – FIGURES. Figure 01. General Location. ### Page 7 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 7 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved ANNEX 1 – FIGURES (CONT.) Figure 02. Lateral view of LH gusset. (Symmetrical for RH) ### Page 8 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 8 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved ANNEX 1 – FIGURES (CONT.) Figure 03. Stringer footprints (View looking up) ### Page 9 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 9 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved Figure 04. A ttachment to the Frame 43 . (View looking up) Figure 05. Actuator Bracket to the Frame 43 (View looking up) Figure 06. Actuator Bracket to the Frame 43 (Right and Left Lateral View) FWD ### Page 10 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 10 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved ANNEX 1 – FIGURES (CONT.) Figure 07. Examples of findings. ### Page 11 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 11 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved Figure 08. Example of findings on actuator bracket ### Page 12 Reference No.: AOT - CN235 - 53 - 0004 Revision No.: 3 Date: 16/09/2022 Alert Operators Transmission Page : 12 / 12 ATA Chapter: 53 - 30 - 00 Subject: Inspections for cracks in rear fuselage upper stringers at FR43 © AIRBUS DEFENCE AND SPACE. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS DEFENCE AND SPACE. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document sha ll not be reproduced or disclosed to a third party without the express written consent of AIRBUS DEFENCE AND SPACE. This document a nd its content shall not be used for any purpose other than that for which it is supplied. © AIRBUS DEFENCE AND SPACE 2022 All right reserved Figure 09. Examples of findings on clips. --- 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.