# Aviation Partners Boeing Service Bulletin AP757-57-012 Copy: Revision 1 ("APB SB AP757-57-012 R1"), 126 pages: PDF https://openairdocs.org/files/sha256/88/d6/88d6571fae09501eebc5cb83977873af0ed0b1a9011e739e8f0b8da0ad9074e4; text https://openairdocs.org/service-documents/aviation-partners-boeing/ap757-57-012/file/88d6571fae09.md. Rights: © Aviation Partners Boeing. Filed by the FAA in regulations.gov docket FAA-2025-0744; AD 2026-01-05 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. ## Details - Manufacturer: [Aviation Partners Boeing](https://openairdocs.org/service-documents/aviation-partners-boeing.md) - Type: Service bulletin (Service Bulletin) - Number: AP757-57-012 - Latest revision known: AP757-57-012, Revision 1, dated October 17, 2024 (OpenAirDocs) - Page: https://openairdocs.org/service-documents/aviation-partners-boeing/ap757-57-012 ## ADs that cite it (1) (OpenAirDocs) Newest first, with the revision each names, as OpenAirDocs read it from the AD's text. - [AD 2026-01-05](https://openairdocs.org/ad/2026-01-05.md), effective Feb 20, 2026: Revision 1 Also cited in [1 proposed AD](https://openairdocs.org/service-documents/aviation-partners-boeing/ap757-57-012/proposed.md). ## Text (126 pages) Rights: © Aviation Partners Boeing. Filed by the FAA in regulations.gov docket FAA-2025-0744; AD 2026-01-05 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 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page i Aviation Partners Boeing Proprietary ALERT NUMBER: AP757-57-012 Revision Transmittal Sheet Original Issue: May 16, 2024 Revision 1: October 17, 2024 ATA SYSTEM: 5720 SUBJECT: WINGS – Lower Stringer L-6 and L-8 Vertical Web Flange – Inspection and Repair This revision includes all pages of the service bulletin. COMPLIANCE INFORMATION RELATED TO THIS REVISION The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory. Revision 1: No airplane has been changed by Revision 0 of this service bulletin. Revision 0 of this service bulletin is not FAA approved. REASON FOR REVISION Revision 0 not released. Revision 1 is sent to clarify compliance conditions, actions and work instructions action descriptions to be consistent with the area of inspection. These sections were changed: - Table of Contents o Updated page numbers. - Summary - Action o Revised to add Group 1, 2 description, and Group 3 description. - Description o Added Group 1, 2 description, and 0.80 inch maximum diameter allowed for the freeze plug repair. o Added Group 3 description. - Compliance Group 1: o Table 2. Added note (b). Table 3. Added note (c). Group 2: o Table 5. Added note (b). Table 6. Added note (c). Group 3: o Table 7. Replaced GVI inspection/Maintenance records check table with High Frequency Eddy Current (HFEC) inspection for all Group 3 airplanes. Condition 1 no crack found, Action 1 repeat HFEC inspection 3,000 flight cycle. Condition 2 any crack found, Action, Contact Aviation Partners Boeing before further flight. Revised table notes. o Table 8 and Table 9 deleted. o Renumbered Tables and Conditions. Group 1: o Table 8 was Table 10. Table 9 was Table 11. Table 10 was Table 12. Revised Actions to reflect new Table numbers. Added note (b). Added note (c). ### Page 2 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page ii Aviation Partners Boeing Proprietary Group 2: o Table 11 was Table 13. Table 12 was Table 14. Table 13 was Table 15. Revised Actions to reflect new Table numbers. Added note (b). Added note (c). Group 3: o Table 14 was Table 16. Replaced GVI inspection/Maintenance records check table with High Frequency Eddy Current (HFEC) inspection for all Group 3 airplanes. Condition 1 no crack found, Action 1 repeat HFEC inspection 3,000 flight cycle. Condition 2 any crack found, Action, Contact Aviation Partners Boeing before further flight. Revised table notes. o Table 17 and Table 18 deleted. o Renumbered Tables and Conditions. - Manpower o Group 3 Left Wing. Removed Figure 2 Task and updated Total Hours and Elapsed Hours. o Group 3 Right Wing. Removed Figure 7 Task and updated Total Hours and Elapsed Hours - Accomplishment Instructions, Work Instructions Group 1-2: o Table 2. Added note (b). o Table 3. Condition 2.1 and Condition 3, Removed “Do Part 2: Close Access”. Added note (b) to Condition 2.1. o Table 5. Added note (b). o Table 6. Condition 2.1, 2.2 and Condition 3, Removed “Do Part 2: Close Access”. Added note to Condition 2.1. Group 3: o Table 7 and Table 8 deleted. Renumbered Tables and Conditions. o Table 7 was Table 9. Revised applicability to “All airplanes”. Revised Action 1 and Action 2. Removed Procedure “Part 2: Close Access” for Condition 2. Added note (b) o Table 10 and Table 11 deleted. o Table 8 was Table 12. Revised applicability to “All airplanes”. Revised Action 1 and Action 2. Removed Procedure “Part 2: Close Access” for Condition 2. Added note (b). - Appendix C: o Revised Compliance Table 7 logic diagram by removing existing freeze plug repair for Group 3. o Deleted Compliance Table 8 logic diagram. o Deleted Compliance Table 9 logic diagram. - Appendix D: o Compliance Table 8 was Table 10. o Compliance Table 9 was Table 11. o Compliance Table 10 was Table 12. - Appendix E: o Compliance Table 11 was Table 13. o Compliance Table 12 was Table 14. o Compliance Table 13 was Table 15. - Appendix F: o Compliance Table 14 was Table 16. Revised logic diagram by removing existing freeze plug repair for Group 3. o Deleted Compliance Table 17 logic diagram. o Deleted Compliance Table 18 logic diagram. ### Page 3 AVIATION PARTNERS BOEING SERVICE BULLETIN 555 Andover Park W., Suite 200 Tukwila, WA 98188 (206) 830-7699 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 1 of 124 Aviation Partners Boeing Proprietary ALERT NUMBER: AP757-57-012 Original Issue: May 16, 2024 Revision 1: October 17, 2024 ATA SYSTEM: 5720 SUBJECT: WINGS – Lower Stringer L-6 and L-8 Vertical Web Flange – Inspection and Repair PROPRIETARY NOTICE The data contained hereon and herein is proprietary to Aviation Partners Boeing. Neither this data nor the data contained herein shall be reproduced, used or disclosed to others without the written authorization of Aviation Partners Boeing. EXPORT CONTROLLED TECHNOLOGY This document contains information about a technology controlled by the Export Administration Regulations (EAR) (15 CFR 730 -774). It has been classified under Export Control Classification Number (ECCN) 9E991 and may not be exported to certain countries without a license. Providing this information to a foreign national – inside or outside the United States – can constitute a prohibited export. Each person handling this document has a legal responsibility to comply with all applicable EAR requirements and should consult with an Export Control Officer before providing it to any foreign national. ### Page 4 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 2 of 124 Aviation Partners Boeing Proprietary APB DOCUMENT FEEDBACK FORM To provide feedback on this document to APB for corrections or improvements, please complete the form below and email to the attention of APB Product Support Engineering at: Email: leng@aviationpartners.com Airline Name: ______________________________________________ Contact Name: ______________________________________________ Phone Number: ______________________________________________ Email Address: ______________________________________________ Airplane Model-Type: ______________________________________________ Document Number: ______________________________________________ Document Revision: ______________________________________________ Document Title: ______________________________________________ Chapter-Section- Subject: ______________________________________________ Page: ______________________________________________ Page Date: ______________________________________________ Description of Change: (Include additional sheets as required) Attachments: ______________________________________________ ### Page 5 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 3 of 124 Aviation Partners Boeing Proprietary Table of Contents APB DOCUMENT FEEDBACK FORM .....................................................................................................................2 Summary….. .............................................................................................................................................................5 1. PLANNING INFORMATION .................................................................................................................... 10 A. Effectivity ................................................................................................................................................. 10 1. Airplanes .................................................................................................................................................. 10 2. Spares Affected ....................................................................................................................................... 10 B. Concurrent Requirements........................................................................................................................ 10 C. Reason..................................................................................................................................................... 11 D. Description ............................................................................................................................................... 11 E. Compliance .............................................................................................................................................. 13 F. Approval ................................................................................................................................................... 31 G. Manpower ................................................................................................................................................ 31 H. Weight and Balance Changes ................................................................................................................. 33 I. Electrical Load Data ................................................................................................................................. 33 J. References .............................................................................................................................................. 33 1. Existing Data: ........................................................................................................................................... 33 2. Data Supplied with this Service Bulletin: ................................................................................................. 33 3. Installation Drawings Used in the Preparation of this Service Bulletin: ................................................... 33 K. Publications Affected ............................................................................................................................... 33 1. Publications ............................................................................................................................................. 33 2. Damage Tolerance Based Structural Inspections: .................................................................................. 33 L. Interchangeability and Intermixability of Parts ......................................................................................... 33 M. Software Accomplishment Summary ....................................................................................................... 33 2. MATERIAL INFORMATION..................................................................................................................... 34 A. Material – Price and Availability ............................................................................................................... 34 B. Industry Support Information ................................................................................................................... 34 C. Parts Necessary for Each Airplane .......................................................................................................... 34 1. Kits/Parts ................................................................................................................................................. 34 2. Parts and Materials Supplied by the Operator: ....................................................................................... 34 3. Parts Modified and Re-identified. ............................................................................................................ 34 4. Parts Removed and Not Replaced .......................................................................................................... 34 D. Parts Necessary to Change Spares ........................................................................................................ 34 E. Special Tooling – Price Availability .......................................................................................................... 34 F. Special Tooling Necessary to do this Service Bulletin ............................................................................ 34 3. ACCOMPLISHMENT INSTRUCTIONS ................................................................................................... 35 A. GENERAL INFORMATION ..................................................................................................................... 35 B. WORK INSTRUCTIONS .......................................................................................................................... 36 FIGURE 1: LEFT AND RIGHT WING ACCESS .................................................................................................. 48 ### Page 6 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 4 of 124 Aviation Partners Boeing Proprietary FIGURE 2: LEFT WING – GENERAL VISUAL INSPECTION (GVI) OR MAINTENANCE RECORDS CHECK – LOWER STRINGER L-6 AND STRINGER L-8 .................................................................................. 49 FIGURE 3: LEFT WING – STRINGER L-6 AND STRINGER L-8, WS 397.5 – WS 403 – HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION........................................................................................... 52 FIGURE 4: LEFT WING – STRINGER L-6 AND STRINGER L-8, FASTENER REMOVAL AND OPEN HOLE HFEC INSPECTION ........................................................................................................................... 56 FIGURE 5: LEFT WING – STRINGER L-6 AND STRINGER L-8, CRACK MEASUREMENT AND CRACK REMOVAL .......................................................................................................................................... 59 FIGURE 6: LEFT WING – STRINGER L-6 AND STRINGER L-8, FREEZE PLUG REPAIR, RESTORATION, AND FASTENER INSTALLATION ..................................................................................................... 61 FIGURE 7: RIGHT WING – GENERAL VISUAL INSPECTION (GVI) OR MAINTENANCE RECORDS CHECK – LOWER STRINGER L-6 AND STRINGER L-8 .................................................................................. 69 FIGURE 8: RIGHT WING – STRINGER L-6 AND STRINGER L-8, WS 397.5 – WS 403 – HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION........................................................................................... 72 FIGURE 9: RIGHT WING – STRINGER L-6 AND STRINGER L-8, FASTENER REMOVAL AND OPEN HOLE HFEC INSPECTION ........................................................................................................................... 76 FIGURE 10: RIGHT WING – STRINGER L-6 AND STRINGER L-8, CRACK MEASUREMENT AND CRACK REMOVAL .......................................................................................................................................... 79 FIGURE 11: RIGHT WING – STRINGER L-6 AND STRINGER L-8, FREEZE PLUG REPAIR, RESTORATION, AND FASTENER INSTALLATION ..................................................................................................... 81 APPENDIX A: LOGIC DIAGRAM, COMPLIANCE TABLE 1: GENERAL VISUAL INSPECTION (GVI) - LOWER STRINGER L-6 AND STRINGER L-8, LEFT WING .......................................................................... 89 APPENDIX B: LOGIC DIAGRAM, COMPLIANCE TABLE 4: GENERAL VISUAL INSPECTION (GVI) - LOWER STRINGER L-6 AND STRINGER L-8, LEFT WING .......................................................................... 97 APPENDIX C: LOGIC DIAGRAM, COMPLIANCE TABLE 7: HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION OF LOWER STRINGER L-6 AND STRINGER L-8, LEFT WING ............................. 105 APPENDIX D: LOGIC DIAGRAM, COMPLIANCE TABLE 8: GENERAL VISUAL INSPECTION (GVI) - LOWER STRINGER L-6 AND STRINGER L-8, RIGHT WING ...................................................................... 107 APPENDIX E: LOGIC DIAGRAM, COMPLIANCE TABLE 11: HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION OF LOWER STRINGER L-6 AND STRINGER L-8, RIGHT WING........................... 115 APPENDIX F: LOGIC DIAGRAM, COMPLIANCE TABLE 14: HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION OF LOWER STRINGER L-6 AND STRINGER L-8, RIGHT WING........................... 123 ### Page 7 AVIATION PARTNERS BOEING SERVICE BULLETIN 555 Andover Park W., Suite 200 Tukwila, WA 98188 (206) 830-7699 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 5 of 124 Aviation Partners Boeing Proprietary Summary….. ALERT NUMBER: AP757-57-012 Summary Original Issue: May 16, 2024 Revision 1: October 17, 2024 ATA SYSTEM: 5720 SUBJECT: WINGS – Lower Stringer L-6 and L-8 Vertical Web Flange – Inspection and Repair THIS DOCUMENT IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS DOCUMENT TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE NEW OWNER. CONCURRENT REQUIREMENTS None. BACKGROUND Accomplishment of this service bulletin will make sure that any crack in the left and right wing lower stringer L -6 and lower stringer L -8 common to the reinforcement strap inboard fasteners will be found and repaired before reaching a critical length. If the work given in this service bulletin is not done, any undetected crack in the lower stringer L-6 or lower stringer L-8 could result in the inability of a principal structural element to sustain limit loads which could adversely affect the structural integrity of the airplane. An operator accomplishing a 4C maintenance check on a 757 -200 airplane equipped with APB Scimitar Blended Winglets (SBW) with 22,185 flight cycles and 106,470 flight hours, reported finding a 0.40 -inch crack on the right wing lower stringer L -8 vertical web flange at approximately WS 401. The crack was located at a fastener common to the stringer L -8 and a reinforcement strap. The finding was a result of the High Frequency Eddy Current (HFEC) inspection in accordance with APB DTR Check Form 57-20-12A, per Boeing B757 NDT Manual, Part 6, 51-00-19 from Direction 1. This service bulletin provides instructions to do a surface High Frequency Eddy Current (HFEC) inspection of the left and right wing lower stringer L -6 vertical web flange and lower stringer L-8 vertical web flange, for any crack common to the reinforcement strap inboard fasteners. ### Page 8 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 6 of 124 Aviation Partners Boeing Proprietary This table is provided to operators for planning purposes only. Refer to the applicable sections for more information. Planning Data Affected Reference Spares Affected No Paragraph 1.A.2., Spares Affected AD Related No Paragraph 1.E, Compliance Weight and Balance Change No Paragraph 1.H., Weight and Balance Changes Electrical Load Changed No Paragraph 1.I., Electrical Load Data Publications Affected No Paragraph 1.K., Publications Affected Airplane Flight Operations Affected (Flight Crew Operations Manual and/or FAA Approved Airplane Flight Manual) No Paragraph 1.K., Publications Affected Kits/Parts Required No Paragraph 2.C.1., Kits/Parts Operator Supplied Parts/Material No Paragraph 2.C.2., Parts and Materials Supplied by the Operator Special Tooling Required No Paragraph 2.F., Special Tooling Necessary to do this Service Bulletin ACTION Group 1, 2: Do a surface HFEC inspection of the wing lower stringer L -6 and lower stringer L-8 vertical web flange, common to the reinforcement strap attach fasteners between WS 397.50 and WS 403.00 for any crack. If any crack is found, do the repair as given in this service bulletin . If no crack is found, repeat internal surface HFEC inspection of the wing lower stringer L -6 vertical web flange and stringer L-8 vertical web flange, common to the reinforcement strap attach fasteners located between WS 397.50 and WS 403.00 for any crack. Group 3: Do a surface HFEC inspection of the wing lower stringer L -6 and lower stringer L-8 vertical web flange , common to the reinforcement strap attach fasteners between WS 397.50 and WS 403.00 for any crack. If any crack is found, contact Aviation Partners Boeing for repair instru ctions and do the repair . If no crack is found, repeat internal surface HFEC inspection of the wing lower stringer L -6 vertical web flange and stringer L-8 vertical web flange, common to the reinforcement strap attach fasteners located between WS 397.50 and WS 403.00 for any crack EFFECTIVITY 757-200, -300 Airplane(s). Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplane(s). COMPLIANCE The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in the service bulletin mandatory. Refer to Paragraph 1.E., Compliance. INDUSTRY SUPPORT INFORMATION Aviation Partners Boeing warranty remedies are not available for the inspections , configuration changes, and/or repair procedures given in this service bulletin. ### Page 9 AVIATION PARTNERS BOEING SERVICE BULLETIN 555 Andover Park W., Suite 200 Tukwila, WA 98188 (206) 830-7699 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 7 of 124 Aviation Partners Boeing Proprietary MANPOWER Refer to Paragraph 1.G., Manpower. MATERIAL INFORMATION Operator Supplied Parts/Materials. ### Page 10 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 FWD RIGHT WING LOWER STRINGER L-8 RIGHT WING LOWER STRINGER L-6 LEFT WING LOWER STRINGER L-8 LEFT WING LOWER STRINGER L-6 WS WS 397.50 425.50 RIB 12 RIB 13 STRINGER L-6 B STRINGER L-8 F c IBI FWD LEFT WING SHOWN, RIGHT WING OPPOSITE Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 8 of 124 Aviation Partners Boeing Proprietary ### Page 11 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 WSTA WSTA 425.50 397.50 RIB 13 RIB 12 „STRINGER L-6 REINFORCEMENT STRAP (FAR SIDE) + + + + + + +++0000 IBD DO A HIGH FREQUENCY EDDY CURRENT INSPECTION OF THE LEFT AND RIGHT WING, LOWER STRINGER L-6, AROUND ATTACH FASTENERS COMMON TO REINFORCEMENT STRAP INBOARD RUNOUT, FOR ANY CRACK. ANY CRACK FOUND, DO THE REPAIR ACCORDING TO INSTRUCTIONS OF THIS SERVICE BULLETIN. NO CRACK FOUND, DO REPEAT INSPECTIONS. LOWER STRINGER L6 LEFT WING SHOWN RIGHT WING OPPOSITE (VIEW LOOKING FWD) B- B SURFACE HFEC INSPECTION AREA WSTA WSTA 397.50 RIB 12 425.50 ‚RIB 13 „STRINGER L-8 REINFORCEMENT STRAP (FAR SIDE) ++++ + + + ++++ DO A HIGH FREQUENCY EDDY CURRENT INSPECTION OF THE LEFT AND RIGHT WING, LOWER STRINGER L-8, AROUND ATTACH FASTENERS COMMON TO REINFORCEMENT STRAP INBOARD RUNOUT, FOR ANY INBD CRACK. ANY CRACK FOUND, DO THE REPAIR ACCORDING TO INSTRUCTIONS OF THIS SERVICE BULLETIN. NO CRACK FOUND, DO REPEAT INSPECTIONS. LOWER STRINGER L8 LEFT WING SHOWN RIGHT WING OPPOSITE (VIEW LOOKING AFT) C - C SURFACE HFEC INSPECTION AREA Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 9 of 124 Aviation Partners Boeing Proprietary ### Page 12 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 10 of 124 Aviation Partners Boeing Proprietary ALERT NUMBER: AP757-57-012 Original Issue: May 16, 2024 Revision 1: October 17, 2024 ATA SYSTEM: 5720 SUBJECT: WINGS – Lower Stringer L-6 and L-8 Vertical Web Flange – Inspection and Repair THIS DOCUMENT IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A, EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS DOCUMENT TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE NEW OWNER. 1. PLANNING INFORMATION A. Effectivity 1. Airplanes RC: Start This service bulletin is applicable to 757-200 and 757-300 aircraft modified in accordance with STC ST01518SE, with winglets or wing tips installed. GROUP CONFIGURATION DESCRIPTION 1 - 757-200 Airplanes modified in accordance with STC ST01518SE Blended Winglet configuration, with winglets or wing tips installed. 2 - 757-200 Airplanes modified in accordance with STC ST01518SE Scimitar Blended Winglet configuration, Or 757-200 Airplanes modified in accordance with STC ST01518SE Scimitar Blended Winglet configuration with service bulletin AP757- 57-010 incorporated. 3 - 757-300 Airplanes modified in accordance with STC ST01518SE Blended Winglet configuration, with winglets or wing tips installed. RC: End RC: Start 2. Spares Affected None. RC: End RC: Start B. Concurrent Requirements None. RC: End ### Page 13 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 11 of 124 Aviation Partners Boeing Proprietary C. Reason Accomplishment of this service bulletin will make sure that any crack in the left and right wing lower stringer L-6 and lower stringer L-8 common to the reinforcement strap inboard fasteners will be found and repaired before reaching a critical length. If the work given in this service bulletin is not done, any undetected crack in the lower stringer L -6 or lower stringer L-8 could result in the inability of a principal structural element to sustain limit loads which could adversely affect the structural integrity of the airplane. An operator accomplishing a 4C maintenance check on a 757 -200 airplane equipped with APB Scimitar Blended Winglets (SBW) with 22,185 flight cycles and 106,470 flight hours, reported finding a 0.40 -inch crack on the right wing lower stringer L -8 vertical web flange at approximately WS 401. The crack was located at a fastener common to the stringer L -8 and a reinforcement strap. The finding was a result of the High Frequency Eddy Current (HFEC) inspection in accordance with APB DTR Check Form 57-20- 12A, per Boeing B757 NDT Manual, Part 6, 51-00-19 from Direction 1. This service bulletin provides instructions to do a surface HFEC inspection of the left and right wing lower stringer L-6 vertical web flange and lower stringer L-8 vertical web flange, for any crack common to the reinforcement strap inboard (4) fasteners. D. Description Group 1, 2: Do a surface High Frequency Eddy Current (HFEC) inspection of the left and right wing lower stringer L-6 and L-8, vertical web flange around (4) inboard fasteners common to the reinforcement strap between WS 397.50 and WS 403.00 for any crack. If a single crack is found, follow the conditions and actions and prepare for a freeze plug repair. If the freeze plug repair exceeds 0.80 inch maximum diameter allowed, or multiple cracks are found in a single inspection area, contact Aviation Partners Boeing for repair instructions and do the repair. If no crack is found, do a repeat surface HFEC inspection of the left and right wing lower stringer L -6 and L -8 vertical web flange around (4) inboard fasteners common to the reinforcement strap between WS 397.50 and WS 403.00 for any crack. Group 3: Do a surface High Frequency Eddy Current (HFEC) inspection of the left and right wing lower stringer L-6 and L-8, vertical web flange around (4) inboard fasteners common to the reinforcement strap between WS 397.50 and WS 403.00 for any crack. If a single crack is found, contact Aviation Partners Boeing for repair instructions and do the repair. If no crack is found, do a repeat surface HFEC inspection of the left and right wing lower stringer L -6 and L-8 vertical web flange around (4) inboard fasteners common to the reinforcement strap between WS 397.50 and WS 403.00 for any crack. Group 1: Affected Maintenance Zones Model Zone 757-200 Airplanes modified in accordance with STC ST01518SE Blended Winglet configuration, with winglets or wing tips installed. 541, 641 Group 2: Affected Maintenance Zones Model Zone 757-200 Airplanes modified in accordance with STC ST01518SE Scimitar Blended Winglet configuration, Or 757-200 Airplanes modified in accordance with STC ST01518SE Scimitar Blended Winglet configuration with service bulletin AP757-57-010 incorporated. 541, 641 ### Page 14 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 12 of 124 Aviation Partners Boeing Proprietary Group 3: Affected Maintenance Zones Model Zone 757-300 Airplanes modified in accordance with STC ST01518SE Blended Winglet configuration, with winglets or wing tips installed. 541, 641 ### Page 15 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 13 of 124 Aviation Partners Boeing Proprietary RC: Start E. Compliance The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin . The Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory. Accomplish the required action(s), based on the applicable condition(s) in Table 1 through Table 18, in accordance with Accomplishment Instructions. When more than one OPTION is given for a CONDITION, do only one of the OPTION numbers. When more than one ACTION is given for a CONDITION or an OPTION, do all of the ACTION numbers for that CONDITION or OPTION. Group 1: Table 1: General Visual Inspection (GVI) or Maintenance Records Check – Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) All airplanes ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) Before 9,500 Flight Cycles after Blended Winglet installation. Within 3,000 Flight Cycles or 24 months after the original issue date of this Service Bulletin, whichever occurs later. - ACTION 2: Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - CONDITION 1: STRINGER L-6 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 2 for ACTIONS. CONDITION 2: STRINGER L-6 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 3 for ACTIONS. ### Page 16 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 14 of 124 Aviation Partners Boeing Proprietary Group 1: Table 1: General Visual Inspection (GVI) or Maintenance Records Check – Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) CONDITION 3: STRINGER L-8 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 2 for ACTIONS. CONDITION 4: STRINGER L-8 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 3 for ACTIONS. (a) An approved freeze plug repair is defined as a freeze plug repair accomplished in accordance with Service Bulletin AP757-57-012, or a deviation of Service Bulletin AP757-57-012 that is Aviation Partners Boeing DER approved with an FAA Form 8110-3. (b) A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair in accordance with Service Bulletin AP757-57-012 exists in that location. (c) More than one CONDITION can be applicable on each airplane. Group 1: Table 2: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with an existing Freeze Plug Repair, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH AN EXISTING FREEZE PLUG REPAIR ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: ANY CRACK FOUND. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (b) Before further flight. CONDITION 2: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 17 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 15 of 124 Aviation Partners Boeing Proprietary Group 1: Table 3: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH NO EXISTING FREEZE PLUG REPAIR. ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles CONDITION 2: ANY CRACK FOUND. (a) ACTION 1: Do an open hole HFEC inspection for any crack. Before further flight. - CONDITION 2.1: ANY ADDITIONAL CRACK FOUND AT ANY REMOVED FASTENER LOCATION AFTER OPEN HOLE HFEC INSPECTION. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (c) Before further flight - CONDITION 2.2: NO ADDITIONAL CRACK FOUND AFTER REMOVAL OF FASTENERS AND OPEN HOLE HFEC INSPECTION. (a) ACTION 1: Measure crack length. (b) Before further flight - CONDITION 3: CRACK LENGTH IS GREATER THAN 0.268 INCH.(a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight - CONDITION 4: CRACK LENGTH IS LESS THAN OR EQUAL TO 0.268 INCH.(a) ACTION 1: Crack removal and Open Hole HFEC Inspection. Before further flight - CONDITION 4.1: ANY REMAINING CRACK FOUND AFTER THE HOLE DIAMETER WAS INCREASED TO THE MAXIMUM 0.80 INCH. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight. - ### Page 18 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 16 of 124 Aviation Partners Boeing Proprietary Group 1: Table 3: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) CONDITION 4.2: AFTER REMOVAL OF CRACK, MAXIMUM HOLE DIAMETER LESS THAN OR EQUAL TO 0.80 INCH. (a) ACTION 1: Do a freeze plug repair. Before further flight. - ACTION 2: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Crack length shall be measured from the edge of fastener hole to end of crack. If fastener hole has more than one crack, measure the longest crack only. (c) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 19 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 17 of 124 Aviation Partners Boeing Proprietary Group 2: Table 4: General Visual Inspection (GVI) or Maintenance Records Check – Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) All airplanes ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) Before 8,000 Flight Cycles after Blended Winglet installation. Within 3,000 Flight Cycles or 24 months after the original issue date of this Service Bulletin, whichever occurs later. - ACTION 2: Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - CONDITION 1: STRINGER L-6 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 5 for ACTIONS. CONDITION 2: STRINGER L-6 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 6 for ACTIONS. CONDITION 3: STRINGER L-8 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 5 for ACTIONS. CONDITION 4: STRINGER L-8 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 6 for ACTIONS. ### Page 20 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 18 of 124 Aviation Partners Boeing Proprietary Group 2: Table 4: General Visual Inspection (GVI) or Maintenance Records Check – Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) (a) An approved freeze plug repair is defined as a freeze plug repair accomplished in accordance with Service Bulletin AP757-57-012, or a deviation of Service Bulletin AP757-57-012 that is Aviation Partners Boeing DER approved with an FAA Form 8110-3. (b) A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair in accordance with Service Bulletin AP757-57-012 exists in that location. (c) More than one CONDITION can be applicable on each airplane. Group 2: Table 5: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with an existing Freeze Plug Repair, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH AN EXISTING FREEZE PLUG REPAIR ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: ANY CRACK FOUND. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (b) Before further flight. CONDITION 2: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 21 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 19 of 124 Aviation Partners Boeing Proprietary Group 2: Table 6: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH NO EXISTING FREEZE PLUG REPAIR. ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles CONDITION 2: ANY CRACK FOUND. (a) ACTION 1: Do an open hole HFEC inspection for any crack. Before further flight. - CONDITION 2.1: ANY ADDITIONAL CRACK FOUND AT ANY REMOVED FASTENER LOCATION AFTER OPEN HOLE HFEC INSPECTION. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (c) Before further flight - CONDITION 2.2: NO ADDITIONAL CRACK FOUND AFTER OPEN HOLE HFEC INSPECTION. (a) ACTION 1: Measure crack length. (b) Before further flight - CONDITION 3: CRACK LENGTH IS GREATER THAN 0.268 INCH.(a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight - CONDITION 4: CRACK LENGTH IS LESS THAN OR EQUAL TO 0.268 INCH.(a) ACTION 1: Crack removal and Open Hole HFEC Inspection. Before further flight - CONDITION 4.1: ANY REMAINING CRACK FOUND AFTER THE HOLE DIAMETER WAS INCREASED TO THE MAXIMUM 0.80 INCH. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight. - ### Page 22 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 20 of 124 Aviation Partners Boeing Proprietary Group 2: Table 6: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) CONDITION 4.2: AFTER REMOVAL OF CRACK, MAXIMUM HOLE DIAMETER LESS THAN OR EQUAL TO 0.80 INCH. (a) ACTION 1: Do a freeze plug repair. Before further flight. - ACTION 2: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Crack length shall be measured from the edge of fastener hole to end of crack. If fastener hole has more than one crack, measure the longest crack only. (c) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 23 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 21 of 124 Aviation Partners Boeing Proprietary Group 3: Table 7: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) All airplanes ACTION 1: Do a surface HFEC Inspection of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for any crack. Before 9,000 Flight Cycles after Blended Winglet installation. Within 1,800 Flight Cycles or 22 months after the original issue date of this Service Bulletin, whichever occurs later. - ACTION 2: Do a surface HFEC Inspection of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for any crack. - CONDITION 1: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in the inspection area. 3,000 flight cycles CONDITION 2: ANY CRACK FOUND. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (b) Before further flight - (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 24 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 22 of 124 Aviation Partners Boeing Proprietary Group 1: Table 8: General Visual Inspection (GVI) or Maintenance Records Check - Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) All airplanes ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) Before 9,500 Flight Cycles after Blended Winglet installation. Within 3,000 Flight Cycles or 24 months after the original issue date of this Service Bulletin, whichever occurs later. - ACTION 2: Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - CONDITION 1: STRINGER L-6 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 9 for ACTIONS. CONDITION 2: STRINGER L-6 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 10 for ACTIONS. CONDITION 3: STRINGER L-8 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 9 for ACTIONS. CONDITION 4: STRINGER L-8 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 10 for ACTIONS. ### Page 25 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 23 of 124 Aviation Partners Boeing Proprietary Group 1: Table 8: General Visual Inspection (GVI) or Maintenance Records Check - Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) (a) An approved freeze plug repair is defined as a freeze plug repair accomplished in accordance with Service Bulletin AP757-57-012, or a deviation of Service Bulletin AP757-57-012 that is Aviation Partners Boeing DER approved with an FAA Form 8110-3. (b) A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair in accordance with Service Bulletin AP757-57-012 exists in that location. (c) More than one CONDITION can be applicable on each airplane. Group 1: Table 9: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with an existing Freeze Plug Repair, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH AN EXISTING FREEZE PLUG REPAIR ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: ANY CRACK FOUND. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (b) Before further flight. CONDITION 2: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 26 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 24 of 124 Aviation Partners Boeing Proprietary Group 1: Table 10: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH NO EXISTING FREEZE PLUG REPAIR. ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles CONDITION 2: ANY CRACK FOUND. (a) ACTION 1: Do an open hole HFEC inspection for any crack. (c) Before further flight. - CONDITION 2.1: ANY ADDITIONAL CRACK FOUND AT ANY REMOVED FASTENER LOCATION AFTER OPEN HOLE HFEC INSPECTION. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight - CONDITION 2.2: NO ADDITIONAL CRACK FOUND AFTER REMOVAL OF FASTENERS AND OPEN HOLE HFEC INSPECTION. (a) ACTION 1: Measure crack length. (b) Before further flight - CONDITION 3: CRACK LENGTH IS GREATER THAN 0.268 INCH.(a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight - CONDITION 4: CRACK LENGTH IS LESS THAN OR EQUAL TO 0.268 INCH.(a) ACTION 1: Crack removal and Open Hole HFEC Inspection. Before further flight - CONDITION 4.1: ANY REMAINING CRACK FOUND AFTER THE HOLE DIAMETER WAS INCREASED TO THE MAXIMUM 0.80 INCH. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight. - ### Page 27 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 25 of 124 Aviation Partners Boeing Proprietary Group 1: Table 10: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) CONDITION 4.2: AFTER REMOVAL OF CRACK, MAXIMUM HOLE DIAMETER LESS THAN OR EQUAL TO 0.80 INCH. (a) ACTION 1: Do a freeze plug repair. Before further flight. - ACTION 2: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Crack length shall be measured from the edge of fastener hole to end of crack. If fastener hole has more than one crack, measure the longest crack only. (c) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 28 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 26 of 124 Aviation Partners Boeing Proprietary Group 2: Table 11: General Visual Inspection (GVI) or Maintenance Records Check - Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) All airplanes ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) Before 8,000 Flight Cycles after Blended Winglet installation. Within 3,000 Flight Cycles or 24 months after the original issue date of this Service Bulletin, whichever occurs later. - ACTION 2: Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - CONDITION 1: STRINGER L-6 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 12 for ACTIONS. CONDITION 2: STRINGER L-6 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 13 for ACTIONS. CONDITION 3: STRINGER L-8 WITH AN EXISTING FREEZE PLUG REPAIR IN ACCORDANCE WITH SERVICE BULLETIN AP757-57-012. (c) ACTION 1: See Table 12 for ACTIONS. CONDITION 4: STRINGER L-8 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 13 for ACTIONS. ### Page 29 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 27 of 124 Aviation Partners Boeing Proprietary Group 2: Table 11: General Visual Inspection (GVI) or Maintenance Records Check - Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) (a) An approved freeze plug repair is defined as a freeze plug repair accomplished in accordance with Service Bulletin AP757-57-012, or a deviation of Service Bulletin AP757-57-012 that is Aviation Partners Boeing DER approved with an FAA Form 8110-3. (b) A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair in accordance with Service Bulletin AP757-57-012 exists in that location. (c) More than one CONDITION can be applicable on each airplane. Group 2: Table 12: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with an existing Freeze Plug Repair, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH AN EXISTING FREEZE PLUG REPAIR ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: ANY CRACK FOUND. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (b) Before further flight. CONDITION 2: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Pa rtners Boeing. ### Page 30 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 28 of 124 Aviation Partners Boeing Proprietary Group 2: Table 13: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) STRINGER WITH NO EXISTING FREEZE PLUG REPAIR. ACTION 1: Do a surface HFEC inspection for any crack. CONDITION 1: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles CONDITION 2: ANY CRACK FOUND. (a) ACTION 1: Do an open hole HFEC inspection for any crack. Before further flight. - CONDITION 2.1: ANY ADDITIONAL CRACK FOUND AT ANY REMOVED FASTENER LOCATION AFTER OPEN HOLE HFEC INSPECTION. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (c) Before further flight - CONDITION 2.2: NO ADDITIONAL CRACK FOUND AFTER REMOVAL OF FASTENERS AND OPEN HOLE HFEC INSPECTION. (a) ACTION 1: Measure crack length. (b) Before further flight - CONDITION 3: CRACK LENGTH IS GREATER THAN 0.268 INCH.(a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight - CONDITION 4: CRACK LENGTH IS LESS THAN OR EQUAL TO 0.268 INCH.(a) ACTION 1: Crack removal and Open Hole HFEC Inspection. Before further flight - CONDITION 4.1: ANY REMAINING CRACK FOUND AFTER THE HOLE DIAMETER WAS INCREASED TO THE MAXIMUM 0.80 INCH. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. Before further flight. - ### Page 31 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 29 of 124 Aviation Partners Boeing Proprietary Group 2: Table 13: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, with no existing Freeze Plug Repair, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) CONDITION 4.2: AFTER REMOVAL OF CRACK, MAXIMUM HOLE DIAMETER LESS THAN OR EQUAL TO 0.80 INCH. (a) ACTION 1: Do a freeze plug repair. Before further flight. - ACTION 2: Repeat surface HFEC inspection in inspection area. 6,000 flight cycles (a) More than one CONDITION can be applicable on each airplane. (b) Crack length shall be measured from the edge of fastener hole to end of crack. If fastener hole has more than one crack, measure the longest crack only. (c) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 32 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 30 of 124 Aviation Partners Boeing Proprietary Group 3: Table 14: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Compliance Time (Whichever Occurs Later) Repeat Interval (Not to Exceed) All airplanes ACTION 1: Do a surface HFEC Inspection of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for any crack. Before 9,000 Flight Cycles after Blended Winglet installation. Within 1,800 Flight Cycles or 22 months after the original issue date of this Service Bulletin, whichever occurs later. - ACTION 2: Do a surface HFEC Inspection of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for any crack. - CONDITION 1: NO CRACK FOUND. (a) ACTION 1: Repeat surface HFEC inspection in the inspection area. 3,000 flight cycles CONDITION 2: ANY CRACK FOUND. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. (b) Before further flight - (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. RC: End ### Page 33 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 31 of 124 Aviation Partners Boeing Proprietary F. Approval This service bulletin was examined by the Federal Aviation Administration (FAA) . The changes specified in this service bulletin comply with the applicable regulations and are FAA approved, as well as European Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on the airplane in its original Boeing delivery configuration and as modified by other approved Boeing changes. If an airplane has a non -Boeing modification or a repair that affects a component or system also affected by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval before incorporating this service bulletin. G. Manpower The table below shows an estimate of the task hours necessary to do this inspection for each airplane. This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator task hour data if necessary. The estimate does not include lost time or time to accomplish repairs . These are some examples of lost time: • Time to adjust to the workplace • Time to schedule the work • Time to inspect the work • Time to cure the materials • Time to make the parts • Time to find the tools Group 1 and Group 2: Left Wing Task Number of Persons Task Hours Elapsed Hours Open Access 1 0.5 0.5 FIGURE 2 1 0.2 0.2 FIGURE 3 1 0.4 0.4 FIGURE 4 1 0.5 0.5 FIGURE 5 1 0.4 0.4 FIGURE 6 1 1.0 1.0 Close Access 1 0.4 0.4 TOTAL FOR EACH AIRPLANE 3.4 3.4 ### Page 34 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 32 of 124 Aviation Partners Boeing Proprietary Group 1 and Group 2: Right Wing Task Number of Persons Task Hours Elapsed Hours Open Access 1 0.5 0.5 FIGURE 7 1 0.2 0.2 FIGURE 8 1 0.4 0.4 FIGURE 9 1 0.5 0.5 FIGURE 10 1 0.4 0.4 FIGURE 11 1 1.0 1.0 Close Access 1 0.4 0.4 TOTAL FOR EACH AIRPLANE 3.4 3.4 Group 3: Left Wing Task Number of Persons Task Hours Elapsed Hours Open Access 1 0.5 0.5 FIGURE 3 1 0.4 0.4 Close Access 1 0.4 0.4 TOTAL FOR EACH AIRPLANE 1.3 1.3 Group 3: Right Wing Task Number of Persons Task Hours Elapsed Hours Open Access 1 0.5 0.5 FIGURE 8 1 0.4 0.4 Close Access 1 0.4 0.4 TOTAL FOR EACH AIRPLANE 1.3 1.3 ### Page 35 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 33 of 124 Aviation Partners Boeing Proprietary H. Weight and Balance Changes None. I. Electrical Load Data Not changed. J. References 1. Existing Data: a. APB Service Bulletin AP757-57-010. b. Boeing 757-200 Aircraft Maintenance Manual (AMM) 12-11-01, 24-22-00, 28-11-00, 28-11-01, 28-26-00. c. Boeing 757-300 Aircraft Maintenance Manual (AMM) 12-11-01, 24-22-00, 28-11-00, 28-11-01, 28-26-00. d. Boeing 757-200 Structural Repair Manual (SRM), 51-10-02, 51-20-07, 51-40-02, 51-80-01. e. Boeing 757-300 Structural Repair Manual (SRM), 51-10-02, 51-20-07, 51-40-02, 51-80-01. f. Boeing 757 Non-Destructive Testing (NDT) Manual, Part 6, 51-00-01, 51-00-04, 51-00-11, 51-00- 14, 51-00-16, or 51-00-19. g. Boeing Standard Overhaul Practices Manual (SOPM) 20-44-04, 20-50-19. 2. Data Supplied with this Service Bulletin: None. 3. Installation Drawings Used in the Preparation of this Service Bulletin: 757-3430 Stringer Reinforcement L-6 Installation 757-3440 Stringer Reinforcement L-8 Installation These drawings were used to prepare this service bulletin. These drawings are not necessary to make the specified changes and are not supplied with this service bulletin. These drawings may not be applicable to all airplane configurations or operators. K. Publications Affected 1. Publications None. 2. Damage Tolerance Based Structural Inspections: Aviation Partners Boeing has evaluated the repairs and/or changes in this service bulletin for effects on Fatigue Critical Structure (FCS) and for changes to Damage Tolerance Inspections (DTI) required in the Maintenance Program. This service bulletin affects FCS and changes to DTI were necessary. After incorporation of the freeze plug repair described in FIGURE 6 or FIGURE 11 of this service bulletin, the surface HFEC inspection of the stringer vertical flange (direction 1) in DTR form 57 -20- 12A in AP57.2 -0604.2-DTR and AP57.3 -0604.2-DTR is no longer possible in the freeze plugged area. The applicable inspections specified in TABLES 2, 5, 8, 11, 14, and 17 achieve required DTR at the repaired locations. L. Interchangeability and Intermixability of Parts Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts . M. Software Accomplishment Summary Not affected. ### Page 36 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 34 of 124 Aviation Partners Boeing Proprietary 2. MATERIAL INFORMATION A. Material – Price and Availability None. B. Industry Support Information APB warranty remedies are not available for the inspection and/or repair procedures given in this service bulletin. C. Parts Necessary for Each Airplane 1. Kits/Parts None. 2. Parts and Materials Supplied by the Operator: None. 3. Parts Modified and Re-identified. None. 4. Parts Removed and Not Replaced None. D. Parts Necessary to Change Spares None. E. Special Tooling – Price Availability None. F. Special Tooling Necessary to do this Service Bulletin No special tools or equipment are necessary to do the change in this service bulletin. But maintenance and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine operator tool supply to make sure all necessary tools are available. ### Page 37 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 35 of 124 Aviation Partners Boeing Proprietary 3. ACCOMPLISHMENT INSTRUCTIONS A. GENERAL INFORMATION NOTE: RC: Start 1. If this Service Bulletin (SB) is mandated by an Airworthiness Directive (AD), then all applicable requirements specified in the SB must be done. Some locations are marked RC Start and RC End to identify the requirements. The areas between RC Start and RC End, including sub -steps and any figures identified between RC Start and RC End, must be done to comply with the AD. Therefore, an Alternative Method of Compliance (AMOC) is required for any deviations to steps between RC Start and RC End, including substeps and identified figures. Steps not between RC Start and RC End may be deviated from using accepted methods in accordance with the operator's maintenance or inspection program without obtaining approval of an AMOC; this is provided that the steps between RC Start and RC End, including sub -steps and identified figures, can still be done as specified, and the airplane can be put back in an airworthy condition. 2. The compliance times for the actions in WORK INSTRUCTIONS are in 1.E., Compliance. 3. Unless shown differently, these dimensions and tolerances are used: • Linear dimensions are in inches • Tolerance on linear dimensions, other than rivet and bolt edge margins, is plus or minus 0.03 inch • Tolerance on rivet and bolt edge margin is plus or minus 0.05 inch • Angular tolerance is plus or minus 2 degrees • Hole dimensions for standard solid rivets and fasteners are in Structural Repair Manual (SRM) Chapter 51 • Torque Values: – Values for structural fasteners are given in 757 Structural Repair Manual, Chapter 51. – Values for airframe maintenance tasks are included in Chapter 20 of 757 Aircraft Maintenance Manual (AMM). – Values for electrical maintenance tasks are included in Chapter 20 of Standard Wiring Practices Manual (SWPM). – Values for engine maintenance tasks are included in Chapter 70 of 757 Aircraft Maintenance Manual (AMM). – Non-standard torque values for maintenance tasks are included in the applicable installation step. 4. These work instructions refer to procedures included in other Boeing documents. When the words "refer to" are used and the operator has an accepted alternative procedure, the accepted alternative procedure can be used. When the words "in accordance with" are included in the instruction, the procedure in the Boeing document must be used. 5. Where the work instructions include installation of a kept part, a new or serviceable part with the same part number can be installed as an alternative to the kept part. 6. If it is necessary to remove more parts for access, you can remove those parts. If you can get access without removing identified parts, it is not necessary to remove all of the identified parts. Jacking and shoring limitations must be observed. ### Page 38 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 36 of 124 Aviation Partners Boeing Proprietary 7. Use the approved fastener, process and material substitutions in accordance with SRM Chapter 51. 8. When more than one OPTION is given for a CONDITION, do only one of the OPTION numbers. When more than one ACTION is given for a CONDITION or an OPTION, do all of the ACTION numbers for that CONDITION or OPTION. 9. If the length of any fastener specified in this service bulletin does not meet installation standards given in SRM Chapter 51, then a fastener of the same specification, or an approved substitute, with a length which meets the installation standards given in SRM Chapter 51 may be used. In addition, washers may be installed for fastener grip length in accordance with SRM Chapter 51. RC: End 10. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for definition of the acronyms. 11. Obey all of the warnings and cautions given in the specified manual sections. 12. Refer to APPENDIX A, APPENDIX B, APPENDIX C, APPENDIX D, APPENDIX E, and APPENDIX F of Service Bulletin AP757 -57-012 for logic diagrams. Logic diagrams are provided as an aid only. Information contained in 1.E., Compliance is the primary source for compliance times. Information in Work Instructions of this service bulletin is the primary source for tasks required for compliance. 13. Use of colors in Figures is based on guidance from the ATA e-Business Program (ATA) iSpec 2200. B. WORK INSTRUCTIONS RC: Start Actions Required for Compliance 1. Requirements ### Page 39 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 37 of 124 Aviation Partners Boeing Proprietary Group 1-2: Table 1: General Visual Inspection (GVI) or Maintenance Records Check - Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure All airplanes ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - PART 1: OPEN ACCESS. FIGURE 2 - ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - PART 1: OPEN ACCESS. FIGURE 2 - CONDITION 1: STRINGER L-6 WITH AN EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 2 for ACTIONS. - - CONDITION 2: STRINGER L-6 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 3 for ACTIONS. - - CONDITION 3: STRINGER L-8 WITH AN EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 2 for ACTIONS. - - CONDITION 4: STRINGER L-8 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 3 for ACTIONS. - - (a) An approved freeze plug repair is defined as a freeze plug repair accomplished in accordance with Service Bulletin AP757-57-012, or a deviation of Service Bulletin AP757-57-012 that is Aviation Partners Boeing DER approved with an FAA Form 8110-3. (b) A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair in accordance with Service Bulletin AP757 -57-012 exists in that location. (c) More than one CONDITION can be applicable on each airplane. ### Page 40 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 38 of 124 Aviation Partners Boeing Proprietary Group 1-2: Table 2: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L -6 and Stringer L-8, Left Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure Stringers with an approved stringer freeze plug repair resulting from Table 1, Condition 1 and/or Condition 3 finding. ACTION 1: Do a surface HFEC inspection of stringer L-6 for any crack. - PART 1: OPEN ACCESS FIGURE 3 - ACTION 2: Do a surface HFEC inspection of stringer L-8 for any crack. FIGURE 3 - CONDITION 1: ANY CRACK FOUND.(a) CONDITION 1, ACTION 1: Contact Aviation Partners Boeing for repair instructions and do the repair. (b) - - CONDITION 2: NO CRACK FOUND.(a) CONDITION 2, ACTION 1: Repeat surface HFEC inspection at stringer L-6 for any crack. - PART 2: CLOSE ACCESS - PART 1: OPEN ACCESS FIGURE 3 - CONDITION 2, ACTION 1: Repeat surface HFEC inspection at stringer L-8 for any crack. - PART 2: CLOSE ACCESS - PART 1: OPEN ACCESS FIGURE 3 - (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing ### Page 41 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 39 of 124 Aviation Partners Boeing Proprietary Group 1-2 Table 3: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L -6 and Stringer L-8, Left Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure Stringers with no existing freeze plug repair resulting from Table 1, Condition 2 and/or Condition 4 finding. ACTION 1: Do a surface HFEC inspection of stringer L-6 for any crack. - PART 1: OPEN ACCESS FIGURE 3 - ACTION 2: Do a surface HFEC inspection of stringer L-8 for any crack. FIGURE 3 - CONDITION 1: NO CRACK FOUND.(a) CONDITION 1, ACTION 1: Repeat surface HFEC inspection at stringer L-6 for any crack. - PART 2: CLOSE ACCESS FIGURE 3 PART 1: OPEN ACCESS CONDITION 1, ACTION 2: Repeat surface HFEC inspection at stringer L-8 for any crack. FIGURE 3 - - PART 2: CLOSE ACCESS CONDITION 2: ANY CRACK FOUND.(a) CONDITION 2, ACTION 1: Remove fasteners required to access damaged hole. Do an open hole HFEC inspection of all removed fastener holes for any crack. FIGURE 4 - CONDITION 2.1: ANY ADDITIONAL CRACK(S) FOUND AT ANY REMOVED FASTENER LOCATION AFTER OPEN HOLE HFEC INSPECTION.(a) CONDITION 2.1, ACTION 1: Contact Aviation Partners Boeing for repair instructions and do the repair. (b) - - CONDITION 2.2: NO ADDITIONAL CRACK(S) FOUND.(a) CONDITION 2.2, ACTION 1: Measure crack length. FIGURE 5 - CONDITION 3: CRACK LENGTH IS GREATER THAN 0.268 INCH.(a) Contact Aviation Partners Boeing for repair instructions and do the repair. - - ### Page 42 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 40 of 124 Aviation Partners Boeing Proprietary Group 1-2 Table 3: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L -6 and Stringer L-8, Left Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure CONDITION 4: CRACK LENGTH IS LESS THAN OR EQUAL TO 0.268 INCH.(a) CONDITION 4, ACTION 1: Crack removal and Open Hole HFEC Inspection. FIGURE 5 - CONDITION 4.1: ANY REMAINING CRACK FOUND AFTER THE HOLE DIAMETER WAS INCREASED TO THE MAXIMUM 0.80 INCH. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. - - CONDITION 4.2: AFTER REMOVAL OF CRACK, MAXIMUM HOLE DIAMETER LESS THAN OR EQUAL TO 0.80 INCH. (a) ACTION 1: Do a freeze plug repair. FIGURE 6 - ACTION 2: Repeat surface HFEC inspection in inspection area. - PART 2: CLOSE ACCESS (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 43 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 41 of 124 Aviation Partners Boeing Proprietary Group 1-2: Table 4: General Visual Inspection (GVI) or Maintenance Records Check - Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure All airplanes ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - PART 1: OPEN ACCESS. FIGURE 7 - ACTION 1: Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair. (a)(b) - - FIGURE 7 - CONDITION 1: STRINGER L-6 WITH AN EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 5 for ACTIONS. - - CONDITION 2: STRINGER L-6 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 6 for ACTIONS. - - CONDITION 3: STRINGER L-8 WITH AN EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 5 for ACTIONS. - - CONDITION 4: STRINGER L-8 WITH NO EXISTING FREEZE PLUG REPAIR. (c) ACTION 1: See Table 6 for ACTIONS. - - (a) An approved freeze plug repair is defined as a freeze plug repair accomplished in accordance with Service Bulletin AP757-57-012, or a deviation of Service Bulletin AP757-57-012 that is Aviation Partners Boeing DER approved with an FAA Form 8110-3. (b) A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair in accordance with Service Bulletin AP757 -57-012 exists in that location. (c) More than one CONDITION can be applicable on each airplane. ### Page 44 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 42 of 124 Aviation Partners Boeing Proprietary Group 1-2: Table 5: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L -6 and Stringer L-8, Right Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure Airplanes with an approved stringer freeze plug repair resulting from Table 4, Condition 1 and/or Condition 3 finding. ACTION 1: Do a surface HFEC inspection of stringer L-6 for any crack. - PART 1: OPEN ACCESS FIGURE 8 - ACTION 2: Do a surface HFEC inspection of stringer L-8 for any crack. FIGURE 8 - CONDITION 1: ANY CRACK FOUND.(a) CONDITION 1, ACTION 1: Contact Aviation Partners Boeing for repair instructions and do the repair. (b) -- - CONDITION 2: NO CRACK FOUND.(a) CONDITION 2, ACTION 1: Repeat surface HFEC inspection at stringer L-6 for any crack. - PART 2: CLOSE ACCESS - PART 1: OPEN ACCESS FIGURE 8 - CONDITION 2, ACTION 1: Repeat surface HFEC inspection at stringer L-8 for any crack. - PART 2: CLOSE ACCESS - PART 1: OPEN ACCESS FIGURE 8 - (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 45 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 43 of 124 Aviation Partners Boeing Proprietary Group 1-2 Table 6: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L -6 and Stringer L-8, Right Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure Stringers with no existing freeze plug repair resulting from Table 4, Condition 2 and/or Condition 4 finding. ACTION 1: Do a surface HFEC inspection of stringer L-6 for any crack. - PART 1: OPEN ACCESS FIGURE 8 - ACTION 2: Do a surface HFEC inspection of stringer L-8 for any crack. FIGURE 8 - CONDITION 1: NO CRACK FOUND.(a) CONDITION 1, ACTION 1: Repeat surface HFEC inspection at stringer L-6 for any crack. - PART 2: CLOSE ACCESS FIGURE 8 PART 1: OPEN ACCESS CONDITION 1, ACTION 2: Repeat surface HFEC inspection at stringer L-8 for any crack. FIGURE 8 - - PART 2: CLOSE ACCESS CONDITION 2: ANY CRACK FOUND.(a) CONDITION 2, ACTION 1: Remove fasteners required to access damaged hole. Remove crack. Do an open hole HFEC inspection of all removed fastener holes for any crack FIGURE 9 - CONDITION 2.1: ANY ADDITIONAL CRACK(S) FOUND AT ANY REMOVED FASTENER LOCATION AFTER OPEN HOLE HFEC INSPECTION.(a) CONDITION 2.1, ACTION 1: Contact Aviation Partners Boeing for repair instructions and do the repair. (b) - - CONDITION 2.2: NO ADDITIONAL CRACK(S) FOUND.(a) CONDITION 2.2, ACTION 1: Measure crack length. FIGURE 10 - CONDITION 3: CRACK LENGTH IS GREATER THAN 0.268 INCH.(a) Contact Aviation Partners Boeing for repair instructions and do the repair. - - ### Page 46 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October, 17, 2024 Page 44 of 124 Aviation Partners Boeing Proprietary Group 1-2 Table 6: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L -6 and Stringer L-8, Right Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757- 57-012 Original Issue or later approved revisions as an accepted procedure CONDITION 4: CRACK LENGTH IS LESS THAN OR EQUAL TO 0.268 INCH.(a) CONDITION 4, ACTION 1: Crack removal and Open Hole HFEC Inspection. FIGURE 10 - CONDITION 4.1: ANY REMAINING CRACK FOUND AFTER THE HOLE DIAMETER WAS INCREASED TO THE MAXIMUM 0.80 INCH. (a) Contact Aviation Partners Boeing for repair instructions and do the repair. - - CONDITION 4.2: AFTER REMOVAL OF CRACK, MAXIMUM HOLE DIAMETER LESS THAN OR EQUAL TO 0.80 INCH. (a) ACTION 1: Do a freeze plug repair. FIGURE 11 - ACTION 2: Repeat surface HFEC inspection in inspection area. - PART 2: CLOSE ACCESS (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 47 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 45 of 124 Aviation Partners Boeing Proprietary Group 3: Table 7: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, Left Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757-57- 012 Original Issue or later approved revisions as an accepted procedure All airplanes ACTION 1: Do a surface HFEC inspection of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for any crack. - PART 1: OPEN ACCESS. FIGURE 3 - ACTION 2: Do a surface HFEC inspection of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for any crack. FIGURE 3 - CONDITION 1: NO CRACK FOUND.(a) CONDITION 1, ACTION 1: Repeat surface HFEC inspection at stringer L-6 for any crack. - PART 2: CLOSE ACCESS FIGURE 3 PART 1: OPEN ACCESS CONDITION 1, ACTION 2: Repeat surface HFEC inspection at stringer L-8 for any crack. FIGURE 3 - - PART 2: CLOSE ACCESS CONDITION 2: ANY CRACK FOUND.(a) CONDITION 2, ACTION 1: Contact Aviation Partners Boeing for repair instructions and do the repair. (b) - - (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. ### Page 48 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 46 of 124 Aviation Partners Boeing Proprietary Group 3 Table 8: High Frequency Eddy Current (HFEC) inspection of Lower Stringer L-6 and Stringer L-8, Right Wing Condition Action Method of Compliance Refer to the listed procedure in SB AP757-57- 012 Original Issue or later approved revisions as an accepted procedure All airplanes ACTION 1: Do a surface HFEC inspection of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for any crack. - PART 1: OPEN ACCESS. FIGURE 8 - ACTION 2: Do a surface HFEC inspection of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for any crack. FIGURE 8 - CONDITION 1: NO CRACK FOUND.(a) CONDITION 1, ACTION 1: Repeat surface HFEC inspection at stringer L-6 for any crack. - PART 2: CLOSE ACCESS FIGURE 8 PART 1: OPEN ACCESS CONDITION 1, ACTION 2: Repeat surface HFEC inspection at stringer L-8 for any crack. FIGURE 8 - - PART 2: CLOSE ACCESS CONDITION 2: ANY CRACK FOUND.(a) CONDITION 2, ACTION 1: Contact Aviation Partners Boeing for repair instructions and do the repair. (b) - - (a) More than one CONDITION can be applicable on each airplane. (b) Any existing repair(s) in the inspection area shall be reported to Aviation Partners Boeing. RC: End ### Page 49 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 47 of 124 Aviation Partners Boeing Proprietary Procedures: 1. PART 1: GET ACCESS FOR INTERNAL INSPECTION. (FIGURE 1) a. De-fuel the wing main fuel tanks. Refer to 757 AMM 28-26-00 as an accepted procedure. b. Drain/Purge the main tanks and prepare for entry. Refer to 757 AMM, 28-11-00 as an accepted procedure. c. Ensure electrical power has been removed from the airplane. Refer to 757 AMM, 24 -22-00 as an accepted procedure. d. Gain access to the lower side of the wing main fuel tanks between WS 397.50 and WS 425.50 on both the left and right side of the aircraft. e. Remove and keep the following access panels. See FIGURE 1. Refer to 757 AMM, 28-11-01 as an accepted procedure for main tank access doors 541GB Access Door – Left Wing 641GB Access Door – Right Wing. 2. PART 2: CLOSE ACCESS. (FIGURE 1) a. Install kept main tank access panel. Refer to 757 AMM 28-11-01 as an accepted procedure. b. Re-fuel the main fuel tank. Refer to 757 AMM 12-11-01 as an accepted procedure. c. Do a fuel leak inspection of the main tank. Make sure main fuel tank access panel door and the area of inspection where sealant was disturbed does not leak. Refer to 757 AMM 28-11-00 as an accepted procedure. d. Put the airplane back to a serviceable condition. ### Page 50 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 WS 397.5 WS 397.5 WS 397.5 WS 397.5 (RIB 12) (RIB 12) WS 425.5 WS 425.5 (RIB 13) (RIB 13) LOWER ACCESS LOWER ACCESS DOOR 541GB DOOR 641GB STRINGER L-8- • STRINGER L-8 STRINGER L-6• - STRINGER L-6 NBD INBD LEFT WING LOWER PANEL RIGHT WING LOWER PANEL (PLAN VIEW) (PLAN VIEW) (INSPAR UPPER SKIN PANEL NOT SHOWN) (INSPAR UPPER SKIN PANEL NOT SHOWN) B FIGURE 1: LEFT AND RIGHT WING ACCESS Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 48 of 124 Aviation Partners Boeing Proprietary ### Page 51 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 RC: Start FWD LEFT WING LOWER STRINGER L-8 LEFT WING LOWER STRINGER L-6 WS WS 397.50 425.50 RIB 12 RIB 13 STRINGER L-6 B A CE STRINGER L-8 C FWD FIGURE 2: LEFT WING - GENERAL VISUAL INSPECTION (GVI) OR MAINTENANCE RECORDS CHECK - LOWER STRINGER L-6 AND STRINGER L-8 (SHEET 1 OF 3) Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 49 of 124 Aviation Partners Boeing Proprietary ### Page 52 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 WSTA WSTA 425.50 397.50 RIB 13 / STRINGER L-6 REINFORCEMENT RIB 12 STRAP (FAR SIDE) + + + INBD LEFT WING - LOWER STRINGER L6 (VIEW LOOKING FWD) B - B WSTA WSTA 397.50 425.50 RIB 12 RIB 13 STRINGER L-8 REINFORCEMENT STRAP (FAR SIDE) 00 LEFT WING - LOWER STRINGER L8 (VIEW LOOKING AFT) INBD C- C GENERAL VISUAL INSPECTION (GVI) INSPECTION AREA A Maintenance records check is acceptable in lieu of the General Visual Inspection if the records review can conclusively determine a repair exists in that location. FIGURE 2: LEFT WING - GENERAL VISUAL INSPECTION (GVI) OR MAINTENANCE RECORDS CHECK - LOWER STRINGER L-6 AND STRINGER L-8 (SHEET 2 OF 3) Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 50 of 124 Aviation Partners Boeing Proprietary ### Page 53 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 51 of 124 Aviation Partners Boeing Proprietary The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts for this figure. Step Task Name Identification Qty More Data 1 Inspect STRINGER L-6 112N4206-() 1 (a)(c) 2 Inspect STRINGER L-8 112N4208-() 1 (b)(c) (a) Do a General Visual Inspection (GVI) of the Lower Stringer L-6, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair (b) Do a General Visual Inspection (GVI) of the Lower Stringer L-8, vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair (c) A Maintenance Records check is acceptable in lieu of the GVI if the records review can conclusively determine a repair exists in the inspection area. RC: End FIGURE 2: LEFT WING – GENERAL VISUAL INSPECTION (GVI) OR MAINTENANCE RECORDS CHECK – LOWER STRINGER L-6 AND STRINGER L-8 (SHEET 3 OF 3) ### Page 54 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 52 of 124 Aviation Partners Boeing Proprietary RC: Start FIGURE 3: LEFT WING – STRINGER L-6 AND STRINGER L-8, WS 397.5 – WS 403 – HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION (SHEET 1 OF 4) ### Page 55 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 WSTA WSTA 425.50 397.50 • RIB 13 RIB 12 STRINGER L-6 REINFORCEMENT STRAP (FAR SIDE) NBD LEFT WING - LOWER STRINGER L6 (VIEW LOOKING FWD) B - B SURFACE HFEC INSPECTION AREA WSTA WSTA 397.50 RIB 12 425.50 RIB 13 STRINGER L-8 REINFORCEMENT • STRAP (FAR SIDE) INBD LEFT WING - LOWER STRINGER L8 (VIEW LOOKING AFT) C - C SURFACE HFEC INSPECTION AREA FIGURE 3: LEFT WING - STRINGER L-6 AND STRINGER L-8, WS 397.5 - WS 403 - HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION (SHEET 2 OF 4) Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 53 of 124 Aviation Partners Boeing Proprietary ### Page 56 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 WSTA 397.50 RIB 12 STRINGER L-6 REINFORCEMENT STRINGER L-6 STRAP (FAR SIDE) REINFORCEMENT STRAP 024 420 ' LOWER SKIN FWD F-F INBD WSTA 397.50 RIB 12 STRINGER L-8 REINFORCEMENT STRINGER L-8 STRAP (FAR SIDE) REINFORCEMENT STRAP 134 LOWER SKIN FWD G - G INBD FIGURE 3: LEFT WING - STRINGER L-6 AND STRINGER L-8, WS 397.5 - WS 403 - HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION (SHEET 3 OF 4) Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 54 of 124 Aviation Partners Boeing Proprietary ### Page 57 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 55 of 124 Aviation Partners Boeing Proprietary The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts for this figure. Step Task Name Identification Qty More Data 1 Remove Sealant - - (a) 2 Inspect STRINGER L-6 112N4206-() 1 (b) 3 Inspect STRINGER L-8 112N4208-() 1 (c) 4 Apply FUEL TANK SEALANT BMS5-45 - (d) Apply FAST CURE FUEL TANK SEALANT BMS5-168 - (d) (a) Prior to inspection, all sealant on the aft surface of the vertical web flange of Stringer 6 and on the forward side of the vertical web flange of Stringer 8 must be removed. Prior to inspection, any cap seal within 0.750 inches of any removed sealant must be removed. Refer to 757-200 AMM 28-11- 00, or 757-300 AMM 28-11-00 for an accepted procedure. (b) Do a surface High Frequency Eddy Current (HFEC) inspection of the lower Stringer L-6 vertical web flange around each of the four fasteners for any crack, from the aft side of the stringer, in accordance with 757 NDT Manual Part 6, 51-00-01 or 51-00-19. (c) Do a surface High Frequency Eddy Current (HFEC) inspection of the lower Stringer L -8 vertical web flange around each of the four fasteners for any crack, from the fwd side of the stringer, in accordance with 757 NDT Manual Part 6, 51-00-01 or 51-00-19. (d) Apply sealant in areas where the sealant was removed. Refer to 757-200 AMM 28-11-00, or 757-300 AMM 28-11-00 for an accepted procedure. RC: End FIGURE 3: LEFT WING – STRINGER L-6 AND STRINGER L-8, WS 397.5 – WS 403 – HIGH FREQUENCY EDDY CURRENT (HFEC) INSPECTION (SHEET 4 OF 4) ### Page 58 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 56 of 124 Aviation Partners Boeing Proprietary RC: Start FIGURE 4: LEFT WING – STRINGER L-6 AND STRINGER L-8, FASTENER REMOVAL AND OPEN HOLE HFEC INSPECTION (SHEET 1 OF 3) ### Page 59 (OCR) AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 WSTA WSTA 425.50 397.50 RIB 13 STRINGER L-6 ‚RIB 12 REINFORCEMENT STRAP (FAR SIDE) INBD 321 (VIEW LOOKING FWD) B - B WSTA WSTA 397.50 425.50 RIB 13 RIB 12 REINFORCEMENT STRINGER L-8 STRAP (FAR SIDE) (VIEW LOOKING AFT) INBD C - C FIGURE 4: LEFT WING - STRINGER L-6 AND STRINGER L-8, FASTENER REMOVAL AND OPEN HOLE HFEC INSPECTION (SHEET 2 OF 3) Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 57 of 124 Aviation Partners Boeing Proprietary ### Page 60 AVIATION PARTNERS BOEING SERVICE BULLETIN AP757-57-012 Original Issue: May 16, 2024 AP757-57-012 Revision 1: October 17, 2024 Page 58 of 124 Aviation Partners Boeing Proprietary The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for this figure. Step Task Name Identification Qty More Data 1 Remove FASTENER - - (a) 2 Remove FASTENERS - - (b) 3 Inspect STRINGER L-6 112N4206-() 1 (c) STRAP STRINGER L-6 757-3431-() 1 (d) 4 Inspect STRINGER L-8 112N4206-() 1 (e) STRAP STRINGER L-8 757-3441-() 1 (f) (a) Remove fastener at crack location. Refer to 757-200 SRM 51-40-02 as an accepted procedure. (b) Remove a minimum number of fasteners common to stringer and reinforcement strap required to get access to the damaged area. Refer to 757-200 SRM 51-40-02 as an accepted procedure. (c) Do an open-hole HFEC inspection of all removed fastener holes in stringer L-6 (aluminum) vertical web flange in accordance with 757 NDT Manual Part 6, 51-00-04, 51-00-11, or 51-00-16. (d) Do an open-hole HFEC inspection of all removed fastener holes in stringer L-6 reinforcement strap (stainless steel) in accordance with 757 NDT Manual Part 6, 51-00-14. (e) Do an open-hole HFEC inspection of all removed fastener holes in stringer L-8 (aluminum) vertical web flange in accordance with 757 NDT Manual Part 6, 51-00-04, 51-00-11, or 51-00-16. (f) Do an open-hole HFEC inspection of all removed fastener holes in stringer L-8 reinforcement strap (stainless steel) in accordance with 757 NDT Manual Part 6, 51-00-14. RC: End FIGURE 4: LEFT WING – STRINGER L-6 AND STRINGER L-8, FASTENER REMOVAL AND OPEN HOLE HFEC INSPECTION (SHEET 3 OF 3) The text continues at https://openairdocs.org/service-documents/aviation-partners-boeing/ap757-57-012/file/88d6571fae09.md?from=61 --- 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.