# Boeing Alert Service Bulletin 737-53A1293: U.S. DOT/FAA - Boeing Service Bulletin 737-53A1293 - Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2011-1254; AD 2012-12-04 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Boeing Alert Service Bulletin 737-53A1293](https://openairdocs.org/service-documents/boeing/737-53a1293.md) - Title as filed: U.S. DOT/FAA - Boeing Service Bulletin 737-53A1293 - Pages: 105 - PDF: https://openairdocs.org/files/sha256/19/7a/197a64a52da079483e4e5657e9b859d9f5d328242868b0b2e98a0d6a5f0c0f9c - Page: https://openairdocs.org/service-documents/boeing/737-53a1293/file/197a64a52da0 ## Text 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 Commercial Airplanes 737 Service Bulletin Number: 737-53A1293 Original Issue: August 13, 2008 Revision 2: August 10, 2011 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460 Inspection and Repair Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15 CFR 730-774). An export license may be required before it is used for development, production or use by foreign persons from specific countries. The controller of this data has the individual responsibility to abide by all export laws. 9E991ECCN: BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2008 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter. Boeing also claims copyright in this document as a compilation and/or collective work. This document includes proprietary information owned by The Boeing Company and/or one or more third parties. Treatment of the document and the information it contains is governed by contract with Boeing. For more information, contact The Boeing Company, P.O. Box 3707, Seattle, Washington 98124. Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner, BBJ, DC-8, DC-9, DC-10, KC-10, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8A, Poseidon and the Boeing livery are all trademarks owned by The Boeing Company; and no trademark license is granted in connection with this document unless provided in writing by Boeing. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 1 of 105 4.0 ### Page 2 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 2 of 105 BOEING SERVICE BULLETIN 737-53A1293 BLANK PAGE ### Page 3 Table of Contents Revision Transmittal Sheet ............................................ 5 Summary ...................................................... 7 1. PLANNING INFORMATION ........................................ 1 1 A. Effectivity ............................................... 1 1 1. Airplanes ............................................ 1 1 2. Spares Affected ........................................ 1 8 B. Concurrent Requirements ...................................... 1 8 C. Reason ................................................ 1 9 D. Description .............................................. 2 0 E. Compliance .............................................. 2 1 F. Approval ............................................... 4 3 G. Manpower .............................................. 4 3 H. Weight and Balance Changes .................................... 4 4 I. Electrical Load Data ......................................... 4 5 J. References .............................................. 4 5 1. Existing Data .......................................... 4 5 2. Data supplied with this Service Bulletin ............................ 4 6 3. Installation Drawings Used in the Preparation of this Service Bulletin ............ 4 6 K. Publications Affected ........................................ 4 6 L. Interchangeability and Intermixability of Parts ........................... 4 6 2. MATERIAL INFORMATION ........................................ 4 7 A. Material - Price and Availability ................................... 4 7 B. Industry Support Information .................................... 4 7 C. Parts Necessary For Each Airplane ................................. 4 7 1. Kits/Parts ............................................ 4 7 2. Parts and Materials Supplied by the Operator ........................ 4 7 3. Parts Modified and Reidentified ................................ 4 8 4. Parts Removed and Not Replaced .............................. 4 9 D. Parts Necessary to Change Spares ................................. 4 9 E. Special Tooling - Price and Availability ............................... 4 9 F. Special Tooling Necessary to do this Service Bulletin ....................... 4 9 3. ACCOMPLISHMENT INSTRUCTIONS .................................. 5 1 A. GENERAL INFORMATION ..................................... 5 1 B. WORK INSTRUCTIONS ....................................... 5 2 FIGURE 1: THIS FIGURE DELETED AT REVISION 1 [Group 1] ..................... 5 9 FIGURE 2: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400 - STA 460 [Group 1] .................................... 6 0 FIGURE 3: THIS FIGURE DELETED AT REVISION 1 [Group 2] ..................... 6 2 FIGURE 4: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400 - STA 460 [Group 2] .................................... 6 3 FIGURE 5: FUSELAGE SKIN - CRACK REMOVAL [Group 1] ...................... 6 5 FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION [Group 1] ............................................ 6 8 FIGURE 7: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1 AND S-2R, STA 400 - STA 460 [Group 1] .......................... 7 8 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 3 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 4 FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION [Group 1] ............................................ 8 0 FIGURE 9: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1 AND S-2R, STA 400 - STA 460 [Group 2] .......................... 9 1 FIGURE 10: FUSELAGE SKIN - CRACK REMOVAL [Group 2] ...................... 9 3 FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION [Group 2] ............ 9 6 FIGURE 12: POST REPAIR - CRITICAL FASTENER ROW INSPECTION [Group 2] .......... 1 0 2 APPENDIX A: CHEM-MILL STEP CRACK DAMAGE CUT-OUT AND REPORT ............. 1 0 4 APPENDIX B: CHEM-MILL STEP CRACK DAMAGE REPORT ...................... 1 0 5 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 4 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 5 Commercial Airplanes 737 Service Bulletin Revision Transmittal SheetNumber: 737-53A1293Original Issue: August 13, 2008 Revision 2: August 10, 2011 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460 Inspection and Repair This revision includes all pages of the service bulletin. COMPLIANCE INFORMATION RELATED TO THIS REVISION No more work is necessary on the airplanes changed in accordance with Revision 1 of this service bulletin. REASON FOR REVISION This revision is sent to revise the group 1 repair figures and add the group 2 repair instructions and post repair inspection. These sections were changed: 1. Summary Background information Revised. 2. Summary Action Group 1 and Group 2 information revised. 3. Summary Industry Support Information, warranty statement revised. 4. Summary Material Information revised. 5. Paragraph 1.A.1., Airplanes, paragraph added. 6. Paragraph 1.C., Reason, information revised and revision 2 reason added. 7. Paragraph 1.D., Description, Group 1 and Group 2 repair instructions revised. 8. Paragraph 1.E., Compliance, Table 1, Table 2 and Table 3 Condition column revised and note (c) added. Table 4 Action column revised. Table 5 Condition column revised and repair compliance details, note (a) was revised and note (c) added. Table 6 added. 9. Paragraph 1.F., Approval, AMOC statement revised. 10. Paragraph 1.G., Manpower, Group 2 table revised to add repair and post repair inspection information. 11. Paragraph 1.H., Weight and Balance Changes, Table replaced with equating statement. 12. Paragraph 1.J.1., Existing Data, book references revised. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 5 of 105 ### Page 6 13. Paragraph 2.A., Material - Price and Availability, paragraph added. 14. Paragraph 2.B., Industry Support Information, warranty statement revised. 15. Paragraph 2.C.2., Parts and Materials Supplied by the Operator, Group 2 table added. 16. Paragraph 3.A., General information, notes revised. 17. Paragraph 3.B., Work instructions, changed as follows: a. PART 1 - step 5.d. and 6.d. added. b. PART 2 - step 3 revised. c. PART 3 - step 4.d. and 5.d. added. d. PART 5 - caution deleted. Step 5 revised and step 6 added. e. PART 6 - step 4 revised and step 5 added. f. PART 7 and PART 8 added. 18. Figure 5 revised to show crack removal information only. View A and B deleted. Flag note table deleted. View C, now view A, revised to show crack information only. Step 1 and 2 deleted. New step 2 added. Foot notes (a), (b), (c), and (d) deleted. New foot notes (a) and (d) revised. 19. Figure 6, new illustration added, new step 1 and footnotes (g) thru (j) added. 20. Figure 8, new illustration added, new step 1 and footnotes (g) thru (j)added. 21. Figure 10, Figure 11 and Figure 12 added. 22. Appendix A, Group reference deleted. Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity, to show the location of important changes. Pages with no vertical lines have no important changes. REVISION HISTORY August 13, 2008Original Issue: July 07, 2010Revision 1: August 10, 2011Revision 2: BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 6 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 7 Commercial Airplanes 737 Service Bulletin SummaryNumber: 737-53A1293Original Issue: August 13, 2008 Revision 2: August 10, 2011 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460 Inspection and Repair CONCURRENT REQUIREMENTS None BACKGROUND Accomplishment of the inspections in this service bulletin will make sure that fuselage skin cracks at stringers S-1 and S-2R, between Body Stations STA 400 and STA 460 are found and repaired. An Air Traffic Control (ATC) antenna was installed at this location at delivery on the affected airplanes. All airplanes listed in this service bulletin require inspection even if the ATC antenna has been removed. This action is necessary to find and repair fatigue cracks of the skin panels at the chem-mill steps. Continued operation with undetected skin cracks could cause unscheduled down time for repairs or possibly a decompression of the airplane. Boeing has received several reports from multiple operators regarding fuselage skin cracks adjacent to the ATC antenna. A total of 60 cracks have been found on Group 1 airplanes (10 inch tear strap bays); cracks have been found at both S-1 and S-2R; the affected airplanes had accumulated between 40,080 and 67,032 total flight cycles. A total of 3 cracks have been found on Group 2 airplanes (20 inch tear strap bays); cracks have only been found at S-1, but similar cracking is possible at S-2R; the affected airplanes had accumulated between 43,565 and 44,700 total flight cycles. Analysis by Boeing indicates that the cracks are caused by fatigue due to high tension stresses and local bending at the edge of the chem-mill pockets of the bonded skin. The cracks initiate at the inner surface of the skin and typically originate at multiple sites along the chem-mill step. Multiple site originations can result in several adjacent partial-thickness cracks. These adjacent partial-thickness cracks can be subsequently linked together before propagating through the full-thickness of the skin. Accomplishment of the work given in this service bulletin will make sure that cracks in the fuselage skin at stringers S-1 and S-2R, between STA 400 and STA 460 are detected and repaired. Boeing Service Related Problem (SRP) 737-SRP-53-0334 is related to this service bulletin. Multi-Operator Message (MOM) MOM-MOM-09-0807-01B (R1) is related to this service bulletin. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 7 of 105 ### Page 8 ACTION 1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460. 3. Do external Non Destructive Inspections (NDI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460. The NDI's that can be used are Medium Frequency Eddy Current (MFEC), Magneto Optical Imaging (MOI), C-Scan or Ultrasonic Phased Array (UTPA). 4. If no crack is found, do repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 at intervals in accordance with Paragraph 1.E., Compliance. 5. Group 1: If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions, do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Paragraph 1.E., Compliance a. Crack(s) found before 35,000 total flight cycles. b. Crack(s) found in four or more tear strap bays. c. Crack(s) found longer than 5 inches. d. Crack(s) found are not contained within the skin cut-out. If all of the following is found as a result of the external DI and NDI, do the repair, the critical fastener row inspection and repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps not covered by a repair at intervals specified in Paragraph 1.E., Compliance. a. Crack(s) found at or after 35,000 total flight cycles. b. Crack(s) found in three or less strap bays. c. Crack(s) found 5 inches or shorter. d. Crack(s) found are contained within the skin cut-out. 6. Group 2: If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions, do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Paragraph 1.E., Compliance. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 8 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 9 a. Crack(s) found before 33,000 total flight cycles. b. Crack(s) found between STA 400 and STA 420. c. Crack(s) found between STA 440 and STA 460. d. Crack(s) found longer than 12.5 inches. e. Crack(s) found are not contained within the skin cut-out. If all of the following are found as a result of the external DI and NDI, do the repair, the critical fastener row inspection and repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps not covered by a repair, at intervals specified in Paragraph 1.E., Compliance. a. Crack(s) found at or after 33,000 total flight cycles. b. Crack(s) found between STA 420 and STA 440. c. Crack(s) found 12.5 inches or shorter. d. Crack(s) found are contained within the skin cut-out. EFFECTIVITY 737-300/-400/-500 Airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes. COMPLIANCE Federal Aviation Administration (FAA) Airworthiness Directive AD 2008-19-03 is related to this service bulletin. Refer to Paragraph 1.E., Compliance. INDUSTRY SUPPORT INFORMATION Boeing warranty remedies are not available for the inspection,and repair procedures given in this service bulletin. MANPOWER Refer to Paragraph 1.G., Manpower. MATERIAL INFORMATION Operator Supplied Parts/Materials. Refer to Paragraph 2.A., Material - Price and Availability BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 9 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 10 (OCR) BOEING SERVICE BULLETIN 737-53A1293 STA 460 ... . STA 400 1000 DO DETAILED INSPECTION AND DO MFEC INSPECTION OR MOI INSPECTION OR C-SCAN OR ULTRASONIC PHASE ARRAY INSPECTION FOR CRACKS IN THE FUSELAGE SKIN ALONG THE CHEM-MILL STEPS. TYPICAL CRACKS - S-1 [LAi TER -=→ S-2R STA STA STA STA STA STA STA 460 450 440 430 420 410 400 ATC ANTENNA INSPECTION AREA 10 INCH TEAR STRAP BAY CONFIGURATION SHOWN 1579184 20 INCH TEAR STRAP BAY CONFIGURATION SIMILAF Original Issue: August 13, 2008 Revision 2: August 10, 2011 BOEING PROPRIETARY - 737-53A1293 Copyright © Unpublished Work - See page 1 for details. 10 of 105 ### Page 11 Commercial Airplanes 737 Service Bulletin Number: 737-53A1293 Original Issue: August 13, 2008 Revision 2: August 10, 2011 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460 Inspection and Repair 1. PLANNING INFORMATION A. Effectivity 1. Airplanes Refer to Service Bulletin Index Document D6-19567 Part 3 for Airplane Variable Number, Line Number, and Serial Number data. This service bulletin is for the airplanes shown below. DESCRIPTIONCONFIGURATIONGROUP 737 - 300/-400/-500 Airplanes, line numbers 1001 thru 2552, which had an ATC antenna installed at STA 430 at delivery, with 10 inch tear strap bays. -1 Airplanes not inspected in accordance with the original issue of this service bulletin. 1 Airplanes inspected in accordance with the original issue of this service bulletin and the last inspection was a Detailed Inspection procedure. 2 Airplanes inspected in accordance with the original issue of this service bulletin and the last inspection was a MFEC or MOI or C-Scan Non-Destructive Inspection procedure. 3 Airplanes inspected in accordance with Boeing Multi-Operator-Message MOM-MOM-09-0807-01B (R1), dated 15-Dec-2009 and the last inspection was a Detailed Inspection procedure. 4 Airplanes inspected in accordance with Boeing Multi-Operator-Message MOM-MOM-09-0807-01B (R1), dated 15-Dec-2009 and the last inspection was a MFEC or MOI or C-Scan Non-Destructive Inspection procedure. 5 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 11 of 105 ### Page 12 DESCRIPTIONCONFIGURATIONGROUP 737 - 300/-400/-500 Airplanes, line numbers 2553 thru 3132, all of which had an ATC antenna installed at STA 430 at delivery, with 20 inch tear strap bays. -2 Airplane Models: 737-300, 737-400, 737-500 GroupVariable Number 1PJ301 - PJ302 1PJ551 2PJ552 - PJ561 2PJ601 - PJ615 2PJ811 2PJ816 - PJ817 1PM389 - PM399 1PM401 - PM417 1PM541 - PM542 2PM543 - PM550 1PM551 - PM564 1PP048 - PP054 1PP140 - PP160 1PP198 - PP199 1PP221 1PP508 - PP517 2PP518 - PP520 1PP805 - PP808 1PP874 - PP875 2PP876 - PP877 1PP910 - PP930 1PP951 - PP952 1PP966 - PP967 1PP984 - PP990 1PP993 1PQ013 - PQ016 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 12 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 13 GroupVariable Number 1PQ038 - PQ041 1PQ069 - PQ085 1PQ101 - PQ199 1PQ201 - PQ202 1PQ230 1PQ237 1PQ251 - PQ267 1PQ281 - PQ296 2PQ297 - PQ299 1PQ301 - PQ307 1PQ331 - PQ332 1PQ341 - PQ344 2PQ345 - PQ348 1PQ361 - PQ369 2PQ370 - PQ373 2PQ391 - PQ395 1PQ401 - PQ407 2PQ408 - PQ410 1PQ411 - PQ413 2PQ414 - PQ418 1PQ421 2PQ431 - PQ438 2PQ447 - PQ448 2PQ451 2PQ454 1PQ471 - PQ472 2PQ473 - PQ475 1PQ481 1PQ486 - PQ487 1PQ491 - PQ493 1PQ771 2PQ772 1PQ791 - PQ793 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 13 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 14 GroupVariable Number 1PQ801 - PQ805 1PQ931 - PQ932 2PQ933 - PQ935 2PQ951 2PQ971 - PQ997 2PR001 - PR017 2PR021 - PR034 2PR041 - PR045 2PR061 - PR072 2PR077 - PR082 2PR091 - PR092 2PR096 2PR101 2PR121 - PR122 2PR131 - PR132 2PR141 - PR143 2PR161 - PR172 2PR181 1PS601 - PS616 2PS617 - PS630 1PS631 1PS636 - PS638 1PS641 - PS644 1PS651 - PS657 1PS666 - PS669 1PS691 - PS692 1PS701 - PS703 2PS704 - PS706 1PS751 - PS762 2PS763 - PS799 2PS811 2PS836 - PS837 2PS841 - PS846 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 14 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 15 GroupVariable Number 2PS851 - PS852 2PS856 2PS861 - PS863 2PS866 - PS868 2PS871 - PS874 2PS896 - PS897 2PS901 - PS941 2PS956 - PS957 2PS961 - PS963 2PS971 - PS978 1PT001 - PT011 2PT012 - PT015 1PT021 - PT028 2PT029 - PT031 1PT041 - PT063 2PT064 1PT101 - PT105 1PT121 - PT125 2PT126 - PT138 1PT146 - PT148 1PT161 - PT170 1PT181 - PT187 2PT188 1PT211 - PT220 1PT295 1PT301 - PT306 2PT307 - PT309 1PT331 - PT360 1PT381 - PT399 1PT401 - PT438 1PT501 - PT512 2PT513 - PT517 1PT561 - PT565 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 15 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 16 GroupVariable Number 1PT581 - PT584 2PT585 - PT586 1PT611 - PT621 1PT641 - PT642 2PT643 - PT644 1PT651 - PT655 2PT656 1PT671 - PT672 2PT681 - PT685 1PT701 - PT703 2PT716 - PT717 2PT721 - PT725 2PT801 - PT834 2PT851 - PT854 2PT871 - PT886 2PT901 - PT930 2PT971 - PT973 2PT981 - PT985 2PT996 1PU001 - PU025 2PU301 2PU311 - PU313 1PV021 - PV055 1PV201 - PV203 2PV204 - PV209 2PV226 - PV229 1PV231 - PV237 1PV271 - PV272 1PV281 - PV283 2PV284 - PV287 2PV296 2PV301 - PV302 2PV351 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 16 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 17 GroupVariable Number 2PV356 - PV357 1PW027 - PW054 1PW061 - PW068 1PW072 2PW086 - PW088 1PW091 - PW094 1PW101 - PW102 1PW106 1PW111 - PW120 1PW156 - PW157 1PW161 - PW167 2PW168 - PW171 1PW201 - PW244 2PW245 - PW252 1PW261 2PW262 - PW264 1PW265 - PW268 2PW271 - PW276 1PW278 1PW281 2PW282 - PW292 1PW293 1PW296 1PW301 - PW327 2PW401 - PW408 2PW411 - PW418 2PW421 - PW424 2PW431 - PW435 2PW441 - PW450 1PW461 - PW467 1PW501 - PW502 1PW504 1PW511 - PW520 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 17 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 18 GroupVariable Number 2PW521 - PW522 2PW524 - PW525 1PW526 2PW527 - PW530 1PW531 - PW546 2PW547 - PW550 1PW556 - PW557 1PW561 - PW564 1PW571 - PW576 1PW591 - PW596 1PW611 - PW620 2PW621 - PW622 1PW631 - PW634 2PW635 - PW637 1PW661 - PW662 1PW681 - PW683 1PW701 - PW702 1PW711 - PW717 1PW741 - PW742 1PW761 1PW771 2PW831 2PW851 - PW856 2. Spares Affected None. B. Concurrent Requirements None. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 18 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 19 C. Reason Accomplishment of the inspections in this service bulletin will make sure that fuselage skin cracks at stringers S-1 and S-2R, between Body Stations STA 400 and STA 460 are found and repaired. An Air Traffic Control (ATC) antenna was installed at this location at delivery on the affected airplanes. All airplanes listed in this service bulletin require inspection even if the ATC antenna has been removed. This action is necessary to find and repair fatigue cracks of the skin panels at the chem-mill steps. Continued operation with undetected skin cracks could cause unscheduled down time for repairs or possibly a decompression of the airplane. Boeing has received several reports from multiple operators regarding fuselage skin cracks adjacent to the ATC antenna. A total of 60 cracks have been found on Group 1 airplanes (10 inch tear strap bays); cracks have been found at both S-1 and S-2R; the affected airplanes had accumulated between 40,080 and 67,032 total flight cycles. A total of 3 cracks have been found on Group 2 airplanes (20 inch tear strap bays); cracks have only been found at S-1, but similar cracking is possible at S-2R; the affected airplanes had accumulated between 43,565 and 44,700 total flight cycles. Analysis by Boeing indicates that the cracks are caused by fatigue due to high tension stresses and local bending at the edge of the chem-mill pockets of the bonded skin. The cracks initiate at the inner surface of the skin and typically originate at multiple sites along the chem-mill step. Multiple site originations can result in several adjacent partial-thickness cracks. These adjacent partial-thickness cracks can be subsequently linked together before propagating through the full-thickness of the skin. Accomplishment of the work given in this service bulletin will make sure that cracks in the fuselage skin at stringers S-1 and S-2R, between STA 400 and STA 460 are detected and repaired. Boeing Service Related Problem (SRP) 737-SRP-53-0334 is related to this service bulletin. Multi-Operator Message (MOM) MOM-MOM-09-0807-01B (R1) is related to this service bulletin. Revision 1 was sent to add more inspection areas, Ultrasonic Phased Array (UTPA) inspection procedure, post repair inspection and change compliance. The option to use a Detailed Inspection (DI) only has been removed. This revision requires that a Non Destructive Inspection (NDI) and a DI be accomplished. For Group 1 only, remove airplanes from the effectivity and add a repair. Revision 2 is sent to revise the group 1 repair figures and add the group 2 repair instructions and post repair inspection. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 19 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 20 D. Description 1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460. 3. Do external Non Destructive Inspections (NDI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460. The NDI's that can be used are Medium Frequency Eddy Current (MFEC), Magneto Optical Imaging (MOI), C-Scan or Ultrasonic Phased Array (UTPA). 4. If no crack is found, do repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 at intervals in accordance with Paragraph 1.E., Compliance. 5. Group 1: If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions, do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Paragraph 1.E., Compliance. a. Crack(s) found before 35,000 total flight cycles. b. Crack(s) found in four or more tear strap bays. c. Crack(s) found longer than 5 inches. d. Crack(s) found are not contained within the skin cut-out. If all of the following is found as a result of the external DI and NDI, do the repair, the critical fastener row inspection and repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps not covered by a repair at intervals specified in Paragraph 1.E., Compliance. a. Crack(s) found at or after 35,000 total flight cycles. b. Crack(s) found in three or less strap bays. c. Crack(s) found 5 inches or shorter. d. Crack(s) found are contained within the skin cut-out. 6. Group 2: If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions, do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Paragraph 1.E., Compliance. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 20 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 21 a. Crack(s) found before 33,000 total flight cycles. b. Crack(s) found between STA 400 and STA 420. c. Crack(s) found between STA 440 and STA 460. d. Crack(s) found longer than 12.5 inches. e. Crack(s) found are not contained within the skin cut-out. If all of the following is found as a result of the external DI and NDI, do the repair, the critical fastener row inspection and repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps not covered by a repair, at intervals specified in Paragraph 1.E., Compliance. a. Crack(s) found at or after 33,000 total flight cycles. b. Crack(s) found between STA 420 and STA 440. c. Crack(s) found 12.5 inches or shorter. d. Crack(s) found are contained within the skin cut-out. Revision 1 - More work is necessary on airplanes inspected as shown in the original issue of this service bulletin. Additional areas have been identified to be inspected for chem-mill line cracking, the Detailed Inspection must be done with a Non Destructive Inspection method, and the compliance times shown in Paragraph 1.E., Compliance have been reduced. Revision 2 - No more work is necessary on the airplanes changed in accordance with Revision 1 of this service bulletin. The work in this service bulletin is done in the maintenance zone(s) given below. Affected Maintenance Zones ZoneModel 107737-300, 737-400, 737-500 E. Compliance Federal Aviation Administration (FAA) Airworthiness Directive AD 2008-19-03 is related to this service bulletin. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 21 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 22 NOTE: If any repair in the Accomplishment Instructions, Paragraph 3.B., Work Instructions, is not applicable, contact Boeing for repair instructions and do the repair before further flight. Group 1, Configuration 1: Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 1,800 flight cycles after the date of Revision 1 on this ser- vice bulletin. Before 35,000 total flight cycles. Option 1: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instruction, Paragraph 3.B., PART 1. Airplanes not inspected in accordance with the original issue of this service bulletin. AND Do external Non Destructive Inspec- tions (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 using one of the following procedures: 1. Medium Frequency Eddy Current (MFEC) or 2. Magneto Optical Imaging (MOI) or 3. C-Scan (a) (c) OR Within 1,800 flight cycles after the date of Revision 1 on this ser- vice bulletin. Before 35,000 total flight cycles. Option 2: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instruction, Paragraph 3.B., PART 1. AND Do external Non Destructive Inspec- tions (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 using the Ultrasonic Phased Array (UTPA) pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 22 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 23 Group 1, Configuration 1: Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Do external DI and NDI of the fuse- lage skin chem-mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1. No crack found in the fuselage skin. AND Option 1 used. (b)(b) OR (a) (c) 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. No crack found in the fuselage skin. (b)(b)AND Option 2 used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 23 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 24 Group 1, Configuration 1: Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Contact Boeing for repair instructions in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 and do the repair. Crack(s) found before 35,000 total flight cy- cles. OR Cracks found in four or more tear strap bays. AND (do Option 1 or Option 2 ) 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Option 1: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Accomplishment In- structions, Paragraph 3.B., PART 3. OR Crack(s) longer than 5 inches. OR Crack(s) found are not contained within the skin cut-out. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. Option 2: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Accomplishment In- structions, Paragraph 3.B., PART 3. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 24 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 25 Group 1, Configuration 1: Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Do the repair in accordance with Ac- complishment Instructions, Paragraph 3.B., PART 2. Crack(s) found at or af- ter 35,000 total flight cycles. AND Cracks(s) found in three or fewer tear strap bays. AND (do Option 1 or Option 2 ) 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Option 1: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Accomplishment In- structions, Paragraph 3.B., PART 3. AND Crack(s) found 5 inches or shorter. AND Crack(s) found are contained within the skin cut-out. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. Option 2: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps (not covered by a repair) for cracks in accordance with Accomplishment In- structions, Paragraph 3.B., PART 3. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 25 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 26 Group 1, Configuration 1: Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following apply: 1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the circumferential direction. Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for repeat inspections under the repair area only. (b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if you do as follows: 1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections must be done within 1,800 flight cycle repeat intervals. Then Option 2 inspections that follow must be done within 2,400 flight cycle repeat intervals. 2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection must be done within 2,400 flight cycles after the Option 2 inspection. Then Option 1 inspections that follow must be done within 1,800 flight cycle repeat intervals. (c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 26 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 27 Group 1, Configuration 2, 4: Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 900 flight cycles after the date of Revision 1 on this ser- vice bulletin. Before 35,000 total flight cycles. Option 1: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 1. Airplanes inspected in accordance with the original issue of this service bulletin and the last inspection was De- tailed Inspection (DI) procedure. OR Airplanes inspected in accordance with Boeing Multi-Operator Mes- sage MOM-MOM-09- 0807-01B (R1) and the last inspection was De- tailed Inspection (DI) procedure. AND Do external Non Destructive Inspec- tions (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 using one of the following procedures: 1. Medium Frequency Eddy Current (MFEC) or 2. Magneto Optical Imaging (MOI) or 3. C-Scan (a) (c) OR -Within 900 flight cycles after the date of Revision 1 on this ser- vice bulletin. Before 35,000 total flight cycles. Option 2: Do external Detailed Inspection (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 1. AND Do external Non Destructive Inspec- tions (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 using the Ultrasonic Phased Array (UTPA) pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 27 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 28 Group 1, Configuration 2, 4: Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Do repeat external DI and NDI of the fuselage skin chem-mill steps for cracks in accordance with Accomplish- ment Instructions, Paragraph 3.B., PART 1. No crack found in the fuselage skin. AND Option 1 used. (b)(b) OR (a) (c) 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. No crack found in the fuselage skin. (b)(b)AND Option 2 used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 28 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 29 Group 1, Configuration 2, 4: Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Contact Boeing for repair instructions in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 and do the repair Crack(s) found before 35,000 total flight cy- cles. OR Cracks found in four or more tear strap bays. AND (do Option 1 or Option 2) 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Option 1: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. OR Crack(s) found longer than 5 inches. OR Crack(s) found are not contained within the skin cut-out. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. Option 2: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 29 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 30 Group 1, Configuration 2, 4: Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Do the repair in accordance with Ac- complishment Instructions, Paragraph 3.B., PART 2. Crack(s) found at or af- ter 35,000 total flight cycles. AND Cracks(s) found in three or fewer tear strap bays. AND (do Option 1 or Option 2) 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Option 1: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. AND Crack(s) found 5 inches or shorter. AND Crack(s) found are contained within the skin cut-out. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. Option 2: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 30 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 31 Group 1, Configuration 2, 4: Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following apply: 1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the circumferential direction. Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for repeat inspections under the repair area only. (b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if you do as follows: 1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections must be done within 1,800 flight cycle repeat intervals. Then Option 2 inspections that follow must be done within 2,400 flight cycle repeat intervals. 2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection must be done within 2,400 flight cycles after the Option 2 inspection. Then Option 1 inspections that follows must be done within 1,800 flight cycle repeat intervals. (c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 31 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 32 Group 1, Configuration 3, 5: Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 1,800 flight cycles after the date of Revision 1 on this ser- vice bulletin. Before 35,000 total flight cycles. Option 1: Do external Detailed Inspections (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 1. Airplanes inspected in accordance with the original issue of this service bulletin and the last inspection was a Non Destructive Inspec- tion (NDI) procedure. AND OR Do external Non Destructive Inspec- tion (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 using one of the following procedures: Airplanes inspected in accordance with Boeing Multi-Operator Mes- sage MOM-MOM-09- 0807-01B (R1) and the last inspection was a Non Destructive Inspec- tion (NDI) procedure. 1. Medium Frequency Eddy Current (MFEC) or 2. Magneto Optical Imaging (MOI) or 3. C-Scan (a) (c) OR Within 1,800 flight cycles after the date of Revision 1 on this ser- vice bulletin. Before 35,000 total flight cycles. Option 2: Do external Detailed Inspections (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 1. AND Do external Non Destructive Inspec- tion (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 using the Ultrasonic Phased Array (UTPA) pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 32 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 33 Group 1, Configuration 3, 5: Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Do repeat external DI and NDI of the fuselage skin chem-mill steps for cracks in accordance with Accomplish- ment Instructions, Paragraph 3.B., PART 1. No crack found in the fuselage skin. AND Option 1 used. (b)(b) OR (a) (c) 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. No crack found in the fuselage skin. (b)(b)AND Option 2 used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 33 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 34 Group 1, Configuration 3, 5: Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Contact Boeing for repair instructions in accordance with Accomplishment Instructions, Paragraph 3.B., PART 1 and do the repair. Crack(s) found before 35,000 total flight cy- cles. OR Crack(s) found in four or more tear strap bays. AND (do Option 1 or Option 2) 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Option1: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. OR Crack(s) found longer than 5 inches. OR Crack(s) found are not contained within the skin cut-out. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. Option 2: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 34 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 35 Group 1, Configuration 3, 5: Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Do the repair in accordance with Ac- complishment Instructions, Paragraph 3.B., PART 2. Crack(s) found at or af- ter 35,000 total flight cycles. AND Cracks(s) found in three or fewer tear strap bays. AND (do Option 1 or Option 2) 1,800 flight cy- cles. Within 1,800 flight cycles af- ter the last NDI. Option1: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. AND Crack(s) found 5 inches or shorter. AND Crack(s) found are contained within the skin cut-out. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 2,400 flight cy- cles. Within 2,400 flight cycles af- ter the last NDI. Option 2: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 3 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 35 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 36 Group 1, Configuration 3, 5: Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following apply: 1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the circumferential direction. Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for repeat inspections under the repair area only. (b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if you do as follows: 1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections must be done within 1,800 flight cycle repeat intervals. The Option 2 inspections that follow must be done within 2,400 flight cycle repeat intervals. 2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection must be done within 2,400 flight cycles after the Option 2 inspection. The Option 1 inspections that follows must be done within 1,800 flight cycle repeat intervals. (c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used. Group 1: Table 4: Post Repair - Critical Fastener Row Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 60,000 flight cycles from the time the repair was installed Do Detailed Inspections (DI) or Non Destructive Inspections (NDI) of the skin at the critical row of fasteners in the repair for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 4. Airplanes with a repair installed in accordance with this service bul- letin. In accordance with Repair As- sessment Guide- lines D6-38669 Revision C Fig- ure 2-9. In accordance with Repair Assessment Guidelines D6- 38669 Revision C Figure 2- 9. Do repeat DI or NDI of the skin at the critical row of fasteners in the repair for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 4. No crack found. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 36 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 37 Group 1: Table 4: Post Repair - Critical Fastener Row Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Contact Boeing for repair instructions in accordance with Accomplishment Instructions, Paragraph 3.B., PART 4 and do the repair. Any crack found. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 37 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 38 Group 2: Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 500 flight cycles after the re- lease date of Revision 1 on this service bulletin. Before 33,000 total flight cycles. Option 1: Do external Detailed Inspections (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 5. AND All Airplanes Do external Non Destructive Inspec- tions (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 5 using one of the following procedures: 1. Medium Frequency Eddy Current (MFEC) or 2. Magneto Optical Imaging (MOI) or 3. C-Scan (a) (c) OR -Within 500 flight cycles after the re- lease date of Revision 1 on this service bulletin. Before 33,000 total flight cycles. Option 2: Do external Detailed Inspections (DI) of the fuselage skin chem-mill steps for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., PART 5. AND Do external Non Destructive Inspec- tions (NDI) of the fuselage skin chem- mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 5 using the Ultrasonic Phased Array (UTPA) pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 38 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 39 Group 2: Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles.Within 500 flight cycles after the last NDI. Do repeat external NDI of the fuselage skin chem-mill steps for cracks in ac- cordance with Accomplishment Instruc- tions, Paragraph 3.B., PART 5. No crack found in the fuselage skin. AND Option 1 used. (b) (b) (a) (c)OR 1,000 flight cy- cles. Within 1,000 flight cycles af- ter the last NDI. No crack found in the fuselage skin. (b)(b)AND Option 2 used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 39 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 40 Group 2: Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Contact Boeing for repair instructions in accordance with Accomplishment Instructions, Paragraph 3.B., PART 5 and do the repair. Crack(s) found before 33,000 total flight cy- cles. OR Crack(s) found between STA 400 and STA 420. AND (do Option 1 or Option 2) 500 flight cycles.Within 500 flight cycles after the last NDI. Option 1: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6. OR Crack(s) found between STA 440 and STA 460. OR Crack(s) found longer than 12.5 inches. OR (b) (b) AND Crack(s) found are not contained within the skin cut-out. Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 1,000 flight cy- cles. Within 1,000 flight cycles af- ter the last NDI. Option 2: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 40 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 41 Group 2: Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Do the repair in accordance with Ac- complishment Instructions, Paragraph 3.B., PART 7. Crack(s) found at or af- ter 33,000 total flight cycles. AND Crack(s) found between STA 420 and STA 440. AND (do Option 1 or Option 2) 500 flight cycles.Within 500 flight cycles after the last NDI. Option 1: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6. AND Crack(s) found 12.5 inches or shorter. AND Crack(s) found are contained within the skin cut-out. (b) (b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6 using one of the following procedures: 1. MFEC or 2. MOI or 3. C-Scan (a) (c) OR 1,000 flight cy- cles. Within 1,000 flight cycles af- ter the last NDI. Option 2: Do external DI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6. (b)(b) AND Do external NDI of the fuselage skin chem-mill steps (not covered by a re- pair) for cracks in accordance with Accomplishment Instructions, Para- graph 3.B., PART 6 using UTPA pro- cedure. (a) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 41 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 42 Group 2: Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460 Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following apply: 1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the circumferential direction. Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for repeat inspections under the repair area only. (b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if you do as follows: 1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. The Option 2 inspections that follow must be done within 1000 flight cycle repeat intervals. 2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspection. The Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. (c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used. Group 2: Table 6: Post Repair - Critical Fastener Row Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 60,000 flight cycles from the time the repair was installed. Do a Non Destructive inspection (NDI) of the skin at the critical row of fasten- ers in the repair for cracks in accor- dance with Accomplishment Instruc- tions, Paragraph 3.B., Part 8. Airplanes with a repair installed in accordance with this service bul- letin. 6,000 flight cy- cles. Within 6,000 flight cycles af- ter the last NDI. Do a repeat NDI of the skin at the critical row of fasteners in the repair for cracks in accordance with Accom- plishment Instructions, Paragraph 3.B., Part 8. No crack found. -Before further flight.Contact Boeing for repair instructions in accordance with Accomplishment Instructions, Paragraph 3.B., Part 8 and do the repair. Any crack found. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 42 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 43 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 or as modified by other approved Boeing changes. If an airplane has a non-Boeing modification or 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. In addition the Manager of the FAA Seattle Aircraft Certification Office approves the inspection methods and corrective actions in Tables 1, 2, 3 and 5 under Paragraph 1.E., Compliance of this service bulletin, as an alternative method of compliance to the inspection methods and corrective actions specified in Table 1 and 2, under Paragraph 1.E., Compliance of the Original Issue of this service bulletin, dated August 13, 2008, required by paragraphs (f) and (g) of AD 2008-19-03. The compliance times remain unchanged from those defined in AD 2008-19-03. When this service bulletin specifies contacting Boeing for repair instructions, the repair instructions must be approved by the FAA in accordance with paragraph (h) of AD 2008-19-03. All provisions of AD 2008-19-03 that are not specifically referenced in this paragraph remain fully applicable and must be complied with accordingly. 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. 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: Table 1 - Skin Panel Inspection and Repair. Elapsed HoursTask HoursNumber of Per- sons Task 0.250.251Get Access 2.755.502FIGURE 2 or FIGURE 7 (a)--FIGURE 5 (a)--FIGURE 6 or FIGURE 8 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 43 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 44 Group 1: Table 1 - Skin Panel Inspection and Repair. Elapsed HoursTask HoursNumber of Per- sons Task 4.25 (b)8.50 (b)2Inspection 0.250.251Close Access 5.7514.50TOTAL FOR EACH AIRPLANE (a) The time to make any repair is not included. More time is required for repairs if any damage is found. (b) Includes time to access interior and inspect interior and exterior of one typical repair location for the critical fastener row. Group 2: Table 2 - Skin Panel Inspection and Repair. Elapsed HoursTask HoursNumber of Per- sons Task 0.250.251Get Access 3.006.002FIGURE 4 or FIGURE 9 (a)--FIGURE 10 (a)--FIGURE 11 1.50 (b)3.002FIGURE 12 0.250.251Close Access 5.009.50TOTAL FOR EACH AIRPLANE (a) The time to make any repair is not included. More time is required for repairs if any damage is found. (b) Includes time to access interior and inspect interior and exterior of one typical repair location for the critical fastener row. H. Weight and Balance Changes All airplanes: 1. Calculate the change in weight for each repair installation as follows: a. Calculate the gross area of each repair doubler in square inches (Length x Width). BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 44 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 45 Example for FIGURE 6: Length = approximately 20 inches and Width = approximately 12 inches. Area = 240 square inches. (Calculation ignores the curvature of the fuselage, holes and rounding of corners). b. To calculate the weight for each repair doubler installed, including fasteners, paint and sealant, multiply the repair doubler area (from step 1.a) by 0.006 lb per sq in. Example for FIGURE 6: Change in Weight = 240 x 0.006 = 1.4 pounds rounded to nearest 1/10 pound. 2. Calculate the change in moment for each repair installation as follows: a. Record the station of the geometric center of each repair doubler. Example for FIGURE 6: By inspection, station = 435. b. To calculate the change in moment for each repair doubler, use the formula for each model as follows: – For Model 737-300: change in weight from step 1.b. x (station from step 2.a. - 80) = Change in Moment. – For Model 737-400: change in weight from step 1.b. x (station from step 2.a. - 152) = Change in Moment. – For Model 737-500: change in weight from step 1.b. x (station from step 2.a. - 26) = Change in Moment. Example for FIGURE 6, Model 737-300: 1.4 x (435 - 80) = 500 Pound-Inches rounded to nearest 10 pound-inch. 3. If multiple repair doublers are installed, treat each one individually and then sum the weights and moments. I. Electrical Load Data Not changed. J. References 1. Existing Data a. Boeing Service Letter 737-SL-51-042 b. Boeing Service Related Problem (SRP) 737-SRP-53-0334 c. Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2008-19-03 d. Standard Overhaul Practices Manual (SOPM) 20-43-03, 20-44-03 , 20-44-04 e. 737 Non-Destructive Testing (NDT) Manual Part 4, 53-30-07, Part 6, 51-00-00, Figure 16, Part 6, 51-00-00 Figure 23 , Part 6, 51-00-00 Figure 4, Part 6, 53-30-00, Figure 5, Part 6, 53-30-00, Figure 6, Part 6, 53-30-09, Part 6, 53-30-18, Part 6, 53-30-19, Part 6, 53-30-25 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 45 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 46 f. 737-300/400/500 Aircraft Maintenance Manual (AMM) 25-21-39, 25-21-45, 25-21-46, 25-22-00, 25-23-61, 25-24-31, 34-53-11, 51-21-00 g. 737-300 Structural Repair Manual (SRM) 51-10-01, 51-20-01 , 51-20-05, 51-30-01, 51-40, 51-40-08 h. 737-400 Structural Repair Manual (SRM) 51-10-01, 51-20-01 , 51-20-05, 51-30-01, 51-40, 51-40-08 i. 737-500 Structural Repair Manual (SRM) 51-10-01, 51-20-01 , 51-20-05, 51-30-01, 51-40, 51-40-08 j. Multi-Operator Message (MOM) MOM-MOM-09-0807-01B (R1) k. Airplane Flight Manual Appendix 53 l. Repair Assessment Guidelines - Model 737-100 to -500 Document Number D6-38669 Rev C m. Service Bulletin Index Document D6-19567 Part 3 2. Data supplied with this Service Bulletin None. 3. Installation Drawings Used in the Preparation of this Service Bulletin TitleDrawing Number SKIN PANEL INSTALLATION - S-10L TO S-10R STA 360 - STA 54065-45765 SKIN INSTALLATION - S-10L TO S-10R, STA 360 TO STA 54065C35765 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: 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. DTI requirements for the structure affected are contained in Paragraph 1.E., Compliance of this service bulletin. L. Interchangeability and Intermixability of Parts Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 46 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 47 2. MATERIAL INFORMATION A. Material - Price and Availability The operator can supply the parts and materials shown in Paragraph 2.C., Parts Necessary for Each Airplane . As an alternative, operators can purchase the parts from Boeing Spares. This service bulletin does not show the Boeing price and supply data. B. Industry Support Information Boeing warranty remedies are not available for the inspection,and 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 Group 1: Table 1 NotesNameQTYPart Number / Specification (a) (b) (c) (d)RIVET-BACR15BB5D (a) (b) (c) (d)RIVET-BACR15BB6AD (a) (b) (c) (d)RIVET-BACR15BB6D (a) (b) (c) (d)RIVET-BACR15CE5D (b) (c)ORGANIC CORROSION INHIBIT- ING COMPOUND -BMS 3-23 TYPE II (b) (c)SEALANT-BMS 5-95 (b) (c)REPAIR DOUBLER MATERIAL-2024-T3 CLAD Sheet X 0.050 thick (b) (c)TEAR STRAP DOUBLER MATERI- AL -2024-T3 CLAD Sheet X 0.040 thick (a) Refer to 737-300/-400/-500 Structural Repair Manual Chapter 51 for alternate fasteners. (b) Quantities to be determined by the size of the repair. (c) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data. (d) Fastener grip length to be determined on assembly. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 47 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 48 Group 2: Table 2 NotesNameQTYPart Number / Specification (a)2024-T3 Clad Sheet x 0.050 inches thick. 40 inches x 30 inches AMS QQ-A-250/5 (b)2024-T3 Clad Sheet x 0.040 inches thick. 24 inches x 5 inches AMS QQ-A-250/5 (c) (d)Rivet16BACR15BB6D5C (c) (d)Rivet32BACR15BB6D6C (c) (d)Rivet124BACR15GF5D4 (c) (d)Rivet166BACR15GF5D5 (c) (d)Rivet51BACR15GF5D6 (c) (d)Rivet68BACR15BB6AD5C (e)Chemical Conversion Coating2 ounces TYPE 2, CLASS A (f)Primer3 ounces BMS 10-79, TYPE III (f)Sealant5 ounces BMS 5-95, TYPE I, CLASS B-1/2 OR B-2 (f)Organic Corrosion Inhibiting Com- pound 2 ounces BMS 3-23, TYPE II (a) Use to make the external repair doubler in accordance with FIGURE 11. (b) Use to make tear strap doublers in accordance with FIGURE 11. (c) Refer to 737-300/-400/-500 Structural Repair Manual Chapter 51 for alternate fasteners. (d) Fastener grip length to be determined on assembly. (e) Refer to SOPM 20-43-03 for material sources. (f) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data. 3. Parts Modified and Reidentified None. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 48 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 49 4. Parts Removed and Not Replaced None. D. Parts Necessary to Change Spares None. E. Special Tooling - Price and 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. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 49 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 50 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 50 of 105 BOEING SERVICE BULLETIN 737-53A1293 BLANK PAGE ### Page 51 3. ACCOMPLISHMENT INSTRUCTIONS A. GENERAL INFORMATION CAUTION: KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL, METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR OTHER ELECTRICAL DAMAGE. NOTE: 1. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for definition of the acronyms. 2. Obey all of the warnings and cautions given in the specified manual sections. 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 are in 737-300/-400/-500 SRM Chapter 51. 4. Maintain a 2D minimum edge margin on all parts unless otherwise stated. 5. All machined surfaces must have a finish of 125 micro-inch Ra or better. Refer to Figure 1 of 737-300 SRM 51-10-01, 737-400 SRM 51-10-01, 737-500 SRM 51-10-01 as an accepted procedure. 6. Clean repair parts and mating surfaces. Refer to 737-300 SRM 51-20-05, 737-400 SRM 51-20-05, and 737-500 SRM 51-20-05 as an accepted procedure. 7. For fastener installation refer to 737-300 SRM 51-40, 737-400 SRM 51-40 or 737-500 SRM 51-40 as an accepted procedure. 8. Use the approved fastener and process material substitutions in accordance with SRM Chapter 51. 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. 10. Boeing Service Letter 737-SL-51-042, Damage Reporting and Repair Plan/Design Guidelines, is an acceptable procedure to request information from Boeing for additional structural repair instructions. The Service Letter describes what information must be provided to Boeing before a structural repair can be provided. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 51 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 52 11. A Detailed Inspection is defined as: An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be necessary. Surface cleaning and elaborate access procedures may be required. 12. 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. 13. If chem-mill step crack damage is found and the damage is within the SB damage limits and the airplane is above the SB threshold, Boeing would still like to obtain the information relative to the damage in order to develop more refined inspection requirements. Report crack damage in accordance with APPENDIX B. 14. 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. 15. 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. The removed part can be discarded if a new or serviceable part is installed. B. WORK INSTRUCTIONS Group 1: PART 1 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400 - STA 460 1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 in accordance with FIGURE 2. 3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 in accordance with FIGURE 2. a. Option 1: Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan. b. Option 2: Ultrasonic Phased Array (UTPA). 4. If no crack is found, do repeat external DI and NDI in accordance with PART 1 at intervals in accordance with Paragraph 1.E., Compliance. 5. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions in accordance with APPENDIX A, do the repair and do the inspection of the fuselage skin not covered by a repair in accordance with PART 3 at intervals in accordance with Paragraph 1.E., Compliance. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 52 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 53 a. Crack(s) found before 35,000 total flight cycles. b. Crack(s) found in four or more tear strap bays. c. Crack(s) found longer than 5 inches. d. Crack(s) found are not contained within the skin cut-out shown in FIGURE 5. 6. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance with PART 2 and do the inspection of the fuselage skin not covered by a repair in accordance with PART 3 at intervals in accordance with Paragraph 1.E., Compliance. a. Crack(s) found at or after 35,000 total flight cycles. b. Crack(s) found in three or fewer tear strap bays. c. Crack(s) found 5 inches or shorter. d. Crack(s) found are contained within the skin cut-out shown in FIGURE 5. 7. Put the airplane back to a serviceable condition. Group 1: PART 2 - SKIN REPAIR 1. In the passenger cabin, remove and keep the equipment listed in the table below to access the area of repair. Refer to the listed Aircraft Maintenance Manual (AMM) as an accepted procedure. AMM Chapter/Section/SubjectEquipment 737-300/400/500 AMM 25-22-00Passenger Seats 737-300/400/500 AMM 25-21-46Sidewall Lining 737-300/400/500 AMM 25-21-39Sidewall insulation 737-300/400/500 AMM 25-24-31Overhead Stowage Bins 737-300/400/500 AMM 25-23-61Passenger Service Units 737-300/400/500 AMM 25-21-45Ceiling Panels 2. Remove and keep ATC antenna if required, refer to 737-300/400/500 AMM 34-53-11 as an accepted procedure. 3. Remove the crack in accordance with FIGURE 5 . 4. Make and install the repair doubler and tear strap doublers in accordance with figure listed below: FigureAirplanes Series FIGURE 6737-300, 737-400 FIGURE 8737-500 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 53 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 54 5. If ATC antenna was removed to do the repair, install kept ATC antenna on top of repair doubler. Refer to 737-300/400/500 AMM 34-53-11 as an accepted procedure. 6. Install kept equipment in the passenger cabin that was removed for access. 7. Accomplish the Part 4 - Post Repair inspections at the times specified in Table 4 of Paragraph 1.E., Compliance. 8. Put airplane back in a serviceable condition. Group 1: PART 3 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1 AND S-2R, STA 400 - STA 460 1. Get external access to skin repair area at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 not covered by a repair in accordance with FIGURE 7. 3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 not covered by a repair in accordance with FIGURE 7. a. Option 1: Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan. b. Option 2: Ultrasonic Phased Array (UTPA). 4. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions in accordance with APPENDIX A and do the repair: a. Crack(s) found before 35,000 total flight cycles. b. Crack(s) found in four or more tear strap bays. c. Crack(s) found longer than 5 inches. d. Crack(s) found are not contained within the skin cut-out shown in FIGURE 5. 5. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance with PART 2. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 54 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 55 a. Crack(s) found at or after 35,000 total flight cycles. b. Crack(s) found in three or fewer tear strap bays. c. Crack(s) found 5 inches or shorter. d. Crack(s) found are contained within the skin cut-out shown in FIGURE 5. 6. Repeat external DI and NDI in accordance with PART 3 at intervals in accordance with Paragraph 1.E., Compliance. 7. Put the airplane back to a serviceable condition. Group 1: PART 4 - POST REPAIR - CRITICAL FASTENER ROW INSPECTION 1. Get access to skin repair at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do Non Destructive Inspection (NDI) or Detailed Inspection (DI) of the skin at the critical row of fasteners in the repair for cracks in accordance with Repair Assessment Guidelines D6-38669 Revision C Figure 2-9. NOTE: The NDI procedures given in the Options column of Figure 2-9 in D6-38669 Revision C should be changed as follows: 1. Use 737 NDT Part 6, 53-30-00, Figure 6 in place of 53-30-3 Figure 6. 2. Use 737 NDT Part 6, 53-30-00, Figure 5 in place of 53-30-3 Figure 5. 3. If crack is found contact Boeing for repair instructions and do the repair. 4. Repeat post repair inspection in accordance with PART 4 at intervals in accordance with Paragraph 1.E., Compliance. 5. Put the airplane back to a serviceable condition. Group 2: PART 5 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400 - STA 460 1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do external Detail Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 in accordance with FIGURE 4. 3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 in accordance with FIGURE 4. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 55 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 56 a. Option 1: Medium Frequency Eddy Current (MFEC), or Magneto Optical Imaging (MOI) or C-Scan b. Option 2: Ultrasonic Phased Array (UTPA). 4. If no crack is found, repeat external DI and NDI in accordance with PART 5 at intervals in accordance with Paragraph 1.E., Compliance. 5. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions in accordance with APPENDIX A, do the repair and do the inspection of the fuselage skin not covered by a repair in accordance with PART 6 at intervals in accordance with Paragraph 1.E., Compliance. a. Crack(s) found before 33,000 total flight cycles. b. Crack(s) found between STA 400 and STA 420. c. Crack(s) found between STA 440 and STA 460. d. Crack(s) found longer than 12.5 inches. e. Crack(s) found are not contained within the skin cut-out shown in FIGURE 10. 6. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance with PART 7 and do the inspection of the fuselage skin not covered by a repair in accordance with PART 6 at intervals in accordance with Paragraph 1.E., Compliance. a. Crack(s) found at or after 33,000 total flight cycles. b. Crack(s) found between STA 420 and STA 440. c. Crack(s) found 12.5 inches or shorter. d. Crack(s) found are contained within the skin cut-out shown in FIGURE 10. 7. Put the airplane back to a serviceable condition. Group 2: PART 6 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1 AND S-2R, STA 400 - STA 460 1. Get external access to skin repair area at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 not covered by a repair in accordance with FIGURE 9. 3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400 and STA 460 not covered by a repair in accordance with FIGURE 9. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 56 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 57 a. Option 1: Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan. b. Option 2: Ultrasonic Phased Array (UTPA). 4. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions in accordance with APPENDIX A, and do the repair. a. Crack(s) found before 33,000 total flight cycles. b. Crack(s) found between STA 400 and STA 420. c. Crack(s) found between STA 440 and STA 460. d. Crack(s) found longer than 12.5 inches. e. Crack(s) found are not contained within the skin cut-out shown in FIGURE 10. 5. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance with PART 7. a. Crack(s) found at or after 33,000 total flight cycles. b. Crack(s) found between STA 420 and STA 440. c. Crack(s) found 12.5 inches or shorter. d. Crack(s) found are contained within the skin cut-out shown in FIGURE 10. 6. Repeat external DI and NDI in accordance with PART 6 at intervals in accordance with Paragraph 1.E., Compliance. 7. Put the airplane back to a serviceable condition. Group 2: PART 7 - SKIN REPAIR 1. In the passenger cabin, remove and keep the equipment listed in the table below to access the area of repair. Refer to the listed Aircraft Maintenance Manual (AMM) as an accepted procedure. AMM Chapter/Section/SubjectEquipment 737-300/400/500 AMM 25-22-00Passenger Seats 737-300/400/500 AMM 25-21-46Sidewall Lining 737-300/400/500 AMM 25-21-39Sidewall insulation 737-300/400/500 AMM 25-24-31Overhead Stowage Bins 737-300/400/500 AMM 25-23-61Passenger Service Units BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 57 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 58 AMM Chapter/Section/SubjectEquipment 737-300/400/500 AMM 25-21-45Ceiling Panels 2. Remove and keep the ATC antenna, refer to 737-300/400/500 AMM 34-53-11 as an accepted procedure. 3. Remove the crack in accordance with FIGURE 10. 4. Make and install the repair doubler and tear strap doublers in accordance with FIGURE 11. 5. Install the kept ATC antenna on top of the repair doubler. Refer to 737-300/400/500 AMM 34-53-11 as an accepted procedure. NOTE: Longer ATC antenna mounting screws may be necessary as a result of installing the repair doubler. 6. Install kept equipment in the passenger cabin that was removed for access. 7. Accomplish the Part 8 - Post Repair inspections at the times specified in Table 6 of Paragraph 1.E., Compliance. 8. Put airplane back in a serviceable condition. Group 2: PART 8 - POST REPAIR - CRITICAL FASTENER ROW INSPECTION 1. Get external access to the skin repair at stringers S-1 and S-2R, between STA 400 and STA 460. 2. Do an external Non Destructive Inspection (NDI) in accordance with FIGURE 12 for cracks in the fuselage skin, at the critical row of fasteners in the repair. a. If any crack is found contact Boeing for repair instructions and do the repair. 3. Repeat post repair inspection in accordance with PART 8 at intervals in accordance with Paragraph 1.E., Compliance. 4. Put the airplane back to a serviceable condition. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 13, 2008 737-53A1293Revision 2: August 10, 2011 58 of 105 BOEING SERVICE BULLETIN 737-53A1293 ### Page 59 (OCR) BOEING SERVICE BULLETIN 737-53A1293 This Figure applies only to: Group 1. THIS FIGURE IS DELETED. 1553909 GURE 1: THIS FIGURE DELETED AT REVISION SHEET T OF ' Revision 2 : As 10, 20110 |. 201* 737-53A1293 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 59 of 105 ### Page 60 (OCR) BOEING SERVICE BULLETIN 737-53A1293 This Figure applies only to: Group 1. STA 460 STA 400 0000 TYPICAL CRACKS - S-2R STA STA STA STA STA STA STA 460 450 440 430 420 410 400 ATC ANTENNA INSPECTION AREA FIGURE 2: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400 - STA 460 (SHEET 1 OF 2) Original Issue: August 13, 2008 Revision 2 August 10, 2011 737-53A1293 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 60 of 105 The text continues at https://openairdocs.org/service-documents/boeing/737-53a1293/file/197a64a52da0.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.