# Boeing Alert Service Bulletin 737-53A1234: Revision 2 - Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2011-1419; AD 2012-26-02 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Boeing Alert Service Bulletin 737-53A1234](https://openairdocs.org/service-documents/boeing/737-53a1234.md) - Title as filed: Boeing - Service Bulletin - Pages: 247 - PDF: https://openairdocs.org/files/sha256/78/a5/78a5bdc1024698cacbd0b59294170af6da8e7db49e90a0b10cdaf48818b6b002 - Page: https://openairdocs.org/service-documents/boeing/737-53a1234/file/78a5bdc10246 ## 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 ALERT Number: 737-53A1234 Original Issue: June 13, 2002 Revision 2: November 24, 2010 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Cracks at Chem-milled Steps - 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all export laws. 9E991ECCN: BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2002 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter.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 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.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: June 13, 2002 737-53A1234Revision 2: November 24, 2010 1 of 247 6.0 ### Page 2 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 2 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT 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 5 B. Concurrent Requirements ...................................... 1 5 C. Reason ................................................ 1 5 D. Description .............................................. 1 6 E. Compliance .............................................. 1 8 F. Approval ............................................... 3 5 G. Manpower .............................................. 3 6 H. Weight and Balance Changes .................................... 4 0 I. Electrical Load Data ......................................... 4 1 J. References .............................................. 4 1 1. Existing Data: ......................................... 4 1 2. Data supplied with this Service Bulletin: ........................... 4 1 3. Installation Drawings Used in the Preparation of this Service Bulletin: ........... 4 2 K. Publications Affected ........................................ 4 2 L. Interchangeability and Intermixability of Parts ........................... 4 2 2. MATERIAL INFORMATION ........................................ 4 3 A. Material - Price and Availability ................................... 4 3 B. Industry Support Information .................................... 4 3 C. Parts Necessary For Each Airplane ................................. 4 3 1. Kits/Parts: ........................................... 4 3 2. Parts and Materials Supplied by the Operator: ........................ 4 3 3. Parts Modified and Reidentified: ............................... 4 5 4. Parts Removed and Not Replaced: .............................. 4 5 D. Parts Necessary to Change Spares ................................. 4 5 E. Special Tooling - Price and Availability ............................... 4 5 F. Special Tooling Necessary to do this Service Bulletin ....................... 4 5 3. ACCOMPLISHMENT INSTRUCTIONS .................................. 4 7 A. GENERAL INFORMATION ..................................... 4 7 B. WORK INSTRUCTIONS ....................................... 4 8 FIGURE 1: LOGIC DIAGRAM - SKIN INSPECTIONS IN THE CROWN AREA ............. 5 8 FIGURE 2: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 1] .......... 5 9 FIGURE 3: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 3] .......... 6 2 FIGURE 4: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 4] .......... 6 5 FIGURE 5: FUSELAGE - STRINGER 4 PERMANENT SKIN REPAIR .................. 6 8 FIGURE 6: FUSELAGE - STRINGER 4 - 3.0-3.54 INCH TEAR STRAP WIDTH ONLY - TIME LIMITED SKIN REPAIR ............................................. 8 0 FIGURE 7: INSPECTION OF THE TIME-LIMITED SKIN REPAIR .................... 8 5 FIGURE 8: LOGIC DIAGRAM FOR OPERATIONAL INSPECTIONS OF THE TIME-LIMITED SKIN REPAIR .................................................. 8 6 FIGURE 9: FUSELAGE - STRINGER 4 TIME LIMITED SKIN REPAIR PERMANENT MODIFICATION . 87 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 3 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 4 FIGURE 10: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 2] .......... 9 7 FIGURE 11: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 1] ......... 1 0 0 FIGURE 12: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 2] ......... 1 0 3 FIGURE 13: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 3] ......... 1 0 6 FIGURE 14: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 4] ......... 1 0 9 FIGURE 15: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 3] ......... 1 1 2 FIGURE 16: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 1] ......... 1 1 5 FIGURE 17: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 2] ......... 1 1 8 FIGURE 18: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 3] ......... 1 2 1 FIGURE 19: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION [Group 4] ......... 1 2 4 FIGURE 20: FUSELAGE - CROWN AREA SKIN SHEAR WRINKLE INSPECTION [Group 1] ..... 1 2 7 FIGURE 21: FUSELAGE - CROWN AREA SKIN SHEAR WRINKLE INSPECTION [Group 2] ..... 1 3 1 FIGURE 22: FUSELAGE - CROWN AREA SKIN SHEAR WRINKLE INSPECTION [Group 3] ..... 1 3 5 FIGURE 23: FUSELAGE - CROWN AREA SKIN SHEAR WRINKLE INSPECTION [Group 4] ..... 1 3 9 FIGURE 24: FUSELAGE - CROWN AREA SKIN BUTT JOINT INSPECTION [Group 1] ........ 1 4 3 FIGURE 25: FUSELAGE - CROWN AREA SKIN BUTT JOINT INSPECTION [Group 2] ........ 1 4 7 FIGURE 26: FUSELAGE - CROWN AREA SKIN BUTT JOINT INSPECTION [Group 3] ........ 1 5 1 FIGURE 27: FUSELAGE - CROWN AREA SKIN BUTT JOINT INSPECTION [Group 4] ........ 1 5 5 FIGURE 28: FUSELAGE - CROWN AREA SKIN INSPECTION [Group 1] ................ 1 5 9 FIGURE 29: FUSELAGE - CROWN AREA SKIN INSPECTION [Group 2] ................ 1 6 3 FIGURE 30: FUSELAGE - CROWN AREA SKIN INSPECTION [Group 3] ................ 1 6 7 FIGURE 31: FUSELAGE - CROWN AREA SKIN INSPECTION [Group 3] ................ 1 7 1 FIGURE 32: FUSELAGE - CROWN AREA SKIN INSPECTION [Group 4] ................ 1 7 5 FIGURE 33: FUSELAGE - CROWN AREA SKIN INSPECTION ..................... 1 7 9 FIGURE 34: FUSELAGE - STRINGER 10 PERMANENT SKIN REPAIR ................ 1 8 2 FIGURE 35: FUSELAGE - STRINGER 4 - 3.88-4.30 INCH TEAR STRAP WIDTH ONLY - TIME LIMITED SKIN REPAIR ......................................... 1 9 3 FIGURE 36: FUSELAGE - STRINGER 10 - 3.0-3.54 INCH TEAR STRAP WIDTH ONLY - TIME LIMITED SKIN REPAIR ......................................... 1 9 8 FIGURE 37: FUSELAGE - STRINGER 10 TIME LIMITED SKIN REPAIR PERMANENT MODIFICATION ................................................. 2 0 3 FIGURE 38: FUSELAGE - STRINGER 4 INTERNAL TEAR STRAP DOUBLER INSTALLATION . . . 212 FIGURE 39: FUSELAGE - STRINGER 10 INTERNAL TEAR STRAP DOUBLER INSTALLATION . . 219 FIGURE 40: FUSELAGE - PERMANENT LAP JOINT REPAIR WITH INTERNAL TEAR STRAP DOUBLERS PART 26 INSPECTIONS ................................... 2 2 6 FIGURE 41: FUSELAGE - PERMANENT LAP JOINT REPAIR WITHOUT INTERNAL TEAR STRAP DOUBLERS PART 26 INSPECTIONS ............................ 2 2 8 APPENDIX A: SKIN DRAWINGS FOR CHEM-MILL POCKET LOCATIONS ............... 2 3 0 APPENDIX B: NDI INSPECTION DETAIL .................................. 2 4 7 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 4 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 5 Commercial Airplanes 737 Service Bulletin ALERT Revision Transmittal SheetNumber: 737-53A1234Original Issue: June 13, 2002 Revision 2: November 24, 2010 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Cracks at Chem-milled Steps - Inspection and Repair This revision includes all pages of the service bulletin. COMPLIANCE INFORMATION RELATED TO THIS REVISION Federal Aviation Administration (FAA) Airworthiness Directive 2005-13-27, is related to this service bulletin. More work is necessary on airplanes inspected in accordance with the original issue and Revision 1 of this service bulletin. Additional areas have been identified to be inspected for horizontal chem-mill cracks and new inspections for vertical chem-mill cracks are now required. Previously repaired areas require additional repairs. REASON FOR REVISION This revision is sent to add additional inspections for horizontal chem-mill cracks away from the lap joints over the entire crown, new inspections for vertical chem-mill cracks adjacent to the butt joints and adding internal tear strap doublers at the tear straps adjacent to existing permanent repairs. The airplane effectivity is divided into 4 groups as follows: Group 1 - 737-300 airplanes line number 2553 through 3132 excluding airplane variable numbers PS763-PS799, PS901-PS906. Group 2 - 737-300 airplanes with variable numbers PS763-PS799, PS901-PS906. Group 3 - 737-400 airplanes line number 2553 through 3132. Group 4 - 737-500 airplanes line number 2553 through 3132. These sections were changed: 1. Paragraph 1.C.Reason - added more background information 2. Paragraph 1.D.Description - added more inspection information 3. Added maintenance zone tables 4. Paragraph 1.E.Compliance - added new compliance tables 5. Paragraph 1.F.Approval - added AD information 6. Paragraph 1.G.Manpower - adjusted Task-Hours 7. Paragraph 1.J.References - added NDT references and AD number BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 5 of 247 ### Page 6 8. Paragraph 1.K.Publications Affected - added DTI statement 9. Paragraph 3.B. Work Instructions - added additional inspection information 10. Figure 1 - deleted and replaced by tables in Paragraph 1.E.Compliance 11. Figure 2 - Figure 4 - added new inspection areas 12. Figure 5, Figure 6, Figure 9 - updated repairs 13. Figure 7, Figure 8 - deleted and replaced by other figures 14. Figure 10 - Figure 19 - new crown skin lap joint inspections 15. Figure 20 - Figure 23 - new crown skin shear wrinkle inspections 16. Figure 24 - Figure 27 - new crown skin butt joint inspections 17. Figure 28 - Figure 33 - new crown area skin inspections 18. Figure 34 - Figure 39 - new repairs/modifications 19. Figure 40, Figure 41 - new part 26 inspections 20. Appendix A - reference for skin drawings 21. Appendix B - NDI inspection detail 22. Added a new effectivity group and modified group references throughout 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 June 13, 2002Original Issue: March 31, 2005Revision 1: November 24, 2010Revision 2: BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 6 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 7 Commercial Airplanes 737 Service Bulletin ALERT SummaryNumber: 737-53A1234Original Issue: June 13, 2002 Revision 2: November 24, 2010 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Cracks at Chem-milled Steps - Inspection and Repair THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OWNER. CONCURRENT REQUIREMENTS None BACKGROUND Accomplishment of the inspections and repairs shown in this service bulletin will ensure that fuselage skin cracks at specified locations are found and repaired. Continued operation with undetected skin cracks could cause unscheduled down time for repairs or possibly a decompression of the airplane. Two operators have reported 77 horizontal chem-mill cracks just above the Stringer (S)-4 and S-10 lap joints on airplanes with 20 inch tear strap spacing. The airplanes had between 30,000 and 46,000 flight cycles at the time the cracks were discovered. One operator has reported 9 cases of horizontal chem-mill cracking away from lap joint locations on 8 different airplanes with 20 inch tear strap spacing. These airplanes had between 37,000 and 45,000 total flight cycles at the time the cracks were discovered. It is believed that these horizontal chem-mill cracks in the crown skin at locations away from the lap joints occurred as a result of skin buckling during the normal flight spectrum combined with stress concentrations at the chem-mill step. As of the release date of this service bulletin there have not been any confirmed reports of cracks in the areas away from the lap joints that were not in the shear wrinkle areas, or areas next to filled in pockets as addressed in Service Bulletins 737-53A1301 or 737-53A1293. However, analysis and fleet data supporting service bulletin 737-53A1210 indicates that chem-mill cracking in these areas will also eventually occur as the airplanes accumulate more flight cycles. Several cases of vertical chem-mill cracks have been reported adjacent to butt joints in airplanes covered by SB 737-53A1210. No vertical cracks have been reported by airplanes covered by this service bulletin but due to structural similarities and identical loading, additional inspections have now been added. Analysis by Boeing indicates that these cracks are caused by fatigue due to high bending stresses at the edge of chem-milled steps. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 7 of 247 ### Page 8 ACTION On all affected airplanes, do Non Destructive Inspections (NDI) of the fuselage skin for cracks just above the S-4 and S-10 lap joints from STA 259.5 to STA 1016. Do NDI inspections for horizontal chem-mill cracks away from the lap joints in crown skin buckling areas over the entire crown skin. Do NDI inspections for vertical chem-mill cracks adjacent to the butt joints. Do NDI inspections for horizontal chem-mill cracks away from lap joints in general pocket-to-pocket crown skin areas that are not in a crown skin buckling area and that are not covered by 737-53A1301 R01 or 737-53A1293 R01 . If cracks are found just above lap joints, repair before any more flights as shown in this service bulletin. If cracks are found in areas other than the lap joints, contact Boeing for repair instructions and do the repair. If no cracks are found, repeat inspection in accordance with Paragraph 1.E., Compliance . EFFECTIVITY 737-300, -400, and -500 airplanes line numbers 2553 through 3132 in 4 groups. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes. COMPLIANCE Federal Aviation Administration (FAA) Airworthiness Directive 2005-13-27 is related to this service bulletin. The Federal Aviation Administration (FAA) will possibly release a new Airworthiness Directive related to this service bulletin. The new Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory. Refer to Paragraph 1.E., Compliance. The installation of a local (Time-Limited or Permanent) repair does not change the inspection requirements for the remaining non-repaired locations. 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 None BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 8 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 9 (OCR) BOEING SERVICE BULLETIN 737-53A1234 ALERT ALERT DO NDI INSPECTIONS OF THE FUSELAGE SKIN FOR VERTICAL CRACKS ALONG THE CHEM-MILL STEPS ADJACENT TO THE BUTT JOINTS. IF ANY CRACK IS FOUND, CONTACT BOEING FOR REPAIF NSTRUCTIONS AND INSTALL THE REPAIR 00000000000 DO NDI INSPECTIONS OF THE por/000/0000 900000000000 FUSELAGE SKIN FOR HORIZONTAL CRACKS ALONG THE CHEM-MILL STEPS ADJACENT TO STRINGERS. IF CRACKS ARE FOUND CONTACT BOEING FOR REPAIR INSTRUCTIONS AND INSTALL THE REPAIR DO NDI INSPECTIONS OF THE SKIN FOR HORIZONTAL CRACKS *ACCORDANCE TH THE SERVICE BALLEN OR ASK BENE FOR REPAIR DATA AND DO THE REPAIR. LEFT SIDE SHOWN RIGHT SIDE EQUIVALENT Original Issue: June 13, 2002 Revision 2: November 24, 2010 BOEING PROPRIETARY - 737-53A1234 Copyright © Unpublished Work - See page 1 for details. 9 of 247 ### Page 10 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 10 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT BLANK PAGE ### Page 11 Commercial Airplanes 737 Service Bulletin ALERT Number: 737-53A1234 Original Issue: June 13, 2002 Revision 2: November 24, 2010 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Cracks at Chem-milled Steps - Inspection and Repair THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OWNER. 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 airplanes, line numbers 2553 through 3132 excluding airplane variable numbers PS763-PS799, PS901-PS906 -1 737-300 airplanes, variable numbers PS763-PS799, PS901-PS906-2 737-400 airplanes, line numbers 2553 through 3132-3 737-500 airplanes, line numbers 2553 through 3132-4 Airplane Models: 737-300, 737-400, 737-500 GroupVariable Number 3PJ552 - PJ561 3PJ601 - PJ615 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 11 of 247 ### Page 12 GroupVariable Number 3PJ811 3PJ816 - PJ817 1PM543 - PM550 1PP518 - PP520 1PP876 - PP877 1PQ297 - PQ299 1PQ345 - PQ348 1PQ370 - PQ373 1PQ391 - PQ395 1PQ408 - PQ410 1PQ414 - PQ418 1PQ431 - PQ438 1PQ447 - PQ448 1PQ451 1PQ454 1PQ473 - PQ475 1PQ772 1PQ933 - PQ935 1PQ951 1PQ971 - PQ997 1PR001 - PR017 1PR021 - PR034 1PR041 - PR045 1PR061 - PR072 1PR077 - PR082 1PR091 - PR092 1PR096 1PR101 1PR121 - PR122 1PR131 - PR132 1PR141 - PR143 1PR161 - PR172 1PR181 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 12 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 13 GroupVariable Number 1PS617 - PS630 1PS704 - PS706 2PS763 - PS799 1PS811 1PS836 - PS837 1PS841 - PS846 1PS851 - PS852 1PS856 1PS861 - PS863 1PS866 - PS868 1PS871 - PS874 1PS896 - PS897 2PS901 - PS906 1PS907 - PS941 1PS956 - PS957 1PS961 - PS963 1PS971 - PS978 4PT012 - PT015 4PT029 - PT031 4PT064 4PT126 - PT138 4PT188 4PT307 - PT309 4PT513 - PT517 4PT585 - PT586 4PT643 - PT644 4PT656 4PT681 - PT685 4PT716 - PT717 4PT721 - PT725 4PT801 - PT834 4PT851 - PT854 4PT871 - PT886 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 13 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 14 GroupVariable Number 4PT901 - PT930 4PT971 - PT973 4PT981 - PT985 4PT996 4PU301 4PU311 - PU313 3PV204 - PV209 3PV226 - PV229 3PV284 - PV287 3PV296 3PV301 - PV302 3PV351 3PV356 - PV357 3PW086 - PW088 3PW168 - PW171 3PW245 - PW252 3PW262 - PW264 3PW271 - PW276 3PW282 - PW292 3PW401 - PW408 3PW411 - PW418 3PW421 - PW424 3PW431 - PW435 3PW441 - PW450 3PW521 - PW522 3PW524 - PW525 3PW527 - PW530 3PW547 - PW550 3PW621 - PW622 3PW635 - PW637 3PW831 3PW851 - PW856 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 14 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 15 2. Spares Affected None. B. Concurrent Requirements None C. Reason Accomplishment of the inspections and repairs shown in this service bulletin will ensure that fuselage skin cracks at specified locations are found and repaired. Continued operation with undetected skin cracks could cause unscheduled down time for repairs or possibly a decompression of the airplane. Two operators have reported 77 horizontal chem-mill cracks just above the Stringer (S)-4 and S-10 lap joints on airplanes with 20 inch tear strap spacing. The airplanes had between 30,000 and 46,000 flight cycles at the time the cracks were discovered. One operator has reported 9 cases of horizontal chem-mill cracking away from lap joint locations on 8 different airplanes with 20 inch tear strap spacing. These airplanes had between 37,000 and 45,000 total flight cycles at the time the cracks were discovered. It is believed that these horizontal chem-mill cracks in the crown skin at locations away from the lap joints occurred as a result of skin buckling during the normal flight spectrum combined with stress concentrations at the chem-mill step. As of the release date of this service bulletin there have not been any confirmed reports of cracks in the areas away from the lap joints that were not in the shear wrinkle areas, or areas next to filled in pockets as addressed in Service Bulletins 737-53A1301 or 737-53A1293. However, analysis and fleet data supporting service bulletin 737-53A1210 indicates that chem-mill cracking in these areas will also eventually occur as the airplanes accumulate more flight cycles. Several cases of vertical chem-mill cracks have been reported adjacent to butt joints in airplanes covered by SB 737-53A1210. No vertical cracks have been reported by airplanes covered by this service bulletin but due to structural similarities and identical loading, additional inspections have now been added. Analysis by Boeing indicates that these cracks are caused by fatigue due to high bending stresses at the edge of chem-milled steps. Revision 2 is sent to add additional inspections for horizontal chem-mill cracks away from the lap joints over the entire crown, new inspections for vertical chem-mill cracks adjacent to the butt joints and adding internal tear strap doublers at the tear strap adjacent to new and existing permanent repairs. Revision 1 is sent to make the repairs given in this Service Bulletin consistent with the 737 Structural Repair Manuals. For the time-limited and permanent repairs, the fastener pattern is changed to install a single fastener through the tear strap at the critical (first) row of the repair. Changes to this Service Bulletin include: — A reference is added to Federal Aviation Administration (FAA) Notice of Proposed Rule Making, FAA Docket Number FAA-2004-19533. — Summary - The number of flight cycles is changed to correct a typographical error. — Planning Information Section - Paragraph 1.C., Reason. Number of flight cycles changed to correct a typographical error. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 15 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 16 — Material Information Section - Paragraph 2.C.2, Parts and Materials Supplied by the Operator. Fastener quantities are changed. — Accomplishment Instructions - Paragraph 3.B., Part 1 Note C removed. — Figures 5, 6, 7 and 9 are changed to show a revised fastener patterns on the critical (first) row, common to the tear straps. D. Description On all affected airplanes, do Non Destructive Inspections (NDI) of the fuselage skin for cracks just above the S-4 and S-10 lap joints from STA 259.5 to STA 1016. Do NDI inspections for horizontal chem-mill cracks away from the lap joints in crown skin buckling areas over the entire crown skin. Do NDI inspections for vertical chem-mill cracks adjacent to the butt joints. Do NDI inspections for horizontal chem-mill cracks away from lap joints in general pocket-to-pocket crown skin areas that are not in a crown skin buckling area and that are not covered by 737-53A1301 R01 or 737-53A1293 R01 . If cracks are found just above lap joints, repair before any more flights as shown in this service bulletin, or contact Boeing for repair instructions and do the repair. If cracks are found in areas other then the lap joints, contact Boeing for repair instructions and do the repair. If no cracks are found, repeat inspections in accordance with Paragraph 1.E., Compliance . Service bulletins 737-53A1234 and 737-53A1210 have overlapping effectivities for airplanes 2553-2565. This is a result of a production change from 10 to 20 inch tear strap spacing and solid skins below stringer 10. Inspections in these two service bulletins do not overlap. The following summarizes the difference in skin configurations for the airplanes affected by these service bulletins: — Line number 292-2552 aircraft have 10 inch spaced tear straps and bonded skins above and below the window belts. The window belts have bonded skin. — Line number 2553-2565 aircraft have 20 inch spaced tear straps above the window belt, and 10 inch spaced tear straps below the window belt. The panels above and below the window belt have bonded skins. The window belt has solid skins. — Line number 2566-3132 aircraft have 20 inch spaced tear straps everywhere, with bonded skin panels above the window belt and solid skin panels at and below the window belt. The airplane effectivity is divided into 4 groups as follows: Group 1 - 737-300 airplanes line number 2553 through 3132 excluding airplane variable numbers PS763-PS799, PS901-PS906. Group 2 - 737-300 airplanes with variable numbers PS763-PS799, PS901-PS906. Group 3 - 737-400 airplanes line number 2553 through 3132. Group 4 - 737-500 airplanes line number 2553 through 3132. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 16 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 17 NOTE: 1. If cracks are found above lap joints before the thresholds listed in Paragraph 1.E., Compliance , measure and record the distance from the center of the upper fastener row in the lap joint to the upper edge of the upper bonded doubler. Measure at the midpoint between tear straps along the inner surface. Report measured distance to Boeing. Include body station, stringer location, airplane identifier and total accumulated flight cycles. Provide photos if possible. Provide the trimmed skin containing the fracture surface if possible. 2. Report all cracks in the general crown pocket to pocket areas, and above lap joints aft of station 908 to Boeing. Include crack length, body station, stringer location, airplane identifier and total accumulated flight cycles. Provide photos if possible. Provide the trimmed skin containing the fracture surface if possible. Ask Boeing for repair data and do the repair. 3. If horizontal or vertical cracks are found away from lap joints contact Boeing for damage removal instructions. 4. If the damaged area is more than the specified limits, write to Boeing for repair instructions and do the repair. Give the size and location of the damage. When possible, send sketches and photographs. If the damage includes corrosion, send data on the length, width, and largest depth of clean up. Send to: BOEING COMMERCIAL AIRPLANE GROUP ATTENTION: MANAGER, AIRLINE SUPPORT PLEASE SEND A REPORT OF YOUR INSPECTION PROGRAM. ALSO, SEND THE INSPECTION RESULTS WHEN EACH INSPECTION IS COMPLETE. Send your report to: BOEING COMMERCIAL AIRPLANE GROUP ATTENTION: MANAGER, AIRLINE SUPPORT Revision 1 - No more work is necessary at the locations repaired as shown in the initial release of this Service Bulletin. Revision 2 - More work is necessary at the locations inspected and repaired in accordance with the original issue and Revision 1 of this service bulletin. The work in this service bulletin is done in the maintenance zone(s) given below. Group 1-2: Affected Maintenance Zones ZoneModel 107, 108737-300 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 17 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 18 Group 3: Affected Maintenance Zones ZoneModel 107, 108737-400 Group 4: Affected Maintenance Zones ZoneModel 107, 108737-500 E. Compliance Federal Aviation Administration (FAA) Airworthiness Directive 2005-13-27 is related to this service bulletin. The Federal Aviation Administration (FAA) will possibly release a new Airworthiness Directive related to this service bulletin. The new Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory. The installation of a local (Time-Limited or Permanent) repair does not change the inspection requirements for the remaining non-repaired locations. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 18 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 19 Table 1: Fuselage Skin Inspections at Chem-mill Steps Common to Lap Joints Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles for an Option 1 inspec- tion. (a) The sooner of: 1. Within 500 flight cycles after the Revision 2 date of this ser- vice bulletin. Before the thresholds listed in Paragraph 1.E., Compli- ance Table 2 Inspect for cracking in the fuselage skin at the loca- tions listed in Paragraph 1.E., Compliance Table 2 in accordance with Ac- complishment Instruction 3.B.1.a. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. 2. At the next re- peat inspection interval previous- ly required by Revision 1 of this service bulletin. (a) (c) (d) Option 1: Do one of the following external Non Destructive Inspections (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OROption 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 1000 flight cycles for an Option 2 in- spection. (a) If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. Then the Option 2 inspec- tions that follow must be done with- in 1000 flight cycle repeat intervals. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 19 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 20 Table 1: Fuselage Skin Inspections at Chem-mill Steps Common to Lap Joints Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition --Before further flight Install a permanent repair in accordance with Ac- complishment Instruction 3.B.2. Any crack found in the fuselage skin (a) OR Install a time limited re- pair in accordance with Accomplishment Instruc- tion 3.B.4. (a) --Within 6000 flight cycles from the release of Revision 2 of this service bul- letin Install internal tear strap doublers in accordance with Accomplishment In- struction 3.B.3. (b) Permanent repairs installed in accordance with the Original Issue or Revision 1 of this service bulletin 3000 flight cycles until permanent re- pair is installed Within 500 flight cycles from the release of Revi- sion 2 of this ser- vice bulletin Within 3000 flight cycles af- ter the time limit- ed repair is in- stalled Do a detailed inspection for loose fasteners in ac- cordance with Accom- plishment Instruction 3.B.4. Time limited repair installed in accordance with the Original Issue, Revision 1 or Revision 2 of this service bulletin -6000 flight cycles from the time the time limited repair is installed Within 1000 flight cycles from the release of Revision 2 of this service bul- letin Make the repair perma- nent by replacing the blind fasteners in the time limited repair with solid rivets and install internal tear strap doublers in ac- cordance with Accom- plishment Instruction 3.B.4. Time limited repair installed in accordance with the Original Issue or Revision 1 of this service bulletin --Within 6000 flight cycles af- ter the time limit- ed repair is in- stalled Make the repair perma- nent by replacing the blind fasteners in the time limited repair with solid rivets and install internal tear strap doublers in ac- cordance with Accom- plishment Instruction 3.B.4. Time limited repair installed in accordance with Revi- sion 2 of this service bul- letin BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 20 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 21 Table 1: Fuselage Skin Inspections at Chem-mill Steps Common to Lap Joints Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition --Before further flight Replace loose fasteners in accordance with Ac- complishment Instruction 3.B.4. Loose fasteners found after the time limited repair was installed in accordance with the Original Issue, Revision 1 or Revision 2 of this ser- vice bulletin --Before further flight Ask Boeing for repair da- ta and do the repair. Crack found after time limit- ed or permanent repair is installed (a) Accomplishment of a repair in accordance with Accomplishment Instruction 3.B.2 Part 2 or 3.B.3 Part 3 or 3.B.4 Part 4 is a terminating action for repeat inspections of the skin at the chem-mill steps under the repair area only. (b) It is not necessary to install internal tear strap doublers if they have previously been installed in accordance with a repair plan that was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. (c) It is not necessary to inspect the chem-mill steps under an existing external repair installed in accordance with the Original Issue or Revision 1 of this service bulletin. (d) 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 Ultra Sonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 21 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 22 Table 2: Inspection Thresholds for Chem-mill Cracks above Lap Joints Threshold (Total Flight Cycles) StringerStationsAircraft 2500010L/R360-586Group 1 10L/R807-928 280004L259.5-294 4R259.5-360 4L/R360-540 4L/R616-685 4L/R727-908 10L/R727-807 420004L/R540-616 4L/R685-727 4L/R908-1016 10L/R665-727 2500010L/R360-540Group 2 10L/R807-928 280004L259.5-294 4R259.5-360 4L/R360-540 4L/R727-908 10L/R727E-807 420004L/R908-1016 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 22 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 23 Table 2: Inspection Thresholds for Chem-mill Cracks above Lap Joints Threshold (Total Flight Cycles) StringerStationsAircraft 2500010L/R360-540Group 3 10L/R807-928 280004L259.5-294 4R259.5-360 4L/R360-540 4L/R616-685 4L/R727-908 10L/R727-807 330004L/R540-616 4L/R685-727 10L/R665-727 420004L/R908-1016 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 23 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 24 Table 2: Inspection Thresholds for Chem-mill Cracks above Lap Joints Threshold (Total Flight Cycles) StringerStationsAircraft 2500010L/R360-586Group 4 10L/R807-928 280004L259.5-294 4R259.5-360 4L/R360-540 4L/R616-685 4L/R727-908 10L/R727-807 420004L/R540-616 4L/R685-727 4L/R908-1016 10L/R665-727 Table 3: Fuselage Skin Inspections at Chem-mill Steps Common to Shear Wrinkle Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 1000 flight cycles for an Option 1 in- spection. Within 1000 flight cycles af- ter the release of Revision 2 of this service bul- letin Before 33000 total flight cycles Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.b. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1500 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 1000 flight cycle repeat intervals. (a)(b) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OR BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 24 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 25 Table 3: Fuselage Skin Inspections at Chem-mill Steps Common to Shear Wrinkle Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 1500 flight cycles for an Option 2 in- spection. Option 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 1000 flight cycle repeat intervals. Then the Option 2 inspections that follow must be done within 1500 flight cycle repeat intervals. --Before further flight Contact Boeing for repair instructions and do the repair. Any crack found in the fuselage skin (a) It is not necessary to inspect the chem-mill steps under an existing external repair doubler provided all of the following apply: 1. The repair installed after the release of Revision 2 of this service bulletin. 2. The repair was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. 3. The repair extends a minimum of three rows of fasteners on each side of the chem-mill step in the circumferential direction. OR 1. The repair was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of 2 rows of 3/16 inch diameter fasteners on each side of the chem- mill step in the circumferential direction with 5-6D fastener spacing. 3. The repair is similar to 737-300/-400/-500 SRM 53-00-01 Figure 201 Repair 31 with regard to:  Fastener type, size, layout and pitch  Repair part thickness and material  Repair installation BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 25 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 26 Table 3: Fuselage Skin Inspections at Chem-mill Steps Common to Shear Wrinkle Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (b) 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 Ultra Sonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 26 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 27 Table 4: Fuselage Skin Inspections at Specified Vertical Chem-mill Step Locations Repeat Interval (Not to Ex- ceed) Compliance Time (Whichever Occurs Later) ActionCondition 1800 flight cycles or 1800 flight hours for an Option 1 inspection. Within 1800 flight cycles or 1800 flight hours after the release date of Revision 2 of this service bul- letin (whichever occurs first) Before 55000 total flight cycles or 55000 total flight hours (whichever oc- curs first) Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.c. using one of the following inspections op- tions: All Airplanes (whichever occurs first) If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 2400 flight cy- cles or 2400 flight hours, whichever occurs first, after the Option 2 inspection. Then the remaining Option 1 inspections that follow must be done within 1800 flight cycle or 1800 flight hour repeat intervals, whichever occurs first. (a) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OR Option 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 2400 flight cycles or 2400 flight hours for an Option 2 inspection. (whichever occurs first) If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 1800 flight cycle or 1800 flight hour repeat intervals, whichever occurs first. Then the Option 2 inspections that follow must be done within 2400 flight cycle or 2400 flight hour repeat intervals, whichever occurs first. -Before further flightContact Boeing for repair instructions and do the repair. Any crack found in the fuselage skin (a) 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 Ultra Sonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 27 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 28 Group 1-2, 4: Table 5 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles for an Option 1 inspec- tion. Within 500 flight cycles after the release of Revi- sion 2 of this service bulletin Before 49000 total flight cycles Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.d. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. (a)(b) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OROption 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 1000 flight cycles for an Option 2 in- spection. If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. Then the Option 2 inspec- tions that follow must be done with- in 1000 flight cycle repeat intervals. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 28 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 29 Group 1-2, 4: Table 5 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles for an Option 1 inspec- tion. Within 500 flight cycles after the release of Revi- sion 2 of this service bulletin Before 66000 total flight cycles Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.e. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. (a)(b) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OROption 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 1000 flight cycles for an Option 2 in- spection. If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. Then the Option 2 inspec- tions that follow must be done with- in 1000 flight cycle repeat intervals. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 29 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 30 Group 1-2, 4: Table 5 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition --Before further flight Contact Boeing for repair instructions and do the repair. Do not cut out the damage prior to receiving repair instructions from Boeing. It is likely that the cutout will be requested for further metallurgical analysis so the cutout will likely be larger than a typical repair. Any crack found in the fuselage skin (a) It is not necessary to inspect the chem-mill steps under an existing external repair doubler provided all of the following apply: 1. The repair installed after the release of Revision 2 of this service bulletin. 2. The repair was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. 3. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the circumferential direction. OR 1. The repair was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of 2 rows of 3/16 inch diameter fasteners on each side of the chem- mill step in the circumferential direction with 5-6D fastener spacing. 3. The repair is similar to 737-300/-400/-500 SRM 53-00-01 Figure 201 Repair 31 with regard to:  Fastener type, size, layout and pitch  Repair part thickness and material  Repair installation (b) 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 Ultra Sonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 30 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 31 Group 3: Table 6 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles for an Option 1 inspec- tion. Within 500 flight cycles after the release of Revi- sion 2 of this service bulletin Before 49000 total flight cycles Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.d. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. (a)(b) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OROption 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 1000 flight cycles for an Option 2 in- spection. If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. Then the Option 2 inspec- tions that follow must be done with- in 1000 flight cycle repeat intervals. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 31 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 32 Group 3: Table 6 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles for an Option 1 inspec- tion. Within 500 flight cycles after the release of Revi- sion 2 of this service bulletin Before 66000 total flight cycles Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.e. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. (a)(b) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OROption 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 1000 flight cycles for an Option 2 in- spection. If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. Then the Option 2 inspec- tions that follow must be done with- in 1000 flight cycle repeat intervals. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 32 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 33 Group 3: Table 6 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 500 flight cycles for an Option 1 inspec- tion. Within 500 flight cycles after the release of Revi- sion 2 of this service bulletin Before 81000 total flight cycles Inspect for cracking in the fuselage skin at the chem-mill steps at the specified locations in ac- cordance with Accom- plishment Instruction 3.B.1.f. using one of the following inspections op- tions: All Airplanes If the inspection procedure is being changed from Op- tion 2 to Option 1, the first Option 1 inspection must be done within 1000 flight cycles after the Option 2 inspec- tion. Then the re- maining Option 1 inspections that follow must be done within 500 flight cycle repeat intervals. (a)(b) Option 1: Do one of the following external Non Destructive Inspection (NDI): Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or C-Scan OR OROption 2: Do an external Non Destructive Inspec- tion: Ultrasonic Phased Array (UTPA) Inspection 1000 flight cycles for an Option 2 in- spection. If the inspection procedure is being changed from Op- tion 1 to Option 2, the first two Option 2 inspections must be done within 500 flight cycle repeat intervals. Then the Option 2 inspec- tions that follow must be done with- in 1000 flight cycle repeat intervals. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 33 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 34 Group 3: Table 6 Fuselage Skin Inspections at Chem-mill Steps in General Pocket-to-Pocket Areas: Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition --Before further flight Contact Boeing for repair instructions and do the repair. Do not cut out the damage prior to receiving repair instructions from Boeing. It is likely that the cutout will be requested for further metallurgical analysis so the cutout will likely be larger than a typical repair. Any crack found in the fuselage skin (a) It is not necessary to inspect the chem-mill steps under an existing external repair doubler provided all of the following apply: 1. The repair installed after the release of Revision 2 of this service bulletin. 2. The repair was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. 3. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the circumferential direction. OR 1. The repair was approved by the FAA or by a Boeing company authorized representative who was authorized by the FAA to make such findings. 2. The repair extends a minimum of 2 rows of 3/16 inch diameter fasteners on each side of the chem- mill step in the circumferential direction with 5-6D fastener spacing. 3. The repair is similar to 737-300/-400/-500 SRM 53-00-01 Figure 201 Repair 31 with regard to:  Fastener type, size, layout and pitch  Repair part thickness and material  Repair installation (b) 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 Ultra Sonic Phased Array (UTPA) NDI inspection options must be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 34 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 35 Table 7: Fuselage Skin Inspections at Chem-mill Step Repairs Common to Lap Joints - Part 26 Inspections Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 6000 flight cycles-Within 60000 flight cycles from the time the permanent repair is in- stalled Do 14 CFR Part 26 in- spections in accordance with Accomplishment In- struction 3.B.2. Permanent repairs installed in accordance with Revi- sion 2 of this service bul- letin 6000 flight cycles until internal tear strap doublers are installed -Within 60000 flight cycles from the time the permanent repair is in- stalled Do 14 CFR Part 26 in- spections in accordance with Accomplishment In- struction 3.B.3. Permanent repairs installed in accordance with the Original Issue or Revision 1 of this service bulletin 6000 flight cycles-Within 60000 flight cycles from the time the Revision 1 repair was in- stalled Do 14 CFR Part 26 in- spections in accordance with Accomplishment In- struction 3.B.3. Permanent repairs installed in accordance with Revi- sion 1 of this service bul- letin and then modified with internal tear strap doublers installed in accordance with Revision 2 of this service bulletin 6000 flight cycles-Within 60000 flight cycles from the time the time limited repair was in- stalled Do 14 CFR Part 26 in- spections in accordance with Accomplishment In- struction 3.B.4. Time limited repair modi- fied to a permanent repair in accordance with Revi- sion 2 of this service bul- letin 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 inspections and repairs defined in this service bulletin as an alternative method of compliance to the inspections and repairs required by paragraphs (g), (h) and (i) of FAA AD 2005-13-27. All provisions of FAA AD 2005-13-27 that are not specifically referenced in the above statement remain fully applicable and must be complied with. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 35 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 36 G. Manpower The table below shows an estimate of the man-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 man-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 examine the work — Time to cure the materials — Time to make the parts — Time to find the tools. Group 1: Elapsed HoursTask HoursNumber of PersonsTask Inspection 1.252.502Figure 2 1.753.502Figure 11 1.002.002Figure 16 2.605.202Figure 20 1.252.502Figure 24 5.5011.002Figure 28 0.751.502Figure 33 1.252.502Figure 40(a) 1.252.502Figure 41(a) 14.1028.20TOTAL FOR INSPECTION(b) Repair 17.0034.002Figure 5(c) (d) 10.5021.002Figure 6(c) (d) 16.0032.002Figure 9(c) (d) 17.0034.002Figure 34(c) (d) 10.5021.002Figure 35(c) (d) 10.5021.002Figure 36(c) (d) 8.0016.002Figure 37(c) (d) 10.0020.002Figure 38(c) (d) 5.0010.002Figure 39(c) (d) 104.50209.00TOTAL FOR REPAIR 118.10237.20TOTAL FOR EACH AIRPLANE BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 36 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 37 Group 1: Elapsed HoursTask HoursNumber of PersonsTask (a) Estimates are for one typical lap joint repair and not included in total inspection time shown. Multiply number of repairs to be inspected by estimate given and add to total shown to arrive at revised total required. (b) Estimates based upon use of C-Scan inspection method. For other types of inspection methods see table below. (c) Estimate given is for one typical repair as shown in the repair figures. (d) Estimate does not include time to manufacture parts. More time will be neces- sary to manufacture parts. Group 2: Elapsed HoursTask HoursNumber of PersonsTask Inspection 1.002.002Figure 10 1.503.002Figure 12 0.501.002Figure 17 2.505.002Figure 21 0.751.502Figure 25 5.0010.002Figure 29 0.751.502Figure 33 1.252.502Figure 40(a) 1.252.502Figure 41(a) 12.0024.00TOTAL FOR INSPECTION(b) Repair 17.0034.002Figure 5(c) (d) 10.5021.002Figure 6(c) (d) 16.0032.002Figure 9(c) (d) 17.0034.002Figure 34(c) (d) 10.5021.002Figure 35(c) (d) 10.5021.002Figure 36(c) (d) 8.0016.002Figure 37(c) (d) 10.0020.002Figure 38(c) (d) 5.0010.002Figure 39(c) (d) 104.50209.00TOTAL FOR REPAIR BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 37 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 38 Group 2: Elapsed HoursTask HoursNumber of PersonsTask 116.50233.00TOTAL FOR EACH AIRPLANE (a) Estimates are for one typical lap joint repair and not included in total inspection time shown. Multiply number of repairs to be inspected by estimate given and add to total shown to arrive at revised total required. (b) Estimates based upon use of C-Scan inspection method. For other types of inspection methods see table below. (c) Estimate given is for one typical repair as shown in the repair figures. (d) Estimate does not include time to manufacture parts. More time will be neces- sary to manufacture parts. Group 3: Elapsed HoursTask HoursNumber of PersonsTask Inspection 1.252.502Figure 3 2.505.002Figure 13 0.501.002Figure 15 0.501.002Figure 18 2.505.002Figure 22 1.252.502Figure 26 4.008.002Figure 30 3.006.002Figure 31 0.751.502Figure 33 1.252.502Figure 40(a) 1.252.502Figure 41(a) 16.2532.50TOTAL FOR INSPECTION(b) Repair 17.0034.002Figure 5(c) (d) 10.5021.002Figure 6(c) (d) 16.0032.002Figure 9(c) (d) 17.0034.002Figure 34(c) (d) 10.521.002Figure 35(c) (d) 10.521.002Figure 36(c) (d) 8.0016.002Figure 37(c) (d) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 38 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 39 Group 3: Elapsed HoursTask HoursNumber of PersonsTask 10.0020.002Figure 38(c) (d) 5.0010.002Figure 39(c) (d) 104.5209.00TOTAL FOR REPAIR 120.75241.50TOTAL FOR EACH AIRPLANE (a) Estimates are for one typical lap joint repair and not included in total inspection time shown. Multiply number of repairs to be inspected by estimate given and add to total shown to arrive at revised total required. (b) Estimates based upon use of C-Scan inspection method. For other types of inspection methods see table below. (c) Estimate given is for one typical repair as shown in the repair figures. (d) Estimate does not include time to manufacture parts. More time will be neces- sary to manufacture parts. Group 4: Elapsed HoursTask HoursNumber of PersonsTask Inspection 0.751.502Figure 4 1.252.502Figure 14 0.751.502Figure 19 1.753.502Figure 23 1.252.502Figure 27 5.0010.002Figure 32 0.751.502Figure 33 1.252.502Figure 40(a) 1.252.502Figure 41(a) 11.5023.00TOTAL FOR INSPECTION(b) Repair 17.0034.002Figure 5(c) (d) 10.5021.002Figure 6(c) (d) 16.0032.002Figure 9(c) (d) 17.0034.002Figure 34(c) (d) 10.5021.002Figure 35(c) (d) 10.5021.002Figure 36(c) (d) BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 39 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 40 Group 4: Elapsed HoursTask HoursNumber of PersonsTask 8.0016.002Figure 37(c) (d) 10.0020.002Figure 38(c) (d) 5.0010.002Figure 39(c) (d) 104.50209.00TOTAL FOR REPAIR 116.00232.00TOTAL FOR EACH AIRPLANE (a) Estimates are for one typical lap joint repair and not included in total inspection time shown. Multiply number of repairs to be inspected by estimate given and add to total shown to arrive at revised total required. (b) Estimates based upon use of C-Scan inspection method. For other types of inspection methods see table below. (c) Estimate given is for one typical repair as shown in the repair figures. (d) Estimate does not include time to manufacture parts. More time will be neces- sary to manufacture parts. Optional Inspection Methods - Manpower Adjustment Factor Multiply estimates given in inspection figures by a factor of 5Medium Frequency Eddy Current (MFEC) Multiply estimates given in inspection figures by a factor of 1.5Magneto Optical Imaging (MOI) Multiply estimates given in inspection figures by a factor of 12Ultrasonic Phased Array Inspection H. Weight and Balance Changes Change in Moment (Pound-Inches) Change in Weight (Pounds) Service Bulletin Repair Figure (a)(b)(c)+3.2Figure 5 - Permanent Skin Repair (a)(b)(c)+4.6Figure 6 - Time Limited Skin Repair (a)(b)(c)+3.0Figure 34 - Permanent Skin Repair (a)(b)(c)+4.6Figure 35 - Time Limited Skin Repair (a)(b)(c)+4.4Figure 36 - Time Limited Skin Repair (a)(b)(c)-1.4Figure 9 - Permanent Modification of the Time Lim- ited Skin Repair (a)(b)(c)-1.4Figure 37 - Permanent Modification of the Time Limited Skin Repair (a)(b)(c)+0.8Figure 38 - Internal Tear Strap Doubler Installation (a)(b)(c)+0.4Figure 39 - Internal Tear Strap Doubler Installation BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 40 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 41 Change in Moment (Pound-Inches) Change in Weight (Pounds) Service Bulletin Repair Figure (a) For Group and 2 (737-300's) measure the straight-line "X" distance in inches from the nose of the airplane to the center of the repair. Add 50 inches to get Balance Arm (BA). Multiply BA times the weight of the repair. The product is the desired "Change in Moment" value. Note that only the 1.4 value is negative which yields a negative product. (b) For Group 3 (737-400's) measure the straight-line "X" distance in inches from the nose of the airplane to the center of the repair. Subtract 22 inches to get Balance Arm (BA). Multiply BA times the weight of the repair. The product is the desired "Change in Moment" value. Note that only the 1.4 value is negative which yields a negative product. (c) For Group 4 (737-500's) measure the straight-line "X" distance in inches from the nose of the airplane to the center of the repair. Add 104 inches to get Balance Arm (BA). Multiply BA times the weight of the repair. The product is the desired "Change in Moment" value. Note that only the 1.4 value is negative which yields a negative product. Example: A 737-400 received two Figure 5 repairs, one Figure 6 and one Figure 9 repair at "X" distances measured as 400, 700, and 1,000 inches respectively. What is the Change in Moment? Answer: (2)(400-22)(3.2) = 2420, (700-22)(4.6) = 3119, and (1,000-22)(-1.4) = -1369 (negative). Summing: 2420 + 3119 - 1369 = 4170 Pound-Inches. I. Electrical Load Data Not changed J. References 1. Existing Data: a. 737-300/-400/-500 Maintenance Manual (AMM) Subject 25-21-39, 25-21-45, 25-21-46, 25-22-00, 25-23-61, 25-24-31 b. 737 Structural Repair Manual (SRM) 737-300, 737-400 and 737-500 Subject 53-00-01 c. 737 Nondestructive Test (NDT) Manual D6-37239 - Part 6, Subject 51-00-00 Figure 4, 51-00-00 Figure 16, 51-00-00 Figure 23, 53-30-00 Figure 3, 53-30-00 Figure 5, 53-30-09, 53-30-12, 53-30-16, 53-30-18, 53-30-19, 53-30-25, and Part 4, 53-30-05, 53-30-06, 53-30-07 d. Boeing Service Bulletins 737-53-1178 "Fuselage Frames - BSTA 663.75, Outboard Chord at Stringers 1, 2, 3, 4, and 5 Inspection and Preventive Modification" 737-53-1179 "Fuselage - Bonded Skin Doublers (Tear Straps) - Delamination Inspection and Repair" e. FAA Airworthiness Directive 2005-13-27 2. Data supplied with this Service Bulletin: None. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 41 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 42 3. Installation Drawings Used in the Preparation of this Service Bulletin: TitleDrawing Number SKIN INSTL - S-10L to S-10R, STA 360 - STA 54065C35765 SKIN ASSY - S-10L to S-10R, STA 360 - STA 54065C35785 SKIN INSTL - S-10 to S-14, STA 360 - STA 54065C35766 SKIN INSTL - S-10L to S-10R, STA 540 - STA 72765C35770 SKIN PANEL INSTL - S-10 to S-18A STA 540 - STA 72765-45771 SKIN INSTL - S-10L to S-10R, STA 727 - STA 90865C35772 PANEL INSTL-WINDOW, S-10 to S-14 STA 727 - STA 90865C35773 SKIN INSTL - S-4L to S-4R, STA 908 - STA 101665C45772 SKIN PANEL INSTL-AFT ENTRY DOOR - S-4L to S-25L, STA 908 - STA 101665C35777 SKIN INSTL-AFT ENTRY DOOR, S-4L to S-25L, STA 908 - STA 101665C27755 SKIN PANEL INSTL-AFT GALLEY DOOR - S-4R to S-25R, STA 908 - STA 101665C35778 SKIN INSTL-AFT GALLEY DOOR, S-4R to S-25R, STA 908 - STA 101665C27756 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 None BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 42 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 43 2. MATERIAL INFORMATION A. Material - Price and Availability None 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: NOTE: The parts that follow are used to accomplish a typical permanent skin repair in accordance with FIGURE 5 and FIGURE 34. Fastener size, type, and grip length may vary, depending on the specific repair. NotesNameQTYPart Number / Specification Doubler1A Filler1B Filler1C Internal Tear Strap Doubler42024-T3 clad sheet. 0.040 inch thick Internal Tear Strap Splice Doubler22024-T3 clad sheet. 0.040 inch thick Internal Tapered Filler22024-T3 clad sheet. 50:1 taper Internal Tapered Filler82024-T3 clad sheet. 50:1 taper (b)Rivet175BACR15BB6AD(-)C (b)Rivet185BACR15BB6D(-)C Chemical Conversion Coating, SOPM 20-43-03 1 ounceAlodine 1200s type II class A Primer, SOPM 20-41-022 ouncesBMS 10-11, Type l (a)Corrosion Inhibitor, SOPM 20-41-054 ouncesBMS 3-23 Type II (a)Sealant, SOPM 20-50-194 ouncesBMS 5-95 Type I or II, Class B 1/2, 2, or 4 (a) See the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data. (b) The actual fastener grip length will very depending on the location of the repair. Use the correct fas- tener size for the stack-up. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 43 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 44 NOTE: The parts that follow are used to accomplish a typical time-limited skin repair in accordance with FIGURE 6, FIGURE 35 - FIGURE 36. Fastener size, type, and grip length may vary, depending on the specific repair. NotesNameQTYPart Number / Specification Doubler1A Filler1B Filler1C (a)(c)Rivet190BACR15FR5E( )R (b)(c)Rivet110BACR15FR6E( )R Chemical Conversion Coating, SOPM 20-43-03 1 ounceAlodine 1200s type ll class A Primer, SOPM 20-41-022 ouncesBMS 10-11, Type l (d)Sealant, SOPM 20-50-194 ouncesBMS 5-95 Type I or II, Class B 1/2, 2, or 4 (a) NAS1738E5-() Optional. (b) NAS1738E6-() Optional. (c) The actual fastener grip length will very depending on the location of the repair. Use the correct fastener size for the stack-up. (d) See the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data. NOTE: The parts that follow are used to modify a typical time-limited skin repair into a permanent skin repair in accordance with FIGURE 9 and FIGURE 37. Fastener size, type, and grip length may vary, depending on the specific repair. NotesNameQTYPart Number / Specification Internal Tear Strap Doubler42024-T3 clad sheet. 0.040 inch thick Internal Tear Strap Splice Doubler22024-T3 clad sheet. 0.040 inch thick Internal Tapered Filler22024-T3 clad sheet. 50:1 taper Internal Tapered Filler82024-T3 clad sheet. 50:1 taper (a)Rivet170BACR15BB6AD(-)C (a)Rivet90BACR15BB6D(-)C (a)Rivet150BACR15BB7AD(-)C (b)Corrosion Inhibitor4 ouncesBMS 3-23, Type lI (a) The actual fastener grip length will very depending on the location of the repair. Use the correct fastener size for the stack-up. (b) See the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 44 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 45 3. Parts Modified and Reidentified: None. 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: June 13, 2002 737-53A1234Revision 2: November 24, 2010 45 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 46 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 46 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT BLANK PAGE ### Page 47 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. — Hole dimensions for standard solid rivets are given in 737 Structural Repair Manual, Chapter 51. — Torque limits to tighten nuts and bolts are given in 737 Structural Repair Manual, Chapter 51. 4. For approved fastener and process material substitutions, refer to 737 Structural Repair Manual, Chapter 51, Alternate fasteners are given in 737 Structural Repair Manual Chapter 51. 5. If the length of fasteners specified in this service bulletin do not meet the installation standards, fasteners of the same specification, or an approved substitute, one grip length longer or shorter may be used. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 47 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 48 6. 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 procedures may be required. 7. A General Visual Inspection is defined as: A visual examination of an interior or exterior area, installation or assembly to detect obvious damage, failure or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to ensure visual access to all surfaces in the inspection area. This level of inspection is made under normal available lighting conditions such as daylight, hangar lighting, flashlight or drop-light and may require removal or opening of access panels or doors. Stands, ladders or platforms may be required to gain proximity to the area being checked. 8. 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. B. WORK INSTRUCTIONS 1. PART 1 - Crown Area Skin Inspections NOTE: Some chem-milled pockets may have an irregular shape. The skin drawings in APPENDIX A can be used to help locate chem-mill pockets for crown area skin inspections. a. Inspections for horizontal chem-mill cracking above the S-4 and S-10 Lap Joints at specified locations: (1) Do NDI inspections in accordance with the applicable figures listed in Paragraph 3.B., Work Instructions, Table 1. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 48 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 49 Table 1: Figures for Chem-mill Cracks above Lap Joints FigureStringerStationsAircraft 210L/R360-586Group 1 210L/R807-928 114L259.5-294 114R259.5-360 114L/R360-540 114L/R616-685 114L/R727-908 1110L/R727-807 164L/R540-616 164L/R685-727 164L/R908-1016 1610L/R665-727 1010L/R360-540Group 2 1010L/R807-928 124L259.5-294 124R259.5-360 124L/R360-540 124L/R727-908 1210L/R727E-807 174L/R908-1016 310L/R360-540Group 3 310L/R807-928 134L259.5-294 134R259.5-360 134L/R360-540 134L/R616-685 134L/R727-908 1310L/R727-807 154L/R540-616 154L/R685-727 1510L/R665-727 184L/R908-1016 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 49 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 50 Table 1: Figures for Chem-mill Cracks above Lap Joints FigureStringerStationsAircraft 410L/R360-586Group 4 410L/R807-928 144L259.5-294 144R259.5-360 144L/R360-540 144L/R616-685 144L/R727-908 1410L/R727-807 194L/R540-616 194L/R685-727 194L/R908-1016 1910L/R665-727 b. Inspections for horizontal chem-mill cracking in shear wrinkle areas: (1) Group 1: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 20. (2) Group 2: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 21. (3) Group 3: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 22. (4) Group 4: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 23. c. Inspections for vertical chem-mill cracking at specified locations: (1) Group 1: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 24. (2) Group 2: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 25. (3) Group 3: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 50 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 51 with FIGURE 26. (4) Group 4: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 27. d. Inspections for horizontal chem-mill cracking in general pocket-to-pocket areas at specified locations between S-10L to S-10R and STA 360 to STA 1016 (excluding STA 500C to STA 540 and STA 727 to STA 727G for group 3 airplanes): (1) Group 1: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 28. (2) Group 2: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 29. (3) Group 3: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 30. (4) Group 4: Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 32. e. Inspections for horizontal chem-mill cracking in general pocket-to-pocket areas at specified locations from STA 259.5 to STA 360 between S-4L to S-4R: (1) Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 33. f. Group 3: Inspections for horizontal chem-mill cracking in general pocket-to-pocket areas at specified locations from STA 500C to STA 540 and STA 727 to 727G between S-10L to S-10R: (1) Do an external NDI of the fuselage skin at the chem-mill steps for cracks in accordance with FIGURE 31. g. If cracks are found just above a Stringer S-4 or S-10 lap joint, repair before further flight in accordance with PART 2 - Permanent Lap Repair or PART 4 - Time Limited Repair. If the repairs shown in PART 2 or PART 4 cannot be installed, ask Boeing for repair data and install the repair. h. Report all cracks not at a lap joint to Boeing. Report all cracks aft of station 908 that are adjacent to the lap joints to Boeing. Include crack length, body station, stringer location, airplane identifier and total accumulated flight cycles. Provide photos if possible. Provide the trimmed skin containing the fracture surface if possible. Ask Boeing for repair data and install the repair. i. If no cracks are found, put the airplane back to a serviceable condition. Do the inspections again in accordance with Paragraph 1.E., Compliance. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 51 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 52 NOTE: 1. The inspections shown in PART 1.a. are not necessary in areas previously repaired, provided the repair is a Boeing approved repair with a minimum of three rows of fasteners above the chem-milled step and three rows of fasteners below the lap joint. 2. Existing repairs with doublers that end on the lower row of the lap joint must be removed and repaired. Ask Boeing for repair data, include existing repair details, and do the repair. 3. The inspections shown in PART 1.c. are not necessary in areas previously repaired, provided the repair is a Boeing approved repair with a minimum of two rows of fasteners FWD and AFT of the the chem-milled step. 4. The inspections shown in PART 1 are not necessary in areas where: – The upper doubler is not fully chem-milled away (removed down to the bond line). – Internal reinforcing members are present (door cut-out bearstraps). – Inspections have been accomplished in accordance with 737-53A1301 R01, or 737-53A1293 R01. 2. PART 2 - Permanent Lap Repair a. The repair that follows is subject to the following limitations: (1) This repair is only applicable at lap joints within the ranges listed in Paragraph 3.B., Work Instructions, Table 2. Table 2: Lap Joint Repair Areas StringerStationsAircraft 4, 10380-520Group 1 4559-639 4685-706 4, 10727A-887 4, 10380-520Group 2 4727A-887 4, 10727E-887 4, 10380-500BGroup 3 4, 10500D-520 4559-639 4685-706 4, 10727A-727F 4, 10747-887 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 52 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 53 Table 2: Lap Joint Repair Areas StringerStationsAircraft 4, 10380-520Group 4 4559-639 4685-706 4, 10727A-887 Contact Boeing for lap joint repairs at all other locations. (2) For a 20-23 inch wide frame/stringer bay, this repair is limited to a crack with a maximum length of 12.5 inches, that is totally contained within the cutout shown in FIGURE 5 or FIGURE 34. For smaller frame/stringer bay widths, the maximum crack length will be smaller. (Example: for a 18 inch wide frame/stringer bay, the maximum crack length is 10.5 inches.) (3) This repair is limited in size to one frame/stringer bay, with the crack totally contained in that bay. (4) This repair cannot be installed in an area where it would be common to a skin butt joint. (5) This repair cannot be used in areas where existing lock bolts, Hi-loks or bolts would be common to the repair. (6) This repair cannot be used in door cutout bear strap locations. (7) Repairs cannot be installed in adjacent frame/stringer bays. (8) Installation of the permanent repair does not change the inspection requirements for the remaining non-repaired locations. b. Remove the following equipment from the passenger cabin as necessary for internal access to the area of the skin crack: 737-300/-400/-500 AMM SubjectEquipment 25-22-00Passenger Seats 25-21-46Sidewall Linings 25-21-39Sidewall Insulation 25-24-31Overhead Stowage Bins 25-23-61Passenger Service Units 25-21-45Ceiling Panels c. Inspect existing local structure in accordance with FIGURE 5 for Stringer 4 or FIGURE 34 for Stringer 10. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 53 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 54 d. Install a permanent skin repair in accordance with FIGURE 5 for Stringer 4 or FIGURE 34 for Stringer 10. If the repair limits in the above notes and in FIGURE 5 and FIGURE 34 cannot be maintained, ask Boeing for repair data and do the repair. NOTE: Group 2 airplanes do not require internal tear strap doublers below S-4 at STA 727A through STA 727E. e. Install the equipment in the passenger cabin that was removed for internal access. f. Put the airplane back to a serviceable condition. g. Do 14 CFR Part 26 inspections in accordance with FIGURE 40 at the times specified in Paragraph 1.E., Compliance, Table 7. 3. PART 3 - Inspection and Installation of Internal Tear Strap Doublers on Permanent Repairs Installed prior to Revision 2 of this service bulletin. NOTE: The fastener pattern at the tear strap is different on repairs installed in accordance with the Original Issue of the service bulletin. Contact Boeing for instructions on how to install internal tear straps doublers for these repairs and install the repair 1. 2. For existing permanent repairs common to tear straps between 3.88 to 4.30 inches wide, contact Boeing for repair instructions and do the repair. a. This repair is only applicable at lap joints within the ranges listed in Paragraph 3.B., Work Instructions, Table 2. b. Remove the following equipment from the passenger cabin as necessary for internal access to the area of the previously installed permanent repair: 737-300/-400/-500 AMM SubjectEquipment 25-22-00Passenger Seats 25-21-46Sidewall Linings 25-21-39Sidewall Insulation 25-24-31Overhead Stowage Bins 25-23-61Passenger Service Units 25-21-45Ceiling Panels c. Install the internal tear strap doublers on the existing permanent repairs in accordance with FIGURE 38 for Stringer 4 and FIGURE 39 for Stringer 10. d. Install the equipment in the passenger cabin that was removed for internal access. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 54 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 55 e. Put the airplane back to a serviceable condition. f. Do 14 CFR Part 26 inspections in accordance with FIGURE 41 at the times specified in Paragraph 1.E., Compliance, Table 7 if a permanent repair was installed in accordance with the Original Issue or Revision 1 of this service bulletin. g. Do 14 CFR Part 26 inspections in accordance with FIGURE 40 at the times specified in Paragraph 1.E., Compliance, Table 7 if a permanent repair was installed in accordance with Revision 1 of this service bulletin and then modified with the internal tear strap doublers in accordance with Revision 2 of this service bulletin. 4. PART 4 - Time Limited Repair CAUTION - USE CAUTION WHEN LOCATING BLIND FASTENERS RELATIVE TO HIDDEN INTERNAL STRUCTURE. a. The repair that follows is subject to these limitations: (1) This repair should only be used for cracks at the chem-milled step in the upper skins at the lap joints within the ranges listed in Paragraph 3.B., Work Instructions, Table 2. (2) For a 20-23 inch wide frame/stringer bay, this repair is limited to a crack with a maximum length of 12.5 inches, that is totally contained within the cutout shown in FIGURE 6, FIGURE 35 or FIGURE 36. For smaller frame/stringer bay widths, the maximum crack length will be smaller. (Example: for a 18 inch wide frame/stringer bay, the maximum crack length is 10.5 inches.) (3) This repair is limited in size to one frame/stringer bay, with the crack totally contained in that bay. (4) This repair cannot be used in areas where existing lock bolts, Hi-loks or bolts would be common to the repair. (5) This repair cannot be used in areas where existing fasteners are larger than 3/16 inch diameter. (6) This repair cannot be installed in an area where it would be common to a skin butt joint. (7) This repair cannot be used in door cutout bear strap locations. (8) Repairs cannot be installed in adjacent frame/stringer bays. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 55 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 56 (9) Installation of the time-limited repair does not change the inspection requirements for the remaining non-repaired locations. (10) This repair cannot be installed common to S-10 between STA 540 to STA 727. Ask Boeing for repair data and do the repair. (11) For tear straps between 3.88 and 4.30 inches wide, only new repairs are allowed common to the production tear straps in accordance with Revision 2 of this service bulletin. Contact Boeing for repair instructions if there is an existing repair common to this type of production tear strap that was accomplished prior to Revision 2 of this service bulletin and do the repair. b. For tear strap widths of 3.0 inches to 3.54 inches, inspect existing local structure at Stringer 4 in accordance with FIGURE 6 and for tear strap widths of 3.88 inches to 4.3 inches inspect existing local structure at Stringer 4 in accordance with FIGURE 35. For tear strap widths of 3.0 inches to 3.54 inches, inspect existing local structure at Stringer 10 in accordance with FIGURE 36. c. Install a time-limited skin repair for Stringer 4 in accordance with FIGURE 6 for tear strap widths of 3.0 inches to 3.54 inches and FIGURE 35 for tear strap widths of 3.88 inches to 4.3 inches. Install a time-limited skin repair for Stringer 10 in accordance with FIGURE 36 for tear strap widths of 3.0 inches to 3.54 inches. If the repair limits in the above note and in FIGURE 6, FIGURE 35 and FIGURE 36 cannot be maintained, ask Boeing for repair data and do the repair. d. Inspect for loose fasteners at the times specified in Paragraph 1.E., Compliance. e. Put the airplane back to a serviceable condition. f. At the times specified in Paragraph 1.E., Compliance, make the repair permanent as follows: (1) Remove the following equipment from the passenger cabin as necessary for internal access to the area of the skin crack: 737-300/-400/-500 AMM SubjectEquipment 25-22-00Passenger Seats 25-21-46Sidewall Linings 25-21-39Sidewall Insulation 25-24-31Overhead Stowage Bins 25-23-61Passenger Service Units 25-21-45Ceiling Panels (2) To make the time limited repair permanent if time limited repair was installed in accordance with Revision 1 or Revision 2 of this service bulletin: BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 56 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 57 NOTE: The fastener pattern at the tear strap is different on repairs installed in accordance with the Original Issue of the service bulletin. Contact Boeing for instructions on how to install internal tear straps doublers for these repairs and install the repair. (a) Do the skin inspections and install permanent fasteners and tear strap doublers in accordance with FIGURE 9 for Stringer 4 and FIGURE 37 for Stringer 10. (3) Install the equipment in the passenger cabin that was removed for internal access. g. Put the airplane back to a serviceable condition. h. Do 14 CFR Part 26 inspections in accordance with FIGURE 40 at the times specified in Paragraph 1.E., Compliance, Table 7 for a time limited repair that was made permanent in accordance with Revision 2 of this service bulletin. BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: June 13, 2002 737-53A1234Revision 2: November 24, 2010 57 of 247 BOEING SERVICE BULLETIN 737-53A1234 ALERTALERT ### Page 58 (OCR) BOEING SERVICE BULLETIN 737-53A1234 ALERT ALERT THIS FIGURE IS DELETED. IGURE 1: LOGIC DIAGRAM - SKIN INSPECTIONS IN THE CROWN ARE SHEET 1 OF Original Issue: June 13, 2002 Revision 2 November 24, 2010 737-53A1234 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 58 of 247 ### Page 59 (OCR) BOEING SERVICE BULLETIN 737-53A1234 ALERT ALERT This Figure applies only to: Group 1. S-10R c •00 STA 727 •0oc 000. 737-300 STA 586 00000 STA 540 000000000 0002000000 SEE A FOR TYPICAL INSPECTION AREA V71814 FIGURE 2: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION (SHEET 1 OF 3) Original Issue: June 13, 2002 Revision 2 November 24, 2010 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. ### Page 60 (OCR) BOEING SERVICE BULLETIN 737-53A1234 ALERT ALERT FRAME TYPICAL FRAME CRACK UPPER SKIN• UPPER DOUBLER A - - C/L STRINGER LOWER SKIN TYPICAL INSPECTION AREA NDI INSPECTION AREA UPPER BONDED UPPER DOUBLER SKIN CRACK STRINGER LOWER SKIN INBD A-A V72014 FIGURE 2: FUSELAGE - CROWN AREA SKIN LAP JOINT INSPECTION (SHEET 2 OF 3) Original Issue: June 13, 2002 Revision 2 November 24, 2010 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 60 of 247 The text continues at https://openairdocs.org/service-documents/boeing/737-53a1234/file/78a5bdc10246.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.