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Commercial Airplanes 737 Service Bulletin ALERT Number: 737-53A1346 Original Issue: March 27, 2020 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Fuselage Skin Chem-Mill Step Crack Inspection and Repair Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15 CFR 300-774). 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 © 2020 Boeing.
Unpublished Work. All Rights Reserved.
Treatment of this document and its content is governed by contract with Boeing. Rights to use this document are licensed on a per aircraft basis and such rights may not be transferable. For more information, contact The Boeing Company.
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, KC-46, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8, Poseidon and Boeing liveries 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.
Original Issue: March 27, 2020 737-53A1346 1 of 801
5.0
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 2 of 801 BOEING SERVICE BULLETIN 737-53A1346
ALERTALERT
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Table of Contents
Summary9
1. PLANNING INFORMATION15
A. Effectivity15
1. Airplanes15
2. Spares Affected26
B. Concurrent Requirements26
C. Reason26
D. Description27
E. Compliance30
F. Approval101
G. Manpower103
H. Weight and Balance Changes134
I. Electrical Load Data135
J. References135
1. Existing Data:135
2. Data Supplied with this Service Bulletin:135
3. Installation Drawings Used in the Preparation of this Service Bulletin:136
K. Publications Affected136
L. Interchangeability and Intermixability of Parts137
M. Software Accomplishment Summary137
2. MATERIAL INFORMATION139
A. Material - Price and Availability139
B. Industry Support Information139
C. Parts Necessary for Each Airplane139
1. Kits/Parts139
2. Parts and Materials Supplied by the Operator139
3. Parts Modified and Reidentified143
4. Parts Removed and Not Replaced143
D. Parts Necessary to Change Spares143
E. Special Tooling - Price and Availability143
F. Special Tooling Necessary to do this Service Bulletin143
3. ACCOMPLISHMENT INSTRUCTIONS145
A. GENERAL INFORMATION145
B. WORK INSTRUCTIONS147
FIGURE 1: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 1, 22]274
FIGURE 2: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 2, 13, 24]278
FIGURE 3: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 23]282
FIGURE 4: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 3, 9-10, 14-15, 25]286
FIGURE 5: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 4, 11, 16]290
FIGURE 6: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 5, 12, 17]294
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 3 of 801 BOEING SERVICE BULLETIN 737-53A1346
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FIGURE 7: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 18, 21]298
FIGURE 8: FUSELAGE - SKIN AND TEAR STRAP INSPECTIONS AT CHEM-MILL STEPS COMMON TO
LAP JOINTS [Group 19-20]302
FIGURE 9: FUSELAGE - WINDOW BELT INSPECTION FOR ANY HORIZONTAL CHEM-MILL STEP
CRACK [Group 3, 9-10, 14-15, 18, 21, 25]306
FIGURE 10: FUSELAGE - WINDOW BELT INSPECTION FOR ANY HORIZONTAL CHEM-MILL STEP
CRACK [Group 4, 11, 16]310
FIGURE 11: FUSELAGE - WINDOW BELT INSPECTION FOR ANY HORIZONTAL CHEM-MILL STEP
CRACK [Group 5, 12, 17, 19-20]315
FIGURE 12: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 1, 22]
.319
FIGURE 13: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 2, 13,
24]325
FIGURE 14: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 23]
.332
FIGURE 15: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 3, 5,
14, 25]338
FIGURE 16: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 9-10,
12, 15, 17]345
FIGURE 17: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 4]
.352
FIGURE 18: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 11,
16]359
FIGURE 19: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 19,
21]366
FIGURE 20: FUSELAGE - SKIN CHEM-MILLED POCKETS VERTICAL CRACK INSPECTION [Group 18,
20]373
FIGURE 21: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANEL INSPECTION FOR ANY CRACK
[Group 1, 22]380
FIGURE 22: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANEL INSPECTION FOR ANY CRACK
[Group 2, 13, 23-24]388
FIGURE 23: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANEL INSPECTION FOR ANY CRACK
[Group 3, 6, 9-10, 14-15, 18, 21]397
FIGURE 24: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANEL INSPECTION FOR ANY CRACK
[Group 25]405
FIGURE 25: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANEL INSPECTION FOR ANY CRACK
[Group 4, 7, 11, 16]412
FIGURE 26: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANEL INSPECTION FOR ANY CRACK
[Group 5, 8, 12, 17, 19-20]421
FIGURE 27: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION FOR ANY CRACK [Group 1, 22] . 428 FIGURE 28: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION FOR ANY CRACK [Group 2-3, 24-25]
.435
FIGURE 29: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION FOR ANY CRACK [Group 23] . 442 FIGURE 30: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION FOR ANY CRACK [Group 4-5, 13-14,
19, 21]449
FIGURE 31: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION FOR ANY CRACK [Group 9-12, 15-18,
20]456
FIGURE 32: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION FOR ANY CRACK [Group 6-8] . 460 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 4 of 801 BOEING SERVICE BULLETIN 737-53A1346
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FIGURE 33: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION AT KNOWN CRACK LOCATIONS
[Group 1, 3-5, 13-14, 19, 21-25]464
FIGURE 34: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION AT KNOWN CRACK LOCATIONS
[Group 2]467
FIGURE 35: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION AT KNOWN CRACK LOCATIONS
[Group 3, 14, 21, 25]471
FIGURE 36: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION AT KNOWN CRACK LOCATIONS
[Group 3, 9-10, 14-15, 18, 21, 25]473
FIGURE 37: FUSELAGE - SECTION 41 SKIN PANEL INSPECTION AT KNOWN CRACK LOCATIONS
[Group 5, 12, 17, 19-20]475
FIGURE 38: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 1, 22]477
FIGURE 39: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 2, 13, 24]486
FIGURE 40: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 23]495
FIGURE 41: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 3, 9-10, 14-15, 25]504
FIGURE 42: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 18, 21]514
FIGURE 43: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 4, 11, 16]523
FIGURE 44: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 5, 12, 17]534
FIGURE 45: FUSELAGE - SECTION 43 AND SECTION 46 CROWN SKIN INSPECTION FOR ANY CRACK
[Group 19-20]543
FIGURE 46: FUSELAGE - MODIFICATION CATEGORY C REPAIR TO A SRM REPAIR AT A LAP JOINT
LOCATION - LAP JOINT INSPECTION551
FIGURE 47: FUSELAGE - MODIFICATION CATEGORY C REPAIR TO A SERVICE BULLETIN REPAIR
AT A NON LAP JOINT - BONDED DOUBLER INSPECTION555
FIGURE 48: FUSELAGE - CATEGORY C SKIN REPAIR AT A LAP JOINT - EXTERNAL INSPECTION. 559 FIGURE 49: FUSELAGE - CATEGORY C SKIN REPAIR AT A LAP JOINT - FASTENER REMOVAL AND
SKIN TRIM562
FIGURE 50: FUSELAGE - CATEGORY C SKIN REPAIR AT A LAP JOINT - FABRICATION565
FIGURE 51: FUSELAGE - CATEGORY C REPAIR AT A LAP JOINT - INSTALLATION569
FIGURE 52: FUSELAGE - CATEGORY C SKIN REPAIR AT A NON LAP JOINT - INSPECTION . . . 573 FIGURE 53: FUSELAGE - CATEGORY C SKIN REPAIR AT A NON LAP JOINT - FASTENER REMOVAL
AND SKIN TRIM575
FIGURE 54: FUSELAGE - CATEGORY C SKIN REPAIR AT A NON LAP JOINT - FABRICATION . . 578 FIGURE 55: FUSELAGE - CATEGORY C SKIN REPAIR AT A NON LAP JOINT - INSTALLATION . 581 FIGURE 56: FUSELAGE - PREVENTIVE MODIFICATION FOR WINDOW BELT HORIZONTAL CHEM-MILL STEP CRACK - INSPECTION AND FASTENER REMOVAL [Group 3, 5, 9-10, 12, 14-15, 17-21,
25]585
FIGURE 57: FUSELAGE - PREVENTIVE MODIFICATION FOR WINDOW BELT HORIZONTAL CHEM-MILL
STEP CRACK - FABRICATION [Group 3, 5, 9-10, 12, 14-15, 17-21, 25]588
FIGURE 58: FUSELAGE - PREVENTIVE MODIFICATION FOR WINDOW BELT HORIZONTAL CHEM-MILL
STEP CRACK - INSTALLATION [Group 3, 5, 9-10, 12, 14-15, 17-21, 25]592
FIGURE 59: FUSELAGE - SKIN CHEM-MILL STEP CRACK AT STRINGER 12 REPAIR - INSPECTION AND FASTENER REMOVAL AND CUT-OUT [Group 3, 5, 9-10, 12, 14-15, 17-21, 25] . . 598 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 5 of 801 BOEING SERVICE BULLETIN 737-53A1346
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FIGURE 60: FUSELAGE - SKIN CHEM-MILL STEP CRACK AT STRINGER 12 REPAIR - FABRICATION
[Group 3, 5, 9-10, 12, 14-15, 17-21, 25]602
FIGURE 61: FUSELAGE - SKIN CHEM-MILL STEP CRACK AT STRINGER 12 REPAIR - INSTALLATION
[Group 3, 5, 9-10, 12, 14-15, 17-21, 25]607
FIGURE 62: FUSELAGE - POST-REPAIR LOW FREQUENCY EDDY CURRENT (LFEC) INSPECTION OF THE STRINGER 12 REPAIR FOR ANY CRACK [Group 3, 5, 9-10, 12, 14-15, 17-21, 25] . 614 FIGURE 63: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 2, 23]617
FIGURE 64: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 13, 24]624
FIGURE 65: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 1]633
FIGURE 66: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 22]640
FIGURE 67: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 3, 6, 9-10, 14-15, 18, 21]647
FIGURE 68: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 25]655
FIGURE 69: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 4, 7, 11, 16]662
FIGURE 70: FUSELAGE - SECTION 43 LOWER LOBE SKIN PANELS WFD INSPECTION FOR ANY CRACK
[Group 5, 8, 12, 17, 19-20]671
FIGURE 71: CATEGORY C/TIME-LIMITED REPAIR AT A NON LAP JOINT CONVERSION INSPECTION
.678
FIGURE 72: OPTION 1 TO MAKE CATEGORY C REPAIR A SERVICE BULLETIN REPAIR WITH A
DOUBLER, SOLID FASTENERS AND TEAR STRAP DOUBLERS680
FIGURE 73: OPTION 2 TO MAKE CATEGORY C REPAIR A SERVICE BULLETIN REPAIR WITH A LARGER
DOUBLER, SOLID FASTENERS AND TEAR STRAP DOUBLERS686
FIGURE 74: POST REPAIR LOW FREQUENCY EDDY CURRENT (LFEC) INSPECTION OF SERVICE
BULLETIN REPAIR, OPTION 1692
FIGURE 75: POST REPAIR LOW FREQUENCY EDDY CURRENT (LFEC) INSPECTION OF SERVICE
BULLETIN REPAIR, OPTION 2694
APPENDIX A: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 1: INSPECTION OF THE SKIN HORIZONTAL
CHEM-MILL STEPS AND THE TEAR STRAP TABS AT THE LAP JOINTS FOR ANY CRACK
[Group 1-5, 9-25, Configuration 1]696
APPENDIX B: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 2: INSPECTION OF THE SKIN HORIZONTAL
CHEM-MILL STEPS AND THE TEAR STRAP TABS AT THE LAP JOINTS FOR ANY CRACK
[Group 1-5, 9-25, Configuration 2]702
APPENDIX C: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 3: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS AT THE WINDOW BELT FOR ANY CRACK [Group 3, 5, 9-10, 12, 14-15,
17-21, 25, Configuration 1]708
APPENDIX D: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 4: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS AT THE WINDOW BELT FOR ANY CRACK [Group 3, 5, 9-10, 12, 14-15,
17-21, 25, Configuration 2]713
APPENDIX E: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 5: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS AT THE WINDOW BELT FOR ANY CRACK [Group 4, 11, 16, Configuration
1]718
APPENDIX F: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 6: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS AT THE WINDOW BELT FOR ANY CRACK [Group 4, 11, 16, Configuration
2]721
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 6 of 801 BOEING SERVICE BULLETIN 737-53A1346
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APPENDIX G: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 7: INSPECTION OF THE VERTICAL
CHEM-MILL STEPS FOR ANY CRACK [Group 1-2, 13, 22-24, Configuration 1]724
APPENDIX H: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 8: INSPECTION OF THE VERTICAL
CHEM-MILL STEPS FOR ANY CRACK [Group 1-2, 13, 22-24, Configuration 2]728
APPENDIX I: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 9: INSPECTION OF THE VERTICAL CHEM-MILL STEPS FOR ANY CRACK [Group 3-5, 9-12, 14-21, 25, Configuration 1] . 732 APPENDIX J: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 10: INSPECTION OF THE VERTICAL CHEM-MILL STEPS FOR ANY CRACK [Group 3-5, 9-12, 14-21, 25, Configuration 2] . 738 APPENDIX K: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 11: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 LOWER LOBE FOR ANY CRACK [Group 1-25,
Configuration 1]744
APPENDIX L: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 12: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 LOWER LOBE FOR ANY CRACK [Group 1-25,
Configuration 2]748
APPENDIX M: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 13: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 41 FOR ANY CRACK [Group 1-25, Configuration 1] . 752 APPENDIX N: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 14: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 41 FOR ANY CRACK [Group 1-25, Configuration 2] . 757 APPENDIX O: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 15: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 AND SECTION 46 CROWN SKIN FOR ANY CRACK
[Group 1-2, 13, 22-24, Configuration 1]762
APPENDIX P: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 16: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 AND SECTION 46 CROWN SKIN FOR ANY CRACK
[Group 1-2, 13, 22-24, Configuration 2]766
APPENDIX Q: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 17: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 AND SECTION 46 CROWN SKIN FOR ANY CRACK
[Group 3-5, 9-12, 14-21, 25, Configuration 1]771
APPENDIX R: LOGIC DIAGRAM FOR PARAGRAPH 1.E., TABLE 18: INSPECTION OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 AND SECTION 46 CROWN SKIN FOR ANY CRACK
[Group 3-5, 9-12, 14-21, 25, Configuration 2]777
APPENDIX S: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE TABLE 19: POST-REPAIR DETAILED
INSPECTION OF CATEGORY C REPAIR INSTALLED IN ACCORDANCE WITH THIS SERVICE
BULLETIN FOR ANY CRACK AND FOR ANY LOOSE, MISSING, OR DAMAGED FASTENERS
[Group 1-25, Configuration 2]783
APPENDIX T: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE TABLE 20: POST-REPAIR DETAILED
INSPECTION OF TIME-LIMITED REPAIR INSTALLED IN ACCORDANCE WITH SERVICE BULLETIN 737-53A1210 REVISION 3 FOR ANY CRACK [Group 1-25, Configuration 1] . 788 APPENDIX U: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE TABLE 21: POST-REPAIR LOW FREQUENCY EDDY CURRENT (LFEC) INSPECTION OF THE STRINGER 12 CHEM-MILL CRACK REPAIR FOR ANY CRACK [Group 3-5, 9-12, 14-21, 25, Configuration 1] . . . 793 APPENDIX V: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE TABLE 22: WIDESPREAD FATIGUE
DAMAGE (WFD) DETAILED AND NON-DESTRUCTIVE TEST (NDT) INSPECTIONS OF THE HORIZONTAL CHEM-MILL STEPS IN SECTION 43 LOWER LOBE S-19 TO S-26 FOR ANY
CRACK795
APPENDIX W: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE TABLE 23: POST-REPAIR LOW
FREQUENCY EDDY CURRENT (LFEC) INSPECTION OF SERVICE BULLETIN REPAIRS INSTALLED IN ACCORDANCE WITH PART 16: MODIFICATION CATEGORY C REPAIR TO
SERVICE BULLETIN REPAIR AT THE NON LAP JOINT LOCATION800
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 7 of 801 BOEING SERVICE BULLETIN 737-53A1346
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Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 8 of 801 BOEING SERVICE BULLETIN 737-53A1346
ALERTALERT
BLANK PAGE
Commercial Airplanes 737 Service Bulletin ALERT SummaryNumber: 737-53A1346Original Issue: March 27, 2020 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Fuselage Skin Chem-Mill Step Crack Inspection and Repair
THIS DOCUMENT IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS DOCUMENT TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE NEW OWNER.
CONCURRENT REQUIREMENTS None.
BACKGROUND This service bulletin gives instructions for inspection and repair for cracking along the chem-mill steps on the fuselage skin from STA 259.5 to STA 1016. This service bulletin will supersede Service Bulletin (SB) 737-53A1210 Revision 3 and will contain all requirements of SB 737-53A1210 Revision 3 with the exception of lower lobe chem-mill cracking between STA 727 and STA 1016. The lower lobe chem-mill cracking between STA 727 and STA 1016 is the subject of Service Bulletins 737-53-1065 (737-200/-200C), 737-53-1168 (737-300), 737-53-1187 (737-400) and 737-53-1315 (737-500). In addition, this service bulletin was created to expand the Non-Destructive Test (NDT) inspection areas of the skin to all horizontal and vertical chem-mill step locations with a history of cracking between STA 259.5 to STA 1016 and to include the requirements to prevent Widespread Fatigue Damage (WFD) in the fuselage skin due to cracking in the chem-mill steps. Accomplishment of this service bulletin will allow early detection of cracks at the step of the chem-mill pockets and prevent WFD by reducing the chance of multiple adjacent chem-mill step cracks for linking with each other. Continued operation of the airplane with undetected chem-mill steps cracks could result in an uncontrolled decompression of the airplane and loss of structural integrity of the airplane.
Boeing has received a large number of reports of horizontal and vertical chem-mill step cracks while accomplishing the inspections in accordance with Service Bulletin 737-53A1210. The service history table below provides further descriptions of operator findings. Cracks found at the step of the chem-mill pockets are caused by fatigue from hoop stress and higher than expected bending stresses across the chem-mill steps. Multiple site damage leading to simultaneous chem-mill step cracking in consecutive bays is the source for WFD. The fuselage skin panels with side-by-side chem-mill pockets have been identified to be structure that is susceptible to WFD.
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 9 of 801
Service History ReportTotal Flight Cycles Operators have reported horizontal cracks along the edges of the chem-milled pockets in the skin at S-12 in the bay forward of STA 520 and just above the S-4, S-10, and S-14 lap joints. Horizontal chem-mill line cracks have also been found in non-lap joint areas of the fuselage crown skin and at the tear strap attachments to the fuselage skin. The chem-mill line crack were up to 8 inches long, and multiple adjacent bays have been found cracked along the same stringer.
23,425 - 64,420 Operators have reported horizontal skin cracks along the edges of the chem-milled pockets in the skin below S-14 in Section 41. The cracks were up to 7.25 inches long.
22,786 - 80,113 Operators have reported circumferential cracks along the vertical chem-mill steps of the fuselage skin next to the STA 360, STA 727, and STA 908 butt joints from S-3R to S-7R. Cracks have been found in multiple adjacent bays and have varied in length from 0.75 inch to 4 inches.
45,100 - 67,400 Boeing Service Related Problems (SRP) 737-SRP-53-0503 and 737-SRP-53-0394 are related to this service bulletin.
Boeing Fleet Team Digest (FTD) 737 FTD 53-14004 is related to this service bulletin.
This table is provided to operators for planning purposes only. Refer to the applicable sections for more information.
ReferenceAffectedPlanning Data Paragraph 1.A.2., Spares AffectedNoSpares Affected Paragraph 1.E., Compliance and Paragraph
1.F., Approval YesAD Related Paragraph 1.H., Weight and Balance ChangesYesWeight and Balance Change Paragraph 1.I., Electrical Load DataNoElectrical Load Changed Paragraph 1.K., Publications AffectedYesPublications Affected Paragraph 1.K., Publications AffectedNoAirplane Flight Operations Affected (Flight Crew Operations Manual and/or FAA Approved Airplane Flight Manual) Paragraph 2.C.1., Kits/PartsNoKits/Parts Required Paragraph 2.C.2., Parts and Materials Supplied by the Operator YesOperator Supplied Parts/Material Paragraph 2.F., Special Tooling Necessary to do this Service Bulletin NoSpecial Tooling Required Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 10 of 801 BOEING SERVICE BULLETIN 737-53A1346
ALERTALERT
ACTION Group 1-5, 9-25:
1. Do the following inspections of the fuselage skin for any crack:
a. Do an external detailed and NDT inspection of the fuselage skin from S-10L to S-10R for any vertical crack along the chem-mill step lines just forward and aft of STA 360, STA 540, STA 727, and STA 908 for 737-200/200C/300/500 airplanes and STA 360, STA 500C, BS 540, STA 727, STA 727G and STA 908 for 737-400 airplanes and at known locations. Skin inspection figures given in the this service bulletin show specific areas to inspect for any crack along the chem-mill step line of the fuselage skin.
b. Do an external detailed or external detailed and NDT inspection for any crack in the fuselage skin from STA 259.5 to STA 360 along the horizontal chem-mill step line. Skin inspection figures given in the this service bulletin show specific areas to inspect for any crack along the chem-mill step line of the fuselage skin.
c. Do an external detailed or external detailed and NDT inspection for any crack in the fuselage skin from STA 360 to STA 1016 and S-10L to S-10R along the horizontal chem-mill step line. Skin inspection figures given in this service bulletin show specific areas to inspect for any crack along the chem-mill step line of the fuselage skin.
d. Do an external detailed or external detailed and NDT inspection of the Section 43 lower lobe skin for any crack from S-14 to S-26 left and right from STA 360 to STA 540 along the horizontal chem-mill step line. Skin inspection figures given in this service bulletin show specific areas to inspect for any crack along the chem-mill step line at Section 43 lower lobe.
e. Do an external detailed and NDT inspection of the window belt dummy bay locations along the horizontal chem-mill step lines of the fuselage skin from S-10 to S-14 left and right and STA 500D to STA 520 for 737-300 airplanes, STA 500E to STA 500F and STA 500G to STA 520 for 737-400 airplanes and STA 482B to STA 520 for 737-500 airplanes for any crack.
f. Do an external detailed and NDT inspection for any horizontal crack along the chem-mill step lines of the fuselage skin from STA 360 to STA 1016 at the lap joints S-4, S-10 and S-14 left and right.
Skin inspection figures given in the this service bulletin show specific areas to inspect for any crack along the chem-mill step line of the fuselage skin.
g. Do an external High Frequency Eddy Current (HFEC) inspection for any crack in the fuselage skin at the tear strap attachments from STA 360 to STA 1016 at the lap joints S-4, S-10 and S-14 left and right.
2. If any crack is found, do the repair in accordance with this service bulletin or contact The Boeing Company for repair instructions and do the repair.
3. If no crack is found, repeat the detailed and NDT inspections at the intervals given in Paragraph 1.E., Compliance.
Group 6-8:
1. Do the following inspections of the fuselage skin for any crack:
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 11 of 801 BOEING SERVICE BULLETIN 737-53A1346
ALERTALERT
a. Do an external detailed inspection for any crack in the fuselage skin from STA 259.5 to STA 360 along the horizontal chem-mill step line. Skin inspection figures given in the this service bulletin show specific areas to inspect for any crack along the chem-mill step line of the fuselage skin.
b. Do an external detailed or external detailed and NDT inspection of the Section 43 lower lobe skin for any crack from S-14 to S-26 left and right from STA 360 to STA 540 along the horizontal chem-mill step line. Skin inspection figures given in this service bulletin show specific areas to inspect for any crack along the chem-mill step line at Section 43 lower lobe.
2. If any crack is found, do the repair in accordance with this service bulletin or contact The Boeing Company for repair instructions and do the repair.
3. If no crack is found, repeat the detailed and NDT inspections at the intervals given in Paragraph 1.E., Compliance.
Group 26:
1. The Boeing Company endorses the new FAA rules related to Limit of Validity (LOV) and recommends immediate and permanent removal from service of any airplanes upon reaching the LOV, whether or not it is operated under FAA jurisdiction. As such, The Boeing Company no longer provides maintenance instructions for airplanes that have accumulated flight cycles beyond the LOV. Airplanes in Group 26 (line number 1-291) have accumulated flight cycles beyond the LOV of the maintenance program. 14 CFR 121.1115 and 129.115 prohibit operation of an airplane beyond its LOV.
EFFECTIVITY 737-100/-200/-200C/-300/-400/-500 Airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes.
COMPLIANCE Federal Aviation Administration (FAA) Airworthiness Directives AD 2009-07-11, AD 2017-20-12, AD 2017-20-14 and AD 2013-18-08 are related to this service bulletin.
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION Boeing warranty remedies are not available for the inspection and repair procedures given in this service bulletin.
MANPOWER Refer to Paragraph 1.G., Manpower.
MATERIAL INFORMATION Operator Supplied Parts/Materials.
Refer to Paragraph 2.A., Material - Price and Availability.
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details.
Original Issue: March 27, 2020 737-53A1346 12 of 801 BOEING SERVICE BULLETIN 737-53A1346