# Boeing Alert Service Bulletin 737-53A1177: Boeing - Service Bulletin

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### Page 1

Commercial 
Airplanes
737
Service Bulletin
Number: 737-53A1177
Original Issue: November 08, 1994
Revision 7: June 14, 2013
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Repair Methods For Cracks In Lower Skins At Lap Joints and
Window Corners
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 © 1994 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Unpublished Work.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: November 08, 1994
737-53A1177Revision 7: June 14, 2013
1 of 598
8.0

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Table of Contents
Revision Transmittal Sheet ............................................ 7
Summary ..................................................... 1 3
1. PLANNING INFORMATION ........................................ 1 7
A. Effectivity ............................................... 1 7
1. Airplanes ............................................ 1 7
2. Spares Affected ........................................ 3 8
B. Concurrent Requirements ...................................... 3 8
C. Reason ................................................ 3 8
D. Description .............................................. 4 3
E. Compliance .............................................. 4 8
F. Approval ............................................... 7 7
G. Manpower .............................................. 8 0
H. Weight and Balance Changes .................................... 8 4
I. Electrical Load Data ......................................... 8 4
J. References .............................................. 8 4
1. Existing Data: ......................................... 8 4
2. Data Supplied with this Service Bulletin: ........................... 8 5
3. Installation Drawings Used in the Preparation of this Service Bulletin: ........... 9 0
4. Process Data: ......................................... 9 1
K. Publications Affected ........................................ 9 1
L. Interchangeability and Intermixability of Parts ........................... 9 1
M. Software Accomplishment Summary ................................ 9 1
2. MATERIAL INFORMATION ........................................ 9 3
A. Material - Price and Availability ................................... 9 3
B. Industry Support Information .................................... 9 6
C. Parts Necessary for Each Airplane ................................. 9 7
1. Kits/Parts: ........................................... 9 7
2. Parts and Materials Supplied by the Operator: ....................... 1 3 2
3. Parts Modified and Reidentified: ............................... 1 3 7
4. Parts Removed and Not Replaced: ............................. 1 3 7
D. Parts Necessary to Change Spares ................................ 1 3 7
E. Special Tooling - Price and Availability .............................. 1 3 7
F. Special Tooling Necessary to do this Service Bulletin ...................... 1 3 8
3. ACCOMPLISHMENT INSTRUCTIONS ................................. 1 3 9
A. GENERAL INFORMATION .................................... 1 3 9
B. WORK INSTRUCTIONS ...................................... 1 4 1
FIGURE 1: AREA TO INSPECT IN ACCORDANCE WITH 737 NDT 53-30-00, FIGURE 5 [Group 2-17,
19-21, 23-27] ......................................... 2 1 9
FIGURE 2: THIS FIGURE IS DELETED AT REVISION 7 ........................ 2 2 0
FIGURE 3: THIS FIGURE IS DELETED AT REVISION 7 ........................ 2 2 1
FIGURE 4: THIS FIGURE IS DELETED AT REVISION 7 ........................ 2 2 2
FIGURE 5: THIS FIGURE IS DELETED AT REVISION 7 ........................ 2 2 3
FIGURE 6: THIS FIGURE IS DELETED AT REVISION 7 ........................ 2 2 4
FIGURE 7: INSPECT THE LAP JOINT - GROUP 1 AIRPLANES [Group 1] .............. 2 2 5
FIGURE 8: INSPECT THE LAP JOINT - EXTERNAL METHOD .................... 2 2 6
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FIGURE 9: INSPECT THE LAP JOINT AND LAP JOINT MODIFICATION (REPAIR) - INTERNAL
INSPECTION [Group 2-28] .................................. 2 2 9
FIGURE 10: S-4 LAP JOINT MODIFICATION (REPAIR) [Group 2-8] .................. 2 3 3
FIGURE 11: S-10 LAP JOINT MODIFICATION (REPAIR) [Group 2-8] ................. 2 6 3
FIGURE 12: S-14 LAP JOINT MODIFICATION (REPAIR) [Group 2-8] ................. 2 8 9
FIGURE 13: S-14 LEFT LAP JOINT MODIFICATION (REPAIR), ESCAPE SLIDE LIGHT CUTOUT AT
STATION 360 [Group 2-8] .................................. 3 3 1
FIGURE 14: LAP JOINT MODIFICATION (REPAIR) SPLICE [Group 2-8] ................ 3 3 9
FIGURE 15: S-10 LAP JOINT MODIFICATION (REPAIR) WITH INTEGRATED SRM WINDOW REPAIR
[Group 2-8] .......................................... 3 4 2
FIGURE 16: SPECIAL REPAIR INSTRUCTIONS, FOR SRM REPAIR AT S-4 [Group 2-17] ...... 3 4 9
FIGURE 17: SPECIAL REPAIR INSTRUCTIONS, FOR SRM REPAIR AT S-10 [Group 2-17] ..... 3 5 3
FIGURE 18: SPECIAL REPAIR INSTRUCTIONS, FOR SRM REPAIR AT S-14 [Group 2-17] ..... 3 5 7
FIGURE 19: SPECIAL REPAIR INSTRUCTIONS, FOR SRM REPAIR [Group 2-17] .......... 3 6 1
FIGURE 20: INSPECTION REQUIREMENTS OUTER ROW, EXISTING REPAIR [Group 2-28] .... 3 6 7
FIGURE 21: S-14 LAP JOINT MODIFICATION (REPAIR) WITH INTEGRATED SRM WINDOW REPAIR
[Group 2-8] .......................................... 3 6 8
FIGURE 22: INSPECT BS360 TO BS540, UPPER FORWARD AND LOWER AFT WINDOW CORNERS
[Group 2-28] .......................................... 3 7 5
FIGURE 23: INSPECT BS727 TO BS908, LOWER FORWARD AND UPPER AFT WINDOW CORNERS
[Group 2-28] .......................................... 3 8 0
FIGURE 24: REPAIR OF WINDOW LOWER CORNERS [Group 2-8] .................. 3 8 5
FIGURE 25: REPAIR OF WINDOW UPPER CORNERS [Group 2-8] .................. 4 0 4
FIGURE 26: REPAIR OF WINDOW CORNERS AT THE BUTT JOINT [Group 2-8] ........... 4 2 3
FIGURE 27: REPAIR OF WINDOW CORNERS AT ADJACENT WINDOWS [Group 2-8] ....... 4 3 9
FIGURE 28: WINDOW CORNER REPAIR SUBSEQUENT TO LAP JOINT MODIFICATION (REPAIR) [Group
2-8] ............................................... 4 6 8
FIGURE 29: INSPECT FORWARD OF BS540, LOWER FORWARD AND UPPER AFT WINDOW CORNERS
[Group 2-28] .......................................... 4 9 5
FIGURE 30: INSPECT AFT OF BS727, UPPER FORWARD AND LOWER AFT WINDOW CORNERS [Group
2-28] .............................................. 4 9 8
FIGURE 31: WINDOW FRAME EDGE MARGIN REQUIREMENTS [Group 2-28] ........... 5 0 1
FIGURE 32: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 2 AND
5 (737-200P) [Group 2, 5] .................................. 5 0 3
FIGURE 33: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 3 AND
4 (737-200P) [Group 3-4] ................................... 5 0 5
FIGURE 34: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 6 AND
8 (737-200C) [Group 6, 8] .................................. 5 0 7
FIGURE 35: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 7
(737-200C) [Group 7] ..................................... 5 0 9
FIGURE 36: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 9, 10
AND 11 (737-300) [Group 9-11] ............................... 5 1 1
FIGURE 37: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 12 AND
13 (737-300) [Group 12-13] .................................. 5 1 3
FIGURE 38: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 14
(737-300) [Group 14] ..................................... 5 1 5
FIGURE 39: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 15
(737-300) [Group 15] ..................................... 5 1 7
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FIGURE 40: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 16
(737-300) [Group 16] ..................................... 5 1 9
FIGURE 41: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 17
(737-300) [Group 17] ..................................... 5 2 1
FIGURE 42: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 18
(737-300) [Group 18] ..................................... 5 2 3
FIGURE 43: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 19 AND
20 (737-400) [Group 19-20] .................................. 5 2 5
FIGURE 44: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 21
(737-400) [Group 21] ..................................... 5 2 7
FIGURE 45: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 22
(737-400) [Group 22] ..................................... 5 2 9
FIGURE 46: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 23 AND
24 (737-500) [Group 23-24] .................................. 5 3 1
FIGURE 47: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 25 AND
26 (737-500) [Group 25-26] .................................. 5 3 3
FIGURE 48: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 27
(737-500) [Group 27] ..................................... 5 3 5
FIGURE 49: LAP JOINT MODIFICATION (REPAIR) ZONES (CROWN LAP JOINT AREA) - GROUP 28
(737-500) [Group 28] ..................................... 5 3 7
FIGURE 50: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 2 AND 3 (737-200P)
[Group 2-3] .......................................... 5 3 9
FIGURE 51: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 4 (737-200P) [Group
4 ]  ................................................ 5 4 1
FIGURE 52: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 5 (737-200P) [Group
5 ]  ................................................ 5 4 3
FIGURE 53: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 6 AND 7 (737-200C)
[Group 6-7] .......................................... 5 4 5
FIGURE 54: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 8 (737-200C) [Group
8 ]  ................................................ 5 4 7
FIGURE 55: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 9 (737-300) [Group
9 ]  ................................................ 5 4 9
FIGURE 56: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 10 AND 12 (737-300)
[Group 10, 12] ......................................... 5 5 1
FIGURE 57: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 11, 13, 14, 15, 16
AND 17 (737-300) [Group 11, 13-17] ............................ 5 5 3
FIGURE 58: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 18 (737-300) [Group
18] ............................................... 5 5 5
FIGURE 59: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 19 (737-400) [Group
19] ............................................... 5 5 7
FIGURE 60: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 20 AND 21 (737-400)
[Group 20-21] ......................................... 5 5 9
FIGURE 61: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 22 (737-400) [Group
22] ............................................... 5 6 1
FIGURE 62: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 23 AND 25 (737-500)
[Group 23, 25] ......................................... 5 6 3
FIGURE 63: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 24, 26 AND 27
(737-500) [Group 24, 26-27] ................................. 5 6 5
FIGURE 64: INSPECTION ZONES (OUTSIDE CROWN LAP JOINT AREA) - GROUP 28 (737-500) [Group
28] ............................................... 5 6 7
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FIGURE 65: LOCATE CRADLE AT CONTACT AREA BS 540 ...................... 5 6 9
FIGURE 66: LOCATE CRADLE AT CONTACT AREA BS 727 ...................... 5 7 1
FIGURE 67: LOCATE CRADLE AT CONTACT AREA BS 352 ...................... 5 7 3
FIGURE 68: LOCATE CRADLE AT CONTACT AREA BS 1016 ..................... 5 7 5
FIGURE 69: LOCATE CRADLE AT CONTACT AREA BS 787 ...................... 5 7 7
FIGURE 70: INSPECT S-4 BUTT JOINT SPLICE ............................. 5 7 9
FIGURE 71: INSPECT S-10 BUTT JOINT SPLICE ............................ 5 8 4
FIGURE 72: INSPECT S-9 TO S-10 BUTT JOINT SPLICE ........................ 5 8 9
Appendix A: DISCREPANT STRUCTURE REPORT ........................... 5 9 4
Appendix B: LOGIC DIAGRAM - MORE WORK REQUIRED IF FIGURES 22 AND 23 HAVE BEEN DONE
................................................. 5 9 6
APPENDIX C: FUEL BURN AND PERFORMANCE PENALTIES ..................... 5 9 7
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### Page 7

Commercial 
Airplanes
737
Service Bulletin
Revision Transmittal SheetNumber: 737-53A1177Original Issue: November 08, 1994
Revision 7: June 14, 2013
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Repair Methods For Cracks In Lower Skins At Lap Joints and
Window Corners
This revision includes all pages of the service bulletin.
COMPLIANCE INFORMATION RELATED TO THIS REVISION
More work is necessary on airplanes changed as shown in revision 5 or revision 6 of this service bulletin.
For Group 2 through 28 airplanes, except as noted below where operators incorporated the actions of Boeing
messages:
– Additional window corner inspections are necessary at nine additional fastener holes in the corners of the
passenger windows between BS 360 to BS 540, upper forward and lower aft, and between BS 727 and BS
908, lower forward and upper aft. Figures 22 and 23 identify the additional inspections. Refer to
Accomplishment Instructions Part 3.B.5 and Compliance 1.E.10. for work instructions and inspection times.
A flow chart is provided in Appendix B of this service bulletin, showing the additional work required for
airplanes that accomplished the Figure 22 and 23 actions of revisions 5 or 6. Following release of revision
6 of this bulletin, but prior to release of revision 7, Boeing sent messages to operators with instructions to
do inspections and preventive modification of these nine additional fastener holes. At locations where the
instructions of those messages have been incorporated with FAA, Boeing DER or Boeing AR approval, no
more work is necessary at these nine fastener locations.
– Additional window corner inspections are necessary at fastener holes in the corners of the passenger
windows between BS 360 to BS 540, lower forward and upper aft, and between BS 727 and BS 908, upper
forward and lower aft. Figures 29 and 30 identify the additional inspections. Refer to Accomplishment
Instructions Part 3.B.5 and Compliance 1.E.10. for work instructions and inspection times.
– Additional window corner inspections are necessary at fastener holes in the corners of the passenger
windows forward of BS 360 and aft of BS 908. Figures 29 and 30 identify the additional inspections. Refer
to Accomplishment Instructions Part 3.B.5 and Compliance 1.E.10. for work instructions and inspection
times.
– Post Repair inspections are necessary for the lap joint modification (repair) or window belt skin panel
replacement, refer to Compliance 1.E.7, window corner structure, refer to Compliance 1.E.11, and butt
joints common to the lap joint modification (repair) or window belt skin panel replacement, refer to Compliance
1.E.13.
For Group 2, 4-5, 7, Configuration 2 airplanes:
– Airplanes that have incorporated the SB 737-53-1077 modification or repair, post alteration and post repair
inspections are necessary for the S-20L lap joint, refer to Compliance 1.E.12.
Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2002-07-08, AD 2002-07-10 and AD
2002-07-11 are related to this service bulletin.
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### Page 8

No new airplanes have been added or removed from the effectivity of this service bulletin.
REASON FOR REVISION
This revision is sent to provide lap joint modification (repair) drawings for 737-400 and 737-500 airplanes. Recent
fleet data has shown that both stringer and window frames have cracked in locations outside of the area covered
by previous releases of this service bulletin. This results in the need to accomplish more extensive inspections
over a larger area. In addition window belt skin panel replacement drawings are provided for alternative lap joint
modification (repair) to the S-10L/R and S-14L/R lap joints on 737-300 and 737-500 airplanes, updated lap joint
modification (repair) figures for 737-200/-200C airplanes and post repair inspections for the lap joint modification
(repair), window corner structure, and butt joints common to the lap joint modification (repair).
These sections were changed:
1. Summary, Effectivity - airplane groups have been increased from 11 to 28. Background, Action and
Compliance sections have been revised.
2. Paragraph 1.A., Effectivity, Group Configuration table has been revised.
3. Paragraph 1.C., Reason, has been revised. The table below shows airplane group changes from
Revision 6.
Airplane Group/Effectivity - Revision 6Airplane Group
Group 6 airplanes1
Group 1 airplanes in the range P3683-P41462
Group 1 airplanes in the range P4147-P4399 with line
numbers 924 to 1426.
3
Group 1 airplanes in the range P4147-P4399 with line
numbers 1453 to1585.
4
Group 4 airplanes.5
Group 3 airplanes are in the range P8901-P8970.6
Group 3 airplanes that are in the range P8971-P9995.7
Group 5 airplanes.8
Group 7 airplanes less PP127-PP150 with line numbers
1001 to 1446.
9
Group 7 airplanes less PP127-PP150 with line numbers
1447 to 1920.
10
Group 7 airplanes less PP127-PP150 with line numbers
1924 to 1953.
11
Group 7 airplanes PP127-PP150 with line numbers
1521 to 1790.
12
Group 7 airplanes PP127-PP150 with line numbers
1942 to 1947.
13
Group 8 airplanes less PP151-PP160 and PS751-
PS756.
14
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Airplane Group/Effectivity - Revision 6Airplane Group
Group 8 airplanes PP151-PP160 and PS751-PS756.15
Group 9 airplanes less PS757-PS76216
Group 9 airplanes PS757-PS762.17
Group 2 airplanes PM543-PM547, PQ408 and PQ473.18
Group 10 airplanes P7801-P7975 and P8151-P8291
with line numbers 1487 to 1922.
19
Group 10 airplanes P7801-P7975 and P8151-P8291
with line numbers 1931 to 2496.
20
Group 10 airplanes PJ551, PV203, PW224-PW244,
PW324-PW327 and PW462-PW467.
21
Group 2 airplanes PJ552, PW245 and PW282-PW284.22
Group 11 airplanes less P7235-P7245 (Group 27) and
PU001-PU0025 (Group 25 and 26) with line numbers
1792 to1921.
23
Group 11 airplanes less P7235-P7245 (Group 20) and
PU001-PU0025 (Group 19) with line numbers 1923 to
2494.
24
Group 11 airplanes PU001-PU007.25
Group 11 airplanes PU008-PU015.26
Group 11 airplanes PT028, PT060-PT063, PT304-
PT306 and PT436-PT438.
27
Group 2 airplane PT064.28
4. Paragraph 1.D., Description, has been revised.
5. Paragraph 1.E., Compliance, has been revised.
6. Paragraph 1.F., Approval, reference to new Airworthiness Directives have been added.
7. Paragraph 1.G., Manpower, added tables for window belt replacement and revised group numbers.
8. Paragraph 1.H., Weight and Balance table has been deleted and a new paragraph added.
9. Paragraph 1.J., Data Supplied with this Service Bulletin, new drawing sheet references have been
added to table.
10. Paragraph 2.A., Material, Price and Availability, new kits have been added for -300/-400/-500 airplanes.
11. Paragraph 2.C., Parts Necessary for each Airplane, new kit numbers have been added for -300/-400/-500
airplanes.
12. Paragraph 3.A., Accomplishment Instructions - General Notes, airplane group numbers revised from
11 to 28.
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13. Paragraph 3.B., Accomplishment Instructions - Work Instructions, revise Part IV to reference Lap Joint
Modification (Repair) instructions for -300 airplanes only, revise Part V to reference Figures 22-30, add
Parts VI and VII to reference new Lap Joint Modification (Repair) instructions for -400/500 airplanes,
add Parts VIII and IX to reference new inspections of the BS 360, BS 540, BS 727 and BS 908 butt
splice structure in areas common to the S-4 and S-10 lap joint modification (repair) and common to
the S-9 to S-10 window belt replacement. Add Part X to reference post repair inspections of the butt
splice structure at BS 360, BS 540, BS 727 and BS 908.
14. Figures 2 to 6 deleted. New figures 32 thru 64 replace figures 2 thru 6 for lap joint inspection locations.
15. Figures 10 and 11, new repairs to show the lap joints at shear tie locations at S-4R and S-10R have
been added.
16. Figures 22 and 23, nine additional fastener hole locations at S-10 and S-14 have been added.
17. Figures 24 and 25, repairs at window corners prior to lap joint modification (repairs) at S-10 and S-14
have been added.
18. Figure 26, repairs to butt joints at S-10 and S-14 have been added.
19. Figure 27, new figure added to show upper and lower adjacent window corner repairs at S-10 and
S-14.
20. Figure 28, new figure added to show repairs subsequent to lap joint modifications at S-10 and S-14.
21. Figures 29 and 30, new figures added to show inspection of fastener holes at unmodified upper and
lower window frame locations at S-10 and S-14.
22. Figure 31, new figure added to show window frame edge margin requirements.
23. Figures 32 thru 64, new figures added to show lap joint modification (repair) locations for crown lap
joints and inspection locations for lap joints outside the crown area. These figures replace figures 2
thru 6.
24. Figures 65 thru 69, new figures added to show cradle contact areas for support of the fuselage in jig
position.
25. Figures 70, 71 and 72, new figures added to show inspection of the BS 360, BS 540, BS 727 and
BS908 butt splice structure in areas common to the S-4 and S-10 lap joint modification (repair) and
common to the S-9 to S-10 window belt skin panel replacement.
26. Appendix A added to include a discrepant structure report.
27. Appendix B added to include a logic diagram reference more work required if figures 22 and 23 have
been done.
28. Appendix C added to include fuel burn penalty analysis data.
Paragraph I.A., Effectivity, has no new changes in the airplane operators.
Vertical lines are put on the left edge of each page, except in Paragraph I.A., Effectivity, to show the location of
important changes. Pages with no vertical lines have no important changes.
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### Page 11

REVISION HISTORY
November 08, 1994Original Issue:
September 19, 1996Revision 1:
July 24, 1997Revision 2:
September 18, 1997Revision 3:
September 02, 1999Revision 4:
February 15, 2001Revision 5:
May 31, 2001Revision 6:
June 14, 2013Revision 7:
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BLANK PAGE

### Page 13

Commercial 
Airplanes
737
Service Bulletin
SummaryNumber: 737-53A1177Original Issue: November 08, 1994
Revision 7: June 14, 2013
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Repair Methods For Cracks In Lower Skins At Lap Joints and
Window Corners
CONCURRENT REQUIREMENTS
None.
BACKGROUND
This service bulletin describes inspection and repair methods for cracks in lower skins at lap joints and window
corners. If the cracks in the lower skins at lap joints and window corners remain undetected, those cracks could
grow large and cause a sudden decompression.
Before the initial release of this bulletin, the fuselage skin lap joints of six airplanes in the fleet were inspected.
One airplane with approximately 45,000 flight cycles had no cracks. Five airplanes with 52,000 to 77,000 flight
cycles and 51,000 to 64,000 flight hours had a total of 273 cracks detected.
The primary cracks were located in the lap joint lower fastener row in the lower skin at tear strap locations.
Secondary cracks were also found in the lap joint lower fastener row of the lower skin, between the tear straps.
Tear straps are located at frames and half way between frames. The longest crack found was in the skin at a
tear strap and was 0.52 inches long, but if linked to adjacent cracks would give a total crack length of 2.0 inches.
Because the primary cracks in the lower skin were hidden between the upper skin and the tear strap, an eddy
current inspection technique was used to find the cracks. The secondary cracks were also found with eddy
current inspection techniques.
Since the initial release of this bulletin additional cases of cracking have been reported. Fifteen operators have
reported a total of 3,028 cracks detected in the lap splices of 32 airplanes and four airplanes with cracks in the
corners of passenger windows. The airplanes had 44,000 to 82,000 flight cycles.
Also since the initial release of this bulletin, lap joint repairs have been classified into different categories which
may require future inspections.
After the release of Revision 1, additional service history and analysis of cut-out sections forwarded to Boeing
has resulted in an enhanced understanding of the nature of the cracking and the ability to accurately detect
cracks common to the lower skin. As a result of this fleet data, the Preventive Change is no longer an option for
use. Additional analysis has lead to the recommendation to accomplish the lap joint repair at a threshold of
50,000 flight cycles. See Section C, Reason for more information.
Boeing did a Fuel Burn penalty analysis on the changes given in this service bulletin. Refer to APPENDIX C for
the analysis.
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### Page 14

The Lap Joints and Window Corners have been determined to be structure that is susceptible to Widespread
Fatigue Damage (WFD).
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 AffectedYesAirplane Flight Operations Affected (Flight Crew
Operations Manual and/or FAA Approved Air-
plane Flight Manual)
Paragraph 2.C.1., Kits/PartsYesKits/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
ACTION (PRR 35005-253RS, PRR 35457-R, PRR 35005-299RS)
On Group 1 airplanes, at lap joints common to stringers 10 and 14, at the locations shown in Figure 7, accomplish
the inspections and lap joint modification (repair).
On Group 2 thru 28 airplanes, at lap joints common to stringers 4, 10, and 14 between specified Body Stations,
install the lap joint modification (repair). On Group 2 thru 28 airplanes, for all other areas, perform an external
eddy current inspection of the lap joints for cracking at the lower row of fasteners in the lower skin.
Do an eddy current inspection and accomplish a general visual inspection for corrosion and bulges in the lap
joint at the same time.
SRM repairs identified in this bulletin are to be replaced with an updated local repair or incorporated into the lap
joint cutout repair.
Boeing recommends do the repairs and accomplish the inspections at the times shown in paragraph 1.E.,
Compliance. To do the lap joint modification (repair), cut out both the upper and lower skins common to the lap
joint and install the repair parts. If any crack is found during eddy current inspection in the other areas, cut out
the skin and the tearstrap common to the lower row and install a repair. If corrosion is discovered that exceeds
the allowable damage limits in the SRM, the damage must be cut out and repaired as shown in the SRM or per
Boeing instructions.
See Section 1.D Description for more details of accomplishment and airplane groups. See Section 1.E Compliance
for more details about when and what to accomplish. See Figures 32 thru 64 for more information of which lap
joints are affected.
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### Page 15

EFFECTIVITY
737-200, -200C, -300, -400, -500 Airplanes with bonded skins. Refer to Paragraph 1.A.1., Airplanes, for the list
of affected airplanes.
COMPLIANCE
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service
bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin
mandatory.
Federal Aviation Administration (FAA) Airworthiness Directives AD 2002-07-08, AD 2002-07-10, AD 2002-07-11,
AD 2003-14-06, AD 2004-18-06, AD 2008-08-23, AD 2008-09-13, AD 2013-09-01, AD 88-22-11 R1, AD 89-09-03,
AD 89-22-04, AD 91-07-04, AD 91-08-12, AD 92-25-09, AD 98-11-04 R1 are related to this service bulletin.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION
Boeing warranty remedies are not available for the configuration changes, inspection and repair, procedures
given in this service bulletin.
MANPOWER
Refer to Paragraph 1.G., Manpower.
MATERIAL INFORMATION
Operator Supplied Parts. Boeing supplied kits. Refer to paragraph 2.A., Material Price and Availability.
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BLANK PAGE

### Page 17

Commercial 
Airplanes
737
Service Bulletin
Number: 737-53A1177
Original Issue: November 08, 1994
Revision 7: June 14, 2013
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Repair Methods For Cracks In Lower Skins At Lap Joints and
Window Corners
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
737-200/-200C Passenger and Cargo Airplanes. Line numbers 1 thru
291. Lap joint cut out repair and modification at S-10L/R and S-14L/R.
-1
737-200 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908 as defined in Figure 32. Inspection of the window corner
structure is required between BS259 to BS540 and BS727 to BS1016.
Inspection of non-crown lap joints is required at the areas defined by
Figure 50.
-2
No service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
1
Service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
2
737-200 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908 as defined in Figure 33. Stringer S-14L/R lap joint modification
(repair) aft of BS727 required only for BS827 to BS908. Inspection
of the window corner structure is required between BS259 to BS540
and BS727 to BS1016. Inspection of non-crown lap joints is required
at the areas defined by Figure 50.
-3
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DESCRIPTIONCONFIGURATIONGROUP
737-200 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908 as defined in Figure 33. Stringer S-14L/R lap joint modification
(repair) aft of BS727 required only for BS827 to BS908. Inspection
of the window corner structure is required between BS259 to BS540
and BS727 to BS1016. Inspection of non-crown lap joints is required
at the areas defined in Figure 51.
-4
No service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
1
Service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
2
737-200 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908 as defined in Figure 32. Inspection of the window corner
structure is required between BS259 to BS540 and BS727 to BS1016.
Inspection of non-crown lap joints is required at the areas defined in
Figure 52.
-5
No service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
1
Service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
2
737-200C Cargo Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 34. Stringers S-10L and S-14L do not
require the lap joint modification (repair) between BS360 to BS540.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. Inspection of non-crown lap joints
is required at the areas defined in Figure 53.
-6
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### Page 19

DESCRIPTIONCONFIGURATIONGROUP
737-200C Cargo Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 35. Stringers S-10L and S-14L do not
require the lap joint modification (repair) between BS360 to BS540.
Stringer S-14L/R lap joint modification (repair) aft of BS727, required
only for BS827 to BS908. Inspection of the window corner structure
is required between BS259 to BS540 and BS727 to BS1016.
Inspection of non-crown lap joints is required at the areas defined in
Figure 53.
-7
No service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
1
Service bulletin 737-53-1077 repair or preventive modification at
S-20L between BS 727 and BS 727A+9.90.
2
737-200C Cargo Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 34. Stringers S-10L and S-14L do not
require the lap joint modification (repair) between BS360 to BS540.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. Inspection of non-crown lap joints
is required at the areas defined in Figure 54.
-8
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 36. Stringer S-14L/R lap joint modification
(repair) aft of BS727 required only for BS827 to BS908. Inspection
of the window corner structure is required between BS259 to BS540
and BS727 to BS1016. The window belt skin panel replacement may
be installed as an option for the lap joint modification (repair) for
S-10L/R and S-14L/R and to terminate the inspections of the window
corner structure. Inspection of non-crown lap joints is required at the
areas defined in Figure 55.
-9
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 36. Stringer S-14L/R lap joint modification
(repair) aft of BS727 required only for BS827 to BS908. Inspection
of the window corner structure is required between BS259 to BS540
and BS727 to BS1016. The window belt skin panel replacement may
be installed as an option for the lap joint modification (repair) for
S-10L/R and S-14L/R and to terminate the inspections of the window
corner structure. Inspection of non-crown lap joints is required at the
areas defined in Figure 56.
-10
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### Page 20

DESCRIPTIONCONFIGURATIONGROUP
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 36. Stringer S-14L/R lap joint modification
(repair) aft of BS727 is required only between BS827 to BS908.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. The window belt skin panel
replacement may be installed as an option for the lap joint modification
(repair) for S-10L/R and S-14L/R and to terminate the inspections of
the window corner structure. Inspection of non-crown lap joints is
required at the areas defined in Figure 57.
-11
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 37. Stringer S-4 L/R lap joint modification
(repair) is not required between BS540 to BS727. Stringer S-14L/R
lap joint modification (repair) aft of BS727 required only for BS827
to BS908. Inspection of the window corner structure is required
between BS259 to BS540 and BS727 to BS1016. The window belt
skin panel replacement may be installed as an option for the lap joint
modification (repair) for S-10L/R and S-14L/R and to terminate the
inspections of the window corner structure. Inspection of non-crown
lap joints is required at the areas defined in Figure 56.
-12
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 37. Stringer S-4 L/R lap joint modification
(repair) is not required between BS540 to BS727. Stringer S-14L/R
lap joint modification (repair) aft of BS727 required only for BS827
to BS908. Inspection of the window corner structure is required
between BS259 to BS540 and BS727 to BS1016. The window belt
skin panel replacement may be installed as an option for the lap joint
modification (repair) for S-10L/R and S-14L/R and to terminate the
inspections of the window corner structure. Inspection of non-crown
lap joints is required at the areas defined in Figure 57.
-13
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 38. Stringer S-14L/R lap joint modification
(repair) aft of BS727 is required only for Stringer S-14L between
BS827 to BS908, and for Stringer S-14R between BS847 to BS908.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. The window belt skin panel
replacement may be installed as an option for the lap joint modification
(repair) for S-10L/R and S-14L/R and to terminate the inspections of
the window corner structure. Inspection of non-crown lap joints is
required at the areas defined in Figure 57.
-14
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### Page 21

DESCRIPTIONCONFIGURATIONGROUP
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 39. Stringer S-4L/R lap joint modification
(repair) is not required between BS540 to BS727. Stringer S-14L/R
lap joint modification (repair) aft of BS727 is required only for Stringer
S-14L between BS827 to BS908, and for Stringer S-14R between
BS847 to BS908. Inspection of the window corner structure is required
between BS259 to BS540 and BS727 to BS1016. The window belt
skin panel replacement may be installed as an option for the lap joint
modification (repair) for S-10L/R and S-14L/R and to terminate the
inspections of the window corner structure. Inspection of non-crown
lap joints is required at the areas defined in Figure 57.
-15
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 40. Stringer S-14L/R lap joint modification
(repair) between BS727 to BS908 is not required. Inspection of the
window corner structure is required between BS259 to BS540 and
BS727 to BS1016. The window belt skin panel replacement may be
installed from BS 360-540 as an option for the lap joint modification
(repair) for S-10L/R and S-14L/R and to terminate the inspections of
the window corner structure. The window belt skin panel replacement
may be installed from BS 727-908 as an option for the lap joint
modification (repair) for S-10L/R and to terminate the inspections of
the window corner structure. Inspection of non-crown lap joints is
required at the areas defined in Figure 57.
-16
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 41. Stringer S-4 L/R lap joint modification
(repair) is not required between BS540 to BS727. Stringer S-14L/R
lap joint modification (repair) between BS727 to BS908 is not required.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. The window belt skin panel
replacement may be installed from BS 360-540 as an option for the
lap joint modification (repair) for S-10L/R and S-14L/R and to
terminate the inspections of the window corner structure. The window
belt skin panel replacement may be installed from BS 727-908 as an
option for the lap joint modification (repair) for S-10L/R and to
terminate the inspections of the window corner structure. Inspection
of non-crown lap joints is required at the areas defined in Figure 57.
-17
737-300 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringer S-14L/R lap between BS360 and BS540 as
defined in Figure 42. Contact Boeing for lap joint (repair) at S-14L/R
between BS360 to BS540. Window corner inspections required
between BS259 to BS540 and BS727 to BS1016. The required
non-crown lap joint inspection areas are defined in Figure 58.
-18
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### Page 22

DESCRIPTIONCONFIGURATIONGROUP
737-400 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 43. Stringer S-14L/R lap joint modification
(repair) aft of BS727 is required only for Stringer S-14L between
BS827 to BS908, and for Stringer S-14R between BS847 to BS908.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. Inspection of non-crown lap joints
is required at the areas defined in Figure 59.
-19
737-400 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 43. Stringer S-14L/R lap joint modification
(repair) aft of BS727 is required only for Stringer S-14L between
BS827 to BS908, and for Stringer S-14R between BS847 to BS908.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. Inspection of non-crown lap joints
is required at the areas defined in Figure 60.
-20
737-400 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 44. Stringer S-14L/R lap joint modification
(repair) between BS727 to BS908 is not required. Inspection of the
window corner structure is required between BS259 to BS540 and
BS727 to BS1016. Inspection of non-crown lap joints is required at
the areas defined in Figure 60.
-21
737-400 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringer S-14L/R lap between BS360 and BS540 as
defined in Figure 45. Contact Boeing for lap joint (repair) at S-14L/R
between BS360 to BS540. Window corner inspections required
between BS259 to BS540 and BS727 to BS1016. The required
non-crown lap joint inspection areas are defined in Figure 61.
-22
737-500 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 46. Stringer S-14L/R lap joint modifcation
(repair) aft of BS727 is required only for Stringer S-14L between
BS827 to BS908, and for Stringer S-14R between BS847 to BS908.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. The window belt skin panel
replacement may be installed as an option for the lap joint modification
(repair) for S-10L/R and S-14L/R and to terminate the inspections of
the window corner structure. Inspection of non-crown lap joints is
required at the areas defined in Figure 62.
-23
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### Page 23

DESCRIPTIONCONFIGURATIONGROUP
737-500 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 46. Stringer S-14L/R lap joint modifcation
(repair) aft of BS727 is required only for Stringer S-14L between
BS827 to BS908, and for Stringer S-14R between BS847 to BS908.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. The window belt skin panel
replacement may be installed as an option for the lap joint modification
(repair) for S-10L/R and S-14L/R and to terminate the inspections of
the window corner structure. Inspection of non-crown lap joints is
required at the areas defined in Figure 63.
-24
737-500 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 47. Stringer S-4L/R lap joint modifcation
(repair) is not required between BS540 to BS727. Stringer S-14 L/R
lap joint modification (repair) aft of BS727 is required only for Stringer
S-14L between BS827 to BS908, and for Stringer S-14R between
BS847 to BS908. Inspection of the window corner structure is required
between BS259 to BS540 and BS727 to BS1016. The window belt
skin panel replacement may be installed as an option for the lap joint
modification (repair) for S-10L/R and S-14L/R and to terminate the
inspections of the window corner structure. Inspection of non-crown
lap joints is required at the areas defined in Figure 62.
-25
737-500 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 47. Stringer S-4 L/R lap joint modification
(repair) is not required between BS540 to BS727. Stringer S-14L/R
lap joint modifcation (repair) is required only for Stringer S-14L
between BS827 to BS908, and for Stringer S-14R between BS847
to BS908. Inspection of the window corner structure is required
between BS259 to BS540 and BS727 to BS1016. The window belt
skin panel replacement may be installed as an option for the lap joint
modification (repair) for S-10L/R and S-14L/R and to terminate the
inspections of the window corner structure. Inspection of non-crown
lap joints is required at the areas defined in Figure 63.
-26
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### Page 24

DESCRIPTIONCONFIGURATIONGROUP
737-500 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringers S-4, S-10 and S-14 laps between BS360 and
BS908, as defined in Figure 48. Stringer S-14 L/R lap joint
modification (repair) between BS727 to BS908 is not required.
Inspection of the window corner structure is required between BS259
to BS540 and BS727 to BS1016. The window belt skin panel
replacement may be installed from BS 360-540 as an option for the
lap joint modification (repair) for S-10L/R and S-14L/R and to
terminate the inspections of the window corner structure. The window
belt skin panel replacement may be installed from BS 727-908 as an
option for the lap joint modification (repair) for S-10L/R and to
terminate the inspections of the window corner structure. Inspection
of non-crown lap joints is required at the areas defined in Figure 63.
-27
737-500 Passenger Airplanes. Crown lap joint modification (repair)
required at Stringer S-14L/R lap between BS360 and BS540 as
defined in Figure 49. Contact Boeing for lap joint (repair) at S-14L/R
between BS360 to BS540. Window corner inspections required
between BS259 to BS540 and BS727 to BS1016. The required
non-crown lap joint inspection areas are defined in Figure 64.
-28
Airplane Models:
737-200, 737-200C, 737-300, 737-400, 737-500
GroupVariable Number
1PG001 - PG075
1PG199
1PG201 - PG230
1PG251 - PG255
1PG271 - PG279
1PG301 - PG314
1PG331 - PG332
1PG351 - PG356
1PG375
1PG401 - PG403
1PG431 - PG442
1PG471 - PG475
1PG501 - PG505
1PG571 - PG583
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### Page 25

GroupVariable Number
5PG584 - PG586
1PG621 - PG630
1PG651 - PG652
1PG701 - PG705
5PH001
5PH011 - PH013
5PH021 - PH024
1PH701 - PH715
1PH731 - PH732
1PH741 - PH742
5PH743
1PJ001 - PJ002
5PJ003
2PJ004 - PJ009
1PJ031 - PJ032
1PJ071 - PJ072
1PJ101 - PJ104
5PJ105 - PJ109
2PJ110 - PJ119
5PJ201 - PJ219
20PJ301 - PJ302
21PJ551
22PJ552
5PK026 - PK028
2PK029
5PK041 - PK048
2PK049 - PK053
5PK061 - PK067
2PK068 - PK070
5PK081
2PK082
5PK091
2PK092 - PK099
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GroupVariable Number
5PK101 - PK103
5PK111 - PK120
5PK141 - PK146
2PK201 - PK204
2PK211 - PK215
3PK216 - PK220
2PK221 - PK223
2PK231 - PK241
2PK251 - PK258
2PK271 - PK274
2PK281 - PK289
2PK291
2PK301 - PK318
2PK341
2PK351 - PK361
2PK391
2PK431 - PK433
2PK451 - PK452
2PK461 - PK469
2PK495
2PK501 - PK504
2PK511 - PK514
3PK515
3PK519
2PK521 - PK525
3PK526 - PK527
4PK528
2PK541 - PK564
3PK565
2PK581
2PK591 - PK599
2PK601 - PK617
2PK621 - PK637
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GroupVariable Number
2PK641 - PK642
2PK661 - PK664
3PK665 - PK666
2PK671 - PK680
3PK681
2PK691 - PK697
2PK711 - PK716
2PK731 - PK749
3PK750 - PK765
2PK771 - PK779
2PK801 - PK802
3PK803 - PK804
2PK819 - PK826
3PK827
2PK830
2PK861 - PK863
2PK871 - PK874
2PK881 - PK884
2PK901 - PK932
3PK933 - PK938
2PK971 - PK974
5PL001
2PL002 - PL026
3PL027 - PL028
2PL061
2PL081
2PL101 - PL113
2PL151
2PL171 - PL172
2PL201 - PL203
2PL221
2PL401 - PL415
3PL416 - PL417
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GroupVariable Number
2PL421
2PL441
2PL451 - PL454
3PL455 - PL456
2PL471
2PL491
2PL501 - PL506
2PL551 - PL562
2PL581
2PL601
3PL602 - PL603
2PL611
3PL621 - PL625
4PL626
2PL631 - PL632
1PL711 - PL712
1PL716
5PL717 - PL721
2PL722 - PL725
5PL726 - PL730
2PL731 - PL735
5PL736 - PL743
2PL744 - PL745
3PL746
4PL747
5PL756
5PL758
5PL761 - PL766
2PL767 - PL770
5PL781 - PL782
2PL783 - PL787
3PL788
5PL793
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GroupVariable Number
1PL801 - PL803
2PM001 - PM006
3PM016 - PM017
2PM021 - PM023
2PM051 - PM056
3PM057 - PM066
2PM101 - PM110
3PM111 - PM119
2PM141 - PM142
3PM171
3PM181
3PM251 - PM255
3PM281 - PM283
10PM381 - PM392
11PM393 - PM395
14PM396 - PM399
14PM401 - PM417
14PM541
16PM542
18PM543 - PM547
20PM551 - PM564
2PN001 - PN002
2PN021
3PN022 - PN043
3PN081 - PN086
3PN101 - PN117
3PN131 - PN163
3PN401 - PN420
3PN431 - PN433
3PN451 - PN456
3PN471 - PN472
4PN473 - PN474
3PN481
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GroupVariable Number
3PN491 - PN492
4PN493
3PN501
4PN502
4PN511 - PN512
4PN521
9PP001 - PP031
10PP032 - PP054
9PP101 - PP126
12PP127 - PP148
13PP149 - PP150
15PP151 - PP160
9PP161 - PP168
10PP169
9PP181 - PP184
10PP185 - PP199
9PP201 - PP204
10PP205
9PP221
9PP231 - PP243
9PP281 - PP286
9PP301 - PP305
9PP351 - PP352
10PP353
9PP376 - PP384
10PP391 - PP393
9PP401 - PP424
10PP425 - PP440
9PP471 - PP475
9PP501 - PP504
10PP505 - PP510
14PP511 - PP517
9PP521 - PP522
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GroupVariable Number
9PP631 - PP634
9PP651 - PP652
9PP671 - PP699
9PP701 - PP720
10PP721 - PP733
9PP771 - PP777
10PP778 - PP779
9PP801 - PP804
10PP805 - PP808
9PP821 - PP827
9PP831 - PP836
10PP837 - PP845
9PP846 - PP848
9PP851
10PP852
9PP861 - PP870
10PP871 - PP873
14PP874 - PP875
9PP891 - PP899
9PP901 - PP905
10PP906 - PP924
11PP925
14PP926 - PP930
9PP931 - PP934
10PP935 - PP936
9PP946 - PP948
10PP951 - PP952
9PP961 - PP965
10PP966 - PP967
9PP981 - PP982
10PP983 - PP987
11PP988
14PP989 - PP990
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GroupVariable Number
9PP991
10PP993
9PQ001 - PQ012
10PQ013 - PQ016
9PQ026 - PQ037
10PQ038 - PQ041
9PQ051 - PQ061
10PQ062 - PQ073
14PQ074 - PQ085
9PQ086
10PQ087 - PQ092
9PQ101 - PQ110
10PQ111 - PQ198
11PQ199
11PQ201 - PQ202
10PQ221 - PQ229
14PQ230
10PQ231 - PQ236
14PQ237
10PQ241 - PQ243
10PQ251 - PQ255
11PQ256 - PQ257
14PQ258 - PQ267
10PQ281 - PQ286
11PQ287
14PQ288 - PQ296
10PQ301 - PQ305
14PQ306 - PQ307
10PQ331 - PQ332
14PQ341 - PQ344
14PQ361 - PQ369
14PQ401 - PQ406
16PQ407
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GroupVariable Number
18PQ408
14PQ411 - PQ413
14PQ421
16PQ471 - PQ472
18PQ473
16PQ479 - PQ480
14PQ481
14PQ486
16PQ487
14PQ491 - PQ493
14PQ771
14PQ791 - PQ793
14PQ801 - PQ803
16PQ804 - PQ805
16PQ931 - PQ932
14PS601 - PS616
14PS631
14PS636 - PS638
10PS641 - PS642
14PS643 - PS644
14PS651 - PS657
10PS666 - PS668
14PS669
14PS691 - PS692
14PS701 - PS703
15PS751 - PS756
17PS757 - PS762
24PT001 - PT011
23PT021 - PT023
24PT024 - PT027
27PT028
24PT041 - PT059
27PT060 - PT063
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GroupVariable Number
28PT064
23PT101
24PT102 - PT105
23PT121 - PT123
24PT124 - PT125
23PT146
24PT147 - PT148
24PT161 - PT170
23PT181 - PT182
24PT183 - PT187
23PT211 - PT214
24PT215 - PT220
23PT295
24PT301 - PT303
27PT304 - PT306
24PT331 - PT360
24PT381 - PT399
24PT401 - PT435
27PT436 - PT438
24PT501 - PT512
24PT561 - PT565
24PT581 - PT584
24PT611 - PT621
24PT641 - PT642
24PT651 - PT655
24PT671 - PT672
24PT701 - PT703
25PU001 - PU007
26PU008 - PU025
19PV001 - PV040
20PV041 - PV055
20PV201 - PV202
21PV203
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GroupVariable Number
20PV231 - PV237
20PV271 - PV272
20PV281 - PV282
21PV283
19PW001 - PW036
20PW037 - PW050
19PW051
20PW052 - PW054
19PW061 - PW063
20PW064 - PW068
20PW072
19PW091 - PW093
20PW094
20PW101 - PW102
20PW106
19PW111 - PW117
20PW118 - PW120
20PW156 - PW157
19PW161 - PW162
20PW163 - PW167
20PW201 - PW223
21PW224 - PW230
20PW231 - PW240
21PW241 - PW244
22PW245
20PW261
20PW265 - PW268
21PW278
20PW281
22PW282 - PW284
20PW293
20PW296
20PW301 - PW323
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GroupVariable Number
21PW324 - PW327
21PW461 - PW467
19PW501 - PW503
20PW504
19PW511 - PW518
20PW519 - PW520
20PW526
19PW531 - PW535
20PW536 - PW545
21PW546
20PW556
21PW557
19PW561 - PW563
20PW564
19PW571 - PW573
20PW574 - PW576
19PW591 - PW594
20PW595 - PW596
19PW611 - PW615
20PW616 - PW620
19PW631 - PW632
20PW633 - PW634
19PW661
20PW662
20PW681 - PW683
20PW701 - PW702
20PW711 - PW717
20PW741 - PW742
20PW761
20PW771
1PX071
1PX701
1PY001 - PY008
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GroupVariable Number
1PY021
8PY022
1PY031
8PY036 - PY037
8PY046 - PY047
6PY048
8PY051 - PY052
6PY053
6PY056 - PY057
8PY101 - PY103
8PY111 - PY113
8PY131 - PY133
6PY134 - PY135
8PY141 - PY142
6PY143
6PY151 - PY154
6PY156 - PY157
6PY161 - PY162
6PY166
6PY191
6PY201
6PY221 - PY222
6PY231
6PY241 - PY244
6PY270
8PY271 - PY273
6PY274 - PY275
6PY281
6PY286
1PY301 - PY304
1PY321 - PY323
1PY341 - PY346
1PY361 - PY362
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GroupVariable Number
1PY381
6PY401
7PY409 - PY410
6PY411
6PY421 - PY422
6PY441
6PY451
6PY461 - PY462
7PY463
7PY591 - PY595
6PY611 - PY612
6PY621
6PY631
6PY651
6PY671 - PY672
6PY721
6PY741
2. Spares Affected
None.
B. Concurrent Requirements
None.
C. Reason
This service bulletin describes inspection and repair methods for cracks in lower skins at lap joints and
window corners. If the cracks in the lower skins at lap joints and window corners remain undetected,
those cracks could grow large and cause a sudden decompression.
Before the initial release of this bulletin, the fuselage skin lap joints of six airplanes in the fleet were
inspected. One airplane with the equivalent of 40,000 to 50,000 flight cycles had no cracks detected.
Five airplanes with 52,000 to 77,000 flight cycles and 51,000 to 64,000 flight hours had a total of 273
cracks detected.
The primary cracks were located in the lap joint lower fastener row in the lower skin at tear strap
locations. Secondary cracking was found between the tear straps. Tear straps are located at frames
and half way between frames. The longest crack found was in the skin at a tear strap and was 0.52
inches long, but if linked to adjacent cracks would give a total crack length of 2.0 inches.
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Because the primary cracks in the lower skin were hidden between the upper skin and the tear strap,
an eddy current inspection technique was used to find the cracks. The secondary cracks were also
found with eddy current inspection techniques.
Since the initial release of this bulletin additional cases of cracking have been reported. Fifteen operators
have reported a total of 3,028 cracks detected in the lap splices of 32 airplanes. The airplanes had
44,000 to 82,000 flight cycles. Operators have reported four 737-200 airplanes with between 47,600
and 63,000 cycles that had cracks in the corners of passenger windows. From the fleet data to date,
the window corner cracking is not considered a safety concern for a 737 airplane with 50,000 cycles
or less.
Also, since the initial release of this bulletin, it has been found that certain repairs, called Category 'B'
repairs, may need future supplemental inspections. See Part II of Section 3, Accomplishment Instructions,
for the definition of a Category 'B' repair.
After the release of Revision 1, an open hole rotary probe eddy current inspection of the lower row has
been accomplished on stringer 4, 10, and 14 (referred to as crown skin lap joints) on twelve airplanes
and on the lower lobe and 41 section lap joints on these and other airplanes. The twelve airplanes had
between 36,500 and 84,400 accumulated flight cycles. The open hole inspection resulted in the detection
of many more cracks, primarily on the crown skin lap joints in the area between BS 360 and BS 908.
In one 111 inch length of stringer 4 between BS 540 and BS 727 on an airplane originally externally
eddy current inspected, 82% of the holes had crack indications. On another airplane with 57,000 cycles,
432 cracks were detected on stringer 4, 10, and 14. This, and other airplanes examined, showed
evidence of multiple crack initiation sites and non-standard crack configurations. Operator reported
inspection results have shown the crown skin lap joints between BS 360 and BS 908 to be the area
where the most cracking is occurring. Inspection results from lap joints in section 41, aft of BS 908 in
the crown skin, and common to the lower lobe (below stringer 14) have exhibited markedly fewer cracks.
Since the release of Revision 2, 100 airplanes have had the lap joints cut out and the lap joint repair
installed. Metallurgical analysis and nondestructive test (NDT) open hole inspections of the cut-out
sections of lap joints forwarded to Boeing has resulted in an enhanced understanding of the nature of
the cracking and the ability to accurately detect cracks common to the lower skin. Examination of a
great deal of these physical specimens from various areas of the crown skin lap joints has revealed
that cracks common to tear strap fastener locations are common to the hole edge and typically have
an aspect ratio (length of crack to depth of crack) of 1:1. The NDT rotary probe inspection method,
calibrated using a reference standard to detect a 0.030 inch by 0.030 inch crack, adequately detects
cracks at these locations. Conversely, cracks at fastener locations between tear straps (mid-bay) are
configured with an aspect ratio of 3:1 or greater, are part-through cracks and initiate away from the
edge of the hole in multiple locations. These long and shallow cracks are not readily detectable with
the 0.030 inch NDT calibration reference standard. If not found during the open hole inspection, cracks
can remain and may link up with adjacent cracks. If found during the open hole inspection, the cracks
are most likely longer than the NDT equipment would indicate. In either case, oversizing of the holes
to remove crack indications can not guarantee the crack is completely removed. Remaining cracks
can continue to grow and, because the net area between fasteners has been reduced by oversizing,
both the critical crack length and resulting residual strength has been decreased. As a result of these
findings based on the gathered fleet data, the Revision 1, 2 or 3 Part III - Preventive Change is no
longer an option for use.
Metallurgical analysis of physical specimens from modified airplanes, large scale fatigue testing, and
structural analysis using fleet data has shown that Multiple Site Damage (MSD) - cracking at multiple
adjacent fastener holes - is initiating between 40,000 and 50,000 cycles. MSD leads to a reduction in
residual strength capability of the lap joint and a potential loss of fail-safety capability. This has lead to
the recommendation to accomplish the lap joint repair at a threshold of 50,000 cycles.
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Because the lap joints in section 41, and aft of BS 908 in the crown skin, and common to the lower
lobe (below stringer 14) have exhibited markedly fewer cracks and no MSD, continued monitoring using
external eddy current techniques can continue. An enhanced external eddy current inspection procedure
allows detection of any mid-bay and tear strap cracks before they get to a critical length.
In response to reports of damage to the lower skin and lower fastener row of the stringer 14 lap joint
aft of BS727, Service Bulletin 737-53A1135 was released in 1989 and called for a one-time internal
detailed visual and subsequent HFEC inspection once affected airplanes had reached a threshold of
40,000 flight cycles. Group 1 airplanes (formerly Group 6, Revision 6 airplanes - those -200's built prior
to line position 292), were added to this service bulletin because local areas common to the stringer
10 lap joint near BS727A+10 and stringer 14 lap joint between BS727+10 and BS727A+15 are configured
like the Group 2 thru 15 airplanes. Damage that occurs similar to that seen on Group 2 thru 15 airplanes
can lead to a reduction in residual strength in these local areas. A local repair is therefore recommended
even if no damage was evident after accomplishing the Service Bulletin 737-53A1135 inspections.
Fatigue testing accomplished on skin panels repaired with certain local SRM repairs revealed cracks
that developed common to the lower row of the structural filler as it interfaced to the adjacent 0.036
inch thick skin. As a result of these findings, these repairs are to be removed and replaced with updated
repairs as outlined in item c in Part II of the Accomplishment Instructions, or removed and incorporated
into the lap joint cutout repair as outlined in item d in Part III, IV, VI, or VII of the Accomplishment
Instructions.
Recent fleet data has shown that the skin, stringer and window frames have cracked in locations outside
of the area covered by previous releases of this service bulletin. This results in the need to accomplish
more extensive inspections over a larger area. The additional cracking was found at the following
locations:
– Nine additional fastener holes in the corners of the passenger windows between BS 360 to BS
540, upper forward and lower aft, and between BS 727 and BS 908, lower forward and upper aft.
– Fastener holes in the corners of the passenger windows between BS 360 to BS 540, lower forward
and upper aft, and between BS 727 and BS 908, upper forward and lower aft.
– Fastener holes common to the passenger windows forward of BS 360 and aft of BS 908.
Boeing did a Fuel Burn penalty analysis on the changes given in this service bulletin. Refer to APPENDIX
C for the analysis.
Revision 1 was sent to:
— Add preventive changes, which, if incorporated into an airplane, will allow the operator to stop
inspecting the airplane as shown in this bulletin.
— Delete Figure 5 and add references to 737-200, 737-300, 737-400, and 737-500 SRM figures.
The repair information that was in Figure 5 is now contained in the SRM figures.
— Add a description of category 'A' and category 'B' repairs.
The data given in Notice of Status Change 737-53A1177 NSC 1 does not apply to this bulletin now.
NSC 1 clarified repair instructions, but those instructions have been included in the applicable SRM's.
Revision 2 was sent to:
— change the compliance information. See Section D. Compliance for a table of compliance
information.
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— add a lap joint repair for 737-200 airplanes. The repair is for the lap joints at S-4 (Station 360 -
1016), S-10 (Station 360 - 540 and Station 727 - 908) and S-14 (Station 360 - 540 and Station
727 - 908). The repair must be accomplished on an entire skin panel.
— replace the 737-200 SRM lap joint repair called out in this bulletin. Structural Repair Manual (SRM)
subject 53-30-3 Figure 39 has been replaced by SRM subject 53-30-3 Figure 42, which has
improved fatigue details. If the repair as given in SRM subject 53-30-3 Figure 39 is already installed
and you are not installing the lap joint repair on the entire length of the skin panel, then the SRM
repair (Figure 39) can remain in place.
— include the data given in Notice of Status Change 737-53A1177 NSC 2, which provided information
about a special mandrel required for cold working fastener holes and to give cold working mandrel
wear limits.
— to increase the manpower estimates for the preventive change.
— to allow the use of protruding head fasteners under the wing-to-body fairing.
— include the NAS1149D1165J and NAS1149D0463J washers in paragraph I.A., Parts Necessary
for Each Airplane. Also, equivalent AN960 washers have been listed as allowable substitutes.
— change the sentence in Figure 15, step 3 from "If there is a crack, do the preventive change" to
"If there is a crack indication, do the preventive change".
Revision 3 was sent to:
— Change the information for Hi-Lok fasteners that are common to the lap joint and butt joint while
accomplishing the full length lap joint repair on 737-200 model airplanes. Figures 20, 21 and 22
are changed to refer to service bulletin 737-53-1076, on commonly affected airplanes, for fastener
size information for these Hi-Loks.
— Add information about the standardized modification washers that can be obtained instead of made
as given in Figure 19.
Revision 4 was sent to:
— Add 737-200 airplanes line positions 1 through 291 to the effectivity as Group 6.
— Add data given in Notice of Status Change 737-53A1177 NSC 5. NSC 5 revised some of the weight
and balance information.
— Add data given in Notice of Status Change 737-53A1177 NSC 6. NSC 6 told operators to stop
doing the preventive modification, and recommended doing the lap joint cut-out repair.
— Change compliance recommendations
— Delete the preventive modification for use on all affected lap joints
— Add compliance recommendations for some SRM lap joint repairs
Revision 5 was sent to add lap joint repair information for 737-300 model airplanes.
— Divided Group 1 into Groups 1, 7, 8, 9, 10 and 11 to separate the 737-300/400/500 airplane from
the 737-200 airplane.
— Added Part IV for the 737-300, to the Accomplishment Instructions.
— Added Part V for repair of passenger window corners, on Groups 1, 2, 3, 4, 5 and 7, 8, 9, 10. 11.
— Revised Table 1 in the Compliance section to define the stringer and body stations affected in
each group.
— Revised Compliance section and Accomplishment Instructions for Group 3 and 5 cargo airplanes,
for S-4L/R, S-10L/R and S-14L forward of BS540.
— Revised the Kit to include parts required for the 737-300 airplanes.
— Provide new repair drawings, 65C38450, 65C38451 and 65C38452, for 737-300 airplanes.
— Revised the Manpower estimates.
— Added Figures 22, 23, 24, 25, 26 and revised Figures 2, 3, 4, 6, 8, 9, 10, 11, 12 and 13.
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— NACA post mod inspections which were added in revision 4, have revised inspection method and
intervals.
Revision 6 was sent to:
— Revise wording of the window corner cracking in the Compliance and Description sections.
— Revise Figures 8 and 9 numbered circle symbols and clarify Figure 13 fastener locations.
— Clarify the repair tripler thickness (typically 0.050 inch thick) for Figures 10, 11, 12, and 19.
— Correct the SRM reference to 53-30-3 in Figures 10, 11, 12, and 13.
— Revise the fastener spacing note in Figure 14.
— Add note (a) to Figures 22 and 23 to provide coverage for short edge margin conditions at the
window corner fastener holes.
— Corrected the revision level from 4 to 3 in part C. Reason.
— Revised part E. Compliance section items 6 and 7 and part F. Approval to add revision 6.
— Added revision 6 to Work Instructions Part I D.
— Added magnetic fastener note to Figure 8, Step 2, NACA Modified Joint.
— Added 0.03 inch notch calibration to fastener tables in Figures 10, 11, 12, 13, 21, 24, 25, and 26;
step tables in Figures 20, 22, and 23; Description; Compliance items 4.a. and 4.b. and
Accomplishment Part I items H., I. and Table 2 item (c), Part III item G. and Part IV item H.
— Clarified the trim out area in Step 1 of Figures 24, 25, and 26 includes all 3 fastener holes even if
only one was damaged.
Revision 7 is sent to change the inspection instructions and add new instructions for repair. Recent
fleet data has shown that both stringer and window frames have cracked in locations outside of the
area covered by previous releases of this service bulletin. This results in the need to accomplish more
extensive inspections over a larger area. Nine additional fastener locations in each window corner, for
a total of 12 locations require inspection per Figures 22 and 23. See section 3.B.5. Accomplishment
instructions for the inspection details and section 1.E.10 for compliance times.
— Summary Effectivity - The airplane groups have changed and the number of groups have been
increased from 11 to 28.
— Planning Information - Revise drawing references and add new repair kits for 737-300 airplanes.
Add new repair drawings/kits for 737-400/-500 airplanes.
— Material Information - Add new kits for 737-300/-400/-500 airplanes.
— Paragraph 3.B., Accomplishment Instructions - Work Instructions, revise Part I to remove the
inspection instructions for the crown lap joints, which were released in Revision 1 of Service Bulletin
737-53A1255, revise Part IV to reference Lap Joint Repair instructions for -300 airplanes only,
revise Part V to reference Figures 22-30, add Parts VI and VII to reference new Lap joint Repair
instructions for -400/500 airplanes, add Parts VIII and IX to reference new Window Belt Replacement
instructions for 300/500 airplanes and add Part X to reference post modification inspections at BS
360, BS 540, BS 727 and BS 908..
— Revise Figures 10 and 11 to show repairs of the lap joints at shear tie locations at S-4R and S-10R.
— Revise Figures 22 and 23 to show additional fastener hole locations at S-11 and S-13.
— Revise Figures 24 and 25 to show additional repairs at window corners prior to lap joint repairs at
S-10 and S-14.
— Revise Figure 26 to show additional repairs at butt joints at S-10 and S-14.
— Add new Figure 27 to show upper and lower adjacent window corner repairs at S-11 and S-13.
— Add new Figure 28 to show repairs subsequent to lap joint modifications at S-10 and S-14.
— Add new Figures 29 and 30 to show inspection of fastener holes at unmodified upper and lower
window frame fastener locations at S-11 and S-13.
— Add new Figure 31, to show window frame edge margin requirements.
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— Add new Figures 32 thru 64 to show lap joint modification (repair) locations for crown lap joints
and inspection locations for lap joints outside the crown area. These figures replace figures 2 thru
6.
— Add new Figures 65 thru 69, to show cradle contact areas for support of the fuselage in jig position.
— Add new Figures 70, 71 and 72 to show inspection of the BS 360, BS 540, BS 727 and BS 908
butt splice structure in areas common to the S-4 and S-10 lap joint modification (repair) and common
to the S-9 to S-10 window belt skin panel replacement.
— Add Appendix A to show a Discrepant Structure Report.
— Add Appendix B to show a logic diagram reference more work required if Figures 22 and 23 have
been done.
— Add Appendix C to show fuel burn penalty analysis.
D. Description
Revision 7 - More work is necessary on airplanes changed as shown in revision 5 or revision 6 of this
service bulletin. Additional inspection instructions and new instructions for repair have been added
from the release of revision 7 of this service bulletin. Recent fleet data has shown that both stringer
and window frames have cracked in locations outside of the area covered by previous releases of this
service bulletin. This results in the need to accomplish more extensive inspections over a larger area
until a preventive modification or repair is done.
The inspections for lower row cracking at crown lap joints have been moved from revision 7 of this
service bulletin to service bulletin 737-53A1255. Service bulletin 737-53A1255 revision 2 contains the
inspections for lap joint lower row cracking common to the crown lap joints, the compliance times, and
repeat intervals for those inspections. The instructions for repair of lower row cracking found during
the crown lap joint inspections are also now contained in service bulletin 737-53A1255 revision 2.
Modification of the crown lap joints and inspections and repairs for lower row cracking at lap joints
outside the crown area are still defined within this service bulletin.
The airplane grouping was revised in revision 7 from what was defined in revision 6 of the bulletin. A
correspondence table that identifies the airplane group changes from revision 6 to revision 7 is provided.
See the Reason for Revision section. Note that the airplane groups in SB 737-53A1177 R7 are different
from the airplane groups in SB 737-53A1255 revision 2.
In revision 6 of this service bulletin, the lap joint inspection and lap joint modification (repair) zones for
the crown lap joints and inspection zones for the non-crown lap joints were identified in Figures 2
through 6. Figures 2 through 6 have been deleted from revision 7 and replaced with Figures 32 through
64. Figures 32 through 49 identify the lap joint modification (repair) zones for the crown lap joints.
Figures 50 through 64 identify the lap joint inspection zones for the non-crown lap joints (lap joints
outside the crown area).
Revision 7 includes a window belt skin panel replacement for 737-300 (Part VIII) and 737-500 (Part
IX) that's an optional terminating modification (lap joint modification (repair)) for the S-10 & S-14 lap
repairs and it also terminates the window corner cracking for the panel replaced.
Revision 6 and other earlier revisions of this bulletin used different definitions or terminology for the
terminating lap joint modification of the crown lap joints (S-4L/R, S-10L/R, & S-14L/R between BS 360
and BS 908), where the lap joint is removed and replaced with a reinforcing doubler and tripler. In
earlier revisions, this action was referred to as either a "lap joint modification" or a "lap joint repair". For
example, Parts III and IV of the Work Instructions of revision 6 defined the terminating action of this
modification as a "Lap Joint Repair". Use of the terminology "lap joint repair" was confusing to some
operators since this bulletin also provides instructions to repair lap joints in local areas where cracking
was detected by inspection of the lower row of the lap joint (example: Part II - Crack Repair, in the
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Work Instructions of revision 6). To improve the service bulletin instructions for the operators and to
provide wording that is consistent with current rule making (FAA AD 2002-07-08), in revision 7, the
crown lap joint terminating modification (S-4L/R, S-10L/R, & S-14L/R between BS 360 and BS 908) is
defined as "lap joint modification (repair)". The lap joint modification (repair) for 737-200/-200C, 737-300,
737-400, and 737-500 airplanes is contained in Work Instructions, Section 3B, Parts III, IV, VI, and VII
in revision 7.
Group 2-28:
For lap joints common to stringer 4 between BS 360 and BS 908, and stringers 10 and 14 between BS
360 and BS 540, and between BS 727 and BS 908, accomplish the lap joint modification (repair).  For
all lap joints between BS 259.5 and BS 360, lap joints common to stringer 19 (and 26 for Group 5 and
8 airplanes) between BS 360 and BS 540, lap joints common to stringer 20 (and 25 for Group 5 and 8
airplanes) between BS 727 and BS 1016, and lap joints common to stringer 4, 10, and 14 between BS
908 and BS 1016, perform an external eddy current inspection of the lap joints for cracking common
to the lower row of fasteners in the lower skin commencing at 70,000 flight cycles. For lap joint areas
that have an SRM or other Boeing approved repair doubler:
— If the repair doubler was installed as shown in one of the applicable SRM repairs listed in Part II
of Section 3., Accomplishment Instructions, then it is not necessary to do the repeat inspections
of the lap joint lower row under the repair doubler.
— If the repair doubler has at least three rows of fasteners above the lap joint fasteners and three
rows of fasteners below the lap joint fasteners, then it is not necessary to do the inspection for the
lap joint lower row under the repair doubler.
— If a SRM repair listed in Table 3 of paragraph 1.E., Compliance was installed, inspections are not
necessary. However, the repairs are to be replaced with the applicable cutout repair or a Boeing
approved repair in accordance with the compliance schedule.
— For all other repairs, you must do inspections of the lower row of the lap joint.
Accomplish the repair, and inspections at the times shown in paragraph 1.E., Compliance. The lap
joint repairs shown in Figures 10 thru 12 are applicable to 737-200 Group 2 thru 5 airplanes and
737-200C Group 6 thru 8 cargo airplanes are typical for lap joints at stringer 4 between BS 360 and
BS 908, and for stringers 10 and 14 between BS 360 and BS 540, as well as between BS 727 and BS
908. The upper and lower skins common to the lap joint must be cut out from butt joint to butt joint. A
repair doubler and tripler, as well as tear strap splices are installed to restore strength (except Group
6 thru 8 cargo airplanes on S-4L from BS 520 to BS 540 repair in accordance with 737-100/200 SRM
53-30-3, Figure 42). Repair 737-300, 737-400, 737-500 as given in drawings (except on S-14L/R from
BS727 to BS908 repair in accordance with 737-300 SRM 53-00-01, Repair 30, 737-400 SRM 53-00-01,
Repair 30 or 737-500 SRM 53-00-01, Repair 30). Existing repairs in the area of the repair must be
removed and incorporated into the overall repair. The repair can be installed in smaller sections to
facilitate installation by utilizing the service bulletin Figure 14 splice for 737-200 airplanes or the splice
in the repair drawings for 737-300, 737-400 and 737-500 airplanes. Some of the fastener locations
require eddy current inspection during accomplishment of the repair to ensure a crack free hole prior
to fastener installation. Incorporation of concurrent service bulletins that affect lap joints, circumferential
butt splices, and window belt bonded doublers at the time of the repair is necessary. Information is
included in the lap joint repair instructions and figures to allow use of the typical repair at all of the
above stringer locations. Instead of specific details for all locations, limiting criteria (such as minimum
and maximum fastener spacing, edge margins, oversize replacement fastener options) is specified.
Areas where the configuration is not typical are outlined. When encountered, existing repairs are to be
documented in detail and submitted to Boeing for alternate repair instructions.
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If any crack is found during eddy current inspection of the areas other than those governed by the lap
joint cutout repair as given in this bulletin, remove the fastener. Clean up the hole within the SRM
section 51 allowable hole tolerance for the size and type of fastener removed to ensure a clean hole
for inspection. Verify the crack by accomplishing an eddy current inspection in accordance with 737
NDT Part 6, 51-00-00, Figure 16. If any crack is evident, you must cut out the damaged skin common
to the lower row and install a repair as shown in Part II - Crack Repair or contact Boeing. Send all
cutout sections in these areas to Boeing for evaluation. If cracking is not evident after inspecting the
open hole, reinstall the original size and type of fastener. Inspect for white powder, skin bulging, or
other signs of corrosion in these areas when accomplishing the eddy current inspection or when the
SRM repair is being installed. If corrosion is discovered, contact Boeing for repair instructions.
Boeing recommends do the inspection, preventive modification or repair of the affected 737-200, 300,
400 and 500 airplanes as required of the window corner fastener holes during the accomplishment of
the lap joint modification (repair). If the hole probe inspection and the preventive modification is not
done as given in this service bulletin, Boeing recommends do a High Frequency Eddy Current (HFEC)
surface inspection for cracks around the window corner fasteners as given in Figures 22 and 23 per
paragraph 1.E., Compliance, Tables 8 and 9.
Group 18, 22, 28:
For lap joints common to stringer 14 between BS360 and BS540, accomplish the lap joint modification
(repair) at the times shown in paragraph 1.E., Compliance. The configuration of the window belt skin
panel is unique on these airplanes, contact Boeing for repair and modification instructions of the S-14,
BS 360 to BS 540 lap joints. For lap joints common to stringer 4 between BS360 and BS908 and stringer
10 between BS360 to BS540 and BS727 to BS908 and stringer 14 between BS727 to BS908 modification
of the lap joints per this service bulletin is not necessary. For all other lap joints, perform an external
eddy current inspection for cracking at the times shown in paragraph 1.E., Compliance.
Group 1:
Cut out the lower row of the lap joints shown in Figure 7 and install a repair as shown in Part II - Crack
Repair over the affected area which is at S-10 and S-14 for 737-200 Passenger and S-10 only for the
Cargo version. Accomplish the repair at the times shown in paragraph 1.E., Compliance. Note that this
modification is necessary even if no cracks were found during a previous inspection in accordance with
Service Bulletin 737-53A1135. If the Service Bulletin 737-53A1135 Figure 2 repair has been
accomplished on the stringer 14 lap joint over the entire affected area, no further action is required. If
the repair has been installed over a portion of the affected area, contact Boeing for repair instructions.
Group 2-28:
For all window corners between BS360 - BS540 and BS727 - BS908 as shown in Figures 22 and 23.
Remove the 12 fasteners from the opposite corners and inspect the open holes. If no cracks are found,
oversize the fastener holes and install the referenced fasteners. If any crack is found, see below and
follow the Part V Accomplishment Instruction. See the Compliance Section E.10 for follow-on inspection
recommendations for window corners not modified by this service bulletin.
Group 2-8:
For locations where window cracks are found do a repair as shown in Figure 24 (single corner repair
- S-14), Figure 25 (single corner repair - S-10) or Figure 27 (adjacent corner repairs - S-10/S-14). If
the adjacent lap joint also requires a repair do the above applicable window corner repair concurrently
with the lap joint repair as shown in Figure 11 (S-10) and Figure 12 (S-14). As an option the operator
can splice in an integrated section of the lap joint repair as shown in Figure 14.
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At butt joints where window corner cracking requires a repair and the adjacent lap joint also requires
a repair, do a repair by cutting the existing lap joint repair and splice in the integrated repair as shown
in Figure 26 to reduce the stack-up common to the butt joint structure.
At lap joints where the lap joint repair has already been done and window cracks are found, repair the
window corners as shown in Figure 28.
Group 9-17:
For locations where window corner cracking requires a repair and the adjacent lap joint requires a
concurrent modification, refer to repair drawings 65C38451 (S-10) and 65C38452 (S-14).
For locations where window corner cracking in the skin requires a repair and the adjacent lap joint is
being modified by SRM (for example S-14 between BS 827 and BS 908 or between BS 847 and BS
908) repair in accordance with 737-300 SRM 53-00-01, Repair 37.
For locations where window corner cracking requires a repair and the adjacent lap joint is not being
modified, repair in accordance with 737-300 SRM 53-00-01, Repair 34.
For Groups 9 thru 17 airplanes, the window belt skin panel replacement, as given in Accomplishment
Instructions, Part 3.B.8. provides an optional lap joint modification (repair) for the S-10L/R and S-14L/R
lap joints and terminates the inspections of the window corner structure.
Group 23-27:
For locations where window corner cracking requires a repair and the adjacent lap joint is not modified,
repair in accordance with 737-500 SRM 53-00-01, Repair 34.
For locations where window corner cracking in the skin requires a repair and the adjacent lap joint is
being modified by SRM (for example S-14 between BS 827 and BS 908 or between BS 847 and BS
908) repair in accordance with 737-500 SRM 53-00-01, Repair 37. For other window corner locations
that require a repair and the adjacent lap joint also requires a repair, contact Boeing.
For Groups 23 thru 27 airplanes, the window belt skin panel replacement, as given in Part 3.B.9. of
the Accomplishment Instructions, provides an optional lap joint modification (repair) for the S-10L/R
and S-14L/R lap joints and terminates the inspections of the window corner structure.
Group 18-22, 28:
For Groups 18 thru 22 and 28, if window cracking is found, contact Boeing for repair instructions.
NOTE: If you find damage that is not covered by this bulletin, contact Boeing for repair
instructions and do the work instructed by Boeing. Boeing Service Letter
737-SL-51-042, Damage Reporting and Repair Plan/Design Guidelines, is an
acceptable procedure to request information from Boeing for additional structural
repair instructions. The Service Letter describes what information must be provided
to Boeing before a structural repair can be provided.
1.
SEND TO:
Boeing Commercial Airplane Company Spares Distribution Center Repair Overhaul
and Exchange Services, SSA 111 2201 South 142nd, Door W10 Seatac, Wa 98168,
USA Attention: Airline Support Manager Forward to Post Production Fuselage Stress,
for engineering evaluation.
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2. The following service bulletins have inspections, preventive changes, and repairs
with Airworthiness Directive mandates. Because of common access, if one of these
bulletins is applicable to your airplane, Boeing recommends that you incorporate it
along with this bulletin. Refer to the applicable service bulletin for more information.
3. Because of common access, if Service Bulletin 737-53-1179 or 737-53A1210 are
applicable to your airplane, Boeing recommends that you consider incorporating it
along with this bulletin. Accomplishment of this service bulletin at revisions 2, 3, 4,
5 or 6 terminates inspections under the repair doubler area for Service Bulletin
737-53A1210. Refer to Service Bulletin 737-53-1179 and 737-53A1210 for more
information.
4. When you do this service bulletin it is possible that you will also satisfy requirements
specified in the 737 Aging Airplane Corrosion Prevention and Control Program. Refer
to D6-38528 to determine if your airplane is applicable.
5. The following 737-200 Maintenance Planning Document (MPD) items are related to
the inspections in this service bulletin: 4-53-01, 4-53-25, and 4-53-26.
6. The following 737-300/400/500 MPD items are related to the inspections in this
service bulletin: P53-10-00-A and -B, and P53-10-00-H thru -K.
The work in this service bulletin is done in the maintenance zone(s) given below.
Group 1:
Affected Maintenance Zones
ZoneModel
1-7, 1-8737-200, 737-200C
Group 2-5:
Affected Maintenance Zones
ZoneModel
1-7, 1-8737-200
Group 6-8:
Affected Maintenance Zones
ZoneModel
1-7, 1-8737-200C
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Group 9-18:
Affected Maintenance Zones
ZoneModel
107, 108737-300
Group 19-22:
Affected Maintenance Zones
ZoneModel
107, 108737-400
Group 23-28:
Affected Maintenance Zones
ZoneModel
107, 108737-500
E. Compliance
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to
this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this
service bulletin mandatory.
Federal Aviation Administration (FAA) Airworthiness Directives AD 2002-07-08, AD 2002-07-10, AD
2002-07-11, AD 2003-14-06, AD 2004-18-06, AD 2008-08-23, AD 2008-09-13, AD 2013-09-01, AD
88-22-11 R1, AD 89-09-03, AD 89-22-04, AD 91-07-04, AD 91-08-12, AD 92-25-09, AD 98-11-04 R1
are related to this service bulletin. The effective date of AD 2002-07-08 is May 17, 2002.
1. Group 2-28:
Lap Joint Modification (Repair) for Crown Lap Joints. Refer to Figures 32 thru 49 for the lap joint
modification (repair) zones.
Table 1: Lap joint modification (repair) for crown lap joints.
Compliance TimeActionCondition
At the times mandated by AD 2002-
07-08.
Accomplish the lap joint modification
(repair) to the crown lap joints in ac-
cordance with the Accomplishment
Instructions of this Service Bulletin.
(a)
All airplanes.
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Table 1: Lap joint modification (repair) for crown lap joints.
Compliance TimeActionCondition
(a)
– For Groups 2 through 8 airplanes, instructions for S-4L/R, S-10L/R, and S-14L/R lap joint modification
(repair) are given in Part 3.B.3. of the Accomplishment Instructions.
– For Groups 9 through 17 airplanes, instructions for S-4L/R, S-10L/R, and S-14L/R lap joint modification
(repair) are given in Part 3.B.4. of the Accomplishment Instructions.
– For Groups 19 through 21 airplanes, instructions for S-4L/R, S-10L/R, and S-14L/R lap joint modification
(repair) are given in Part 3.B.6. of the Accomplishment Instructions.
– Groups 23 through 27 airplanes, instructions for S-4L/R, S-10L/R, and S-14L/R lap joint modification
(repair) are given in Part 3.B.7. of the Accomplishment Instructions.
– For Groups 9 through 17 airplanes, the window belt skin panel replacement as given in Part 3.B.8.
of the Accomplishment Instructions provides an optional lap joint modification (repair) for the S-10L/R
and S-14L/R lap joints.
– For Groups 23 through 27 airplanes, the window belt skin panel replacement as given in Part 3.B.9.
of the Accomplishment Instructions provides an optional lap joint modification (repair) for the S-10L/R
and S-14L/R lap joints.
– For Group 18, 22 and 28 airplanes, instructions for lap joint modification (repair) are not included in
this service bulletin. Contact Boeing for lap joint modification (repair) instructions and do the work in-
structed by Boeing.
NOTE: 1. No rework is required on 737-200C airplanes (Group 6, 7 and 8) that have been
repaired at S-4L or S-10L from BS 500 to BS 540 as given in Revision 2, 3 or
4 of this bulletin.
2. Skin repair doublers that end on the lower row of a lap joint further degrade the
fatigue life and accelerate cracking in the lower skin. Contact Boeing for alternate
lap joint modification (repair) instructions for areas with repair doublers ending
on the lower row.
3. If the airplane has had a skin panel replaced, the compliance times for
modification of the lower row for both the upper lap joint and the lower lap joint
common to the replaced panel may be affected. Contact Boeing for alternate
lap joint modification (repair) instructions for lap joint areas affected by skin panel
replacements.
2. Group 2-28:
Inspection Recommendations for the Areas Outside the Crown Lap Joint Area.
For all lap joints identified in bold lines in Figures 50 thru 64 inspect as follows:
NOTE: For Group 2, 4, 5 and 7, Configuration 2 airplanes, refer to Paragraph 1.E.12., for
inspections in areas affected by a service bulletin 737-53-1077 modification or repair.
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Table 2: Inspection for cracking at lap joints outside the crown lap joint area.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
5,000 flight cycles (a)At the times mandated
by AD 2002-07-08.
Do an external Eddy Current and general visual
inspection of the lap joints outside the crown
area for cracks in accordance with Accomplish-
ment Instructions 3.B.1.b, Non-Crown Lap Joint
Inspections.
All Air-
planes.
-Before further flight.Repair in accordance with Accomplishment In-
structions 3.B.2., Part II Crack Repair.
Any crack
found.
(a) There is currently no terminating action for lap joints in these areas.
NOTE: 1. Skin repair doublers that end on the lower row of a lap joint further degrade the
fatigue life and accelerate cracking in the lower skin. Contact Boeing for alternate
lap joint inspection and modification instructions for areas with repair doublers
ending on the lower row.
2. If the airplane has had a skin panel replaced, the compliance times for inspection
of the lower row for both the upper lap joint and the lower lap joint common to
the replaced panel may be affected. Contact Boeing for alternate lap joint
modification instructions for lap joint areas affected by skin panel replacements.
3. Group 1:
Airplane line numbers 1-291:
a. Using the inspection area map (Figure 7), inspect the lap joints with a Dual Frequency Eddy
Current inspection from the exterior as given in Figure 8 of this service bulletin at the times
mandated by FAA AD 2002-07-11.
b. If cracking is found, refer to 737-100/200 SRM 53-30-3, Figure 44 for the repair and repair
before further flight. If corrosion is found, contact Boeing for repair instructions and do the
instructions provided by Boeing before further flight.
c. Mandatory modification is required at the times defined in FAA AD 2002-07-11. The modification
is the same as the repair as described in 737-100/200 SRM 53-30-3, Figure 44.
4. Group 2-28:
Post NACA modification inspections for airplanes that have already accomplished the NACA
modifications.
The following instructions are mandated by AD 2002-07-08:
a. Accomplish post NACA modification inspections and lap joint modification (repair) in the crown
area.
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The following instructions apply to airplanes that have received the NACA modification
(Preventive Change) in the crown stringers (stringers 4L and 4R between BS 360 and BS 908
and stringers 10L and 10R and 14L and 14R between BS 360 and BS 540 and also between
BS 727 and BS 908), except S-14L between the main cargo door and BS 540 for Group 6
thru 8 airplanes.
Within 12,000 cycles of performing the Preventive Change per Part III of the Accomplishment
Instructions in SB 737-53A1177 Revision 1, 2, or 3 or within 750 flight cycles after the effective
date of Airworthiness Directive AD 2002-07-08, whichever is later, inspect the lap joints as
given in Figure 8 (external inspection). Repeat the inspections at 1,500 cycle intervals. If there
is any crack indication and the inside of the fuselage is accessible, the crack can be verified
by doing an eddy current inspection around the head of the rivet as given in Figure 9. If there
is no crack indication with the internal inspection, then repairs are not required.
Alternately, within 12,000 cycles of performing the Preventive Change per Part III of the
Accomplishment Instructions in SB 737-53A1177 Revision 1, 2 or 3 or within 750 flight cycles
after the effective date of Airworthiness Directive AD 2002-07-08, whichever is later, inspect
the lap joints between tear straps as given in Figure 9 (internal inspection) and under tear
straps as given in Figure 8 (external inspection). Repeat the inspections at 4,500 cycles
intervals.
Note that the Figure 9 inspection applies only to rivets where there is no tear strap or bonded
doubler. If any crack indication is found, remove the fastener. Oversize the hole within the
SRM Chapter 51 allowable hole tolerance for the size and type of fastener removed to ensure
a clean hole for inspection. Verify the crack by accomplishing an eddy current inspection in
accordance with 737 NDT Part 6, 51-00-00, Figure 16, use 0.03 inch notch calibration. If any
crack is found, repair the lap joints as given in Part II Crack Repair as defined in the
Accomplishment Instructions. If no cracks are found, install the same size and type of fastener
removed. Report all crack findings and label and send in cutout sections to Boeing.
Within 18,000 cycles of performing the Preventive Change per Part III of the Accomplishment
Instructions in SB 737-53A1177 Revision 1, 2, or 3, repair the lap joints per the Lap Joint
Repair Figures 10, 11, or 12 of the Accomplishment Instructions in SB 737-53A1177 Revision
4, 5, 6 or 7.
b. Accomplish post NACA modification inspections outside the crown area.
The following instructions apply to airplanes that have received the NACA modification
(Preventive Change) in areas outside the main fuselage crown area. These areas are for all
lap joints not defined in paragraph 4.a. above.
Within 20,000 cycles of performing the Preventive Change per Part III of the Accomplishment
Instructions in SB 737-53A1177 Revision 1, 2, or 3 or within 750 flight cycles after the effective
date of Airworthiness Directive AD 2002-07-08, whichever is later, inspect the lap joints as
given in Figure 8 (external inspection). Repeat the inspections at 1,500 cycle intervals. If there
is any crack indication and the inside of the fuselage is accessible, the crack can be verified
by doing an eddy current inspection around the head of the rivet per Figure 9. If there is no
crack indication with the internal inspection, then repairs are not required.
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Alternately, within 20,000 cycles of performing the Preventive Change per Part III of the
Accomplishment Instructions in SB 737-53A1177 Revision 1, 2 or 3 or within 750 flight cycles
after the effective date of Airworthiness Directive AD 2002-07-08, whichever is later, inspect
the lap joints between tear straps as given in Figure 9 (internal inspection) and under the tear
straps as given in Figure 8 (external inspection). Repeat the inspections at 4,500 cycles
intervals.
Note that the Figure 9 inspection applies only to rivets where there is no tear strap or bonded
doubler. If any crack indication is found, remove the fastener. Oversize the hole within the
SRM Chapter 51 allowable hole tolerance for the size and type of fastener removed to ensure
a clean hole for inspection. Verify the crack by accomplishing an eddy current inspection in
accordance with 737 NDT Part 6, 51-00-00, Figure 16, use 0.03 inch notch calibration. If any
crack is found, repair the lap joints as given in Part II - Crack Repair, of Section 3 -
Accomplishment Instructions. If no cracks are found, install the same size and type of fastener
removed. If any crack, corrosion or evidence of corrosion is found, contact Boeing for repair
instructions and do the work instructed by Boeing before further flight.
The inspection must be accomplished all the way up to the door cutouts. This includes the
main entry door, service doors, and the cargo doors.
Inspection of the lap joints common to all butt splice joints must also be accomplished.
Label and send in to Boeing all lap joint sections with crack indications that have been cutout
and repaired per the SRM.
Note that there is currently no terminating action for the lap joints in these areas.
5. Group 2-8:
Limitation of SB 737-53A1177 Revision 2 and Revision 3 lap joint modifications (repairs).
The SB 737-53A1177 Revision 2 and Revision 3 lap joint modification (repair) is limited to 45,000
cycles from the time of the modification (repair) as a result of fatigue test results, unless the
extended tear straps are installed, as given in item 6, below.
6. Group 2-8:
Modification of existing 737-53A1177 Revision 2 and Revision 3 lap joint modification (repair) tear
strap splice straps by installing extended tear strap splice straps per Service Bulletin 737-53A1177
Revision 4, 5, 6 or 7, and Post Repair Inspection Instructions.
Lap joint modifications (repairs) done per Service Bulletin 737-53A1177 Revision 2 and Revision
3 may be modified with extended tear strap splice straps per Figures 10, 11, and 12. If this
modification is carried out, it must be done within 45,000 cycles from the time the Revision 2 or
Revision 3 lap joint repair was installed. Starting at a threshold of 45,000 cycles from the time the
Revision 2 and Revision 3 repair was installed, inspections given in item 7.a.(1)(b) and 7.a.(2),
below apply to this modified repair.
7. Group 2-28:
The instructions in this section apply to Groups 2-28, as defined by the groups below. Post repair
Inspection Instructions for the Service Bulletin Revision 4, 5, 6 and 7 Lap Joint Modification (Repair)
with extended tear strap splice straps and Service Bulletin Revision 7 Window Belt Skin Panel
Replacement.
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a. Group 2-17, 19-21, 23-27:
Accomplish the post repair inspections as given in Accomplishment Instructions 3.B.1.d at
the threshold and repeat interval defined below:
(1) Compliance Time:
(a) Compliance Time of 45,000 cycles after the service bulletin Revision 4, 5, 6, or 7 lap
joint modification (repair) was installed.
(b) Compliance Time of 45,000 cycles after the service bulletin Revision 2 or Revision
3 lap joint modification (repair) was installed, provided the extended tear straps are
installed, as given in item 6 above.
(2) Repeat Intervals (not to exceed) 2,800 cycles.
(3) The Compliance time and repeat intervals are the same for both the internal and external
procedures.
(4) If any crack, corrosion or evidence of corrosion is found, contact Boeing for repair
instructions and do the work instructed by Boeing before further flight.
b. Group 18, 22, 28:
For Group 18, 22 and 28 airplanes, post repair inspection instructions will be provided with
the lap joint modification (repair) instructions that operators must obtain from Boeing. Refer
to Compliance Table 1.
8. Group 2-17, 19-21, 23-27:
Replacement of local lap joint SRM repairs.
Table 3 - Replacement of 737-100/200 SRM 53-30-3, Figure 39, 737-300/-500 SRM 53-00-01,
Figure 227, or 737-400 SRM 53-00-01, Figure 229
Replacement Compliance TimeLocation of 737-100/200 SRM 53-30-
3, Figure 39, 737-300/500 SRM 53-00-
01, Figure 227 or 737-400 SRM 53-00-
01, Figure 229 repairs
Within 15,000 cycles from repair installa-
tion, or 5,000 cycles after Revision 4
date of this service bulletin, whichever
occurs later.
S-4L and 4R between BS 259.5-1016
S-10L and 10R between BS 259.5-540
and BS 727-1016
S-14L and 14R between BS 259.5-540
and BS 727-1016
Within 20,000 cycles from repair installa-
tion, or 5,000 cycles after Revision 4
date of this service bulletin, whichever
occurs later.
All other areas between BS259.5-1016
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NOTE: 1. Replacement of repairs defined by 737-100/200 SRM 53-30-3, Figure 39,
737-300 SRM 53-00-01, Figure 227, 737-400 SRM 53-00-01, Figure 229 or
737-500 SRM 53-00-01, Figure 227 is mandated by AD 2002-07-10.
2. On 737-200/300 airplanes, if the lap joints are being cut out and repaired per
this Service Bulletin Work Instructions, sections 3.B.3. Part III or 3.B.4 Part IV,
the 737-100/200 SRM 53-30-3, Figure 39 or 737-300 SRM 53-00-01, Figure
227 repair is to be removed and repaired as given in this bulletin, SB
737-53A1177, Figure 16, 17 or 18.
3. On 737-300 airplanes, if the lap joints are being cut out and repaired per this
Service Bulletin Work Instructions, section 3.B.8 Part VIII, for replacement of
the 737-300 SRM 53-00-01, Figure 227 repair(s), contact Boeing for replacement
instructions, and do the work instructed by Boeing.
4. On 737-200/300 airplanes, if the lap joints are not being cut out, the 737-100/200
SRM 53-30-3, Figure 39 or 737-300 SRM 53-00-01, Figure 227 repair are to be
removed and inspected as given in this bulletin 737-53A1177 Figure 20, and
replaced with 737-100/200 SRM 53-30-3, Figure 42 or 737-300 SRM 53-00-01,
Repair 30.
5. On 737-400/500 airplanes, for replacement of the 737-400 SRM 53-00-01, Figure
229 repairs or 737-500 SRM 53-00-01, Figure 227 repairs, contact Boeing for
replacement instructions, and do the work instructed by Boeing.
9. Group 2-17, 19-21, 23-27:
The instructions in this section apply to Groups 2-17, 19-21, 23-27, as defined by the groups below.
Supplemental Structural Inspection Document (SSID) items affected by lap joint cutout repair or
the window belt replacement.
The following instructions apply to SSI's defined in the 737 Supplemental Structural Inspection
Documents (737-200) D6-37089 Revision D, (737-200C) D6-37089 Rev E, or (737-300/-400/-500)
D6-82669 Rev New that are common to Service Bulletin 737-53A1177 lap joint modification (repair)
and/or Service Bulletin 737-53A1177 window belt skin panel replacement, as applicable. SSI's
affected are the fuselage circumferential splices (F-38), fuselage crown skin and stringers (F-39),
and fuselage skin longitudinal lap splices (F-48). Federal Aviation Administration (FAA) Airworthiness
Directives AD 98-11-04 R1, AD 2008-08-23 and AD 2008-09-13, as applicable, are related to these
SSI's.
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### Page 55

Group 2-5:
Table 4 - Alternate SSID inspection requirements for 737-200 airplanes with lap joint modification (repair).
SSI F-38B, F-38C, F-38D, F-38E, F-39A, F-39B, F-39C, F-39F, F-39G, F-39H, and F-48A.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in Part 1.E.13.
Compliance
As given in Part 1.E.13.
Compliance
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-38C
and F-38D inspections at
Stringers S-4 and S-10,
Left and Right at Body
Stations 540 and 727.
However the inspections
of the butt splice structure
as given in Part X of the
Work Instructions meet the
requirements of these SSI
details. Accomplish these
inspections at the Compli-
ance Time given in this ta-
ble.
SSI F-38C and F-38D.
Production Fuselage Cir-
cumferential Butt Splice
Structure at BS 540 and
BS 727 common to the
Stringers S-4 and S-10
Lap Joint Modification
(Repair)
As given in Service Bulletin
737-53A1322 Original Is-
sue
As given in Service Bulletin
737-53A1322 Original Is-
sue
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-38B
and F-38E inspections at
Stringers S-4 and S-10,
Left and Right at Body
Stations 360 and 908.
However the inspections
of the butt splice structure
as given in Service Bulletin
737-53A1322 meet the re-
quirements of these SSI
details. Accomplish these
inspections at the Compli-
ance Time given in this ta-
ble.
SSI F-38B and F-38E.
Production Fuselage Cir-
cumferential Butt Splice
Structure at BS 360 and
BS 908 common to the
Stringers S-4 or S-10 Lap
Joint Modification (Repair)
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### Page 56

Group 2-5:
Table 4 - Alternate SSID inspection requirements for 737-200 airplanes with lap joint modification (repair).
SSI F-38B, F-38C, F-38D, F-38E, F-39A, F-39B, F-39C, F-39F, F-39G, F-39H, and F-48A.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in D6-37089 Revi-
sion D, DTR Check Forms
F-39A, F-39B and F-39C
At the next SSID inspec-
tion on this airplane
Although the service bul-
letin lap joint modification
(repair) affects SSI F-39 at
stringers S-4 and S-10, as
applicable, the internal in-
spection methods and inter-
vals as given in D6-37089
Revision D, DTR Check
Forms F-39A, F-39B and
F-39C are still effective.
External inspections in the
areas with the lap joint
modification (repair) will
not be possible, so the in-
spections must be accom-
plished from the inside of
the fuselage. Accomplish
these inspections at the
Compliance Time given in
this table.
SSI F-39A, F-39B, and F-
39C. Production Fuselage
Crown Stringers S-4 and
S-10 common to the Lap
Joint Modification (Repair)
As given in D6-37089 Revi-
sion D, DTR Check Forms
F-39F, F-39G and F-39H
At the next SSID inspec-
tion on this airplane
Although the service bul-
letin lap joint modification
(repair) affects SSI F-39 at
stringers S-4 and S-10, as
applicable, the external in-
spection methods and inter-
vals as given in D6-37089
Revision D, DTR Check
Forms F-39F, F-39G and
F-39H are still effective.
With the lap joint modifica-
tion (repair) installed, the
inspection is to be directed
at the lap joint modification
(repair) doubler and tripler.
Accomplish these inspec-
tions at the Compliance
Time given in this table.
SSI F-39F, F-39G, and F-
39H. Lap Joint Modification
(Repair) Doubler and
Tripler
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### Page 57

Group 2-5:
Table 4 - Alternate SSID inspection requirements for 737-200 airplanes with lap joint modification (repair).
SSI F-38B, F-38C, F-38D, F-38E, F-39A, F-39B, F-39C, F-39F, F-39G, F-39H, and F-48A.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in Part 1.E.7.
Compliance
As given in Part 1.E.7.
Compliance
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-48 in-
spections. However the in-
spections defined in Part
1.E.7. Compliance meet
the SSID inspection re-
quirements of F-48A. Ac-
complish these inspections
at the Compliance Time
given in this table.
SSI F-48A. Fuselage Skin
Longitudinal Lap Splices
Group 6-8:
Table 5 - Alternate SSID inspection requirements for 737-200C airplanes with lap joint modification (repair).
SSI F-38B, F-38C, F-38D, F-38E, F-39A, F-39B, F-39C, F-39F, F-39G, F-39H, and F-48A.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in Part 1.E.13.
Compliance
As given in Part 1.E.13.
Compliance
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-38C
and F-38D inspections at
Stringers S-4 and S-10,
Left and Right at Body
Stations 540 and 727.
However the inspections
of the butt splice structure
as given in Part X of the
Work Instructions meet the
requirements of these SSI
details. Accomplish these
inspections at the Compli-
ance Time given in this ta-
ble.
SSI F-38C and F-38D.
Production Fuselage Cir-
cumferential Butt Splice
Structure at BS 540 and
BS 727 common to the
Stringers S-4 and S-10
Lap Joint Modification
(Repair)
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### Page 58

Group 6-8:
Table 5 - Alternate SSID inspection requirements for 737-200C airplanes with lap joint modification (repair).
SSI F-38B, F-38C, F-38D, F-38E, F-39A, F-39B, F-39C, F-39F, F-39G, F-39H, and F-48A.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in Service Bulletin
737-53A1322 Original Is-
sue
As given in Service Bulletin
737-53A1322 Original Is-
sue
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-38B
and F-38E inspections at
Stringers S-4 and S-10,
Left and Right at Body
Stations 360 and 908.
However the inspections
of the butt splice structure
as given in Service Bulletin
737-53A1322 meet the re-
quirements of these SSI
details. Accomplish these
inspections at the Compli-
ance Time given in this ta-
ble.
SSI F-38B and F-38E.
Production Fuselage Cir-
cumferential Butt Splice
Structure at BS 360 and
BS 908 common to the
Stringers S-4 and S-10
Lap Joint Modification
(Repair)
As given in D6-37089 Revi-
sion E, CTR Check Forms
F-39A, F-39B and F-39C
At the next SSID inspec-
tion on this airplane
Although the service bul-
letin lap joint modification
(repair) affects SSI F-39 at
stringers S-4 and S-10, as
applicable, the internal in-
spection methods and inter-
vals as given in D6-37089
Revision E, DTR Check
Forms F-39A, F-39B and
F-39C are still effective.
External inspections in the
areas with the lap joint
modification (repair) will
not be possible, so the in-
spections must be accom-
plished from the inside of
the fuselage. Accomplish
these inspections at the
Compliance Time given in
this table.
SSI F-39A, F-39B and F-
39C. Production Fuselage
Crown Stringers S-4 and
S-10 common to the Lap
Joint Modification (Repair)
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### Page 59

Group 6-8:
Table 5 - Alternate SSID inspection requirements for 737-200C airplanes with lap joint modification (repair).
SSI F-38B, F-38C, F-38D, F-38E, F-39A, F-39B, F-39C, F-39F, F-39G, F-39H, and F-48A.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in D6-37089 Revi-
sion E, DTR Check Forms
F-39F, F-39G and F-39H
At the next SSID inspec-
tion on this airplane
Although the service bul-
letin lap joint modification
(repair) affects SSI F-39 at
stringers S-4 and S-10, as
applicable, the external in-
spection methods and inter-
vals as given in D6-37089
Revision E, DTR Check
Forms F-39F, F-39G and
F-39H are still effective.
With the lap joint modifica-
tion (repair) installed, the
inspection is to be directed
at the lap joint modification
(repair) doubler and tripler.
Accomplish these inspec-
tions at the Compliance
Time given in this table.
SSI F-39F, F-39G, and F-
39H. Lap Joint Modification
(Repair) Doubler and
Tripler
As given in Part 1.E.7.
Compliance
As given in Part 1.E.7.
Compliance
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-48 in-
spections. However the in-
spections defined in Part
1.E.7. Compliance meet
the SSID inspection re-
quirements of F-48A. Ac-
complish these inspections
at the Compliance Time
given in this table.
SSI F-48A. Fuselage Skin
Longitudinal Lap Splices
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### Page 60

Group 9-17, 19-21, 23-27:
Table 6 - Alternate SSID inspection requirements for 737-300/-400/-500 airplanes with lap joint modification
(repair). SSI F-38A, F-38B, F-38C, F-38D, F-38G, F-38H, F-39A, F-39B, F-39E, F-39F, and F-48B.
Repeat Interval (Not to
Exceed)
Compliance TimeActionCondition
As given in Part 1.E.13.
Compliance
As given in Part 1.E.13.
Compliance
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-38B
and F-38C inspections at
Stringers S-4 and S-10,
Left and Right at Body
Stations 540 and 727.
However the inspections
of the butt splice structure
as given in Part X of the
Work Instructions meet the
requirements of these SSI
details. Accomplish these
inspections at the Compli-
ance Time given in this ta-
ble.
SSI F-38B and F-38C.
Production Fuselage Cir-
cumferential Butt Splice
Structure at BS 540 and
BS 727 common to the
Stringers S-4 and S-10
Lap Joint Modification
(Repair)
As given in Service Bulletin
737-53A1322 Original Is-
sue
As given in Service Bulletin
737-53A1322 Original Is-
sue
The installation of the ser-
vice bulletin lap joint modi-
fication (repair) will have
an impact on SSI F-38A
and F-38D inspections at
Stringers S-4 and S-10,
Left and Right at Body
Stations 360 and 908.
However the inspections
of the butt splice structure
as given in Service Bulletin
737-53A1322 meet the re-
quirements of these SSI
details. Accomplish these
inspections at the Compli-
ance Time given in this ta-
ble.
SSI F-38A and F-38D.
Production Fuselage Cir-
cumferential Butt Splice
Structure at BS 360 and
BS 908 common to the
Stringers S-4 or S-10 Lap
Joint Modification (Repair)
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