Commercial 

Airplanes 737

Service Bulletin

Number: 737-53A1293

Original Issue: August 13, 2008

Revision 2: August 10, 2011

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460

Inspection and Repair

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BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET

Copyright © 2008 The Boeing Company

Unpublished Work - All Rights Reserved

Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable

subject matter. Boeing also claims copyright in this document as a compilation and/or collective work.

This document includes proprietary information owned by The Boeing Company and/or one or more third parties.

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BOEING SERVICE BULLETIN 737-53A1293

BLANK PAGE
Table of Contents

Revision Transmittal Sheet ............................................ 5

Summary ...................................................... 7

1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

E. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

H. Weight and Balance Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

1. Existing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

2. Data supplied with this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3. Installation Drawings Used in the Preparation of this Service Bulletin . . . . . . . . . . . . 46

K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

C. Parts Necessary For Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

2. Parts and Materials Supplied by the Operator . . . . . . . . . . . . . . . . . . . . . . . . 47

3. Parts Modified and Reidentified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 49

3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

FIGURE 1: THIS FIGURE DELETED AT REVISION 1 [Group 1] . . . . . . . . . . . . . . . . . . . . . 59

FIGURE 2: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA

400 - STA 460 [Group 1] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

FIGURE 3: THIS FIGURE DELETED AT REVISION 1 [Group 2] . . . . . . . . . . . . . . . . . . . . . 62

FIGURE 4: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA

400 - STA 460 [Group 2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

FIGURE 5: FUSELAGE SKIN - CRACK REMOVAL [Group 1] . . . . . . . . . . . . . . . . . . . . . . 65

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

[Group 1] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

FIGURE 7: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1

AND S-2R, STA 400 - STA 460 [Group 1] . . . . . . . . . . . . . . . . . . . . . . . . . . 78

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BOEING SERVICE BULLETIN 737-53A1293
FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

[Group 1] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

FIGURE 9: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1

AND S-2R, STA 400 - STA 460 [Group 2] . . . . . . . . . . . . . . . . . . . . . . . . . . 91

FIGURE 10: FUSELAGE SKIN - CRACK REMOVAL [Group 2] . . . . . . . . . . . . . . . . . . . . . . 93

FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION [Group 2] . . . . . . . . . . . . 96

FIGURE 12: POST REPAIR - CRITICAL FASTENER ROW INSPECTION [Group 2] . . . . . . . . . . 102

APPENDIX A: CHEM-MILL STEP CRACK DAMAGE CUT-OUT AND REPORT . . . . . . . . . . . . . 104

APPENDIX B: CHEM-MILL STEP CRACK DAMAGE REPORT . . . . . . . . . . . . . . . . . . . . . . 105

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BOEING SERVICE BULLETIN 737-53A1293
Commercial 

Airplanes 737

Service Bulletin

Revision Transmittal Sheet Number: 737-53A1293

Original Issue: August 13, 2008

Revision 2: August 10, 2011

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460

Inspection and Repair

This revision includes all pages of the service bulletin.

COMPLIANCE INFORMATION RELATED TO THIS REVISION

No more work is necessary on the airplanes changed in accordance with Revision 1 of this service bulletin.

REASON FOR REVISION

This revision is sent to revise the group 1 repair figures and add the group 2 repair instructions and post repair

inspection.

These sections were changed:

1. Summary Background information Revised.

2. Summary Action Group 1 and Group 2 information revised.

3. Summary Industry Support Information, warranty statement revised.

4. Summary Material Information revised.

5. Paragraph 1.A.1., Airplanes, paragraph added.

6. Paragraph 1.C., Reason, information revised and revision 2 reason added.

7. Paragraph 1.D., Description, Group 1 and Group 2 repair instructions revised.

8. Paragraph 1.E., Compliance, Table 1, Table 2 and Table 3 Condition column revised and note (c) added.

Table 4 Action column revised. Table 5 Condition column revised and repair compliance details, note (a)

was revised and note (c) added. Table 6 added.

9. Paragraph 1.F., Approval, AMOC statement revised.

10. Paragraph 1.G., Manpower, Group 2 table revised to add repair and post repair inspection information.

11. Paragraph 1.H., Weight and Balance Changes, Table replaced with equating statement.

12. Paragraph 1.J.1., Existing Data, book references revised.

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13. Paragraph 2.A., Material - Price and Availability, paragraph added.

14. Paragraph 2.B., Industry Support Information, warranty statement revised.

15. Paragraph 2.C.2., Parts and Materials Supplied by the Operator, Group 2 table added.

16. Paragraph 3.A., General information, notes revised.

17. Paragraph 3.B., Work instructions, changed as follows:

a. PART 1 - step 5.d. and 6.d. added.

b. PART 2 - step 3 revised.

c. PART 3 - step 4.d. and 5.d. added.

d. PART 5 - caution deleted. Step 5 revised and step 6 added.

e. PART 6 - step 4 revised and step 5 added.

f. PART 7 and PART 8 added.

18. Figure 5 revised to show crack removal information only. View A and B deleted. Flag note table deleted.

View C, now view A, revised to show crack information only. Step 1 and 2 deleted. New step 2 added. Foot

notes (a), (b), (c), and (d) deleted. New foot notes (a) and (d) revised.

19. Figure 6, new illustration added, new step 1 and footnotes (g) thru (j) added.

20. Figure 8, new illustration added, new step 1 and footnotes (g) thru (j)added.

21. Figure 10, Figure 11 and Figure 12 added.

22. Appendix A, Group reference deleted.

Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity, to show the location

of important changes.

Pages with no vertical lines have no important changes.

REVISION HISTORY

Original Issue: August 13, 2008

Revision 1: July 07, 2010

Revision 2: August 10, 2011

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BOEING SERVICE BULLETIN 737-53A1293
Commercial 

Airplanes 737

Service Bulletin

Summary Number: 737-53A1293

Original Issue: August 13, 2008

Revision 2: August 10, 2011

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460

Inspection and Repair

CONCURRENT REQUIREMENTS

None

BACKGROUND

Accomplishment of the inspections in this service bulletin will make sure that fuselage skin cracks at stringers

S-1 and S-2R, between Body Stations STA 400 and STA 460 are found and repaired. An Air Traffic Control

(ATC) antenna was installed at this location at delivery on the affected airplanes. All airplanes listed in this

service bulletin require inspection even if the ATC antenna has been removed. This action is necessary to find

and repair fatigue cracks of the skin panels at the chem-mill steps. Continued operation with undetected skin

cracks could cause unscheduled down time for repairs or possibly a decompression of the airplane.

Boeing has received several reports from multiple operators regarding fuselage skin cracks adjacent to the ATC

antenna.

A total of 60 cracks have been found on Group 1 airplanes (10 inch tear strap bays); cracks have been found

at both S-1 and S-2R; the affected airplanes had accumulated between 40,080 and 67,032 total flight cycles.

A total of 3 cracks have been found on Group 2 airplanes (20 inch tear strap bays); cracks have only been found

at S-1, but similar cracking is possible at S-2R; the affected airplanes had accumulated between 43,565 and

44,700 total flight cycles.

Analysis by Boeing indicates that the cracks are caused by fatigue due to high tension stresses and local bending

at the edge of the chem-mill pockets of the bonded skin. The cracks initiate at the inner surface of the skin and

typically originate at multiple sites along the chem-mill step. Multiple site originations can result in several adjacent

partial-thickness cracks. These adjacent partial-thickness cracks can be subsequently linked together before

propagating through the full-thickness of the skin.

Accomplishment of the work given in this service bulletin will make sure that cracks in the fuselage skin at

stringers S-1 and S-2R, between STA 400 and STA 460 are detected and repaired.

Boeing Service Related Problem (SRP) 737-SRP-53-0334 is related to this service bulletin.

Multi-Operator Message (MOM) MOM-MOM-09-0807-01B (R1) is related to this service bulletin.

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ACTION

1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA 400 and

STA 460.

2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at stringers

S-1 and S-2R, between STA 400 and STA 460.

3. Do external Non Destructive Inspections (NDI) for cracks in the fuselage skin along the chem-mill steps at

stringers S-1 and S-2R, between STA 400 and STA 460. The NDI's that can be used are Medium Frequency

Eddy Current (MFEC), Magneto Optical Imaging (MOI), C-Scan or Ultrasonic Phased Array (UTPA).

4. If no crack is found, do repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps

at stringers S-1 and S-2R, between STA 400 and STA 460 at intervals in accordance with Paragraph 1.E.,

Compliance.

5. Group 1:

If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions,

do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not covered by a repair) for

cracks in accordance with Paragraph 1.E., Compliance

a. Crack(s) found before 35,000 total flight cycles.

b. Crack(s) found in four or more tear strap bays.

c. Crack(s) found longer than 5 inches.

d. Crack(s) found are not contained within the skin cut-out.

If all of the following is found as a result of the external DI and NDI, do the repair, the critical fastener row

inspection and repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps not

covered by a repair at intervals specified in Paragraph 1.E., Compliance.

a. Crack(s) found at or after 35,000 total flight cycles.

b. Crack(s) found in three or less strap bays.

c. Crack(s) found 5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out.

6. Group 2:

If any of the following is found as a result of the external DI and NDI, contact Boeing for repair instructions,

do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not covered by a repair) for

cracks in accordance with Paragraph 1.E., Compliance.

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BOEING SERVICE BULLETIN 737-53A1293
a. Crack(s) found before 33,000 total flight cycles.

b. Crack(s) found between STA 400 and STA 420.

c. Crack(s) found between STA 440 and STA 460.

d. Crack(s) found longer than 12.5 inches.

e. Crack(s) found are not contained within the skin cut-out.

If all of the following are found as a result of the external DI and NDI, do the repair, the critical fastener row

inspection and repeat external DI and NDI for cracks in the fuselage skin along the chem-mill steps not

covered by a repair, at intervals specified in Paragraph 1.E., Compliance.

a. Crack(s) found at or after 33,000 total flight cycles.

b. Crack(s) found between STA 420 and STA 440.

c. Crack(s) found 12.5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out.

EFFECTIVITY

737-300/-400/-500 Airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes.

COMPLIANCE

Federal Aviation Administration (FAA) Airworthiness Directive AD 2008-19-03 is related to this service bulletin.

Refer to Paragraph 1.E., Compliance.

INDUSTRY SUPPORT INFORMATION

Boeing warranty remedies are not available for the inspection,and repair procedures given in this service bulletin.

MANPOWER

Refer to Paragraph 1.G., Manpower.

MATERIAL INFORMATION

Operator Supplied Parts/Materials.

Refer to Paragraph 2.A., Material - Price and Availability

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BOEING SERVICE BULLETIN 737-53A1293
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BOEING SERVICE BULLETIN 737-53A1293
Commercial 

Airplanes 737

Service Bulletin

Number: 737-53A1293

Original Issue: August 13, 2008

Revision 2: August 10, 2011

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Stringer S-1 and Stringer S-2R, Station 400 to Station 460

Inspection and Repair

1. PLANNING INFORMATION

A. Effectivity

1. Airplanes

Refer to Service Bulletin Index Document D6-19567 Part 3 for Airplane Variable Number, Line

Number, and Serial Number data.

This service bulletin is for the airplanes shown below.

GROUP CONFIGURATION DESCRIPTION

737 - 300/-400/-500 Airplanes, line numbers 1001 thru 2552, which

had an ATC antenna installed at STA 430 at delivery, with 10 inch

tear strap bays.

1 -

Airplanes not inspected in accordance with the original issue of this

service bulletin.

1

Airplanes inspected in accordance with the original issue of this

service bulletin and the last inspection was a Detailed Inspection

procedure.

2

Airplanes inspected in accordance with the original issue of this

service bulletin and the last inspection was a MFEC or MOI or C-Scan

Non-Destructive Inspection procedure.

3

Airplanes inspected in accordance with Boeing

Multi-Operator-Message MOM-MOM-09-0807-01B (R1), dated

15-Dec-2009 and the last inspection was a Detailed Inspection

procedure.

4

Airplanes inspected in accordance with Boeing

Multi-Operator-Message MOM-MOM-09-0807-01B (R1), dated

15-Dec-2009 and the last inspection was a MFEC or MOI or C-Scan

Non-Destructive Inspection procedure.

5

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GROUP CONFIGURATION DESCRIPTION

737 - 300/-400/-500 Airplanes, line numbers 2553 thru 3132, all of

which had an ATC antenna installed at STA 430 at delivery, with 20

inch tear strap bays.

2 -

Airplane Models:

737-300, 737-400, 737-500

Variable Number Group

PJ301 - PJ302 1

PJ551 1

PJ552 - PJ561 2

PJ601 - PJ615 2

PJ811 2

PJ816 - PJ817 2

PM389 - PM399 1

PM401 - PM417 1

PM541 - PM542 1

PM543 - PM550 2

PM551 - PM564 1

PP048 - PP054 1

PP140 - PP160 1

PP198 - PP199 1

PP221 1

PP508 - PP517 1

PP518 - PP520 2

PP805 - PP808 1

PP874 - PP875 1

PP876 - PP877 2

PP910 - PP930 1

PP951 - PP952 1

PP966 - PP967 1

PP984 - PP990 1

PP993 1

PQ013 - PQ016 1

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BOEING SERVICE BULLETIN 737-53A1293
Variable Number Group

PQ038 - PQ041 1

PQ069 - PQ085 1

PQ101 - PQ199 1

PQ201 - PQ202 1

PQ230 1

PQ237 1

PQ251 - PQ267 1

PQ281 - PQ296 1

PQ297 - PQ299 2

PQ301 - PQ307 1

PQ331 - PQ332 1

PQ341 - PQ344 1

PQ345 - PQ348 2

PQ361 - PQ369 1

PQ370 - PQ373 2

PQ391 - PQ395 2

PQ401 - PQ407 1

PQ408 - PQ410 2

PQ411 - PQ413 1

PQ414 - PQ418 2

PQ421 1

PQ431 - PQ438 2

PQ447 - PQ448 2

PQ451 2

PQ454 2

PQ471 - PQ472 1

PQ473 - PQ475 2

PQ481 1

PQ486 - PQ487 1

PQ491 - PQ493 1

PQ771 1

PQ772 2

PQ791 - PQ793 1

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BOEING SERVICE BULLETIN 737-53A1293
Variable Number Group

PQ801 - PQ805 1

PQ931 - PQ932 1

PQ933 - PQ935 2

PQ951 2

PQ971 - PQ997 2

PR001 - PR017 2

PR021 - PR034 2

PR041 - PR045 2

PR061 - PR072 2

PR077 - PR082 2

PR091 - PR092 2

PR096 2

PR101 2

PR121 - PR122 2

PR131 - PR132 2

PR141 - PR143 2

PR161 - PR172 2

PR181 2

PS601 - PS616 1

PS617 - PS630 2

PS631 1

PS636 - PS638 1

PS641 - PS644 1

PS651 - PS657 1

PS666 - PS669 1

PS691 - PS692 1

PS701 - PS703 1

PS704 - PS706 2

PS751 - PS762 1

PS763 - PS799 2

PS811 2

PS836 - PS837 2

PS841 - PS846 2

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BOEING SERVICE BULLETIN 737-53A1293
Variable Number Group

PS851 - PS852 2

PS856 2

PS861 - PS863 2

PS866 - PS868 2

PS871 - PS874 2

PS896 - PS897 2

PS901 - PS941 2

PS956 - PS957 2

PS961 - PS963 2

PS971 - PS978 2

PT001 - PT011 1

PT012 - PT015 2

PT021 - PT028 1

PT029 - PT031 2

PT041 - PT063 1

PT064 2

PT101 - PT105 1

PT121 - PT125 1

PT126 - PT138 2

PT146 - PT148 1

PT161 - PT170 1

PT181 - PT187 1

PT188 2

PT211 - PT220 1

PT295 1

PT301 - PT306 1

PT307 - PT309 2

PT331 - PT360 1

PT381 - PT399 1

PT401 - PT438 1

PT501 - PT512 1

PT513 - PT517 2

PT561 - PT565 1

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BOEING SERVICE BULLETIN 737-53A1293
Variable Number Group

PT581 - PT584 1

PT585 - PT586 2

PT611 - PT621 1

PT641 - PT642 1

PT643 - PT644 2

PT651 - PT655 1

PT656 2

PT671 - PT672 1

PT681 - PT685 2

PT701 - PT703 1

PT716 - PT717 2

PT721 - PT725 2

PT801 - PT834 2

PT851 - PT854 2

PT871 - PT886 2

PT901 - PT930 2

PT971 - PT973 2

PT981 - PT985 2

PT996 2

PU001 - PU025 1

PU301 2

PU311 - PU313 2

PV021 - PV055 1

PV201 - PV203 1

PV204 - PV209 2

PV226 - PV229 2

PV231 - PV237 1

PV271 - PV272 1

PV281 - PV283 1

PV284 - PV287 2

PV296 2

PV301 - PV302 2

PV351 2

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BOEING SERVICE BULLETIN 737-53A1293
Variable Number Group

PV356 - PV357 2

PW027 - PW054 1

PW061 - PW068 1

PW072 1

PW086 - PW088 2

PW091 - PW094 1

PW101 - PW102 1

PW106 1

PW111 - PW120 1

PW156 - PW157 1

PW161 - PW167 1

PW168 - PW171 2

PW201 - PW244 1

PW245 - PW252 2

PW261 1

PW262 - PW264 2

PW265 - PW268 1

PW271 - PW276 2

PW278 1

PW281 1

PW282 - PW292 2

PW293 1

PW296 1

PW301 - PW327 1

PW401 - PW408 2

PW411 - PW418 2

PW421 - PW424 2

PW431 - PW435 2

PW441 - PW450 2

PW461 - PW467 1

PW501 - PW502 1

PW504 1

PW511 - PW520 1

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BOEING SERVICE BULLETIN 737-53A1293
Variable Number Group

PW521 - PW522 2

PW524 - PW525 2

PW526 1

PW527 - PW530 2

PW531 - PW546 1

PW547 - PW550 2

PW556 - PW557 1

PW561 - PW564 1

PW571 - PW576 1

PW591 - PW596 1

PW611 - PW620 1

PW621 - PW622 2

PW631 - PW634 1

PW635 - PW637 2

PW661 - PW662 1

PW681 - PW683 1

PW701 - PW702 1

PW711 - PW717 1

PW741 - PW742 1

PW761 1

PW771 1

PW831 2

PW851 - PW856 2

2. Spares Affected

None.

B. Concurrent Requirements

None.

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BOEING SERVICE BULLETIN 737-53A1293
C. Reason

Accomplishment of the inspections in this service bulletin will make sure that fuselage skin cracks at

stringers S-1 and S-2R, between Body Stations STA 400 and STA 460 are found and repaired. An Air

Traffic Control (ATC) antenna was installed at this location at delivery on the affected airplanes. All

airplanes listed in this service bulletin require inspection even if the ATC antenna has been removed.

This action is necessary to find and repair fatigue cracks of the skin panels at the chem-mill steps.

Continued operation with undetected skin cracks could cause unscheduled down time for repairs or

possibly a decompression of the airplane.

Boeing has received several reports from multiple operators regarding fuselage skin cracks adjacent

to the ATC antenna.

A total of 60 cracks have been found on Group 1 airplanes (10 inch tear strap bays); cracks have been

found at both S-1 and S-2R; the affected airplanes had accumulated between 40,080 and 67,032 total

flight cycles.

A total of 3 cracks have been found on Group 2 airplanes (20 inch tear strap bays); cracks have only

been found at S-1, but similar cracking is possible at S-2R; the affected airplanes had accumulated

between 43,565 and 44,700 total flight cycles.

Analysis by Boeing indicates that the cracks are caused by fatigue due to high tension stresses and

local bending at the edge of the chem-mill pockets of the bonded skin. The cracks initiate at the inner

surface of the skin and typically originate at multiple sites along the chem-mill step. Multiple site

originations can result in several adjacent partial-thickness cracks. These adjacent partial-thickness

cracks can be subsequently linked together before propagating through the full-thickness of the skin.

Accomplishment of the work given in this service bulletin will make sure that cracks in the fuselage

skin at stringers S-1 and S-2R, between STA 400 and STA 460 are detected and repaired.

Boeing Service Related Problem (SRP) 737-SRP-53-0334 is related to this service bulletin.

Multi-Operator Message (MOM) MOM-MOM-09-0807-01B (R1) is related to this service bulletin.

Revision 1 was sent to add more inspection areas, Ultrasonic Phased Array (UTPA) inspection

procedure, post repair inspection and change compliance. The option to use a Detailed Inspection (DI)

only has been removed. This revision requires that a Non Destructive Inspection (NDI) and a DI be

accomplished.

For Group 1 only, remove airplanes from the effectivity and add a repair.

Revision 2 is sent to revise the group 1 repair figures and add the group 2 repair instructions and post

repair inspection.

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BOEING SERVICE BULLETIN 737-53A1293
D. Description

1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA

400 and STA 460.

2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at

stringers S-1 and S-2R, between STA 400 and STA 460.

3. Do external Non Destructive Inspections (NDI) for cracks in the fuselage skin along the chem-mill

steps at stringers S-1 and S-2R, between STA 400 and STA 460. The NDI's that can be used are

Medium Frequency Eddy Current (MFEC), Magneto Optical Imaging (MOI), C-Scan or Ultrasonic

Phased Array (UTPA).

4. If no crack is found, do repeat external DI and NDI for cracks in the fuselage skin along the chem-mill

steps at stringers S-1 and S-2R, between STA 400 and STA 460 at intervals in accordance with

Paragraph 1.E., Compliance.

5. Group 1:

If any of the following is found as a result of the external DI and NDI, contact Boeing for repair

instructions, do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not

covered by a repair) for cracks in accordance with Paragraph 1.E., Compliance.

a. Crack(s) found before 35,000 total flight cycles.

b. Crack(s) found in four or more tear strap bays.

c. Crack(s) found longer than 5 inches.

d. Crack(s) found are not contained within the skin cut-out.

If all of the following is found as a result of the external DI and NDI, do the repair, the critical

fastener row inspection and repeat external DI and NDI for cracks in the fuselage skin along the

chem-mill steps not covered by a repair at intervals specified in Paragraph 1.E., Compliance.

a. Crack(s) found at or after 35,000 total flight cycles.

b. Crack(s) found in three or less strap bays.

c. Crack(s) found 5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out.

6. Group 2:

If any of the following is found as a result of the external DI and NDI, contact Boeing for repair

instructions, do the repair and do external DI and NDI of the fuselage skin chem-mill steps (not

covered by a repair) for cracks in accordance with Paragraph 1.E., Compliance.

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BOEING SERVICE BULLETIN 737-53A1293
a. Crack(s) found before 33,000 total flight cycles.

b. Crack(s) found between STA 400 and STA 420.

c. Crack(s) found between STA 440 and STA 460.

d. Crack(s) found longer than 12.5 inches.

e. Crack(s) found are not contained within the skin cut-out.

If all of the following is found as a result of the external DI and NDI, do the repair, the critical

fastener row inspection and repeat external DI and NDI for cracks in the fuselage skin along the

chem-mill steps not covered by a repair, at intervals specified in Paragraph 1.E., Compliance.

a. Crack(s) found at or after 33,000 total flight cycles.

b. Crack(s) found between STA 420 and STA 440.

c. Crack(s) found 12.5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out.

Revision 1 - More work is necessary on airplanes inspected as shown in the original issue of this service

bulletin. Additional areas have been identified to be inspected for chem-mill line cracking, the Detailed

Inspection must be done with a Non Destructive Inspection method, and the compliance times shown

in Paragraph 1.E., Compliance have been reduced.

Revision 2 - No more work is necessary on the airplanes changed in accordance with Revision 1 of

this service bulletin.

The work in this service bulletin is done in the maintenance zone(s) given below.

Affected Maintenance Zones

Model Zone

737-300, 737-400, 737-500 107

E. Compliance

Federal Aviation Administration (FAA) Airworthiness Directive AD 2008-19-03 is related to this service

bulletin.

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BOEING SERVICE BULLETIN 737-53A1293
NOTE: If any repair in the Accomplishment Instructions, Paragraph 3.B., Work Instructions, is not

applicable, contact Boeing for repair instructions and do the repair before further flight.

Group 1, Configuration 1:

Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 1,800 -

flight cycles

after the date

of Revision 1

on this service bulletin.

Before

35,000 total

flight cycles.

Option 1:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instruction, Paragraph 3.B.,

PART 1.

Airplanes not inspected

in accordance with the

original issue of this

service bulletin.

AND

Do external Non Destructive Inspections (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 1 using one of

the following procedures:

1. Medium Frequency Eddy Current

(MFEC)

or

2. Magneto Optical Imaging (MOI)

or

3. C-Scan

(a) (c)

OR

Within 1,800

flight cycles

after the date

of Revision 1

on this service bulletin.

Before

35,000 total

flight cycles.

Option 2:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instruction, Paragraph 3.B.,

PART 1.

AND

Do external Non Destructive Inspections (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 1 using the

Ultrasonic Phased Array (UTPA) procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 1:

Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Do external DI and NDI of the fuselage skin chem-mill steps for cracks

in accordance with Accomplishment

Instructions, Paragraph 3.B., PART

1.

No crack found in the

fuselage skin.

AND

Option 1 used.

(b) (b)

OR (a) (c)

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.No crack found in the

fuselage skin.

AND (b) (b)

Option 2 used.

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 1:

Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Contact Boeing for repair instructions Before further flight. -

in accordance with Accomplishment

Instructions, Paragraph 3.B., PART 1

and do the repair.

Crack(s) found before

35,000 total flight cycles.

OR

Cracks found in four or

more tear strap bays. AND (do Option 1 or Option 2 )

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Option 1:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

(not covered by a repair) for cracks in

accordance with Accomplishment Instructions, Paragraph 3.B., PART 3.

OR

Crack(s) longer than 5

inches.

OR

Crack(s) found are not

contained within the

skin cut-out.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.Option 2:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

(not covered by a repair) for cracks in

accordance with Accomplishment Instructions, Paragraph 3.B., PART 3.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 1:

Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Do the repair in accordance with Ac- Before further flight. -

complishment Instructions, Paragraph

3.B., PART 2.

Crack(s) found at or after 35,000 total flight

cycles.

AND

Cracks(s) found in

three or fewer tear

strap bays.

AND (do Option 1 or Option 2 )

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Option 1:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

(not covered by a repair) for cracks in

accordance with Accomplishment Instructions, Paragraph 3.B., PART 3.

AND

Crack(s) found 5 inches

or shorter.

AND

Crack(s) found are

contained within the

skin cut-out.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.Option 2:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

(not covered by a repair) for cracks in

accordance with Accomplishment Instructions, Paragraph 3.B., PART 3.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 1:

Table 1: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

(a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following

apply:

1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved

by a Boeing company authorized representative who was authorized by the FAA to make such findings.

2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the

circumferential direction.

Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for

repeat inspections under the repair area only.

(b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if

you do as follows:

1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections

must be done within 1,800 flight cycle repeat intervals. Then Option 2 inspections that follow must

be done within 2,400 flight cycle repeat intervals.

2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection

must be done within 2,400 flight cycles after the Option 2 inspection. Then Option 1 inspections that

follow must be done within 1,800 flight cycle repeat intervals.

(c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an

existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy

Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used.

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 2, 4:

Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 900 -

flight cycles

after the date

of Revision 1

on this service bulletin.

Before

35,000 total

flight cycles.

Option 1:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 1.

Airplanes inspected in

accordance with the

original issue of this

service bulletin and the

last inspection was Detailed Inspection (DI)

procedure.

OR

Airplanes inspected in

accordance with Boeing

Multi-Operator Message MOM-MOM-09-

0807-01B (R1) and the

last inspection was Detailed Inspection (DI)

procedure.

AND

Do external Non Destructive Inspections (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 1 using one of

the following procedures:

1. Medium Frequency Eddy Current

(MFEC)

or

2. Magneto Optical Imaging (MOI)

or

3. C-Scan

(a) (c)

OR

Within 900 -

flight cycles

after the date

of Revision 1

on this service bulletin.

Before

35,000 total

flight cycles.

Option 2:

Do external Detailed Inspection (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 1.

AND

Do external Non Destructive Inspections (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 1 using the

Ultrasonic Phased Array (UTPA) procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 2, 4:

Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Do repeat external DI and NDI of the

fuselage skin chem-mill steps for

cracks in accordance with Accomplishment Instructions, Paragraph 3.B.,

PART 1.

No crack found in the

fuselage skin.

AND

Option 1 used.

(b) (b)

OR (a) (c)

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.No crack found in the

fuselage skin.

AND (b) (b)

Option 2 used.

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 2, 4:

Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Contact Boeing for repair instructions Before further flight. -

in accordance with Accomplishment

Instructions, Paragraph 3.B., PART 1

and do the repair

Crack(s) found before

35,000 total flight cycles.

OR

Cracks found in four or

more tear strap bays. AND (do Option 1 or Option 2)

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Option 1:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

OR

Crack(s) found longer

than 5 inches.

OR

Crack(s) found are not

contained within the

skin cut-out.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.Option 2:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 2, 4:

Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Do the repair in accordance with Ac- Before further flight. -

complishment Instructions, Paragraph

3.B., PART 2.

Crack(s) found at or after 35,000 total flight

cycles.

AND

Cracks(s) found in

three or fewer tear

strap bays.

AND (do Option 1 or Option 2)

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Option 1:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

AND

Crack(s) found 5 inches

or shorter.

AND

Crack(s) found are

contained within the

skin cut-out.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.Option 2:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 2, 4:

Table 2: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

(a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following

apply:

1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved

by a Boeing company authorized representative who was authorized by the FAA to make such findings.

2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the

circumferential direction.

Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for

repeat inspections under the repair area only.

(b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if

you do as follows:

1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections

must be done within 1,800 flight cycle repeat intervals. Then Option 2 inspections that follow must

be done within 2,400 flight cycle repeat intervals.

2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection

must be done within 2,400 flight cycles after the Option 2 inspection. Then Option 1 inspections that

follows must be done within 1,800 flight cycle repeat intervals.

(c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an

existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy

Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used.

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 3, 5:

Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 1,800 -

flight cycles

after the date

of Revision 1

on this service bulletin.

Before

35,000 total

flight cycles.

Option 1:

Do external Detailed Inspections (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 1.

Airplanes inspected in

accordance with the

original issue of this

service bulletin and the

last inspection was a

Non Destructive Inspection (NDI) procedure. AND

OR Do external Non Destructive Inspection (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 1 using one of

the following procedures:

Airplanes inspected in

accordance with Boeing

Multi-Operator Message MOM-MOM-09-

0807-01B (R1) and the

last inspection was a

Non Destructive Inspection (NDI) procedure.

1. Medium Frequency Eddy Current

(MFEC)

or

2. Magneto Optical Imaging (MOI)

or

3. C-Scan

(a) (c)

OR

Within 1,800

flight cycles

after the date

of Revision 1

on this service bulletin.

Before

35,000 total

flight cycles.

Option 2:

Do external Detailed Inspections (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 1.

AND

Do external Non Destructive Inspection (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 1 using the

Ultrasonic Phased Array (UTPA) procedure.

(a)

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Group 1, Configuration 3, 5:

Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Do repeat external DI and NDI of the

fuselage skin chem-mill steps for

cracks in accordance with Accomplishment Instructions, Paragraph 3.B.,

PART 1.

No crack found in the

fuselage skin.

AND

Option 1 used.

(b) (b)

OR (a) (c)

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.No crack found in the

fuselage skin.

AND (b) (b)

Option 2 used.

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Group 1, Configuration 3, 5:

Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Contact Boeing for repair instructions Before further flight. -

in accordance with Accomplishment

Instructions, Paragraph 3.B., PART 1

and do the repair.

Crack(s) found before

35,000 total flight cycles.

OR

Crack(s) found in four

or more tear strap bays. AND (do Option 1 or Option 2)

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Option1:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

OR

Crack(s) found longer

than 5 inches.

OR

Crack(s) found are not

contained within the

skin cut-out.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.Option 2:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 3, 5:

Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Do the repair in accordance with Ac- Before further flight. -

complishment Instructions, Paragraph

3.B., PART 2.

Crack(s) found at or after 35,000 total flight

cycles.

AND

Cracks(s) found in

three or fewer tear

strap bays.

AND (do Option 1 or Option 2)

1,800 flight cycles.Within 1,800 flight cycles after the last NDI.Option1:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

AND

Crack(s) found 5 inches

or shorter.

AND

Crack(s) found are

contained within the

skin cut-out.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

2,400 flight cycles.Within 2,400 flight cycles after the last NDI.Option 2:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 3 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 1, Configuration 3, 5:

Table 3: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

(a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following

apply:

1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved

by a Boeing company authorized representative who was authorized by the FAA to make such findings.

2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the

circumferential direction.

Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for

repeat inspections under the repair area only.

(b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if

you do as follows:

1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections

must be done within 1,800 flight cycle repeat intervals. The Option 2 inspections that follow must be

done within 2,400 flight cycle repeat intervals.

2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection

must be done within 2,400 flight cycles after the Option 2 inspection. The Option 1 inspections that

follows must be done within 1,800 flight cycle repeat intervals.

(c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an

existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy

Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used.

Group 1:

Table 4: Post Repair - Critical Fastener Row Inspection

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 60,000 flight cycles -

from the time the repair was

installed

Do Detailed Inspections (DI) or Non

Destructive Inspections (NDI) of the

skin at the critical row of fasteners in

the repair for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 4.

Airplanes with a repair

installed in accordance

with this service bulletin.

In accordance

with Repair Assessment Guidelines D6-38669

Revision C Figure 2-9.

In accordance with Repair

Assessment Guidelines D6-

38669 Revision C Figure 2-

9.

Do repeat DI or NDI of the skin at the

critical row of fasteners in the repair

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 4.

No crack found.

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BOEING SERVICE BULLETIN 737-53A1293
Group 1:

Table 4: Post Repair - Critical Fastener Row Inspection

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Contact Boeing for repair instructions Before further flight. -

in accordance with Accomplishment

Instructions, Paragraph 3.B., PART 4

and do the repair.

Any crack found.

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BOEING SERVICE BULLETIN 737-53A1293
Group 2:

Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 500 -

flight cycles

after the release date of

Revision 1 on

this service

bulletin.

Before

33,000 total

flight cycles.

Option 1:

Do external Detailed Inspections (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 5.

AND

All Airplanes

Do external Non Destructive Inspections (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 5 using one of

the following procedures:

1. Medium Frequency Eddy Current

(MFEC)

or

2. Magneto Optical Imaging (MOI)

or

3. C-Scan

(a) (c)

OR

Within 500 -

flight cycles

after the release date of

Revision 1 on

this service

bulletin.

Before

33,000 total

flight cycles.

Option 2:

Do external Detailed Inspections (DI)

of the fuselage skin chem-mill steps

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., PART 5.

AND

Do external Non Destructive Inspections (NDI) of the fuselage skin chemmill steps for cracks in accordance

with Accomplishment Instructions,

Paragraph 3.B., PART 5 using the

Ultrasonic Phased Array (UTPA) procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 2:

Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 500 flight cycles after 500 flight cycles.

the last NDI.

Do repeat external NDI of the fuselage

skin chem-mill steps for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., PART 5.

No crack found in the

fuselage skin.

AND

Option 1 used.

(b)

(b)

(a) (c) OR

1,000 flight cycles.Within 1,000 flight cycles after the last NDI.No crack found in the

fuselage skin.

AND (b) (b)

Option 2 used.

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BOEING SERVICE BULLETIN 737-53A1293
Group 2:

Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Contact Boeing for repair instructions Before further flight. -

in accordance with Accomplishment

Instructions, Paragraph 3.B., PART 5

and do the repair.

Crack(s) found before

33,000 total flight cycles.

OR

Crack(s) found between

STA 400 and STA 420. AND (do Option 1 or Option 2)

Within 500 flight cycles after 500 flight cycles.

the last NDI.

Option 1:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6.

OR

Crack(s) found between

STA 440 and STA 460.

OR

Crack(s) found longer

than 12.5 inches.

OR

(b)

(b)

AND

Crack(s) found are not

contained within the

skin cut-out.

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

1,000 flight cycles.Within 1,000 flight cycles after the last NDI.Option 2:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 2:

Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Do the repair in accordance with Ac- Before further flight. -

complishment Instructions, Paragraph

3.B., PART 7.

Crack(s) found at or after 33,000 total flight

cycles.

AND

Crack(s) found between

STA 420 and STA 440.

AND (do Option 1 or Option 2)

Within 500 flight cycles after 500 flight cycles.

the last NDI.

Option 1:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6.

AND

Crack(s) found 12.5

inches or shorter.

AND

Crack(s) found are

contained within the

skin cut-out.

(b)

(b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6 using one of the

following procedures:

1. MFEC

or

2. MOI

or

3. C-Scan

(a) (c)

OR

1,000 flight cycles.Within 1,000 flight cycles after the last NDI.Option 2:

Do external DI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6.

(b) (b)

AND

Do external NDI of the fuselage skin

chem-mill steps (not covered by a repair) for cracks in accordance with

Accomplishment Instructions, Paragraph 3.B., PART 6 using UTPA procedure.

(a)

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BOEING SERVICE BULLETIN 737-53A1293
Group 2:

Table 5: External Fuselage Skin Chem-Mill Inspection - Stringers S-1 and S-2R, STA 400 - STA 460

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

(a) It is not necessary to inspect the chem-mill steps under an external repair doubler provided all of the following

apply:

1. The repair was installed in accordance with this service bulletin, or approved by the FAA, or approved

by a Boeing company authorized representative who was authorized by the FAA to make such findings.

2. The repair extends a minimum of three rows of fasteners on each side of the chem-mill line in the

circumferential direction.

Installation of an external repair that meets the requirements of items 1 and 2 above is terminating action for

repeat inspections under the repair area only.

(b) It is acceptable to change inspection procedures from Option 1 to Option 2 or from Option 2 to Option 1 if

you do as follows:

1. If the inspection procedure is being changed from Option 1 to Option 2, the first two Option 2 inspections

must be done within 500 flight cycle repeat intervals. The Option 2 inspections that follow must be

done within 1000 flight cycle repeat intervals.

2. If the inspection procedure is being changed from Option 2 to Option 1, the first Option 1 inspection

must be done within 1000 flight cycles after the Option 2 inspection. The Option 1 inspections that

follow must be done within 500 flight cycle repeat intervals.

(c) Magneto Optical Imaging (MOI) and C-Scan NDI inspection options cannot be used within 4 inches of an

existing repair doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy

Current (MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used.

Group 2:

Table 6: Post Repair - Critical Fastener Row Inspection

Repeat Interval

(Not to Exceed)

Compliance Time

(Whichever Occurs Later)

Condition Action

Within 60,000 flight cycles -

from the time the repair was

installed.

Do a Non Destructive inspection (NDI)

of the skin at the critical row of fasteners in the repair for cracks in accordance with Accomplishment Instructions, Paragraph 3.B., Part 8.

Airplanes with a repair

installed in accordance

with this service bulletin.

6,000 flight cycles.Within 6,000 flight cycles after the last NDI.Do a repeat NDI of the skin at the

critical row of fasteners in the repair

for cracks in accordance with Accomplishment Instructions, Paragraph

3.B., Part 8.

No crack found.

Contact Boeing for repair instructions Before further flight. -

in accordance with Accomplishment

Instructions, Paragraph 3.B., Part 8

and do the repair.

Any crack found.

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BOEING SERVICE BULLETIN 737-53A1293
F. Approval

This service bulletin was examined by the Federal Aviation Administration (FAA). The changes specified

in this service bulletin comply with the applicable regulations and are FAA approved, as well as European

Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved

airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on

the airplane in its original Boeing delivery configuration or as modified by other approved Boeing

changes.

If an airplane has a non-Boeing modification or repair that affects a component or system also affected

by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval

before incorporating this service bulletin.

In addition the Manager of the FAA Seattle Aircraft Certification Office approves the inspection methods

and corrective actions in Tables 1, 2, 3 and 5 under Paragraph 1.E., Compliance of this service bulletin,

as an alternative method of compliance to the inspection methods and corrective actions specified in

Table 1 and 2, under Paragraph 1.E., Compliance of the Original Issue of this service bulletin, dated

August 13, 2008, required by paragraphs (f) and (g) of AD 2008-19-03. The compliance times remain

unchanged from those defined in AD 2008-19-03. When this service bulletin specifies contacting Boeing

for repair instructions, the repair instructions must be approved by the FAA in accordance with paragraph

(h) of AD 2008-19-03. All provisions of AD 2008-19-03 that are not specifically referenced in this

paragraph remain fully applicable and must be complied with accordingly.

G. Manpower

The table below shows an estimate of the task hours necessary to do this inspection for each airplane.

This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator

task hour data if necessary. The estimate does not include lost time. These are some examples of lost

time:

• Time to adjust to the workplace

• Time to schedule the work

• Time to inspect the work

• Time to cure the materials

• Time to make the parts

• Time to find the tools.

Group 1:

Table 1 - Skin Panel Inspection and Repair.

Number of Per- Task Hours Elapsed Hours

sons

Task

Get Access 1 0.25 0.25

FIGURE 2 2 5.50 2.75

or

FIGURE 7

FIGURE 5 - - (a)

FIGURE 6 - - (a)

or

FIGURE 8

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BOEING SERVICE BULLETIN 737-53A1293
Group 1:

Table 1 - Skin Panel Inspection and Repair.

Number of Per- Task Hours Elapsed Hours

sons

Task

Inspection 2 8.50 (b) 4.25 (b)

Close Access 1 0.25 0.25

TOTAL FOR EACH AIRPLANE 14.50 5.75

(a) The time to make any repair is not included. More time is required for repairs

if any damage is found.

(b) Includes time to access interior and inspect interior and exterior of one typical

repair location for the critical fastener row.

Group 2:

Table 2 - Skin Panel Inspection and Repair.

Number of Per- Task Hours Elapsed Hours

sons

Task

Get Access 1 0.25 0.25

FIGURE 4 2 6.00 3.00

or

FIGURE 9

FIGURE 10 - - (a)

FIGURE 11 - - (a)

FIGURE 12 2 3.00 1.50 (b)

Close Access 1 0.25 0.25

TOTAL FOR EACH AIRPLANE 9.50 5.00

(a) The time to make any repair is not included. More time is required for repairs

if any damage is found.

(b) Includes time to access interior and inspect interior and exterior of one typical

repair location for the critical fastener row.

H. Weight and Balance Changes

All airplanes:

1. Calculate the change in weight for each repair installation as follows:

a. Calculate the gross area of each repair doubler in square inches (Length x Width).

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BOEING SERVICE BULLETIN 737-53A1293
Example for FIGURE 6: Length = approximately 20 inches and Width = approximately 12

inches. Area = 240 square inches. (Calculation ignores the curvature of the fuselage, holes

and rounding of corners).

b. To calculate the weight for each repair doubler installed, including fasteners, paint and sealant,

multiply the repair doubler area (from step 1.a) by 0.006 lb per sq in.

Example for FIGURE 6: Change in Weight = 240 x 0.006 = 1.4 pounds rounded to nearest

1/10 pound.

2. Calculate the change in moment for each repair installation as follows:

a. Record the station of the geometric center of each repair doubler.

Example for FIGURE 6: By inspection, station = 435.

b. To calculate the change in moment for each repair doubler, use the formula for each model

as follows:

– For Model 737-300: change in weight from step 1.b. x (station from step 2.a. - 80) =

Change in Moment.

– For Model 737-400: change in weight from step 1.b. x (station from step 2.a. - 152) =

Change in Moment.

– For Model 737-500: change in weight from step 1.b. x (station from step 2.a. - 26) =

Change in Moment.

Example for FIGURE 6, Model 737-300: 1.4 x (435 - 80) = 500 Pound-Inches rounded to

nearest 10 pound-inch.

3. If multiple repair doublers are installed, treat each one individually and then sum the weights and

moments.

I. Electrical Load Data

Not changed.

J. References

1. Existing Data

a. Boeing Service Letter 737-SL-51-042

b. Boeing Service Related Problem (SRP) 737-SRP-53-0334

c. Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2008-19-03

d. Standard Overhaul Practices Manual (SOPM) 20-43-03, 20-44-03 , 20-44-04

e. 737 Non-Destructive Testing (NDT) Manual Part 4, 53-30-07, Part 6, 51-00-00, Figure 16,

Part 6, 51-00-00 Figure 23 , Part 6, 51-00-00 Figure 4, Part 6, 53-30-00, Figure 5, Part 6,

53-30-00, Figure 6, Part 6, 53-30-09, Part 6, 53-30-18, Part 6, 53-30-19, Part 6, 53-30-25

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BOEING SERVICE BULLETIN 737-53A1293
f. 737-300/400/500 Aircraft Maintenance Manual (AMM) 25-21-39, 25-21-45, 25-21-46, 25-22-00,

25-23-61, 25-24-31, 34-53-11, 51-21-00

g. 737-300 Structural Repair Manual (SRM) 51-10-01, 51-20-01 , 51-20-05, 51-30-01, 51-40,

51-40-08

h. 737-400 Structural Repair Manual (SRM) 51-10-01, 51-20-01 , 51-20-05, 51-30-01, 51-40,

51-40-08

i. 737-500 Structural Repair Manual (SRM) 51-10-01, 51-20-01 , 51-20-05, 51-30-01, 51-40,

51-40-08

j. Multi-Operator Message (MOM) MOM-MOM-09-0807-01B (R1)

k. Airplane Flight Manual Appendix 53

l. Repair Assessment Guidelines - Model 737-100 to -500 Document Number D6-38669 Rev

C

m. Service Bulletin Index Document D6-19567 Part 3

2. Data supplied with this Service Bulletin

None.

3. Installation Drawings Used in the Preparation of this Service Bulletin

Drawing Number Title

65-45765 SKIN PANEL INSTALLATION - S-10L TO S-10R STA 360 - STA 540

65C35765 SKIN INSTALLATION - S-10L TO S-10R, STA 360 TO STA 540

These drawings were used to prepare this service bulletin. These drawings are not necessary to

make the specified changes, and are not supplied with this service bulletin. These drawings may

not be applicable to all airplane configurations or operators.

K. Publications Affected

1. Publications:

None.

2. Damage Tolerance Based Structural Inspections:

Boeing has evaluated the repairs and/or changes in this service bulletin for effects on Fatigue

Critical Structure (FCS) and for changes to Damage Tolerance Inspections (DTI) required in the

Maintenance Program. This service bulletin affects FCS. DTI requirements for the structure affected

are contained in Paragraph 1.E., Compliance of this service bulletin.

L. Interchangeability and Intermixability of Parts

Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.

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BOEING SERVICE BULLETIN 737-53A1293
2. MATERIAL INFORMATION

A. Material - Price and Availability

The operator can supply the parts and materials shown in Paragraph 2.C., Parts Necessary for Each

Airplane . As an alternative, operators can purchase the parts from Boeing Spares. This service bulletin

does not show the Boeing price and supply data.

B. Industry Support Information

Boeing warranty remedies are not available for the inspection,and repair procedures given in this

service bulletin.

C. Parts Necessary For Each Airplane

1. Kits/Parts

None.

2. Parts and Materials Supplied by the Operator

Group 1:

Table 1

Part Number / QTY Name Notes

Specification

BACR15BB5D - RIVET (a) (b) (c) (d)

BACR15BB6AD - RIVET (a) (b) (c) (d)

BACR15BB6D - RIVET (a) (b) (c) (d)

BACR15CE5D - RIVET (a) (b) (c) (d)

ORGANIC CORROSION INHIBIT- (b) (c)

ING COMPOUND

BMS 3-23 TYPE II -

BMS 5-95 - SEALANT (b) (c)

2024-T3 CLAD - REPAIR DOUBLER MATERIAL (b) (c)

Sheet X 0.050

thick

TEAR STRAP DOUBLER MATERI- (b) (c)

AL

2024-T3 CLAD -

Sheet X 0.040

thick

(a) Refer to 737-300/-400/-500 Structural Repair Manual Chapter 51 for alternate fasteners.

(b) Quantities to be determined by the size of the repair.

(c) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS)

for supplier data.

(d) Fastener grip length to be determined on assembly.

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Group 2:

Table 2

Part Number / QTY Name Notes

Specification

2024-T3 Clad Sheet x 0.050 inches (a)

thick.

40

inches

x 30

inches

AMS QQ-A-250/5

2024-T3 Clad Sheet x 0.040 inches (b)

thick.

24

inches

x 5

inches

AMS QQ-A-250/5

BACR15BB6D5C 16 Rivet (c) (d)

BACR15BB6D6C 32 Rivet (c) (d)

BACR15GF5D4 124 Rivet (c) (d)

BACR15GF5D5 166 Rivet (c) (d)

BACR15GF5D6 51 Rivet (c) (d)

BACR15BB6AD5C 68 Rivet (c) (d)

2 Chemical Conversion Coating (e)

ounces

TYPE 2, CLASS A

3 Primer (f)

ounces

BMS 10-79, TYPE

III

5 Sealant (f)

ounces

BMS 5-95, TYPE I,

CLASS B-1/2 OR

B-2

Organic Corrosion Inhibiting Com- (f)

pound

2

ounces

BMS 3-23, TYPE II

(a) Use to make the external repair doubler in accordance with FIGURE 11.

(b) Use to make tear strap doublers in accordance with FIGURE 11.

(c) Refer to 737-300/-400/-500 Structural Repair Manual Chapter 51 for alternate fasteners.

(d) Fastener grip length to be determined on assembly.

(e) Refer to SOPM 20-43-03 for material sources.

(f) Refer to the Qualified Products List at the end of the Boeing Material Specification (BMS)

for supplier data.

3. Parts Modified and Reidentified

None.

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4. Parts Removed and Not Replaced

None.

D. Parts Necessary to Change Spares

None.

E. Special Tooling - Price and Availability

None.

F. Special Tooling Necessary to do this Service Bulletin

No special tools or equipment are necessary to do the change in this service bulletin. But, maintenance

and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine

operator tool supply to make sure all necessary tools are available.

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BLANK PAGE
3. ACCOMPLISHMENT INSTRUCTIONS

A. GENERAL INFORMATION

CAUTION: KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL

PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL,

METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE

DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR

OTHER ELECTRICAL DAMAGE.

NOTE: 1. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for

definition of the acronyms.

2. Obey all of the warnings and cautions given in the specified manual sections.

3. Unless shown differently, these dimensions and tolerances are used:

– Linear dimensions are in inches

– Tolerance on linear dimensions, other than rivet and bolt edge margins, is plus

or minus 0.03 inch

– Tolerance on rivet and bolt edge margin is plus or minus 0.05 inch

– Angular tolerance is plus or minus 2 degrees

– Hole dimensions for standard solid rivets are in 737-300/-400/-500 SRM Chapter

51.

4. Maintain a 2D minimum edge margin on all parts unless otherwise stated.

5. All machined surfaces must have a finish of 125 micro-inch Ra or better. Refer to

Figure 1 of 737-300 SRM 51-10-01, 737-400 SRM 51-10-01, 737-500 SRM 51-10-01

as an accepted procedure.

6. Clean repair parts and mating surfaces. Refer to 737-300 SRM 51-20-05, 737-400

SRM 51-20-05, and 737-500 SRM 51-20-05 as an accepted procedure.

7. For fastener installation refer to 737-300 SRM 51-40, 737-400 SRM 51-40 or 737-500

SRM 51-40 as an accepted procedure.

8. Use the approved fastener and process material substitutions in accordance with

SRM Chapter 51.

9. If the length of any fastener specified in this service bulletin does not meet installation

standards given in SRM Chapter 51, then a fastener of the same specification, or

an approved substitute, with a length which meets the installation standards given

in SRM Chapter 51 may be used. In addition, washers may be installed for fastener

grip length in accordance with SRM Chapter 51.

10. Boeing Service Letter 737-SL-51-042, Damage Reporting and Repair Plan/Design

Guidelines, is an acceptable procedure to request information from Boeing for

additional structural repair instructions. The Service Letter describes what information

must be provided to Boeing before a structural repair can be provided.

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11. A Detailed Inspection is defined as: An intensive examination of a specific item,

installation, or assembly to detect damage, failure, or irregularity. Available lighting

is normally supplemented with a direct source of good lighting at an intensity deemed

appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be

necessary. Surface cleaning and elaborate access procedures may be required.

12. These work instructions refer to procedures included in other Boeing documents.

When the words "refer to" are used and the operator has an accepted alternative

procedure, the accepted alternative procedure can be used. When the words "in

accordance with" are included in the instruction, the procedure in the Boeing document

must be used.

13. If chem-mill step crack damage is found and the damage is within the SB damage

limits and the airplane is above the SB threshold, Boeing would still like to obtain the

information relative to the damage in order to develop more refined inspection

requirements. Report crack damage in accordance with APPENDIX B.

14. If it is necessary to remove more parts for access, you can remove those parts. If

you can get access without removing identified parts, it is not necessary to remove

all of the identified parts. Jacking and shoring limitations must be observed.

15. Where the work instructions include installation of a kept part, a new or serviceable

part with the same part number can be installed as an alternative to the kept part.

The removed part can be discarded if a new or serviceable part is installed.

B. WORK INSTRUCTIONS

Group 1:

PART 1 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R,

STA 400 - STA 460

1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA

400 and STA 460.

2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at

stringers S-1 and S-2R, between STA 400 and STA 460 in accordance with FIGURE 2.

3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for

cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400

and STA 460 in accordance with FIGURE 2.

a. Option 1: Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or

C-Scan.

b. Option 2: Ultrasonic Phased Array (UTPA).

4. If no crack is found, do repeat external DI and NDI in accordance with PART 1 at intervals in

accordance with Paragraph 1.E., Compliance.

5. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair

instructions in accordance with APPENDIX A, do the repair and do the inspection of the fuselage

skin not covered by a repair in accordance with PART 3 at intervals in accordance with Paragraph

1.E., Compliance.

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a. Crack(s) found before 35,000 total flight cycles.

b. Crack(s) found in four or more tear strap bays.

c. Crack(s) found longer than 5 inches.

d. Crack(s) found are not contained within the skin cut-out shown in FIGURE 5.

6. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance

with PART 2 and do the inspection of the fuselage skin not covered by a repair in accordance with

PART 3 at intervals in accordance with Paragraph 1.E., Compliance.

a. Crack(s) found at or after 35,000 total flight cycles.

b. Crack(s) found in three or fewer tear strap bays.

c. Crack(s) found 5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out shown in FIGURE 5.

7. Put the airplane back to a serviceable condition.

Group 1:

PART 2 - SKIN REPAIR

1. In the passenger cabin, remove and keep the equipment listed in the table below to access the

area of repair. Refer to the listed Aircraft Maintenance Manual (AMM) as an accepted procedure.

Equipment AMM Chapter/Section/Subject

Passenger Seats 737-300/400/500 AMM 25-22-00

Sidewall Lining 737-300/400/500 AMM 25-21-46

Sidewall insulation 737-300/400/500 AMM 25-21-39

Overhead Stowage Bins 737-300/400/500 AMM 25-24-31

Passenger Service Units 737-300/400/500 AMM 25-23-61

Ceiling Panels 737-300/400/500 AMM 25-21-45

2. Remove and keep ATC antenna if required, refer to 737-300/400/500 AMM 34-53-11 as an accepted

procedure.

3. Remove the crack in accordance with FIGURE 5 .

4. Make and install the repair doubler and tear strap doublers in accordance with figure listed below:

Airplanes Series Figure

737-300, 737-400 FIGURE 6

737-500 FIGURE 8

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5. If ATC antenna was removed to do the repair, install kept ATC antenna on top of repair doubler.

Refer to 737-300/400/500 AMM 34-53-11 as an accepted procedure.

6. Install kept equipment in the passenger cabin that was removed for access.

7. Accomplish the Part 4 - Post Repair inspections at the times specified in Table 4 of Paragraph

1.E., Compliance.

8. Put airplane back in a serviceable condition.

Group 1:

PART 3 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS

S-1 AND S-2R, STA 400 - STA 460

1. Get external access to skin repair area at stringers S-1 and S-2R, between STA 400 and STA

460.

2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at

stringers S-1 and S-2R, between STA 400 and STA 460 not covered by a repair in accordance

with FIGURE 7.

3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for

cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400

and STA 460 not covered by a repair in accordance with FIGURE 7.

a. Option 1: Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or

C-Scan.

b. Option 2: Ultrasonic Phased Array (UTPA).

4. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair

instructions in accordance with APPENDIX A and do the repair:

a. Crack(s) found before 35,000 total flight cycles.

b. Crack(s) found in four or more tear strap bays.

c. Crack(s) found longer than 5 inches.

d. Crack(s) found are not contained within the skin cut-out shown in FIGURE 5.

5. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance

with PART 2.

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a. Crack(s) found at or after 35,000 total flight cycles.

b. Crack(s) found in three or fewer tear strap bays.

c. Crack(s) found 5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out shown in FIGURE 5.

6. Repeat external DI and NDI in accordance with PART 3 at intervals in accordance with Paragraph

1.E., Compliance.

7. Put the airplane back to a serviceable condition.

Group 1:

PART 4 - POST REPAIR - CRITICAL FASTENER ROW INSPECTION

1. Get access to skin repair at stringers S-1 and S-2R, between STA 400 and STA 460.

2. Do Non Destructive Inspection (NDI) or Detailed Inspection (DI) of the skin at the critical row of

fasteners in the repair for cracks in accordance with Repair Assessment Guidelines D6-38669

Revision C Figure 2-9.

NOTE: The NDI procedures given in the Options column of Figure 2-9 in D6-38669 Revision C

should be changed as follows:

1. Use 737 NDT Part 6, 53-30-00, Figure 6 in place of 53-30-3 Figure 6.

2. Use 737 NDT Part 6, 53-30-00, Figure 5 in place of 53-30-3 Figure 5.

3. If crack is found contact Boeing for repair instructions and do the repair.

4. Repeat post repair inspection in accordance with PART 4 at intervals in accordance with Paragraph

1.E., Compliance.

5. Put the airplane back to a serviceable condition.

Group 2:

PART 5 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R,

STA 400 - STA 460

1. Get external access to the area around the ATC antenna at stringers S-1 and S-2R, between STA

400 and STA 460.

2. Do external Detail Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at

stringers S-1 and S-2R, between STA 400 and STA 460 in accordance with FIGURE 4.

3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for

cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400

and STA 460 in accordance with FIGURE 4.

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a. Option 1: Medium Frequency Eddy Current (MFEC), or Magneto Optical Imaging (MOI) or

C-Scan

b. Option 2: Ultrasonic Phased Array (UTPA).

4. If no crack is found, repeat external DI and NDI in accordance with PART 5 at intervals in

accordance with Paragraph 1.E., Compliance.

5. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair

instructions in accordance with APPENDIX A, do the repair and do the inspection of the fuselage

skin not covered by a repair in accordance with PART 6 at intervals in accordance with Paragraph

1.E., Compliance.

a. Crack(s) found before 33,000 total flight cycles.

b. Crack(s) found between STA 400 and STA 420.

c. Crack(s) found between STA 440 and STA 460.

d. Crack(s) found longer than 12.5 inches.

e. Crack(s) found are not contained within the skin cut-out shown in FIGURE 10.

6. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance

with PART 7 and do the inspection of the fuselage skin not covered by a repair in accordance with

PART 6 at intervals in accordance with Paragraph 1.E., Compliance.

a. Crack(s) found at or after 33,000 total flight cycles.

b. Crack(s) found between STA 420 and STA 440.

c. Crack(s) found 12.5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out shown in FIGURE 10.

7. Put the airplane back to a serviceable condition.

Group 2:

PART 6 - EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS

S-1 AND S-2R, STA 400 - STA 460

1. Get external access to skin repair area at stringers S-1 and S-2R, between STA 400 and STA

460.

2. Do external Detailed Inspection (DI) for cracks in the fuselage skin along the chem-mill steps at

stringers S-1 and S-2R, between STA 400 and STA 460 not covered by a repair in accordance

with FIGURE 9.

3. Do external Non Destructive Inspection (NDI) using one of the following options/procedures for

cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between STA 400

and STA 460 not covered by a repair in accordance with FIGURE 9.

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a. Option 1: Medium Frequency Eddy Current (MFEC) or Magneto Optical Imaging (MOI) or

C-Scan.

b. Option 2: Ultrasonic Phased Array (UTPA).

4. If any of the following is found as a result of the external DI and NDI, contact Boeing for repair

instructions in accordance with APPENDIX A, and do the repair.

a. Crack(s) found before 33,000 total flight cycles.

b. Crack(s) found between STA 400 and STA 420.

c. Crack(s) found between STA 440 and STA 460.

d. Crack(s) found longer than 12.5 inches.

e. Crack(s) found are not contained within the skin cut-out shown in FIGURE 10.

5. If all of the following are found as result of the external DI and NDI, do the skin repair in accordance

with PART 7.

a. Crack(s) found at or after 33,000 total flight cycles.

b. Crack(s) found between STA 420 and STA 440.

c. Crack(s) found 12.5 inches or shorter.

d. Crack(s) found are contained within the skin cut-out shown in FIGURE 10.

6. Repeat external DI and NDI in accordance with PART 6 at intervals in accordance with Paragraph

1.E., Compliance.

7. Put the airplane back to a serviceable condition.

Group 2:

PART 7 - SKIN REPAIR

1. In the passenger cabin, remove and keep the equipment listed in the table below to access the

area of repair. Refer to the listed Aircraft Maintenance Manual (AMM) as an accepted procedure.

Equipment AMM Chapter/Section/Subject

Passenger Seats 737-300/400/500 AMM 25-22-00

Sidewall Lining 737-300/400/500 AMM 25-21-46

Sidewall insulation 737-300/400/500 AMM 25-21-39

Overhead Stowage Bins 737-300/400/500 AMM 25-24-31

Passenger Service Units 737-300/400/500 AMM 25-23-61

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Equipment AMM Chapter/Section/Subject

Ceiling Panels 737-300/400/500 AMM 25-21-45

2. Remove and keep the ATC antenna, refer to 737-300/400/500 AMM 34-53-11 as an accepted

procedure.

3. Remove the crack in accordance with FIGURE 10.

4. Make and install the repair doubler and tear strap doublers in accordance with FIGURE 11.

5. Install the kept ATC antenna on top of the repair doubler. Refer to 737-300/400/500 AMM 34-53-11

as an accepted procedure.

NOTE: Longer ATC antenna mounting screws may be necessary as a result of installing the

repair doubler.

6. Install kept equipment in the passenger cabin that was removed for access.

7. Accomplish the Part 8 - Post Repair inspections at the times specified in Table 6 of Paragraph

1.E., Compliance.

8. Put airplane back in a serviceable condition.

Group 2:

PART 8 - POST REPAIR - CRITICAL FASTENER ROW INSPECTION

1. Get external access to the skin repair at stringers S-1 and S-2R, between STA 400 and STA 460.

2. Do an external Non Destructive Inspection (NDI) in accordance with FIGURE 12 for cracks in the

fuselage skin, at the critical row of fasteners in the repair.

a. If any crack is found contact Boeing for repair instructions and do the repair.

3. Repeat post repair inspection in accordance with PART 8 at intervals in accordance with Paragraph

1.E., Compliance.

4. Put the airplane back to a serviceable condition.

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This Figure applies only to: Group 1.

FIGURE 1: THIS FIGURE DELETED AT REVISION 1

(SHEET 1 OF 1)

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BOEING SERVICE BULLETIN 737-53A1293
This Figure applies only to: Group 1.

FIGURE 2: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400

- STA 460

(SHEET 1 OF 2)

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BOEING SERVICE BULLETIN 737-53A1293
The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for one airplane.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Inspect SKIN - - (a)

2 Inspect SKIN - - Do the procedure listed in note (b) or (c) or (d) or (e).

(a) Do Detailed Inspection for cracks.

(b) Do Medium Frequency Eddy Current (MFEC) Inspection in accordance with 737 NDT Part 6, 53-30-09

or 737 NDT Part 6, 53-30-18 for cracks.

(c) Do Magneto Optical Imaging (MOI) Inspection in accordance with 737 NDT Part 6, 53-30-19 for cracks.

Magneto Optical Imaging (MOI) NDI inspection option cannot be used within 4 inches of an existing repair

doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current

(MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used (see note (b) or (e) ).

(d) Do C-Scan Inspection in accordance with 737 NDT Part 6, 53-30-25 for cracks. C-Scan NDI inspection

option cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing

repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA)

NDI inspection options must be used (see note (b) or (e) ).

(e) Do Ultrasonic Phased Array (UTPA) inspection in accordance with 737 NDT Part 4, 53-30-07 for cracks.

FIGURE 2: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400

- STA 460

(SHEET 2 OF 2)

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This Figure applies only to: Group 2.

FIGURE 3: THIS FIGURE DELETED AT REVISION 1

(SHEET 1 OF 1)

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This Figure applies only to: Group 2.

FIGURE 4: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400

- STA 460

(SHEET 1 OF 2)

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The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for one airplane.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Inspect SKIN - - (a)

2 Inspect SKIN - - Do the procedure listed in note (b) or (c) or (d) or (e).

(a) Do Detailed Inspection for cracks.

(b) Do Medium Frequency Eddy Current (MFEC) Inspection in accordance with 737 NDT Part 6, 53-30-09

or 737 NDT Part 6, 53-30-18 for cracks.

(c) Do Magneto Optical Imaging (MOI) Inspection in accordance with 737 NDT Part 6, 53-30-19 for cracks.

Magneto Optical Imaging (MOI) NDI inspection option cannot be used within 4 inches of an existing repair

doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current

(MFEC) or Ultra Sonic Phased Array (UTPA) NDI inspection options must be used (see note (b) or (e) ).

(d) Do C-Scan Inspection in accordance with 737 NDT Part 6, 53-30-25 for cracks. C-Scan NDI inspection

option cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing

repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultra Sonic Phased Array (UTPA)

NDI inspection options must be used (see note (b) or (e) ).

(e) Do Ultrasonic Phased Array (UTPA) inspection in accordance with 737 NDT Part 4, 53-30-07 for cracks.

FIGURE 4: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION - STRINGERS S-1 AND S-2R, STA 400

- STA 460

(SHEET 2 OF 2)

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This Figure applies only to: Group 1.

FIGURE 5: FUSELAGE SKIN - CRACK REMOVAL

(SHEET 1 OF 3)

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The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for each repair location.

CAUTION: WHEN REMOVING THE CRACK, MAKE SURE THE CUT-OUT IS COMMON TO THE SKIN

ONLY. TAKE CARE NOT TO DAMAGE OR CUT THE BONDED DOUBLER.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Cut SKIN - - (a) (b) (c)

2 Inspect SKIN - - (d)

ALODINE 1200S TYPE - (e)

2 CLASS A

CHEMICAL CONVERSION COATING3 Apply

BMS 10-79 TYPE 2 - (f)

(BMS 10-79 TYPE 3

optional)

Apply PRIMER

(a) Cut and remove damaged skin as shown. Maintain 0.5 inch radius on the skin cut-out.

(b) Maintain 2D minimum edge margin from all fastener holes.

(c) Maintain a minimum of 63 micro inch Ra or better surface roughness.

(d) Do a High Frequency Eddy Current inspection of the edge of the skin cut-out in accordance with 737 NDT

Part 6, 51-00-00 Figure 4 or 737 NDT Part 6, 51-00-00 Figure 23. If any crack is found, contact Boeing

for repair instructions and do the repair. If no cracks are found, remove an additional 0.040 inch of material at the inspected area as an insurance (area in bold at each end of the skin cut-out). Make sure there

is a smooth transition from the insurance cut area to the non-insurance cut area. Maintain a minimum of

63 micro inches Ra or better surface roughness.

FIGURE 5: FUSELAGE SKIN - CRACK REMOVAL

(SHEET 2 OF 3)

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STEP TASK NAME IDENTIFICATION QTY MORE DATA

(e) Apply to bare aluminium surfaces. Refer to SOPM 20-43-03 as an accepted procedure.

(f) Apply to bare aluminium surfaces. Refer to SOPM 20-44-04 as an accepted procedure.

FIGURE 5: FUSELAGE SKIN - CRACK REMOVAL

(SHEET 3 OF 3)

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BOEING SERVICE BULLETIN 737-53A1293
This Figure applies only to: Group 1.

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 1 OF 10)

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FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 2 OF 10)

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BOEING SERVICE BULLETIN 737-53A1293
The flag note letters shown below agree with the letters shown in the flag note symbols in the figure.

FLAG DESCRIPTION

NOTE

A Extend the doubler a minimum of four (4) fastener rows beyond all sides of the skin cut-out.

If the doubler will terminate within 3.00 inches of the skin cut-out for the ATC antenna, extend the

doubler beyond the antenna in all directions by two (2) additional fastener rows.

B

In the hoop direction, do not terminate the doubler common to the ATC antenna support structure.

Extend the doubler beyond the ATC antenna support structure by two (2) additional fasteners.

C

In the longitudinal direction, do not terminate the doubler at the edge of the ATC antenna support

structure. Extend the doubler beyond the ATC antenna support structure by one (1) additional fastener

row.

D

E Do not terminate the doubler within 0.5 inch of any chem-mill step.

The repair should extend a minimum of three (3) fastener rows beyond any longitudinal chem-mill

step that is covered by the repair.

F

The repair should extend a minimum of two (2) fastener rows beyond rows beyond any circumferential

chem-mill step that is covered by the repair.

G

H Make the doubler from 2024-T3 CLAD sheet, 0.050 inch thick.

Tear strap doublers are required at repair locations where skin pockets are located directly forward

and aft of the production tear strap.

I

J The tear strap doubler should have the same width as the production tear strap.

Stagger fasteners common to the 1.5 inch wide tear straps as shown in the figure. The staggered row

of fasteners counts as one (1) row of fasteners in the longitudinal direction.

K

Do not end the tear strap doubler on a stringer. If the end of the tear strap doubler is on a stringer,

extend the tear strap doubler beyond the stringer by one (1) additional fastener row.

L

If the tear strap doubler crosses a stringer, install tapered fillers on each side of the tear strap doubler

between the skin and the stringer. Make the tapered fillers from 2024-T3 CLAD sheet, 0.040 inch

thick, tapered to .010/.020 inch, maintaining a 50 to 1 minimum taper ratio.

M

N Make the tear strap doublers from 2024-T3 CLAD sheet, 0.040 inch thick.

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 3 OF 10)

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FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 4 OF 10)

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FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 5 OF 10)

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FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 6 OF 10)

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BOEING SERVICE BULLETIN 737-53A1293
CAUTION: WHEN DRILLING NEW FASTENER HOLES, USE CARE NOT TO DRILL NEAR EDGE OF THE

TEAR STRAP. TEAR STRAP FASTENERS SHOULD BE DRILLED FROM THE INNER FACE

OF THE PANEL.

The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for each repair location.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

Locate repair area in

accordance with

Flag Notes A

through K.

1 Locate REPAIR AREA - -

2 Remove FASTENER - - (g) (h) (i) (j)

Make in accordance

with foot notes (a)

(c) (d) (e) (f). Determine size of repair

doubler in accordance with Flag

Notes A through K.

3 Make REPAIR DOUBLER - -

Make in accordance

with foot notes (b)

(c) (f). Locate and

determine size of

tear strap doubler in

accordance with

Flag Notes I through

N.

TEAR STRAP DOU- - -

BLER

4 Make

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 7 OF 10)

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STEP TASK NAME IDENTIFICATION QTY MORE DATA

Apply to all bare surfaces of doublers.

Refer to 737-300

SRM 51-20-01 or

ALODINE 1200S TYPE -

2 CLASS A

CHEMICAL CONVERSION COATING5 Apply

737-400 SRM 51-

20-01 and

SOPM 20-44-03 as

an accepted procedure.

2 primer coats required. Apply to all

bare surfaces of

doublers. Refer to

737-300 SRM 51-

20-01 or

Apply PRIMER BMS 10-79 TYPE II -

737-400 SRM 51-

20-01 and

SOPM 20-44-04 as

an accepted procedure.

Make and install, refer to 737-300 SRM

51-40-08 or

COUNTERSINK RE- - -

PAIR WASHER

6 Install (New)

737-400 SRM 51-

40-08

as an accepted procedure.

Fay surface seal all

mating parts.

7 Apply SEALANT BMS 5-95 -

8 Install (New) REPAIR DOUBLER - -

TEAR STRAP DOU- - -

BLER

9 Install (New)

Apply a fillet seal

around edges of repair

10 Apply SEALANT BMS 5-95 -

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 8 OF 10)

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BOEING SERVICE BULLETIN 737-53A1293
STEP TASK NAME IDENTIFICATION QTY MORE DATA

Apply corrosion inhibiting compound to

internal surfaces of

repair after sealant

in area has cured.

Refer to 737-300

SRM 51-20-01 or

ORGANIC CORRO- BMS 3-23 TYPE II -

SION INHIBITING

COMPOUND

11 Apply

737-400 SRM 51-

20-01

as an accepted procedure.

Apply external finish

to match adjacent

structure. Refer to

737-300/400/500

AMM 51-21-00 as

an accepted procedure.

12 Apply EXTERNAL FINISH - -

(a) Use 2024-T3 CLAD sheet x 0.050 inch thick material.

(b) Use 2024-T3 CLAD sheet x 0.040 inch thick material.

(c) Refer to 737-300 SRM 51-30-01 or 737-400 SRM 51-30-01 as an accepted procedure.

(d) Pre-form or roll doubler to match the contour of the fuselage.

(e) Chamfer edges. Refer to 737-300 SRM 51-10-01 or 737-400 SRM 51-10-01 as an accepted procedure.

(f) Keep a 0.50 inch outside radius and 2.00 inch inside radius on all repair part corners.

(g) Remove existing fasteners common to the area to be repaired.

(h) Do an open hole High Frequency Eddy Current inspection of all the existing open holes in the skin in accordance with 737 NDT Part 6, 51-00-00, Figure 16 to make sure there is no crack. If crack is detected,

contact Boeing for repair instructions and do the repair.

(i) Make sure the area under the repair does not show signs of bond separation of the bonded doubler or

have corrosion. If bond separation or corrosion is found, contact Boeing for repair instructions and do the

repair.

(j) Make sure the underlying structure in the area of repair does not have corrosion or cracks. If corrosion

or cracks are found, contact Boeing for repair instructions and do the repair.

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 9 OF 10)

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BOEING SERVICE BULLETIN 737-53A1293
The codes shown below agree with the letter shown in the upper left corner of the fastener symbols in the figure.

A number in the lower right corner gives the grip length of the fastener. The QTY numbers shown below are the

number of fasteners necessary for this figure.

CODE NAME IDENTIFICATION QTY HOLE DIA MORE DATA

Install fastener at the

same time as antenna installation.

A - - - 0.218 - 0.229

B RIVET BACR15BB6AD - 0.191 - 0.202 (d) (e)

C RIVET BACR15BB6D - 0.191 -0.202 (d) (e)

D RIVET BACR15BB5D - 0.159 - 0.171 (c) (e)

(b) (c) (e) 100 degree

countersink on repair

doubler.

E RIVET BACR15CE5D - 0.159 - 0.165

F RIVET BACR15BB6D - 0.191 - 0.202 (a) (c) (e)

(a) Fastener holes may be oversized by 1/32 inch. Install BACR15ET7AD in place of BACR15BB6D fasteners

after hole is oversized by 1/32 inch.

(b) Fastener holes are not permitted to be oversized, if oversized is required contact Boeing for instructions.

(c) Install countersink washers between skin and external doubler. Refer to 737-300 SRM 51-40-08 or 737-

400 SRM 51-40-08 as an accepted procedure.

(d) At new fastener locations, maintain 5-6 diameter spacing and 2 diameter edge margin, unless otherwise

specified.

(e) Over drive rivets to a minimum 1.4 times the diameter.

FIGURE 6: 737-300,737-400 SERIES AIRPLANE - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 10 OF 10)

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BOEING SERVICE BULLETIN 737-53A1293
This Figure applies only to: Group 1.

FIGURE 7: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1

AND S-2R, STA 400 - STA 460

(SHEET 1 OF 2)

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BOEING SERVICE BULLETIN 737-53A1293
The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for each inspection.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Inspect SKIN - - (a) (f) (g)

(f) (g). Do the procedure listed in note

(b) or (c) or (d) or

(e).

2 Inspect SKIN - -

(a) Do Detail Inspection for cracks.

(b) Do Medium Frequency Eddy Current (MFEC) Inspection in accordance with 737 NDT Part 6, 53-30-09

or 737 NDT Part 6, 53-30-18 for cracks.

(c) Do Magneto Optical Imaging (MOI) Inspection in accordance with 737 NDT Part 6, 53-30-19 for cracks.

Magneto Optical Imaging (MOI) NDI inspection option cannot be used within 4 inches of an existing repair

doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current

(MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used (see note (b) or (e) ).

(d) Do C-Scan Inspection in accordance with 737 NDT Part 6, 53-30-25 for cracks. C-Scan NDI inspection

option cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing

repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA)

NDI inspection options must be used (see note (b) or (e) ).

(e) Do Ultrasonic Phased Array (UTPA) inspection in accordance with 737 NDT Part 4, 53-30-07 for cracks.

(f) For repair(s) done in accordance with this service bulletin, it is not required to inspect chem-mill steps

under external doublers.

(g) For other FAA approved repair(s) with external doubler that extends a minimum of three fasteners on

each side of the chem-mill, not required to inspect chem-mill steps under external doublers.

FIGURE 7: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1

AND S-2R, STA 400 - STA 460

(SHEET 2 OF 2)

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BOEING SERVICE BULLETIN 737-53A1293
This Figure applies only to: Group 1.

FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 1 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 2 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
The flag note letters shown below agree with the letters shown in the flag note symbols in the figure.

FLAG DESCRIPTION

NOTE

A Extend the doubler a minimum of four (4) fastener rows beyond all sides of the skin cut-out.

If the doubler will terminate within 3.00 inches of the skin cut-out for the ATC antenna, extend the

doubler beyond the antenna in all directions by two (2) additional fastener rows.

B

In the hoop direction, do not terminate the doubler common to the ATC antenna support structure.

Extend the doubler beyond the ATC antenna support structure by two (2) additional fasteners.

C

In the longitudinal direction, do not terminate the doubler at the edge of the ATC antenna support

structure. Extend the doubler beyond the ATC antenna support structure by one (1) additional fastener

row.

D

E Do not terminate the doubler within 0.5 inch of any chem-mill step.

The repair should extend a minimum of three (3) fastener rows beyond any longitudinal chem-mill

step that is covered by the repair.

F

The repair should extend a minimum of two (2) fastener rows beyond rows beyond any circumferential

chem-mill step that is covered by the repair.

G

H Make the doubler from 2024-T3 CLAD sheet, 0.050 inch thick.

Tear strap doublers are required at repair locations where skin pockets are located directly forward

and aft of the production tear strap. The tear strap doubler can be a different shape at the different

locations. Select the appropriate tear strap detail.

I

J The tear strap doubler should have the same width as the production tear strap.

Stagger fasteners common to the 1.5 inch wide tear straps as shown in the figure. The staggered row

of fasteners counts as one (1) row of fasteners in the longitudinal direction.

K

Do not end the tear strap doubler on a stringer. If the end of the tear strap doubler is on a stringer,

extend the tear strap doubler beyond the stringer by one (1) additional fastener row.

L

If the tear strap doubler crosses a stringer, install tapered fillers on each side of the tear strap doubler

between the skin and the stringer. Make the tapered fillers from 2024-T3 CLAD sheet, 0.040 inch

thick, tapered to .010/.020 inch, maintaining a 50 to 1 minimum taper ratio.

M

N Make the tear strap doublers from 2024-T3 CLAD sheet, 0.040 inch thick.

FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 3 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 4 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 5 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 6 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 7 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
CAUTION: WHEN DRILLING NEW FASTENER HOLES, USE CARE NOT TO DRILL NEAR EDGE OF THE

TEAR STRAP. TEAR STRAP FASTENERS SHOULD BE DRILLED FROM THE INNER FACE

OF THE PANEL.

The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for each repair location.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

Locate repair area in

accordance with

Flag Notes A

through K.

1 Locate REPAIR AREA - -

2 Remove FASTENER - - (g) (h) (i) (j)

Make in accordance

with foot notes (a)

(c) (d) (e) (f). Determine size of repair

doubler in accordance with Flag

Notes A through K.

3 Make REPAIR DOUBLER - -

Make in accordance

with foot notes (b)

(c) (f). Locate and

determine size of

tear strap doubler in

accordance with

Flag Notes I through

N.

TEAR STRAP DOU- - -

BLER

4 Make

Apply to all bare surfaces of doublers.

Refer to 737-500

SRM 51-20-01 and

SOPM 20-44-03 as

an accepted procedure.

ALODINE 1200S TYPE -

2 CLASS A

CHEMICAL CONVERSION COATING5 Apply

2 primer coats required. Apply to all

bare surfaces of

doublers. Refer to

737-500 SRM 51-

20-01 and SOPM

20-44-04 as an accepted procedure.

BMS 10-79 TYPE 2 -

(BMS 10-79 TYPE 3

optional)

Apply PRIMER

FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 8 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
STEP TASK NAME IDENTIFICATION QTY MORE DATA

Make and install, refer to 737-500 SRM

51-40-08 as an accepted procedure.

COUNTERSINK RE- - -

PAIR WASHER

6 Install (New)

Fay surface seal all

mating parts.

7 Apply SEALANT BMS 5-95 -

8 Install (New) REPAIR DOUBLER - -

TEAR STRAP DOU- - -

BLER

9 Install (New)

Apply a fillet seal

around edges of repair

10 Apply SEALANT BMS 5-95 -

Apply corrosion inhibiting compound to

internal surfaces of

repair after sealant

in area has cured.

Refer to 737-500

SRM 51-20-01 as an

accepted procedure.

ORGANIC CORRO- BMS 3-23 TYPE II -

SION INHIBITING

COMPOUND

11 Apply

Apply external finish

to match adjacent

structure. Refer to

737-300/400/500

AMM 51-21-00 as

an accepted procedure.

12 Apply EXTERNAL FINISH - -

(a) Use 2024-T3 CLAD sheet x 0.050 inch thick material.

(b) Use 2024-T3 CLAD sheet x 0.040 inch thick material.

(c) Refer to 737-500 SRM 51-30-01 as an accepted procedure.

(d) Pre-form or roll doubler to match the contour of the fuselage.

(e) Chamfer edges. Refer to 737-500 SRM 51-10-01 as an accepted procedure.

(f) Keep 0.50 inch outside radius and 2.00 inch inside radius on all repair part corners.

(g) Remove existing fasteners common to the area to be repaired.

(h) Do an open hole High Frequency Eddy Current inspection of all the existing open holes in the skin in accordance with 737 NDT Part 6, 51-00-00, Figure 16 to make sure there is no crack. If crack is detected,

contact Boeing for repair instructions and do the repair.

(i) Make sure the area under the repair does not show signs of bond separation of the bonded doubler or

have corrosion. If bond separation or corrosion is found, contact Boeing for repair instructions and do the

repair.

FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 9 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
STEP TASK NAME IDENTIFICATION QTY MORE DATA

(j) Make sure the underlying structure in the area of repair does not have corrosion or cracks. If corrosion

or cracks are found, contact Boeing for repair instructions and do the repair.

The codes shown below agree with the letter shown in the upper left corner of the fastener symbols in the figure.

A number in the lower right corner gives the grip length of the fastener. The QTY numbers shown below are the

number of fasteners necessary for this figure.

CODE NAME IDENTIFICATION QTY HOLE DIA MORE DATA

Install fastener at the

same time as antenna installation.

A - - - 0.218 - 0.229

B RIVET BACR15BB6AD - 0.191 - 0.202 (d) (e)

C RIVET BACR15BB6D - 0.191 -0.202 (d) (e)

D RIVET BACR15BB5D - 0.159 - 0.171 (c) (e)

(b) (c) (e) 100 degree

countersink on repair

doubler.

E RIVET BACR15CE5D - 0.159 - 0.165

F RIVET BACR15BB6D - 0.191 - 0.202 (a) (c) (e)

(a) Fastener holes may be oversized by 1/32 inch. Install BACR15ET7AD in place of BACR15BB6D fasteners

after hole is oversized by 1/32 inch.

(b) Fastener holes are not permitted to be oversized, if oversized is required contact Boeing for instructions.

(c) Install countersink washers between skin and external doubler. Refer to 737-300 SRM 51-40-08 or 737-

400 SRM 51-40-08 as an accepted procedure.

(d) At new fastener locations, maintain 5-6 diameter spacing and 2 diameter edge margin, unless otherwise

specified.

FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 10 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
CODE NAME IDENTIFICATION QTY HOLE DIA MORE DATA

(e) Over drive rivets to a minimum 1.4 times the diameter.

FIGURE 8: 737-500 SERIES AIRPLANES - REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 11 OF 11)

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BOEING SERVICE BULLETIN 737-53A1293
This Figure applies only to: Group 2.

FIGURE 9: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1

AND S-2R, STA 400 - STA 460

(SHEET 1 OF 2)

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BOEING SERVICE BULLETIN 737-53A1293
The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for each inspection.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Inspect SKIN - - (a) (f) (g)

(f) (g). Do the procedure listed in note

(b) or (c) or (d) or

(e).

2 Inspect SKIN - -

(a) Do Detail Inspection for cracks.

(b) Do Medium Frequency Eddy Current (MFEC) Inspection in accordance with 737 NDT Part 6, 53-30-09

or 737 NDT Part 6, 53-30-18 for cracks.

(c) Do Magneto Optical Imaging (MOI) Inspection in accordance with 737 NDT Part 6, 53-30-19 for cracks.

Magneto Optical Imaging (MOI) NDI inspection option cannot be used within 4 inches of an existing repair

doubler edge. Within 4 inches of an existing repair doubler edge, the Medium Frequency Eddy Current

(MFEC) or Ultrasonic Phased Array (UTPA) NDI inspection options must be used (see note (b) or (e) ).

(d) Do C-Scan Inspection in accordance with 737 NDT Part 6, 53-30-25 for cracks. C-Scan NDI inspection

option cannot be used within 4 inches of an existing repair doubler edge. Within 4 inches of an existing

repair doubler edge, the Medium Frequency Eddy Current (MFEC) or Ultrasonic Phased Array (UTPA)

NDI inspection options must be used (see note (b) or (e) ).

(e) Do Ultrasonic Phased Array (UTPA) inspection in accordance with 737 NDT Part 4, 53-30-07 for cracks.

(f) For repair(s) done in accordance with this service bulletin, it is not required to inspect chem-mill steps

under external doublers.

(g) For other FAA approved repair(s) with external doubler that extends a minimum of three fasteners on

each side of the chem-mill, it is not required to inspect chem-mill steps under external doublers.

FIGURE 9: EXTERNAL FUSELAGE SKIN CHEM-MILL INSPECTION AFTER REPAIR - STRINGERS S-1

AND S-2R, STA 400 - STA 460

(SHEET 2 OF 2)

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This Figure applies only to: Group 2.

FIGURE 10: FUSELAGE SKIN - CRACK REMOVAL

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BOEING SERVICE BULLETIN 737-53A1293
The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for one airplane.

CAUTION: WHEN REMOVING THE CRACK, MAKE SURE THE CUT-OUT IS COMMON TO THE SKIN

ONLY. TAKE CARE NOT TO DAMAGE OR CUT THE BONDED DOUBLER.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Cut SKIN - - (a) (b) (c)

2 Inspect SKIN - - (d)

ALODINE 1200S TYPE - (e)

2 CLASS A

CHEMICAL CONVERSION COATING3 Apply

Apply PRIMER BMS 10-79, TYPE III - (f)

(a) Cut and remove damaged skin as shown. Maintain 0.5 inch radius on the skin cut-outs. The skin must

be cut out at both S-1 and S-2R locations as shown, even if the skin is only cracked at one location.

FIGURE 10: FUSELAGE SKIN - CRACK REMOVAL

(SHEET 2 OF 3)

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STEP TASK NAME IDENTIFICATION QTY MORE DATA

(b) Maintain 2D minimum edge margin from all fastener holes.

(c) Maintain a minimum of 63 micro inch Ra or better surface roughness.

(d) Do a High Frequency Eddy Current inspection of the edge of the skin cut-out in accordance with 737 NDT

Part 6, 51-00-00 Figure 4 or 737 NDT Part 6, 51-00-00 Figure 23. If any crack is found, contact Boeing

for repair instructions and do the repair. If no cracks are found, remove an additional 0.040 inch of material at the inspected area as an insurance (area in bold at each end of the skin cut-out). Make sure there

is a smooth transition from the insurance cut area to the non-insurance cut area. Maintain a minimum of

63 micro inches Ra or better surface roughness.

(e) Apply to bare aluminium surfaces. Refer to SOPM 20-43-03 as an accepted procedure.

(f) Apply to chemical conversion coated surfaces. Refer to SOPM 20-41-02 as an accepted procedure.

FIGURE 10: FUSELAGE SKIN - CRACK REMOVAL

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This Figure applies only to: Group 2.

FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 1 OF 6)

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FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 2 OF 6)

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FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION

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BOEING SERVICE BULLETIN 737-53A1293
CAUTION: WHEN DRILLING NEW FASTENER HOLES, USE CARE NOT TO DRILL NEAR EDGE OF THE

TEAR STRAP. TEAR STRAP FASTENERS SHOULD BE DRILLED FROM THE INNER FACE

OF THE PANEL.

The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for one airplane.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Remove FASTENER - - (a) (b) (c)

Make in accordance

with foot notes (d) (f)

(g) (h) (i) (j).

2 Make REPAIR DOUBLER - 1

Make in accordance

with foot notes (e) (f)

(g) (j).

TEAR STRAP DOU- - 4

BLER

3 Make

ALODINE 1200S TYPE - To all repair parts (k)

2 CLASS A

CHEMICAL CONVERSION COATING4 Apply

Apply PRIMER BMS 10-79, TYPE III - To all repair parts (l)

COUNTERSINK RE- - - (m)

PAIR WASHER

5 Install (New)

Fay surface seal all

mating parts. (n)

6 Apply SEALANT BMS 5-95 -

7 Install (New) REPAIR DOUBLER - 1 See fastener table.

TEAR STRAP DOU- - 4 See fastener table.

BLER

8 Install (New)

Apply a fillet seal

around edges of repair parts. (n)

9 Apply SEALANT BMS 5-95 -

ORGANIC CORRO- BMS 3-23 TYPE II - (o)

SION INHIBITING

COMPOUND

10 Apply

11 Apply EXTERNAL FINISH - - (p)

(a) Remove existing fasteners common to the area to be repaired.

(b) Do an open hole High Frequency Eddy Current inspection of all the existing open holes in the skin in accordance with 737 NDT Part 6, 51-00-00, Figure 16 for cracks. If crack is detected, contact Boeing for

repair instructions and do the repair.

(c) Do an internal detailed inspection of the skin in the area of the repair for corrosion or disbonded doublers.

If corrosion or disbonded doubler is found, contact Boeing for repair instructions and do the repair.

(d) Size the repair doubler as shown. Make from 2024-T3 CLAD sheet (AMS QQ-A-250/5) x 0.050 inch thick

material. Refer to the fastener table for hole sizes. Break all sharp edges. Maintain a minimum of 125

micro inches Ra surface finish.

FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION

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BOEING SERVICE BULLETIN 737-53A1293
STEP TASK NAME IDENTIFICATION QTY MORE DATA

(e) Size the tear strap doublers as shown. Make from 2024-T3 CLAD sheet (AMS QQ-A-250/5) x 0.040 inch

thick material. Refer to the fastener table for hole sizes. Break all sharp edges. Maintain a minimum of

125 micro inches Ra surface finish.

(f) Refer to 737-300 SRM 51-30-01 or 737-400 SRM 51-30-01 or 737-500 SRM 51-30-01 as an accepted

procedure.

(g) Where fastener spacing is not shown, maintain a fastener spacing of 5D-6D, based on the largest size

of adjacent fasteners. Maintain a minimum of 2D edge margin at all fastener locations. Make sure that

the fasteners will not ride the radius of the chem-milled pockets. Make sure the fastener row above the

chem-milled step has a 2D minimum distance from the edge of the step.

(h) Pre-form or roll doubler to match the contour of the fuselage.

(i) Chamfer edges. Refer to 737-300 SRM 51-10-01 or 737-400 SRM 51-10-01 or 737-500 SRM 51-10-01

as an accepted procedure.

(j) Keep a 0.50 inch outside radius and 2.00 inch inside radius on all repair part corners.

(k) Apply to bare aluminium surfaces. Refer to SOPM 20-43-03 as an accepted procedure.

(l) Apply to chemical conversion coated surfaces. Refer to SOPM 20-41-02 as an accepted procedure.

(m) Make the repair washers in accordance with 737-300 SRM 51-40-08 or 737-400 SRM 51-40-08 or 737-

500 SRM 51-40-08. Install in existing countersink holes underneath the external doubler. Install wet with

BMS 5-95, TYPE 1, CLASS B-1/2 or B-2 sealant.

(n) Refer to SOPM 20-50-19 as an accepted procedure.

(o) Apply to all of the internal repair parts and surrounding skin and structure. Refer to 737-300 SRM 51-20-

01 or 737-400 SRM 51-20-01 or 737-500 SRM 51-20-01 as an accepted procedure.

(p) Apply external finish to match adjacent structure. Refer to 737-300/400/500 AMM 51-21-00 as an accepted

procedure.

FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 5 OF 6)

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BOEING SERVICE BULLETIN 737-53A1293
The codes shown below agree with the letter shown in the upper left corner of the fastener symbols in the figure.

A number in the lower right corner gives the grip length of the fastener. The QTY numbers shown below are the

number of fasteners necessary for this figure.

CODE NAME IDENTIFICATION QTY HOLE DIA MORE DATA

A RIVET BACR15BB6D5C 16 0.190 - 0.196 (a) (b)

RIVET BACR15BB6D6C 32 0.190 - 0.196 (a) (b)

B RIVET BACR15GF5D4 124 0.159 -0.165 (a) (b)

RIVET BACR15GF5D5 166 0.159 - 0.165 (a) (b)

RIVET BACR15GF5D6 51 0.159 - 0.165 (a) (b)

C RIVET BACR15BB6AD5C 68 0.190 - 0.196 (a) (b)

(a) Fastener length to be determined on installation. Grip lengths shown are for reference only.

(b) Over drive all rivets to a 1.4 times the diameter.

FIGURE 11: REPAIR DOUBLER FABRICATION AND INSTALLATION

(SHEET 6 OF 6)

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This Figure applies only to: Group 2.

FIGURE 12: POST REPAIR - CRITICAL FASTENER ROW INSPECTION

(SHEET 1 OF 2)

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BOEING SERVICE BULLETIN 737-53A1293
The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for each inspection.

STEP TASK NAME IDENTIFICATION QTY MORE DATA

1 Inspect SKIN - - (a)

(a) Do an external Non Destructive Inspection (NDI) for cracks in the skin under the doubler, at the fastener

locations in the shaded areas shown, in accordance with 737 NDT Part 6, 53-30-00, Figure 5.

FIGURE 12: POST REPAIR - CRITICAL FASTENER ROW INSPECTION

(SHEET 2 OF 2)

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BOEING SERVICE BULLETIN 737-53A1293
If crack damage is found that exceeds the limits of the repair or that is found prior to the SB inspection threshold,

Boeing requests as follows:

1. Contact Boeing for instructions on cutting out the damaged skin. Make sure that the skin cut-out includes

the full length of the chem-mill step, i.e. tear strap to tear strap.

2. Damage information:

a. Number of cracks: ______________________________

b. Length of crack(s): _____________________________

c. Body station of crack(s):__________________________

d. Location of crack(s) relative to adjacent stringer:____________________________

3. Airplane information:

a. Series: ________________________

b. Line Number: ________________________

c. Variable Number: ________________________

d. Flight cycles: ________________________

e. Flight hours: ________________________

4. Inspection procedure used:

a. When the crack was found: ________________________

b. At the previous inspection: ________________________

5. Number of flight cycles accumulated since the last inspection of the cracked detail: ___________________

6. Send the skin cut-out and inspection reports to Boeing for metallurgical evaluation.

Boeing Commercial Airplane Company

Spares Distribution Center

Repair Overhaul and Exchange Services, SSA 111

2201 South 142nd, Door W10

Seatac, Washington 98168, USA

Attention Airline Support Manager, forward to Post Production Fuselage Stress for engineering evaluation.

APPENDIX A: CHEM-MILL STEP CRACK DAMAGE CUT-OUT AND REPORT

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BOEING SERVICE BULLETIN 737-53A1293
If crack damage is found that can be repaired within the limits of this service bulletin, Boeing would still like to

obtain the information relative to the damage in order to develop more refined inspection requirements. It is not

necessary to send these damaged skin cut-outs into Boeing, but please send Boeing the inspection information,

as outlined below.

1. Damage Information:

a. Number of cracks: ________________________

b. Length of crack(s): ________________________

c. Body station of crack(s): ________________________

d. Location of crack(s) relative to adjacent stringer: ________________________

2. Airplane information:

a. Series: ________________________

b. Line Number: ________________________

c. Variable number: ________________________

d. Flight cycles: ________________________

e. Flight hours: ________________________

3. Inspection procedure used:

a. When the crack was found: ________________________

b. At the previous inspection: ________________________

4. Number of flight cycles accumulated since the last inspection of the cracked detail: ___________________

APPENDIX B: CHEM-MILL STEP CRACK DAMAGE REPORT

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BOEING SERVICE BULLETIN 737-53A1293