# Boeing Alert Service Bulletin 737-53A1251: Revision 2

- Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2021-0503; AD 2021-21-09 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication.
- Document: [Boeing Alert Service Bulletin 737-53A1251](https://openairdocs.org/service-documents/boeing/737-53a1251.md)
- Title as filed: SB-737-53A1251-02
- Pages: 47
- PDF: https://openairdocs.org/files/sha256/59/a2/59a2d2b8e34050dd2194490e3745f311fa12527d0c7935572f0b059de7003f5c
- Page: https://openairdocs.org/service-documents/boeing/737-53a1251/file/59a2d2b8e340

## Text

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### Page 1

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-53A1251
Original Issue: June 03, 2004
Revision 2: January 20, 2021
ATA System: 5311
SUBJECT: FUSELAGE - Frames and Bulkheads - Body Station 1016 Aft Pressure Bulkhead -
Apex Inspection
Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15
CFR 300-774). An export license may be required before it is used for development, production or use by foreign
persons from specific countries. The controller of this data has the individual responsibility to abide by all export
laws.
9E991ECCN:
BOEING PROPRIETARY, CONFIDENTIAL AND/OR TRADE SECRET
Copyright © 2004 Boeing.
Unpublished Work. All Rights Reserved.
Treatment of this document and its content is governed by contract with Boeing. Rights to use this document
are licensed on a per aircraft basis and such rights may not be transferable. For more information, contact The
Boeing Company.
Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner,
BBJ, DC-8, DC-9, DC-10, KC-10, KC-46, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8, Poseidon and
Boeing liveries are all trademarks owned by The Boeing Company; and no trademark license is granted in
connection with this document unless provided in writing by Boeing.
Original Issue: June 03, 2004
737-53A1251Revision 2: January 20, 2021
1 of 47
4.0

### Page 2

Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: June 03, 2004
737-53A1251Revision 2: January 20, 2021
2 of 47
BOEING SERVICE BULLETIN 737-53A1251
ALERTALERT
BLANK PAGE

### Page 3

Table of Contents
Revision Transmittal Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
E. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
H. Weight and Balance Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Existing Data: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2. Data Supplied with this Service Bulletin: . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3. Installation Drawings Used in the Preparation of this Service Bulletin: . . . . . . . . . . . 23
K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
M. Software Accomplishment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
C. Parts Necessary for Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2. Parts and Materials Supplied by the Operator . . . . . . . . . . . . . . . . . . . . . . . . 25
3. Parts Modified and Reidentified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 25
3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
FIGURE 1: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS  [Group 1] . . . 33
FIGURE 2: THIS FIGURE IS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . . . . . 35
FIGURE 3: AFT PRESSURE BULKHEAD - GENERAL VISUAL INSPECTION  [Group 2] . . . . . . . 36
FIGURE 4: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS  [Group 2] . . . 39
APPENDIX A: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE, TABLE 1: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME APEX GORE WEBS [Group 1] . . . . . . . . . 42
APPENDIX B: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE, TABLE 2: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME APEX GORE WEBS [Group 2] . . . . . . . . . 44
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
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737-53A1251Revision 2: January 20, 2021
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BOEING SERVICE BULLETIN 737-53A1251
ALERTALERT

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Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: June 03, 2004
737-53A1251Revision 2: January 20, 2021
4 of 47
BOEING SERVICE BULLETIN 737-53A1251
ALERTALERT
BLANK PAGE

### Page 5

Commercial 
Airplanes
737
Service Bulletin
ALERT
Revision Transmittal SheetNumber: 737-53A1251Original Issue: June 03, 2004
Revision 2: January 20, 2021
ATA System: 5311
SUBJECT: FUSELAGE - Frames and Bulkheads - Body Station 1016 Aft Pressure Bulkhead -
Apex Inspection
This revision includes all pages of the service bulletin.
COMPLIANCE INFORMATION RELATED TO THIS REVISION
Federal Aviation Administration (FAA) Airworthiness Directive AD 2005-05-18 is related to this service bulletin.
The effective date of AD 2005-05-18 is April 18, 2005.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2013-19-23 is related to this service bulletin.
The effective date of AD 2013-19-23 is November 7, 2013.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2017-10-22 is related to this service bulletin.
The effective date of AD 2017-10-22 is June 27, 2017.
The Federal Aviation Administration (FAA) will possibly release an additional Airworthiness Directive related to
this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service
bulletin mandatory.
Effects of this Revision on airplanes on which Orignal Issue and Revision 1 was previously done:
None.
REASON FOR REVISION
This revision is sent to update Group 1 compliance time and for Group 1 removed GVI for any repair.
These sections were changed:
1. In Summary and 1.D Description, updated Group 1 Actions.
2. In Paragraph 1.E., Compliance, updated compliance tables 1 and 2.
3. In 1.G Manpower, removed figure 2 for Group 1.
4. In Paragraph 3.B.2, Work Instructions, updated to match compliance tables 1 and 2.
5. Figure 2, was deleted.
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
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Original Issue: June 03, 2004
737-53A1251Revision 2: January 20, 2021
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### Page 6

6. APPENDIX A and B, updated logic diagrams for compliance tables 1 and 2.
Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity and format changes,
to show the location of all content changes.
Pages with no vertical lines have no changes.
REVISION HISTORY
June 03, 2004Original Issue:
September 22, 2020Revision 1:
January 20, 2021Revision 2:
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: June 03, 2004
737-53A1251Revision 2: January 20, 2021
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BOEING SERVICE BULLETIN 737-53A1251
ALERTALERT

### Page 7

Commercial 
Airplanes
737
Service Bulletin
ALERT
SummaryNumber: 737-53A1251Original Issue: June 03, 2004
Revision 2: January 20, 2021
ATA System: 5311
SUBJECT: FUSELAGE - Frames and Bulkheads - Body Station 1016 Aft Pressure Bulkhead -
Apex Inspection
THIS DOCUMENT IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN
PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS DOCUMENT
TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE
NEW OWNER.
CONCURRENT REQUIREMENTS
None.
BACKGROUND
Accomplishment of the inspections in this Service Bulletin will detect the propagation of cracks from fastener
holes in the web lap splices at Station (STA) 1016 Aft Pressure Bulkhead (APB) center dome apex. If the work
given in this service bulletin is not accomplished, multiple cracks in the APB gore webs of the center dome apex
could go undetected. Cracks in the webs may result in the inability of the APB to sustain limit loads and result
in rapid decompression of the fuselage.
During cycle tests of the Boeing 737-800 Fatigue Test Article, cracks were found in the APB web lap splices
common to the apex of the pressure dome. The cracks occurred at several of the fastener rows located in the
aft web at the lap splice area. The cracks were in the fastener rows located adjacent to the area where the web
transitions aft over the forward web in the lap splice. The pull down loading caused by the single rivet located
in the areas where each of the webs transitions up 0.032 inches over the adjacent web causes cracks to start
on the lap rivet holes. Cracks were found in three of the seven webs. Additional cracks have been found at the
single fastener locations between lap splices on 737 classic airplanes.
For Group 2, while performing High Frequency Eddy Current (HFEC) inspections of the APB web lap splice per
Service Bulletin 737-53A1353, five cracks common to the gore webs of the center dome apex were found. At
one location, the crack was linked from the first to the second fastener row. The current Service Bulletin
737-53A1353 and Maintenance Planning Data (MPD) do not provide adequate inspections for the subject cracks.
Operators should note only affected airplanes line numbers 1 through 1755 have a 0.032 inch web thickness.
Airplanes line numbers 1 to 1166 have a different fastener pattern than line numbers 1167 to 1755. The fasteners
in the apex dome region are subjected to fuselage pressurization fatigue cycles and clamp-up stresses during
the assembly process. Airplanes after line number 1755 have a web thickness 0.040 inch.
Boeing Service Related Problem (SRP) 737NG-SRP-53-0608 is related to this service bulletin.
Export Controlled ECCN: 9E991 - BOEING
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### Page 8

Boeing Fleet Team Digest (FTD) 737NG FTD 53-19005 is related to this service bulletin.
This table is provided to operators for planning purposes only. Refer to the applicable sections for more
information.
ReferenceAffectedPlanning Data
Paragraph 1.A.2., Spares AffectedNoSpares Affected
Paragraph 1.E., Compliance and Paragraph
1.F., Approval
YesAD Related
Paragraph 1.H., Weight and Balance ChangesNoWeight and Balance Change
Paragraph 1.I., Electrical Load DataNoElectrical Load Changed
Paragraph 1.K., Publications AffectedNoPublications Affected
Paragraph 1.K., Publications AffectedNoAirplane Flight Operations Affected (Flight Crew
Operations Manual and/or FAA Approved Air-
plane Flight Manual)
Paragraph 2.C.1., Kits/PartsNoKits/Parts Required
Paragraph 2.C.2., Parts and Materials Supplied
by the Operator
NoOperator Supplied Parts/Material
Paragraph 2.F., Special Tooling Necessary to
do this Service Bulletin
NoSpecial Tooling Required
ACTION (PRR 39800-023RS)
Group 1:
Do a Detailed Inspection and a HFEC Inspection around the web fasteners for any crack. Do a LFEC Inspection
around the hidden web lap splice fastener locations for any crack. If no crack is found, continue to do the repeat
Detailed Inspection, HFEC Inspection and LFEC Inspection, at the times specified in the compliance section of
this service bulletin. If any crack is found, contact The Boeing Company for repair instructions and do the repair.
Group 2:
Get access to the aft side of the Aft Pressure Bulkhead (APB). Do a General Visual Inspection for any repair. If
any repair found contact The Boeing Company for alternative inspection(s) to this Service Bulletin, and do the
inspection(s) and applicable on-condition action(s). Do a Detailed Inspection and a High Frequency Eddy Current
(HFEC) Inspection around the web fasteners for any crack in the unrepaired areas. Do a Low Frequency Eddy
Current (LFEC) Inspection around the hidden web lap splice fastener locations for any crack in the unrepaired
areas. If no repair is found, do a Detailed inspection, HFEC inspection and LFEC inspection of the Station (STA)
1016 Aft Pressure Bulkhead (APB) center dome apex gore webs including the web edges, lap splices and
outside lap splices for any crack. If any crack is found, contact The Boeing Company for repair instructions and
do the repair and repeat the Detailed, HFEC, LFEC Inspections of the STA 1016 APB center dome apex gore
webs for any crack. If no crack is found, repeat the Detailed, HFEC, LFEC Inspections of the STA 1016 APB
center dome apex gore webs for any crack.
EFFECTIVITY
737-600/-700/-700C/-800/-900 Airplane(s). Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplane(s).
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
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BOEING SERVICE BULLETIN 737-53A1251
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### Page 9

COMPLIANCE
Federal Aviation Administration (FAA) Airworthiness Directive AD 2005-05-18 is related to this service bulletin.
The effective date of AD 2005-05-18 is April 18, 2005.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2013-19-23 is related to this service bulletin.
The effective date of AD 2013-19-23 is November 7, 2013.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2017-10-22 is related to this service bulletin.
The effective date of AD 2017-10-22 is June 27, 2017.
The Federal Aviation Administration (FAA) will possibly release an additional Airworthiness Directive related to
this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service
bulletin mandatory.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION
Boeing warranty remedies are not available for the inspections given in this service bulletin.
MANPOWER
Refer to Paragraph 1.G., Manpower.
MATERIAL INFORMATION
None.
Export Controlled ECCN: 9E991 - BOEING
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ALERTALERT

### Page 10 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
S-7L  BL
ACCESS
DOOR
TEAR
•STRAP
WEB LAP SPLICE
(7 LOCATIONS)
S-7R
DO A GENERAL VISUAL  S-15L-
INSPECTION OF THE AFT
PRESSURE BULKHEAD
(APB) CENTER DOME
APEX GORE WEBS FOR
ANY REPAIR (GROUP 2)
DO A DETAILED, HIGH
FREQUENCY EDDY CURRENT
AND LOW FREQUENCY EDDY  S-23L  —S-15R
CURRENT INSPECTIONS OF
THE STATION (STA) 1016 AFT
PRESSURE BULKHEAD (APB)
CENTER DOME APEX GORE
WEBS FOR ANY CRACK  DOUBLER
AFT PRESSURE BULKHEAD  S-23R
2935759
Original Issue: June 03, 2004
Revision 2: January 20, 2021  PROPRIETARY - Copyright © Unpublished  Export Controlled ECCN: 9E991 - BOEING  737-53A1251
Work - See page 1 for details.  10 of 47

### Page 11

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-53A1251
Original Issue: June 03, 2004
Revision 2: January 20, 2021
ATA System: 5311
SUBJECT: FUSELAGE - Frames and Bulkheads - Body Station 1016 Aft Pressure Bulkhead -
Apex Inspection
THIS DOCUMENT IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN
PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS DOCUMENT
TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS DOCUMENT TO THE
NEW OWNER.
1.    PLANNING INFORMATION
A. Effectivity
1. Airplanes
Refer to Service Bulletin Index D6-19567 Part 3 for Airplane Variable Number, Line Number, and
Serial Number data.
This bulletin is applicable to 737-600, 737-700, 737-700C, 737-800, 737-900 Airplane(s), line
number(s) 1-1755 in 2 Group(s). Where the effectivity is presented with hyphens between line
numbers, the airplane applicability means "through" and "inclusive", e.g. line numbers 1-9 means
line numbers 1 through 9 inclusive.
The Variable Numbers and Group Information for the applicable airplanes is given below.
DESCRIPTIONCONFIGURATIONGROUP
All 737-600, -700, -700C, -800, -900 airplanes line numbers 1 through
1166.
-1
All 737-600, -700, -700C, -800, -900 airplanes line numbers 1167
through 1755.
-2
Airplane Models:
737-600, 737-700, 737-700C, 737-800, 737-900
GroupVariable Number
1YA001 - YA099
GroupVariable Number
1YA101 - YA124
GroupVariable Number
2YA125 - YA199
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GroupVariable Number
1YA201 - YA211
2YA221
1YA231 - YA242
1YA251 - YA256
1YA271 - YA272
1YA291
1YA301 - YA302
1YA311 - YA314
1YA321 - YA323
1YA336 - YA343
2YA344 - YA345
1YA351
1YA356 - YA357
1YA366 - YA367
2YA371 - YA377
1YA501 - YA536
1YA541 - YA552
1YA571 - YA578
1YA601 - YA615
1YA621 - YA622
1YA626 - YA629
2YA630 - YA631
1YA635 - YA636
2YA641 - YA642
1YA645 - YA647
2YA648 - YA650
1YA656 - YA659
2YA666 - YA667
1YA671 - YA672
1YA681 - YA691
1YA701 - YA706
2YA707 - YA710
1YA721 - YA722
GroupVariable Number
1YA731 - YA734
1YA751 - YA756
1YA801 - YA803
1YA809
1YA811 - YA814
1YA831 - YA834
2YA835
1YA841 - YA856
2YA857 - YA862
1YA881 - YA882
1YA891 - YA892
1YA961 - YA967
2YA968 - YA976
1YB001 - YB006
1YB101 - YB116
2YB117 - YB132
1YB151 - YB153
2YB156 - YB157
1YB161 - YB162
2YB163 - YB164
1YB171 - YB172
1YB181 - YB183
2YB184
1YB201 - YB207
2YB208
1YB271
1YB276
1YB301 - YB306
2YB307 - YB310
2YB371 - YB381
1YB501 - YB502
1YB521
2YB522 - YB526
GroupVariable Number
2YB541 - YB544
1YB551
2YB561 - YB574
2YB576 - YB577
2YB581 - YB587
2YB601 - YB632
2YB651
2YB656
2YB851 - YB863
2YB871 - YB873
2YB881 - YB888
2YB901 - YB903
2YB911
1YC001 - YC030
1YC051 - YC082
2YC083
1YC091 - YC094
1YC101 - YC104
1YC111 - YC113
1YC121
1YC126 - YC127
1YC136 - YC141
1YC146 - YC147
1YC151 - YC156
1YC166 - YC168
2YC169 - YC170
1YC171
1YC176
2YC177 - YC178
2YC186 - YC189
2YC201 - YC203
2YC206 - YC207
1YC301 - YC304
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GroupVariable Number
2YC305
1YC321 - YC383
2YC384 - YC386
1YC391 - YC392
2YC393 - YC394
1YC396
1YC401 - YC417
1YC421 - YC422
1YC426 - YC428
1YC436 - YC437
1YC441 - YC448
1YC451 - YC455
1YC459
1YC461 - YC467
1YC471 - YC491
2YC492 - YC499
1YC501 - YC526
1YC571 - YC581
2YC582 - YC583
1YC587 - YC589
1YC591 - YC593
1YC601 - YC655
1YC681 - YC696
1YC701 - YC715
1YC720 - YC725
1YC727 - YC739
2YC740 - YC741
1YC751 - YC752
1YC761 - YC770
1YC781 - YC793
1YC801 - YC888
2YC889 - YC892
1YC901 - YC907
GroupVariable Number
1YC921
2YC922
1YC931 - YC932
1YC941 - YC949
2YC950 - YC951
1YC971 - YC976
2YC977 - YC978
1YC981 - YC983
1YD001 - YD006
2YD007
1YD021 - YD025
1YD041 - YD054
2YD055 - YD057
1YD081 - YD084
1YD101 - YD107
2YD108
1YD121 - YD126
1YD151 - YD153
2YD154 - YD159
1YD171 - YD172
1YD201 - YD203
1YD206 - YD208
2YD209
1YD216
2YD217 - YD219
1YD251 - YD253
2YD254
2YD256 - YD257
2YD261
1YD301 - YD324
2YD325 - YD334
1YD391
1YD401 - YD409
GroupVariable Number
2YD410
2YD412
2YD481 - YD485
2YD491
1YD501 - YD506
2YD507 - YD512
1YD531 - YD534
2YD535
1YD541 - YD544
2YD545 - YD547
2YD561 - YD564
2YD571 - YD572
2YD591 - YD595
1YD601 - YD612
2YD651 - YD653
1YE001 - YE020
1YE051
1YE101 - YE109
1YE151 - YE157
1YE171 - YE172
1YE201 - YE203
2YE204 - YE206
1YE301 - YE305
2YE321 - YE326
1YG001 - YG043
2YG044
1YG061 - YG064
1YG066 - YG084
2YG085 - YG089
2YG091
2YG201
2YG211
1YG501 - YG505
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GroupVariable Number
2YG506 - YG508
1YG601 - YG602
2YJ001 - YJ004
2YJ011 - YJ013
2YJ021
1YJ471 - YJ476
2YJ477 - YJ480
1YJ501 - YJ517
2YJ531 - YJ546
2YJ591 - YJ594
1YJ631 - YJ632
2YJ671 - YJ682
2YJ801 - YJ853
2YJ861 - YJ867
2YJ871
GroupVariable Number
2YJ901 - YJ902
2YJ911 - YJ923
2YJ931 - YJ936
2YJ941 - YJ943
2YK001 - YK007
2YK101 - YK104
2YK111 - YK112
2YK121 - YK122
2YK131 - YK132
2YK136 - YK137
2YK301 - YK304
2YK321 - YK330
2YK361 - YK366
2YK401 - YK406
2YK426 - YK427
GroupVariable Number
2YK431 - YK432
2YK456 - YK460
2YK480 - YK484
2YK511 - YK512
2YK601
2YM101 - YM103
2YM201 - YM204
2YM251 - YM267
2YM471
2YM481 - YM482
2YM521
2YM541
2YM551
--
--
2. Spares Affected
None.
B. Concurrent Requirements
None.
C. Reason
Accomplishment of the inspections in this Service Bulletin will detect the propagation of cracks from
fastener holes in the web lap splices at Station (STA) 1016 Aft Pressure Bulkhead (APB) center dome
apex. If the work given in this service bulletin is not accomplished, multiple cracks in the APB gore
webs of the center dome apex could go undetected. Cracks in the web may result in the inability of the
APB to sustain limit loads and result in rapid decompression of the fuselage.
During cycle tests of the Boeing 737-800 Fatigue Test Article, cracks were found in the APB web lap
splices common to the apex of the pressure dome. The cracks occurred at several of the fastener rows
located in the aft web at the lap splice area. The cracks were in the fastener rows located adjacent to
the area where the web transitions aft over the forward web in the lap splice. The pull down loading
caused by the single rivet located in the areas where each of the webs transitions up 0.032 inches over
the adjacent web causes cracks to start on the lap rivet holes. Cracks were found in three of the seven
webs. Additional cracks have been found at the single fastener locations between lap splices on 737
classic airplanes.
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For Group 2, while performing High Frequency Eddy Current (HFEC) inspections of the APB web lap
splice per Service Bulletin 737-53A1353, five cracks common to the gore webs of the center dome
apex were found. At one location, the crack was linked from the first to the second fastener row. The
current Service Bulletin 737-53A1353 and Maintenance Planning Data (MPD) do not provide adequate
inspections for the subject cracks.
Operators should note only affected airplanes line numbers 1 through 1755 have a 0.032 inch web
thickness. Airplanes line numbers 1 to 1166 have a different fastener pattern than line numbers 1167
to 1755. The fasteners in the apex dome region are subjected to fuselage pressurization fatigue cycles
and clamp-up stresses during the assembly process. Airplanes after line number 1755 have a web
thickness 0.040 inch.
Boeing Service Related Problem (SRP) 737NG-SRP-53-0608 is related to this service bulletin.
Boeing Fleet Team Digest (FTD) 737NG FTD 53-19005 is related to this service bulletin.
Revision 01 is sent to add inspections for LN 1167-1755 for cracking that was found at five of seven
apex gore webs while performing inspections per SB 737-53A1353. The new LN 1167-1755 will be
contained in Group 2 since the apex fastener configuration is different than LN 1-1166 contained in
Group 1 of the original release of this SB 737-53-1251. An additional requirement of performing a
General Visual Inspection (GVI) for repairs was added to determine the new compliance time for the
unrepaired areas. Group 1 and Group 2 both contain new Work Instructions and new Figures for
performing GVI. The inspection requirement for the Supplemental Inspection Planning Document (SIPD)
is inadequate to find the subject cracking.
Revision 02 is sent to update Group 1 compliance time and for Group 1 removed GVI for any repair.
D. Description
Group 1:
Do a Detailed Inspection and a HFEC Inspection around the web fasteners for any crack. Do a LFEC
Inspection around the hidden web lap splice fastener locations for any crack. If no crack is found,
continue to do the repeat Detailed Inspection, HFEC Inspection and LFEC Inspection, at the times
specified in the compliance section of this service bulletin. If any crack is found, contact The Boeing
Company for repair instructions and do the repair.
Group 2:
Get access to the aft side of the Aft Pressure Bulkhead (APB). Do a General Visual Inspection for any
repair. If any repair found contact The Boeing Company for alternative inspection(s) to this Service
Bulletin, and do the inspection(s) and applicable on-condition action(s). Do a Detailed Inspection and
a High Frequency Eddy Current (HFEC) Inspection around the web fasteners for any crack in the
unrepaired areas. Do a Low Frequency Eddy Current (LFEC) Inspection around the hidden web lap
splice fastener locations for any crack in the unrepaired areas. If no repair is found, do a Detailed
inspection, HFEC inspection and LFEC inspection of the Station (STA) 1016 Aft Pressure Bulkhead
(APB) center dome apex gore webs including the web edges, lap splices and outside lap splices for
any crack. If any crack is found, contact The Boeing Company for repair instructions and do the repair
and repeat the Detailed, HFEC, LFEC Inspections of the STA 1016 APB center dome apex gore webs
for any crack. If no crack is found, repeat the Detailed, HFEC, LFEC Inspections of the STA 1016 APB
center dome apex gore webs for any crack.
Effects of this Revision on airplanes on which Original Issue and Revision 1 was previously done:
None.
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The work in this service bulletin is done in the maintenance zone(s) given below.
Affected Maintenance Zones
ZoneModel
311, 312737-600, 737-700, 737-700C,
737-800, 737-900
E. Compliance
Federal Aviation Administration (FAA) Airworthiness Directive AD 2005-05-18 is related to this service
bulletin. The effective date of AD 2005-05-18 is April 18, 2005.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2013-19-23 is related to this service
bulletin. The effective date of AD 2013-19-23 is November 7, 2013.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2017-10-22 is related to this service
bulletin. The effective date of AD 2017-10-22 is June 27, 2017.
The Federal Aviation Administration (FAA) will possibly release an additional Airworthiness Directive
related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times
given in this service bulletin mandatory.
For airplanes which have incorporated Boeing Business Jet (BBJ) Lower Cabin Altitude Supplemental
Type Certificate (STC) ST01697SE (6500 feet maximum cabin altitude in lieu of 8000 feet) as referenced
in Boeing SB 737-21-1149, the flight cycle related compliance times are different from those specified
in this service bulletin. All initial compliance times (thresholds) specified in flight cycles must be reduced
to half of those specified in this service bulletin. All repeat interval compliance times specified in flight
cycles must be reduced to one-quarter of those specified in this service bulletin.
Do the required actions in accordance with Paragraph 3. Accomplishment Instructions.
When more than one OPTION is given for a CONDITION, do only one of the OPTION numbers. When
more than one ACTION is given for a CONDITION or an OPTION, do all of the ACTION numbers for
that CONDITION or OPTION.
A logic diagram showing compliance tasks and compliance times is included as an aid in APPENDIX
A and APPENDIX B.
Group 1:
Table 1: Inspections of the Aft Side of the Aft Pressure Bulkhead (APB)
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Within 4,000
flight cycles after
the effective date
of AD 2005-05-
18.
Before 26,000
total flight cycles.
Do a Detailed, High Frequen-
cy Eddy Current (HFEC) and
Low Frequency Eddy Cur-
rent (LFEC) Inspections of
the aft side of the Aft Pres-
sure Bulkhead (APB) for any
crack.
All Airplanes.
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Group 1:
Table 1: Inspections of the Aft Side of the Aft Pressure Bulkhead (APB)
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Before further flight.CONDITION 1 (ACTION 1):CONDITION 1:
Contact The Boeing Compa-
ny for repair instructions and
do the repair.
ANY CRACK
FOUND.
4,000 flight cycles.-CONDITION 1 (ACTION 2):
Repeat the Detailed, High
Frequency Eddy Current
(HFEC) and Low Frequency
Eddy Current (LFEC) Inspec-
tions of the aft side of the Aft
Pressure Bulkhead (APB) for
any crack. (a)
4,000 flight cycles.-Repeat the Detailed, High
Frequency Eddy Current
(HFEC) and Low Frequency
Eddy Current (LFEC) Inspec-
tions of the aft side of the Aft
Pressure Bulkhead (APB) for
any crack. (a)
CONDITION 2:
NO CRACK FOUND.
(a) It is not required to do the inspections of the aft side of the Aft Pressure Bulkhead (APB) in areas where
a repair covers the affected inspection zones provided:
1. The repair is the corrective action to the crack condition identified in Service Bulletin 737-53A1251
or in Service Bulletin 737-53A1353 and installed after the original issue date of Service Bulletins
737-53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company Organization Designation Authoriza-
tion (ODA) via a FAA Form 8100-9.
Group 2:
Table 2: Inspections of the Aft Side of the Aft Pressure Bulkhead (APB)
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Within 4,000
flight cycles after
the Revision 1
date of this Ser-
vice Bulletin.
Before 23,000
total flight cycles.
Do a General Visual Inspec-
tion of the aft side of the Aft
Pressure Bulkhead (APB) for
any repair.
All Airplanes.
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Group 2:
Table 2: Inspections of the Aft Side of the Aft Pressure Bulkhead (APB)
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Within 4,000
flight cycles after
the Revision 1
date of this Ser-
vice Bulletin.
Before 23,000
total flight cycles.
CONDITION 3 (ACTION 1):
Contact The Boeing Compa-
ny for alternative inspec-
tion(s) to this Service Bul-
letin, and do the inspec-
tion(s) and applicable on-
condition action(s). (a)
CONDITION 3:
ANY REPAIR
FOUND.
-Within 4,000
flight cycles after
the Revision 1
date of this Ser-
vice Bulletin.
Before 23,000
total flight cycles.
CONDITION 3 (ACTION 2):
Do a Detailed, High Frequen-
cy Eddy Current (HFEC) and
Low Frequency Eddy Cur-
rent (LFEC) Inspections of
the aft side of the Aft Pres-
sure Bulkhead (APB) for any
crack at the unrepaired ar-
eas.
-Before further flight.CONDITION 3.1 (ACTION
1):
CONDITION 3.1:
ANY CRACK
FOUND. Contact The Boeing Compa-
ny for repair instructions and
do the repair.
4,000 flight cycles.-CONDITION 3.1 (ACTION
2):
Repeat the Detailed, High
Frequency Eddy Current
(HFEC) and Low Frequency
Eddy Current (LFEC) Inspec-
tions of the aft side of the Aft
Pressure Bulkhead (APB) for
any crack at the unrepaired
areas. (b)
4,000 flight cycles.-Repeat the Detailed, High
Frequency Eddy Current
(HFEC) and Low Frequency
Eddy Current (LFEC) Inspec-
tions of the aft side of the Aft
Pressure Bulkhead (APB) for
any crack at the unrepaired
areas. (b)
CONDITION 3.2:
NO CRACK FOUND.
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Group 2:
Table 2: Inspections of the Aft Side of the Aft Pressure Bulkhead (APB)
Repeat Interval
(Not to Exceed)
Compliance Time (Whichever
Occurs Later)
ActionCondition
-Within 4,000
flight cycles after
the Revision 1
date of this Ser-
vice Bulletin.
Before 23,000
total flight cycles.
Do a Detailed, High Frequen-
cy Eddy Current (HFEC) and
Low Frequency Eddy Cur-
rent (LFEC) Inspections of
the aft side of the Aft Pres-
sure Bulkhead (APB) for any
crack.
CONDITION 4:
NO REPAIR FOUND.
-Before further flight.CONDITION 4.1 (ACTION
1):
CONDITION 4.1:
ANY CRACK
FOUND. Contact The Boeing Compa-
ny for repair instructions and
do the repair.
4,000 flight cycles.-CONDITION 4.1 (ACTION
2):
Repeat the Detailed, High
Frequency Eddy Current
(HFEC) and Low Frequency
Eddy Current (LFEC) Inspec-
tions of the aft side of the Aft
Pressure Bulkhead (APB) for
any crack. (b)
4,000 flight cycles.-Repeat the Detailed, High
Frequency Eddy Current
(HFEC) and Low Frequency
Eddy Current (LFEC) Inspec-
tions of the aft side of the Aft
Pressure Bulkhead (APB) for
any crack. (b)
CONDITION 4.2:
NO CRACK FOUND.
(a) Condition 3 (Action 1) is not required for any repair found during the General Visual Inspection (GVI) of
the aft side of the Aft Pressure Bulkhead (APB) in areas where a repair covers the affected inspection
zones provided that the installed repair was approved by The Boeing Company Organization Designation
Authorization (ODA) via a FAA Form 8100-9 and inspections are accomplished in accordance with the
scheduled repair approval listed on the FAA Form 8100-9.
(b) It is not required to do the inspections of the aft side of the Aft Pressure Bulkhead (APB) in areas where
a repair covers the affected inspection zones provided:
1. The repair is the corrective action to the crack condition identified in Service Bulletin 737-53A1251
or in Service Bulletin 737-53A1353 and installed after the original issue date of Service Bulletins
737-53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company Organization Designation Authoriza-
tion (ODA) via a FAA Form 8100-9.
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F. Approval
NOTE: THE APPROVAL STATEMENT THAT FOLLOWS IS VALID FOR ALL AFFECTED AIRPLANES,
EXCEPT FOR 737-700C AIRPLANES.
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
Union 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.
This service bulletin is also approved for airplanes having FAA Aviation Partners Boeing (APB)
Supplemental Type Certificate (STC) number ST00830SE installed (not including any areas affected
by the split scimitar winglet configuration).
For BBJ models that have APB winglets installed by STC number ST00830SE, the operator is
responsible for obtaining appropriate regulatory agency approval before incorporating this service
bulletin if the bulletin is in the area affected by blended winglets.
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.
The Manager of the FAA Seattle ACO Branch approves accomplishment of the applicable inspection
program defined in this SB revision as an Alternative Method of Compliance (AMOC) to the inspections
required by paragraph (f) of AD 2005-05-18. All provisions of AD 2005-05-18 that are not specifically
referenced above remain fully applicable and must be complied with accordingly.
In addition, the Manager of the FAA Seattle ACO Branch approves the incorporation of the applicable
inspection program defined in this SB revision as an AMOC, to the incorporation of the corresponding
inspections for PSE 53-80-01-3 and 53-80-01-7, required by paragraph (g) of AD 2013-19-23. This
AMOC is only applicable after accomplishment of the initial inspections and is limited to the areas
inspected. All provisions of AD 2013-19-23 that are not specifically referenced above remain fully
applicable and must be complied with accordingly.
In addition, the Manager of the FAA Seattle ACO Branch approves accomplishment of the applicable
inspections defined in this SB revision as an AMOC, for the corresponding inspections required by
paragraph (g) of AD 2017-10-22. This AMOC is only applicable after accomplishment of the initial
inspections and is limited to the areas inspected. All provisions of AD 2017-10-22 that are not specifically
referenced above remain fully applicable and must be complied with accordingly.
This Service Bulletin is also approved for airplanes converted into 737-800BCF under project number
TS14-0042 that have incorporated Boeing drawing 800A0003 specified in the Type Certification Data
Sheet A16WE.
NOTE: THE APPROVAL STATEMENT THAT FOLLOWS IS FOR 737-700C AIRPLANES ONLY.
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 for the 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.
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For 737-700C models that have APB winglets installed by STC number ST00830SE, the operator is
responsible for obtaining appropriate regulatory agency approval before incorporating this service
bulletin if the bulletin is in the area affected by blended winglets.
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.
The Manager of the FAA Seattle ACO Branch approves accomplishment of the applicable inspection
program defined in this SB revision as an Alternative Method of Compliance (AMOC) to the inspections
required by paragraph (f) of AD 2005-05-18. All provisions of AD 2005-05-18 that are not specifically
referenced above remain fully applicable and must be complied with accordingly.
In addition, the Manager of the FAA Seattle ACO Branch approves the incorporation of the applicable
inspection program defined in this SB revision as an AMOC, to the incorporation of the corresponding
inspections for PSE 53-80-01-3 and 53-80-01-7, required by paragraph (g) of AD 2013-19-23. This
AMOC is only applicable after accomplishment of the initial inspections and is limited to the areas
inspected. All provisions of AD 2013-19-23 that are not specifically referenced above remain fully
applicable and must be complied with accordingly.
In addition, the Manager of the FAA Seattle ACO Branch approves accomplishment of the applicable
inspections defined in this SB revision as an AMOC, for the corresponding inspections required by
paragraph (g) of AD 2017-10-22. This AMOC is only applicable after accomplishment of the initial
inspections and is limited to the areas inspected. All provisions of AD 2017-10-22 that are not specifically
referenced above 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 change 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:
Elapsed HoursTask HoursNumber of
Persons
Task
0.250.251Open Access
2.02.01FIGURE 1 - Detailed Inspection
1.53.02FIGURE 1 - Low Frequency Eddy Current
Inspection
1.53.02FIGURE 1 - High Frequency Eddy Current
Inspection
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Group 1:
Elapsed HoursTask HoursNumber of
Persons
Task
0.250.251Close Access
5.58.5TOTAL FOR EACH AIRPLANE
Group 2:
Elapsed HoursTask HoursNumber of
Persons
Task
0.250.251Open Access
0.500.501FIGURE 3 - General Visual Inspection
2.02.01FIGURE 4 - Detailed Inspection
1.53.02FIGURE 4 - Low Frequency Eddy Current
Inspection
1.53.02FIGURE 4 - High Frequency Eddy Current
Inspection
0.250.251Close Access
6.09.0TOTAL FOR EACH AIRPLANE
H. Weight and Balance Changes
None.
I. Electrical Load Data
Not changed.
J. References
1. Existing Data:
a. Engineering Change Memo PRR 39800-023RS
b. Boeing Service Bulletins 737-21-1149, 737-53-1251, 737-53A1353
c. Boeing Service Related Problem (SRP) 737NG-SRP-53-0608
d. Federal Aviation Administration (FAA) Airworthiness Directives (AD) 2005-05-18, 2013-19-23,
2017-10-22
e. Service Bulletin Index D6-19567
f. 737 Non-Destructive Testing (NDT) Manual Part 6, 53-10-64
g. 737-600/700/800/900 Aircraft Maintenance Manual (AMM) 52-49-11
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h. Boeing Fleet Team Digest (FTD) 737NG FTD 53-19005
2. Data Supplied with this Service Bulletin:
None.
3. Installation Drawings Used in the Preparation of this Service Bulletin:
TitleDrawing Number
PRESSURE BULKHEAD ASSEMBLY - STA 1016148A2280
BULKHEAD INTEGRATION INSTALLATION - STA 1016148A0922
The table above lists applicable drawings used to prepare this service bulletin. The drawings are
not necessary to make the specified changes, and are not supplied with this service bulletin. The
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 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.
M. Software Accomplishment Summary
Not affected.
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### Page 25

2.    MATERIAL INFORMATION
A. Material - Price and Availability
None.
B. Industry Support Information
Boeing warranty remedies are not available for the configuration changes, 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
None.
3. Parts Modified and Reidentified
None.
4. Parts Removed and Not Replaced
None.
D. Parts Necessary to Change Spares
None.
E. Special Tooling - Price and Availability
None.
F. Special Tooling Necessary to do this Service Bulletin
No special tools or equipment are necessary to do the change in this service bulletin. But, maintenance
and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine
operator tool supply to make sure all necessary tools are available.
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### Page 27

3.    ACCOMPLISHMENT INSTRUCTIONS
A. GENERAL INFORMATION
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 and fasteners are in Structural Repair
Manual (SRM) Chapter 51
– Torque Values:
— Values for structural fasteners are given in 737 Structural Repair Manual,
Chapter 51.
— Values for airframe maintenance tasks are included in Chapter 20 of 737
Aircraft Maintenance Manual (AMM).
— Non-standard torque values for maintenance tasks are included in the
applicable installation step.
4. A Detailed Inspection is defined as: An intensive examination of a specific item,
installation, or assembly to detect damage, failure, or irregularity. This could include
tactile assessment in which a component or assembly can be checked for
tightness/security. Available lighting is normally supplemented with a direct source
of good lighting at an intensity deemed appropriate. Inspection aids such as mirrors,
magnifying lenses, etc. may be necessary. Surface cleaning and elaborate procedures
may be required.
5. A General Visual Inspection is defined as: A visual examination of an interior or
exterior area, installation or assembly to detect obvious damage, failure or irregularity.
This level of inspection is made from within touching distance unless otherwise
specified. A mirror may be necessary to enhance visual access to all exposed surfaces
in the inspection area. This level of inspection is made under normally available
lighting conditions such as daylight, hangar lighting, flashlight or drop-light and may
require removal or opening of access panels or doors. Stands, ladders or platforms
may be required to gain proximity to the area being checked. Basic cleaning may be
required to ensure appropriate visibility.
6. 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.
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7. Refer to Appendix A and Appendix B for logic diagram(s). Logic diagrams are provided
as an aid only. Information contained in Paragraph 1.E., Compliance is the primary
source for compliance times. Information in Paragraph 3.B., Work Instructions is the
primary source for tasks required for compliance.
8. The instructions in Paragraph 3.B., Work Instructions and the figures can include
operation of tools or test equipment. Boeing Engineering Tool Drawings, the Illustrated
Tool and Equipment Manual, and the Special Tool and Ground Handling Drawing
Index contain data on versions of the tools or test equipment that you can use. It is
permitted to use replaced tools. It is not permitted to use superseded tools.
9. 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.
10. 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.
11. If shading is used, shaded areas in Figures are to separate the non-critical and
non-authoritative information from the critical and authoritative information.
12. When more than one OPTION is given for a CONDITION, do only one of the OPTION
numbers. When more than one ACTION is given for a CONDITION or an OPTION,
do all of the ACTION numbers for that CONDITION or OPTION.
13. The compliance times for the actions in Paragraph 3.B., WORK INSTRUCTIONS
are in Paragraph 1.E., Compliance.
14. Some steps in the Work Instructions are labeled as Required for Compliance (RC).
If this service bulletin is mandated by an Airworthiness Directive (AD), then the steps
labeled as RC, including sub-steps under an RC step and any figures identified in
an RC step, must be done to comply with the AD. If a step or sub-step is labeled
"RC Exempt," then the RC requirement is removed from that step or sub-step. An
Alternative Method of Compliance (AMOC) is required for any deviations to RC steps,
including sub-steps and identified figures. Steps not labeled as RC may be deviated
from using accepted methods in accordance with the operator's maintenance or
inspection program without obtaining approval of an AMOC. This is provided that
the RC steps, including sub-steps and identified figures, can still be done as specified,
and the airplane can be put back in an airworthy condition.
B. WORK INSTRUCTIONS
Group 1:
1. Get access to the aft side of the Aft Pressure Bulkhead (APB) through the section 48 access and
blowout access door, refer to 737-600/700/800/900 AMM 52-49-11 as an accepted procedure.
2. Do a Detailed, High Frequency Eddy Current (HFEC) and Low Frequency Eddy Current (LFEC)
Inspections of the aft side of the Aft Pressure Bulkhead (APB) for any crack in accordance with
FIGURE 1.
a. CONDITION 1: ANY CRACK FOUND.
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(1) CONDITION 1 (ACTION 1):
(a) Contact The Boeing Company for repair instructions and do the repair.
(2) CONDITION 1 (ACTION 2):
(a) Repeat the Detailed, HFEC and LFEC Inspections of the aft side of the Aft Pressure
Bulkhead (APB) for any crack in accordance with FIGURE 1.
NOTE: It is not required to do the inspections of the aft side of the Aft Pressure
Bulkhead (APB) in areas where a repair covers the affected inspection
zones provided:
1. The repair is the corrective action to the crack condition identified
in Service Bulletin 737-53A1251 or in Service Bulletin 737-53A1353
and installed after the original issue date of Service Bulletins
737-53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company
Organization Designation Authorization (ODA) via a FAA Form
8100-9.
b. CONDITION 2: NO CRACK FOUND.
(1) Repeat the Detailed, High Frequency Eddy Current (HFEC) and Low Frequency Eddy
Current (LFEC) Inspections of the aft side of the Aft Pressure Bulkhead (APB) for any
crack in accordance with FIGURE 1.
NOTE: It is not required to do the inspections of the aft side of the Aft Pressure Bulkhead
(APB) in areas where a repair covers the affected inspection zones provided:
1. The repair is the corrective action to the crack condition identified in
Service Bulletin 737-53A1251 or in Service Bulletin 737-53A1353 and
installed after the original issue date of Service Bulletins 737-53-1251
or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company
Organization Designation Authorization (ODA) via a FAA Form 8100-9.
3. Close the section 48 access and blowout door, refer to 737-600/700/800/900 AMM 52-49-11 as
an accepted procedure.
4. Put the airplane back to a serviceable condition.
Group 2:
1. Get access to the aft side of the Aft Pressure Bulkhead (APB) through the section 48 access and
blowout access door refer to 737-600/700/800/900 AMM 52-49-11 as an accepted procedure.
2. RC - Do a General Visual Inspection of the aft side of the Aft Pressure Bulkhead (APB) for any
repair in accordance with FIGURE 3.
a. CONDITION 3: ANY REPAIR FOUND.
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(1) CONDITION 3 (ACTION 1):
(a) Contact The Boeing Company for alternative inspection(s) to this Service Bulletin,
and do the inspection(s) and applicable on-condition action(s).
NOTE: Condition 3 (Action 1) is not required for any repair found during the General
Visual Inspection (GVI) of the aft side of the Aft Pressure Bulkhead (APB)
in areas where a repair covers the affected inspection zones provided that
the installed repair was approved by The Boeing Company Organization
Designation Authorization (ODA) via a FAA Form 8100-9 and inspections
are accomplished in accordance with the scheduled repair approval listed
on the FAA Form 8100-9.
(2) CONDITION 3 (ACTION 2):
(a) Do a Detailed, High Frequency Eddy Current (HFEC) and Low Frequency Eddy
Current (LFEC) Inspections of the aft side of the Aft Pressure Bulkhead (APB) for
any crack at the unrepaired areas in accordance with FIGURE 4.
1) CONDITION 3.1: ANY CRACK FOUND.
a) CONDITION 3.1 (ACTION 1):
{1} Contact The Boeing Company for repair instructions and do the repair.
b) CONDITION 3.1 (ACTION 2):
{1} Repeat the Detailed, HFEC and LFEC Inspections of the aft side of the
Aft Pressure Bulkhead (APB) for any crack at the unrepaired areas in
accordance with FIGURE 4.
NOTE: It is not required to do the inspections of the aft side of the Aft
Pressure Bulkhead (APB) in areas where a repair covers the
affected inspection zones provided:
1. The repair is the corrective action to the crack
condition identified in Service Bulletin 737-53A1251
or in Service Bulletin 737-53A1353 and installed after
the original issue date of Service Bulletins
737-53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing
Company Organization Designation Authorization
(ODA) via a FAA Form 8100-9.
2) CONDITION 3.2: NO CRACK FOUND.
a) Repeat the Detailed, HFEC and LFEC Inspections of the aft side of the Aft
Pressure Bulkhead (APB) at the unrepaired areas in accordance with
FIGURE 4.
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NOTE: It is not required to do the inspections of the aft side of the Aft
Pressure Bulkhead (APB) in areas where a repair covers the
affected inspection zones provided:
1. The repair is the corrective action to the crack condition
identified in Service Bulletin 737-53A1251 or in Service
Bulletin 737-53A1353 and installed after the original issue
date of Service Bulletins 737-53-1251 or 737-53A1353,
AND
2. The installed repair was approved by The Boeing
Company Organization Designation Authorization (ODA)
via a FAA Form 8100-9.
b. CONDITION 4: NO REPAIR FOUND.
(1) Do a Detailed, High Frequency Eddy Current (HFEC) and Low Frequency Eddy Current
(LFEC) Inspections of the aft side of the Aft Pressure Bulkhead (APB) for any crack in
accordance with FIGURE 4.
(a) CONDITION 4.1: ANY CRACK FOUND.
1) CONDITION 4.1 (ACTION 1):
a) Contact The Boeing Company for repair instructions and do the repair.
2) CONDITION 4.1 (ACTION 2):
a) Repeat the Detailed, HFEC and LFEC Inspections of the aft side of the Aft
Pressure Bulkhead (APB) for any crack in accordance with FIGURE 4.
NOTE: It is not required to do the inspections of the aft side of the Aft
Pressure Bulkhead (APB) in areas where a repair covers the
affected inspection zones provided:
1. The repair is the corrective action to the crack condition
identified in Service Bulletin 737-53A1251 or in Service
Bulletin 737-53A1353 and installed after the original issue
date of Service Bulletins 737-53-1251 or 737-53A1353,
AND
2. The installed repair was approved by The Boeing
Company Organization Designation Authorization (ODA)
via a FAA Form 8100-9.
(b) CONDITION 4.2: NO CRACK FOUND.
1) Repeat the Detailed, HFEC and LFEC Inspections of the aft side of the Aft
Pressure Bulkhead (APB) for any crack in accordance with FIGURE 4.
NOTE: It is not required to do the inspections of the aft side of the Aft Pressure
Bulkhead (APB) in areas where a repair covers the affected inspection
zones provided:
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1. The repair is the corrective action to the crack condition
identified in Service Bulletin 737-53A1251 or in Service Bulletin
737-53A1353 and installed after the original issue date of
Service Bulletins 737-53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company
Organization Designation Authorization (ODA) via a FAA Form
8100-9.
3. Close access to the section 48 access and blowout access door refer to 737-600/700/800/900
AMM 52-49-11 as an accepted procedure.
4. Put the airplane back to a serviceable condition.
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### Page 33 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
This Figure applies only to: Group 1.
STA
1016
A-A
CRACKS
TYPICAL)
S-7L  • S-7R
CRACKS
(TYPICAL)
S-15L  •  • S-15R
_ TYPICAL AT 7
1) WEB AREAS
AROUND BULKHEAD
CRACKS/ S-23L
(TYPICAL)  S-23R
FIGURE 1: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS
(SHEET 1 OF 2)
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### Page 34

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
(a)--AFT PRESSURE
BULKHEAD WEBS
Inspect1
(b)--AFT PRESSURE
BULKHEAD WEBS
Inspect2
(c)--AFT PRESSURE
BULKHEAD WEBS
Inspect3
(a) Do a Detailed Inspection on the aft side of the Station (STA) 1016 Aft Pressure Bulkhead (APB) center
dome apex gore webs including the web edges, lap splices and outside lap splices for any crack.
(b) Do a Low Frequency Eddy Current Inspection on the aft side of the Station (STA) 1016 Aft Pressure
Bulkhead (APB) for any crack around all hidden web lap splice fasteners in accordance with 737 NDT
Manual Part 6, 53-10-64.
(c) Do a High Frequency Eddy Current Inspection on the aft side of the Station (STA) 1016 Aft Pressure
Bulkhead (APB) for any crack around the web fasteners in accordance with 737 NDT Manual Part 6, 53-
10-64.
FIGURE 1: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS
(SHEET 2 OF 2)
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FIGURE 2: THIS FIGURE IS DELETED AT REVISION 2
(SHEET 1 OF 1)
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BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
This Figure applies only to: Group 2.
S-7L
ACCESS
DOOR
WEB LAP SPLICE
(7 LOCATIONS)
S-7R
S-15L-
S-23L
AFT PRESSURE BULKHEAD S-23R
2935764
FIGURE 3: AFT PRESSURE BULKHEAD - GENERAL VISUAL INSPECTION
(SHEET 1 OF 3)
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### Page 37 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
BLO
S-7L  „S-7R
S-15L  S-15R
S-23L  S-23R
AFT PRESSURE BULKHEAD
GENERAL VISUAL  INSPECTION  VIEW LOOKING FORWARD
9929862
FIGURE 3: AFT PRESSURE BULKHEAD - GENERAL VISUAL INSPECTION
(SHEET 2 OF 3)
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### Page 38

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
(a)--AFT PRESSURE
BULKHEAD WEBS
Inspect1
(a) Do a General Visual Inspection of the aft side of the Station (STA) 1016 Aft Pressure Bulkhead (APB) for
any repair.
FIGURE 3: AFT PRESSURE BULKHEAD - GENERAL VISUAL INSPECTION
(SHEET 3 OF 3)
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### Page 39 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
This Figure applies only to: Group 2.
BL
S-7L
ACCESS
DOOR
WEB LAP SPLICE
(7 LOCATIONS)
S-7R
S-15L -
S-23L
AFT PRESSURE BULKHEAD
FIGURE 4: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS
(SHEET 1 OF 3)
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### Page 40 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
BL O
S-7L  →S-7R
S-15L  S-15R
S-23L  S-23R
+ FASTENER LOCATIONS  REFERENCE STEP 2 & 3  GORE WEB LAP SPLICES  AFT PRESSURE BULKHEAD
• FASTENER LOCATIONS OUTSIDE  GORE WEB LAP SPLICES  • DETAILED INSPECTION  2935752
REFERENCE STEP 3  VIEW LOOKING FORWARD
FIGURE 4: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS
(SHEET 2 OF 3)
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### Page 41

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
More DataQtyIdentificationNameTaskStep
(a)--AFT PRESSURE
BULKHEAD WEBS
Inspect1
(b)--AFT PRESSURE
BULKHEAD WEBS
Inspect2
(c)--AFT PRESSURE
BULKHEAD WEBS
Inspect3
(a) Do a Detailed Inspection on the aft side of the Station (STA) 1016 Aft Pressure Bulkhead (APB) center
dome apex gore webs including the web edges, lap splices and outside lap splices for any crack.
(b) Do a Low Frequency Eddy Current Inspection on the aft side of the Station (STA) 1016 Aft Pressure
Bulkhead (APB) for any crack around all hidden web lap splice fasteners in accordance with 737 NDT
Manual Part 6, 53-10-64.
(c) Do a High Frequency Eddy Current Inspection on the aft side of the Station (STA) 1016 Aft Pressure
Bulkhead (APB) for any crack around the web fasteners in accordance with 737 NDT Manual Part 6, 53-
10-64.
FIGURE 4: AFT PRESSURE BULKHEAD - WEB LAP SPLICE INSPECTION AREAS
(SHEET 3 OF 3)
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### Page 42

This Appendix applies only to: Group 1.
Logic diagrams are provided as an aid only. Information contained in Paragraph 1.E., Compliance is the primary
source for compliance times. Information contained in Paragraph 3.B., Work Instructions is the primary source
for tasks required for compliance.
1. The table below gives the description for the parts and conditions called out in the logic diagrams.
DescriptionTitle
ANY CRACK FOUND.CONDITION 1
NO CRACK FOUND.CONDITION 2
2. The table below gives the description for the flag notes called out in the logic diagram.
DescriptionFlag Note Letter
It is not required to do the inspections of the aft side of the Aft Pressure
Bulkhead (APB) in areas where a repair covers the affected inspection zones
provided:
(a)
1. The repair is the corrective action to the crack condition identified in
Service Bulletin 737-53A1251 or in Service Bulletin 737-53A1353
and installed after the original issue date of Service Bulletins 737-
53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company Organi-
zation Designation Authorization (ODA) vis a FAA Form 8100-9.
APPENDIX A:  LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE, TABLE 1: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME APEX GORE WEBS
(SHEET 1 OF 2)
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BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
WHICHEVER OCCURS LATER
BEFORE 26,000 TOTAL  FLIGHT CYCLES.  EFFECTIVE DATE OF AD 2005-05-18.  WITHIN 4,000 FLIGHT CYCLES AFTER THE
DO A DETAILED, HIGH FREQUENCY EDDY CURRENT
(HFEC) AND LOW FREQUENCY EDDY CURRENT (LFEC)
INSPECTIONS OF THE AFT SIDE OF THE AFT PRESSURE
BULKHEAD (APB) FOR ANY CRACK.
CONDITION 1  CONDITION 2
BEFORE FURTHER
FLIGHT
CONDITION 1 (ACTION 1):
CONTACT THE BOEING COMPANY
FOR REPAIR INSTRUCTIONS AND
DO THE REPAIR.
NOT TO EXCEED 4,000
FLIGHT CYCLES
CONDITION 1 (ACTION 2): REPEAT THE
DETAILED, HIGH FREQUENCY EDDY
CURRENT (HFEC) AND LOW
FREQUENCY EDDY CURRENT (LFEC)
INSPECTIONS OF THE AFT SIDE OF
THE AFT PRESSURE BULKHEAD (APB)
FOR ANY CRACK.
(a)
NOT TO EXCEED 4,000
FLIGHT CYCLES
REPEAT THE DETAILED, HIGH
FREQUENCY EDDY CURRENT (HFEC)
AND LOW FREQUENCY EDDY CURRENT
(LFEC) INSPECTIONS OF THE AFT SIDE
OF THE AFT PRESSURE BULKHEAD (APB)
FOR ANY CRACK
2935760
APPENDIX A: LOGIC DIAGRAM FOR PARAGRAPH 1.., COMPLIANCE, TABLE 1: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME АРЕХ GORE WEBS
(SHEET 2 OF 2)
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### Page 44

This Appendix applies only to: Group 2.
Logic diagrams are provided as an aid only. Information contained in Paragraph 1.E., Compliance is the primary
source for compliance times. Information contained in Paragraph 3.B., Work Instructions is the primary source
for tasks required for compliance.
1. The table below gives the description for the parts and conditions called out in the logic diagrams.
DescriptionTitle
ANY REPAIR FOUND.CONDITION 3
ANY CRACK FOUND.CONDITION 3.1
NO CRACK FOUND.CONDITION 3.2
NO REPAIR FOUND.CONDITION 4
ANY CRACK FOUND.CONDITION 4.1
NO CRACK FOUND.CONDITION 4.2
2. The table below gives the description for the flag notes called out in the logic diagram.
DescriptionFlag Note Letter
Condition 3 (Action 1) is not required for any repair found during the General
Visual Inspection (GVI) of the aft side of the Aft Pressure Bulkhead (APB) in
areas where a repair covers the affected inspection zones provided that the
installed repair was approved by The Boeing Company Organization Desig-
nation Authorization (ODA) via a FAA Form 8100-9 and inspections are ac-
complished in accordance with the scheduled repair approval listed on the
FAA Form 8100-9.
(a)
It is not required to do the inspections of the aft side of the Aft Pressure
Bulkhead (APB) in areas where a repair covers the affected inspection zones
provided:
(b)
1. The repair is the corrective action to the crack condition identified in
Service Bulletin 737-53A1251 or in Service Bulletin 737-53A1353
and installed after the original issue date of Service Bulletins 737-
53-1251 or 737-53A1353, AND
2. The installed repair was approved by The Boeing Company Organi-
zation Designation Authorization (ODA) vis a FAA Form 8100-9.
APPENDIX B:  LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE, TABLE 2: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME APEX GORE WEBS
(SHEET 1 OF 4)
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BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
WHICHEVER OCCURS LATER
WITHIN 4,000 FLIGHT
BEFORE 23,000 TOTAL  CYCLES AFTER THE
FLIGHT CYCLES.  REVISION 1 DATE
OF THIS SERVICE
BULLETIN.
DO A GENERAL VISUAL INSPECTION OF THE
AFT SIDE OF THE AFT PRESSURE
BULKHEAD (APB) FOR ANY REPAIR.
CONDITION 3  CONDITION 4
WHICHEVER OCCURS LATER  WHICHEVER OCCURS LATER
BEFORE 23,000 TOTAL  FLIGHT CYCLES.  WITHIN 4,000 FLIGHT  CYCLES AFTER THE  REVISION 1 DATE  BEFORE 23,000 TOTAL  FLIGHT CYCLES.  WITHIN 4,000 FLIGHT  CYCLES AFTER THE  REVISION 1 DATE
OF THIS SERVICE  OF THIS SERVICE
BULLETIN.  BULLETIN.
CONDITION 3 (ACTION 1): CONTACT THE BOEING
COMPANY FOR ALTERNATIVE INSPECTION(S)
TO THIS SERVICE BULLETIN, AND DO THE
INSPECTION(S) AND APPLICABLE
ON-CONDITION ACTION(S).
DO A DETAILED, HIGH FREQUENCY EDDY
CURRENT (HFEC) AND LOW FREQUENCY
EDDY CURRENT (LFEC) INSPECTIONS OF
THE AFT SIDE OF THE AFT PRESSURE
BULKHEAD (APB) FOR ANY CRACK.
CONDITION 3 (ACTION 2):
DO A DETAILED, HIGH FREQUENCY
EDDY CURRENT (HFEC) AND LOW
FREQUENCY EDDY CURRENT (LFEC)
INSPECTIONS OF THE AFT SIDE OF
THE AFT PRESSURE BULKHEAD (APB)
FOR ANY CRACK AT THE UNREPAIRED
AREAS.
B
2935781
APPENDIX B: LOGIC DIAGRAM FOR PARAGRAPH 1.., COMPLIANCE, TABLE 2: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME АРЕХ GORE WEBS
(SHEET 2 OF 4)
Original Issue: June 03, 2004
Revision 2 January 20, 2021  Export Controlled ECCN: 9E991 - BOEING  737-53A1251
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.  45 of 47

### Page 46 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
CONDITION 3.1
BEFORE FURTHER
FLIGHT
CONDITION 3.1 (ACTION 1):
CONTACT THE BOEING COMPANY
FOR REPAIR INSTRUCTIONS AND
DO THE REPAIR.
NOT TO EXCEED 4,000
FLIGHT CYCLES
CONDITION 3.1 (ACTION 2): REPEAT
THE DETAILED, HIGH FREQUENCY
EDDY CURRENT (HFEC) AND LOW
FREQUENCY EDDY CURRENT (LFEC)
INSPECTIONS OF THE AFT SIDE OF
THE AFT PRESSURE BULKHEAD
(APB) FOR ANY CRACK AT THE
UNREPAIRED AREAS.
(b)
CONDITION 3.2
NOT TO EXCEED 4,000
FLIGHT CYCLES
REPEAT THE DETAILED, HIGH
FREQUENCY EDDY CURRENT (HFEC)
AND LOW FREQUENCY EDDY CURRENT
(LFEC) INSPECTIONS OF THE AFT SIDE
OF THE AFT PRESSURE BULKHEAD (APB)
FOR ANY CRACK AT THE UNREPAIRED
AREAS.
2935782
APPENDIX B: LOGIC DIAGRAM FOR PARAGRAPH 1.E., COMPLIANCE, TABLE 2: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME АРЕХ GORE WEBS
(SHEET 3 OF 4)
Original Issue: June 03, 2004
Revision 2 January 20, 2021  PROPRIETARY - Copyright © Unpublished  Export Controlled ECCN: 9E991 - BOEING  737-53A1251
Work - See page 1 for details.  46 of 47

### Page 47 (OCR)

BOEING SERVICE BULLETIN 737-53A1251
ALERT  ALERT
CONDITION 4.1  CONDITION 4.2
BEFORE FURTHER
FLIGHT
CONDITION 4.1 (ACTION 1):
CONTACT THE BOEING COMPANY
FOR REPAIR INSTRUCTIONS AND
DO THE REPAIR.
NOT TO EXCEED 4,000
FLIGHT CYCLES
CONDITION 4.1 (ACTION 2): REPEAT
THE DETAILED, HIGH FREQUENCY
EDDY CURRENT (HFEC) AND LOW
FREQUENCY EDDY CURRENT (LFEC)
INSPECTIONS OF THE AFT SIDE OF
THE AFT PRESSURE BULKHEAD
(APB) FOR ANY CRACK.  (0)
NOT TO EXCEED 4,000
FLIGHT CYCLES
REPEAT THE DETAILED, HIGH
FREQUENCY EDDY CURRENT (HFEC) AND
LOW FREQUENCY EDDY CURRENT (LFEC)
INSPECTIONS OF THE AFT SIDE OF THE
AFT PRESSURE BULKHEAD (APB)
FOR ANY CRACK.  (b)
2935783
APPENDIX B: LOGIC DIAGRAM FOR PARAGRAPH 1.., COMPLIANCE, TABLE 2: INSPECTION OF AFT
PRESSURE BULKHEAD CENTER DOME АРЕХ GORE WEBS
(SHEET 4 OF 4)
Original Issue: June 03, 2004
Revision 2 January 20, 2021  Export Controlled ECCN: 9E991 - BOEING  737-53A1251
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.  47 of 47

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