# Boeing Alert Service Bulletin 737-53A1248: Revision 2

- Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2016-6901; AD 2016-18-15 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication.
- Document: [Boeing Alert Service Bulletin 737-53A1248](https://openairdocs.org/service-documents/boeing/737-53a1248.md)
- Title as filed: SB-737-53A1248 R2
- Pages: 40
- PDF: https://openairdocs.org/files/sha256/2d/12/2d120f12ccb90ea8893e4590a96937a3912e7e4aa52b67c40bbadc66ba62a077
- Page: https://openairdocs.org/service-documents/boeing/737-53a1248/file/2d120f12ccb9

## Text

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### Page 1

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-53A1248
Original Issue: September 09, 2004
Revision 2: October 14, 2015
ATA System: 5311
SUBJECT: FUSELAGE - Body Station 1016 Aft Pressure Bulkhead Web - Inspection for Web
Cracks at the Y-Chord
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Unpublished Work.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: September 09, 2004
737-53A1248Revision 2: October 14, 2015
1 of 40
4.0

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Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: September 09, 2004
737-53A1248Revision 2: October 14, 2015
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BOEING SERVICE BULLETIN 737-53A1248
ALERTALERT
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Table of Contents
Revision Transmittal Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
E. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
H. Weight and Balance Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1. Existing Data: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2. Data Supplied with this Service Bulletin: . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3. Installation Drawings Used in the Preparation of this Service Bulletin: . . . . . . . . . . . 25
K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
M. Software Accomplishment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
C. Parts Necessary for Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1. Kits/Parts: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2. Parts and Materials Supplied by the Operator: . . . . . . . . . . . . . . . . . . . . . . . . 27
3. Parts Modified and Reidentified: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4. Parts Removed and Not Replaced: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 27
3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
FIGURE 1: LFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
FIGURE 2: HFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
FIGURE 3: HFEC, LFEC AND DETAILED INSPECTION OF WEB AT "Y" CHORD - BELOW S-15L AND
S-15R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: September 09, 2004
737-53A1248Revision 2: October 14, 2015
3 of 40
BOEING SERVICE BULLETIN 737-53A1248
ALERTALERT

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Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: September 09, 2004
737-53A1248Revision 2: October 14, 2015
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ALERTALERT
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Commercial 
Airplanes
737
Service Bulletin
ALERT
Revision Transmittal SheetNumber: 737-53A1248Original Issue: September 09, 2004
Revision 2: October 14, 2015
ATA System: 5311
SUBJECT: FUSELAGE - Body Station 1016 Aft Pressure Bulkhead Web - Inspection for Web
Cracks at the Y-Chord
This revision includes all pages of the service bulletin.
COMPLIANCE INFORMATION RELATED TO THIS REVISION
More work is necessary on airplanes inspected in accordance with Revision 1 or the Original Issue of this service
bulletin. Do repeat inspections in accordance with Paragraph 1.E., Compliance of this service bulletin.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2005-21-06 is related to this service bulletin.
REASON FOR REVISION
This revision is sent to change the repeat inspection intervals after the initial inspection threshold.
The data given in Alternative Method of Compliance Notice 737-53A1248 AMOC 01 is included in this revision.
These sections were changed:
1. Summary, Background - added Service Related Problem (SRP) reference, Widespread Fatigue Damage
(WFD) statement, and Summary Evaluation table.
2. Summary, Action - revised inspection requirements to include corrosion as specified in AD 2005-21-06.
3. Summary, Compliance - added additional Airworthiness Directive statement, and added the effective
date of AD 2005-21-06.
4. Paragraph 1.C., Reason - added SRP reference and AMOC incorporation statement.
5. Paragraph 1.D., Description - revised inspection requirements to include corrosion as specified in AD
2005-21-06, and added Affected Maintenance Zones table.
6. Paragraph 1.E., Compliance - added additional Airworthiness Directive statement, added the effective
date of AD 2005-21-06, and revised the compliance table to change the repeat inspection intervals
after the initial inspection threshold.
7. Paragraph 1.F., Approval - updated approval paragraphs.
8. Paragraph 1.G., Manpower - added footnote to Task Hour table.
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9. Paragraph 1.J., References - updated references.
10. Paragraph 1.K.2, Damage Tolerance Based Structural Inspections - added Damage Tolerance
Inspections (DTI) statement.
11. Paragraph 3.A., General Information - added notes.
12. Paragraph 3.B., Work Instructions - revised inspection requirements to include corrosion as specified
in AD 2005-21-06, reformatted instructions, and revised FIGURE 1 through FIGURE 3 Step Tables.
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
September 09, 2004Original Issue:
September 10, 2007Revision 1:
October 14, 2015Revision 2:
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ALERTALERT

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Commercial 
Airplanes
737
Service Bulletin
ALERT
SummaryNumber: 737-53A1248Original Issue: September 09, 2004
Revision 2: October 14, 2015
ATA System: 5311
SUBJECT: FUSELAGE - Body Station 1016 Aft Pressure Bulkhead Web - Inspection for Web
Cracks at the Y-Chord
THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH
1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OWNER.
CONCURRENT REQUIREMENTS
None.
BACKGROUND
Cracks have been reported in the aft pressure bulkhead web on numerous 737-200/-300 airplanes inspected
as shown in service bulletin 737-53A1214. In all of the cases, the cracks ran in the circumferential direction
along the aft row of fasteners connecting the web assembly to the bulkhead "Y" chord. These cracks occurred
in the S-6L and S-6R areas. The 737-600/700/700C/800/900 airplanes have a similar structure for the aft pressure
bulkhead and could experience the same type of fatigue damage. If cracks are allowed to continue undetected
the airplane could have an uncontrolled decompression.
The aft pressure bulkhead has been determined to be structure that is susceptible to Widespread Fatigue
Damage (WFD).
The Federal Aviation Administration (FAA) has issued Airworthiness Directive AD 2005-21-06 which requires
incorporation of this service bulletin.
Boeing Service Related Problem (SRP) 737NG-SRP-53-0183 and 737NG-SRP-53-0473 are related to this
service bulletin.
The data given in Alternative Method of Compliance Notice 737-53A1248 AMOC 01 is included in this revision.
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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
Get access to the aft side of the aft pressure bulkhead and do a Low Frequency Eddy Current (LFEC) and
Detailed Inspection for circumferential cracks in the web where it attaches to the "Y" chord along the aft row of
fasteners.
As an option to doing an inspection from the aft side of the bulkhead, it is acceptable to do a High Frequency
Eddy Current (HFEC) and Detailed Inspection from the forward side of the bulkhead.
When performing an inspection from the aft side, if either a crack, crack indication, discrepant fastener hole, or
corrosion is found, you must get access to the forward side of the bulkhead and do an HFEC and a Detailed
Inspection to inspect for cracks from the forward side. Do the HFEC inspection for circumferential cracks along
the aft row of fasteners at the "Y" chord for the section of web where the crack, crack indication, discrepant
fastener hole, or corrosion was found. It is not necessary to do the HFEC inspection beyond the web splices of
the web section containing the crack, crack indication, discrepant fastener hole, or corrosion. Do the Detailed
Inspection for cracks in the web and for incorrectly drilled or elongated fastener holes. At the crack indication
fastener location(s), remove the fastener(s) and do an HFEC open hole inspection. Refer to Maintenance
Planning Document (MPD) section 9 for additional inspection requirements.
Repeat inspections may be performed from either the aft or forward side of the aft pressure bulkhead at the
times indicated in Paragraph 1.E., Compliance.
If any crack, crack indication, discrepant fastener hole, or corrosion is found, repair before further flight.
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Contact The Boeing Company for repair instructions and do the repair.
NOTE: When contacting Boeing for repair instructions, give the size and location of the damage. When possible,
send sketches and photographs. If the damage includes corrosion, send data on the length, width and
largest depth of the clean up.
Send to:
BOEING COMMERCIAL AIRPLANES GROUP
ATTENTION: MANAGER, AIRLINE SUPPORT
EFFECTIVITY
737-600/-700/-700C/-800/-900 airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes.
COMPLIANCE
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.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2005-21-06 is related to this service bulletin.
The effective date of AD 2005-21-06 is November 25, 2005.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION
Boeing warranty remedies are not available for the inspection given in this service bulletin.
MANPOWER
Refer to Paragraph 1.G., Manpower.
MATERIAL INFORMATION
None.
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BOEING SERVICE BULLETIN 737-53A1248
ALERT  ALERT
BL
ACCESS DOOR  5-71-  →S-7R
S-15L -  ~S-15R
"Y" CHORD
A-A
FRAME  VIEW LOOKING FORWARD
CHORD
- WEB
INSPECT THE WEB ALONG THE AFT ROW OF
FASTENERS AND ALONG THE EDGE OF THE
"Y" CHORD USING EDDY CURRENT AND
VISUAL INSPECTION
FWD
B—B  N71435
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Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-53A1248
Original Issue: September 09, 2004
Revision 2: October 14, 2015
ATA System: 5311
SUBJECT: FUSELAGE - Body Station 1016 Aft Pressure Bulkhead Web - Inspection for Web
Cracks at the Y-Chord
THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH
1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO
THE NEW OWNER.
1.    PLANNING INFORMATION
A. Effectivity
1. Airplanes
This service bulletin is applicable to 737-600/-700/-700C/-800/-900 airplanes, line numbers 1 -
1755 in 1 Group(s). The Variable Numbers and Group Information for the applicable airplanes is
given below.
Refer to Service Bulletin Index D6-19567 Part 3 for Airplane Variable Number, Line Number, and
Serial Number data.
DESCRIPTIONCONFIGURATIONGROUP
737-600, -700, -700C, -800, -900 airplanes, line numbers 1 - 1755-1
Airplane Models:
737-600, 737-700, 737-700C, 737-800, 737-900
GroupVariable Number
1YA001 - YA099
1YA101 - YA199
1YA201 - YA211
1YA221
1YA231 - YA242
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GroupVariable Number
1YA251 - YA256
1YA271 - YA272
1YA291
1YA301 - YA302
1YA311 - YA314
1YA321 - YA323
1YA336 - YA345
1YA351
1YA356 - YA357
1YA366 - YA367
1YA371 - YA377
1YA501 - YA536
1YA541 - YA552
1YA571 - YA578
1YA601 - YA615
1YA621 - YA622
1YA626 - YA631
1YA635 - YA636
1YA641 - YA642
1YA645 - YA650
1YA656 - YA659
1YA666 - YA667
1YA671 - YA672
1YA681 - YA691
1YA701 - YA710
1YA721 - YA722
1YA731 - YA734
1YA751 - YA756
1YA801 - YA803
1YA809
1YA811 - YA814
1YA831 - YA835
1YA841 - YA862
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GroupVariable Number
1YA881 - YA882
1YA891 - YA892
1YA961 - YA976
1YB001 - YB006
1YB101 - YB132
1YB151 - YB153
1YB156 - YB157
1YB161 - YB164
1YB171 - YB172
1YB181 - YB184
1YB201 - YB208
1YB271
1YB276
1YB301 - YB310
1YB371 - YB381
1YB501 - YB502
1YB521 - YB526
1YB541 - YB544
1YB551
1YB561 - YB574
1YB576 - YB577
1YB581 - YB587
1YB601 - YB632
1YB651
1YB656
1YB851 - YB863
1YB871 - YB873
1YB881 - YB888
1YB901 - YB903
1YB911
1YC001 - YC030
1YC051 - YC083
1YC091 - YC094
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GroupVariable Number
1YC101 - YC104
1YC111 - YC113
1YC121
1YC126 - YC127
1YC136 - YC141
1YC146 - YC147
1YC151 - YC156
1YC166 - YC171
1YC176 - YC178
1YC186 - YC189
1YC201 - YC203
1YC206 - YC207
1YC301 - YC305
1YC321 - YC386
1YC391 - YC394
1YC396
1YC401 - YC417
1YC421 - YC422
1YC426 - YC428
1YC436 - YC437
1YC441 - YC448
1YC451 - YC455
1YC459
1YC461 - YC467
1YC471 - YC499
1YC501 - YC526
1YC571 - YC583
1YC587 - YC589
1YC591 - YC593
1YC601 - YC655
1YC681 - YC696
1YC701 - YC715
1YC720 - YC725
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GroupVariable Number
1YC727 - YC741
1YC751 - YC752
1YC761 - YC770
1YC781 - YC793
1YC801 - YC892
1YC901 - YC907
1YC921 - YC922
1YC931 - YC932
1YC941 - YC951
1YC971 - YC978
1YC981 - YC983
1YD001 - YD007
1YD021 - YD025
1YD041 - YD057
1YD081 - YD084
1YD101 - YD108
1YD121 - YD126
1YD151 - YD159
1YD171 - YD172
1YD201 - YD203
1YD206 - YD209
1YD216 - YD219
1YD251 - YD254
1YD256 - YD257
1YD261
1YD301 - YD334
1YD391
1YD401 - YD410
1YD412
1YD481 - YD485
1YD491
1YD501 - YD512
1YD531 - YD535
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GroupVariable Number
1YD541 - YD547
1YD561 - YD564
1YD571 - YD572
1YD591 - YD595
1YD601 - YD612
1YD651 - YD653
1YE001 - YE020
1YE051
1YE101 - YE109
1YE151 - YE157
1YE171 - YE172
1YE201 - YE206
1YE301 - YE305
1YE321 - YE326
1YG001 - YG044
1YG061 - YG064
1YG066 - YG089
1YG091
1YG201
1YG211
1YG501 - YG508
1YG601 - YG602
1YJ001 - YJ004
1YJ011 - YJ013
1YJ021
1YJ471 - YJ480
1YJ501 - YJ517
1YJ531 - YJ546
1YJ591 - YJ594
1YJ631 - YJ632
1YJ671 - YJ682
1YJ801 - YJ853
1YJ861 - YJ867
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GroupVariable Number
1YJ871
1YJ901 - YJ902
1YJ911 - YJ923
1YJ931 - YJ936
1YJ941 - YJ943
1YK001 - YK007
1YK101 - YK104
1YK111 - YK112
1YK121 - YK122
1YK131 - YK132
1YK136 - YK137
1YK301 - YK304
1YK321 - YK330
1YK361 - YK366
1YK401 - YK406
1YK426 - YK427
1YK431 - YK432
1YK456 - YK460
1YK480 - YK484
1YK511 - YK512
1YK601
1YM101 - YM103
1YM201 - YM204
1YM251 - YM267
1YM471
1YM481 - YM482
1YM521
1YM541
1YM551
2. Spares Affected
None.
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B. Concurrent Requirements
None.
C. Reason
Cracks have been reported in the aft pressure bulkhead web on numerous 737-200/-300 airplanes
inspected as shown in service bulletin 737-53A1214. In all of the cases, the cracks ran in the
circumferential direction along the aft row of fasteners connecting the web assembly to the bulkhead
"Y" chord. These cracks occurred in the S-6L and S-6R areas. The 737-600/700/700C/800/900 airplanes
have a similar structure for the aft pressure bulkhead and could experience the same type of fatigue
damage. If cracks are allowed to continue undetected the airplane could have an uncontrolled
decompression.
The Federal Aviation Administration (FAA) has issued Airworthiness Directive AD 2005-21-06 which
requires incorporation of this service bulletin.
Boeing Service Related Problem (SRP) 737NG-SRP-53-0183 and 737NG-SRP-53-0473 are related
to this service bulletin.
Revision 1 was sent to limit effectivity of the service bulletin to line numbers 1 through 1755. Airplanes
produced after line number 1755 have a thicker aft pressure bulkhead gore web and are therefore not
included in the effectivity of this service bulletin. Note: Refer to the Maintenance Planning Data Document
(MPD) section 9 for additional inspection requirements.
Revision 2 is sent to change the repeat inspection intervals after the initial inspection threshold.
The data given in Alternative Method of Compliance Notice 737-53A1248 AMOC 01 is included in this
revision.
D. Description
Get access to the aft side of the aft pressure bulkhead and do a Low Frequency Eddy Current (LFEC)
and Detailed Inspection for circumferential cracks in the web where it attaches to the "Y" chord along
the aft row of fasteners.
As an option to doing an inspection from the aft side of the bulkhead, it is acceptable to do a High
Frequency Eddy Current (HFEC) and Detailed Inspection from the forward side of the bulkhead.
When performing an inspection from the aft side, if either a crack, crack indication, discrepant fastener
hole, or corrosion is found, you must get access to the forward side of the bulkhead and do an HFEC
and a Detailed Inspection to inspect for cracks from the forward side. Do the HFEC inspection for
circumferential cracks along the aft row of fasteners at the "Y" chord for the section of web where the
crack, crack indication, discrepant fastener hole, or corrosion was found. It is not necessary to do the
HFEC inspection beyond the web splices of the web section containing the crack, crack indication,
discrepant fastener hole, or corrosion. Do the Detailed Inspection for cracks in the web and for incorrectly
drilled or elongated fastener holes. At the crack indication fastener location(s), remove the fastener(s)
and do an HFEC hole inspection. Refer to Maintenance Planning Document (MPD) section 9 for
additional inspection requirements.
Repeat inspections may be performed from either the aft or forward side of the aft pressure bulkhead
at the times indicated in Paragraph 1.E., Compliance.
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If any crack, crack indication, discrepant fastener hole, or corrosion is found, repair before further flight.
Contact The Boeing Company for repair instructions and do the repair.
NOTE: When contacting Boeing for repair instructions, give the size and location of the damage.
When possible, send sketches and photographs. If the damage includes corrosion, send data
on the length, width and largest depth of the clean up.
Send to:
BOEING COMMERCIAL AIRPLANES GROUP
ATTENTION: MANAGER, AIRLINE SUPPORT
Revision 2 - More work is necessary on airplanes inspected in accordance with Revision 1 or the
Original Issue of this service bulletin. Do repeat inspections in accordance with Paragraph 1.E.,
Compliance of this service bulletin.
The work in this service bulletin is done in the maintenance zone(s) given below.
Affected Maintenance Zones
ZoneModel
145, 146, 241, 242, 311, 312737-600, 737-700, 737-700C,
737-800, 737-900
E. Compliance
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.
Federal Aviation Administration (FAA) Airworthiness Directive AD 2005-21-06 is related to this service
bulletin. The effective date of AD 2005-21-06 is November 25, 2005.
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.
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Do the required actions in accordance with Paragraph 3. Accomplishment Instructions.
NOTE: "Discrepant fastener holes" are defined as holes that are incorrectly drilled or elongated.
Table 1: Inspection for cracks of aft pressure bulkhead Web at "Y" Chord - Above S-15L and S-15R
Repeat Interval (Not to Exceed)Compliance
Time
ActionCondition
--Do one of the options that
follow:
All airplanes.
OPTION 1:
-Before 25,000
total flight cy-
cles.
Do an LFEC and detailed
inspection of the aft side of
the aft pressure bulkhead
in accordance with Part I,
OPTION 1. (a)
OPTION 2:
-Before 25,000
total flight cy-
cles.
Do an HFEC and detailed
inspection of the forward
side of the aft pressure
bulkhead in accordance
with Part I, OPTION 2.
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Table 1: Inspection for cracks of aft pressure bulkhead Web at "Y" Chord - Above S-15L and S-15R
Repeat Interval (Not to Exceed)Compliance
Time
ActionCondition
-Before further
flight.
ACTION 1:
Contact The Boeing Com-
pany for repair instructions
and do the repair.
If any crack, crack
indication, dis-
crepant fastener
hole, or corrosion
is found. --ACTION 2:
Do one of the options that
follow:
OPTION 1:
1,200 flight cy-
cles from last
LFEC inspec-
tion.
Inspections at S-5L to S-
7L and S-5R to S-9R.
-On areas that are not re-
paired, do repeat LFEC
and detailed inspections of
the aft side of the aft pres-
sure bulkhead in accor-
dance with Part I, OPTION
1. (a)
6,000 flight cy-
cles from last
LFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with less
than 65,000 total flight
cycles.
2,700 flight cy-
cles from last
LFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with 65,000
or more total flight cycles.
OPTION 2:
3,800 flight cy-
cles from last
HFEC inspec-
tion.
Inspections at S-5L to S-
7L and S-5R to S-9R.
-On areas that are not re-
paired, do repeat HFEC
and detailed inspections of
the forward side of the aft
pressure bulkhead in accor-
dance with Part I, OPTION
2.
12,000 flight cy-
cles from last
HFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with less
than 65,000 total flight
cycles.
5,650 flight cy-
cles from last
HFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with 65,000
or more total flight cycles.
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Table 1: Inspection for cracks of aft pressure bulkhead Web at "Y" Chord - Above S-15L and S-15R
Repeat Interval (Not to Exceed)Compliance
Time
ActionCondition
--Do one of the options that
follow:
If no crack, crack
indication, dis-
crepant fastener
hole, or corrosion
is found.
OPTION 1:
1,200 flight cy-
cles from last
LFEC inspec-
tion.
Inspections at S-5L to S-
7L and S-5R to S-9R.
-Do repeat LFEC and de-
tailed inspections of the aft
side of the aft pressure
bulkhead in accordance
with Part I, OPTION 1. (a) 6,000 flight cy-
cles from last
LFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with less
than 65,000 total flight
cycles.
2,700 flight cy-
cles from last
LFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with 65,000
or more total flight cycles.
OPTION 2:
3,800 flight cy-
cles from last
HFEC inspec-
tion.
Inspections at S-5L to S-
7L and S-5R to S-9R.
-Do repeat HFEC and de-
tailed inspections of the
forward side of the aft
pressure bulkhead in accor-
dance with Part I, OPTION
2. 12,000 flight cy-cles from last
HFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with less
than 65,000 total flight
cycles.
5,650 flight cy-
cles from last
HFEC inspec-
tion.
Inspections above S-15L
and S-15R EXCEPT S-5L
to S-7L and S-5R to S-9R
on airplanes with 65,000
or more total flight cycles.
(a) If a crack, crack indication, discrepant fastener hole, or corrosion is found, you must do an HFEC inspection
from the forward side. Do the HFEC inspection for cracks in the section of web where the crack was
found. It is not necessary to do the HFEC inspection beyond the web splices of the web section containing
the crack, crack indication, discrepant fastener hole, or corrosion.
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Table 2: Inspection for cracks of aft pressure bulkhead Web at "Y" Chord - Below S-15L and S-15R
Repeat Interval (Not to Exceed)Compliance
Time
ActionCondition
-Before 65,000
total flight cy-
cles.
Do an HFEC and detailed
inspection of the forward
side, and an LFEC and de-
tailed inspection of the aft
side of the aft pressure
bulkhead in accordance
with Part II. (a)
All airplanes.
-Before further
flight.
ACTION 1:
Contact The Boeing Com-
pany for repair instructions
and do the repair.
If any crack, crack
indication, dis-
crepant fastener
hole, or corrosion
is found. 2,700 flight cy-
cles.
Aft side inspections.-ACTION 2:
On areas that are not re-
paired, do repeat HFEC
and detailed inspections of
the forward side, and re-
peat LFEC and detailed in-
spections of the aft side of
the aft pressure bulkhead
in accordance with Part II.
(a)
5,650 flight cy-
cles.
Forward side inspections.
2,700 flight cy-
cles.
Aft side inspections.-Do repeat HFEC and de-
tailed inspections of the
forward side, and repeat
LFEC and detailed inspec-
tions of the aft side of the
aft pressure bulkhead in
accordance with Part II. (a)
If no crack, crack
indication, dis-
crepant fastener
hole, or corrosion
is found.
5,650 flight cy-
cles.
Forward side inspections.
(a) In many areas the access is limited and you can do an inspection from only one side: either the forward
side (HFEC) or the aft side (LFEC). In these areas, do the inspection from the side which provides access.
Perform repeat inspections accordingly.
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.
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The Manager, Seattle Aircraft Certification Office, FAA, approves accomplishment of the inspection
methods defined in Paragraph 1.E., Compliance, Tables 1 and 2, of SB 737-53A1248, Revision 2 as
an alternative method of compliance to the corresponding requirements of paragraph (f) of AD
2005-21-06. All provisions of AD 2005-21-06 that are not specifically referenced in the above statement
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.
Elapsed HoursTask HoursNumber of
Persons
Task
13.026.02Open Access (a)
1.753.52Figure 1
2.254.52Figure 2
2.04.02Figure 3
16.032.02Close Access (a)
3570TOTAL FOR EACH AIRPLANE
(a) These tasks apply only to Paragraph 3. Accomplishment Instructions,
PART I, OPTION 2 and PART II.
H. Weight and Balance Changes
None.
I. Electrical Load Data
Not changed.
J. References
1. Existing Data:
a. Boeing Service Bulletin 737-21-1149, 737-53A1214
b. Boeing Service Letter 737-SL-51-042
c. Boeing Service Related Problem (SRP) 737NG-SRP-53-0183, 737NG-SRP-53-0473
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d. Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2005-21-06
e. Service Bulletin Index D6-19567
f. Standard Overhaul Practices Manual (SOPM) 20-50-01
g. Standard Wiring Practices Manual (SWPM) 20-10-11, 20-10-12, 20-10-19
h. 737 Non-Destructive Testing (NDT) Manual Part 6, 51-00-00 Procedure 4, 16, or 23, Part 6,
53-10-54
i. 737-600/700/800/900 Aircraft Maintenance Manual (AMM) 25-31-41, 25-31-61, 25-40-18,
25-40-19, 38-11-01
j. 737 Structural Repair Manual (SRM) Chapter 51
k. 737-600 Structural Repair Manual (SRM) 51-40-02
l. 737-700 Structural Repair Manual (SRM) 51-40-02
m. 737-700CONV Structural Repair Manual (SRM) 51-40-02
n. 737-700IGW (BBJ) Structural Repair Manual (SRM) 51-40-02
o. 737-800 Structural Repair Manual (SRM) 51-40-02
p. 737-900 Structural Repair Manual (SRM) 51-40-02
q. 737-900ER Structural Repair Manual (SRM) 51-40-02
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
1016
148A2280
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.
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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 but no new DTIs are necessary.
L. Interchangeability and Intermixability of Parts
None.
M. Software Accomplishment Summary
Not affected.
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2.    MATERIAL INFORMATION
A. Material - Price and Availability
None.
B. Industry Support Information
Boeing warranty remedies are not available for the inspection 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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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 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).
— Values for electrical maintenance tasks are included in Chapter 20 of
Standard Wiring Practices Manual (SWPM).
— Non-standard torque values for maintenance tasks are included in the
applicable installation step.
4. Use the approved fastener, process and material substitutions in accordance with
SRM Chapter 51.
5. Refer to the SWPM 20-10-11 and SWPM 20-10-12 for the wire installation procedures,
and SWPM 20-10-19 for the wire separation requirements, as accepted procedures.
6. 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. Refer to SOPM 20-50-01 for alternate
full threaded fasteners (screws) needed for installation in this service bulletin.
7. A Detailed Inspection is defined as: An intensive examination of a specific item,
installation, or assembly to detect damage, failure, or irregularity. Available lighting
is normally supplemented with a direct source of good lighting at an intensity deemed
appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be
necessary. Surface cleaning and elaborate procedures may be required.
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8. These work instructions refer to procedures included in other Boeing documents.
When the words "refer to" are used and the operator has an accepted alternative
procedure, the accepted alternative procedure can be used. When the words "in
accordance with" are included in the instruction, the procedure in the Boeing document
must be used.
9. 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.
10. 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.
11. 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.
12. The compliance times for the actions in Paragraph 3.B., WORK INSTRUCTIONS
are in Paragraph 1.E., Compliance.
B. WORK INSTRUCTIONS
PART I - INSPECTION OF THE WEB AT THE "Y" CHORD ABOVE S-15L AND S-15R
1. Do one of the options that follow:
NOTE: "Discrepant fastener holes" are defined as holes that are incorrectly drilled or elongated.
OPTION 1:
a. Do an LFEC and Detailed Inspection from the aft side of the aft pressure bulkhead web in
accordance with FIGURE 1.
NOTE: As an option to doing the LFEC and Detailed Inspection from the aft side of the aft
pressure bulkhead, you can do an HFEC and Detailed Inspection of the aft pressure
bulkhead web from the forward side of the aft pressure bulkhead in accordance with
PART I, OPTION 2.
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b. If any crack, crack indication, discrepant fastener hole, or corrosion is found:
(1) Get access to the forward side of the aft pressure bulkhead and do an HFEC and Detailed
Inspection on the section of web where the crack, crack indication, discrepant fastener
hole, or corrosion was found. Do the inspection in accordance with FIGURE 2 except the
inspection can be limited to only the section of web with the damage. It is not necessary
to do the inspection beyond the web splices of the web section containing the damage.
At the crack indication fastener location(s), remove the fastener(s) and perform an HFEC
hole inspection in accordance with 737 NDT Manual Part 6, 51-00-00, Procedure 16.
(2) If any crack, crack indication, discrepant fastener hole, or corrosion is found:
(a) ACTION 1: Contact The Boeing Company for repair instructions and do the repair.
(b) ACTION 2: On areas that are not repaired, perform repeat inspections in accordance
with PART I, OPTION 1 at the times specified in Paragraph 1.E., Compliance .
c. If no crack, crack indication, discrepant fastener hole, or corrosion is found, perform repeat
inspections in accordance with PART I, OPTION 1 at the times specified in Paragraph 1.E.,
Compliance.
d. Put the airplane back to a serviceable condition.
OPTION 2:
a. Open access to the forward side of the aft pressure bulkhead by removing these items as
follows:
(1) Remove/keep the galley. Refer to 737-600/700/800/900 AMM 25-31-41 and
737-600/700/800/900 AMM 25-31-61 as accepted procedures.
(2) Remove/keep the lavatory. Refer to 737-600/700/800/900 AMM 25-40-18 and
737-600/700/800/900 AMM 25-40-19 as accepted procedures.
b. Do an HFEC and Detailed Inspection from the forward side of the aft pressure bulkhead in
accordance with FIGURE 2.
c. If any crack, crack indication, discrepant fastener hole, or corrosion is found:
(1) ACTION 1: Contact The Boeing Company for repair instructions and do the repair.
(2) ACTION 2: On areas that are not repaired, perform repeat inspections in accordance
with PART I, OPTION 2 at the times specified in Paragraph 1.E., Compliance .
d. If no crack, crack indication, discrepant fastener hole, or corrosion is found, perform repeat
inspections in accordance with PART I, OPTION 2 at the times specified in Paragraph 1.E.,
Compliance.
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### Page 32

e. Close access to the forward side of the aft pressure bulkhead by installing these items as
follows:
(1) Install kept galley. Refer to 737-600/700/800/900 AMM 25-31-41 and 737-600/700/800/900
AMM 25-31-61 as accepted procedures.
(2) Install kept lavatory. Refer to 737-600/700/800/900 AMM 25-40-18 and
737-600/700/800/900 AMM 25-40-19 as accepted procedures.
f. Put the airplane back to a serviceable condition.
PART II - INSPECTION OF THE WEB AT THE "Y" CHORD BELOW S-15L and S-15R
1. Open access to the forward side of the aft pressure bulkhead by removing these items as follows:
a. Remove/keep the galley. Refer to 737-600/700/800/900 AMM 25-31-41 and
737-600/700/800/900 AMM 25-31-61 as accepted procedures.
b. Remove/keep the lavatory. Refer to 737-600/700/800/900 AMM 25-40-18 and
737-600/700/800/900 AMM 25-40-19 as accepted procedures.
c. Remove/keep the potable water tank. Refer to 737-600/700/800/900 AMM 38-11-01 as an
accepted procedure.
2. Do the inspections of the web from the forward side (HFEC), aft side (LFEC) and Detailed Inspection
of the aft pressure bulkhead in accordance with FIGURE 3.
NOTE: In many areas the access is limited and you can do the inspections from only one side:
either the forward side (HFEC) or the aft side (LFEC). In these areas, do the inspection
from the side which provides access.
3. If any crack, crack indication, discrepant fastener hole, or corrosion is found:
a. ACTION 1: Contact The Boeing Company for repair instructions and do the repair.
b. ACTION 2: On areas that are not repaired, perform repeat inspections in accordance with
PART II at the times specified in Paragraph 1.E., Compliance .
4. If no crack, crack indication, discrepant fastener hole, or corrosion is found, perform repeat
inspections in accordance with PART II at the times specified in Paragraph 1.E., Compliance.
5. Close access to the forward side of the aft pressure bulkhead by installing these items as follows:
a. Install kept galley. Refer to 737-600/700/800/900 AMM 25-31-41 and 737-600/700/800/900
AMM 25-31-61 as accepted procedures.
b. Install kept lavatory. Refer to 737-600/700/800/900 AMM 25-40-18 and 737-600/700/800/900
AMM 25-40-19 as accepted procedures.
c. Install kept potable water tank. Refer to 737-600/700/800/900 AMM 38-11-01 as an accepted
procedure.
6. Put the airplane back to a serviceable condition.
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: September 09, 2004
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BOEING SERVICE BULLETIN 737-53A1248
ALERTALERT

### Page 33 (OCR)

BOEING SERVICE BULLETIN 737-53A1248
ALERT  ALERT
FIN TERMINAL
FITTING
ACCESS DOOR
BL
S-3L  S-3R  OUTER CIRCUMFERENTIAL
TEAR STRAP
alo°
SEE (
S-7L  STEEL STRAPS  _S-7R
(14 PLACES)
S-10L -  -S-10R
S-15L  - S-15R
EDGE OF
"Y" CHORD
A-A
VIEW LOOKING FORWARD  N71437
FIGURE 1: LFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R
(SHEET 1 OF 3)
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PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.  33 of 40

### Page 34

FIGURE 1: LFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R
(SHEET 2 OF 3)
Export Controlled ECCN: 9E991 - BOEING
PROPRIETARY - Copyright © Unpublished
Work - See page 1 for details.
Original Issue: September 09, 2004
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BOEING SERVICE BULLETIN 737-53A1248
ALERTALERT

### Page 35

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
NOTESREFERENCESPROCEDURENAMETASKSTEP
From the aft side, inspect the aft fas-
tener row of the "Y" chord/web inter-
face above S-15L and S-15R for any
crack or crack indication. It is not
necessary to inspect the web in the
area of the steel straps. Instead, per-
form a Detailed Inspection along the
edge of the steel straps.
737 NDT Manual
Part 6, 53-10-54.
LFECWebInspect1
Wherever you are doing the NDT in-
spection, inspect along both fastener
rows which attaches the web to the
"Y" chord and along the edge of the
"Y" chord. Do a detailed inspection for
cracks and fastener installation dis-
crepancies that may indicate incorrect-
ly drilled or elongated fastener holes
and corrosion. Refer to 737-600 SRM
51-40-02, 737-700 SRM 51-40-02,
737-700CONV SRM 51-40-02, 737-
700IGW (BBJ) SRM 51-40-02, 737-
800 SRM 51-40-02, 737-900 SRM 51-
40-02, 737-900ER SRM 51-40-02 as
an accepted procedure.
-Detailed InspectionWebInspect2
FIGURE 1: LFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R
(SHEET 3 OF 3)
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ALERTALERT

### Page 36 (OCR)

BOEING SERVICE BULLETIN 737-53A1248
ALERT  ALERT
FIN TERMINAL
FITTING DOUBLER
RADIAL STIFFINER
(TYPICAL)
BL
S-3R O  • S-3L  OUTER CIRCUMFERENTIAL
ACCESS  TEAR STRAP
DOOR
B
S-7R.  →S~7L
S-11R -  S-11L
S-15R  • S-15L
SPLICE ANGLE
(2 PLACES)
S-21R  \ S-21L
FLOOR BEAM
A-A  N71439
VIEW LOOKING AFT
FIGURE 2: HFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R
(SHEET 1 OF 2)
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Work - See page 1 for details.  36 of 40

### Page 37

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
NOTESREFERENCESPROCEDURENAMETASKSTEP
From the forward side, inspect the aft
fastener row of the web above S-15L
and S-15R for any crack or crack indi-
cation. (a) (b)
737 NDT Manual Part 6,
51-00-00, Procedure 4
or Procedure 23.
HFECWebInspect1
Wherever you are doing the NDT in-
spection, inspect along both fastener
rows of the web. Do a detailed inspec-
tion for cracks and fastener installa-
tion discrepancies that may indicate
incorrectly drilled or elongated fasten-
er holes and corrosion. Refer to 737-
600 SRM 51-40-02, 737-700 SRM
51-40-02, 737-700CONV SRM 51-40-
02, 737-700IGW (BBJ) SRM 51-40-
02, 737-800 SRM 51-40-02, 737-900
SRM 51-40-02, 737-900ER SRM 51-
40-02 as an accepted procedure.
-Detailed InspectionWebInspect2
(a) Where a radial stiffener overlaps the "Y" chord at the perimeter of the web, you cannot get access to the
web to inspect the fastener holes. Instead, use the reference HFEC procedure to inspect the web along
the edge of the radial stiffener adjacent to the fastener holes that need to be inspected. Inspect the web
for a distance of one inch each side of the fastener row.
(b) Where the fin terminal fitting doublers overlap the web, use the reference HFEC procedure to inspect the
web along the edge of the doublers.
FIGURE 2: HFEC AND DETAILED INSPECTION OF THE WEB AT THE "Y" CHORD - ABOVE S-15L AND
S-15R
(SHEET 2 OF 2)
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ALERTALERT

### Page 38 (OCR)

BOEING SERVICE BULLETIN 737-53A1248
ALERT  ALERT
ACCESS DOOR
S-15R  S-15L
B
S-21R  S-21L
SPLICE ANGLE
(2 PLACES)  FLOOR BEAM
A—A
VIEW LOOKING AFT
FRAME CHORD  FRAME CHORD
WEB
"Y" CHORD  "Y" CHORD
FWD C  FWD <  WEB  N71441
B-B  C-C
FIGURE 3: HFEC, LFEC AND DETAILED INSPECTION OF WEB AT "Y" CHORD - BELOW S-15L AND
S-15R
(SHEET 1 OF 3)
Original Issue: September 09, 2004
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### Page 39

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
NOTESREFERENCESPROCEDURENAMETASKSTEP
From the forward side, inspect
the aft fastener row of the web
below S-15L and S-15R for any
crack or crack indication. At the
"Y" chord splice and at the inter-
section of the floor structure and
the "Y" chord, do step 3 instead.
See step 4 below for optional in-
spection. (a)
737 NDT Manual
Part 6, 51-00-00,
Procedure 4 or Pro-
cedure 23.
HFECWebInspect1
Wherever possible, inspect on
the forward side of the aft pres-
sure bulkhead along both fasten-
er rows of the web below S-15L
and S-15R. Do a detailed inspec-
tion for cracks and fastener instal-
lation discrepancies that may in-
dicate incorrectly drilled or elon-
gated fastener holes and corro-
sion. Refer to 737-600 SRM 51-
40-02, 737-700 SRM 51-40-02,
737-700CONV SRM 51-40-02,
737-700IGW (BBJ) SRM 51-40-
02, 737-800 SRM 51-40-02, 737-
900 SRM 51-40-02, 737-900ER
SRM 51-40-02 as an accepted
procedure. See Step 5 below for
optional inspection.
-Detailed InspectionWebInspect2
Do the LFEC inspection for any
crack or crack indication on the
aft side of the aft pressure bulk-
head web at the "Y" chord
splices and where the floor
structure intersects the "Y" chord.
(b) (c)
737 NDT Manual
Part 6, 53-10-54.
LFECWebInspect3
From the aft side, inspect the aft
fastener row of the "Y" chord web
interface below S-15L and S-15R
for any crack or crack indication.
Inspect along the edge of the
steel straps.
737 NDT Manual
Part 6, 53-10-54.
LFECWebInspection
Option
4
FIGURE 3: HFEC, LFEC AND DETAILED INSPECTION OF WEB AT "Y" CHORD - BELOW S-15L AND
S-15R
(SHEET 2 OF 3)
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ALERTALERT

### Page 40

NOTESREFERENCESPROCEDURENAMETASKSTEP
Do a detailed inspection on the
web along the edge of the flange
and both fastener rows, looking
for cracks, corrosion, and fasten-
er installation discrepancies that
may indicate incorrectly drilled or
elongated fastener holes. Refer
to 737-600 SRM 51-40-02, 737-
700 SRM 51-40-02, 737-
700CONV SRM 51-40-02, 737-
700IGW (BBJ) SRM 51-40-02,
737-800 SRM 51-40-02, 737-900
SRM 51-40-02, 737-900ER SRM
51-40-02 as an accepted proce-
dure.
-Detailed InspectionWeb / "Y"
chord
Inspection
Option
5
(a) Where a radial stiffener overlaps the "Y" chord at the perimeter of the web, you cannot get access to the
web to inspect the fastener holes. Instead, use the reference HFEC procedure to inspect the web along
the edge of the radial stiffener adjacent to the fastener holes that need to be inspected. Inspect the web
for a distance of one inch each side of the fastener row.
(b) It is possible that the NDT manual shows an inspection area that is different than what is shown in this
bulletin. Use the inspection area shown in this bulletin.
(c) It is not possible to inspect the web adjacent to the stringer end-fittings because the NDT probe cannot
fit under the fittings.
FIGURE 3: HFEC, LFEC AND DETAILED INSPECTION OF WEB AT "Y" CHORD - BELOW S-15L AND
S-15R
(SHEET 3 OF 3)
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