# Boeing Alert Service Bulletin 737-53A1319: U.S. DOT/FAA - Service Bulletin - SB 737-53A1319

- Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2011-0348; AD 2011-08-51 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication.
- Document: [Boeing Alert Service Bulletin 737-53A1319](https://openairdocs.org/service-documents/boeing/737-53a1319.md)
- Title as filed: U.S. DOT/FAA - Service Bulletin - SB 737-53A1319
- Pages: 33
- PDF: https://openairdocs.org/files/sha256/01/05/010553fbd35c69917ec08b01a141b5aaef67bf39639f092997ae36e128e804f7
- Page: https://openairdocs.org/service-documents/boeing/737-53a1319/file/010553fbd35c

## Text

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### Page 1

Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-53A1319
Original Issue: April 04, 2011
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at
Stringer S-4, Between BS 360 and BS 908
Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15
CFR 730-774). 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 © 2011 The Boeing Company
Unpublished Work - All Rights Reserved
Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable
subject matter. Boeing also claims copyright in this document as a compilation and/or collective work.
This document includes proprietary information owned by The Boeing Company and/or one or more third parties.
Treatment of the document and the information it contains is governed by contract with Boeing. For more
information, contact The Boeing Company, P.O. Box 3707, Seattle, Washington 98124.
Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner,
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connection with this document unless provided in writing by Boeing.
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Table of Contents
Summary ...................................................... 5
1. PLANNING INFORMATION ........................................ 9
A. Effectivity ................................................ 9
1. Airplanes ............................................. 9
2. Spares Affected ........................................ 1 2
B. Concurrent Requirements ...................................... 1 2
C. Reason ................................................ 1 3
D. Description .............................................. 1 3
E. Compliance .............................................. 1 3
F. Approval ............................................... 1 4
G. Manpower .............................................. 1 4
H. Weight and Balance Changes .................................... 1 4
I. Electrical Load Data ......................................... 1 4
J. References .............................................. 1 4
1. Existing Data .......................................... 1 4
2. Data supplied with this Service Bulletin ............................ 1 4
3. Installation Drawings Used in the Preparation of this Service Bulletin ............ 1 4
K. Publications Affected ........................................ 1 4
L. Interchangeability and Intermixability of Parts ........................... 1 5
2. MATERIAL INFORMATION ........................................ 1 7
A. Material - Price and Availability ................................... 1 7
B. Industry Support Information .................................... 1 7
C. Parts Necessary For Each Airplane ................................. 1 7
1. Kits/Parts ............................................ 1 7
2. Parts and Materials Supplied by the Operator ........................ 1 7
3. Parts Modified and Reidentified ................................ 1 7
4. Parts Removed and Not Replaced .............................. 1 7
D. Parts Necessary to Change Spares ................................. 1 7
E. Special Tooling - Price and Availability ............................... 1 7
F. Special Tooling Necessary to do this Service Bulletin ....................... 1 7
3. ACCOMPLISHMENT INSTRUCTIONS .................................. 1 9
A. GENERAL INFORMATION ..................................... 1 9
B. WORK INSTRUCTIONS ....................................... 2 0
FIGURE 1: EXTERNAL INSPECTION ................................... 2 1
FIGURE 2: ALTERNATIVE INTERNAL INSPECTION .......................... 2 3
FIGURE 3: CONFIRMING A CRACK INDICATION ............................ 2 6
FIGURE 4: SECOND EXTERNAL INSPECTION - INSPECTION LOCATION .............. 2 9
FIGURE 5: INSPECTION ZONES ..................................... 3 1
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Commercial 
Airplanes
737
Service Bulletin
ALERT
SummaryNumber: 737-53A1319Original Issue: April 04, 2011
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at
Stringer S-4, Between BS 360 and BS 908
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
Recently, a 737-300 airplane, outside of the effectivity of Service Bulletin (SB) 737-53A1255, experienced a
rapid decompression when the lap joint at stringer S-4L between BS 664 - BS 727 cracked and opened up.
Investigation shows that the cracking was caused by fatigue cracking in the lower skin at the lower row of
fasteners in the lap joint. The airplane had 39,781 total flight cycles and 48,740 total flight hours. This service
bulletin gives instructions to inspect the lower row of fasteners at stringer S-4R and S-4L, from BS 360 to BS
908 for cracking in the lower skin of the lap joint. If cracking at this location goes undetected, the cracks could
link up, resulting in an uncontrolled decompression.
Airplanes prior to Line Number 2553 are covered by Service Bulletin (SB) 737-53A1255. This SB covers airplanes
from Line Number 2553 to 3132.
ACTION
Do a Non Destructive Test (NDT) Dual Frequency Eddy Current (DFEC) external inspection of the lap joint at
stringers S-4R and S-4L along the entire length from BS 360 to BS 908.
As an option to doing the external DFEC inspection of the lap joint, you can get access to the interior fuselage
and do NDT eddy current and Detailed Inspections.
As an option, crack indications can be confirmed by doing internal eddy current inspections.
If a crack is found, contact Boeing for a repair and do the repair.
EFFECTIVITY
737-300, 737-400, and 737-500 Airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes.
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COMPLIANCE
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service
bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin
mandatory.
Refer to Paragraph 1.E., Compliance.
INDUSTRY SUPPORT INFORMATION
At the time of release of this service bulletin, warranty remedies have not been determined. A subsequent
revision or Information Notice will address the warranty remedies available, if any.
MANPOWER
TBD
MATERIAL INFORMATION
None.
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BOEING SERVICE BULLETIN 737-53A1319
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LOWER SKIN
INSPECT LAP JOINT
BETWEEN STA 360
AND STA 908
TEAR STRAP
• *,
S-4L/R'
AT THE LOWER ROOF FASTENE
TYPICAL LAP JOINT CONFIGURATION
2068118
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Commercial 
Airplanes
737
Service Bulletin
ALERT
Number: 737-53A1319
Original Issue: April 04, 2011
ATA System: 5331
SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at
Stringer S-4, Between BS 360 and BS 908
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
DESCRIPTIONCONFIGURATIONGROUP
737-300, 737-400 and 737-500 Airplanes-1
Airplane Models:
737-300, 737-400, 737-500
GroupVariable Number
1PJ552 - PJ561
1PJ601 - PJ615
1PJ811
1PJ816 - PJ817
1PM543 - PM550
1PP518 - PP520
1PP876 - PP877
1PQ297 - PQ299
1PQ345 - PQ348
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GroupVariable Number
1PQ370 - PQ373
1PQ391 - PQ395
1PQ408 - PQ410
1PQ414 - PQ418
1PQ431 - PQ438
1PQ447 - PQ448
1PQ451
1PQ454
1PQ473 - PQ475
1PQ772
1PQ933 - PQ935
1PQ951
1PQ971 - PQ997
1PR001 - PR017
1PR021 - PR034
1PR041 - PR045
1PR061 - PR072
1PR077 - PR082
1PR091 - PR092
1PR096
1PR101
1PR121 - PR122
1PR131 - PR132
1PR141 - PR143
1PR161 - PR172
1PR181
1PS617 - PS630
1PS704 - PS706
1PS763 - PS799
1PS811
1PS836 - PS837
1PS841 - PS846
1PS851 - PS852
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GroupVariable Number
1PS856
1PS861 - PS863
1PS866 - PS868
1PS871 - PS874
1PS896 - PS897
1PS901 - PS941
1PS956 - PS957
1PS961 - PS963
1PS971 - PS978
1PT012 - PT015
1PT029 - PT031
1PT064
1PT126 - PT138
1PT188
1PT307 - PT309
1PT513 - PT517
1PT585 - PT586
1PT643 - PT644
1PT656
1PT681 - PT685
1PT716 - PT717
1PT721 - PT725
1PT801 - PT834
1PT851 - PT854
1PT871 - PT886
1PT901 - PT930
1PT971 - PT973
1PT981 - PT985
1PT996
1PU301
1PU311 - PU313
1PV204 - PV209
1PV226 - PV229
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GroupVariable Number
1PV284 - PV287
1PV296
1PV301 - PV302
1PV351
1PV356 - PV357
1PW086 - PW088
1PW168 - PW171
1PW245 - PW252
1PW262 - PW264
1PW271 - PW276
1PW282 - PW292
1PW401 - PW408
1PW411 - PW418
1PW421 - PW424
1PW431 - PW435
1PW441 - PW450
1PW521 - PW522
1PW524 - PW525
1PW527 - PW530
1PW547 - PW550
1PW621 - PW622
1PW635 - PW637
1PW831
1PW851 - PW856
2. Spares Affected
B. Concurrent Requirements
None.
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C. Reason
Recently, a 737-300 airplane, outside of the effectivity of Service Bulletin (SB) 737-53A1255, experienced
a rapid decompression when the lap joint at stringer S-4L between BS 664 - BS 727 cracked and
opened up. Investigation shows that the cracking was caused by fatigue cracking in the lower skin at
the lower row of fasteners in the lap joint. The airplane had 39,781 total flight cycles and 48,740 total
flight hours. This service bulletin gives instructions to inspect the lower row of fasteners at stringer
S-4R and S-4L, from BS 360 to BS 908 for cracking in the lower skin of the lap joint. If cracking at this
location goes undetected, the cracks could link up, resulting in an uncontrolled decompression.
Airplanes prior to Line Number 2553 are covered by Service Bulletin (SB) 737-53A1255. This SB covers
airplanes from Line Number 2553 to 3132.
D. Description
Do a Non Destructive Test (NDT) Dual Frequency Eddy Current (DFEC) external inspection of the lap
joint at stringers S-4R and S-4L along the entire length from BS 360 to BS 908.
As an option to doing the external DFEC inspection of the lap joint, you can get access to the interior
fuselage and do NDT eddy current and Detailed Inspections.
As an option, crack indications can be confirmed by doing internal eddy current inspections.
If a crack is found, contact Boeing for a repair and do the repair.
The work in this service bulletin is done in the maintenance zone(s) given below.
Affected Maintenance Zones
ZoneModel
107, 108737-300, 737-400, 737-500
E. Compliance
The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to
this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this
service bulletin mandatory.
Boeing recommends that the inspections be done before the airplane has 30,000 total flight cycles or
within 20 days of the original issue date of this SB, whichever occurs later. For airplanes with 30,000
to 34,999 total flight cycles, do the inspections within 20 days of the original issue date of this SB. For
airplanes that have 35,000 total flight cycles or more, do the inspections within 5 days of the original
issue date of this SB. Repeat the inspections at intervals not to exceed 500 flight cycles. If a crack is
found, contact Boeing for a repair and do the repair.
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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.
G. Manpower
TBD
H. Weight and Balance Changes
None.
I. Electrical Load Data
None.
J. References
1. Existing Data
a. Boeing Service Bulletin 737-53A1255
b. 737 NDT Part 6, 51-00-00 Figure 16, 53-30-00 Figure 9, 53-30-12, 53-30-16
c. Boeing Service Letter 737-SL-51-042
2. Data supplied with this Service Bulletin
None.
3. Installation Drawings Used in the Preparation of this Service Bulletin
None.
K. Publications Affected
1. Publications:
None.
2. Damage Tolerance Based Structural Inspections:
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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 does not affect FCS, therefore DTIs are not necessary.
L. Interchangeability and Intermixability of Parts
None.
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2.    MATERIAL INFORMATION
A. Material - Price and Availability
None.
B. Industry Support Information
At the time of release of this service bulletin, warranty remedies have not been determined. A subsequent
revision or Information Notice will address the warranty remedies available, if any.
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. The instructions identified in Paragraph 3.B., Work Instructions and the Figure(s)
give the recommended sequence of steps. The sequence of steps to do this service
bulletin can be changed.
2. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for
definition of the acronyms.
3. Obey all of the warnings and cautions given in the specified manual sections.
4. 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 limits to tighten nuts and bolts are in SRM Chapter 51
5. Use the approved fastener and process material substitutions in accordance with
SRM Chapter 51.
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.
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.
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.
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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. 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.
B. WORK INSTRUCTIONS
NOTE: Inspection procedures 737 NDT Part 6, 53-30-16 and 737 NDT Part 6, 53-30-12 show limited
effectivity. The inspections applicable to the lap joint lower rows in these procedures are applicable to
the full effectivity in this service bulletin.
1. Do external eddy current inspections for cracks in the lower skin at the lap joint lower fastener row
at stringer S-4L and S-4R at the locations shown in Figure 5 as follows:
a. Do the first inspection for cracks along the centerline in accordance with Figure 1.
b. Do a second inspection for cracks along the lower edge of the fastener countersunk heads
in accordance with Figure 4.
c. It is not required to inspect the lower skin at the lap joint lower fastener row under existing
external repair doublers provided:
(1) The installed repair was approved by the FAA or by a Boeing Authorized Representative
who was authorized by the FAA to make such findings.
(2) The installed repair extends a minimum of three rows of fasteners above the chem-mill
step and three rows of fasteners below the lap joint lower row.
If the repair does not meet the above conditions, then inspect the lower skin lap joint lower
row internally in the area covered by the doubler in accordance with Figure 2.
2. As an alternative to doing the external eddy current inspection, you can get access to the interior
fuselage and do eddy current inspection and Detailed Inspection for cracks in the lower skin at
the lower row of fasteners at stringer S-4L and S-4R in accordance with Figure 2.
3. As an option, crack indications can be confirmed by gaining access to the interior fuselage, as
required, and doing an internal eddy current inspection for cracking in the lower skin at the crack
indication in accordance with Figure 3.
4. If any crack is found in the lap joint, contact Boeing for a repair and do the repair.
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BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
LOWER SKIN
TEAR STRAP
At‡+
CRACK EXAMPLES
SHOWN IN THE LOWER
SKIN AT THE LOWER
ROW OF FASTENERS
TYPICAL LAP JOINT CONFIGURATION  2068143
FIGURE 1: EXTERNAL INSPECTION
(SHEET 1 OF 2)
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The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
(a)--Crown Lap Joints Lower
Skin
Inspect1
(a) Do an external eddy current inspection for cracking in the lap joint lower fastener row in accordance with
737 NDT Part 6, 53-30-00 Figure 9.
FIGURE 1: EXTERNAL INSPECTION
(SHEET 2 OF 2)
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BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
STA
908
STA
360
S-4R
S-4L
TEAR STRAP
S-4L/R
V
CHEM-MILLED
TYPICAL LAP JOINT CONFIGURATION WHERE LOWER
SKIN DOUBLER IS CHEM-MILLED AT THE LAP JOINT
2068124
FIGURE 2: ALTERNATIVE INTERNAL INSPECTION
(SHEET 1 OF 3)
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BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
TEAR STRAP
S-4L/R
CHEM-MILLED
NON CHEM  LLED
EWD
TYPICAL LAP JOINT CONFIGURATION WHERE LOWER
SKIN DOUBLER IS NOT CHEM-MILLED AT THE LAP JOINT
2068135
FIGURE 2: ALTERNATIVE INTERNAL INSPECTION
(SHEET 2 OF 3)
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The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
Between tear straps (a)(b)--Crown Lap Joints Lower
Skin
Inspect1
At tear straps (a)(c)--Crown Lap Joints Lower
Skin
Inspect2
Where lower skin doubler is
not chem-milled at the lap
joint (a)(d)
--Crown Lap Joints Lower
Skin
Inspect3
(a) Do a Detailed Inspection of the lap joint lower fastener row for cracking.
(b) Do an internal Mid Frequency Eddy Current (MFEC) inspection for cracking in the lap joint lower fastener
row between tear straps in accordance with 737 NDT Part 6, 53-30-16.
(c) Do a Low Frequency Eddy Current (LFEC) inspection for cracking in the lap joint lower fastener row
through the tear strap in accordance with 737 NDT Part 6, 53-30-12.
(d) Do a Low Frequency Eddy Current (LFEC) inspection for cracking in the lap joint lower fastener row
through the lower doubler in accordance with 737 NDT Part 6, 53-30-12.
FIGURE 2: ALTERNATIVE INTERNAL INSPECTION
(SHEET 3 OF 3)
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ALERTALERT

### Page 26 (OCR)

BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
STA
908
STA
360
S-4R-
S-4L
TEAR STRAP
S-4L/R
V
CHEM-MILLED
TYPICAL LAP JOINT CONFIGURATION WHERE LOWER
SKIN DOUBLER IS CHEM-MILLED AT THE LAP JOINT
2068144
FIGURE 3: CONFIRMING A CRACK INDICATION
(SHEET 1 OF 3)
Original Issue: April 04, 2011
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### Page 27 (OCR)

BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
TEAR STRAP
S-4L/R
CHEM-MILLED
NON CHEM-MILLED
TYPICAL LAP JOINT CONFIGURATION WHERE LOWER
SKIN DOUBLER IS NOT CHEM-MILLED AT THE LAP JOINT
B  2068145
FIGURE 3: CONFIRMING A CRACK INDICATION
(SHEET 2 OF 3)
Original Issue: April 04, 2011
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Copyright © Unpublished Work - See page 1 for details.  27 of 33

### Page 28

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
Between tear straps (a)--Crown Lap Joints Lower
Skin
Inspect1
At tear straps (b)--Crown Lap Joints Lower
Skin
Inspect2
Where lower skin doubler is
not chem-milled at the lap
joint (c)
--Crown Lap Joints Lower
Skin
Inspect3
(a) If there was a crack indication at this location as a result of the external eddy current inspection: do an
internal Mid Frequency Eddy Current (MFEC) inspection for cracking in the lap joint lower fastener row
between tear straps in accordance with 737 NDT Part 6, 53-30-16.
(b) If there was a crack indication at this location: do a Low Frequency Eddy Current (LFEC) inspection for
cracking in the lap joint lower fastener row through the tear strap in accordance with 737 NDT Part 6, 53-
30-12 or do 737 NDT Part 6, 51-00-00 Figure 16 hole probe inspection. Use 0.03 inch notch standard for
the 737 NDT Part 6, 51-00-00, Figure 16 inspection.
(c) If there was a crack indication at this location: do a Low Frequency Eddy Current (LFEC) inspection for
cracking in the lap joint lower fastener row through the lower doubler in accordance with 737 NDT Part 6,
53-30-12 or do 737 NDT Part 6, 51-00-00 Figure 16 hole probe inspection. Use 0.03 inch notch standard
for the 737 NDT Part 6, 51-00-00, Figure 16 inspection.
FIGURE 3: CONFIRMING A CRACK INDICATION
(SHEET 3 OF 3)
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Original Issue: April 04, 2011
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BOEING SERVICE BULLETIN 737-53A1319
ALERTALERT

### Page 29 (OCR)

BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
TYPICAL
LOWER SKIN  CRACKS
TEAR STRAP
UPPER EDGE OF
LOWER SKIN
S-4L/R
LOWER FASTENEF
ROW OF LAP JOINT
COUNTERSUNK
FASTENER HEAD SHOWN)
LOWER EDGE  2068146
OF UPPER SKIN
FIGURE 4: SECOND EXTERNAL INSPECTION - INSPECTION LOCATION
(SHEET 1 OF 2)
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Copyright © Unpublished Work - See page 1 for details.  29 of 33

### Page 30

The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
MORE DATAQTYIDENTIFICATIONNAMETASKSTEP
(a)--Crown Lap Joints Lower
Skin
Inspect1
(a) Do an external eddy current inspection for cracking in the lap joint lower fastener row in accordance with
737 NDT Part 6, 53-30-00 Figure 9. Move the centerline of the probe along the lower edge of the fastener
countersunk heads.
FIGURE 4: SECOND EXTERNAL INSPECTION - INSPECTION LOCATION
(SHEET 2 OF 2)
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BOEING SERVICE BULLETIN 737-53A1319
ALERTALERT

### Page 31 (OCR)

BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
S-4R  S-4L
STA
1016
•
STA
908
SZA
STA
540
STA
360
STA
259.50  737-300  2068147
FIGURE 5: INSPECTION ZONES
(SHEET 1 OF 3)
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Copyright © Unpublished Work - See page 1 for details.  31 of 33

### Page 32 (OCR)

BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
SAR SAL
STA
1016
STA
908
00
00I
•0000.
STA  0000
727
STA
540
0000  •0u.u0o
•
STA
360
STA
259.50  737-400  2068148
FIGURE 5: INSPECTION ZONES
(SHEET 2 OF 3)
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### Page 33 (OCR)

BOEING SERVICE BULLETIN 737-53A1319
ALERT  ALERT
S-4R S-4L
STA
1016
STA
908
00  0000
•00
STA
360
STA
259.50  737-500  2068149
FIGURE 5: INSPECTION ZONES
(SHEET 3 OF 3)
Original Issue: April 04, 2011
BOEING PROPRIETARY -  737-53A1319
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