Commercial 

Airplanes 737

Service Bulletin

ALERT

Number: 737-53A1255

Original Issue: October 17, 2002

Revision 2: August 07, 2012

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at

Stringers S-4, S-10, S-14 Between STA 360 and STA 908

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.

ECCN: 9E991

BOEING PROPRIETARY, CONFIDENTIAL AND/OR TRADE SECRET

Copyright © 2002 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Unpublished Work.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, DreamlinerTM,

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BLANK PAGE
Table of Contents

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

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

1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

E. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

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

I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

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

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

2. Data Supplied with this Service Bulletin: . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

3. Installation Drawings Used in the Preparation of this Service Bulletin: . . . . . . . . . . . 45

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

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

M. Software Accomplishment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

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

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

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

C. Parts Necessary for Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

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

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

3. Parts Modified and Reidentified: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4. Parts Removed and Not Replaced: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 47

3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

FIGURE 1: INTERNAL INSPECTION - CROWN LAP JOINTS AND STRINGER CLIPS . . . . . . . . 69

FIGURE 2: EXTERNAL INSPECTION - CROWN LAP JOINTS . . . . . . . . . . . . . . . . . . . . . 71

FIGURE 3: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 1] . . . . . . . . . . . 73

FIGURE 4: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 2] . . . . . . . . . . . 75

FIGURE 5: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 3] . . . . . . . . . . . 77

FIGURE 6: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 4] . . . . . . . . . . . 79

FIGURE 7: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 5] . . . . . . . . . . . 81

FIGURE 8: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 6] . . . . . . . . . . . 83

FIGURE 9: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 7] . . . . . . . . . . . 85

FIGURE 10: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 8] . . . . . . . . . . . 87

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ALERT ALERT
FIGURE 11: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 9] . . . . . . . . . . . 89

FIGURE 12: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 10] . . . . . . . . . . 91

FIGURE 13: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 11] . . . . . . . . . . 93

FIGURE 14: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 12] . . . . . . . . . . 95

FIGURE 15: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 13] . . . . . . . . . . 97

FIGURE 16: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 14] . . . . . . . . . . 99

FIGURE 17: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 15] . . . . . . . . . . 101

FIGURE 18: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 16] . . . . . . . . . . 103

FIGURE 19: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 17] . . . . . . . . . . 105

FIGURE 20: INSPECTION ZONES AT THE CROWN LAP JOINT AREA [Group 18] . . . . . . . . . . 107

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
Commercial 

Airplanes 737

Service Bulletin

ALERT

Revision Transmittal Sheet Number: 737-53A1255

Original Issue: October 17, 2002

Revision 2: August 07, 2012

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at

Stringers S-4, S-10, S-14 Between STA 360 and STA 908

This revision includes all pages of the service bulletin.

COMPLIANCE INFORMATION RELATED TO THIS REVISION

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

Federal Aviation Administration (FAA) Airworthiness Directive AD 2003-08-15 is related to this service bulletin.

REASON FOR REVISION

This revision is sent to incorporate additional compliance notes in Paragraph 1.E., Compliance and additional

inspection notes in Paragraph 3.B., Work Instructions.

These sections were changed:

1. Paragraph 1.E., Compliance, added new compliance notes.

2. Paragraph 1.F., Approval, changed service bulletin revision number.

3. Added Paragraph 1.M., Software Accomplishment Summary.

4. Paragraph 3.B., Work Instructions, added new inspection notes.

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

of important changes.

Pages with no vertical lines have no important changes.

REVISION HISTORY

Original Issue: October 17, 2002

Revision 1: November 07, 2011

Revision 2: August 07, 2012

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT

BLANK PAGE
Commercial 

Airplanes 737

Service Bulletin

ALERT

Summary Number: 737-53A1255

Original Issue: October 17, 2002

Revision 2: August 07, 2012

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at

Stringers S-4, S-10, S-14 Between STA 360 and STA 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

This service bulletin outlines additional inspection requirements with reduced compliance times from that described

in service bulletin 737-53A1177 for stringer S-4L & S-4R skin lap joints between STA 360-STA 908, S-10L,

S-10R, S-14L, S-14R between STA 360-STA 540 and STA 727-STA 908.

Two findings, one discovered on September 11, 2002 on a 737-300 with 52,400 flight cycles and the other

discovered on December 31, 2001 on a 737-200 with 60,333 flight cycles have caused increased concern with

the extent of lap joint lower row cracking.

On December 31, 2001 during a walk-around inspection on a 737-200 with 60,333 flight cycles, a 23 inch long

crack was found in the lower row of the stringer S-4L lap joint between STA 616 and STA 639. The technician

noticed the crack above the over-wing exit, because the lower skin was pushed outward approximately 1 inch

with the crack ends turning downward at the tear straps. There was no report from the flight crew of pressurization

problems or from passenger or cabin crew of any abnormal noise in the area. The operator elected to inspect

the lap joint for additional cracks using external and internal NDT methods. Additional cracks were found.

Following a local repair of the 23 inch long crack the operator ferried the airplane unpressurized to a maintenance

facility to perform the 737-53A1177 lap joint modification. The removed lap joints were inspected by Boeing

NDT personnel using the current methods referenced in service bulletin 737-53A1177 and significantly more

cracks were found.

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Boeing is concerned about the extent of cracking both forward and aft of the 23 inch long cracked section. Cracks

were found in between the tear straps and in the skin at locations common to the tear straps. The in-tact tear

straps were able to turn the cracks as they were designed to do. However, due to the condition of the skin at

the tear straps forward and aft of the 23 inch crack area, it is likely that similar crack link-up just forward in an

area which had a higher percentage of cracked fastener holes could have resulted in an uncontained

decompression. Of great importance is the total number and length of cracks found at this particular lap joint.

The damage observed is believed to exceed all prior in-service crack findings and Boeing predictions based on

test and analysis for an airplane with 60,000 flight cycles.

On September 11, 2002 Boeing NDT personnel, while assisting an operator of a 737-300 with 52,400 flight

cycles, discovered significant cracking on the stringer S-4R lap joint between STA 600 and STA 727. At one

location between STA 639 and STA 650, every fastener hole (11 total) had a crack of over 0.5 inches emanating

from each side. Although the individual cracks had not yet linked up, it was clear that within a few number of

flights the cracks would have linked up with a length of over 10 inches. Forward of this section between STA

636 and STA 620, 15 fastener holes in a row were cracked. This included the skin common to the tear strap at

STA 630. Although these cracks were only 0.2 inches long, there were only 4 crack free fastener holes separating

the two cracked areas. Additionally, 3 stringer clips common to S-4 were found to be cracked. The clip at STA

639 was completely severed and the clips at STA 616 and STA 663.75 were partially cracked. Stringer clips

were redesigned beginning at line position 1001. Service bulletin 737-53-1268, which superseded service bulletin

737-53-1085 provides retrofit instructions for airplanes built prior to line position 1001. Service bulletin 737-53-1268

also inspects for damaged stringer clips for airplanes line positions 1001 to 3132. The cracks in the lap joints

were found using the LFEC external inspection method and verified using the MFEC inspection method which

are called out in service bulletin 737-53A1177. Previous inspection by the operator found significantly less

cracking. Boeing NDT personnel were able to locate over eight times as many cracks.

If the cracks continue to grow undetected they will link-up. Independent large scale fatigue testing at Boeing

has shown that this extent of cracking can result in an uncontrolled decompression.

Since the release of service bulletin 737-53A1177 Revision 6 and the original issue of this service bulletin there

have been many reports of crack findings. On 33 airplanes between 36,781 flight cycles and 68,884 flight cycles

lap joint damage has been found, with cracking lengths ranging from 0.03 inches to 0.10 inches, with the exception

of the more significant cracking noted above. Cracks have also been found in lap joint lower skins that do not

intersect fastener holes. Boeing has completed a re-evaluation of the compliance requirements for the lap joints.

As a result of the re-evaluation the inspection recommendations of the crown lap joints between STA 360 - STA

908 are updated. This update includes a reduced inspection threshold and repeat inspections. Accomplishment

of service bulletin 737-53A1177 lap joint modification is mandated by AD 2002-07-08 to be accomplished before

50,000 total flight cycles.

Boeing Service Related Problem (SRP) 737-SRP-53-0372 is related to this service bulletin.

This table is provided to operators for planning purposes only. Refer to the applicable sections for more

information.

Planning Data Affected Reference

Spares Affected No Paragraph 1.A.2., Spares Affected

Paragraph 1.E., Compliance and Paragraph

1.F., Approval

AD Related Yes

Weight and Balance Change No Paragraph 1.H., Weight and Balance Changes

Electrical Load Changed No Paragraph 1.I., Electrical Load Data

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
Planning Data Affected Reference

Publications Affected No Paragraph 1.K., Publications Affected

Airplane Flight Operations Affected (Flight Crew No Paragraph 1.K., Publications Affected

Operations Manual and/or FAA Approved Airplane Flight Manual)

Kits/Parts Required No Paragraph 2.C.1., Kits/Parts

Paragraph 2.C.2., Parts and Materials Supplied

by the Operator

Operator Supplied Material Yes

Paragraph 2.F., Special Tooling Necessary to

do this Service Bulletin

Special Tooling Required No

ACTION

Do a Non-Destructive Test (NDT) eddy current inspection of the external fuselage crown lap joints (S-4L/R,

S-10L/R, and S-14L/R) between STA 360 and STA 908 at specific locations.

Get access to the interior fuselage and do Non-Destructive Test (NDT) eddy current and detailed inspections

of the internal fuselage crown lap joints (S-4L/R, S-10L/R, and S-14L/R) and detailed inspections of the stringer

clips between STA 360 and STA 908 at specific locations.

If no cracks are detected continue inspections in accordance with Paragraph 1.E., Compliance.

If any crack is found in a crown lap joint repair in accordance with 737-100/200 SRM 53-30-3, Figure 42, 737-300

SRM 53-00-01, Figure 201, Repair 30, 737-400 SRM 53-00-01, Figure 201, Repair 30 or 737-500 SRM 53-00-01,

Figure 201, Repair 30.

Replace any damaged stringer clips with new clips.

EFFECTIVITY

737-200/200C/300/400/500 Airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes.

COMPLIANCE

Federal Aviation Administration (FAA) Airworthiness Directive AD 2003-08-15 is related to this service bulletin.

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

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

bulletin.

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ALERT ALERT
MANPOWER

Refer to Paragraph 1.G. Manpower.

MATERIAL INFORMATION

None.

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BLANK PAGE
Commercial 

Airplanes 737

Service Bulletin

ALERT

Number: 737-53A1255

Original Issue: October 17, 2002

Revision 2: August 07, 2012

ATA System: 5331

SUBJECT: FUSELAGE - Skin - Crown Skin Lap Joint - Inspection for Lower Row Cracking at

Stringers S-4, S-10, S-14 Between STA 360 and STA 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

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

Number, and Serial Number data.

This service bulletin is for the airplanes shown below.

GROUP CONFIGURATION DESCRIPTION

737-200 airplanes with specific inspection zones S-14R/L STA 360

to STA 540 and STA 727 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, and S-4R/L STA 360 to STA 908.

1 -

737-200 airplanes with specific inspection zones S-14R/L STA 360

to STA 540 and STA 827 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, and S-4R/L STA 360 to STA 908

2 -

737-200C airplanes with specific inspection zones S-14R STA 360

to STA 540 and STA 727 to STA 908, S-10R STA 360 to STA 540

and STA 727 to STA 908, S-4R STA 360 to STA 908, S-4L STA 520

to STA 908, S-10L STA 727 to STA 908, and S-14L STA 727 to STA

908.

3 -

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GROUP CONFIGURATION DESCRIPTION

737-200C airplanes with specific inspection zones S14R/L STA 360

to STA 540 and STA 827 to STA 908, S-10R STA 360 to STA 540

and STA 727 to STA 908, S-4R STA 360 to STA 908, S-4L STA 520

to STA 908, S-10L STA 727 to STA 908, and S-14L STA 827 to STA

908

4 -

737-300 airplanes with specific inspection zones S-14R/L STA 360

to STA 540 and STA 827 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, and S-4R/L STA 360 to STA 908.

5 -

737-300 airplanes with specific inspection zones S-14R/L STA 360

to STA 540 and STA 827 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, and S-4R/L STA 360 to STA 540 and STA

727E to STA 908.

6 -

737-300 airplanes with specific inspection zones S-14R STA 360 to

STA 540 and STA 847 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, S-4R/L STA 360 to STA 908, S-14L STA

360 to STA 540 and STA 827 to STA 908.

7 -

737-300 airplanes with specific inspection zones S-14R STA 360 to

STA 540 and STA 847 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, S-4R/L STA 360 to STA 540 and STA

727E to STA 908, and S-14L STA 360 to STA 540 and STA 827 to

STA 908.

8 -

737-300 airplanes with specific inspection zones S-14R/L STA 360

to STA 540, S-10R/L STA 360 to STA 540 and STA 727 to STA 908,

and S-4R/L STA 360 to STA 908.

9 -

737-300 airplanes with specific inspection zones S-14R/L STA 360

to STA 540, S-10R/L STA 360 to STA 540 and STA 727 to STA 908,

and S-4R/L STA 360 to STA 540, STA 727E to STA 908.

10 -

737-300 airplanes with specific inspection zones S-14R/L STA 360

to STA 540.

11 -

737-400 airplanes with specific inspection zones S-14R STA 360 to

STA 540 and STA 847 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, S-4R/L STA 360 to STA 908, and S-14L

STA STA 360 to STA 540 and STA 827 To STA 908.

12 -

737-400 airplanes with specific inspection zones S-14R/L STA 360

to STA 540, S-10R/L STA 360 to STA 540 and STA 727 to STA 908,

and S-4R/L STA 360 to STA 908.

13 -

747-400 airplanes with specific inspection zones S-14R/L STA 360

to STA 540.

14 -

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GROUP CONFIGURATION DESCRIPTION

737-500 airplanes with specific inspection zones S-14R STA 360 to

STA 540 and STA 847 to STA 908, S-10R/L STA 360 to STA 540,

STA 727 to STA 908, S-4R/L STA 360 to STA 908 and S-14L STA

827 to STA 908.

15 -

737-500 airplanes with specific inspection zones S-14R STA 360 to

STA 540 and STA 847 to STA 908, S-10R/L STA 360 to STA 540

and STA 727 to STA 908, S-4R/L STA 360 to STA 540 and STA

727C to STA 908, and S-14L STA 360 to STA 540 and STA 827 to

STA 908.

16 -

737-500 airplanes with specific inspection zones S-14R/L STA 360

to STA 540, S-10R/L STA 360 to STA 540 and STA 727 to STA 908,

and S-4R/L STA 360 to STA 908.

17 -

737-500 airplanes with specific inspection zones S-14R/L STA 360

to STA 540.

18 -

Airplane Models:

737-200, 737-200C, 737-300, 737-400, 737-500

Variable Number Group

PG584 - PG586 1

PH001 1

PH011 - PH013 1

PH021 - PH024 1

PH743 1

PJ003 - PJ009 1

PJ105 - PJ119 1

PJ201 - PJ219 1

PJ301 - PJ302 12

PJ551 13

PJ552 14

PK026 - PK029 1

PK041 - PK053 1

PK061 - PK070 1

PK081 - PK082 1

PK091 - PK099 1

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ALERT ALERT
Variable Number Group

PK101 - PK103 1

PK111 - PK120 1

PK141 - PK146 1

PK201 - PK204 1

PK211 - PK215 1

PK216 - PK220 2

PK221 - PK223 1

PK231 - PK241 1

PK251 - PK258 1

PK271 - PK274 1

PK281 - PK289 1

PK291 1

PK301 - PK318 1

PK341 1

PK351 - PK361 1

PK391 1

PK431 - PK433 1

PK451 - PK452 1

PK461 - PK469 1

PK495 1

PK501 - PK504 1

PK511 - PK514 1

PK515 2

PK519 2

PK521 - PK525 1

PK526 - PK528 2

PK541 - PK564 1

PK565 2

PK581 1

PK591 - PK599 1

PK601 - PK617 1

PK621 - PK637 1

PK641 - PK642 1

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ALERT ALERT
Variable Number Group

PK661 - PK664 1

PK665 - PK666 2

PK671 - PK680 1

PK681 2

PK691 - PK697 1

PK711 - PK716 1

PK731 - PK749 1

PK750 - PK765 2

PK771 - PK779 1

PK801 - PK802 1

PK803 - PK804 2

PK819 - PK826 1

PK827 2

PK830 1

PK861 - PK863 1

PK871 - PK874 1

PK881 - PK884 1

PK901 - PK932 1

PK933 - PK938 2

PK971 - PK974 1

PL001 - PL026 1

PL027 - PL028 2

PL061 1

PL081 1

PL101 - PL113 1

PL151 1

PL171 - PL172 1

PL201 - PL203 1

PL221 1

PL401 - PL415 1

PL416 - PL417 2

PL421 1

PL441 1

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ALERT ALERT
Variable Number Group

PL451 - PL454 1

PL455 - PL456 2

PL471 1

PL491 1

PL501 - PL506 1

PL551 - PL562 1

PL581 1

PL601 1

PL602 - PL603 2

PL611 1

PL621 - PL626 2

PL631 - PL632 1

PL717 - PL745 1

PL746 - PL747 2

PL756 1

PL758 1

PL761 - PL770 1

PL781 - PL787 1

PL788 2

PL793 1

PM001 - PM006 1

PM016 - PM017 2

PM021 - PM023 1

PM051 - PM056 1

PM057 - PM066 2

PM101 - PM110 1

PM111 - PM119 2

PM141 - PM142 1

PM171 2

PM181 2

PM251 - PM255 2

PM281 - PM283 2

PM381 - PM395 5

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ALERT ALERT
Variable Number Group

PM396 - PM399 7

PM401 - PM417 7

PM541 7

PM542 9

PM543 - PM547 11

PM551 - PM564 12

PN001 - PN002 1

PN021 1

PN022 - PN043 2

PN081 - PN086 2

PN101 - PN117 2

PN131 - PN163 2

PN401 - PN420 2

PN431 - PN433 2

PN451 - PN456 2

PN471 - PN474 2

PN481 2

PN491 - PN493 2

PN501 - PN502 2

PN511 - PN512 2

PN521 2

PP001 - PP054 5

PP101 - PP126 5

PP127 - PP150 6

PP151 - PP160 8

PP161 - PP169 5

PP181 - PP199 5

PP201 - PP205 5

PP221 5

PP231 - PP243 5

PP281 - PP286 5

PP301 - PP305 5

PP351 - PP353 5

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ALERT ALERT
Variable Number Group

PP376 - PP384 5

PP391 - PP393 5

PP401 - PP440 5

PP471 - PP475 5

PP501 - PP510 5

PP511 - PP517 7

PP521 - PP522 5

PP631 - PP634 5

PP651 - PP652 5

PP671 - PP699 5

PP701 - PP733 5

PP771 - PP779 5

PP801 - PP808 5

PP821 - PP827 5

PP831 - PP848 5

PP851 - PP852 5

PP861 - PP873 5

PP874 - PP875 7

PP891 - PP899 5

PP901 - PP925 5

PP926 - PP930 7

PP931 - PP936 5

PP946 - PP948 5

PP951 - PP952 5

PP961 - PP967 5

PP981 - PP988 5

PP989 - PP990 7

PP991 5

PP993 5

PQ001 - PQ016 5

PQ026 - PQ041 5

PQ051 - PQ073 5

PQ074 - PQ085 7

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ALERT ALERT
Variable Number Group

PQ086 - PQ092 5

PQ101 - PQ199 5

PQ201 - PQ202 5

PQ221 - PQ229 5

PQ230 7

PQ231 - PQ236 5

PQ237 7

PQ241 - PQ243 5

PQ251 - PQ257 5

PQ258 - PQ267 7

PQ281 - PQ287 5

PQ288 - PQ296 7

PQ301 - PQ305 5

PQ306 - PQ307 7

PQ331 - PQ332 5

PQ341 - PQ344 7

PQ361 - PQ369 7

PQ401 - PQ406 7

PQ407 9

PQ408 11

PQ411 - PQ413 7

PQ421 7

PQ471 - PQ472 9

PQ473 11

PQ479 - PQ480 9

PQ481 7

PQ486 7

PQ487 9

PQ491 - PQ493 7

PQ771 7

PQ791 - PQ793 7

PQ801 - PQ803 7

PQ804 - PQ805 9

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ALERT ALERT
Variable Number Group

PQ931 - PQ932 9

PS601 - PS616 7

PS631 7

PS636 - PS638 7

PS641 - PS642 5

PS643 - PS644 7

PS651 - PS657 7

PS666 - PS668 5

PS669 7

PS691 - PS692 7

PS701 - PS703 7

PS751 - PS756 8

PS757 - PS762 10

PT001 - PT011 15

PT021 - PT027 15

PT028 17

PT041 - PT059 15

PT060 - PT063 17

PT064 18

PT101 - PT105 15

PT121 - PT125 15

PT146 - PT148 15

PT161 - PT170 15

PT181 - PT187 15

PT211 - PT220 15

PT295 15

PT301 - PT303 15

PT304 - PT306 17

PT331 - PT360 15

PT381 - PT399 15

PT401 - PT435 15

PT436 - PT438 17

PT501 - PT512 15

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ALERT ALERT
Variable Number Group

PT561 - PT565 15

PT581 - PT584 15

PT611 - PT621 15

PT641 - PT642 15

PT651 - PT655 15

PT671 - PT672 15

PT701 - PT703 15

PU001 - PU025 16

PV001 - PV055 12

PV201 - PV202 12

PV203 13

PV231 - PV237 12

PV271 - PV272 12

PV281 - PV282 12

PV283 13

PW001 - PW054 12

PW061 - PW068 12

PW072 12

PW091 - PW094 12

PW101 - PW102 12

PW106 12

PW111 - PW120 12

PW156 - PW157 12

PW161 - PW167 12

PW201 - PW223 12

PW224 - PW230 13

PW231 - PW240 12

PW241 - PW244 13

PW245 14

PW261 12

PW265 - PW268 12

PW278 13

PW281 12

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ALERT ALERT
Variable Number Group

PW282 - PW284 14

PW293 12

PW296 12

PW301 - PW323 12

PW324 - PW327 13

PW461 - PW467 13

PW501 - PW504 12

PW511 - PW520 12

PW526 12

PW531 - PW545 12

PW546 13

PW556 12

PW557 13

PW561 - PW564 12

PW571 - PW576 12

PW591 - PW596 12

PW611 - PW620 12

PW631 - PW634 12

PW661 - PW662 12

PW681 - PW683 12

PW701 - PW702 12

PW711 - PW717 12

PW741 - PW742 12

PW761 12

PW771 12

PY022 3

PY036 - PY037 3

PY046 - PY048 3

PY051 - PY053 3

PY056 - PY057 3

PY101 - PY103 3

PY111 - PY113 3

PY131 - PY135 3

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ALERT ALERT
Variable Number Group

PY141 - PY143 3

PY151 - PY154 3

PY156 - PY157 3

PY161 - PY162 3

PY166 3

PY191 3

PY201 3

PY221 - PY222 3

PY231 3

PY241 - PY244 3

PY270 - PY275 3

PY281 3

PY286 3

PY401 3

PY409 - PY410 4

PY411 3

PY421 - PY422 3

PY441 3

PY451 3

PY461 - PY462 3

PY463 4

PY591 - PY595 4

PY611 - PY612 3

PY621 3

PY631 3

PY651 3

PY671 - PY672 3

PY721 3

PY741 3

2. Spares Affected

None.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
B. Concurrent Requirements

None.

C. Reason

This service bulletin outlines additional inspection requirements with reduced compliance times from

that described in service bulletin 737-53A1177 for stringer S-4L & S-4R skin lap joints between STA

360-STA 908, S-10L, S-10R, S-14L, S-14R between STA 360-STA 540 and STA 727-STA 908.

Two findings, one discovered on September 11, 2002 on a 737-300 with 52,400 flight cycles and the

other discovered on December 31, 2001 on a 737-200 with 60,333 flight cycles have caused increased

concern with the extent of lap joint lower row cracking.

On December 31, 2001 during a walk-around inspection, on a 737-200 with 60,333 flight cycles, a 23

inch long crack was found in the lower row of the stringer S-4L lap joint between STA 616 and STA

639. The technician noticed the crack above the over-wing exit, because the lower skin was pushed

outward approximately 1 inch with the crack ends turning downward at the tear straps. There was no

report from the flight crew of pressurization problems or from passenger or cabin crew of any abnormal

noise in the area. The operator elected to inspect the lap joint for additional cracks using external and

internal NDT methods. Additional cracks were found. Following a local repair of the 23 inch long crack

the operator ferried the airplane unpressurized to a maintenance facility to perform the 737-53A1177

lap joint modification. The removed lap joints were inspected by Boeing NDT personnel using the

current methods referenced in service bulletin 737-53A1177 and significantly more cracking was found.

Boeing is concerned about the extent of cracking both forward and aft of the 23 inch long cracked

section. Cracks were found in between the tear straps and in the skin at locations common to the tear

straps. The in-tact tear straps were able to turn the cracks as they were designed to do. However, due

to the condition of the skin at the tear straps forward and aft of the 23 inch crack area, it is likely that

similar crack link-up just forward in an area which had a higher percentage of cracked fastener holes

could have resulted in an uncontained decompression. Of great importance is the total number and

length of cracks found at this particular lap joint. The damage observed is believed to exceed all prior

in-service crack findings and Boeing predictions based on test and analysis for an airplane with 60,000

flight cycles.

On September 11, 2002 Boeing NDT personnel, while assisting an operator of a 737-300 with 52,400

flight cycles, discovered significant cracking on the stringer S-4R lap joint between STA 600 and STA

727. At one location between STA 639 and STA 650, every fastener hole (11 total) had a crack of over

0.5 inches emanating from each side. Although the individual cracks had not yet linked up, it was clear

that within a few number of flights the cracks would have linked up with a length of over 10 inches.

Forward of this section between STA 636 and STA 620, 15 fastener holes in a row were cracked. This

included the skin common to the tear strap at STA 630. Although these cracks were only 0.2 inches

long, there were only 4 crack free fastener holes separating the two cracked areas. Additionally, 3

stringer clips common to S-4 were found to be cracked. The clip at STA 639 was completely severed

and the clips at STA 616 and STA 663.75 were partially cracked. Stringer clips were redesigned

beginning at line position 1001. Service bulletin 737-53-1268, which superseded service bulletin

737-53-1085 provides retrofit instructions for airplanes built prior to line position 1001. Service bulletin

737-53-1268 also inspects for damaged stringer clips for airplanes line positions 1001 to 3132. The

cracks in the lap joints were found using the LFEC external inspection method and verified using the

MFEC inspection method which are called out in service bulletin 737-53A1177. Previous inspection

by the operator found significantly less cracking. Boeing NDT personnel were able to locate over eight

times as many cracks.

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ALERT ALERT
If the cracks continue to grow undetected they will link-up. Independent large scale fatigue testing at

Boeing has shown that this extent of cracking can result in an uncontrolled decompression.

Since the release of service bulletin 737-53A1177 Revision 6 and the original issue of this service

bulletin there have been many reports of crack findings. On 33 airplanes between 36,781 flight cycles

and 68,884 flight cycles lap joint damage has been found, with cracking lengths ranging from 0.03

inches to 0.10 inches, with the exception of the more significant cracking noted above. Cracks have

also been found in lap joint lower skins that do not intersect fastener holes. Boeing has completed a

re-evaluation of the compliance requirements for the lap joints. As a result of the re-evaluation the

inspection recommendations of the crown lap joints between STA 360 - STA 908 are updated. This

update includes a reduced inspection threshold and repeat inspections. Accomplishment of service

bulletin 737-53A1177 lap joint modification is mandated by AD 2002-07-08 to be accomplished before

50,000 total flight cycles.

Boeing Service Related Problem (SRP) 737-SRP-53-0372 is related to this service bulletin.

Revision 1 was sent to revise compliance times, add repeat inspection intervals, and revise inspection

zones for the crown lap joints. The effectivity is now divided into eighteen groups, these new groups

cover the different inspection requirements for each group. Airplanes PJ552, PM543-PM547,

PP127-PP160, PQ408, PQ473, PS751-PS762, PT064, PU001-PU025 and PW245, PW282-PW284

are added to the service bulletin effectivity. Some airplanes previously in Group 1 are moved to Groups

2, 3, 4, 5, 7, 9, 12, 13, 15 and 17.

Revision 2 is sent to incorporate additional compliance notes in Paragraph 1.E., Compliance and

additional inspection notes in Paragraph 3.B., Work Instructions.

D. Description

Do a Non-Destructive Test (NDT) eddy current inspection of the external fuselage crown lap joints

(S-4L/R, S-10L/R, and S-14L/R) between STA 360 and STA 908 at specific locations.

Get access to the interior fuselage and do Non-Destructive Test (NDT) eddy current and detailed

inspections of the internal fuselage crown lap joints (S-4L/R, S-10L/R, and S-14L/R) and detailed

inspections of the stringer clips between STA 360 and STA 908 at specific locations.

If no cracks are detected continue inspections in accordance with Paragraph 1.E., Compliance.

If any crack is found in a crown lap joint repair in accordance with 737-100/200 SRM 53-30-3, Figure

42, 737-300 SRM 53-00-01, Figure 201, Repair 30, 737-400 SRM 53-00-01, Figure 201, Repair 30 or

737-500 SRM 53-00-01, Figure 201, Repair 30.

Replace any damaged stringer clips with the same part number.

Revision 2 - No more work is necessary on airplanes inspected in accordance with Revision 1 of this

service bulletin.

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

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ALERT ALERT
Group 1-2:

Affected Maintenance Zones

Model Zone

737-200 1-7, 1-8

Group 3-4:

Affected Maintenance Zones

Model Zone

737-200C 1-7, 1-8

Group 5-11:

Affected Maintenance Zones

Model Zone

737-300 107, 108

Group 12-14:

Affected Maintenance Zones

Model Zone

737-400 107, 108

Group 15-18:

Affected Maintenance Zones

Model Zone

737-500 107, 108

E. Compliance

Federal Aviation Administration (FAA) Airworthiness Directive AD 2003-08-15 is related to this service

bulletin.

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.

Definition of crown lap joint over wing and non over wing locations.

Over wing S-4L/R between STA 540 and STA 727

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ALERT ALERT
Definition of crown lap joint over wing and non over wing locations.

S-4L/R, S-10L/R and S-14L/R between STA 360 and STA 540 and S-4L/R, S-10L/R

and S-14L/R between STA 727 and STA 908

Non over wing

Table 1: Inspection for cracking at crown lap joints.

Repeat Interval (Not to

Exceed) (a)

Condition Action (d) Compliance Time (a)

Before 35,000 total -

flight cycles, or within

2,500 flight cycles from

the Revision 1 date of

this service bulletin,

whichever is later.

Do an initial external Eddy Current inspection

of the crown lap joints for cracks in accordance

with Accomplishment Instructions 3.B.1.

Airplanes

with less

than

35,000 total flight cycles at the

Revision 1

date of this

service

bulletin.

2,500 flight cycles until

the Option 1 or Option 2

inspections are started.

Within 2,500 flight cycles after the initial external eddy current inspection.Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Do one of the options that follow: - -

OPTION 1:

Before 40,000 total -

flight cycles, not to exceed 2,500 flight cycles

after the external inspection, but not before

37,500 total flight cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

OR OPTION 2:

1,700 flight cycles until

the internal Eddy Current

and detailed inspections

are accomplished.

Before 40,000 total

flight cycles.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Before 45,000 total -

flight cycles, not to exceed 1,700 flight cycles

after the external inspection, but but not

before 37,500 total

flight cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
Table 1: Inspection for cracking at crown lap joints.

Repeat Interval (Not to

Exceed) (a)

Condition Action (d) Compliance Time (a)

Airplanes OPTION 1:

with more

than

34,999

and less

than

37,500 total flight cycles at the

Revision 1

date of this

service

bulletin.

Do one of

the options

that follow:

2,500 flight cycles until

the internal Eddy Current

and detailed inspections

are accomplished.

Within 2,500 flight cycles from the Revision

1 date of this service

bulletin.

Do an initial external Eddy Current inspection

of the crown lap joints for cracks in accordance

with Accomplishment Instructions 3.B.1.

Before 40,000 total -

flight cycles but not before 37,500 total flight

cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

OR OPTION 2:

2,500 flight cycles until

39,999 maximum total

flight cycles.

Within 2,500 flight cycles from the Revision

1 date of this service

bulletin.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

1,700 flight cycles until

the internal Eddy Current

and detailed inspections

are accomplished.

Before 40,000 total

flight cycles.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Before 45,000 total -

flight cycles, not to exceed 1,700 flight cycles

after the external inspection.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

OR OPTION 3

Within 2,500 flight cy- -

cles from the Revision

1 date of this service

bulletin, and before

40,000 total flight cycles, but not before

37,500 total airplane

flight cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
Table 1: Inspection for cracking at crown lap joints.

Repeat Interval (Not to

Exceed) (a)

Condition Action (d) Compliance Time (a)

Airplanes Do one of the options that follow: - -

with more

than

37,499

and less

than

40,000 total flight cycles at the

Revision 1

date of this

service

bulletin.

Do one of

the options

that follow:

OPTION 1:

Within 2,500 flight cy- -

cles from the Revision

1 date of this service

bulletin but not to exceed 41,699 total flight

cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

OR OPTION 2:

1,700 flight cycles until

the internal Eddy Current

and detailed inspections

are accomplished.

Within 2,500 flight cycles from the Revision

1 date of this service

bulletin but not to exceed 41,699 total flight

cycles.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Before 45,000 total -

flight cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

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ALERT ALERT
Table 1: Inspection for cracking at crown lap joints.

Repeat Interval (Not to

Exceed) (a)

Condition Action (d) Compliance Time (a)

Airplanes Do one of the options that follow: - -

with more

than

39,999

and less

than

43,300 total flight cycles at the

Revision 1

date of this

service

bulletin.

Do one of

the options

that follow:

OPTION 1:

Within 1,700 flight cy- -

cles from the Revision

1 date of this service

bulletin.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

OR OPTION 2:

1,700 flight cycles until

the internal Eddy Current

and detailed inspections

are accomplished.

Within 1,700 flight cycles from the Revision

1 date of this service

bulletin.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Before 45,000 total -

flight cycles.

Do an internal Eddy Current inspection and

detailed inspection of the crown lap joints and

do a detailed inspection of the stringer clips for

cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Before 45,000 total -

flight cycles. (c)

Do an internal Eddy Current inspection and

detailed inspection of the over wing crown lap

joints and do a detailed inspection of the

stringer clips for cracks in accordance with Accomplishment Instructions 3.B.2.

Airplanes

with more

than

43,299

and less

than

45,000 total flight cycles at the

Revision 1

date of this

service

bulletin.

Within 1,700 total flight -

cycles from the Revision 1 date of this service bulletin.

Do an internal Eddy Current inspection and

detailed inspection of the non over wing crown

lap and do a detailed inspection of the stringer

clips for cracks in accordance with Accomplishment Instructions 3.B.2.

Within 2,500 flight cy- 2,500 flight cycles.

cles after the internal

inspection of the non

over wing crown lap

joints, but not to exceed

48,750 total flight cycles.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

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ALERT ALERT
Table 1: Inspection for cracking at crown lap joints.

Repeat Interval (Not to

Exceed) (a)

Condition Action (d) Compliance Time (a)

Within 2,500 flight cy- 2,500 flight cycles

cles after the Revision

1 date of this service

bulletin.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Airplanes

with more

than

44,999

and less

than

46,251 total flight cycles at the

Revision 1

date of this

service

bulletin.

Before 48,750 total -

flight cycles.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Airplanes

with more

than

46,250

and less

than

47,501 total flight cycles at the

Revision 1

date of this

service

bulletin.

Within 1,250 flight cy- -

cles after the Revision

1 date of this service

bulletin.

Do an external Eddy Current inspection of the

crown lap joints for cracks in accordance with

Accomplishment Instructions 3.B.1.

Airplanes

with more

than

47,500

and less

than

48,751 total flight cycles at the

Revision 1

date of this

service

bulletin.

Repair the lap joint in accordance with Accom- Before further flight. -

plishment Instructions 3.B.1 or 3.B.2.b as applicable.

Any crack

found in a

lap joint.

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ALERT ALERT
Table 1: Inspection for cracking at crown lap joints.

Repeat Interval (Not to

Exceed) (a)

Condition Action (d) Compliance Time (a)

Replace the damaged stringer clip in accor- Before further flight. -

dance with Accomplishment Instructions

3.B.2.b.

Any

stringer

clip damage found.

Before 50,000 total -

flight cycles. (b)

Do the modification to the crown lap joints in

accordance with service bulletin 737-53A1177.

All airplanes.

(a) Accomplishment of the crown lap joint repair (modification) in accordance with service bulletin 737-53A1177

terminates the Table 1 inspections in the modified area.

(b) This action is mandated by AD 2002-07-08.

(c) Unless already accomplished in accordance with the original issue of this service bulletin.

(d) Actions are for over wing and non over wing crown lap joints unless otherwise stated.

NOTE:

1. For lap joint areas that have an SRM or Boeing approved repair doubler:

– If the repair doubler has at least three rows of fasteners above the lap joint

fasteners and three rows of fasteners below the lap joint fasteners, then it is not

necessary to do an inspection of the lap joint lower row under the repair doubler.

– If an SRM repair listed in Table 3 of paragraph 1.E. Compliance of service bulletin

737-53A1177, Revision 6 was installed, inspections are not necessary. However,

the repair should be replaced with the applicable cutout repair or a Boeing

approved repair in accordance with the compliance times of AD 2002-07-10.

– If an SRM repair doubler was installed to repair lap joint lower row damage

following the instructions of SB 737-53A1255 or SB 737-53A1177 and the repair

extends at least three fastener rows below the lap joint and two fastener rows

above the lap joint, then it is not necessary to do an inspection of the lap joint

lower row under the repair doubler.

2. Skin repair doublers that end on the lower row of a lap joint further degrade the

fatigue life and accelerate cracking in the lower skin. Contact Boeing for alternate

lap joint inspection and modification instructions for areas with repair doublers ending

on the lower row.

3. If the airplane has had a skin panel replaced, the compliance times for inspection

and modification of the upper lap joint and lower lap joint may be affected. Contact

Boeing for alternate lap joint inspection and modification instructions for lap joint

areas affected by skin panel replacements.

4. Credit for accomplishment of the inspections at non-over wing lap joints (outside

STA 540 through STA 727), mandated by paragraph (d) and (e) of AD 2003-08-15,

resulting from "significant" crack findings at the S-4L or S-4R lap joints between STA

540 and STA 727, is not provided for by this compliance table.

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ALERT ALERT
5. Damage Tolerance Post Repair Inspection:

Damage tolerance post repair inspections for the SRM repairs referenced in this

service bulletin are specified within each of the SRM repairs.

F. Approval

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

in this service bulletin comply with the applicable Federal Aviation Regulations (FAR) and are FAA

approved. This service bulletin and the FAA approval were based on the airplane in its original Boeing

delivery configuration or as modified by other FAA 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.

Final approval from the FAA is required for repair instructions provided by Boeing, that are not defined

within this service bulletin.

The Manager of the FAA Seattle Aircraft Certification Office approves accomplishment of the repairs

defined in service bulletin 737-53A1255, Revision 2 and 737-53A1177, Revision 6, as an alternative

method of compliance to the inspections and repairs, as applicable, within the areas covered by the

repair parts only required by the following airworthiness directives (AD) and paragraphs:

– AD 89-09-03, A.1 Amendment 39-6184 Service Bulletin 737-53A1039

– AD 88-22-11 R1 H.1.b Amendment 39-6432 Service Bulletin 737-53A1039

– AD 92-25-09, d3 and g Amendment 39-8424 Service Bulletin 737-53-1076

– AD 90-06-02 A Amendment 39-6489

– AD 91-07-04, C and D Amendment 39-6933 Service Bulletin 737-53-1078

– AD 91-08-12, B.2.c, B.4 and C Amendment 39-6967 Service Bulletins 737-53A1039, 737-53-1076,

737-53A1089 and 737-53-1124

– AD 89-22-04 A and B Amendment 39-6355 Service Bulletin 737-53A1135

This service bulletin has been approved by the FAA. In addition, the Manager of the FAA Seattle Aircraft

Certification Office approves the repairs defined in this service bulletin as an alternative method of

compliance to the requirements of paragraph (d) of AD 2002-07-08. When this service bulletin specifies

contacting Boeing for repair instructions, the repair instructions must be approved by the FAA in

accordance with paragraph (o) of AD 2002-07-08. All provisions of AD 2002-07-08 that are not specifically

referenced in the above statement remain fully applicable and must be complied with accordingly.

This service bulletin has been approved by the FAA. In addition, the Manager of the FAA Seattle Aircraft

Certification Office approves the inspections and repairs defined in this service bulletin as an alternative

method of compliance to the requirements of paragraphs (a), (b), (c)(1), (d), (e) and (f)(1) of AD

2003-08-15. All provisions of AD 2003-08-15 that are not specifically referenced in the above statement

remain fully applicable and must be complied with accordingly.

This service bulletin has been approved by the FAA. In addition, the Manager of the FAA Seattle Aircraft

Certification Office approves the repairs defined in this service bulletin as an alternative method of

compliance to the requirements of paragraphs (a) and (b) of AD 2004-18-06, for areas covered by the

repair only. All provisions of AD 2004-18-06 that are not specifically referenced in the above statement

remain fully applicable and must be complied with accordingly.

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ALERT ALERT
The SRM repairs defined in this service bulletin may be subject to Federal Aviation Administration(FAA)

Airworthiness Directive (AD) AD 98-11-04 R1, AD 2008-08-23, and AD 2008-09-13. Refer to the

specified SRM repair used to determine if any SSI listed in the Supplemental Structural Inspection

Documents (SSID) D6-37089 or D6-82669 may have been affected. An evaluation of these SRM repairs

has been accomplished and any affects on SSID inspections are contained in the SRM repair.

G. Manpower

The table below shows an estimate of the task-hours necessary to do this one time internal 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 examine the work

— Time to cure the materials

— Time to make the parts

— Time to find the tools.

Group 1:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 115.00 28.75

Figure 3 4 19.00 4.75

Close Access 4 115.00 28.75

TOTAL FOR EACH AIRPLANE (a) 249.00 62.25

(a) Additional hours will be required for repair if any crack is found.

Group 1:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 3 2 8.00 4.00

TOTAL FOR EACH AIRPLANE (a) 8.00 4.00

(a) Additional hours will be required for repair if any crack is found.

Group 2:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 104.00 26.00

Figure 4 4 17.00 4.25

Close Access 4 104.00 26.00

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ALERT ALERT
Group 2:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

TOTAL FOR EACH AIRPLANE (a) 225.00 56.25

(a) Additional hours will be required for repair if any crack is found.

Group 2:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 4 2 8.00 4.00

TOTAL FOR EACH AIRPLANE (a) 8.00 4.00

(a) Additional hours will be required for repair if any crack is found.

Group 3:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 99.00 24.75

Figure 5 4 15.00 3.75

Close Access 4 99.00 24.75

TOTAL FOR EACH AIRPLANE (a) 213.00 53.25

(a) Additional hours will be required for repair if any crack is found.

Group 3:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 5 2 7.00 3.50

TOTAL FOR EACH AIRPLANE (a) 7.00 3.50

(a) Additional hours will be required for repair if any crack is found.

Group 4:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 84.00 21.00

Figure 6 4 13.00 3.25

Close Access 4 84.00 21.00

TOTAL FOR EACH AIRPLANE (a) 181.00 45.25

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ALERT ALERT
Group 4:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

(a) Additional hours will be required for repair if any crack is found.

Group 4:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 6 2 6.50 3.25

TOTAL FOR EACH AIRPLANE (a) 6.50 3.25

(a) Additional hours will be required for repair if any crack is found.

Group 5:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 115.00 28.75

Figure 7 4 20.00 5.00

Close Access 4 115.00 28.75

TOTAL FOR EACH AIRPLANE (a) 250.00 62.50

(a) Additional hours will be required for repair if any crack is found.

Group 5:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 7 2 8.50 4.25

TOTAL FOR EACH AIRPLANE (a) 8.50 4.25

(a) Additional hours will be required for repair if any crack is found.

Group 6:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 101.00 25.25

Figure 8 4 17.00 4.25

Close Access 4 101.00 25.25

TOTAL FOR EACH AIRPLANE (a) 219.00 54.75

(a) Additional hours will be required for repair if any crack is found.

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ALERT ALERT
Group 6:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 8 2 7.50 3.75

TOTAL FOR EACH AIRPLANE (a) 7.50 3.75

(a) Additional hours will be required for repair if any crack is found.

Group 7:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 121.00 30.25

Figure 9 4 20.00 5.00

Close Access 4 121.00 30.25

TOTAL FOR EACH AIRPLANE (a) 262.00 65.50

(a) Additional hours will be required for repair if any crack is found.

Group 7:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 9 2 8.50 4.25

TOTAL FOR EACH AIRPLANE (a) 8.50 4.25

(a) Additional hours will be required for repair if any crack is found.

Group 8:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 101.00 25.25

Figure 10 4 17.00 4.25

Close Access 4 101.00 25.25

TOTAL FOR EACH AIRPLANE (a) 219.00 54.75

(a) Additional hours will be required for repair if any crack is found.

Group 8:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 10 2 7.50 3.75

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ALERT ALERT
Group 8:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

TOTAL FOR EACH AIRPLANE (a) 7.50 3.75

(a) Additional hours will be required for repair if any crack is found.

Group 9:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 115.00 28.75

Figure 11 4 19.00 4.75

Close Access 4 115.00 28.75

TOTAL FOR EACH AIRPLANE (a) 249.00 62.25

(a) Additional hours will be required for repair if any crack is found.

Group 9:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 11 2 8.00 4.00

TOTAL FOR EACH AIRPLANE (a) 8.00 4.00

(a) Additional hours will be required for repair if any crack is found.

Group 10:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 100.00 25.00

Figure 12 4 16.00 4.00

Close Access 4 100.00 25.00

TOTAL FOR EACH AIRPLANE (a) 216.00 54.00

(a) Additional hours will be required for repair if any crack is found.

Group 10:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 12 2 7.00 3.50

TOTAL FOR EACH AIRPLANE (a) 7.00 3.50

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ALERT ALERT
Group 10:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

(a) Additional hours will be required for repair if any crack is found.

Group 11:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 27.00 6.75

Figure 13 1 4.00 4.00

Close Access 4 27.00 6.75

TOTAL FOR EACH AIRPLANE (a) 58.00 17.50

(a) Additional hours will be required for repair if any crack is found.

Group 11:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 13 1 2.50 2.50

TOTAL FOR EACH AIRPLANE (a) 2.50 2.50

(a) Additional hours will be required for repair if any crack is found.

Group 12:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 140.00 35.00

Figure 14 4 23.00 5.75

Close Access 4 140.00 35.00

TOTAL FOR EACH AIRPLANE (a) 303.00 75.75

(a) Additional hours will be required for repair if any crack is found.

Group 12:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 14 2 9.50 4.75

TOTAL FOR EACH AIRPLANE (a) 9.50 4.75

(a) Additional hours will be required for repair if any crack is found.

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ALERT ALERT
Group 13:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 135.00 33.75

Figure 15 4 22.00 5.50

Close Access 4 135.00 33.75

TOTAL FOR EACH AIRPLANE (a) 292.00 73.00

(a) Additional hours will be required for repair if any crack is found.

Group 13:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 15 2 9.00 4.50

TOTAL FOR EACH AIRPLANE (a) 9.00 4.50

(a) Additional hours will be required for repair if any crack is found.

Group 14:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 27.00 6.75

Figure 16 1 4.00 4.00

Close Access 4 27.00 6.75

TOTAL FOR EACH AIRPLANE (a) 58.00 17.50

(a) Additional hours will be required for repair if any crack is found.

Group 14:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 16 1 2.50 2.50

TOTAL FOR EACH AIRPLANE (a) 2.50 2.50

(a) Additional hours will be required for repair if any crack is found.

Group 15:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 115.00 28.75

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ALERT ALERT
Group 15:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 17 4 20.00 5.00

Close Access 4 115.00 28.75

TOTAL FOR EACH AIRPLANE (a) 250.00 62.50

(a) Additional hours will be required for repair if any crack is found.

Group 15:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 17 2 8.00 4.00

TOTAL FOR EACH AIRPLANE (a) 8.00 4.00

(a) Additional hours will be required for repair if any crack is found.

Group 16:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 99.00 24.75

Figure 18 4 15.00 3.75

Close Access 4 99.00 24.75

TOTAL FOR EACH AIRPLANE (a) 213.00 53.25

(a) Additional hours will be required for repair if any crack is found.

Group 16:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 18 2 7.00 3.50

TOTAL FOR EACH AIRPLANE (a) 7.00 3.50

(a) Additional hours will be required for repair if any crack is found.

Group 17:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 104.00 26.00

Figure 19 4 18.00 4.50

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ALERT ALERT
Group 17:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Close Access 4 104.00 26.00

TOTAL FOR EACH AIRPLANE (a) 226.00 56.50

(a) Additional hours will be required for repair if any crack is found.

Group 17:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 19 2 7.00 3.50

TOTAL FOR EACH AIRPLANE (a) 7.00 3.50

(a) Additional hours will be required for repair if any crack is found.

Group 18:

Internal Inspection

Task Number of Persons Task-Hours Elapsed Hours

Open Access 4 27.00 6.75

Figure 20 1 4.00 4.00

Close Access 4 27.00 6.75

TOTAL FOR EACH AIRPLANE (a) 58.00 17.50

(a) Additional hours will be required for repair if any crack is found.

Group 18:

External Inspection

Task Number of Persons Task-Hours Elapsed Hours

Figure 20 1 2.50 2.50

TOTAL FOR EACH AIRPLANE (a) 2.50 2.50

(a) Additional hours will be required for repair if any crack is found.

H. Weight and Balance Changes

None.

I. Electrical Load Data

Not applicable.

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ALERT ALERT
J. References

1. Existing Data:

a. Boeing Service Bulletin 737-53-1076, 737-53-1078, 737-53-1085, 737-53-1124, 737-53-1268,

737-53A1039, 737-53A1089, 737-53A1135, 737-53A1177, 737-53-1179, 737-53A1255

b. Boeing Service Related Problem (SRP) 737-SRP-53-0372

c. Federal Aviation Administration (FAA) Airworthiness Directive (AD) 2002-07-08, 2002-07-10,

2003-08-15, 2004-18-06, 2008-08-23, 2008-09-13, 88-22-11 R1, 89-09-03, 89-22-04, 90-06-02,

91-07-04, 91-08-12, 92-25-09, 98-11-04 R1, 2009-04-15

d. Standard Wiring Practices Manual (SWPM) 20-10-11, 20-10-12, 20-10-19

e. 737 Non-Destructive Testing (NDT) Manual Part 6, 51-00-00, Part 6, 53-30-00, Part 6, 53-30-12,

Part 6, 53-30-16

f. 737-100/200 Aircraft Maintenance Manual (AMM) 25-21-311, 25-21-341, 25-21-347, 25-22-0,

25-23-311, 25-24-311

g. 737-100/200 Structural Repair Manual (SRM) 53-30-3

h. 737-300/400/500 Aircraft Maintenance Manual (AMM) 25-21-39, 25-21-45, 25-21-46, 25-22-00,

25-23-61, 25-24-31

i. 737-300 Structural Repair Manual (SRM) 53-00-01

j. 737-400 Structural Repair Manual (SRM) 53-00-01

k. 737-500 Structural Repair Manual (SRM) 53-00-01

2. Data Supplied with this Service Bulletin:

None.

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

Drawing Number Title

65C38450 Top Kit - Skin Lap Repair, S-4, STA 360 - 908

65C38451 Top Kit - Skin Lap Repair, S-10, STA 360 - 540, 727 - 908

65C38452 Top Kit - Skin Lap Repair, S-14, STA 360 - 540

65-73742 Skin Diagram - Body-Model 737

65C37852 Top Kit - Stringer Tie Clip

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

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

not be applicable to all airplane configurations or operators.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
K. Publications Affected

1. Publications:

None.

2. Damage Tolerance Based Structural Inspections:

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

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

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

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

L. Interchangeability and Intermixability of Parts

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

M. Software Accomplishment Summary

Not affected.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
2. MATERIAL INFORMATION

A. Material - Price and Availability

None.

B. Industry Support Information

Boeing warranty remedies are not available for the inspection, and/or 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:

A new stringer clip will be necessary at any location where a stringer clip is found to be cracked.

The part number for the replacement stringer clip should be determined from the damaged stringer

clip.

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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ALERT ALERT
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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT

BLANK PAGE
3. ACCOMPLISHMENT INSTRUCTIONS

A. GENERAL INFORMATION

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

PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL,

METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE

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

OTHER ELECTRICAL DAMAGE.

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

definition of the acronyms.

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

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

– Linear dimensions are in inches

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

or minus 0.03 inch

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

– Angular tolerance is plus or minus 2 degrees

– Hole dimensions for standard solid rivets and fasteners are in Structural Repair

Manual (SRM) Chapter 51

– Torque limits to tighten nuts and bolts are in SRM Chapter 51.

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

SRM Chapter 51. Alternate fasteners are listed in SRM Chapter 51.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
10. It is extremely important that operators and operator personnel pay close attention

to the notes and instructions that follow for the continued safety of the airplane.

As described previously in the Reason section of this service bulletin, 737-53A1177

lap joint inspections accomplished by some operators followed by Boeing inspections

have resulted in significantly greater numbers of crack findings by Boeing. Service

experience with these inspections has shown that the missed crack indications can

be attributed to human-factors reasons, including but not limited to:

— Inadequate understanding of the inspection procedures.

— Incorrect or faulty NDT standards.

— Improper set-up and calibration of equipment prior to inspection.

— Improper monitoring of the NDT instrument display.

— Inadequate time to conduct the inspections.

— Inadequate access to the inspection areas.

— Improper documentation of areas not inspected or remaining to be inspected

due to shift changes or breaks during the inspection, resulting in areas missed.

— Improper documentation of inspection findings.

Given the sensitivity of these inspections and the consequences of missing significant

lower row cracking, Boeing recommends operators make sure the NDT technicians

who accomplish these inspections be trained on and are experienced with the NDT

procedures defined in this service bulletin.

If there are any questions or concerns about the NDT procedures or inspections

described in the 737 NDT Manual or this service bulletin, the operator should contact

Boeing Commercial Airplane Group through the normal communication channels.

B. WORK INSTRUCTIONS

1. PART 1 - EXTERNAL CROWN LAP JOINT INSPECTION

a. Do external eddy current inspections as follows:

NOTE: The following two notes apply to All Groups.

1. If a fastener is magnetic or if a fastener has a protruding head, the Figure

2 external inspection at the fastener hole in accordance with 737 NDT Part

6, 53-30-00, Figure 9, cannot be done. If a fastener is magnetic or has a

protruding head, internal inspection in accordance with Figure 1 must be

done at the fastener location.

2. Inspect for white powder, skin bulging, or other signs of corrosion in these

areas when accomplishing the eddy current inspection or when an SRM

repair is being installed. If corrosion is discovered, contact Boeing for repair

instructions and do the repair.

Group 1:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 3.

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ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 2:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 4.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 3:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 5.

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ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 4:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 6.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 5:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 7.

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ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 6:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 8.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 7:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 9.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 8:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 10.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 9:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 11.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 10:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 12.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 11:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 13.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 12:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 14.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-400 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 13:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 15.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-400 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 14:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 16.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-400 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 15:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 17.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 16:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 18.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 17:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 19.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

Group 18:

(1) Do inspections for cracks in the crown lap joints in accordance with FIGURE 2 at the

locations given in FIGURE 20.

(a) If no cracks are found continue inspections in accordance with Paragraph 1.E.,

Compliance.

(b) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Mid-bay fastener locations (between tear straps):

As an option to confirm crack indications between tear straps do

an internal Medium Frequency Eddy Current (MFEC) inspection

for cracking in the lap joint fastener row between tear straps in

accordance with 737 NDT Part 6, 53-30-16 and do a detailed

inspection of the lap joint lower fastener row for cracking.

2. Tear strap fastener locations:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

(c) Put the airplane back to a serviceable condition.

2. PART 2 - INTERNAL CROWN LAP JOINT INSPECTION

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
a. Get access to the interior of the fuselage as required for a eddy current and detailed

inspections. Refer to the table below for access information. Remove panels and equipment

in the areas of inspection as necessary.

737-300/-400/-500

AMM Subject

737-200 AMM

Subject

Equipment

737-300/400/500

AMM 25-21-45

737-100/200 AMM

25-21-341

Ceiling Panels

737-300/400/500

AMM 25-24-31

737-100/200 AMM

25-24-311

Overhead Stowage Bins

737-300/400/500

AMM 25-21-46

737-100/200 AMM

25-21-311

Sidewall Linings

737-300/400/500

AMM 25-21-39

737-100/200 AMM

25-21-347

Sidewall Insulation

737-300/400/500

AMM 25-22-00

737-100/200 AMM

25-22-0

Passenger Seats

737-300/400/500

AMM 25-23-61

737-100/200 AMM

25-23-311

Passenger Service Units

b. Do an internal (MFEC) Medium Frequency Eddy Current, (LFEC) Low Frequency Eddy Current

and a detailed inspection as follows:

NOTE: The following note applies to All Groups.

1. Inspect for white powder, skin bulging, or other signs of corrosion in these

areas when accomplishing the eddy current inspection or when an SRM

repair is being installed. If corrosion is discovered, contact Boeing for repair

instructions and do the repair.

Group 1:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 3.

(a) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

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ALERT ALERT
(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 2:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 4.

(a) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 3:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 5.

(a) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 4:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 6.

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BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
(a) If any crack is found in a lap joint do the repair in accordance with 737-100/200 SRM

53-30-3, Figure 42.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 5:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 7.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 6:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 8.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

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ALERT ALERT
As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 7:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 9.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 8:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 10.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

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ALERT ALERT
Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 9:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 11.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 10:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 12.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

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ALERT ALERT
Group 11:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 13.

(a) If any crack is found in a lap joint do the repair in accordance with 737-300 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 12:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 14.

(a) If any crack is found in a lap joint do the repair in accordance with 737-400 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 13:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 15.

(a) If any crack is found in a lap joint do the repair in accordance with 737-400 SRM

53-00-01, Figure 201, Repair 30.

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ALERT ALERT
NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 14:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 16.

(a) If any crack is found in a lap joint do the repair in accordance with 737-400 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 15:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 17.

(a) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

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ALERT ALERT
Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 16:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 18.

(a) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

Group 17:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 19.

(a) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

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ALERT ALERT
Group 18:

(1) Do inspections for cracks in the crown lap joints and stringer clips in accordance with

FIGURE 1 at the locations given in FIGURE 20.

(a) If any crack is found in a lap joint do the repair in accordance with 737-500 SRM

53-00-01, Figure 201, Repair 30.

NOTE: 1. Tear strap fastener locations only:

As an option to confirm crack indications do an open hole

inspection in accordance with 737 NDT Part 6, 51-00-00, Figure

16.

2. Mid-bay fastener locations (between tear straps):

Boeing does not have a published method to confirm/clear cracks

at these locations.

(b) Replace any damaged stringer clips with the same part number.

(2) Continue inspections in accordance with Paragraph 1.E., Compliance.

c. Refer to the table below and install all panels and equipment removed for access:

737-300/-400/-500

AMM Subject

737-200 AMM

Subject

Equipment

737-300/400/500

AMM 25-21-45

737-100/200 AMM

25-21-341

Ceiling Panels

737-300/400/500

AMM 25-24-31

737-100/200 AMM

25-24-311

Overhead Stowage Bins

737-300/400/500

AMM 25-21-46

737-100/200 AMM

25-21-311

Sidewall Linings

737-300/400/500

AMM 25-21-39

737-100/200 AMM

25-21-347

Sidewall Insulation

737-300/400/500

AMM 25-22-00

737-100/200 AMM

25-22-0

Passenger Seats

737-300/400/500

AMM 25-23-61

737-100/200 AMM

25-23-311

Passenger Service Units

d. Put the airplane back to a serviceable condition.

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

FIGURE 1: INTERNAL INSPECTION - CROWN LAP JOINTS AND STRINGER CLIPS

(SHEET 1 OF 2)

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ALERT ALERT
IDENTIFICA- QTY MORE DATA

TION

STEP TASK NAME

Crown Lap - - (a) (b)

Joints Lower

Skin

1 Inspect

Stringer Clips - - Detailed inspection.

(a) Do an internal Medium 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. 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. Do a detailed inspection of the lap joint lower fastener

row for cracking.

(b) As an option to confirm crack indications at tear strap fastener locations only do an open hole inspection

in accordance with 737 NDT Part 6, 51-00-00, Figure 16.

FIGURE 1: INTERNAL INSPECTION - CROWN LAP JOINTS AND STRINGER CLIPS

(SHEET 2 OF 2)

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

STEP TASK NAME IDENTIFICATION QTY NOTES

Crown Lap - - (a) (b) (c)

Joints Lower Skin

1 Inspect

(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.

(b) As an option to confirm crack indications between tear straps do an internal Medium 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 and do a detailed inspection of the lap joint

lower fastener row for cracking.

FIGURE 2: EXTERNAL INSPECTION - CROWN LAP JOINTS

(SHEET 1 OF 2)

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ALERT ALERT
STEP TASK NAME IDENTIFICATION QTY NOTES

(c) As an option to confirm crack indications at tear strap fastener locations only do an open hole inspection in accordance with 737 NDT Part 6, 51-00-00, Figure 16.

FIGURE 2: EXTERNAL INSPECTION - CROWN LAP JOINTS

(SHEET 2 OF 2)

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ALERT ALERT
This Figure applies only to: Group 1.

FIGURE 3: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 727 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 727 to STA 908

FIGURE 3: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

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ALERT ALERT
This Figure applies only to: Group 2.

FIGURE 4: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

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75 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 827 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 4: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

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ALERT ALERT
This Figure applies only to: Group 3.

FIGURE 5: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

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77 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 727 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 520 to STA 908

5 Inspect Lap Joint S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 727 to STA 908

FIGURE 5: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

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ALERT ALERT
This Figure applies only to: Group 4.

FIGURE 6: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

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79 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 827 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 520 to STA 908

5 Inspect Lap Joint S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 827 to STA 908

FIGURE 6: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

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ALERT ALERT
This Figure applies only to: Group 5.

FIGURE 7: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

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BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 827 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 7: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

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ALERT ALERT
This Figure applies only to: Group 6.

FIGURE 8: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

83 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 827 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 540

S-4R, STA 727E to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 540

S-4L, STA 727E to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 8: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

84 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 7.

FIGURE 9: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

85 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 847 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 9: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

86 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 8.

FIGURE 10: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

87 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 847 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 540

S-4R, STA 727E to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 540

S-4L, STA 727E to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 10: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

88 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 9.

FIGURE 11: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

89 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 11: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

90 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 10.

FIGURE 12: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

91 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 540

S-4R, STA 727E to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 540

S-4L, STA 727E to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 12: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

92 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 11.

FIGURE 13: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

93 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 13: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

94 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 12.

FIGURE 14: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

95 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 847 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 14: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

96 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 13.

FIGURE 15: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

97 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 15: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

98 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 14.

FIGURE 16: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

99 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 16: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

100 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 15.

FIGURE 17: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

101 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 847 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 17: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

102 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 16.

FIGURE 18: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

103 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

S-14R, STA 847 to STA 908

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 540

S-4R, STA 727C to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 540

S-4L, STA 727C to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

S-14L, STA 827 to STA 908

FIGURE 18: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

104 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 17.

FIGURE 19: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

105 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-10R, STA 360 to STA 540

S-10R, STA 727 to STA 908

3 Inspect Lap Joint S-4R, STA 360 to STA 908

4 Inspect Lap Joint S-4L, STA 360 to STA 908

5 Inspect Lap Joint S-10L, STA 360 to STA 540

S-10L, STA 727 to STA 908

6 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 19: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

106 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT
This Figure applies only to: Group 18.

FIGURE 20: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 1 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

107 of 108

BOEING SERVICE BULLETIN 737-53A1255

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

STEP TASK NAME IDENTIFICATION MORE DATA

1 Inspect Lap Joint S-14R, STA 360 to STA 540

2 Inspect Lap Joint S-14L, STA 360 to STA 540

FIGURE 20: INSPECTION ZONES AT THE CROWN LAP JOINT AREA

(SHEET 2 OF 2)

Export Controlled ECCN: 9E991 - BOEING

PROPRIETARY - Copyright © Unpublished

Work - See page 1 for details.

Original Issue: October 17, 2002

Revision 2 August 07, 2012 737-53A1255

108 of 108

BOEING SERVICE BULLETIN 737-53A1255

ALERT ALERT