### 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. 9E991 ECCN: 

## 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 Unpublished Work.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, BBJ, DC-8, DC-9, DC-10, KC-10, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8A, Poseidon and Boeing liveries are all trademarks owned by The Boeing Company; and no trademark license is granted in connection with this document unless provided in writing by Boeing. BOEING is a trademark of Boeing Management Company.

Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 1 of 108 2.0Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 2 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**

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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 3 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 4 of 108 **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** October 17, 2002 Original Issue: November 07, 2011 Revision 1: August 07, 2012 Revision 2:

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 5 of 108Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 6 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**

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### 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 7 of 108Boeing 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.
**Reference Affected**  **Planning Data** Paragraph 1.A.2., Spares Affected No Spares Affected Paragraph 1.E., Compliance and Paragraph 1.F., Approval Yes AD Related Paragraph 1.H., Weight and Balance Changes No Weight and Balance Change Paragraph 1.I., Electrical Load Data No Electrical Load Changed

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 8 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Reference**  **Affected Planning Data**  Paragraph 1.K., Publications Affected No Publications Affected Paragraph 1.K., Publications Affected No Airplane Flight Operations Affected (Flight CrewOperations Manual and/or FAA Approved Airplane Flight Manual) Paragraph 2.C.1., Kits/Parts No Kits/Parts Required Paragraph 2.C.2., Parts and Materials Supplied by the Operator Yes Operator Supplied Material Paragraph 2.F., Special Tooling Necessary to do this Service Bulletin No Special Tooling Required

**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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 9 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT MANPOWER**  Refer to Paragraph 1.G. Manpower. **MATERIAL INFORMATION** None.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 10 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 11 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 12 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**

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### 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.
**DESCRIPTION CONFIGURATION**  **GROUP** 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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 13 of 108**DESCRIPTION CONFIGURATION**  **GROUP** 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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 14 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT DESCRIPTION**  **CONFIGURATION GROUP**  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 **Group Variable Number**  1 PG584 - PG586 1 PH001 1 PH011 - PH013 1 PH021 - PH024 1 PH743 1 PJ003 - PJ009 1 PJ105 - PJ119 1 PJ201 - PJ219 12 PJ301 - PJ302 13 PJ551 14 PJ552 1 PK026 - PK029 1 PK041 - PK053 1 PK061 - PK070 1 PK081 - PK082 1 PK091 - PK099

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 15 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 1 PK101 - PK103 1 PK111 - PK120 1 PK141 - PK146 1 PK201 - PK204 1 PK211 - PK215 2 PK216 - PK220 1 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 2 PK515 2 PK519 1 PK521 - PK525 2 PK526 - PK528 1 PK541 - PK564 2 PK565 1 PK581 1 PK591 - PK599 1 PK601 - PK617 1 PK621 - PK637 1 PK641 - PK642

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 16 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 1 PK661 - PK664 2 PK665 - PK666 1 PK671 - PK680 2 PK681 1 PK691 - PK697 1 PK711 - PK716 1 PK731 - PK749 2 PK750 - PK765 1 PK771 - PK779 1 PK801 - PK802 2 PK803 - PK804 1 PK819 - PK826 2 PK827 1 PK830 1 PK861 - PK863 1 PK871 - PK874 1 PK881 - PK884 1 PK901 - PK932 2 PK933 - PK938 1 PK971 - PK974 1 PL001 - PL026 2 PL027 - PL028 1 PL061 1 PL081 1 PL101 - PL113 1 PL151 1 PL171 - PL172 1 PL201 - PL203 1 PL221 1 PL401 - PL415 2 PL416 - PL417 1 PL421 1 PL441

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 17 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 1 PL451 - PL454 2 PL455 - PL456 1 PL471 1 PL491 1 PL501 - PL506 1 PL551 - PL562 1 PL581 1 PL601 2 PL602 - PL603 1 PL611 2 PL621 - PL626 1 PL631 - PL632 1 PL717 - PL745 2 PL746 - PL747 1 PL756 1 PL758 1 PL761 - PL770 1 PL781 - PL787 2 PL788 1 PL793 1 PM001 - PM006 2 PM016 - PM017 1 PM021 - PM023 1 PM051 - PM056 2 PM057 - PM066 1 PM101 - PM110 2 PM111 - PM119 1 PM141 - PM142 2 PM171 2 PM181 2 PM251 - PM255 2 PM281 - PM283 5 PM381 - PM395

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 18 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 7 PM396 - PM399 7 PM401 - PM417 7 PM541 9 PM542 11 PM543 - PM547 12 PM551 - PM564 1 PN001 - PN002 1 PN021 2 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 5 PP001 - PP054 5 PP101 - PP126 6 PP127 - PP150 8 PP151 - PP160 5 PP161 - PP169 5 PP181 - PP199 5 PP201 - PP205 5 PP221 5 PP231 - PP243 5 PP281 - PP286 5 PP301 - PP305 5 PP351 - PP353

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 19 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 5 PP376 - PP384 5 PP391 - PP393 5 PP401 - PP440 5 PP471 - PP475 5 PP501 - PP510 7 PP511 - PP517 5 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 7 PP874 - PP875 5 PP891 - PP899 5 PP901 - PP925 7 PP926 - PP930 5 PP931 - PP936 5 PP946 - PP948 5 PP951 - PP952 5 PP961 - PP967 5 PP981 - PP988 7 PP989 - PP990 5 PP991 5 PP993 5 PQ001 - PQ016 5 PQ026 - PQ041 5 PQ051 - PQ073 7 PQ074 - PQ085

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 20 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 5 PQ086 - PQ092 5 PQ101 - PQ199 5 PQ201 - PQ202 5 PQ221 - PQ229 7 PQ230 5 PQ231 - PQ236 7 PQ237 5 PQ241 - PQ243 5 PQ251 - PQ257 7 PQ258 - PQ267 5 PQ281 - PQ287 7 PQ288 - PQ296 5 PQ301 - PQ305 7 PQ306 - PQ307 5 PQ331 - PQ332 7 PQ341 - PQ344 7 PQ361 - PQ369 7 PQ401 - PQ406 9 PQ407 11 PQ408 7 PQ411 - PQ413 7 PQ421 9 PQ471 - PQ472 11 PQ473 9 PQ479 - PQ480 7 PQ481 7 PQ486 9 PQ487 7 PQ491 - PQ493 7 PQ771 7 PQ791 - PQ793 7 PQ801 - PQ803 9 PQ804 - PQ805

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 21 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 9 PQ931 - PQ932 7 PS601 - PS616 7 PS631 7 PS636 - PS638 5 PS641 - PS642 7 PS643 - PS644 7 PS651 - PS657 5 PS666 - PS668 7 PS669 7 PS691 - PS692 7 PS701 - PS703 8 PS751 - PS756 10 PS757 - PS762 15 PT001 - PT011 15 PT021 - PT027 17 PT028 15 PT041 - PT059 17 PT060 - PT063 18 PT064 15 PT101 - PT105 15 PT121 - PT125 15 PT146 - PT148 15 PT161 - PT170 15 PT181 - PT187 15 PT211 - PT220 15 PT295 15 PT301 - PT303 17 PT304 - PT306 15 PT331 - PT360 15 PT381 - PT399 15 PT401 - PT435 17 PT436 - PT438 15 PT501 - PT512

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 22 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 15 PT561 - PT565 15 PT581 - PT584 15 PT611 - PT621 15 PT641 - PT642 15 PT651 - PT655 15 PT671 - PT672 15 PT701 - PT703 16 PU001 - PU025 12 PV001 - PV055 12 PV201 - PV202 13 PV203 12 PV231 - PV237 12 PV271 - PV272 12 PV281 - PV282 13 PV283 12 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 13 PW224 - PW230 12 PW231 - PW240 13 PW241 - PW244 14 PW245 12 PW261 12 PW265 - PW268 13 PW278 12 PW281

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 23 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 14 PW282 - PW284 12 PW293 12 PW296 12 PW301 - PW323 13 PW324 - PW327 13 PW461 - PW467 12 PW501 - PW504 12 PW511 - PW520 12 PW526 12 PW531 - PW545 13 PW546 12 PW556 13 PW557 12 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 3 PY022 3 PY036 - PY037 3 PY046 - PY048 3 PY051 - PY053 3 PY056 - PY057 3 PY101 - PY103 3 PY111 - PY113 3 PY131 - PY135

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 24 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group**  **Variable Number** 3 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 4 PY409 - PY410 3 PY411 3 PY421 - PY422 3 PY441 3 PY451 3 PY461 - PY462 4 PY463 4 PY591 - PY595 3 PY611 - PY612 3 PY621 3 PY631 3 PY651 3 PY671 - PY672 3 PY721 3 PY741 2. Spares Affected None.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 25 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 26 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 27 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 1-2:** 
**Affected Maintenance Zones Zone**  **Model** 1-7, 1-8 737-200 **Group 3-4:**
**Affected Maintenance Zones Zone**  **Model** 1-7, 1-8 737-200C **Group 5-11:**
**Affected Maintenance Zones Zone**  **Model** 107, 108 737-300 **Group 12-14:**
**Affected Maintenance Zones Zone**  **Model** 107, 108 737-400 **Group 15-18:**
**Affected Maintenance Zones Zone**  **Model** 107, 108 737-500 **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.**
S-4L/R between STA 540 and STA 727 Over wing

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 28 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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) Compliance Time (a)**  **Action (d) Condition** 

- 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 than35,000 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 totalflight cycles, not to exceed 2,500 flight cyclesafter the external inspection, but not before37,500 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 forcracks in accordance with Accomplishment Instructions 3.B.2.

2,500 flight cycles. Within 2,500 flight cy- 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 totalflight cycles, not to exceed 1,700 flight cyclesafter 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 forcracks in accordance with Accomplishment Instructions 3.B.2.

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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 29 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Table 1: Inspection for cracking at crown lap joints.**  **Repeat Interval (Not to Exceed) (a)**  **Compliance Time (a) Action (d)**  **Condition**

OPTION 1: Airplanes with more than 34,999 and less than37,500 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 totalflight 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 forcracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- 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 totalflight cycles, not to exceed 1,700 flight cyclesafter 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 forcracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- 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 before40,000 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 forcracks in accordance with Accomplishment Instructions 3.B.2.

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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 30 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Table 1: Inspection for cracking at crown lap joints.**  **Repeat Interval (Not to Exceed) (a)**  **Compliance Time (a) Action (d)**  **Condition**

- - Do one of the options that follow: Airplanes with more than 37,499 and less than40,000 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 servicebulletin 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 forcracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- 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 servicebulletin 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 forcracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 31 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Table 1: Inspection for cracking at crown lap joints.**  **Repeat Interval (Not to Exceed) (a)**  **Compliance Time (a) Action (d)**  **Condition**

- - Do one of the options that follow: Airplanes with more than 39,999 and less than43,300 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 forcracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- 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 forcracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- 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 thestringer clips for cracks in accordance with Accomplishment Instructions 3.B.2. Airplanes with more than 43,299 and less than45,000 total flight cycles at the Revision 1 date of this service bulletin. - Within 1,700 total flightcycles 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 stringerclips for cracks in accordance with Accomplishment Instructions 3.B.2. 2,500 flight cycles. Within 2,500 flight cy- cles after the internal inspection of the non over wing crown lap joints, but not to exceed48,750 total flight cycles. Do an external Eddy Current inspection of the crown lap joints for cracks in accordance with Accomplishment Instructions 3.B.1.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 32 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Table 1: Inspection for cracking at crown lap joints.**  **Repeat Interval (Not to Exceed) (a)**  **Compliance Time (a) Action (d)**  **Condition** 2,500 flight cycles Within 2,500 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 44,999 and less than46,251 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 than47,501 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 than48,751 total flight cycles at the Revision 1 date of this service bulletin.

- Before further flight. Repair the lap joint in accordance with Accom-plishment Instructions 3.B.1 or 3.B.2.b as applicable. Any crack found in a lap joint.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 33 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Table 1: Inspection for cracking at crown lap joints.**  **Repeat Interval (Not to Exceed) (a)**  **Compliance Time (a) Action (d)**  **Condition**

- Before further flight. Replace the damaged stringer clip in accor- dance with Accomplishment Instructions 3.B.2.b. Any stringerclip 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 34 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 35 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  28.75 115.00 4 Open Access 4.75 19.00 4 Figure 3 28.75 115.00 4 Close Access 62.25 249.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 1: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.00 8.00 2 Figure 3 4.00 8.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 2: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  26.00 104.00 4 Open Access 4.25 17.00 4 Figure 4 26.00 104.00 4 Close Access

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 36 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 2:**  **Internal Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** 56.25 225.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 2: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.00 8.00 2 Figure 4 4.00 8.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 3: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  24.75 99.00 4 Open Access 3.75 15.00 4 Figure 5 24.75 99.00 4 Close Access 53.25 213.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 3: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  3.50 7.00 2 Figure 5 3.50 7.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 4: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  21.00 84.00 4 Open Access 3.25 13.00 4 Figure 6 21.00 84.00 4 Close Access 45.25 181.00 TOTAL FOR EACH AIRPLANE (a)

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 37 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 4:**  **Internal Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** (a) Additional hours will be required for repair if any crack is found. **Group 4: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  3.25 6.50 2 Figure 6 3.25 6.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 5: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  28.75 115.00 4 Open Access 5.00 20.00 4 Figure 7 28.75 115.00 4 Close Access 62.50 250.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 5: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.25 8.50 2 Figure 7 4.25 8.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 6: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  25.25 101.00 4 Open Access 4.25 17.00 4 Figure 8 25.25 101.00 4 Close Access 54.75 219.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 38 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 6:**  **External Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** 3.75 7.50 2 Figure 8 3.75 7.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 7: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  30.25 121.00 4 Open Access 5.00 20.00 4 Figure 9 30.25 121.00 4 Close Access 65.50 262.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 7: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.25 8.50 2 Figure 9 4.25 8.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 8: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  25.25 101.00 4 Open Access 4.25 17.00 4 Figure 10 25.25 101.00 4 Close Access 54.75 219.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 8: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  3.75 7.50 2 Figure 10

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 39 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 8:**  **External Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** 3.75 7.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 9: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  28.75 115.00 4 Open Access 4.75 19.00 4 Figure 11 28.75 115.00 4 Close Access 62.25 249.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 9: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.00 8.00 2 Figure 11 4.00 8.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 10: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  25.00 100.00 4 Open Access 4.00 16.00 4 Figure 12 25.00 100.00 4 Close Access 54.00 216.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 10: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  3.50 7.00 2 Figure 12 3.50 7.00 TOTAL FOR EACH AIRPLANE (a)

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 40 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 10:**  **External Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** (a) Additional hours will be required for repair if any crack is found. **Group 11: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  6.75 27.00 4 Open Access 4.00 4.00 1 Figure 13 6.75 27.00 4 Close Access 17.50 58.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 11: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  2.50 2.50 1 Figure 13 2.50 2.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 12: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  35.00 140.00 4 Open Access 5.75 23.00 4 Figure 14 35.00 140.00 4 Close Access 75.75 303.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 12: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.75 9.50 2 Figure 14 4.75 9.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 41 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 13:**  **Internal Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** 33.75 135.00 4 Open Access 5.50 22.00 4 Figure 15 33.75 135.00 4 Close Access 73.00 292.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 13: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.50 9.00 2 Figure 15 4.50 9.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 14: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  6.75 27.00 4 Open Access 4.00 4.00 1 Figure 16 6.75 27.00 4 Close Access 17.50 58.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 14: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  2.50 2.50 1 Figure 16 2.50 2.50 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 15: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  28.75 115.00 4 Open Access

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 42 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 15:**  **Internal Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** 5.00 20.00 4 Figure 17 28.75 115.00 4 Close Access 62.50 250.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 15: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  4.00 8.00 2 Figure 17 4.00 8.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 16: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  24.75 99.00 4 Open Access 3.75 15.00 4 Figure 18 24.75 99.00 4 Close Access 53.25 213.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 16: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  3.50 7.00 2 Figure 18 3.50 7.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 17: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  26.00 104.00 4 Open Access 4.50 18.00 4 Figure 19

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 43 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT Group 17:**  **Internal Inspection Elapsed Hours**  **Task-Hours Number of Persons**  **Task** 26.00 104.00 4 Close Access 56.50 226.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 17: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  3.50 7.00 2 Figure 19 3.50 7.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 18: Internal Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  6.75 27.00 4 Open Access 4.00 4.00 1 Figure 20 6.75 27.00 4 Close Access 17.50 58.00 TOTAL FOR EACH AIRPLANE (a) (a) Additional hours will be required for repair if any crack is found. **Group 18: External Inspection**  **Elapsed Hours Task-Hours**  **Number of Persons Task**  2.50 2.50 1 Figure 20 2.50 2.50 TOTAL FOR EACH AIRPLANE (a) (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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 44 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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:
**Title Drawing Number**  Top Kit - Skin Lap Repair, S-4, STA 360 - 908 65C38450 Top Kit - Skin Lap Repair, S-10, STA 360 - 540, 727 - 908 65C38451 Top Kit - Skin Lap Repair, S-14, STA 360 - 540 65C38452 Skin Diagram - Body-Model 737 65-73742 Top Kit - Stringer Tie Clip 65C37852 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 45 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 46 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 47 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 48 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 49 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 50 of 108 **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 737-100/200 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 51 of 108 **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 737-100/200 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 52 of 108 **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 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 53 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 54 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 55 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 56 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 57 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 58 of 108 **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

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 59 of 108 **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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 60 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 61 of 108 **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:

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 62 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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):

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 63 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 64 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 65 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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):

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 66 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 67 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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.

Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2: August 07, 2012 68 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.

**FIGURE 1: INTERNAL INSPECTION - CROWN LAP JOINTS AND STRINGER CLIPS (SHEET 1 OF 2)** 
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 69 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICA-**  **TION NAME**  **TASK STEP**  (a) (b)

- - Crown Lap Joints Lower Skin Inspect 1

Detailed inspection.

- - Stringer Clips (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)** 
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 70 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.
**NOTES QTY**  **IDENTIFICATION NAME**  **TASK STEP**  (a) (b) (c)

- - Crown LapJoints Lower Skin Inspect 1

(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)** 
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 71 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT NOTES**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP**(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)** 
Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 72 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT This Figure applies only to: Group 1.** 

**FIGURE 3: 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 737-53A1255 Revision 2 August 07, 2012 73 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 727 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 S-14L, STA 727 to STA 908

**FIGURE 3: 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 737-53A1255 Revision 2 August 07, 2012 74 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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 PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 827 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 S-14L, STA 827 to STA 908

**FIGURE 4: 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 737-53A1255 Revision 2 August 07, 2012 76 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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 Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 727 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 520 to STA 908 Lap Joint Inspect 4 S-10L, STA 727 to STA 908 Lap Joint Inspect 5 S-14L, STA 727 to STA 908 Lap Joint Inspect 6

**FIGURE 5: 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 737-53A1255 Revision 2 August 07, 2012 78 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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 PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 827 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 520 to STA 908 Lap Joint Inspect 4 S-10L, STA 727 to STA 908 Lap Joint Inspect 5 S-14L, STA 827 to STA 908 Lap Joint Inspect 6

**FIGURE 6: 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 737-53A1255 Revision 2 August 07, 2012 80 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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 PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: October 17, 2002 737-53A1255 Revision 2 August 07, 2012 81 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 827 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 S-14L, STA 827 to STA 908

**FIGURE 7: 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 737-53A1255 Revision 2 August 07, 2012 82 of 108 **BOEING SERVICE BULLETIN 737-53A1255 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 827 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 540 Lap Joint Inspect 3 S-4R, STA 727E to STA 908 S-4L, STA 360 to STA 540 Lap Joint Inspect 4 S-4L, STA 727E to STA 908 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 847 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 847 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 540 Lap Joint Inspect 3 S-4R, STA 727E to STA 908 S-4L, STA 360 to STA 540 Lap Joint Inspect 4 S-4L, STA 727E to STA 908 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6

**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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 540 Lap Joint Inspect 3 S-4R, STA 727E to STA 908 S-4L, STA 360 to STA 540 Lap Joint Inspect 4 S-4L, STA 727E to STA 908 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6

**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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14L, STA 360 to STA 540 Lap Joint Inspect 2

**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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 847 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6

**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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14L, STA 360 to STA 540 Lap Joint Inspect 2

**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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 847 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14R, STA 847 to STA 908 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 540 Lap Joint Inspect 3 S-4R, STA 727C to STA 908 S-4L, STA 360 to STA 540 Lap Joint Inspect 4 S-4L, STA 727C to STA 908 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6 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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-10R, STA 360 to STA 540 Lap Joint Inspect 2 S-10R, STA 727 to STA 908 S-4R, STA 360 to STA 908 Lap Joint Inspect 3 S-4L, STA 360 to STA 908 Lap Joint Inspect 4 S-10L, STA 360 to STA 540 Lap Joint Inspect 5 S-10L, STA 727 to STA 908 S-14L, STA 360 to STA 540 Lap Joint Inspect 6

**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 737-53A1255 Revision 2 August 07, 2012 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 737-53A1255 Revision 2 August 07, 2012 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.
**MORE DATA IDENTIFICATION**  **NAME TASK**  **STEP** S-14R, STA 360 to STA 540 Lap Joint Inspect 1 S-14L, STA 360 to STA 540 Lap Joint Inspect 2

**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 737-53A1255 Revision 2 August 07, 2012 108 of 108 **BOEING SERVICE BULLETIN 737-53A1255 ALERT**  **ALERT**