### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Number: 737-57A1308**  Original Issue: August 21, 2009 Revision 1: October 01, 2009 ATA System: 5720 **SUBJECT:** WINGS - Outer Wing - Skins - Lower Wing Skin at Fuel Tank Access Door Cutout Keyway - Inspection and Change Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15 CFR 730-774). An export license may be required before it is used for development, production or use by foreign persons from specific countries. The controller of this data has the individual responsibility to abide by all export laws. 9E991 ECCN: 

## BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2009 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter. Boeing also claims copyright in this document as a compilation and/or collective work. This document includes proprietary information owned by The Boeing Company and/or one or more third parties. Treatment of the document and the information it contains is governed by contract with Boeing. For more information, contact The Boeing Company, P.O. Box 3707, Seattle, Washington 98124. Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner, 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 the Boeing livery 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BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 1 of 44 3.0BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 2 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**

BLANK PAGE**Table of Contents** Revision Transmittal Sheet ............................................ 5 Summary...................................................... 7 1. PLANNING INFORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 E. Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 H. Weight and Balance Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1. Existing Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2. Data supplied with this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3. Installation Drawings Used in the Preparation of this Service Bulletin. . . . . . . . . . . . 16 K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 A. Material - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 C. Parts Necessary For Each Airplane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2. Parts and Materials Supplied by the Operator. . . . . . . . . . . . . . . . . . . . . . . . 17 3. Parts Modified and Reidentified. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 D. Parts Necessary to Change Spares. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 E. Special Tooling - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 F. Special Tooling Necessary to do this Service Bulletin. . . . . . . . . . . . . . . . . . . . . . . 18 3. ACCOMPLISHMENT INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 B. WORK INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 FIGURE 1: LEFT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY. . . . . . . . . 21 FIGURE 2: RIGHT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY. . . . . . . . 24 FIGURE 3: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION. . . . . . . . . 27 FIGURE 4: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION . . . . . . . . 30 FIGURE 5: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE . . . 33 FIGURE 6: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE . . 36 FIGURE 7: LEFT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR. . . . . . . . . 39 FIGURE 8: RIGHT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR. . . . . . . . 42

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 3 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 4 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**

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### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Revision Transmittal Sheet**  **Number: 737-57A1308** Original Issue: August 21, 2009 Revision 1: October 01, 2009 ATA System: 5720 **SUBJECT:** WINGS - Outer Wing - Skins - Lower Wing Skin at Fuel Tank Access Door Cutout Keyway - Inspection and Change This revision includes all pages of the service bulletin. **COMPLIANCE INFORMATION RELATED TO THIS REVISION** No more work is necessary on airplanes changed in accordance with the original issue of this service bulletin. Airplane variable numbers YH301, YH302 and YH303 are added to the effectivity of this service bulletin. **REASON FOR REVISION** This revision is sent to complete the approval process. The original issue was inadvertently released without completion of the full approval process. These sections are changed: 1. In the Compliance table, the words "after the initial release date" are changed to "after the revision 1 date", in two places. 2. Airplane variable numbers YH301, YH302 and YH303 are added to the effectivity of this service bulletin. The data given in Information Notice 737-57-1308 IN 01 is included in this revision. 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** August 21, 2009 Original Issue: October 01, 2009 Revision 1:

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 5 of 44BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 6 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**

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### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Summary**  **Number: 737-57A1308** Original Issue: August 21, 2009 Revision 1: October 01, 2009 ATA System: 5720 **SUBJECT:** WINGS - Outer Wing - Skins - Lower Wing Skin at Fuel Tank Access Door Cutout Keyway - Inspection and Change 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** The inspection and change in this service bulletin will detect and help prevent cracks in the lower wing skins. Cracks in the lower wing skin, if left undetected could result in the catastrophic structural failure of the wings. Three operators have reported finding seven cracks, ranging from 0.02 to 0.380 inches in length, emanating from the keyway of the fuel tank access hole on the wing lower skin between wing rib numbers 8 and 9 on Boeing 777-200LR and 777-300ER airplanes. The fuel tank access door at this location has a fuel measuring stick installed and the keyway is used to ensure that the fuel measuring stick is oriented correctly when the fuel tank access door is installed. The crack is believed to be the result of fatigue due to the position of the keyway. The lower wing skins on the Boeing 737-900ER Series Airplanes have fuel tank access holes with the same configuration as that of the affected fuel tank access holes on the 777-300ER airplanes. The affected fuel tank access holes on the 737-900ER are located between ribs 4 and 5, between Wing Station (WSTA) 180 and WSTA 204.25. These fuel tank access holes are for fuel tank access doors 531BB and 631BB. Although cracks have not yet been reported on any 737-900ER airplane, damage tolerance analysis shows crack potential for the 737-900ER lower wing skins at the noted locations. If a crack initiates, and grows unchecked, it could result in the loss of the lower wing skin load path. The loss of the lower wing skin load path could result in the catastrophic structural failure of the wing. Inspection of the keyway will detect cracks in the keyway before the cracks can grow to the point the lower wing skin load path is lost. Changing the profile of the keyway will improve the fatigue characteristics of the keyway which will help prevent cracks in the future. The change in the profile of the keyway can also be used to repair cracks up to 0.030 inch in length. If any crack is found that is greater than 0.30 inch in length, skin panel replacement may be required. Skin panel replacement would require significant manpower and extended downtime.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 7 of 44The change given in this Service Bulletin is incorporated in production on 737-900ER series airplanes from line number 2990 onwards. Boeing Service Related Problem (SRP) 777-SRP-57-0222 is related to this service bulletin. **ACTION** Drain and purge the center fuel tank. Remove the fuel tank access doors 531BB and 631BB between wing rib numbers 4 and 5, between WSTA 180 and WSTA 204.25. Inspect the fuel tank access door cutouts for a keyway. If a keyway does not exist then no more work is necessary. If a keyway does exist then do a one time High Frequency Eddy Current (HFEC) inspection of the keyway in the fuel tank access door cutout for cracks. If no crack is found or any crack found is 0.030 inch in length or less, change the profile of the keyway to obtain a larger radius and remove the crack, if present. If any crack greater than 0.030 inch is found, contact Boeing for repair instructions and do the repair. Install the fuel tank access doors 531BB and 631BB. **EFFECTIVITY** 737-900ER Airplanes. Refer to Paragraph 1.A., Effectivity for the list of affected airplanes. **COMPLIANCE** The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin mandatory. See Paragraph 1.E., Compliance for compliance information. **INDUSTRY SUPPORT INFORMATION** Boeing warranty remedies are available for airplanes in warranty as of May 1, 2008. Please refer to Paragraph 2.B., Industry Support Information. **MANPOWER** Refer to Paragraph 1.G., Manpower. **MATERIAL INFORMATION** Operator Supplied Parts/Materials. Refer to Paragraph 2.A., Material - Price and Availability.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 8 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 9 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 10 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**

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### Commercial **Airplanes** 

# 737 Service Bulletin **ALERT Number: 737-57A1308**  Original Issue: August 21, 2009 Revision 1: October 01, 2009 ATA System: 5720 **SUBJECT:** WINGS - Outer Wing - Skins - Lower Wing Skin at Fuel Tank Access Door Cutout Keyway - Inspection and Change THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH 1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO THE NEW OWNER. **1. PLANNING INFORMATION A. Effectivity**  1. Airplanes This service bulletin is for the airplanes shown below. Refer to Service Bulletin Index Document D6-19567 Part 3 for Airplane Variable Number, Line Number, and Serial Number data.
**DESCRIPTION CONFIGURATION**  **GROUP** 737-900ER Series Airplanes with a keyway in the wing lower skin at fuel tank access doors 531BB and 631BB. - 1

Airplane Models: 737-900ER **Group Variable Number**  1 YH001 - YH012 1 YH031 - YH039 1 YH051 - YH055 1 YH101 - YH126 1 YH201 - YH202

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 11 of 44**Group Variable Number**  1 YH206 - YH207 1 YH301 - YH303 1 YH321 - YH322 2. Spares Affected None. **B. Concurrent Requirements** None. **C. Reason** The inspection and change in this service bulletin will detect and help prevent cracks in the lower wing skins. Cracks in the lower wing skin, if left undetected could result in the catastrophic structural failure of the wings. Three operators have reported finding seven cracks, ranging from 0.02 to 0.380 inches in length, emanating from the keyway of the fuel tank access hole on the wing lower skin between wing rib numbers 8 and 9 on Boeing 777-200LR and 777-300ER airplanes. The fuel tank access door at this location has a fuel measuring stick installed and the keyway is used to ensure that the fuel measuring stick is oriented correctly when the fuel tank access door is installed. The crack is believed to be the result of fatigue due to the position of the keyway. The lower wing skins on the Boeing 737-900ER Series Airplanes have fuel tank access holes with the same configuration as that of the affected fuel tank access holes on the 777-300ER airplanes. The affected fuel tank access holes on the 737-900ER are located between ribs 4 and 5, between Wing Station (WSTA) 180 and WSTA 204.25. These fuel tank access holes are for fuel tank access doors 531BB and 631BB. Although cracks have not yet been reported on any 737-900ER airplane, damage tolerance analysis shows crack potential for the 737-900ER lower wing skins at the noted locations. If a crack initiates, and grows unchecked, it could result in the loss of the lower wing skin load path. The loss of the lower wing skin load path could result in the catastrophic structural failure of the wing. Inspection of the keyway will detect cracks in the keyway before the cracks can grow to the point the lower wing skin load path is lost. Changing the profile of the keyway will improve the fatigue characteristics of the keyway which will help prevent cracks in the future. The change in the profile of the keyway can also be used to repair cracks up to 0.030 inch in length. If any crack is found that is greater than 0.30 inch in length, skin panel replacement may be required. Skin panel replacement would require significant manpower and extended downtime. The change given in this Service Bulletin is incorporated in production on 737-900ER series airplanes from line number 2990 onwards. Boeing Service Related Problem (SRP) 777-SRP-57-0222 is related to this service bulletin. Revision 1 is sent to complete the approval process. The original issue was inadvertently released without completion of the full approval process.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 12 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**These sections are changed in Revision 1: 1. In the Compliance table, the words "after the initial release date" are changed to "after the revision 1 date", in two places. 2. Airplane variable numbers YH301, YH302 and YH303 are added to the effectivity of this service bulletin. **D. Description** Drain and purge the center fuel tank. Remove the fuel tank access doors 531BB and 631BB between wing rib numbers 4 and 5, between WSTA 180 and WSTA 204.25. Inspect the fuel tank access door cutouts for a keyway. If a keyway does not exist then no more work is necessary. If a keyway does exist then do a one time High Frequency Eddy Current (HFEC) inspection of the keyway in the fuel tank access door cutout for cracks. If no crack is found or any crack found is 0.030 inch in length or less, change the profile of the keyway to obtain a larger radius and remove the crack, if present. If any crack greater than 0.030 inch is found, contact Boeing for repair instructions and do the repair. Install the fuel tank access doors 531BB and 631BB. Revision 1 - No more work is necessary on airplanes changed in accordance with the original issue of this service bulletin. The work in this service bulletin is done in the maintenance zone(s) given below.
**Affected Maintenance Zones Zone**  **Model** 531, 631 737-900ER **E. Compliance** The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in Table 1 in this service bulletin mandatory. **Table 1: Compliance Time For Fuel Access Door Cutout Keyway Inspection and Keyway Profile Change Repeat Interval**  **(Not to Exceed) Compliance Time**  **Action Condition** 

- Before 7,500 total flight cycles or 1000 flight cycles after the revision 1 date of this service bulletin, whichever occurs later. Do a one time inspection for a keyway in the fuel tank access door 531BB and 631BB cutouts in accordance with Paragraph 3.B.1.d. All Airplanes

- - No more work is necessary. Airplanes that do not have a keyway in the fuel tank access door 531BB and 631BB cutouts.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 13 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT Table 1: Compliance Time For Fuel Access Door Cutout Keyway Inspection and Keyway Profile Change**  **Repeat Interval (Not to Exceed)**  **Compliance Time Action**  **Condition**

- Before 7,500 total flight cycles or 1000 flight cycles after the revision 1 date of this service bulletin, whichever occurs later. Do a one time High Frequency Eddy Current (HFEC) inspection of the fuel tank accessdoor 531BB cutout keyway and fuel tank access door 631BB cutout keyway on the left and right wing in accordance with Paragraph 3.B.2. Part 2 - Fuel Tank Access Door Cutout Keyway Inspection.Airplanes that have a keyway in the fuel tank access door 531BB and/or 631BB cutout.

- Before further flight. Change the fuel tank access door cutout keyway profile in accordance with Paragraph 3.B.3. Part 3 - Fuel Tank Access Door Cutout Keyway Profile Change. No crack found in fuel tank access door cutout keyway

- Before further flight.Repair access door cutout keyway in accordance with Paragraph 3.B.4 Part 4 - Fuel Tank Access Door Cutout Keyway Repair Any crack found that is 0.030 inch or less in length in fuel tank access door cutout keyway

- Before further flight. Contact Boeing for repair instructions and do the repair. Any crack found that is greater than 0.030 inch in length. **F. Approval** This service bulletin was examined by the Federal Aviation Administration (FAA). The changes specified in this service bulletin comply with the applicable regulations and are FAA approved, as well as European Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on the airplane in its original Boeing delivery configuration or as modified by other approved Boeing changes. If an airplane has a non-Boeing modification or repair that affects a component or system also affected by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval before incorporating this service bulletin. **G. Manpower** The table below shows an estimate of the task hours necessary to do this inspection and change for each airplane. This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator task hour data if necessary. The estimate does not include lost time. These are some examples of lost time: • Time to adjust to the workplace • Time to schedule the work • Time to inspect the work • Time to cure the materials • Time to make the parts • Time to find the tools.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 14 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT Elapsed**  **Hours Task**  **Hours Number of**  **Persons Task** 

4.75 19.00 4 Open Access Inspect for keyway 0.10 0.10 1 Left Wing - FIGURE 1 0.10 0.10 1 Right Wing - FIGURE 2 Inspect for cracking in keyway 1.00 1.00 1 Left wing - FIGURE 3 1.00 1.00 1 Right wing - FIGURE 4 Change Keyway Profile 2.00 2.00 1 Left wing - FIGURE 5 2.00 2.00 1 Right wing - FIGURE 6 Keyway Repair 2.50 2.50 1 Left Wing - FIGURE 7 2.50 2.50 1 Right Wing - FIGURE 8 1.75 7 4 Close Access (a) (a) TOTAL FOR EACH AIRPLANE (a) The total task hours and elapsed time will depend on whether any cracks are found or not during the inspection. **H. Weight and Balance Changes** None. **I. Electrical Load Data** Not changed. **J. References** 1. Existing Data a. Boeing Service Related Problem (SRP) 777-SRP-57-0222. b. Standard Overhaul Practices Manual (SOPM) 20-10-03, 20-43-03. c. 737 Non-Destructive Testing (NDT) Manual Part 6, 51-00-00 Figure 4 and Figure 23. d. 737-600/700/800/900 Aircraft Maintenance Manual (AMM) 28-11-00, 28-11-31, 28-26-00. 2. Data supplied with this Service Bulletin None.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 15 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**3. Installation Drawings Used in the Preparation of this Service Bulletin None. **K. Publications Affected** 1. Publications: None. 2. Damage Tolerance Based Structural Inspections: Boeing has evaluated the repairs and/or changes in this service bulletin for effects on Fatigue Critical Structure (FCS) and for changes to Damage Tolerance Inspections (DTI) required in the Maintenance Program. This service bulletin affects FCS but no new DTIs are necessary. **L. Interchangeability and Intermixability of Parts** Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 16 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT 2. MATERIAL INFORMATION**  **A. Material - Price and Availability** None. **B. Industry Support Information** Boeing warranty remedies are available for 737 airplanes in warranty as of May 1, 2008. For task hour and material reimbursement for airplanes in warranty as of that date, send a warranty claim to Boeing Commercial Airplanes Group - Warranties. **C. Parts Necessary For Each Airplane** 1. Kits/Parts None. 2. Parts and Materials Supplied by the Operator The following parts or materials are necessary to do the change in this service bulletin. Parts and materials in the manuals given in Paragraph 1.J., References, can also be necessary. Examine operator supply to make sure all necessary parts and materials are available.
**Notes Name**  **QTY Part Number / Specifica-**  **tion** (b) Chemical Conversion Coating 2 Oz. Type 2, Class A (a) Corrosion Resistant Finish 4 Oz. BMS 10-20, TYPE II (a) See the Qualified Products List at the end of the Boeing Material Specification (BMS) for supplier data. (b) Refer to SOPM 20-43-03 for supplier data.
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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 17 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 18 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT 3. ACCOMPLISHMENT INSTRUCTIONS**  **A. GENERAL INFORMATION CAUTION:**  KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL, METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR OTHER ELECTRICAL DAMAGE. **NOTE:** 1. The instructions identified in Paragraph 3.B., Work Instructions and the Figure(s) give the recommended sequence of steps. The sequence of steps to do this service bulletin can be changed. 2. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for definition of the acronyms. 3. Obey all of the warnings and cautions given in the specified manual sections. 4. Unless shown differently, these dimensions and tolerances are used: – Linear dimensions are in inches – Tolerance on linear dimensions is plus or minus 0.03 inch 5. 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. **B. WORK INSTRUCTIONS** 1. PART 1: PREPARATION a. Defuel the center fuel tank. Refer to 737-600/700/800/900 AMM 28-26-00 as an accepted procedure. b. Purge the center fuel tank and prepare for entry. Refer to 737-600/700/800/900 AMM 28-11-00 as an accepted procedure. c. Remove fuel tank access doors 531BB (left wing) and 631BB (right wing). Refer to 737-600/700/800/900 AMM 28-11-31 as accepted procedures. d. Do an inspection for a keyway in the the fuel tank access door 531BB cutout in accordance with FIGURE 1 and the fuel tank access door 631BB cutout in accordance with FIGURE 2. (1) If the access door cutout does not have a keyway then no more work is necessary. Do 5. PART 5 - Restoration. (2) If the access door cutout does have a keyway then do 2. PART 2 - Fuel Tank Access Door Cutout Keyway Inspection. 2. PART 2: FUEL TANK ACCESS DOOR CUTOUT KEYWAY INSPECTION

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 19 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**a. Do a High Frequency Eddy Current (HFEC) inspection of the fuel tank access door 531BB cutout for cracks at the keyway in accordance with FIGURE 3. (1) If no crack is found, do 3. PART 3 - Fuel Tank Access Door Cutout Keyway Profile Change. (2) If any crack is found and the crack is less than or equal to 0.030 inch in length, do 4.PART 4, Fuel Tank Access Door Cutout Keyway Repair. (3) If any crack greater than 0.030 inch in length is found, contact Boeing for repair instructions and do the repair. b. Do a High Frequency Eddy Current (HFEC) inspection of the fuel tank access door 631BB cutout for cracks at the keyway in accordance with FIGURE 4. (1) If no crack is found, do 3. PART 3 - Fuel Tank Access Door Cutout Keyway Profile Change. (2) If any crack is found and the crack is less than or equal to 0.030 inch in length, do 4.PART 4, Fuel Tank Access Door Cutout Keyway Repair. (3) If any crack greater than 0.030 inch in length is found, contact Boeing for repair instructions and do the repair. 3. PART 3 : FUEL TANK ACCESS DOOR CUTOUT KEYWAY PROFILE CHANGE a. Change the profile of the fuel tank access door cutout keyway on the left wing in accordance with FIGURE 5. b. Change the profile of the fuel tank access door cutout keyway on the right wing in accordance with FIGURE 6. 4. PART 4: FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR a. Remove the crack in the fuel tank access door cutout keyway on the left wing in accordance with FIGURE 7. b. Remove the crack in the fuel tank access door cutout keyway on the right wing in accordance with FIGURE 8. 5. PART 5: RESTORATION a. Install fuel tank access doors 531BB (left wing) and 631BB (right wing). Refer to 737-600/700/800/900 AMM 28-11-31 as accepted procedures. b. Put the airplane back to a serviceable condition.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1: October 01, 2009 20 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 1: LEFT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 21 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 1: LEFT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 22 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** (a) 1

- Fuel Tank Access Door Cutout Keyway Inspect 1 (a) Inspect the fuel tank access door 531BB cutout for a keyway.

**FIGURE 1: LEFT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 23 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 2: RIGHT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 24 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 2: RIGHT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 25 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** (a) 1

- Fuel Tank Access Door Cutout Keyway Inspect 1 (a) Inspect the fuel tank access door 631BB cutout for a keyway.

**FIGURE 2: RIGHT WING - ACCESS DOOR CUTOUT - INSPECTION FOR KEYWAY (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 26 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 3: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 27 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 3: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 28 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** Do a High Frequency Eddy Current (HFEC) inspection of the indicated area for cracks in accordance with 737 NDT Part 6, 51- 00-00 Figure 4 or Figure 23. - - Fuel Tank Access Door Cutout Keyway Inspect 1

**FIGURE 3: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 29 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 4: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 30 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 4: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 31 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** Do a High Frequency Eddy Current (HFEC) inspection of the indicated area for cracks in accordance with 737 NDT Part 6, 51- 00-00 Figure 4 or Figure 23. - - Fuel Tank Access Door Cutout Keyway Inspect 1

**FIGURE 4: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - HFEC INSPECTION (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 32 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 5: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 33 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 5: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 34 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT NOTE:**  Material of the wing panel is 2324 T-39 aluminum.
**MORE DATA QTY**  **IDENTIFICATION NAME**  **TASK STEP**  Machine the wing panel an additional 0.020 to 0.040 inchbeyond the keyway as an insurance cut. Machine the wing panel to obtain a 3.0 inch radius at the keyway as shown. Blend new radius into the existing cutout with a 3.0 inch return radius. 1

- Fuel Tank Access Door Cutout Keyway Change 1

Break sharp edges. 1

- Fuel Tank Access Door Cutout Keyway Change 2 Intensity: 0.004A to 0.007A. 1

- Fuel Tank Access Door Cutout Keyway Shot Peen 3 Coverage: 2.0. Shot peen machined edges. Refer to SOPM 20-10-03 as an accepted procedure. Apply to machined areas. Refer to SOPM 20-43-03 as an accepted procedure. - TYPE 2, CLASS A Chemical Conversion Coating Apply 4

Apply one coat only to machined areas. Do not apply to surface where the gasket seats. - BMS 10-20, TYPE II Corrosion Resistant Finish Apply

**FIGURE 5: LEFT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 35 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 6: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 36 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 6: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 37 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** Machine the wing panel an additional 0.020 to 0.040 inchbeyond the keyway as an insurance cut. Machine the wing panel to obtain a 3.0 inch radius at the keyway as shown. Blend new radius into the existing cutout with a 3.0 inch return radius. 1

- Fuel Tank Access Door Cutout Keyway Change 1

Break sharp edges. 1

- Fuel Tank Access Door Cutout Keyway Change 2 Intensity: 0.004A to 0.007A. 1

- Fuel Tank Access Door Cutout Keyway Shot Peen 3 Coverage: 2.0. Shot peen machined edges. Refer to SOPM 20-10-03 as an accepted procedure. Apply to machined areas. Refer to SOPM 20-43-03 as an accepted procedure. - TYPE 2, CLASS A Chemical Conversion Coating Apply 4

Apply one coat only to machined areas. Do not apply to surface where the gasket seats. - BMS 10-20, TYPE II Corrosion Resistant Finish Apply

**FIGURE 6: RIGHT WING - ACCESS DOOR CUTOUT KEYWAY - KEYWAY PROFILE CHANGE (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 38 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 7: LEFT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 39 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 7: LEFT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 40 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** Machine the wing panel to obtain a 3.0 inch radius at the keyway as shown. 1

- Fuel Tank Access Door Cutout Keyway Change 1

Move the radius to a maximum of 0.030 inch from thekeyway as required to remove the crack. Maintain a125 microinch or better surface finish. Do a High Frequency Eddy Current (HFEC) inspection of the machined areas for cracks in accordance with 737 NDT Part 6, 51-00-00 Figure 4 or Figure 23. If acrack is found after the keyway has been machined, contact Boeing for additional instructions and do the repair. 1

- Fuel Tank Access Door Cutout Keyway Inspect 2

Machine the wing panel an additional 0.020 to 0.040 asan insurance cut to fully remove the crack. Keep a 3.0 inch radius at the keyway as shown. Blend the new radius into the existing cutout with a 3.0 inch return radius. 1

- Fuel Tank Access Door Cutout Keyway Change 3

Break sharp edges. 1

- Fuel Tank Access Door Cutout Keyway Change 4 Intensity: 0.004A to 0.007A. 1

- Fuel Tank Access Door Cutout Keyway Shot Peen 5 Coverage: 2.0. Shot peen machined edges. Refer to SOPM 20-10-03 as an accepted procedure. Apply to machined areas. Refer to SOPM 20-43-03 as an accepted procedure. - TYPE 2, CLASS A Chemical Conversion Coating Apply 6

Apply one coat only to machined areas. Do not apply to surface where the gasket seats. - BMS 10-20, TYPE II Corrosion Resistant Finish Apply

**FIGURE 7: LEFT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 41 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT FIGURE 8: RIGHT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 42 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY numbers shown below are the number of parts necessary for one side of the airplane.

**FIGURE 8: RIGHT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR (SHEET 2 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 43 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT MORE DATA**  **QTY IDENTIFICATION**  **NAME TASK**  **STEP** Machine the wing panel to obtain a 3.0 inch radius at the keyway as shown. 1

- Fuel Tank Access Door Cutout Keyway Change 1

Move the radius to a maximum of 0.030 inch from thekeyway as required to remove the crack. Maintain a125 microinch or better surface finish. Do a High Frequency Eddy Current (HFEC) inspection of the machined areas for cracks in accordance with 737 NDT Part 6, 51-00-00 Figure 4 or Figure 23. If acrack is found after the keyway has been machined, contact Boeing for additional instructions and do the repair. 1

- Fuel Tank Access Door Cutout Keyway Inspect 2

Machine the wing panel an additional 0.020 to 0.040 asan insurance cut to fully remove the crack. Keep a 3.0 inch radius at the keyway as shown. Blend the new radius into the existing cutout with a 3.0 inch return radius. 1

- Fuel Tank Access Door Cutout Keyway Change 3

Break sharp edges. 1

- Fuel Tank Access Door Cutout Keyway Change 4 Intensity: 0.004A to 0.007A. 1

- Fuel Tank Access Door Cutout Keyway Shot Peen 5 Coverage: 2.0. Shot peen machined edges. Refer to SOPM 20-10-03 as an accepted procedure. Apply to machined areas. Refer to SOPM 20-43-03 as an accepted procedure. - TYPE 2, CLASS A Chemical Conversion Coating Apply 6

Apply one coat only to machined areas. Do not apply to surface where the gasket seats. - BMS 10-20, TYPE II Corrosion Resistant Finish Apply

**FIGURE 8: RIGHT WING - FUEL TANK ACCESS DOOR CUTOUT KEYWAY REPAIR (SHEET 3 OF 3)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: August 21, 2009 737-57A1308 Revision 1 October 01, 2009 44 of 44 **BOEING SERVICE BULLETIN 737-57A1308 ALERT**  **ALERT**