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ALERT ALERT Commercial Airplanes 737

ALERTALERT Service Bulletin Number: 737-53A1210 Original Issue: December 14, 2000 Revision 3: July 16, 2009 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Fuselage Skin Chem-Mill Line Crack Inspection and Repair

BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2000 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter.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, 707, 717, 727, 737, 747, 757, 767, 777, BBJ, BOEING BUSINESS JET, DC-8, DC-9, DC-10, MD-10, MD-11, MD-80, MD-90, the Boeing logo and the Boeing livery are among the trademarks owned by Boeing or its subsidiaries. No intellectual property license (express or implied) is granted in connection with this document or otherwise.

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BLANK PAGE Original Issue: December 14, 2000 Revision 3: July 16, 2009 737-53A1210 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 2 of 267 BOEING SERVICE BULLETIN 737-53A1210

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Table of Contents Original Issue: December 14, 2000 Revision 3: July 16, 2009 737-53A1210 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 3 of 267 BOEING SERVICE BULLETIN 737-53A1210

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Table of Contents Revision Transmittal Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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

2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 E. Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 H. Weight and Balance Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

1. Existing Data: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

2. Data supplied with this Service Bulletin: . . . . . . . . . . . . . . . . . . . . . . . . . 79

3. Installation Drawings Used in the Preparation of this Service Bulletin: . . . . . . . . . . 80 K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . 80

2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 A. Material - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 C. Parts Necessary For Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

1. Kits/Parts: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

2. Parts and Materials Supplied by the Operator: . . . . . . . . . . . . . . . . . . . . . . 81

3. Parts Modified and Reidentified: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

4. Parts Removed and Not Replaced: . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 E. Special Tooling - Price and Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . 84

3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 FIGURE 1: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . . 105 FIGURE 2: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . . 106 FIGURE 3: SKIN INSPECTIONS IN THE CROWN AREA AND OTHER AREAS OF KNOWN CRACKING 107 FIGURE 4: SKIN INSPECTIONS IN THE CROWN AREA AND OTHER AREAS OF KNOWN CRACKING 112 FIGURE 5: CROWN AREA SKIN INSPECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 FIGURE 6: CROWN AREA SKIN INSPECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 FIGURE 7: CROWN AREA SKIN INSPECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 FIGURE 8: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . . 126 FIGURE 9: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . . 127

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FIGURE 10: PREVENTIVE MODIFICATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8 FIGURE 11: SKIN INSPECTIONS IN THE LOWER LOBE AREA AND IN SECTION 41 . . . . . . . 135 FIGURE 12: SKIN INSPECTIONS IN THE LOWER LOBE AREA AND IN SECTION 41 . . . . . . . 138 FIGURE 13: SKIN INSPECTIONS IN THE LOWER LOBE AREA AND IN SECTION 41 . . . . . . . 141 FIGURE 14: SKIN INSPECTIONS IN THE LOWER LOBE AREA . . . . . . . . . . . . . . . . . . . 144 FIGURE 15: SKIN INSPECTIONS IN THE LOWER LOBE AREA . . . . . . . . . . . . . . . . . . . 147 FIGURE 16: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . 150 FIGURE 17: TIME-LIMITED SKIN REPAIR AT A LAP JOINT . . . . . . . . . . . . . . . . . . . . . 151 FIGURE 18: INSPECTION OF THE TIME-LIMITED SKIN REPAIR AT A LAP JOINT. . . . . . . . . 157 FIGURE 19: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . 160 FIGURE 20: THIS FIGURE WAS DELETED AT REVISION 2 . . . . . . . . . . . . . . . . . . . . . 161 FIGURE 21: SECTION 41 - EXTERNAL INSPECTION BETWEEN STA 259.5 AND STA 360 - S-19R TO 24R AND S-4L TO S-4R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 FIGURE 22: SECTION 41 - EXTERNAL INSPECTION BETWEEN STA 259.5 AND STA 360 - S-24R TO S-24 L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 FIGURE 23: TEAR STRAP ATTACHMENT TO SKIN INSPECTION . . . . . . . . . . . . . . . . . 166 FIGURE 24: SKIN CHEM-MILL LINE CRACK AT STRINGER 12 - REPAIR . . . . . . . . . . . . . 168 FIGURE 25: INSPECTION FOR VERTICAL CRACKS AT CHEM-MILL LINES OF FUSELAGE SKIN 175 FIGURE 26: SKIN INSPECTION - LEFT AND RIGHT HAND SIDE BETWEEN STA 360 AND STA 540, STRINGER 14 - STRINGER 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 FIGURE 27: SKIN INSPECTION - RIGHT HAND SIDE BETWEEN STA 360 AND STA 540, STRINGER 14

- STRINGER 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8 FIGURE 28: SECTION 41 - SKIN INSPECTION - STRINGER-18R AND STRINGER-19R BETWEEN STA 303 AND STA 320 AND STRINGER- 15R BETWEEN STA 344 AND STA 352 . . . . 196 FIGURE 29: SKIN INSPECTIONS IN THE LOWER LOBE AREA . . . . . . . . . . . . . . . . . . . 198 FIGURE 30: TYPICAL INTERNAL INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 FIGURE 31: SKIN INSPECTION - LEFT HAND SIDE BETWEEN STA 490 AND STA 500, STRINGER 17L 204 FIGURE 32: SKIN INSPECTION - LEFT HAND SIDE BETWEEN STA 727 AND STA 1016 . . . . . 206 FIGURE 33: SKIN INSPECTION - LEFT HAND SIDE BETWEEN STA 360 AND STA 540 AND STA 727 AND STA 1016 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 8 FIGURE 34: SKIN INSPECTION - LEFT AND RIGHT SIDE BETWEEN STA 360 AND STA 540. . . 212 FIGURE 35: SKIN INSPECTION - LEFT AND RIGHT SIDE BETWEEN STA 727 AND 1016. . . . . 218 FIGURE 36: SKIN INSPECTION - LEFT SIDE BETWEEN STA 360 AND STA 540. . . . . . . . . . 222 FIGURE 37: SKIN INSPECTION - LEFT SIDE BETWEEN STA 360 AND STA 540. . . . . . . . . . 224 FIGURE 38: TIME LIMITED REPAIR - CHEM-MILL CRACKS - NOT LOCATED AT LAP JOINTS . . 226 FIGURE 39: INSPECTION FOR VERTICAL CRACKS AT CHEM-MILL LINES OF FUSELAGE SKIN 230 FIGURE 40: INSPECTION FOR VERTICAL CRACKS AT CHEM-MILL LINES OF FUSELAGE SKIN 234 FIGURE 41: SKIN INSPECTIONS IN THE LOWER LOBE AREA . . . . . . . . . . . . . . . . . . . 238 FIGURE 42: FUSELAGE WINDOW BELT AREA INSPECTION . . . . . . . . . . . . . . . . . . . . 241 FIGURE 43: FUSELAGE WINDOW BELT AREA INSPECTION . . . . . . . . . . . . . . . . . . . . 244 FIGURE 44: FUSELAGE WINDOW BELT AREA INSPECTION . . . . . . . . . . . . . . . . . . . . 248 FIGURE 45: CROWN AREA SKIN INSPECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 251 FIGURE 46: CROWN AREA SKIN INSPECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 254 FIGURE 47: INSPECTION FOR VERTICAL CRACKS AT CHEM-MILL LINES OF FUSELAGE SKIN 257 FIGURE 48: POST REPAIR INSPECTION - SKIN CHEM-MILL CRACK REPAIR AT STRINGER 12 261 FIGURE 49: INSPECTION FOR VERTICAL CRACKS AT CHEM-MILL LINES OF FUSELAGE SKIN 263

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Table of Contents Original Issue: December 14, 2000 Revision 3: July 16, 2009 737-53A1210 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 5 of 267 BOEING SERVICE BULLETIN 737-53A1210

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APPENDIX A: COST BENEFIT ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

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Table of Contents Original Issue: December 14, 2000 Revision 3: July 16, 2009 737-53A1210 BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. 6 of 267 BOEING SERVICE BULLETIN 737-53A1210

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ALERT ALERT Commercial Airplanes 737

ALERTALERT Service Bulletin Number: 737-53A1210 Revision Transmittal Sheet Original Issue: December 14, 2000 Revision 3: July 16, 2009 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Fuselage Skin Chem-Mill Line Crack Inspection and Repair This revision includes all pages of the service bulletin.

COMPLIANCE INFORMATION RELATED TO THIS REVISION No more work is necessary on airplanes inspected as shown in Revision 2 of this service bulletin.

More work is necessary on airplanes inspected as shown in the original issue or revision 1 of this service bulletin. Additional areas have been identified to be inspected for vertical and horizontal chem-mill line cracks.

Inspection areas are clearly identified to facilitate compliance.

Airplanes PM551-PM557, PM559-PM563, PW037-PW050, PW052-PW054, PW094, PW106, PW156-PW157, PW261, PW265-PW268, PW281, PW293, PW296, PW504, PW519-PW520, PW526, PW536-PW545, PW556, PW564, PW575-PW576, PW595-PW596, PW616, PW633-PW634, PW662, PW681-PW683, PW701-PW702, PW711-PW717, PW741-PW742, PW761, PW771 are added to Group 16 of this service bulletin effectivity.

REASON FOR REVISION This revision is sent to add 737-400 airplanes to this service bulletin effectivity that were incorrectly removed in revision 2 of this service bulletin.

Changes to this service bulletin include: - — Paragraph 1.A., Effectivity: Airplanes PM551-PM557, PM559-PM563, PW037-PW050, PW052-PW054, PW094, PW106, PW156-PW157, PW261, PW265-PW268, PW281, PW293, PW296, PW504, PW519- PW520, PW526, PW536-PW545, PW556, PW564, PW575-PW576, PW595-PW596, PW616, PW633- PW634, PW662, PW681-PW683, PW701-PW702, PW711-PW717, PW741-PW742, PW761, PW771 are added to the Group 16 effectivity.

— Summary Compliance: FAA Airworthiness Directive is added.

— Paragraph 1.E.,Compliance: FAA Airworthiness Directive is added. Compliance information and SRM reference is updated. Damage tolerance based structural inspection statement is moved to Paragraph 1.K.

Publications Affected.

— Paragraph 1.F., Approval: Approval information is updated.

— Paragraph 1.G., Manpower: Manpower tables for Group 6, Group 7 and Group 8 is updated.

— Paragraph 1.H.,Weight and Balance Changes: Weight and balance information is updated.

— Paragraph 1.J., References, 1. Existing Data: FAA Airworthiness Directive is added and SRM reference is updated.

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ALERT ALERT

— Paragraph 2.C.2. Parts and Material Supplied by the Operator: Brackets are added to the ends of fastener part numbers.

— Paragraph 3.B., Work Instructions, 1 Part 1, 5 Part 5 and 6 Part 6: SRM reference is updated.

— Paragraph 3.B., Work Instructions, 6 Part 6 a.,(1),(a),4),{d}: A note is added to clarify staggered fasteners locations common to the time limited repair.

— FIGURE 17 and FIGURE 18: The fastener pattern has been changed to stagger fasteners common to the tear strap.

— FIGURE 24: Brackets are added to the ends of fastener part numbers and SRM reference is updated.

— FIGURE 35: A new inspection area is added.

Paragraph 1.A., Effectivity, shows changes of airplane operators. Each operator should examine the Effectivity paragraph for changes.

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

Pages with no vertical lines have no important changes.

REVISION HISTORY Original Issue: December 14, 2000 Revision 1: October 25, 2001 Revision 2: March 3, 2009 Revision 3: July 16, 2009

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ALERT ALERT Commercial Airplanes 737

ALERTALERT Service Bulletin Number: 737-53A1210 Summary Original Issue: December 14, 2000 Revision 3: July 16, 2009 ATA System: 5331 SUBJECT: FUSELAGE - Skin - Fuselage Skin Chem-Mill Line Crack Inspection and Repair

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 Accomplishment of the inspections, modifications and repairs given in this service bulletin will ensure that fuselage skin cracks at chem-mill lines are found and repaired. This action is necessary to find and fix fatigue cracking of the skin panels which could result in sudden fracture and failure of the skin panels of the fuselage, and consequent rapid decompression of the airplane.

Operators have reported horizontal cracks along the edges of the chem-milled pockets in the skin at S-12 in the bay forward of body station STA 520 and just above the S-4, S-10, and S-14 lap joints. Operators have reported 37 horizontal chem-mill line cracks of the fuselage crown skin at non-lap-joint areas. Skin inspection maps as given in this service bulletin present areas that need to be inspected for crown chem-mill line cracks. Fuselage skin cracks at tear strap attachments to the fuselage skin have also been reported by some operators. The chem-mill cracks were up to 8 inches long, and on at least 4 of the airplanes multiple adjacent bays were found to be cracked along the same stringer. These airplanes had flown 23,425 to 64,420 flight-cycles.

Operators have reported numerous horizontal skin cracks along the edges of the chem-milled pockets in the skin below S-14, and section 41. The cracks were up to 7.25 inches long. These airplanes had flown 22,786 - 80,113 flight-cycles.

Operators have also reported 13 circumferential cracks along the vertical chem-mill steps of the fuselage skin next to the STA 360, STA 727 and STA 908 Butt-Joints. The most critical situation was four in-line cracks in multiple adjacent bays on the aft side of the STA 908 butt joint from S-3R to S-7R. Crack lengths varied from

0.75 inch to 4 inches. These airplanes had flown 45,100 flight cycles (65,200 flight hours) to 67,400 flight cycles (70,800 flight hours).

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ALERT ALERT

Analysis by Boeing indicates that these cracks are caused by fatigue due to tension stresses plus local bending stresses at the edge of chem-milled pockets or bonded skin doublers. Boeing did a cost benefit analysis on the changes given in this service bulletin. Refer to Appendix A for the analysis.

Boeing Service Related Problem (SRP) 737-SRP-53-0281 is related to this service bulletin.

ACTION On all affected airplanes, do a detailed inspection and eddy current inspection of the fuselage skin for cracks at S-12 in the bay forward of STA 520, just above the S-4, S-10, and S-14 lap joints from STA 360 to STA 1016, at S-15 between STA 360 and STA 540, aft of STA 727 and other locations of known cracking identified in this service bulletin. Skin inspection maps as given in this service bulletin indicate additional areas that need to be inspected for possible signs of chem-mill line cracks at the fuselage crown.

On all affected airplanes, do a High Frequency Eddy current (HFEC) Sliding Probe inspection of the tear strap attachments to the fuselage skin for signs of cracks at the locations as given in this service bulletin.

On all affected airplanes, do detailed inspection of the crown area skins from S-10L to S-10R between STA 360 and STA 1016 for indications of horizontal chem-mill line cracks.

On all affected airplanes, do a detailed inspection of the lower lobe skins for cracks from S-14L to S-14R, between STA 360 and STA 1016 and in Section 41 as given in this service bulletin. Skin inspection maps as given in this service bulletin indicate additional areas that need to be inspected for possible signs of chem-mill line cracks at the fuselage lower lobe and section 41.

Also, on all affected airplanes do a detailed inspection and eddy current inspections of the fuselage crown skin (from S-10L to S-10R) for vertical cracks just forward and aft of STA 360, STA 500C, STA 540, STA 727, STA 727G, and STA 908, as applicable depending on the model, along the chem-mill lines as provided in this Service Bulletin.

If any crack is found, repair as given in this service bulletin, or contact Boeing for repair instructions and install the repair.

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

COMPLIANCE Federal Aviation Administration (FAA) Airworthiness Directive 2004-18-06 and 98-11-04 R1 are related to this service bulletin.

See Service Bulletin Paragraph 1.E. for compliance information.

INDUSTRY SUPPORT INFORMATION Boeing warranty remedies are not available for the inspection and repair procedures given in this service bulletin.

MANPOWER Refer to Paragraph 1.G., Manpower.

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ALERT ALERT

MATERIAL INFORMATION Operator Supplied Parts/Materials. Refer to Paragraph 2.A., Material - Price and Availability.

DO DETAILED INSPECTIONS OF THE LOWER LOBE SKINS BELOW S-14 FROM STA 360 TO STA 1016 AND SECTION 41 FOR CRACKS. ALSO DO

DETAILED INSPECTIONS OF THE UPPER LOBE SKINS ABOVE S-10 BETWEEN STA 360 AND STA 1016. IF

ANY CRACK IS FOUND, REPAIR AS GIVEN IN THIS

SERVICE BULLETIN, OR CONTACT BOEING FOR REPAIR INSTRUCTIONS AND INSTALL THE REPAIR.

DO DETAILED INSPECTION AND EDDY CURRENT INSPECTION FOR CRACKS JUST ABOVE S-4, S-10 AND S-14 BETWEEN STA 360 TO STA 1016 AND ALONG THE CHEM-MILL LINES AT S-12, BETWEEN STA 500D TO STA 520 FOR 737-300, STA 482B TO 520 FOR 737-500, AND STA 500E TO 520 FOR 737-400. ALSO IN THE CROWN BETWEEN S-10L AND S-10R, AND AT S-15 BETWEEN STA 360 AND STA 540 AND AFT OF STA 727. IF ANY CRACK IS FOUND,

REPAIR AS GIVEN IN THIS SERVICE BULLETIN, OR CONTACT BOEING FOR REPAIR INSTRUCTIONS AND INSTALL THE REPAIR.

ADDITIONAL INSPECTION MAPS ARE GIVEN IN THE SERVICE BULLETIN.

S-4L S-10L S-14L S-15L STA 360 STA 540 STA 727 STA 908 STA 1016 STA

259.5

LEFT SIDE SHOWN

RIGHT SIDE OPPOSITE 737-400 SHOWN,

OTHER MODELS ARE SIMILAR V21666

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ALERT ALERT

S-10R STA 360 STA 540 STA 727 STA 908 STA 500C STA 727G 737-400 SHOWN

OTHER MODELS ARE

SIMILAR

DO EDDY CURRENT INSPECTIONS OF THE FUSELAGE SKIN FOR VERTICAL

CRACKS ALONG THE CHEM-MILL LINES AT THE BUTT JOINT AND OTHER LOCATIONS GIVEN IN THIS SERVICE BULLETIN. IF ANY CRACK IS

FOUND, REPAIR AS GIVEN IN THIS SERVICE BULLETIN, OR CONTACT BOEING FOR REPAIR INSTRUCTIONS AND INSTALL THE REPAIR.

1522051

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