# Boeing Alert Service Bulletin 747-55A2050: Revision 2 - Rights: © The Boeing Company. Filed by the FAA in regulations.gov docket FAA-2015-5816; AD 2016-25-05 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [Boeing Alert Service Bulletin 747-55A2050](https://openairdocs.org/service-documents/boeing/747-55a2050.md) - Title as filed: U.S. DOT/FAA - SB-747-55A2050-02 - Pages: 249 - PDF: https://openairdocs.org/files/sha256/ba/9a/ba9aa00c91da50653e0eb3bf56ffde00ede36ebb9a7aeeedb1038981fd8f62ed - Page: https://openairdocs.org/service-documents/boeing/747-55a2050/file/ba9aa00c91da ## Text Some pages are OCR from a scan. OCR can misread letters and numbers. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 Commercial Airplanes 747 Service Bulletin Number: 747-55A2050 Original Issue: February 28, 2002 Revision 2: January 23, 2015 ATA System: 5510 SUBJECT: STABILIZERS - Horizontal Stabilizer - Upper Skin and Upper Rear Spar Chord Inspection 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. 9E991ECCN: 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 Unpublished Work.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, Dreamliner, BBJ, DC-8, DC-9, DC-10, KC-10, KC-46, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8, 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. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 1 of 249 4.0 ### Page 2 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 2 of 249 BOEING SERVICE BULLETIN 747-55A2050 BLANK PAGE ### Page 3 Table of Contents Revision Transmittal Sheet ............................................ 5 Summary ..................................................... 1 1 1. PLANNING INFORMATION ........................................ 1 5 A. Effectivity ............................................... 1 5 1. Airplanes ............................................ 1 5 2. Spares Affected ........................................ 2 5 B. Concurrent Requirements ...................................... 2 5 C. Reason ................................................ 2 6 D. Description .............................................. 2 7 E. Compliance .............................................. 3 2 F. Approval ............................................... 6 1 G. Manpower .............................................. 6 2 H. Weight and Balance Changes .................................... 6 6 I. Electrical Load Data ......................................... 6 6 J. References .............................................. 6 6 1. Existing Data: ......................................... 6 6 2. Data Supplied with this Service Bulletin: ........................... 6 7 3. Installation Drawings Used in the Preparation of this Service Bulletin: ........... 6 7 K. Publications Affected ........................................ 6 7 L. Interchangeability and Intermixability of Parts ........................... 6 8 M. Software Accomplishment Summary ................................ 6 8 2. MATERIAL INFORMATION ........................................ 6 9 A. Material - Price and Availability ................................... 6 9 B. Industry Support Information .................................... 7 0 C. Parts Necessary for Each Airplane ................................. 7 0 1. Kits/Parts: ........................................... 7 0 2. Parts and Materials Supplied by the Operator: ........................ 7 6 3. Parts Modified and Reidentified: ............................... 7 8 4. Parts Removed and Not Replaced: .............................. 7 8 D. Parts Necessary to Change Spares ................................. 7 8 E. Special Tooling - Price and Availability ............................... 7 8 F. Special Tooling Necessary to do this Service Bulletin ....................... 7 8 3. ACCOMPLISHMENT INSTRUCTIONS .................................. 7 9 A. GENERAL INFORMATION ..................................... 7 9 B. WORK INSTRUCTIONS ....................................... 8 0 FIGURE 1: LOGIC DIAGRAM OF INSPECTION AND MAINTENANCE ALTERNATIVES ....... 9 1 FIGURE 2: ZONE A - DETAILED AND NDT INSPECTION ........................ 9 3 FIGURE 3: ZONE B - NDT INSPECTION (GROUP 1, 2, AND 3 AIRPLANES) [Group 1-3] ...... 9 9 FIGURE 4: ZONE B - OPEN HOLE NDT INSPECTION (GROUP 1 AND 2 AIRPLANES) [Group 1-2] . 109 FIGURE 5: ZONE B - OPEN HOLE NDT INSPECTION (GROUP 3 AIRPLANES) [Group 3] ..... 1 2 1 FIGURE 6: ZONE B - OPEN HOLE NDT INSPECTION (GROUP 4, 5, 7, 8, AND 9 AIRPLANES) [Group 4-5, 7-9] ............................................ 1 3 3 FIGURE 7: ZONE B - OPEN HOLE NDT INSPECTION (GROUP 6 AIRPLANES) [Group 6] ..... 1 4 5 FIGURE 8: ZONE C MARAGING OR H-11 STEEL FASTENER INSPECTION (GROUP 1, 2, AND 3 AIRPLANES) [Group 1-3] ................................... 1 5 8 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 3 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 4 FIGURE 9: ZONE C ADDITIONAL MARAGING OR H-11 STEEL FASTENER INSPECTION (GROUP 1, 2, AND 3 AIRPLANES) [Group 1-3] ............................... 1 6 3 FIGURE 10: ZONE B MODIFICATION [Group 1-2] ............................ 1 6 6 FIGURE 11: ZONE B MODIFICATION [Group 3] ............................. 1 7 9 FIGURE 12: ZONE B MODIFICATION [Group 4-9] ............................ 1 9 5 FIGURE 13: ZONE B POST-MODIFICATION INSPECTION [Group 1-2] ................ 2 1 0 FIGURE 14: ZONE B POST-MODIFICATION INSPECTIONS [Group 3] ................ 2 1 7 FIGURE 15: ZONE B POST-MODIFICATION INSPECTIONS [Group 4-5, 7-9] ............. 2 2 4 FIGURE 16: ZONE B POST-MODIFICATION INSPECTIONS [Group 6] ................ 2 3 1 APPENDIX A: FLIGHT SAFETY SECTION ................................. 2 3 9 APPENDIX B: FEEDBACK FORM - EDGE MARGINS AND END MARGINS ............... 2 4 0 APPENDIX C: LOGIC DIAGRAM OF ZONE B INSPECTION [Group 1-6] ................. 2 4 8 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 4 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 5 Commercial Airplanes 747 Service Bulletin Revision Transmittal SheetNumber: 747-55A2050Original Issue: February 28, 2002 Revision 2: January 23, 2015 ATA System: 5510 SUBJECT: STABILIZERS - Horizontal Stabilizer - Upper Skin and Upper Rear Spar Chord Inspection This revision includes all pages of the service bulletin. COMPLIANCE INFORMATION RELATED TO THIS REVISION Federal Aviation Administration (FAA) Airworthiness Directive AD 2006-10-16 and AD 2004-07-22 R1 are related to this service bulletin. More work is necessary on airplanes inspected in accordance with the original issue and Revision 1 of this service bulletin. Do the inspections at the new compliance times given in Paragraph 1.E., Compliance. For Zone B inspection, continue to do the inspections at the new compliance times given in Paragraph 1.E., Compliance, until the optional Zone B modification is accomplished. For Zone C inspection, do additional Maraging or H-11 steel fastener inspection at the time given in Paragraph 1.E., Compliance. No airplanes were added to this service bulletin effectivity; however, new airplane groups (7, 8, and 9) were added. Airplane line number 904 (RT876) was moved from Group 5 to Group 7. Airplanes line numbers 766 (RT631) and 778 (RT632) were moved from Group 5 to Group 8. Airplane line number 932 (RT743) was moved from Group 5 to Group 9. REASON FOR REVISION This revision is sent to give reduced compliance times for Zone B inspection requirements, Zone B modification instructions, Zone B post-modification inspection instructions, additional Zone C Maraging or H-11 steel fastener inspection, and instructions to install Inconel or titanium fasteners at locations where Maraging or H-11 steel fasteners are removed. After the original issue of this service bulletin, multiple operators have reported crack findings before reaching the compliance times given in this service bulletin. Based on the additional fleet information, reduced compliance times are necessary in Zone B to detect early cracking. Due to the changes in compliance times for Zone B inspection requirements, Zone B compliance information in FIGURE 1 logic diagram was converted to a table format and moved to Paragraph 1.E., Compliance. New airplane groups were added to the effectivity to give separate compliance times for 747-400 Large Cargo Freighter (LCF) airplanes in Paragraph 1.E., Compliance. Optional Zone B modification and its post-modification inspections are given to terminate the Zone B repeat inspection requirements. Fastener hole sizes and torque values were updated in the Fastener Tables. In Zone C, additional Maraging and H-11 steel fastener inspection is necessary to make sure there are no cracked or fractured fasteners. For the additional Zone C inspection, separate compliance information and inspection instructions are added. Instructions are changed to install Inconel or titanium fasteners at locations where Maraging or H-11 steel fasteners are removed. Re-installation of Maraging or H-11 steel fastener is not acceptable in accordance with paragraph (n) of AD 2006-10-16. The data given in Information Notice 747-55A2050 IN 01 is included in this revision; however, the information was changed due to the changes given in this revision. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 5 of 249 ### Page 6 The data given in Information Notice 747-55A2050 IN 02 is included in this revision. The data given in Alternative Method of Compliance Notice 747-55A2050-AMOC-01 is included in this revision. Terminology has been changed in the Work Instructions to agree with the terminology defined in Paragraph 3.A., General Information - Notes. These sections were changed: 1. In Summary, Background, updated the service history and added a planning table. 2. In Summary, Action, added headings with applicable zones and clarified repair instructions. Updated Zone C information to match work instructions and added group applicability. Added information about the optional Zone B modification. 3. In Summary, Effectivity, clarified the summary of the service bulletin effectivity by listing the minor models. 4. In Summary, Compliance, updated the FAA AD reference with the effective date of the FAA AD. Added FAA AD 2006-10-16, which supersedes AD 2002-06-02. Clarified the affected zones for the compliance information related to FIGURE 1 and added group applicability. Added a reference to Paragraph 1.E., Compliance, for the new and changed compliance information. 5. In Summary, Manpower, updated the reference to Paragraph 1.G., Manpower. 6. In Summary, Material Information, added information regarding operator supplied parts. 7. In Summary Figure, updated existing inspection summary and added information about the optional Zone B modification. 8. In Paragraph 1.A.1., Airplanes, converted existing Group Configuration information into a table format. Existing group descriptions were updated but no airplanes were added to the effectivity. 747-400 LCF airplanes in Group 5 were moved to new airplane Groups 7, 8, and 9. Also, updated the effectivity list in variable numbers. 9. In Paragraph 1.C., Reason, updated the service history and added a reason for this revision. 10. In Paragraph 1.D., Description, updated the "contact Boeing" phrase for repair instructions and group applicability. Changed Zone C inspection requirements to prevent re-installation of Maraging or H-11 steel fasteners by deleting optional Magnetic Particle Inspection (MPI) and Fluorescent Penetrant Inspection (FPI). Clarified the terminating action requirement for Zone C inspections. Added information about additional Zone C inspection requirement, optional Zone B modification, "more work" statement for this revision, and affected maintenance zones tables. 11. In Paragraph 1.E., Compliance: – Updated the FAA AD reference with the effective date of the FAA AD. Added FAA AD 2006-10-16, which supersedes AD 2002-06-02. – Clarified the description of FIGURE 1 logic diagram. – Zone B compliance information in FIGURE 1 logic diagram was converted and added to Tables 1 through 5. – Added Tables 6 through 8 to give compliance information for 747-400 LCF airplanes, which was previously given in Boeing Service Bulletin 747-53A2817. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 6 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 7 – Additional information was added to clarify the compliance information in Tables 6 through 8 and Boeing Service Bulletin 747-53A2817. – Added Table 9 to give compliance information for additional Zone C inspection. – Added Tables 10 through 14 to give compliance information for Zone B post-modification inspections. 12. In Paragraph 1.F., Approval, added an alternative method of compliance (AMOC) paragraph for AD 2006-10-16. Also, updated the AMOC paragraph for AD 2004-07-22 R1. 13. In Paragraph 1.G., Manpower, added table headers with corresponding "Part" of the work instructions. Replaced the word "examine" with the corresponding figure number in each table. Updated manpower information for Zone B open hole NDT inspection to match the changes in the accomplishment instructions. Added manpower information for additional Zone C inspection, Zone B modification and Zone B post-modification inspections. Deleted optional MPI and FPI information from Part 5 (Table 8). 14. In Paragraph 1.J.1., Existing Data, updated the reference list. 15. In Paragraph 1.K., Publications Affected, added publications affected table and damage tolerance evaluation statement. 16. Added Paragraph 1.M., Software Accomplishment Summary. 17. In Paragraph 2.A., Material - Price and Availability, updated pricing information on the inspection top kits. Added top kit information for Zone B modification. 18. In Paragraph 2.C.1., Kits/Parts, updated the existing note to clarify the top kit information. Added parts list for the modification top kits. 19. In Paragraph 2.C.2., Parts and Materials Supplied by the Operator, added optional oversize fasteners for Zone B modification and necessary material information. 20. In Paragraph 3.A., General Information, updated existing notes and added new notes. 21. In Paragraph 3.B., Work Instructions: – Access and Restoration instructions for Zones A, B, and C were moved to separate part of the work instructions to prevent repeated instructions. – Access panel callouts have been updated in Access and Restoration instructions. – Updated visual inspection terminology to match the general note. – Updated SRM repair references and "contact Boeing" phrase for repair instructions. – Added group applicability. – Changed Zone C inspection requirements to prevent installation of Maraging or H-11 steel fasteners. Deleted optional MPI and FPI in this section. – Added additional Zone C inspection requirements. – Clarified the terminating action requirement for Zone C Inspections. – Added optional Zone B modification instructions. – Added Zone B post-modification instructions. 22. In FIGURE 1, updated compliance information to be effective from the date of the AD and group applicability. Added optional Zone B modification. Deleted compliance information for Zone B inspections, which was moved to Paragraph 1.E., Compliance. Change Zone C Inspection requirements to prevent installation of Maraging or H-11 steel fasteners by deleting optional MPI and FPI. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 7 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 8 23. In FIGURE 2, change the task "Examine" to "Inspect." Clarified the type of inspection in the notes section and updated non-destructive test (NDT) references. 24. In FIGURE 3, change the task "Examine" to "Inspect." Added group applicability. Clarified the type of inspection in the notes section and updated NDT references. Also added a footnote to give instructions for areas with bushings or freeze plugs. 25. In FIGURE 4 and FIGURE 5: – Added group applicability. – Change the buttock line (BL) 40 to 43.5 in the graphic. – Updated the fastener head orientation in fastener symbols. – Change the task "Examine" to "Inspect." – Updated NDT references. – Clarified hole reaming and fastener removal/installation instructions. – Changed the MPI and FPI inspections to the magnetic inspection of the bolts to find and discard any Maraging or H-11 steel fasteners and replace them with Inconel or titanium fasteners. – Added a footnote to give instructions for areas with bushings or freeze plugs. – Updated Table 1 to give torque values for fasteners installed in accordance with service bulletin 747-55-2045. – Changed Flag Note 1 to refer to the magnetic inspection. – Clarified Flag Notes 2 and 3. – Deleted information regarding fastener substitution using Boeing Document D-590 and Boeing drawing 012W6100. – Updated the fastener torque values. – Updated fastener holes sizes to give close ream hole diameters. – Added a footnote about the close ream holes. 26. In FIGURE 6: – Added group applicability. – Change the buttock line (BL) 40 to 43.5 in the graphic. – Updated the fastener head orientation in fastener symbols. – Change the task "Examine" to "Inspect." – Updated NDT references. – Clarified hole reaming and fastener removal/installation instructions. – Added a footnote to give instructions for areas with bushings or freeze plugs. – Changed Table 1 title. – Clarified Flag Notes 3 and 4. – Deleted information regarding fastener substitution using Boeing Document D-590 and Boeing drawing 012W6100. – Updated the fastener torque values. – Updated fastener holes sizes to give close ream hole diameters. – Added a footnote about the close ream holes. 27. In FIGURE 7: – Added group applicability. – Change the buttock line (BL) 40 to 43.5 in the graphic. – Updated the fastener head orientation in fastener symbols. – Change the task "Examine" to "Inspect." – Updated NDT references. – Clarified hole reaming and fastener removal/installation instructions. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 8 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 9 – Added a manual reference for installing bonding jumper if removed. – Added a footnote to give instructions for areas with bushings or freeze plugs. – Deleted Table 1, which gave torque values for original production fasteners. – Updated the fastener torque values. – Updated fastener holes sizes to give close ream hole diameters. – Added a footnote about the close ream holes. – Deleted information regarding fastener substitution using Boeing Document D-590 and Boeing drawing 012W6100. 28. In FIGURE 8: – Added group applicability. – Change BL 40 to 43.5 in the graphic. – Changed the task "Examine" to "Inspect." – Deleted optional MPI and FPI, flag note table, and fastener torque value table to prevent installation of Maraging or H-11 steel fasteners. – Deleted Flag Note 1 and MPI/FPI related steps in illustrations. 29. Added FIGURE 9 to give additional Zone C inspection. 30. Added FIGURE 10, FIGURE 11, and FIGURE 12 to give optional Zone B modification instructions. 31. Added FIGURE 13, FIGURE 14, FIGURE 15, and FIGURE 16 to give Zone B post-modification inspection instructions. 32. In APPENDIX A, updated Flight Safety Inspection Program information. 33. Added APPENDIX B to give feedback form for edge margins and end margins when contacting Boeing. 34. Added APPENDIX C to give logic diagram for Zone B inspection. Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity and format changes, to show the location of all content changes. Pages with no vertical lines have no important changes. REVISION HISTORY February 28, 2002Original Issue: May 01, 2003Revision 1: January 23, 2015Revision 2: Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 9 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 10 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 10 of 249 BOEING SERVICE BULLETIN 747-55A2050 BLANK PAGE ### Page 11 Commercial Airplanes 747 Service Bulletin SummaryNumber: 747-55A2050Original Issue: February 28, 2002 Revision 2: January 23, 2015 ATA System: 5510 SUBJECT: STABILIZERS - Horizontal Stabilizer - Upper Skin and Upper Rear Spar Chord Inspection CONCURRENT REQUIREMENTS None. BACKGROUND This inspection when completed, will help to detect cracks in the horizontal stabilizer outboard and center section rear spar structure, hinge fittings, terminal fittings and splice plates. Cracks in this structure could cause significant degradation of the structural integrity of the horizontal stabilizer outboard and center sections and subsequent adverse effects on airplane controllability and possible loss of control of the airplane. One operator has reported finding a 3.5 inch crack in the horizontal stabilizer center section aft upper skin. The crack was located at LBL 37.8 and ran 3.5 inches forward of the aft edge of the skin. The skin and rear spar upper chord are subject of Supplemental Structural Inspection Document (SSID) E-3C. However, the airplane that the crack was found on was not a SSID candidate airplane. Subsequent to the original issue of this service bulletin multiple operators have reported cracks in the splice plates, hinge fittings, terminal fittings, and outboard and center section upper skin, upper chord, and rear spar web. Operators have also reported cracked and fractured Maraging steel fasteners. The cracks have been reported on airplanes as early as 19,200 flight-cycles/24,300 flight-hours and 8,000 flight-cycles/54,800 flight-hours. Inspection of the horizontal stabilizer hinge fitting halves, terminal fittings, splice plates, and the outboard and center section upper skins, rear spar upper chords, and rear spar webs for cracks and for cracked or fractured Maraging or H-11 steel fasteners will maintain the structural integrity of the horizontal stabilizer outboard and center sections. Boeing Service Related Problem (SRP) 747OP-SRP-55-0023 and 747OP-SRP-55-0027 are related to this service bulletin. The Federal Aviation Administration (FAA) has issued an Airworthiness Directive (AD) which requires incorporation of this service bulletin. This table is provided to operators for planning purposes only. Refer to the applicable sections for more information. ReferenceAffectedPlanning Data Paragraph 1.A.2., Spares AffectedNoSpares Affected Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 11 of 249 ### Page 12 ReferenceAffectedPlanning Data Paragraph 1.E., Compliance and Paragraph 1.F., Approval YesAD Related Paragraph 1.H., Weight and Balance ChangesNoWeight and Balance Change Paragraph 1.I., Electrical Load DataNoElectrical Load Changed Paragraph 1.K., Publications AffectedYesPublications Affected Paragraph 1.K., Publications AffectedNoAirplane Flight Operations Affected (Flight Crew Operations Manual and/or FAA Approved Air- plane Flight Manual) Paragraph 2.C.1., Kits/PartsYesKits/Parts Required Paragraph 2.C.2., Parts and Materials Supplied by the Operator YesOperator Supplied Parts/Material Paragraph 2.F., Special Tooling Necessary to do this Service Bulletin NoSpecial Tooling Required ACTION Zone A and Zone B Inspections: Gain access to the aft upper end of the horizontal stabilizer outboard and center sections, internal and external. Perform detailed and/or NDT inspections of the splice fittings, terminal fittings, hinge fitting halves, and the outboard and center section upper skins, rear spar upper chords, and rear spar webs. If any crack is found, repair cracks in accordance with the SRM or contact Boeing for repair instructions and do the repair. Group 1-3: Zone C Inspection: Do a magnetic inspection of the fasteners common to the outboard and center section rear spar upper chords to determine if they are magnetic or non-magnetic. If a bolt is magnetic, it is made from Maraging or H-11 steel. If a bolt is not magnetic, it is not made from Maraging or H-11 steel and no further action is required at that fastener location. If a bolt is magnetic, do an ultrasonic inspection for cracking or fracture. If any cracked or fractured fastener is found, replace the fastener with Inconel or titanium fastener. No further action is required once all Maraging or H-11 steel fasteners are replaced with Inconel or titanium fasteners in this inspection zone. Zone B Modification: Do optional Zone B modifications in accordance with this service bulletin, which is terminating action for the Zone B and Zone C repeat inspections. Make sure that the fastener holes that exist are free of cracks, then make the fastener holes 1/16 inch oversize in diameter and install new fasteners in accordance with this service bulletin. After the modification is accomplished, do post-modification inspections at the time given in Paragraph 1.E., Compliance. EFFECTIVITY All 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SP, and 747SR airplanes. Refer to Paragraph 1.A.1., Airplanes for the list of affected airplanes. COMPLIANCE Federal Aviation Administration (FAA) Airworthiness Directive AD 2006-10-16 and AD 2004-07-22 R1 are related to this service bulletin. The effective date of AD 2006-10-16 is June 21, 2006. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 12 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 13 Group 1-6: See FIGURE 1, Logic Diagram, for a summary of Inspection and Maintenance Alternatives for Zones A and C. Refer to Paragraph 1.E., Compliance. INDUSTRY SUPPORT INFORMATION Boeing warranty remedies are not available for the inspections given in this service bulletin. MANPOWER Refer to Paragraph 1.G., Manpower. MATERIAL INFORMATION Boeing Supplied Kits/Parts. Operator Supplied Parts/Materials. Refer to Paragraph 2.A., Material - Price and Availability. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 13 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 14 (OCR) BOEING SERVICE BULLETIN 747-55A2050 UP FWD < LBL - 43.5 RBL 43.5 DO DETAILED VISUAL AND/OR NDT INSPECTIONS OF THE HINGE FITTING HALVES, TERMINAL FITTING, SPLICE PLATE, AND OUTBOARD AND CENTER SECTION REAR SPAR UPPER CHORDS, REAR SPAR WEBS, AND UPPER SKINS. DO MAGNETIC TEST AND ULTRASONIC INSPECTION OF THE MARAGING OR H-11 STEEL FASTENERS COMMON TO THE REAR SPAR UPPER CHORDS AND SPLICE PLATE. AS AN OPTION, DO ZONE B MODIFICATION. V72950 Original Issue: February 28, 2002 Revision 2: January 23, 2015 PROPRIETARY - Copyright © Unpublished Export Controlled ECCN: 9E991 - BOEING 747-55A2050 Work - See page 1 for detalls. 14 of 249 ### Page 15 Commercial Airplanes 747 Service Bulletin Number: 747-55A2050 Original Issue: February 28, 2002 Revision 2: January 23, 2015 ATA System: 5510 SUBJECT: STABILIZERS - Horizontal Stabilizer - Upper Skin and Upper Rear Spar Chord Inspection 1. PLANNING INFORMATION A. Effectivity 1. Airplanes Refer to Service Bulletin Index Document D6-30300 Part 3 for Airplane Variable Number, Line Number, and Serial Number data. This service bulletin is for the airplanes shown below. DESCRIPTIONCONFIGURATIONGROUP 747-100 and 747-200B airplanes line numbers 1 through 167, 169 through 208, 210, 212 through 220, 222 through 228, 232, 233, 235, 236, 238 through 241, 244, 246, 247, 248, 250, and 251. -1 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SP, and 747SR airplanes line numbers 252 through 695. -2 747-200C, 747-200F, 747SR airplanes line numbers 168, 209, 211, 221, 229, 230, 231, 234, 237, 242, 243, 245, and 249. -3 747-200B, 747-200C, 747-200F, and 747-300 airplanes line numbers 697 through 886. -4 747-400, 747-400D, and 747-400F airplanes line numbers 696 through 1307. -5 747-400 and 747-400F airplanes line numbers 1308 through 1419.-6 747-400 Large Cargo Freighter (LCF) airplane line number 904.-7 747-400 LCF airplanes line numbers 766 and 778.-8 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 15 of 249 ### Page 16 DESCRIPTIONCONFIGURATIONGROUP 747-400 LCF airplane line number 932.-9 Airplane Models: 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SP, 747SR GroupVariable Number 1RA001 - RA034 1RA101 - RA115 1RA161 - RA164 1RA201 - RA203 1RA216 - RA217 1RA245 - RA246 1RA251 - RA264 2RA265 - RA266 1RA301 - RA317 2RA318 1RA351 - RA360 1RA369 - RA373 1RA401 - RA418 1RA501 - RA502 1RA521 - RA527 2RA528 1RA532 - RA542 2RA543 - RA548 1RA551 - RA552 1RA559 - RA561 1RA581 - RA582 1RA585 1RA601 - RA602 1RA631 - RA635 1RA651 - RA652 1RA671 - RA677 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 16 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 17 GroupVariable Number 1RA701 - RA702 1RA721 - RA724 2RA725 - RA731 1RA741 - RA745 1RA749 2RA750 1RA761 - RA762 1RA781 - RA783 2RA784 1RA901 - RA916 1RB001 - RB009 2RB010 - RB012 1RB013 - RB015 2RB016 1RB041 - RB044 1RB071 - RB075 1RB101 - RB102 2RB411 - RB412 4RB413 4RB421 3RB601 - RB606 2RB607 2RB681 - RB697 2RB711 2RB721 - RB723 2RB741 - RB748 1RD001 - RD003 2RD004 1RD021 - RD022 1RD041 - RD043 2RD044 - RD059 1RD071 - RD072 2RD081 - RD083 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 17 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 18 GroupVariable Number 2RD091 - RD092 1RD101 - RD104 2RD121 - RD127 2RD131 - RD144 2RD166 - RD167 2RD171 - RD172 2RD181 - RD183 2RD201 - RD204 2RD221 - RD227 2RD231 - RD234 4RD235 2RD241 - RD243 2RD251 - RD262 2RD271 - RD272 2RD291 - RD292 2RD301 - RD302 2RD311 2RD351 - RD358 2RD361 - RD366 2RD381 - RD383 2RD411 - RD414 2RD421 - RD426 2RD431 - RD435 2RD441 - RD442 2RD451 - RD456 2RD461 2RD471 - RD475 2RD513 - RD519 2RD531 - RD533 2RD551 2RD561 2RD571 2RD581 - RD583 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 18 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 19 GroupVariable Number 2RD591 - RD593 2RD601 - RD607 2RD621 - RD623 2RD641 - RD649 2RD651 - RD659 2RD661 2RD671 2RD681 - RD682 2RD691 - RD692 2RD701 - RD702 2RD721 - RD722 2RD741 - RD742 2RD751 - RD755 2RD761 2RD771 - RD775 2RD781 - RD783 2RD791 4RD792 2RE001 6RF001 - RF006 2RG001 - RG009 2RG091 2RG095 2RG101 - RG104 2RG121 - RG126 2RG141 - RG142 2RG161 - RG164 2RG171 - RG174 2RG191 - RG193 2RG211 - RG213 2RG221 - RG222 2RH101 - RH102 2RH111 - RH112 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 19 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 20 GroupVariable Number 2RH121 - RH122 3RJ131 - RJ133 2RJ151 - RJ152 2RJ301 - RJ303 2RJ321 4RJ322 2RJ331 - RJ333 5RL401 - RL402 6RL403 5RL411 - RL419 6RL420 - RL436 6RL451 - RL456 6RL461 - RL462 6RL471 - RL481 6RL491 - RL492 6RL501 - RL502 6RL511 - RL516 6RL521 - RL522 6RL531 - RL534 6RL551 6RL561 - RL568 6RL571 - RL572 6RL576 - RL577 6RL579 6RL581 - RL586 5RL651 - RL654 6RL655 6RL671 - RL675 6RL681 - RL684 5RL751 6RL752 5RM001 - RM007 5RM010 - RM013 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 20 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 21 GroupVariable Number 5RM021 - RM024 5RM026 - RM029 6RM030 5RM036 - RM045 5RM051 - RM052 6RM053 5RM071 5RM081 - RM084 5RM091 5RM096 - RM097 5RM116 - RM117 5RM126 - RM132 5RM136 - RM147 5RM156 - RM158 5RM166 - RM177 5RM191 - RM192 5RM231 - RM233 5RM241 - RM246 5RM261 - RM264 5RM316 - RM318 5RM331 - RM333 5RM341 5RM351 - RM355 5RM366 - RM367 6RM401 - RM403 6RM426 6RM431 6RM441 - RM443 6RM445 5RM801 - RM803 5RM811 - RM813 5RM851 - RM858 6RM859 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 21 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 22 GroupVariable Number 5RM861 - RM862 6RM863 5RM871 - RM876 6RM877 - RM880 5RM881 - RM886 6RM887 - RM890 5RM891 - RM899 5RM901 - RM905 6RM906 5RM911 2RR001 - RR005 2RR021 - RR023 4RR024 - RR025 2RR031 3RR201 2RR202 - RR205 4RR206 3RR221 2RR222 - RR226 3RR261 2RR262 - RR267 3RR301 2RR302 - RR306 4RR307 - RR310 2RR331 - RR332 2RR336 2RR341 - RR345 2RR361 - RR362 2RR421 - RR422 2RR431 - RR432 2RR441 4RR442 4RR451 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 22 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 23 GroupVariable Number 2RR501 - RR504 2RR521 4RR522 4RR526 2RR531 2RR551 - RR554 4RR555 - RR556 2RR561 4RR566 5RR701 5RR721 - RR724 5RR746 - RR748 5RR851 - RR856 5RR861 - RR862 5RR951 - RR952 2RS001 - RS002 2RS201 2RS211 - RS212 2RS221 - RS222 2RS231 - RS241 2RS251 - RS259 4RS263 2RS265 - RS268 2RS271 - RS276 2RS291 - RS292 2RS301 - RS305 4RS306 2RS311 - RS320 4RS331 - RS333 2RS341 - RS342 2RS699 2RS701 - RS703 2RS711 - RS713 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 23 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 24 GroupVariable Number 2RS721 - RS722 4RS731 - RS732 2RS741 - RS743 2RS751 - RS752 2RS761 4RS762 2RS771 4RS781 - RS782 4RS786 5RT001 - RT014 5RT021 - RT022 5RT031 - RT035 5RT041 - RT047 5RT061 5RT071 - RT075 5RT101 - RT103 5RT121 5RT131 - RT137 5RT151 - RT152 5RT161 - RT168 5RT401 - RT412 5RT431 - RT447 5RT451 - RT469 5RT471 - RT499 5RT501 - RT535 5RT551 - RT568 5RT571 - RT591 5RT601 - RT630 8RT631 - RT632 5RT633 - RT657 5RT671 - RT673 5RT681 - RT682 5RT691 - RT699 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 24 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 25 GroupVariable Number 5RT701 - RT704 5RT711 - RT717 5RT741 - RT742 9RT743 5RT744 - RT757 5RT776 - RT777 5RT781 - RT784 5RT801 - RT803 5RT811 - RT814 5RT831 - RT837 5RT861 - RT864 7RT876 5RT877 - RT880 5RT931 - RT932 5RT945 - RT949 5RT951 - RT955 5RT966 - RT967 5RU001 - RU006 5RU016 - RU017 5RU031 - RU032 5RU051 - RU052 5RU059 - RU062 5RU081 - RU083 5RU101 - RU102 5RU121 - RU132 5RU801 - RU809 5RU831 - RU841 2. Spares Affected None. B. Concurrent Requirements None. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 25 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 26 C. Reason This inspection when completed, will help to detect cracks in the horizontal stabilizer outboard and center section rear spar structure, hinge fittings, terminal fittings and splice plates. Cracks in this structure could cause significant degradation of the structural integrity of the horizontal outboard and center sections and subsequent adverse effects on airplane controllability and possible loss of control of the airplane. One operator has reported finding a 3.5 inch crack in the horizontal stabilizer center section aft upper skin. The crack was located at LBL 37.8 and ran 3.5 inches forward of the aft edge of the skin. The skin and rear spar upper chord are subject of Supplemental Structural Inspection Document (SSID) E-3C. However, the airplane that the crack was found on was not a SSID candidate airplane. Subsequent to the original issue of this service bulletin multiple operators have reported cracks in the splice plates, hinge fittings, terminal fittings, and outboard and center section upper skin, upper chord, and rear spar web. Operators have also reported cracked and fractured Maraging steel fasteners. The cracks have been reported on airplanes as early as 19,200 flight-cycles/24,300 flight-hours and 8,000 flight-cycles/54,800 flight-hours. Inspection of the horizontal stabilizer hinge fitting halves, terminal fittings, splice plates, and the outboard and center section upper skins, rear spar upper chords, and rear spar webs for cracks and for cracked or fractured Maraging or H-11 steel fasteners will maintain the structural integrity of the horizontal stabilizer outboard and center sections. Revision 1 is issued to: 1) Add a High Frequency Eddy Current (HFEC) inspection as an option to the detailed visual inspection in the original issue of this service bulletin. The optional HFEC inspection has a greater repeat inspection interval. The inspection area in the original issue of this service bulletin is identified as Zone A; 2) Add inspections of the structure at the splice plates and hinge fittings. This inspection covers the inboard and outboard hinge fitting halves, terminal fittings, splice plates, and the outboard and center section upper chords, webs and upper skins. This inspection area is identified as Zone B. Subsequent to the original issue of this service bulletin, 2 operators have reported 22 cracks on 6 airplanes with approximately 20,800 to 37,000 flight-cycles and 41,700 to 115,700 flight-hours; and 3) Add inspection for cracked or fractured Maraging or H-11 steel fasteners common to the horizontal stabilizer outboard and center section upper chords at the hinge fitting halves and the splice plates. This inspection area is identified as Zone C. Maraging and H-11 steel fasteners are susceptible to stress corrosion cracking and fracture. One operator has reported finding 2 fractured and 3 cracked Maraging steel fasteners on 1 airplane with approximately 18,700 flight cycles and 87,300 flight-hours. Revision 2 is sent to give reduced compliance times for Zone B inspection requirements, Zone B modification instructions, Zone B post-modification inspection instructions, additional Zone C Maraging or H-11 steel fastener inspection, and instructions to install Inconel or titanium fasteners at locations where Maraging or H-11 steel fasteners are removed. After the original issue of this service bulletin, multiple operators have reported crack findings before reaching the compliance times given in this service bulletin. Based on the additional fleet information, reduced compliance times are necessary in Zone B to detect early cracking. Due to the changes in compliance times for Zone B inspection requirements, Zone B compliance information in FIGURE 1 logic diagram was converted to a table format and moved to Paragraph 1.E., Compliance. New airplane groups were added to the effectivity to give separate compliance times for 747-400 Large Cargo Freighter (LCF) airplanes in Paragraph 1.E., Compliance. Optional Zone B modification and its post-modification inspections are given to terminate the Zone B repeat inspection requirements. Fastener hole sizes and torque values were updated in the Fastener Tables. In Zone C, additional Maraging and H-11 steel fastener inspection is Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 26 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 27 necessary to make sure there are no cracked or fractured fasteners. For the additional Zone C inspection, separate compliance information and inspection instructions are added. Instructions are changed to install Inconel or titanium fasteners at locations where Maraging or H-11 steel fasteners are removed. Re-installation of Maraging or H-11 steel fastener is not acceptable in accordance with paragraph (n) of AD 2006-10-16. The data given in Information Notice 747-55A2050 IN 01 is included in this revision; however, the information was changed due to the changes given in this revision. The data given in Information Notice 747-55A2050 IN 02 is included in this revision. The data given in Alternative Method of Compliance Notice 747-55A2050-AMOC-01 is included in this revision. Boeing Service Related Problem (SRP) 747OP-SRP-55-0023 and 747OP-SRP-55-0027 are related to this service bulletin. The Federal Aviation Administration (FAA) has issued an Airworthiness Directive (AD) which requires incorporation of this service bulletin. D. Description Zone A Inspection 1. Part 1 - Zone A Detailed Inspection Gain access to the aft upper end of the horizontal stabilizer center section, internal and external. Do a detailed inspection for cracks in the center section upper skin and rear spar upper chord. If no crack is found, repeat Part 1 - Zone A Detailed Inspection or Part 2 - Zone A NDT Inspection within the primary inspection interval shown in FIGURE 1. If any crack is found, do Part 4 - Zone B Open Hole NDT Inspection. Repair cracks in accordance with the SRM or contact Boeing for repair instructions and do the repair. Repeat Part 1 - Zone A Detailed Inspection or Part 2 - Zone A NDT Inspection within the primary inspection interval shown in FIGURE 1. 2. Part 2 - Zone A NDT Inspection Gain access to the aft upper end of the horizontal stabilizer center section, internal and external. Do a surface High Frequency Eddy Current (HFEC) Inspection for cracks in the center section upper skin and the rear spar upper chord. If no crack is found, repeat Part 1 - Zone A Detailed Inspection or Part 2 - Zone A NDT Inspection within the alternate inspection interval shown in FIGURE 1. If any crack is found, do Part 4 - Zone B Open Hole NDT Inspection. Repair cracks in accordance with the SRM or contact Boeing for repair instructions and do the repair. Repeat Part 1 - Zone A Detailed Inspection or Part 2 - Zone A NDT Inspection within the alternate inspection interval shown in FIGURE 1. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 27 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 28 Zone B Inspection 1. Part 3 - Zone B NDT Inspection Gain access to the aft upper end of the horizontal stabilizer outboard and center sections, internal and external. Do an ultrasonic inspection for cracks in the outboard and center section rear spar upper chords under the hinge fitting halves. Do an ultrasonic inspection for cracks in the outboard and center section upper skins under the splice plate. Do an ultrasonic inspection for cracks in the outboard and center section rear spar webs behind the terminal fitting. Do a surface HFEC inspection for cracks in the terminal fitting around the fasteners common to the outboard and center section rear spar upper chords. Do a Low Frequency Eddy Current (LFEC) inspection for cracks in the splice plate around the fasteners. Do a surface HFEC inspection for cracks in the outboard and center section rear spar upper chords in the radius area above the terminal fitting and the horizontal flange lower surface. Do a surface HFEC inspection for cracks in the outboard and center section rear spar webs in the exposed edge above the terminal fitting. If no crack is found, repeat Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection at the inspection interval shown in Paragraph 1.E., Compliance, or do Part 7 - Zone B Modification. If any crack is found, repair cracks in accordance with the SRM or contact Boeing for repair instructions and do the repair. Repeat Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection at the inspection interval shown in Paragraph 1.E., Compliance, or do Part 7 - Zone B Modification. 2. Part 4 - Zone B Open Hole NDT Inspection Gain access to the aft upper end of the horizontal stabilizer outboard and center sections, internal and external. Remove fasteners and do an open hole HFEC inspection of the hole for cracks in the splice plates, terminal fittings, hinge fitting halves, and the outboard and center section rear spar upper chords, rear spar webs, and upper skins. If no crack is found, repeat Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection at the inspection interval shown in Paragraph 1.E., Compliance, or do Part 7 - Zone B Modification. If any crack is found, repair cracks in accordance with the SRM or contact Boeing for repair instructions and do the repair. Repeat Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection at the inspection interval shown in Paragraph 1.E., Compliance, or do Part 7 - Zone B Modification. Group 1-3: Zone C Inspections 1. Part 5 - Zone C Maraging or H-11 Steel Fastener Inspection Gain access to the aft upper end of the horizontal stabilizer outboard and center sections, internal and external. Remove sealant from the heads and nuts of the fasteners common to the hinge fitting halves, splice plates and the outboard and center section rear spar upper chords. Do an inspection of the fasteners to determine if the fastener is magnetic. If the fastener is not magnetic, the fastener is not made from Maraging or H-11 steel, and no further action is required at that fastener location. If the fastener is magnetic, the fastener is made from Maraging or H-11 steel and do an ultrasonic inspection of the fastener for cracking or fracture. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 28 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 29 If the fastener is not cracked and fractured, repeat Part 5 - Maraging or H-11 Steel Fastener Inspection at the Interval shown in FIGURE 1. As an option to repeat inspections, do Part 4 - Zone B Open Hole NDT Inspection and replace the fastener or Part 7 - Zone B Modification. No further action is required at that fastener location. If the fastener is cracked or fractured, do Part 4 - Zone B Open Hole NDT Inspection and replace the fastener or Part 7 - Zone B Modification. No further action is required at that fastener location. NOTE: For the fasteners specified in Zone C, replacement of all magnetic (Maraging or H-11 steel) bolts with non-magnetic (Inconel or titanium) bolts terminates the Zone C repeat inspection requirements. New fasteners specified in Part 4 - Zone B Open Hole NDT Inspection and Part 7 - Zone B Modification are all non-magnetic (Inconel or titanium) bolts. 2. Part 6 - Additional Zone C Maraging or H-11 Steel Fastener Inspection Gain access to the aft upper end of the horizontal stabilizer outboard and center sections, internal and external. Remove sealant from the heads and nuts of the fasteners common to the splice plates. Do an inspection of the fasteners to determine if the fastener is magnetic. If the fastener is not magnetic, the fastener is not made from Maraging or H-11 steel, and no further action is required at that fastener location. If the fastener is magnetic, the fastener is made from Maraging or H-11 steel and do an ultrasonic inspection of the fastener for cracking or fracture. If the fastener is not cracked or fractured, repeat Part 6 - Additional Maraging or H-11 Steel Fastener Inspection at the interval shown in Paragraph 1.E., Compliance. As an option to repeat inspections, do Part 4 - Zone B Open Hole NDT Inspection and replace the fastener or Part 7 - Zone B Modification. No further action is required at that fastener location. If the fastener is cracked or fractured, do Part 4 - Zone B Open Hole NDT Inspection and replace the fastener or Part 7 - Zone B Modification. No further action is required at that fastener location. NOTE: For the fasteners specified in Zone C, replacement of all magnetic (Maraging or H-11 steel) bolts with non-magnetic (Inconel or titanium) bolts terminates the Zone C repeat inspection requirements. New fasteners specified in Part 4 - Zone B Open Hole NDT Inspection and Part 7 - Zone B Modification are all non-magnetic (Inconel or titanium) bolts. Zone B Modification 1. Part 7 - Zone B Modification As an alternative to Zone B and Zone C repeated inspections, do optional Zone B modifications in accordance with this service bulletin. Make sure that the fastener holes that exist are free of cracks, then make the fastener holes 1/16 inch oversize in diameter and install new fasteners in accordance with this service bulletin. NOTE: Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 3 - Zone B NDT Inspection, Part 4 - Zone B Open Hole NDT Inspection, Part 5 - Zone C Maraging or H-11 Steel Fastener Inspection, and Part 6 - Additional Zone C Maraging or H-11 Steel Fastener Inspection, as applicable. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 29 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 30 Zone B Post-Modification Inspection 1. Part 8 - Zone B Post-Modification Inspection After the Zone B modification, do post-modification inspections at the time given in Paragraph 1.E., Compliance. Airplane effectivity is divided into 9 groups, based on the type of fasteners used in the inspection area and airplane type. Group 1, 2, and 3 Airplanes have Maraging or H-11 steel fasteners in the inspection area. These bolts are susceptible to stress corrosion cracking. Group 4, 5, 6, 7, 8 and 9 airplanes have Inconel or titanium fasteners. Group 1, 2, 3, and 4 Airplanes are 747-100, -200 and -300 Airplanes. Group 5, 6, 7, 8, and 9 Airplanes are 747-400 airplanes. Group 4, 5, 6, 7, 8, and 9 airplanes have seal pans and fuel seal in the inspection area which prevents the accomplishment of Part 3 - Zone B NDT inspection. These airplanes must use Part 4 - Zone B Open Hole NDT Inspection. NOTE: If the damaged area is more than the specified limits, contact Boeing for repair instructions and do the repair. Give the size and location of the damage. When possible, send sketches, photographs, and cracked parts. If the damage includes corrosion, send data on the length, width, and largest depth of clean up. 1. Revision 1 - More work is necessary on airplanes inspected in accordance with the original issue of this service bulletin. Airplanes should accomplish the Zone B inspections (all groups) and Zone C inspections (Group 1, 2, and 3 Airplanes) at the initial compliance thresholds for the zone in accordance with this service bulletin. Revision 2 - More work is necessary on airplanes inspected in accordance with the original issue and Revision 1 of this service bulletin. Do the inspections at the new compliance times given in Paragraph 1.E., Compliance. For Zone B inspection, continue to do the inspections at the new compliance times given in Paragraph 1.E., Compliance, until the optional Zone B modification is accomplished. For Zone C inspection, do additional Maraging or H-11 steel fastener inspection at the time given in Paragraph 1.E., Compliance. The work in this service bulletin is done in the maintenance zone(s) given below. Group 1: Affected Maintenance Zones ZoneModel 338, 348747-100, 747-200B Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 30 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 31 Group 2: Affected Maintenance Zones ZoneModel 338, 348747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SP, 747SR Group 3: Affected Maintenance Zones ZoneModel 338, 348747-200C, 747-200F, 747SR Group 4: Affected Maintenance Zones ZoneModel 338, 348747-200B, 747-200C, 747-200F, 747-300 Group 5: Affected Maintenance Zones ZoneModel 338, 348747-400, 747-400D, 747-400F Group 6: Affected Maintenance Zones ZoneModel 338, 348747-400, 747-400F Group 7-9: Affected Maintenance Zones ZoneModel 338, 348747-400 Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 31 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 32 E. Compliance Federal Aviation Administration (FAA) Airworthiness Directive AD 2006-10-16 and AD 2004-07-22 R1 are related to this service bulletin. The effective date of AD 2006-10-16 is June 21, 2006. Group 1-6: See FIGURE 1, Logic Diagram, for a summary of Inspection and Maintenance Alternatives for Zones A and C. Zone B information has been changed and moved to Tables 1 through 5. Group 7-9: Boeing Service Bulletin 747-53A2817 was issued to give compliance information for other service bulletins, including this service bulletin. Tables 13 through 15 in Paragraph 1.E., Compliance, of Boeing Service Bulletin 747-53A2817 give compliance information related to this service bulletin. The new compliance information in Tables 6 through 8 in Paragraph 1.E., Compliance, of this service bulletin supersede the compliance information in Tables 13 through 15 in Paragraph 1.E., Compliance, of Boeing Service Bulletin 747-53A2817. All other compliance information in Boeing Service Bulletin 747-53A2817 are not affected. Group 1-3: Refer to Table 9 for additional Zone C Maraging or H-11 steel fastener inspection. Do the required actions in accordance with Paragraph 3. Accomplishment Instructions. Group 1-6: Table 1: Horizontal Stabilizer - Zone B Inspection - Compliance Table Index Repeat Interval (Not to Exceed) Compliance TimeActionCondition -Refer to Table 2.Refer to Table 2.Group 1, 3: All airplanes with less than 27,000 total-flight cycles and 117,000 total flight- hours. -Refer to Table 3.Refer to Table 3.Group 2: All airplanes with less than 27,000 total-flight cycles and less than 117,000 total flight-hours. -Refer to Table 4.Refer to Table 4Group 1-3: All airplanes with 27,000 or more total-flight cycles or 117,000 or more total flight- hours. -Refer to Table 5.Refer to Table 5Group 4-6: All airplanes. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 32 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 33 Group 1, 3: Table 2: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Before 15,000 total flight-cy- cles or 55,000 total flight- hours, whichev- er occurs first. Do non-destructive test (NDT) inspections of Zone B for cracks in ac- cordance with Part 3. As an alternative, do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. Airplanes that have not done Zone B inspection in accordance with Revision 1 of this service bulletin. – Before 20,000 flight cycles or 85,000 flight hours, whichever occurs first. – Within 2,400 flight cycles or 12,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. -Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection Repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 3. Airplanes that have done NDT inspections of Zone B in accordance with Part 3 of Paragraph 3.B., Work Instructions given in Revi- sion 1 of this service bul- letin. As an alternative, do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. (a) Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 33 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 34 Group 1, 3: Table 2: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Within 6,000 flight-cycles or 30,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4. As an alternative, do NDT inspections of Zone B for cracks in accordance with Part 3. Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4 of Para- graph 3.B., Work Instruc- tions given in Revision 1 of this service bulletin. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 8,000 flight cycles or 44,000 flight hours, whichever occurs first, from the last inspec- tion. (a) -Before further flight.Do a repair in accordance with Part 3 or Part 4. Any crack found in Zone B. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 34 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 35 Group 1, 3: Table 2: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 3. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 4. (a) Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 3. As an alternative, in the unrepaired areas do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. No crack found with NDT inspections of Zone B in accordance with Part 3 or Any crack found and re- paired in accordance with Part 3. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 35 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 36 Group 1, 3: Table 2: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 3. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 4. (a) Within 6,000 flight-cycles or 30,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. As an alternative, in the unrepaired areas and ar- eas repaired only by hole oversizing, do NDT in- spections of Zone B for cracks in accordance with Part 3. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with Part 4. (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 3 - Zone B NDT Inspection, Part 4 - Zone B Open Hole NDT Inspection, Part 5 - Zone C Maraging or H-11 Steel Fastener Inspection, and Part 6 - Additional Zone C Maraging or H-11 Steel Fastener In- spection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the modification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 36 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 37 Group 2: Table 3: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and Less Than 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Before 17,000 total flight-cy- cles or 65,000 total flight- hours, whichev- er occurs first. Do NDT inspections of Zone B for cracks in ac- cordance with Part 3. As an alternative, do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. Airplanes that have not done Zone B inspection in accordance with Revision 1 of this service bulletin. – Before 22,000 flight cycles or 95,000 flight hours, whichever occurs first. – Within 2,400 flight cycles or 12,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. -Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection Repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 3. Airplanes that have done NDT inspections of Zone B in accordance with Part 3 of Paragraph 3.B., Work Instructions given in Revi- sion 1 of this service bul- letin. As an alternative, do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. (a) Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 37 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 38 Group 2: Table 3: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and Less Than 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Within 6,000 flight-cycles or 30,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4. As an alternative, do NDT inspections of Zone B for cracks in accordance with Part 3. Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4 of Para- graph 3.B., Work Instruc- tions given in Revision 1 of this service bulletin. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 8,000 flight cycles or 44,000 flight hours, whichever occurs first, from the last inspec- tion. (a) -Before further flight.Do a repair in accordance with Part 3 or Part 4. Any crack found in Zone B. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 38 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 39 Group 2: Table 3: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and Less Than 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 3. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 4. (a) Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 3. As an alternative, in the unrepaired areas do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. No crack found with NDT inspections of Zone B in accordance with Part 3 or Any crack found and re- paired in accordance with Part 3. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 39 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 40 Group 2: Table 3: Horizontal Stabilizer - Zone B Inspection - Airplanes with Less Than 27,000 Total Flight-Cycles and Less Than 117,000 Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 3. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 4. (a) Within 6,000 flight-cycles or 30,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. As an alternative, in the unrepaired areas and ar- eas repaired only by hole oversizing, do NDT in- spections of Zone B for cracks in accordance with Part 3. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with Part 4. (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 3 - Zone B NDT Inspection, Part 4 - Zone B Open Hole NDT Inspection, Part 5 - Zone C Maraging or H-11 Steel Fastener Inspection, and Part 6 - Additional Zone C Maraging or H-11 Steel Fastener In- spection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the modification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 40 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 41 Group 1-3: Table 4: Horizontal Stabilizer - Zone B Inspection - Airplanes with 27,000 or More Total Flight-Cycles or 117,000 or More Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 90 days after the Revision 2 date of this service bulletin. Do NDT inspections of Zone B for cracks in ac- cordance with Part 3. Airplanes that have not done Zone B inspection in accordance with Revision 1 of this service bulletin. As an alternative, do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. -Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection Repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 3. Airplanes that have done NDT inspections of Zone B in accordance with Part 3 of Paragraph 3.B., Work Instructions given in Revi- sion 1 of this service bul- letin. As an alternative, do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. (a) -Whichever oc- curs first of the following: Within 6,000 flight-cycles or 30,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4. As an alternative, do NDT inspections of Zone B for cracks in accordance with Part 3. Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4 of Para- graph 3.B., Work Instruc- tions given in Revision 1 of this service bulletin. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 8,000 flight cycles or 44,000 flight hours, whichever occurs first, from the last inspec- tion. (a) Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 41 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 42 Group 1-3: Table 4: Horizontal Stabilizer - Zone B Inspection - Airplanes with 27,000 or More Total Flight-Cycles or 117,000 or More Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Do a repair in accordance with Part 3 or Part 4. Any crack found in Zone B. – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 3. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 4. (a) Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 3. As an alternative, in the unrepaired areas do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 4. No crack found with NDT inspections of Zone B in accordance with Part 3 or Any crack found and re- paired in accordance with Part 3. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 42 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 43 Group 1-3: Table 4: Horizontal Stabilizer - Zone B Inspection - Airplanes with 27,000 or More Total Flight-Cycles or 117,000 or More Total Flight-Hours Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 3. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 4. (a) Within 6,000 flight-cycles or 30,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. As an alternative, in the unrepaired areas and ar- eas repaired only by hole oversizing, do NDT in- spections of Zone B for cracks in accordance with Part 3. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with Part 4. (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 3 - Zone B NDT Inspection, Part 4 - Zone B Open Hole NDT Inspection, Part 5 - Zone C Maraging or H-11 Steel Fastener Inspection, and Part 6 - Additional Zone C Maraging or H-11 Steel Fastener In- spection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be installed prior to reaching the initial compli- ance threshold of Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the modification and to avoid costly repairs if any damage is found during the post-modification inspection. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 43 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 44 Group 4-6: Table 5: Horizontal Stabilizer - Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Before 15,000 total flight-cy- cles or 55,000 total flight- hours, whichev- er occurs first. Do an open hole HFEC inspection of Zone B for cracks in accordance with Part 4. Airplanes that have not done Zone B inspection in accordance with Revision 1 of this service bulletin. – Before 20,000 flight cycles or 85,000 flight hours, whichever occurs first. – Within 2,400 flight cycles or 12,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 44 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 45 Group 4-6: Table 5: Horizontal Stabilizer - Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Within 6,000 flight-cycles or 30,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4.(a) Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4 of Para- graph 3.B., Work Instruc- tions given in Revision 1 of this service bulletin. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 8,000 flight cycles or 44,000 flight hours, whichever occurs first, from the last inspec- tion. -Before further flight.Do a repair in accordance with Part 4. Any crack found in Zone B. 6,000 flight-cycles or 30,000 flight- hours, whichever occurs first.(a) Within 6,000 flight-cycles or 30,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with Part 4. (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 4 - Zone B Open Hole NDT Inspection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the mod- ification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 45 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 46 Group 7: Table 6: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before 16,000 total flight-cycles.Do a Detailed inspection of Zone A for cracks in accordance with Part 1. Airplanes that have not done Zone A inspection. As an alternative, do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. -Whichever oc- curs first of the following: Before 12,000 total flight-cy- cles or 44,000 total flight- hours, whichev- er occurs first. Do an open hole HFEC inspection of Zone B for cracks in accordance with Part 4. Airplanes that have not done Zone B inspection. – Within 2,400 flight cycles or 12,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Before 14,000 total flight cycles or 56,000 total flight hours, whichever occurs first. -Within 500 flight-cycles or 2,800 flight-hours from the last inspec- tion, whichever occurs first. Repeat the Detailed in- spection of Zone A for cracks in accordance with Part 1. Airplanes that have done a Detailed inspection of Zone A in accordance with Part 1. As an alternative, do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 46 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 47 Group 7: Table 6: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 1,350 flight-cycles or 7,500 flight-hours, whichever occurs first, from the last inspection. Repeat the surface HFEC inspection of Zone A for cracks in accordance with Part 2. Airplanes that have done a surface HFEC inspection of Zone A in accordance with Part 2. As an alternative, do a Detailed inspection of Zone A for cracks in ac- cordance with Part 1. -Whichever oc- curs first of the following: Within 3,000 flight-cycles or 18,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4.(a) Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 4,000 flight cycles or 22,000 flight hours, whichever occurs first, from the last inspec- tion. -Before further flight.Do an open hole HFEC inspection for cracks in accordance with Part 4 and do a repair in accor- dance with Part 1 or Part 2. Any crack found in Zone A. -Before further flight.Do a repair in accordance with Part 4. Any crack found in Zone B. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 47 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 48 Group 7: Table 6: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 500 flight-cy- cles or 2,800 flight-hours, whichever oc- curs first, from the last De- tailed inspec- tion. – 1,350 flight- cycles or 7,500 flight- hours, whichever oc- curs first, from the last sur- face HFEC in- spection. Within 500 flight-cycles or 2,800 flight-hours from the last inspec- tion, whichever occurs first. In the unrepaired areas, repeat the Detailed in- spection of Zone A for cracks in accordance with Part 1. As an alternative, in the unrepaired areas do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. No cracks found with De- tailed inspection of Zone A in accordance with Part 1 or Any crack found and re- paired in accordance with this service bulletin. – 500 flight-cy- cles or 2,800 flight-hours, whichever oc- curs first, from the last De- tailed inspec- tion. – 1,350 flight- cycles or 7,500 flight- hours, whichever oc- curs first, from the last sur- face HFEC in- spection. Within 1,350 flight-cycles or 7,500 flight-hours, whichever occurs first, from the last inspection. In the unrepaired areas, repeat the surface HFEC inspection of Zone A for cracks in accordance with Part 2. As an alternative, in the unrepaired areas do a Detailed inspection of Zone A for cracks in ac- cordance with Part 1. No cracks found with sur- face HFEC inspection of Zone A in accordance with Part 2 or Any crack found and re- paired in accordance with this service bulletin. 3,000 flight-cycles or 18,000 flight- hours, whichever occurs first.(a) Within 3,000 flight-cycles or 18,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with this service bulletin. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 48 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 49 Group 7: Table 6: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 4 - Zone B Open Hole NDT Inspection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the mod- ification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Group 8: Table 7: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before 18,000 total flight-cycles.Do a Detailed inspection of Zone A for cracks in accordance with Part 1. Airplanes that have not done Zone A inspection. As an alternative, do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. -Whichever oc- curs first of the following: Before 14,000 total flight-cy- cles or 55,000 total flight- hours, whichev- er occurs first. Do an open hole HFEC inspection of Zone B for cracks in accordance with Part 4. Airplanes that have not done Zone B inspection. – Within 2,400 flight cycles or 12,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Before 16,000 total flight cycles or 74,000 total flight hours, whichever occurs first. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 49 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 50 Group 8: Table 7: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Within 500 flight-cycles or 2,800 flight-hours from the last inspec- tion, whichever occurs first. Repeat the Detailed in- spection of Zone A for cracks in accordance with Part 1. Airplanes that have done a Detailed inspection of Zone A in accordance with Part 1. As an alternative, do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. -Within 1,350 flight-cycles or 7,500 flight-hours, whichever occurs first, from the last inspection. Repeat the surface HFEC inspection of Zone A for cracks in accordance with Part 2. Airplanes that have done a surface HFEC inspection of Zone A in accordance with Part 2. As an alternative, do a Detailed inspection of Zone A for cracks in ac- cordance with Part 1. -Whichever oc- curs first of the following: Within 3,000 flight-cycles or 18,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4.(a) Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 4,000 flight cycles or 22,000 flight hours, whichever occurs first, from the last inspec- tion. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 50 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 51 Group 8: Table 7: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before further flight.Do an open hole HFEC inspection for cracks in accordance with Part 4 and do a repair in accor- dance with Part 1 or Part 2. Any crack found in Zone A. -Before further flight.Do a repair in accordance with Part 4. Any crack found in Zone B. – 500 flight-cy- cles or 2,800 flight-hours, whichever oc- curs first, from the last De- tailed inspec- tion. – 1,350 flight- cycles or 7,500 flight- hours, whichever oc- curs first, from the last sur- face HFEC in- spection. Within 500 flight-cycles or 2,800 flight-hours from the last inspec- tion, whichever occurs first. In the unrepaired areas, repeat the Detailed in- spection of Zone A for cracks in accordance with Part 1. As an alternative, in the unrepaired areas do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. No cracks found with De- tailed inspection of Zone A in accordance with Part 1 or Any crack found and re- paired in accordance with this service bulletin. – 500 flight-cy- cles or 2,800 flight-hours, whichever oc- curs first, from the last De- tailed inspec- tion. – 1,350 flight- cycles or 7,500 flight- hours, whichever oc- curs first, from the last sur- face HFEC in- spection. Within 1,350 flight-cycles or 7,500 flight-hours, whichever occurs first, from the last inspection. In the unrepaired areas, repeat the surface HFEC inspection of Zone A for cracks in accordance with Part 2. As an alternative, in the unrepaired areas do a Detailed inspection of Zone A for cracks in ac- cordance with Part 1. No cracks found with sur- face HFEC inspection of Zone A in accordance with Part 2 or Any crack found and re- paired in accordance with this service bulletin. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 51 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 52 Group 8: Table 7: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition 3,000 flight-cycles or 18,000 flight- hours, whichever occurs first.(a) Within 3,000 flight-cycles or 18,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with this service bulletin. (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 4 - Zone B Open Hole NDT Inspection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the mod- ification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Group 9: Table 8: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Before 15,000 total flight-cycles.Do a Detailed inspection of Zone A for cracks in accordance with Part 1. Airplanes that have not done Zone A inspection. As an alternative, do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 52 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 53 Group 9: Table 8: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Before 12,000 total flight-cy- cles or 55,000 total flight- hours, whichev- er occurs first. Do an open hole HFEC inspection of Zone B for cracks in accordance with Part 4. Airplanes that have not done Zone B inspection. – Within 2,400 flight cycles or 12,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Before 13,000 total flight cycles or 72,000 total flight hours, whichever occurs first. -Within 500 flight-cycles or 2,800 flight-hours from the last inspec- tion, whichever occurs first. Repeat the Detailed in- spection of Zone A for cracks in accordance with Part 1. Airplanes that have done a Detailed inspection of Zone A in accordance with Part 1. As an alternative, do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. -Within 1,350 flight-cycles or 7,500 flight-hours, whichever occurs first, from the last inspection. Repeat the surface HFEC inspection of Zone A for cracks in accordance with Part 2. Airplanes that have done a surface HFEC inspection of Zone A in accordance with Part 2. As an alternative, do a Detailed inspection of Zone A for cracks in ac- cordance with Part 1. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 53 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 54 Group 9: Table 8: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition -Whichever oc- curs first of the following: Within 3,000 flight-cycles or 18,000 flight- hours, whichev- er occurs first, from the last in- spection. Repeat the open hole HFEC inspection of Zone B for cracks in accor- dance with Part 4.(a) Airplanes that have done an open hole HFEC inspec- tion of Zone B in accor- dance with Part 4. – Within 2,400 flight cycles or 13,000 flight hours, whichever occurs first, after the Revision 2 date of this service bul- letin. – Within 4,000 flight cycles or 22,000 flight hours, whichever occurs first, from the last inspec- tion. -Before further flight.Do an open hole HFEC inspection for cracks in accordance with Part 4 and do a repair in accor- dance with Part 1 or Part 2. Any crack found in Zone A. -Before further flight.Do a repair in accordance with Part 4. Any crack found in Zone B. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 54 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 55 Group 9: Table 8: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition – 500 flight-cy- cles or 2,800 flight-hours, whichever oc- curs first, from the last De- tailed inspec- tion. – 1,350 flight- cycles or 7,500 flight- hours, whichever oc- curs first, from the last sur- face HFEC in- spection. Within 500 flight-cycles or 2,800 flight-hours from the last inspec- tion, whichever occurs first. In the unrepaired areas, repeat the Detailed in- spection of Zone A for cracks in accordance with Part 1. As an alternative, in the unrepaired areas do a surface HFEC inspection of Zone A for cracks in accordance with Part 2. No cracks found with De- tailed inspection of Zone A in accordance with Part 1 or Any crack found and re- paired in accordance with this service bulletin. – 500 flight-cy- cles or 2,800 flight-hours, whichever oc- curs first, from the last De- tailed inspec- tion. – 1,350 flight- cycles or 7,500 flight- hours, whichever oc- curs first, from the last sur- face HFEC in- spection. Within 1,350 flight-cycles or 7,500 flight-hours, whichever occurs first, from the last inspection. In the unrepaired areas, repeat the surface HFEC inspection of Zone A for cracks in accordance with Part 2. As an alternative, in the unrepaired areas do a Detailed inspection of Zone A for cracks in ac- cordance with Part 1. No cracks found with sur- face HFEC inspection of Zone A in accordance with Part 2 or Any crack found and re- paired in accordance with this service bulletin. 3,000 flight-cycles or 18,000 flight- hours, whichever occurs first.(a) Within 3,000 flight-cycles or 18,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 4. No crack found with open hole HFEC inspection of Zone B in accordance with Part 4 or Any crack found and re- paired in accordance with this service bulletin. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 55 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 56 Group 9: Table 8: Horizontal Stabilizer - Zone A and Zone B Inspection Repeat Interval (Not to Exceed) Compliance Time (Whichever Occurs Later) ActionCondition (a) Accomplishment of optional Part 7 - Zone B Modification is terminating action to the repeat inspections for Part 4 - Zone B Open Hole NDT Inspection given in Paragraph 3.B., Work Instructions. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the mod- ification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Group 1-3: Table 9: Additional Zone C Maraging or H-11 Steel Fastener Inspection Repeat Interval (Not to Exceed) Compliance TimeActionCondition -Within 36 months after the Revi- sion 2 date of this service bul- letin.(a) Do additional inspection of the indicated fasteners to determine if the bolt is magnetic in accordance with Part 6. All airplanes. --No further action is neces- sary at that fastener loca- tion. Bolt is not magnetic. -Before further flight.Do an ultrasonic inspec- tion to determine if the magnetic bolt is cracked or fractured in accor- dance with Part 6.(a) Bolt is magnetic. -Before further flight.Do an open hole HFEC inspection of Zone B for cracks, repair any crack- ing, and replace the fas- tener in accordance with Part 4. Bolt is cracked or fractured. Within 18 months.(a) Within 18 months from the last in- spection. Repeat the ultrasonic in- spection to determine if the magnetic bolt is cracked or fractured in accordance with Part 6. Bolt is not cracked and fractured. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 56 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 57 Group 1-3: Table 9: Additional Zone C Maraging or H-11 Steel Fastener Inspection Repeat Interval (Not to Exceed) Compliance TimeActionCondition (a) Accomplishment of Part 4 - Zone B Open Hole NDT Inspection and fastener replacement or optional Part 7 - Zone B Modification is terminating action for Zone C inspection. Boeing recommends that Part 7 - Zone B Modification not be accomplished prior to reaching the initial compliance threshold of Part 3 - Zone B NDT Inspection or Part 4 - Zone B Open Hole NDT Inspection to maximize the benefit of the modification and reduce the number of post-modification repeat inspections prior to reaching 35,000 total flight cycles. 35,000 total flight cycles is the Limit of Validity (LOV) for the affected airplanes. Group 1-3: Table 10: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition -Within 15,000 flight-cycles or 55,000 flight-hours, whichever oc- curs first, after the modification. Do NDT inspections of Zone B for cracks in ac- cordance with Part 8. Airplanes with Zone B modification previously ac- complished in accordance with Part 7 of Paragraph 3.B., Work Instructions. As an alternative, do an open hole HFEC inspec- tions of Zone B for cracks in accordance with Part 8. -Before further flight.Do a repair in accordance with Part 8. Any crack found. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 57 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 58 Group 1-3: Table 10: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 8. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 8. Within 2,400 flight-cycles or 13,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, repeat the NDT inspec- tions of Zone B for cracks in accordance with Part 8. As an alternative, in the unrepaired areas do an open hole HFEC inspec- tion of Zone B for cracks in accordance with Part 8. No crack found with NDT inspections of Zone B in accordance with Part 8 or Any crack found and re- paired in accordance Part 8. Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 58 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 59 Group 1-3: Table 10: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition – 2,400 flight- cycles or 13,000 flight- hours, whichever oc- curs first, from the last NDT inspections of Zone B in ac- cordance with Part 8. – 6,000 flight- cycles or 30,000 flight- hours, whichever oc- curs first, from the last open hole HFEC in- spection of Zone B in ac- cordance with Part 8. Within 6,000 flight-cycles or 30,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas, and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 8. As an alternative, in the unrepaired areas and ar- eas repaired only by hole oversizing, do NDT in- spections of Zone B for cracks in accordance with Part 8. No crack found with open hole HFEC inspection of Zone B in accordance with Part 8 or Any crack found and re- paired in accordance with Part 8. Group 4-6: Table 11: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition -Within 15,000 flight-cycles or 55,000 flight-hours, whichever oc- curs first, after accomplishment of the modification. Do an open hole HFEC inspections of Zone B for cracks in accordance with Part 8. Airplanes with Zone B modification previously ac- complished in accordance with Part 7 of Paragraph 3.B., Work Instructions. -Before further flight.Do a repair in accordance with Part 8. Any crack found Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 59 of 249 BOEING SERVICE BULLETIN 747-55A2050 ### Page 60 Group 4-6: Table 11: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition 6,000 flight-cycles or 30,000 flight- hours, whichever occurs first. Within 6,000 flight-cycles or 30,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 8. No crack found with open hole HFEC inspection of Zone B in accordance with Part 8 or Any crack found and re- paired in accordance with Part 8. Group 7: Table 12: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition -Within 12,000 flight-cycles or 44,000 flight-hours, whichever oc- curs first, after accomplishment of the modification. Do an open hole HFEC inspections of Zone B for cracks in accordance with Part 8. Airplanes with Zone B modification previously ac- complished in accordance with Part 7 of Paragraph 3.B., Work Instructions. -Before further flight.Do a repair in accordance with Part 8. Any crack found 3,000 flight-cycles or 18,000 flight- hours, whichever occurs first. Within 3,000 flight-cycles or 18,000 flight-hours, whichever oc- curs first, from the last inspection. In the unrepaired areas and areas repaired only by hole oversizing, repeat the open hole HFEC in- spection of Zone B for cracks in accordance with Part 8. No crack found with open hole HFEC inspection of Zone B in accordance with Part 8 or Any crack found and re- paired in accordance with Part 8. Group 8: Table 13: Horizontal Stabilizer - Zone B Post-Modification Inspections Repeat Interval (Not to Exceed) Compliance TimeActionCondition -Within 14,000 flight-cycles or 55,000 flight-hours, whichever oc- curs first, after accomplishment of the modification. Do an open hole HFEC inspections of Zone B for cracks in accordance with Part 8. Airplanes with Zone B modification previously ac- complished in accordance with Part 7 of Paragraph 3.B., Work Instructions. -Before further flight.Do a repair in accordance with Part 8. Any crack found Export Controlled ECCN: 9E991 - BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: February 28, 2002 747-55A2050Revision 2: January 23, 2015 60 of 249 BOEING SERVICE BULLETIN 747-55A2050 The text continues at https://openairdocs.org/service-documents/boeing/747-55a2050/file/ba9aa00c91da.md?from=61 --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain, except the copies of manufacturers’ service documents, which belong to their rights holders.