2003 structures

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2003 structures

  1. 1. 2003 STRUCTURES CONFERENCE SERVICE ENGINEERING COMMERCIAL AVIATION SERVICES The data contained herein and included herewith are the property of The Boeing Company and are to be used by the recipient solely for the purposes for which theyare furnished. Recipient agrees not to use this information to make of sell any part or to disclose these data to any other parties without the expressed written consent of The Boeing Company. SE-ACM-4-1-2003 April 2003
  2. 2. ContentsOverview ………………………………………………………………………………………….. ivGlossary …………………………………………………………………………………………… vAging Airplane Maintenance Program Developments .......................................................... 1Damage Tolerance Programs Update.................................................................................. 2Widespread Fatigue Damage (WFD) ................................................................................... 3Damage Removal During Structural Repairs........................................................................ 4Charging for Engineering Services....................................................................................... 5Structural Health Management (SHM) ................................................................................. 6737 Lap Joint........................................................................................................................ 7Nondestructive Testing (NDT) Personnel Training and Certification .................................... 8737 Classic Fuselage Issues................................................................................................ 9737 Aft Pressure Bulkhead Issues ..................................................................................... 10737 BS 178 Bulkhead Issues ............................................................................................. 11737 Classic Elevator Tab Vibration .................................................................................... 12737NG Elevator Tab Modification Program ........................................................................ 13Flap Failure Mitigation ........................................................................................................ 14Damage Reporting and Repair Approval............................................................................ 15New SRM General Skin Repair .......................................................................................... 16Visual Inspection ................................................................................................................ 17Metalbond Repair Technology Improvements .................................................................... 18Materials and Processes .................................................................................................... 19Improving Window Service Life .......................................................................................... 20Maintaining High Strength Steel ......................................................................................... 21Structural Repair Training................................................................................................... 22SE-ACM-4-1-2003 iii
  3. 3. OverviewMaintaining airworthiness is the primary goal of all airplane maintenance programs. Havinga good understanding of structural design, repair and maintenance requirements is animportant aspect of a successful maintenance program.This conference series is intended to raise the participant’s level of structural awarenessand provide an opportunity to discuss in-service structural issues that may impact operatorsand the airframe manufacturers. The presentations are starting points for participants to askquestions and share experiences related to the current topics.Discussions will update the Aging Airplane Program activities, and the new FAA InterimFinal Rule and associated Advisory Circulars published in December 2002. The newregulatory action is the result of activities called for by the “Aging Aircraft Safety Act of1991”. Another important item is the newly developed Widespread Fatigue Damageprogram that is the most recent activity in the FAA’s Aging Airplane program. How to applythe updated damage tolerance requirements of the repair assessment and SSID programswhen a repair or alteration is made to airplane structure is another important discussionitem. Other topics will discuss the importance of removing all damage when performingrepairs, recent changes in body skin lap joint mandatory repair and modification activitiesrelated to 737 airplanes, and ongoing activities to improve SRM skin repair information tohelp airlines make more repairs without Boeing assistance.This conference also includes a demonstration and presentation outlining new activities todevelop structural health monitoring systems for future applications. Adopting thistechnology will require the aviation industry to work together to define new ways to addressstructural maintenance needs and assumptions as new technology is introduced that cansimplify routine maintenance inspection tasks. As the industry continues to progress, non-destructive inspection techniques and the associated training for inspectors will continue tobe an item of importanceThe closing presentations will also address recent technology developments that will beadded to the SRMs to improve the repair of metalbond parts containing aluminumhoneycomb, provide updates on current materials and processes issues, discuss new MSG-3 visual inspection terms, and methods to reduce schedule delays related to flight deck andpassenger cabin widow damage.The attached CD-ROM contains copies of the presentation material.Operators requiring more information or assistance are encouraged to contact Boeingthrough established communication channels and Boeing Field Service representatives.iv SE-ACM-4-1-2003
  4. 4. GlossaryThe following are definitions of frequently used acronyms and many of them appear in this document.737 Classic 737-100/200/300/400/500737 NG 737-600/700/800/900 DFR Detail Fatigue RatingAASR Aging Airplane Safety Rule DMS Douglas Material SpecificationAATF Airworthiness Assurance Task Force DPS Douglas Process SpecificationAAWG Airworthiness Assurance Working Group DSO Design Service ObjectiveAC Advisory Circular DTR Damage Tolerance RatingACO Aircraft Certification Office F FahrenheitAD Airworthiness Directive f/c flight cyclesAEG Aircraft Evaluation Group FAA Federal Aviation AdministrationAHM Airplane Health Managment FAR Federal Aviation RegulationAmdt Amendment FFMP Flap Failure Mitigation ProgramAMOC Alternative Method of Compliance Flts FlightsAOG Airplane on Ground FOD Foreign Object DamageAPU Auxiliary Power Unit FSBTI Flight Safety Boeing TrainingARAC Aviation Rulemaking Advisory International (Now called Alteon) Committee FTD Fleet Team DigestASI Aviation Safety Inspector ftg fittingASNT American Society for Nondestructive FWD Forward Testing GPS Global Positioning SystemATA Air Transport Association GVI General Visual InspectionATSRAC Aging Transport Systems Rulemaking HFEC High Frequency Eddy Current Advisory CommitteeBAC Boeing part or process specification HMC Heavy Maintenance CheckBBL Body Buttock Line IACS International Annealed Copper StandardBCAG Boeing Commercial Airplane Group ISIP Integrated Structural Inspection ProgramBMS Boeing Material Specification ISP Inspection Start PointBOECOM Boeing Communication Messaging IVHM Integrated Vehicle Health Maintenance System ksi Thousand pounds per square inchBS Body Station L/P Line PositionCAA Civil Aviation Authority LBL Left Buttock LineCACRC Commercial Aircraft Composite Repair LCD Liquid Crystal Display CommitteeCd Cadmium (plating) LFEC Low Frequency Eddy CurrentCFRP Carbon Fiber Reinforced Plastic LH Left HandCIC Corrosion Inhibiting Compound max maximumCMM Component Maintenance Manual MDC McDonnell Douglas published documentCMR Certification Maintenance Requirement MED Multi Element DamageCPC Corrosion Preventative Compound MFEC Medium Frequency Eddy CurrentCPCP Corrosion Prevention and Control min minimum Program MLG Main Landing GearCPM Corrosion Prevention Manual mm millimeterCRES Corrosion Resistant Steel MM Maintenance ManualD6- Boeing published document MOI Magneto Optic ImagingDER Designated Engineering Representative MPD Maintenance Planning DataDET Detailed (Inspection) MRB Maintenance Review BoardSE-ACM-4-1-2003 v
  5. 5. Glossary (continued)The following are definitions of frequently used acronyms and many of them appear in this documentMSD Multiple Site Damage STA StationMSG Maintenance Steering Group STC Supplemental Type CertificateN/A Not applicable STG Structures Task GroupNDI Nondestructive Inspection SUD Stretched Upper DeckNDT Nondestructive Testing SURV Surveillance (Inspection)NLG Nose Landing Gear SWG Structures Working GroupNPRM Notice of Proposed Rule Making TBD To Be DeterminedNSC Notice of Status Change TE Trailing Edge National Transportation Safety USD United States DollarNTSB Board WFD Widespread Fatigue DamageOAMP On Airplane Maintenance Program WISC Working Industry Steering CommitteeOEM Original Equipment Manufacturer WL Water LineP/N Part NumberPAA Phosphoric Acid AnodizePSE Principal Structural ElementRAG Repair Assessment GuidelinesRAP Repair Assessment ProgramRBL Right Buttock LineRev RevisionRH Right HandRRC Rapid Response CenterSAE Society of Automotive EngineersSAR Service Action RequirementsSATCOM Satellite CommunicationsSB (or S/B) Service BulletinSDI Special Detailed InspectionSDR Service Difficulty ReportingSFAR Special Federal Aviation RegulationSHM Structural Health Maintenancesht sheetSID Supplemental Inspection DocumentSIIA Structural Item Interim AdvisorySL Service LetterSMP Structural Modification Point Standard Overhaul OperatingSOPM ProceduresSOW Statement of WorkSRM Structural Repair ManualSRP Structural Related ProblemSSI Structural Significant Item Supplemental Structural InspectionSSID Document Supplemental Structural InspectionSSIP Program (or SIP)vi SE-ACM-4-1-2003
  6. 6. SectionsAging Airplane Maintenance Program Developments . . . . . . . . . . . . . . . . . . . . . . 1Damage Tolerance Programs Update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Widespread Fatigue Damage (WFD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Damage Removal During Structural Repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Charging for Engineering Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Structural Health Management (SHM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6737 Lap Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Nondestructive Testing (NDT) Personnel Training and Certification . . . . . . . . . . . . . . . 8737 Classic Fuselage Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9737 Aft Pressure Bulkhead Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10737 BS 178 Bulkhead Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11737 Classic Elevator Tab Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12737NG Elevator Tab Modification Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Flap Failure Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Damage Reporting and Repair Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15New SRM General Skin Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Metalbond Repair Technology Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Materials and Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Improving Window Service Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Maintaining High Strength Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Structural Repair Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Maintenance Program 1. Aging Airplane Developments
  7. 7. 1. Aging Airplane Maintenance Program Developments Objective To provide inform ation regarding the latest program developm ents to ensure the continuing structural airworthiness of airplanes as they age 2 Contents • Background • Recent Developm ents • W idespread Fatigue Dam age • Aging Airplane Safety Rule • CPCP NPRM • CPCP Reporting AMOC 3 The transport airplane fleet has been in continuous operation over the past 45 Aging Airplane Concerns years, accumulating hours and cycles in ever increasing numbers. As the fleet ages, it has become apparent that the • As airplanes age effects of long term service, primarily from fatigue and corrosion, increase • Potential for fatigue cracking increases with continuous usage. The • Corrosion m ay becom e m ore widespread and simultaneous exposure of a structure to corrosion and fatigue increases the risk significantly degrade fatigue performance of degradation in structural integrity. As • Tw o or m ore types of dam age in an area can structural problems tend to be degrade fail-safe or dam age tolerance capability addressed individually, it is a concern that both types of damage to a structure be addressed at the same time. 4SE-ACM-4-1-2003 1-1
  8. 8. 1. Aging Airplane Maintenance Program Developments The concerns regarding the aging fleet have arisen as a result of the operation Aging Fleet Issues of a number of airplanes beyond the original design service objective (DSO). As shown by the number of high-time • Econom ic and m arket conditions result in airplanes still in service, the useful operation of airplanes longer than anticipated economic life of transport category aircraft has proven to be greater than • Damage on high tim e airplanes highlighted aging the original design objective. However, fleet structural concerns as experience has shown, with incidents • Horizontal stabilizer occurring on two high-time airplanes, the condition of the structures as the • Fuselage skin airframe ages is of concern. Structural maintenance must now also address the • Maintenance program s for an aging fleet must effects of aging as well as the normal, address effects of fatigue and corrosion during routine inspection and repair tasks. long term operations 5 For airplanes certified prior to the adoption of Amendment 45 to FAR 25, Structural Maintenance Program s the aging airplane programs, in conjunction with the original maintenance planning data document, • Maintenance Planning Data provide a comprehensive structures • Aging Airplane Program s maintenance program. • Supplem ental Structural Inspections • Corrosion Prevention and Control Program • M andatory m odifications and inspections • Repair Assessm ent Program • W idespread Fatigue Dam age Program (TBD) • Service Bulletins • Other m andated actions 6 There have been several recent developments with regard to the various Aging Airplane Program Developm ents aspects of aging airplane structures. These involve new programs, i.e., Widespread Fatigue Damage and the • W idespread Fatigue Dam age Aging Airplane Safety Rule and changes to existing programs, i.e., the Corrosion • Aging Airplane Safety Rule Prevention and Control Program, previously implemented under the • CPCP NPRM auspices of the Aging Airplane Safety Act of 1991. • CPCP Reporting AMOC 71-2 SE-ACM-4-1-2003
  9. 9. 1. Aging Airplane Maintenance Program Developments The issue of Widespread Fatigue Damage is the sixth initiative originally W idespread Fatigue Damage (W FD) identified by the Airworthiness Assurance Task Force (AATF), now the Airworthiness Assurance Working • W FD is structural damage which is characterized by: Group (AAWG), as a result of a 1988 accident which raised the issue of aging • The sim ultaneous presence of cracks at multiple airplane structures. There has been an structural details, and industry wide approach to defining and • Have sufficient size and density such that the characterizing widespread fatigue and structure will no longer m eet its dam age the steps needed to reduce the risk of tolerance requirement this type of damage occurring. One byproduct of this effort has been an • There is a point in airplane operation where the risk understanding that there is a point in the of uncertainties in structural perform ance and the operation of an airplane where the probable development of W FD increases maintenance program may no longer protect the airplane from the increased risk of widespread fatigue damage. 8 One concept, which has come out of the research and development effort into Lim it of the M aintenance Program widespread fatigue, is that of a Limit of Validity (LOV) of an airplane’s maintenance program. This is a point in • Concept of Limit of Validity (LOV) an airplane’s operational life beyond which there may be insufficient • Threshold beyond which the airplane structural substantiation data to support m aintenance program is not considered valid continued operation due to fatigue • W FD requirem ents to be provided in m odel considerations. In other words, the specific documents inspections in the maintenance program may not detect fatigue damage before • LOV the strength levels are reduced below the regulatory requirements. • Inspections The issue of WFD for each model • Modifications airplane will be addressed in a document that will contain the LOV, and any modifications and inspections required to alleviate the concern over 9 WFD. The FAA has recently published an Interim Final Rule and three associated Aging Airplane Safety Rule (AASR) Advisory Circulars defining the requirements for damaged tolerance based maintenance actions for transport • Interim Final Rule and ACs published in Dec 2002 are result of activities called for by the “Aging airplanes operated under FAR Parts Aircraft Safety Act of 1991” 121, 129 and 135 (scheduled operations only). This rule, to be effective • Rule result of com m ents received from two December 8, 2003, was a result of two previous NPRM publications previous NPRMs, the latest being • Further comm ents requested because 1999 issued in 1999. The latest version of the NPRM w as significantly m odified rule has been greatly modified over the previous versions and now covers areas • Com m ent period extended to 5 May 2003 of transport category airplanes not • Airplanes operated under FARs 121, 129, and 135 previously addressed. The FAA has extended the original • Effective 8 Dec 2003 comment period for this rule from the original closing date of February 4th to May 5th, 2003. 10SE-ACM-4-1-2003 1-3
  10. 10. 1. Aging Airplane Maintenance Program Developments There are two paragraphs to the AASR requirements. The first, Paragraph 1, Rule Requirem ents, Paragraph 1 contains two parts, an aging airplane records review and an on-site inspection of the airplane. The rule requires a • Records Review s periodic review of an operator’s • Periodic review of m aintenance records based maintenance records as called out in on airplane age FARs 121.368, 129.33 and 135.422. These FARs list the records information • Inspections of airplanes that is required to be available at the time of the review. In addition, each • Focus on existing aging aircraft requirem ents airplane will have to undergo a physical inspection of the airframe structure at • Specified in FARs 121.368, 129.33 and 135.422 the time of the records review. 11 The schedule for the accomplishment of the maintenance record review and the Records Review – Part 1 on-airplane inspection will depend upon the age of the airplane on 08 December 2003; the date the rule becomes • On 8 Dec 2003, for airplanes effective. At that time, operators with • Exceeding 24 years in service, 1 st records airplanes over 24 years of age will have review m ust occur before 5 Dec 2007 4 years to complete the records review. For airplanes between 14 and 24 years • Exceeding 14 years in service but less than of age on that date, the records review 24 years, 1 st records review m ust occur must be accomplished with 5 years. If before 4 Dec 2008 an airplane is less than 14 years old, the records review must be performed by • Less than 14 years in service, no later than the start of the airplane’s 20th year in 5 years after the start of 15th year in service service. • For all airplanes, records review will be Repeat records reviews must be done repeated every 7 years thereafter every 7 years thereafter. 12 The second part of the records review involves an on-airplane inspection of the Records Review - Part 2 airframe structure. This inspection is to be accomplished in conjunction with the review of the maintenance records. The • Physical inspection of the airplane either by FAA FAA will require at least 60 days notice Adm inistrator or Designee of when the airplane will be available for the inspection. A representative of the • Accom plished in conjunction with the FAA Administrator, such as an Aviation m aintenance records review Safety Inspector (ASI), or an FAA Designee, will perform the inspection. • Adm inistrator will require notification 60 days The FAA Designee will be a Designated prior to date that airplane and its records will be Airworthiness Representative (DAR). available for inspection 131-4 SE-ACM-4-1-2003
  11. 11. 1. Aging Airplane Maintenance Program Developments The second paragraph of the AASR specifies the requirement for the Rule Requirem ents, Paragraph 2 maintenance program for an airplane to include damage tolerance based inspections and procedures. The • Supplem ental Inspections specifics of this part of the AASR are • Require a dam age tolerance based spelled out in FARs 121.370a, 129.16 m aintenance program by 5 Dec 2007 and 135.168 (scheduled operations only). • Affects airplanes operated under FAR 121, 129, and 135 14 The damage tolerance based inspection program required by this rule which Supplemental Inspection must be incorporated in an operator’s maintenance program is intended to maintain the continued airworthiness of • A dam age tolerance based program m ust be in both the original airframe and those place and operating with three elem ents which: structures altered by repairs or • Proactively inspects for dam age to the as modifications. Any repairs or delivered structure to m aintain continued modifications made to an airplane must airworthiness* have damage tolerance based • M aintains continued airworthiness of a inspections included in the existing repaired airplane maintenance program. • Establishes a new or revised program for areas of the airplane that undergo m ajor m odification * Repairs to areas affected by the SSID or ALI require damage tolerance based maintenance program s 15 In one form or another, the maintenance programs for all Boeing model airplanes Supplemental Inspections include damage tolerance based inspection requirements. For the pre- amendment 45 certified airplanes, these • For all Boeing products, programs will exist are contained in the various aging • Pre-am endm ent 45 airplanes airplane programs mandated by airworthiness directives or operational • Service Action Requirem ents rules. The post-amendment 45 airplanes • CPCP contain these requirements as a result of their certification basis. • SSIP • Repair Assessm ent Program 0 Fuselage pressure boundary • Post Am endm ent 45 airplanes • Certification basis requirem ent 16SE-ACM-4-1-2003 1-5
  12. 12. 1. Aging Airplane Maintenance Program Developments A number of operators commented that the existing aging airplane programs Com m ents on Rule should be sufficient to comply with the intent of the rule. The FAA partially agreed, but stated that these programs • Operators com m ented that existing Aging Airplane only satisfy part of the requirements of Program s provide m eans of com pliance the final rule. The FAA’s position was that the SSIPs only address certain • FAA has interpreted additional issues and portions of an airplanes structure while responses that operators “m ust establish the damage-tolerance-based SSIPs dam age-tolerance-based SSIPs or service- specified by the rule address the entire history-based SSIPs, as applicable, for m ajor primary structure of an airplane, repairs, m ajor alterations, and m odifications to including the baseline structure, and structures not affected by the repair major repairs, major alterations, and assessment program , such as fuselage fram es modifications to baseline structure. For and longerons, and wing and em pennage that reason, the FAA feels that the structures” SSIPs must go beyond the current aging airplane programs to encompass the entire airframe. 17 The FAA expressed concern that a number of derivatives of existing Other FAA Issues airplanes are not now covered by a supplemental inspection program. They are also concerned by the fact that there • SSID program s on som e 737, 747 m odels and are a number of major repairs or MD-80 have yet to be mandated modifications that may now require an assessment to determine any damage • Unknow n number of “m ajor” repairs and tolerance based inspection m odifications that may now require dam age requirements under this rule. These tolerance based inspections include service bulletin and STC repairs • Service Bulletins and modifications. • STCs 181-6 SE-ACM-4-1-2003
  13. 13. 1. Aging Airplane Maintenance Program Developments The FAA held a public meeting to review the activities of an FAA team that was FAA SSID AD Standardization Review chartered to gain knowledge of the damage tolerance based inspection aspects of the Aging Aircraft Programs • Public m eeting on 27 Feb 2003 and to make recommendations • FAA SSID Team m ade 8 recom m endations, regarding how the FAA should handle including the Supplemental Structural Inspection Document (SSID) Airworthiness 0 Assessm ent compliance time to 18 months Directives (ADs). The team addressed the ADs currently existing for the 727, 0 Three step assessm ent process 737, DC-8, DC-9 and the DC-10 airplanes. The result of the review was • Relationship betw een SSID ADs and AASR eight recommendations to standardize • Requirem ents for repairs, alterations and the SSID ADs, including extending the m odifications under these regulations assessment time for repairs, alterations and modifications to 18 months. 0 Have dam age tolerance based inspections The meeting also addressed the relationship between the SSID ADs and 19 the AASR as both regulations require damage tolerance inspections for repairs, alterations and modifications. For a copy of the FAA SSID Team report, see the following website: http://www1.faa.gov/certification/aircraft/ agingaircraft/ssid/ssid/index.htm It is felt that the post-amendment 45 Boeing models will meet the intent of the Effect on Boeing Models – Post-Am dt 45 AASR. These models were certified under damage tolerance rules and have damage tolerance based inspections in • 757, 767, 777, 737-700C/900, MD-11, MD-90, 717 their maintenance programs. • Certification basis fulfills intent of the AASR for dam age tolerance based m aintenance program s 0 All have SSIPs in form of Airw orthiness Lim itation Instructions (certain models have ADs for early L/Ps) 0 All require dam age tolerance based repairs and m odifications 20SE-ACM-4-1-2003 1-7
  14. 14. 1. Aging Airplane Maintenance Program Developments It is the FAA’s position that meeting the requirements of FARs 121.370, 125.248 Effect on Boeing Models – Pre-Am dt 45 and 129.32 is an acceptable means of compliance with the final rule only to the extent that these requirements address • 707, 720, 727, 737-100 through –800*, 747-100 repairs to the fuselage pressure through -400, DC-8, DC-9, MD-80, DC-10 boundary for the noted airplanes. The • Required by FARs to have a RAP FAA states that operators will have to accomplish additional work to fully 0 Applicable only to fuselage pressure boundary comply with this rule. Damage tolerance based SSIPs will have to be • Rule w ill require additional damage tolerance established for major repairs, major based inspection program for structures not alterations, and modifications to addressed by RAP structures not affected by the repair assessment program, such as fuselage frames and longerons, and wing and empennage structures. * Except 737-700C 21 Reporting of Level 2 and 3 corrosion occurrences was originally required to CPCP Reporting AM OC validate baseline CPCP programs. However, the baseline program has not been changed as a result of CPCP • CPCP ADs required quarterly reporting of Level 2 reports. The CPCP is operator adjusted and follow -up of Level 3 reporting on a quarterly to meet specific operator program basis needs. Operators are also required to report corrosion occurrences of • Corrosion reporting also required per FAR 121.703 corrosion per FAR 121.703(a)(15). Operators’ felt reporting to Boeing was • Boeing proposed that reporting corrosion per FAR duplicate reporting requirements for the 121.703 would fulfill the AD reporting requirem ents same occurrence. Reporting Levels 2 and 3 instances of • FAA concurred and issued an AMOC corrosion per FAR 121.703(a)(15) is • Separate reporting to Boeing no longer required now an AMOC to paragraph D of ADs 90-25-07, 90-25-03, 90-25-01 and 90- 25-05. A copy of this AMOC is included as Addendum 1-1. 221-8 SE-ACM-4-1-2003
  15. 15. 1. Aging Airplane Maintenance Program Developments The FAA has released a CPCP NPRM, Notice No. 02-16, Docket No. FAA- CPCP NPRM 2002-13458, which is applicable to airplanes operated under FARs 121, 129 or 135 (scheduled service only). • Released in Federal Register 3 Oct 2002 This proposal would impose • Requires im plem entation of an FAA approved requirements to prevent the spreading CPCP w ithin 2 years of rule effective date of corrosion in all other airplanes operated under part 121, all other U.S.- • Applicable to FAR 121, 129 and 135 operators registered multiengine airplanes operated under part 129, and all other • Baseline program to control corrosion so that multiengine airplanes in scheduled dam age does not exceed Level 1 operations under part 135. In other words, this proposed rule would apply to • Existing CPCPs will satisfy rule most airplanes not currently covered by • Com m ent period closed 1 Apr 2003 AD, in addition to those previously covered by AD. It is unknown if the FAA’s intent is to have these proposed FARs supercede the current CPCP 23 ADs. The rule would require that a baseline program be established that will control corrosion such that it will not exceed Level 1 for the affected airplanes. For Boeing airplanes, the existing CPCPs will satisfy the intent of the rule. Sum mary • M aintain continued airworthiness with • An effective scheduled maintenance program • Com pliance w ith all mandated actions • New rules are being established to apply dam age tolerance and corrosion program s to more of the transport airplane fleet • M aintenance program m ust be valid for extended operations • Structural m aintenance activities will increase as airplanes age 24SE-ACM-4-1-2003 1-9
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  17. 17. 1. Aging Airplane Maintenance Program Developments Addendum 1-1SE-ACM-4-1-2003 1-11
  18. 18. 1. Aging Airplane Maintenance Program Developments Addendum 1-11-12 SE-ACM-4-1-2003
  19. 19. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA ReportAging Aircraft Program Supplemental Structural InspectionDocument (SSID) Review -Final Report- September 2001 Extracted from FAA website: http://www1.faa.gov/certification/aircraft/agingaircraft/ssid/ssid/index.htmTable of Contents Executive Summary Introduction List of Acronyms Phase I Discussion Phase I List of Recommendations Phase I Recommendation Discussion Phase II Discussion Phase II Recommendations and Discussion Appendices A 727 Final Rule B MD-80 Draft NPRM (not attached) C Team Charter (not attached) D Interview Notes (not attached) E 727 and MD-80 AD Comparison F Table of Advantages and Disadvantages G Generic SSID/SID AD H Compliance Time Comparison I Special Inspection Criteria J Flyable Crack Limits Memo (not attached) K Summary of Aging Aircraft Initiatives L Phase II SSID Summary’s Executive SummaryThis report describes the activities of a Team that was chartered to gain knowledge ofthe damage tolerance based inspection aspects of the Aging Aircraft Programs and tomake recommendations regarding how the FAA should handle the SupplementalStructural Inspection Document (SSID) Airworthiness Directives (ADs). During phase I,the team addressed the Boeing 727/737, MD-80, and McDonnell Douglas heritagemodel airplanes, and made recommendations regarding the differences in the treatmentof repairs and modifications in the respective SSID Airworthiness Directives (AD).During phase II, the team addressed the remaining 6 model aging aircraft (Boeing707/720, Fokker F-28, Lockheed L-1011, BAe 1-11, Airbus A300, and CASA C-212),and made recommendations for changes that should be incorporated into theseremaining SSID ADs. 1
  20. 20. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA ReportThis report also describes the process used to develop recommendations that areintended to standardize the repair and modification instructions in the SSID AD’s.Recommendations for both phase I and phase II are listed in this report with ajustification provided for each. A Generic SSID AD implementing the recommendationsfor repairs and modifications are provided in this report to illustrate how standardizedinstructions and compliance times could be incorporated into AD format.Introduction:This report is the product of a team that was chartered by the ANM-110 and AgingAircraft Program Managers. From this point on this team will be referred to as the“Team”. The Team was chartered to obtain a fundamental understanding of thedamage tolerance based inspection aspects of the Aging Aircraft Programs and to makerecommendations in the following two phases of activities.Phase I of the Team’s charter is defined as follows: 1. Recommend a course of action to address the current differences in the treatment of repairs and modifications (especially STC’s) installed both before and after the effective dates of the AD’s for the 727/737 models and DC-8, DC-9, and DC-10 models. Also recommend a course of action for treatment of the draft MD-80 SSID NPRM prepared by the LAACO. If the team’s recommendation is that the mandated programs for these models should be different, the team should provide full explanations and justification for the differences. 2. The team should also determine, in consideration of the general rulemaking, whether changes to the AD’s that mandate SSID programs are necessary.Phase II of the Team’s charter consists of the following activities: 1. Recommend how the FAA should handle SSID AD’s on all of the 11 model aging aircraft (Boeing, Douglas, Lockheed, Airbus, Fokker, CASA, and British Aerospace). If the team’s recommendation is that the mandated programs for the eleven Aging Aircraft models should be different, the team should provide full explanations and justification for the differences. It’s important to note that CASA was not identified in the SSID Team Charter as being one of the aging model aircraft. However, the Team became aware that CASA had produced a SSID document for the C-212, which had been subsequently mandated by a FAA AD. Therefore, during Phase II the Team gathered information on the CASA C- 212 SSID and FAA AD, then evaluated them along with the other aging aircraft. The addition of CASA resulted in the Team evaluating a total of 12 aging aircraft models during both Phase I and Phase II. Even though the Team reviewed the basic Boeing and Douglas SSID programs during the Phase I activities, the Team focused on the difference in the AD mandated implementation of the two basic programs, primarily in the areas of repairs, alterations and STC modifications. The details about the process and activities that the Team took in order to establish recommendations are in the Discussion section of this report.The Team’s recommendations and justification for the recommendations for both phaseI, and phase II of the Team’s review are provided in the Recommendations section ofthis report. The appendices of this report contain several tools that the Team developed2
  21. 21. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Reportand used to establish the Team’s recommendations. The Appendix section alsocontains a Generic AD that demonstrates how the Team’s recommendations can beimplemented into a standardized AD.List of Acronyms and Definitions:CPCP Corrosion Prevention and Control Program (Reference Appendix K for details of this program)DGAC Dirección General de Aviación Civil (The Spanish Airworthiness Authorities responsible for the State of Design for CASA)DGAC (The French Airworthiness Authorities responsible for the State of Design for Airbus)DSG Design Service GoalPSE Principal Structural ElementRAP Repair Assessment Program (Reference Appendix K for details of this program)RLD Rijksluchtvaartdienst (The Netherlands Airworthiness Authority responsible for the State of Design for Fokker)SID Supplemental Inspection Document-Sometimes the Acronym SID is interchanged with SSIDSIP Structural Integrity ProgramSRP Sampling Rotational ProgramSSID Supplemental Structural Inspection Document-Sometimes the AcronymSSID is interchanged with SIDSSD Structurally Significant DetailSSI Structurally Significant ItemPhase I Discussion:The process used to develop the recommendations intended to standardize the repairsand modifications paragraphs of the SSID/SID ADs, where necessary, took severalmeetings and telecons over a period of five months. Prior to making anyrecommendations, the Team conducted interviews with FAA engineers, FAA nationalresource specialist, FAA aging aircraft program manager; FAA aircraft evaluationgroup, FAA legal counsel, Boeing north engineers; Boeing Long Beach engineers(MDC), and engineers from an airline operator (who requested to remain anonymous).The interviews were conducted in person when feasible and by telephone when timeand distance was an obstacle. These interviews helped the Team to gain afundamental understanding of the basic SSID/SID programs and the AD’s that mandatethem. Detailed notes from these interviews are located in Appendix D of this report.The Team met several times in both Los Angeles and in Seattle to conduct the review ofthe SSID/SID AD’s and their differences. During these meetings the Team developedseveral tools to assist in the decision making process. One tool that was developed 3
  22. 22. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Reportwas a table comparing the 727/737 AD’s and MD-80 draft NPRM paragraphs related torepairs, alterations and STC modifications. This comparison table was usedthroughout the review and can be found in Appendix E of this report. The comparisontable was used to assist the Team in identifying and listing the differences between the727/737 AD’s and the MD-80 draft AD. From this list of differences, the Team identifiedand created a table of advantages and disadvantages based on the information gainedfrom the interviews. The table of advantages and disadvantages was used to identifywhat worked well from each AD. The table of advantages and disadvantages islocated in Appendix F of this report. This table was used in the formulation of theTeam’s recommendations.A Generic SSID/SID AD implementing the Team’s recommendations was drafted toassist in illustrating the recommendations and was used as a tool to ensure therecommendations could be implemented in AD format. The Generic AD paragraphswere limited to those with requirements for inspection program revisions related torepairs and modifications. The development of the Generic AD helped the Team tofine-tune the final recommendations. The Team recognizes that the 727/737 AD’s andMDC SID AD’s will continue to be different in the areas where the basic SSID/SIDinspection requirements are specified. However, for repairs and modifications, theSSID/SID AD’s may use the standardized compliance time in the Generic AD. TheGeneric SSID/SID AD is located in Appendix G of this report.The Team is in concurrence with 8 final recommendations resulting from the evaluationof the 727/737 and MDC SSID/SID AD’s. In parallel with the development of theGeneric SSID/SID AD, the Team looked at each recommendation in detail and provideda rational justification for each recommendation.A summary of each of the aging aircraft initiatives is included in Appendix K of thisreport. The aging aircraft initiatives include the Repair Assessment Program,Widespread Fatigue Damage, Aging Airplane Safety Initiative, Corrosion ControlProgram, and Supplemental Structural Inspection Programs. It was important for theteam to become familiar with these initiatives, since some of them have requirementswhich can overlap the SID requirementsPhase I List of Recommendations:The following is a list of recommendations that the Team concurs should be consideredfor revision of the Boeing 727/737 and McDonnell Douglas heritage model airplanesSSID/SID AD’s.Recommendation 1: Add a requirement to perform a damage tolerance assessment forrepairs and modifications accomplished after the effective date of the ADs using astandardized compliance time of 18 months.Recommendation 2: a) Standardize to a 3-step damage tolerance assessment process for new repairs, STC’s and other design changes. b) Provide a standardized description of an acceptable damage tolerance assessment methodology, similar to Note 6 of the 727 AD, by referencing Advisory Circular 91-56A.Recommendation 3:4
  23. 23. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Report a) Eliminate the term “SSI created” in the 727/737 AD’s. b) Criteria for determining which repaired, altered or modified structure requires damage tolerance based special inspections should be jointly developed by the cognizant ACO’s, and added to the AD’s.Recommendation 4: Standardize the compliance time to perform a damage toleranceassessment for repairs and non-STC design changes accomplished before the effectivedate of the ADs as follows: a) For airplanes that have already exceeded their SSID threshold the compliance time should be 18 months after the effective date of the AD. b) For airplanes that have not reached their SSID threshold, the compliance time should be 18 months after the SSID threshold, or within 5 years after the effective date of the AD, whichever occurs first.Recommendation 5: Provide a description in the AD’s detailing the information to beincluded in the operators FAA-approved maintenance or inspection program.Recommendation 6: Standardize the acceptance of the Repair Assessment Guidelines(RAG), where applicable, as a method of compliance to recommendation 1 and 4requirement for a damage tolerance assessment of repairs. The RAG should only beapplicable for those repairs found on the fuselage pressure vessel.Recommendation 7: a) Standardize the compliance time to perform a damage tolerance assessment for STC’s accomplished before the effective date of the AD’s similar to paragraph (d)(2) of the 727/737 AD’s, and remove paragraph (d)(1) from the 727/737 AD’s. b) Include a note similar to Note 7 in the 727/737 AD’s, which provide FAA expectations for the contents of the compliance plan specified in paragraph (d)(2).Recommendation 8: Accomplish a separate evaluation of the Damage ToleranceNational Resource Specialist concerns about the basic SSID/SID program.Phase I Recommendation Discussion:Recommendation 1: Add a requirement to perform a damage toleranceassessment for repairs and modifications accomplished after the effective date ofthe ADs using a standardized compliance time of 18 months.The compliance time specified in paragraph (g) of the 727/737 AD for revision of theFAA-approved maintenance or inspection program is 12 months for all repairs andmodifications installed after the effective date of the AD. In contrast, the compliancetime specified in paragraph (d) of the MD-80 draft NPRM for revision of the FAA-approved maintenance or inspection program is 18 months. The 18 month compliancetime in the MD-80 draft NPRM was based upon the compliance time that the LA ACOhas been using for approval of the damage tolerance assessment of repairs on PSEs.This compliance time is linked to the 3-stage approval process, which is discussed indetail under recommendation 2 (a). Until about 5 years ago, the LA ACO had been 5
  24. 24. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Reportusing a 12 month compliance time for the approval of the damage toleranceassessment. However, as the result of a large increase in the number of repairs thatneeded to be assessed for damage tolerance, McDonnell Douglas (MDC) requestedthat the LA ACO extend this compliance time to 18 months. They cited difficulties inmeeting the 12 month compliance time. MDC justified their request with the argumentthat a repair, which has been shown to meet static strength requirements, will inherentlybe able to resist fatigue cracking for a period greater than 18 months. The LAACOconcurred with MDC and has since routinely required approval of the damage toleranceassessment 18 months after accomplishment of the repair.The Seattle ACO does not concur with the use of an 18 month compliance time for thecompletion of damage tolerance assessment (DTA) of repairs and modifications for thefollowing reasons: 1. The 18 month compliance time is not consistent with the guidelines established in AC 25.1529-1, where it states that a time period not to exceed 12 months is generally adequate for most structural repairs. 2. The airline operators are not required to retain records for minor repairs longer than 12 months, which will result in the operator’s losing track of the repair date and of when the DTA is to be completed. In addition, the operator’s FAA maintenance inspectors would not be able to enforce an 18 month compliance time since the operators were not required to maintain the records longer than 12 month. The Team could find no valid argument against the MDC statement that a repair, which has been shown to meet static strength requirements, will inherently be able to resist fatigue cracking for a period greater than 18 months. The Team further reviewed AC 25.1529-1 and could find no technical justification for the 12 month compliance time providing any significantly higher level of safety than the 18 month compliance time used by the LAACO. The Team interviewed Mr. Jim Dodge from ANM-230 to find out what operating rules would require the airline operators to maintain records longer than 12 months. The Team explained the concerns of the Seattle ACO and asked if the 18 month compliance time would be difficult for the FAA maintenance inspectors to enforce. Jim explained that 14 CFR Part 39.3 states that no person may operate a product except in accordance with the requirements of the AD. Therefore, since the SSID will be mandated by ADs, the operators would be required to comply with the terms and limitations of the AD. However, FAR 121.380 only requires that records of major repairs be kept for a maximum period of 12 months. Due to the allowance in the regulations that only require carriers to retain major repair records for 12 months, Jim indicated difficulty may result in enforcing compliance with the AD since the operator could indicate that an assessment was accomplished for a repair, and that there was no affect to the structure thus requiring no further FAA approval. The Team had similar discussions with engineering managers at separate airlines, with each responding that they believed they would have to maintain the records longer than 12 months if the AD specified a longer compliance time for an assessment to be accomplished. After evaluating AC 25.1529-1 and considering the interviews with the airline engineers and Jim Dodge, the Team is in agreement that an 18 month compliance time for the approval of the DTA is justified and does not reduce the level of safety.6
  25. 25. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Report Therefore, the Team recommends that the SSID AD’s specify a standardized compliance time of 18 months for the accomplishment of a DTA for repairs and modifications.Recommendation 2: a) Standardize to a 3-step DTA process for new repairs, STC’s and other design changes. b) Provide a standardized description of an acceptable damage tolerance assessment methodology, similar to Note 6 of the 727 AD, by referencing Advisory Circular 91-56A.Recommendation 2(a) For new repairs, STC’s and other design changes installed after the effective date of the AD, paragraph (g) of the 727/737 AD’s states: “Within 12 months after that modification, alteration, or repair, revise the FAA-approved maintenance or inspection program to include an inspection method and compliance times for each new or affected SSI, and to include the compliance times for initial and repetitive accomplishment for each inspection.” During interviews with SACO engineers, the Team learned that SACO issued an AMOC to the 727/737 AD’s that allows the use of a two-step procedure for damage tolerance assessment of repairs. The two-step approval process consists of the following: 1. Evaluate the repair to determine the inspection threshold within 12 months of installation. 2. Prior to the inspection threshold or within 12 months after accomplishing the inspection at the SSID threshold, whichever occurs first, complete the damage tolerance assessment to determine the repetitive inspection intervals based on the inspection method. During interviews with LAACO engineers, the Team learned that LAACO has accepted a three-stage process for approval of damage tolerance assessment of repairs. This three-stage approval process consists of the following: 1. Static strength approval prior to further flight. 2. Damage tolerance assessment approval within 18 months of the static strength approval. 3. Inspection method and repeat interval approval 2 years prior to the inspection threshold determined by the damage tolerance assessment. The concepts of the two methods are similar with some minor differences. SACO does not include the first step of the LAACO three-phase process since damaged SSID items per SACO have to be repaired using methods approved by FAA, while the LAACO AD’s require that PSE’s found cracked during a SID inspection be repaired in a manner approved by the manager of the LAACO. The other minor difference between the two approval processes is that LAACO allows 18 months after repair to establish the inspection threshold, while SACO allows 12 months after repair 7
  26. 26. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Report to establish the inspection threshold. Additionally, LAACO requires that the inspection method and intervals be approved 2 years prior to reaching the inspection threshold, while the SACO method requires the inspection method and intervals be established prior to the inspection threshold or within 12 months after accomplishing the inspection at the SSID threshold, whichever occurs first. Both the SACO two-step approval process and the LAACO three stage approval process are based on the two-stage structural evaluation concept that is discussed in Advisory Circular (AC) 25.1529-1. The AC states that a time period not to exceed 12 mo. is generally adequate for most structural repairs. Until about 5 years ago, LAACO had been using a 12 month compliance time for the approval of the damage tolerance assessment. However, as the result of a large increase in the number of repairs that needed to be assessed for damage tolerance, McDonnell Douglas (MDC) requested that the LAACO extend this compliance time to 18 months. They cited difficulties in meeting the 12 month compliance time. MDC justified their request with the argument that a repair, which has been shown to meet static strength requirements, will inherently be able to resist fatigue cracking for a period greater than 18 months. The LAACO concurred with MDC and has since routinely required approval of the damage tolerance assessment 18 months after accomplishment of the repair. As similarly discussed in recommendation 1, the team could find no technical justification for the 12 month compliance time described in AC 25.1529-1 providing any significantly higher level of safety than the 18 month compliance time approved by the LAACO. Therefore, the team is in agreement that the use of an 18 month compliance time rather than a 12 month compliance time for the approval of the damage tolerance assessment is justified and does not reduce the level of safety. The 727/737 AD’s require that new inspection methods and compliance times for SSI’s created or affected by a repair, STC, or other design change be approved by the Manager, Seattle Aircraft Certification Office. The MD-80 draft NPRM requires that new inspection methods and compliance times for PSE’s affected by a repair, STC, or other design change be approved by the Manager, LAACO. The approval of a new inspection method and compliance time by the airplane’s type certificate managing ACO may not make sense for STC alterations. The STC may be issued by an ACO other than the airplane’s type certificate managing ACO. In this case, all of the data supporting the STC and the ACO engineering awareness of the STC modification resides in the ACO that is managing the STC. Therefore, the team recommends that the approval of the inspection method and compliance time for STC alterations be done by the STC managing ACO and that approval of the inspection method and compliance time for repairs and non-STC design changes be done by the airplane’s Type Certificate Managing ACO. The Team also recommends that a standardized approval process for new repairs, STC’s and other design changes be used by adopting the three-stage approval process as outlined above. The Team recommends that SACO and LAACO continue approval of the first phase of the process as they feel appropriate for individual SID/SSID programs. The Team recommends the use of an 18-month compliance time for the damage tolerance assessment because it provides an adequate amount of time for the operators to conduct the assessment as discussed in8
  27. 27. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA Report Recommendation 1. Even though the 18 month compliance time is not consistent with the guidance contained in AC 25.1529-1, the differences can be described in the preamble of the SSID/SID AD’s, which is appropriate since the AD establishes new rulemaking. The Team concurs with the approach of requiring determination of the inspection method and repeat intervals to be established 2 years prior to reaching the inspection threshold. The Team concluded that relating the compliance time for establishment of the repair inspection method and repeat intervals to the established inspection threshold is reasonable. The 2-year compliance time will ensure that the repair inspection method and repeat intervals are in place when the repair inspection threshold is reached. The AD’s should clarify that the DTA for repairs must be approved by the ACO responsible for the type design of the aircraft, and that the DTA for STC’s must be approved by the ACO, which issued the STC. This information should be communicated to all ACO’s if the Manager of the Transport Airplane Directorate approves the recommendations in this report.Recommendation 2(b)Note 6 of the 727/737 AD’s specifies that the inspection methods and compliance timesshould be determined based on a damage tolerance assessment methodology, such asthat described in FAA Advisory Circular No. 91-56, Change 2 dated April 15, 1983. Incontrast, the MD-80 draft NPRM does not specify what is considered an acceptabledamage tolerance assessment methodology for determining the inspection methodsand compliance times.The Team recommends that the AD’s contain a standardized note, similar to Note 6 ofthe 727/737 AD, that specifies an acceptable damage tolerance assessmentmethodology for determining the inspection methods and compliance times. The Teamfurther recommends the standardized note reference the methodology contained in FAAAdvisory Circular No 91-56A, dated April 29, 1998.Recommendation 3. a) Eliminate the term “SSI created” in the 727/737 AD’s. b) Criteria for determining which repaired, altered or modified structure requires damage tolerance based special inspections should be jointly developed by the cognizant ACO’s, and added to the AD’s.Recommendation 3(a)The Team noted that the 727/737 AD’s used the terms “new SSI” and “created SSI” inParagraphs (d)(1), (e), (g), and in note 7. This term was used where a repair, alterationor modification affected the aircraft structure such that damage tolerance based specialinspections are required. The Team further noted that the MD-80 draft NPRM did notaddress any repaired, altered or modified structure that would require damage toleranceassessment other than the PSE’s that had been affected by repairs, alterations andmodifications. The Team recognized that the Boeing and MDC basic SSID/SID weredeveloped differently and use two different terms for structure that requiressupplemental inspections. Because of these differences, it is important that the terms 9
  28. 28. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA ReportSSI created and PSE created not be used in the AD’s to prevent association with theOEM’s basic programs.The Team recommends that the term “new SSI” and “created SSI” not be used in the727/737 AD’s. The SSID/SID AD’s should simply address the affected structure asstructure that requires damage tolerance based special inspections”.Recommendation 3(b)Paragraph (d)(1) and (e) of the 727/737 AD’s require assessment of the damagetolerance characteristics of each SSI created by a repair or design change. Theoperators must revise their FAA-approved maintenance or inspection program to include inspection methods and compliance times for each SSI created. The MD-80draft NPRM does not contain instructions for a PSE created by a repair or an alterationor modification. However, the preamble of the MD-80 draft NPRM states that once theAging Aircraft Safety Act becomes a final rule the MD-80 AD will be superseded toaddress all structural repairs, alterations and modifications and not just those that“affect” a PSE.During interviews, LAACO engineers indicated that the MD-80 draft NPRM takes intoaccount the proposed Aging Airplane Safety Rule, which has been issued as an NPRM(Notice 99-02). This rule will require that within 4 years after the effective date that theoperators maintenance program include damage tolerance based inspections andprocedures, for all repairs and modifications, including STC’s. This rule will beapplicable for all Parts 121, 129, and 135 operating rules. The Aging Airplane SafetyRule is expected to become a final rule in February of 2001.The Team believes that it is important that all repairs, alterations and modifications toairplanes with mandated SSID/SID programs have a damage tolerance assessmentaccomplished in order to determine if damage tolerance based special inspections arenecessary.The Team evaluated the proposed Aging Airplane Safety Rule and determined that it isnot as specific as the SSID/SID AD’s in its requirement to accomplish a damagetolerance assessment and determination of supplemental inspections. The rule doesnot involve the ACO engineers in the review and approval of damage tolerance basedinspection programs. The proposed operating rule states that the operators must havea maintenance program that includes damage tolerance based inspections andprocedures. The airplane operators have the freedom to submit a damage tolerancebased maintenance program to their Principal Maintenance Inspector, with norequirement for the cognizant ACO’s review and approval of the damage toleranceassessment, inspection method, and interval. In addition, the Safety Rule is notapplicable to Part 125 operators, which are cargo operators. The cargo operations fleettypically consists of older airplanes with a large number of these airplanes havingundergone passenger to freighter modifications. These freighters often incorporateseveral significant modifications, which may include auxiliary fuel tanks, zero fuel weightincreases, engine hush kits, and winglets. The Team also evaluated whether theSSID/SID AD’s will conflict with the proposed Aging Airplane Safety Rule. The Teamdetermined that the requirements of the AD’s will not be in conflict with the Safety Rule,but will actually provide the operators with a method to comply with the rule.10
  29. 29. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA ReportThe Team recommends the development of criteria for the determination of whatrepaired, altered or modified structure requires damage tolerance based specialinspections. The criteria, similar to the example provide below, should be jointlydeveloped and adopted by all the cognizant ACO’s:A damage tolerance assessment must be accomplished for all repaired, altered ormodified structure if all of the following criteria have been met: 1. The structure contributes significantly to the carrying of flight, ground or pressurization loads. 2. The integrity of the structure is essential in maintaining the overall integrity of the airplane.Recommendation 4: Standardize the compliance time to perform a damagetolerance assessment for repairs and non-STC design changes accomplishedbefore the effective date of the ADs as follows: a) For airplanes that have already exceeded their SSID threshold the compliance time should be 18 months after the effective date of the AD. b) For airplanes that have not reached their SSID threshold, the compliance time should be 18 months after the SSID threshold, or within 5 years after the effective date of the AD, whichever occurs first.The compliance time specified in paragraph (e) of the 727/737 AD for revision of theFAA approved maintenance or inspection program for repairs and non-STC designchanges accomplished prior to the effective date of the AD, is 12 months after the firstSSID inspection. The 727/737 AD’s address both SSI’s created and affected by therepair or design change. In contrast, the compliance time specified in paragraph (c) ofthe MD-80 draft NPRM for revision of the FAA approved maintenance or inspectionprogram for repairs and modifications (including STC’s) accomplished prior to theeffective date of the AD, is 5 years after the effective date of the AD. The MD-80 draftNPRM addresses PSE’s affected but not PSE’s created by the repair or design change.From the Team’s interviews with an airline operator, it was apparent that paragraph (e)was the only section of the 727/737 AD’s they found acceptable. They indicated thatother 727/737 operators shared this position. Paragraph (e) allows the operators toassess the “old repairs” and “old design changes” at the next SSID inspection and thenallows 12 months after the inspection to determine if a new inspection method orinspection interval is required.During interviews, LAACO engineers voiced concern about inconsistencies in thecompliance time of paragraph (e) of the 727/737 AD’s. Their concern is that designchanges and repairs installed before the effective date of the AD are not addressed until12 months after the first SSID inspection, which could be many years in the future. Thisis in contrast to the requirement that design changes and repairs installed after theeffective date of the AD be addressed within 12 months after installation. They statethat because of this inconsistency, the 727/737 AD’s imply that new repairs and designchanges are less fatigue resistant than old repairs and design changes which could beup to 20 years old. 11
  30. 30. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA ReportThe Team believes there is merit to both the 727/737 operator’s and LAACO concernsabout the compliance time for repairs and design changes accomplished prior to theeffective dates of the AD’s. The Team recognizes that the 727/737 operators do notknow about all the repairs installed on their airplanes, and some operators may nothave sufficient data on the repairs and design changes in their fleets. Because of this,the operators need sufficient time to identify and address these repairs and designchanges.LAACO engineers indicated that there should not be the same concern regarding lackof operator knowledge of repairs affecting the PSE’s. This is because repairsandmodifications that affect PSE’s, the entire PSE must be inspected prior to thethreshold or have an AMOC. Additionally, Boeing South engineers indicated that if anoperator finds that they cannot accomplish a SID inspection due to the existence of arepair or modification, that discrepant PSE must still be inspected prior to the SIDdefined threshold, unless a new threshold is approved by the LAACO. However, FAALegal Counsel expressed concern during the Team’s interview, that operators of MDCairplanes may not be ensuring that damage tolerance assessment and any changes tothe PSE inspections are being accomplished on 100% of PSE repairs. Legal Counselreferred to comments from the airline operators represented at the Joint ManagementTeam meetings, as stating they don’t treat SRM repairs as “major” and have noprocedure for tracking or informing their engineering organizations when SRM repairsare installed. Based on these comments, Legal Counsel questioned the validity ofassuming 100% reporting of repairs on the MDC fleet.Based on all these comments and concerns, the Team recommends a standardizedcompliance time for the 727/737 and MD-80 fleets that have exceeded the SSIDthreshold. The MDC operators should not be affected since they should already be incompliance, and the 18 month compliance time will then allow time for the 727/737operators to comply. If there happens to be some MDC operators that are not currentlyin compliance with reporting all their repairs and modification to PSE’s, the standardizedcompliance time will provide sufficient time for them to comply as well. The Team alsorecognizes that repairs and modifications on relatively young airplanes should not beignored until the first SSID inspection, and that a compliance time similar to the MD-80draft NPRM would be appropriate.Therefore, the Team recommends a combination compliance time broken into twocategories. For airplanes that have already exceeded their SSID threshold, thecompliance time should be 18 months after the effective date of the AD. For airplanesthat have not reached the SSID threshold, the compliance time should be 18 monthsafter the SSID/SID threshold, or within 5 years after the effective date of the AD,whichever should occur first. This proposed two-category compliance time wouldprovide the operators adequate time to assess the repairs and design changes on theairplanes if they have either exceeded or are approaching the SSID threshold. It alsoprovides up to 5 years to make the assessment if their airplanes are still young.The Team chose to use the SSID/SID threshold as the benchmark for the compliancetime rather than the first SSID inspections, as was previously used in the 727/737ADs.By using the inspection threshold, operators who may have accomplished the firstSSID/SID inspection significantly before the SSID threshold will not be penalized.12
  31. 31. 1. Aging Airplane Maintenance Program Developments Addendum 1-2 FAA ReportAdditionally, since the two-categories are divided based on whether the inspectionthreshold has passed, a benchmark of inspection threshold is necessary to avoidconfusion regarding compliance times.Recommendation 5: Provide a description in the AD’s detailing the information tobe included in the operators FAA-approved maintenance or inspection program.The MD-80 draft NPRM does not provide a description of the information that should beincluded in the operators FAA-approved maintenance or inspection program. Incontrast, Paragraph (d)(2)(iii) of the 727/737 AD’s provides instruction to “revise theFAA-approved maintenance or inspection program to include an inspection method foreach new or affected SSI, and to include the compliance times for initial and repetitiveaccomplishment of each inspection. The inspection methods and the compliance timesshall be approved by the Manager, Seattle ACO.” The Team recognizes frominterviews with the Seattle AEG and operators that information clarifying the FAA’sexpectations for AD compliance will reduce miscommunication. The Teamrecommends the SSID/SID AD’s provide compliance information similar to what isshown in Paragraph (d)(2)(iii) of the 727/737 SSID AD to clarify the AD requirements.Recommendation 6: Standardize the acceptance of the Repair AssessmentGuidelines (RAG), where applicable, as a method of compliance torecommendation 1 and 4 requirement for a damage tolerance assessment ofrepairs. The RAG should only be applicable for those repairs found on thefuselage pressure vessel.Note 6 of the MD-80 draft NPRM accepts the Aging Aircraft Repair AssessmentGuidelines (RAG) as an acceptable method of compliance for the draft NRPM.Currently, the 727/737 AD’s do not recognize the RAG’s as an acceptable method ofcompliance to the AD’s. The Repair Assessment Program is mandated by Part 91.410,121.370, 125.248 and 129.32 operating rules, with the RAG’s being approved as anacceptable method of complying with the damage tolerance assessment and inspectionrequirements of the rules. Because the RAG’s are approved by the cognizant ACO’sand contain damage tolerance based inspections for certain repairs, they should beaccepted as a method of compliance for those repairs found on the fuselage pressurevessel.Recommendation 7: a) Standardize the compliance time to perform a damage tolerance assessment for STC’s accomplished before the effective date of the AD’s similar to paragraph (d)(2) of the 727/737 AD’s, and remove paragraph (d)(1) from the 727/737 AD’s. b) Include a note similar to Note 7 in the 727/737 AD’s, which provide FAA expectations for the contents of the compliance plan specified in paragraph (d)(2).The compliance time specified in paragraph (d) of the 727/737 AD’s provides the optionof two compliance times. This paragraph addresses SSI’s affected by STC’saccomplished prior to the effective date of the AD. Paragraph (d)(1) requires that adamage tolerance assessment and new inspections be determined within 18 months of 13

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