Aging Transport

The U.S. Federal AviationAdministration andindustry representativesare working together todetermine how existingmaintenance practicesmay be improved to helpensure the continued airworthiness of olderairplanes. Although fact-finding efforts to datehave found no endemicsafety issues, recom-mendations are beingmade to enhance thedesign and maintenanceof airplane electrical systems and associateddocumentation andtraining.

UPDATE:

S A F E T Y

DONALD ANDERSEN

MANAGER

REGULATORY AND INDUSTRY LIAISON

BOEING COMMERCIAL AIRPLANES

PAUL LAPWOOD

INSTRUCTOR

MAINTENANCE

FLIGHTSAFETY BOEING TRAINING INTERNATIONAL

GIL PALAFOX

MANAGER

MAINTENANCE ENGINEERING

BOEING COMMERCIAL AIRPLANES

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Systems Investigation

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Although none of the teams identifiedany issue related to the immediate safety of the aging fleet, they did suggest enhancements to existingdesign, maintenance, and operationalprocedures for the continued air-worthiness of all airplanes.

Fleet condition.One team reviewed the condition of the aging fleet by conducting a non-intrusive evaluation of the wiring on 81 in-service airplanes and a detailed,intrusive inspection of the wiringremoved from six recently retired airline airplanes.

The team found that wiring degra-dation primarily is not related to the age of the airplane (i.e., the time since manufacture), the environment in which the airplane operates, or the typeof wiring. Rather, wiring degradation is influenced significantly by the main-tenance and modification performedthroughout the life of the airplane. Theteam also determined that a generalvisual inspection of the wiring installedon airplanes, which typically is con-ducted from a distance of a few feet,cannot adequately assess the condition

ATSRAC FINDINGS AND RECOMMENDATIONS

The initial ATSRAC investigation ofaging airplane wiring studied five factors: fleet condition, fleet service history, maintenance criteria, standardpractices for wiring, and inspection and repair training. A team of ATSRACmembers and industry representativeswas assigned to evaluate each parame-ter. The teams conducted analyses,made conclusions, and recommendedfollow-up actions, which the ATSRACthen reviewed, approved, and provided to the FAA.

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As part of its effort to ensure the continued airworthiness ofaging airplanes (i.e., airplanesbuilt to type designs that aremore than 20 years old), the U.S.Federal Aviation Administration(FAA) formed a fact-findingcommittee in 1998 to evaluatethe airplane systems of the agingfleet and propose enhancementsto current procedures. The AgingTransport Systems RulemakingAdvisory Committee (ATSRAC),which is composed of represen-tatives from various segments ofthe aviation industry, is focusingits investigation on airplanewiring. (See “Aging AirplaneSystems Investigation,”Aero no. 7, July 1999.) The committee completed its initialtasks in January 2001 and is continuing with plans to imple-ment its recommendations.

This article discusses

1. ATSRAC findings and recommendations.

2. Implementation of ATSRAC recommendations.

3. FAA actions.

4. Enhanced Airworthiness Program for Airplane Systems.

5. Boeing support.

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737

747

DC-8

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737-24-1144

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DC9-74A001 DC9-72A002

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DC10-76A048 DC10-76A049

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Notice of Proposed Rulemaking 2001-NM-99-AD

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Boeing service bulletin

Electrical Power – Auxiliary Power Unit Generator Feeder Wire Bundle – Inspection

Electrical Power – Main 115 Volt AC Power Distribution – Wire Inspection and Protective Sleeving Installation

Equipment/Furnishings – Flight Compartment – Flight Engineer’s Panel – Wire Bundle Clamping Modification

Passenger Oxygen System – Passenger Service Unit Hose/Wire Bundle Inspection

Equipment/Furnishings – Electrical/Electronic Equipment Center – Water Dripshield Modification

Electrical Power – Aircraft Wiring & Connectors General – Replace Toilet Flushing Circuit Breakers

Electrical Power – Electrical Load Distribution – Modify Nacelle/Pylon Generator Power Feeder Cable Support Clamp Installation

Ice and Rain Protection – Windshield Heating and Control System – Inspect/Replace Clearview Window Wiring Conduit

Lights – Main Cabin Illumination – Install Protective Insulation on Terminals of Cabin Lighting Switches

Electrical Power – Electrical Load Distribution – Inspect Auxiliary Power Unit (APU) Power Feeder Cables and Revise Bus Terminals

Electrical Power – Electrical Load Distribution – Inspect Electrical Wiring for Chafing/Damage and Install Grommet on Conduit in Forward Electrical Power Center

Electrical Power – External Power – Inspect/Replace External Power Ground Stud and Install Nameplate

Electrical Power – Electrical Load Distribution – Revise Power Feeder Cable Support Installation and Inspect for Wire Damage

Flight Controls – Spoiler Control and Indication – Modify Spoiler Control System

Lights – Passenger Compartment Lights – Rework Reflector Assemblies and Install Insulation Blanket Supports

Lights – Passenger Compartment Lights – Inspect/Revise Wire Routing of Attendants’ Aft Cabin Work Lights

Lights – Passenger Compartment Lights – Revise Cabin Sidewall Lights Circuitry

Lights – Cargo and Service Compartment Lights – Modify Cargo Compartment Light Switch

Lights – Passenger Compartment Lights – Replace Upper and Lower Cabin Sidewall Fluorescent Light Ballasts

Ignition – Switching – Inspect/Replace Rotary Ignition Switch Engine Ignition – Ignition Switching – Inspect/Replace Rotary Ignition Switch

Navigation – Attitude and Direction – Replace Navigation Transfer Circuit Breaker

Engine Controls – Engine Power Control – Modify Throttle Control Module Engine Controls – Engine Power Control – Inspect/Repair Throttle Control Module Wiring

Electrical Power – Electrical Load Distribution – Inspect Circuit Breakers on Flight Engineer’s Equipment Panel for Proper Wire Connections

Electrical Power – Electrical Load Distribution – Inspect/Modify/Repair/Replace APU Power Feeder Cable and Clamp Installation

Electrical Power – DC Generation – Relocate Battery 1 Ground Stud Bracket Assembly

Electrical Power – Electrical Load Distribution – Inspect/Install Spiral Wrap on External Ground Power Feeder Cable Assemblies in Forward Lower Cargo Compartment

Electrical Power – AC Generation & Control – Inspect Wire Bundle and Modify Wire Bundle Support Clamp Installation at Flight Engineer’s Station

Airplanemodel Number Title

FAA AD

DIRECTIVES RESULTING FROM SERVICE DOCUMENT REVIEW

TABLE

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of the wiring. Specific recommenda-tions included an increased emphasis on the periodic removal of accumulatedcontaminants and clarification of therequirements regarding the spatial separation of wiring for critical airplane systems.

Fleet service history.A second team reviewed all existingservice information applicable to theolder airplanes under study. Of the thousands of wiring-related service documents (e.g., service bulletins,service letters, all-operator letters,in-service activity reports) reviewed,29 service bulletins contained airplanemodifications important enough to justify upgrading the service bulletins to alert status. (Boeing releases alert service bulletins to address issues ofsafety over the life of the fleet.) TheFAA has released 26 airworthinessdirectives (AD) and proposed one AD that mandate incorporation of themodifications (table 1).

Maintenance criteria.A third team evaluated the recom-mended scheduled maintenance activitiesfor older airplanes. Most modern

manufacturers adopt a common document format and include thesame types of information in newdocuments so that technicians andengineers can easily use documentsfrom different manufacturers. Theteam also recommended that existingdocuments be updated to reflect therevised format and content.

Inspection and repair training.The fifth team reviewed available programs for training personnel with access to wiring and electrical systems.The team found a need for a trainingprogram specific to wiring to ensurethat all aviation personnel who are incontact with the airplane are aware of the importance of airplane wiring.The team recommended a training curriculum that is standardized, withcontent customized to operators’specific airplane models.

IMPLEMENTATION OF ATSRACRECOMMENDATIONS

The teams recommended enhance-ments to maintenance programs, train-ing programs, airplane documentation,and future airplane design. However,the level of detail and the methods of

commercial airplanes are delivered with a recommended maintenance planbased on an airplane zonal analysisusing the Maintenance Steering GroupLevel 3 (MSG-3) evaluation process.However, the MSG-3 and previous evaluation processes did not considerthe airplane wiring as a specific system.The typical result was that airplanewiring was examined visually when a maintenance technician was in thegeneral area for other reasons.

The team concluded that an enhancedmaintenance analysis process was needed to specifically evaluate airplanewiring. This enhanced zonal analysisprocedure (EZAP) can be accomplishedon all airplanes regardless of whetherthey have been evaluated previouslyusing the MSG-3 process. (See“Enhanced Zonal Analysis Procedure”on p. 16.)

Standard practices for wiring.Another team evaluated the documen-tation concerning wiring repair andmaintenance and determined that theinformation used to inspect, repair,and replace airplane wiring could beimproved and made easier to use. Theteam recommended that all airplane

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FAA ACTIONS

The FAA already has taken regulatoryaction to increase the margin of safety of older airplane models. These actionsinclude issuing ADs regarding airplanemodifications (table 1), developing atraining program about airplane wiringsystems, forming a policy statement on thecertification of wiring systems, releas-ing bulletins on operation specifications and the principal maintenance inspector handbook, and improving rules and com-munication with worldwide regulatoryauthorities on service difficulty reports.

The FAA’s long-term plans are to

■ Implement the remaining fourATSRAC tasks.

■ Change maintenance and trainingrequirements under Part 121 of theFederal Aviation Regulations (FAR).

■ Release related ACs and operationspecifications.

■ Enhance airplane design require-ments as appropriate.

■ Issue requirements and guidelines for the installation of arc-fault circuitbreakers that are under development.

implementing these enhancements needed further development.

In January 2001, the FAA recharteredthe ATSRAC to provide more details on the recommendations and developimplementation plans. Specifically, theFAA asked the ATSRAC to accomplishfour tasks by January 2003:

■ Review and consolidate the federalregulations used to certify airplanewiring systems.

■ Standardize the format and content ofwiring standard-practices documents.

■ Develop the content and imple-mentation plan for an industrywide common training program.

■ Develop an enhanced zonal maintenance plan.

To accomplish these tasks, theATSRAC formed four new teams, eachcochaired by industry representativesunder the authority of the FAA and the European Joint Aviation Authorities. In addition to completing its specifiedtask, each team was asked to produceguidance material in the form of draft advisory circulars (AC) and recommendspecific terminology for use in futureregulatory mandates.

■ Establish wire performance requirements.

■ Develop an automated system forreporting service difficulties.

■ Conduct ongoing research and development of maintenance equipment used in the assessment of airplane wiring.

Institutionalizing the ATSRAC re-sults and recommendations will requireall holders of type certificates and supplemental type certificates to changeexisting instructions for continuedairworthiness. These requirements areexpected to apply to all FAR Part 91,121, 125, 129, and possibly 135 opera-tors. In addition, changes to Part 25 will combine existing wiring designand certification requirements andinclude any new requirements iden-tified by the ATSRAC. These changeswill apply to all new type certificateand supplemental type certificate applications.

The FAA plans to release a specialfederal aviation regulation (SFAR),based on ATSRAC recommendations,which will mandate the incorporation of an EZAP to enhance airplane main-tenance programs. In addition, the FAA

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plans to update sections of the FARs for private, charter, and domestic com-mercial operators and foreign commer-cial operators operating in the UnitedStates. These operators will be requiredto update their maintenance and trainingdocumentation to include the notedenhancements. In addition to the SFARand changes to FAR Parts 91, 121,125, and 129, related ACs will provide guidance on an acceptable means ofcompliance.

The FAA expects to begin developingthe SFAR changes, the FAR changes,and the accompanying ACs and otherguidance material during fourth-quarter2002. The ATSRAC will review thesematerials before they are placed on thepublic docket to help ensure that man-dated actions are readily implemented in the fleet. All changes are subject to public review under the Notice ofProposed Rulemaking procedures.Regulation changes, AC releases, and the issuance of operations specificationsare expected to continue through 2004.

ENHANCED AIRWORTHINESS PROGRAM FOR AIRPLANE SYSTEMS

The ATSRAC efforts are part of an overarching plan developed by the FAA known as the EnhancedAirworthiness Program for AirplaneSystems (EAPAS). The EAPAS outlinesthe results and recommendations of theATSRAC and other fact-finding groupsand explains how this knowledge will be applied throughout the aviationindustry. Although the program has been designed to encourage voluntarycompliance, the FAA’s objective of institutionalizing an enhanced andacceptable level of safety requires theuse of mandatory requirements. TheEAPAS organizes this information and initiates both short-term and long-termimplementation actions to enhance thesafety of the entire domestic fleet. Forthis reason, the EAPAS omits specificreference to older airplanes. The pro-gram is intended to focus on all airplanesystems, with mechanical systems toundergo detailed evaluation after wiring.

BOEING SUPPORT

Boeing supports the ATSRAC andEAPAS through active participation and the development of both guidancematerial and programs to comply withexpected regulatory mandates.

■ Boeing has developed the EZAPbased on the MSG-3 process for older Boeing airplane models. Boeing has applied the EZAP to the 727 and plans to apply it to all in- and out-of-production airplanes.

■ FlightSafety Boeing TrainingInternational has developed a wiringtraining course to meet the expectedFAR requirements. The programenables the operator or repair station to tailor the curriculum to the technical expertise of the studentand to the specific airplane model. (See “Airplane Wiring SystemsTraining” on p. 16.)

■ Boeing is revising the BoeingStandard Wiring Practices Manualto add new procedures for cleaninginstalled wiring, performing a detailed wiring inspection, and protecting wiring during related and unrelated maintenance.

■ In addition to the requirements out-lined in the regulatory mandate andthe guidance provided by the ACs,Boeing will be available to assistoperators in the development andimplementation of their enhancedcontinued airworthiness programs.For example, Boeing will release supplemental guidance material that, although not expected to be regulatory agency approved, will provide information on existing maintenance, training, and inspec-tion programs that are known to have complied with the SFAR. Thisguidance material also will describeregulatory programs or material not typically distributed worldwide.Operators can use this information to develop their programs.

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The FAA asked industry representatives to review the systems installed on the aging airplane fleet anddetermine whether changes to existing processesand designs were needed to offset the effects ofaging. Investigation of airplane wiring systems indicated that, although no endemic issues related tothe immediate safety of the airplanes were identified,safety enhancements could be implemented. Theseenhancements relate to the design and maintenanceof airplane electrical systems and associated docu-mentation and training.

The FAA has developed a program, the EAPAS, to promote voluntary incorporation of these enhance-ments, charter related reporting and research projects, and provide guidance on the expeditedincorporation of the anticipated changes to relatedfederal regulations.

Boeing is actively participating in the EAPAS and is providing the industry with information andentire programs that are expected to comply withthe forthcoming changes. In addition, Boeing will assist operators in their efforts to incorporatethese changes into their current maintenance andtraining programs.

SUMMARY