improvement of maintenance criteria - task 3 1 improvement of maintenance criteria atsrac task 3...

Improvement of Maintenance Criteria - Task 3 Improvement of Maintenance Criteria - Task 3 Improvement of Maintenance Criteria - Task 3 Improvement of Maintenance Criteria - Task 3 11

Improvement of Maintenance CriteriaImprovement of Maintenance Criteria

ATSRAC Task 3ATSRAC Task 3

presented by T J Harbottlepresented by T J Harbottle

Task 3 Working Group ChairmanTask 3 Working Group Chairman

Seattle - November 2001Seattle - November 2001


Improvement of maintenance criteria - Task 3 Improvement of maintenance criteria - Task 3

ContentsContents

• BackgroundBackground

• Recommendation summaryRecommendation summary

• Development of new logicDevelopment of new logic

• Revised inspection definitionsRevised inspection definitions

• Single element dual load path designSingle element dual load path design

• Consequences for operatorsConsequences for operators

• ConclusionConclusion



• BackgroundBackground







ContentsContents


BackgroundBackground

• ATSRAC’s Task 3 WG formed in 1999 to identify ATSRAC’s Task 3 WG formed in 1999 to identify proposals for the proposals for the “Improvement of maintenance “Improvement of maintenance criteria”criteria”

• During 2000, the group assessed sub-tasks During 2000, the group assessed sub-tasks associated withassociated with– Maintenance program developmentMaintenance program development

– Inspection and maintenance task accomplishmentInspection and maintenance task accomplishment

– Maintenance practicesMaintenance practices

• A list of recommendations were developed and A list of recommendations were developed and agreed by ATSRAC in Jan 2001agreed by ATSRAC in Jan 2001



ContentsContents

• Background








Recommendation summaryRecommendation summary

These recommendations includeThese recommendations include

• Application of an Application of an Enhanced Zonal Analysis ProcedureEnhanced Zonal Analysis Procedure

• Clarification of Clarification of GVIGVI and and Detailed InspectionDetailed Inspection

• Guidance on the Guidance on the expectationsexpectations of a GVI performed as of a GVI performed as part of part of Zonal InspectionZonal Inspection

• Protections Protections and and cautions cautions to be observed when to be observed when performing certain maintenance or servicing tasksperforming certain maintenance or servicing tasks

• The need to The need to re-assessre-assess continuous airworthiness of continuous airworthiness of dual dual load path designload path design features in flight control systems features in flight control systems



ContentsContents

• Background

• Recommendation summary







• Through an iterative process, an Through an iterative process, an EnhancedEnhanced Zonal Zonal Analysis Procedure was developed.Analysis Procedure was developed.

• Starting point: ATA’s MSG-3 Zonal Analysis Procedure Starting point: ATA’s MSG-3 Zonal Analysis Procedure previously used to develop Zonal Inspection Programspreviously used to develop Zonal Inspection Programs

Development of new logicDevelopment of new logic

• This had to address the findings from the non-intrusive This had to address the findings from the non-intrusive inspections performed during the Task 1 survey.inspections performed during the Task 1 survey.Its focus was to address wiring installations.Its focus was to address wiring installations.

Enhanced zonal analysis procedureEnhanced zonal analysis procedure



• Many findings related toMany findings related to

– Inappropriate or deteriorated repairsInappropriate or deteriorated repairs

– Mechanical damageMechanical damage

– ContaminationContamination

– Inadequate attachment of wires and bundlesInadequate attachment of wires and bundles

• House keeping issues - most would be evident House keeping issues - most would be evident during existing inspections. during existing inspections. They were seen but not They were seen but not addressedaddressed

• Learned complacency needs to be overcome - Learned complacency needs to be overcome - enhanced awareness is necessaryenhanced awareness is necessary

Findings analysisFindings analysis



• Primary concern is the Primary concern is the potential fire hazardpotential fire hazard

• EZAP must identify tasks to EZAP must identify tasks to minimizeminimize this potential this potential

• The results must be The results must be realisticrealistic

• Any new tasks must Any new tasks must not not increase potential for new increase potential for new discrepanciesdiscrepancies



• EZAP starts with identification of zones containing EZAP starts with identification of zones containing wiringwiring

• For each zone, the enhanced logic is performed ifFor each zone, the enhanced logic is performed if– Combustible materials may be present Combustible materials may be present

oror

– Wiring is installed close to primary and back-up Wiring is installed close to primary and back-up hydraulic/mechanical flight controlshydraulic/mechanical flight controls

• It will always be applied in flight compartment and It will always be applied in flight compartment and avionics / electronic baysavionics / electronic bays

Application processApplication process



• Logic first leads to identification of task(s) to address Logic first leads to identification of task(s) to address actual or potential contaminationactual or potential contamination

• These may includeThese may include

– Removal of heavy accumulations of dust/lintRemoval of heavy accumulations of dust/lint

– Drying pools of fluidsDrying pools of fluids

– Cleaning/discard of contaminated insulation blanketsCleaning/discard of contaminated insulation blankets

– Detailed inspection of high pressure hydraulic lines in Detailed inspection of high pressure hydraulic lines in close proximity to wiring close proximity to wiring

Application process Application process (cont’d)(cont’d)



• Logic then identifies wiring inspection tasksLogic then identifies wiring inspection tasks

• Inspection Inspection levellevel determined with consideration to determined with consideration to– Potential effect of localized fire on adjacent systemsPotential effect of localized fire on adjacent systems

– Size of inspection areaSize of inspection area

– Density of installed equipmentDensity of installed equipment

• Inspection Inspection intervalinterval determined with consideration to determined with consideration to– Potential for accidental damagePotential for accidental damage

– EnvironmentEnvironment

Application process Application process (cont’d)(cont’d)



• In conclusion, for each zone, the enhanced logicIn conclusion, for each zone, the enhanced logic– Permits identification ofPermits identification of

• Tasks to reduce likelihood of significant build-up of Tasks to reduce likelihood of significant build-up of combustible materialscombustible materials

• Detailed Inspections of some or all wiring in a zoneDetailed Inspections of some or all wiring in a zone

• Standalone GVIs of some or all wiring in a zoneStandalone GVIs of some or all wiring in a zone

oror – Confirms that existing zonal inspection is adequateConfirms that existing zonal inspection is adequate

Enhanced logic: summaryEnhanced logic: summary

• Any new tasks identified will need to be included in the Any new tasks identified will need to be included in the Systems and Power Plant programsSystems and Power Plant programs



• Some breeches were discovered in the wiring Some breeches were discovered in the wiring insulationinsulation

• These are These are notnot expected to be found by visual expected to be found by visual inspectioninspection

• Inspection techniques used during Intrusive Inspection techniques used during Intrusive Inspections are Inspections are not appropriate for routine in-servicenot appropriate for routine in-service useuse

• Enhancements to maintenance practices and Enhancements to maintenance practices and reduction in potential fire hazard will reduction in potential fire hazard will mitigatemitigate the the existence of such breechesexistence of such breeches

Intrusive inspectionsIntrusive inspections



ContentsContents

• Background


• Development of new logic






Revised inspection definitionsRevised inspection definitions

General Visual InspectionGeneral Visual Inspection

• Definition now readsDefinition now reads– ““A visual examination of an interior or exterior area, A visual examination of an interior or exterior area,

installation or assembly to detect obvious damage, installation or assembly to detect obvious damage, failure or irregularity. failure or irregularity. This level of inspection is made This level of inspection is made from within touching distance, unless otherwise from within touching distance, unless otherwise specified. A mirror may be necessary to ensure visual specified. A mirror may be necessary to ensure visual access to all surfaces in the inspection area.access to all surfaces in the inspection area. This level This level of inspection is made under normally available lighting of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight conditions such as daylight, hangar lighting, flashlight or droplight and may require removal or opening of or droplight and may require removal or opening of access panels or doors. Stands, ladders or platforms access panels or doors. Stands, ladders or platforms may be required to gain proximity to the area being may be required to gain proximity to the area being checked”checked”



Detailed inspectionDetailed inspection

• Definition now readsDefinition now reads

– ““An intensive An intensive visualvisual examination of a specific item, examination of a specific item, installation or assembly to detect damage failure or installation or assembly to detect damage failure or irregularity. Available lighting is normally supplemented irregularity. Available lighting is normally supplemented with a direct source of good lighting at an interval with a direct source of good lighting at an interval deemed appropriate. Inspection aids such as mirrors, deemed appropriate. Inspection aids such as mirrors, magnifying glasses etc may be necessary. Surface magnifying glasses etc may be necessary. Surface cleaning and elaborate access procedures may be cleaning and elaborate access procedures may be required”required”

• Accomplishment instructions may thus now include Accomplishment instructions may thus now include tactile security checkstactile security checks



• Most GVIs are performed as part of Zonal Most GVIs are performed as part of Zonal Inspection ProgramsInspection Programs

• These may provide an acceptable opportunity to find These may provide an acceptable opportunity to find significant deterioration in wiringsignificant deterioration in wiring

• Guidance on types of deterioration Guidance on types of deterioration expected to be expected to be found and addressedfound and addressed by such inspections has been by such inspections has been developed and will be widely distributed in developed and will be widely distributed in forthcoming Advisory Circular and in training forthcoming Advisory Circular and in training materialmaterial

Inspection effectivenessInspection effectiveness



ContentsContents

• Background



• Revised inspection definitions





Single element dual load path designSingle element dual load path design

• Used in Used in flight control systemsflight control systems to provide load path to provide load path redundancy and thus permit compliance withredundancy and thus permit compliance withFAR 25. 671FAR 25. 671

• Includes features such as ‘tubes within tubes’ and Includes features such as ‘tubes within tubes’ and ‘back to back fittings’‘back to back fittings’

• Degradation and/or failure of one load path Degradation and/or failure of one load path may not may not be visible.be visible. Assurance of Continued Airworthiness Assurance of Continued Airworthiness has been questionedhas been questioned

• Task 3 WG recommended that existing designs are Task 3 WG recommended that existing designs are re-evaluatedre-evaluated using MSG-3 techniques using MSG-3 techniques



ContentsContents

• Background




• Single element dual load path design




Consequences for operatorsConsequences for operators

SummarySummary

• Some detailed wiring inspections will be requiredSome detailed wiring inspections will be required

• Removal of contamination to become normal practiceRemoval of contamination to become normal practice

• Zonal inspection expectations to be better understoodZonal inspection expectations to be better understood

• Protection and cautions to be enhanced and adhered toProtection and cautions to be enhanced and adhered to

• General awareness of wiring issues to be enhancedGeneral awareness of wiring issues to be enhanced

• Sufficient time to be made available for visual inspectionsSufficient time to be made available for visual inspections

• Reassessment of dual load path items may lead to new Reassessment of dual load path items may lead to new taskstasks



ContentsContents

• Background




• Single element dual load path design

• Consequences for operators




Conclusion Conclusion

EZAP developed to enable closer attention to be given to EZAP developed to enable closer attention to be given to wiring during maintenance program developmentwiring during maintenance program development

Operators will need to address the consequences of the Operators will need to address the consequences of the Task 3 activity relating to new tasks, revised inspection Task 3 activity relating to new tasks, revised inspection criteria and enhanced maintenance practicescriteria and enhanced maintenance practices

Taken together, these actions will result in a significantTaken together, these actions will result in a significantenhancement in the condition of wiring installationsenhancement in the condition of wiring installationsTaken together, these actions will result in a significantTaken together, these actions will result in a significantenhancement in the condition of wiring installationsenhancement in the condition of wiring installations

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