Improvement of Maintenance Criteria - Task 3 1 Improvement of Maintenance Criteria ATSRAC Task 3 presented by T J Harbottle Task 3 Working Group Chairman Seattle - November 2001

Improvement of Maintenance Criteria - Task 3 2 Improvement of maintenance criteria - Task 3 Contents 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

Improvement of Maintenance Criteria - Task 3 3 Improvement of maintenance criteria - Task 3 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 Contents

Improvement of Maintenance Criteria - Task 3 4Background ATSRAC’s Task 3 WG formed in 1999 to identify proposals for the “Improvement of maintenance criteria”ATSRAC’s Task 3 WG formed in 1999 to identify proposals for the “Improvement of maintenance criteria” During 2000, the group assessed sub-tasks associated withDuring 2000, the group assessed sub-tasks associated with – Maintenance program development – Inspection and maintenance task accomplishment – Maintenance practices A list of recommendations were developed and agreed by ATSRAC in Jan 2001A list of recommendations were developed and agreed by ATSRAC in Jan 2001

Improvement of Maintenance Criteria - Task 3 5 Improvement of maintenance criteria - Task 3 Contents Background 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

Improvement of Maintenance Criteria - Task 3 6 Recommendation summary These recommendations include Application of an Enhanced Zonal Analysis ProcedureApplication of an Enhanced Zonal Analysis Procedure Clarification of GVI and Detailed InspectionClarification of GVI and Detailed Inspection Guidance on the expectations of a GVI performed as part of Zonal InspectionGuidance on the expectations of a GVI performed as part of Zonal Inspection Protections and cautions to be observed when performing certain maintenance or servicing tasksProtections and cautions to be observed when performing certain maintenance or servicing tasks The need to re-assess continuous airworthiness of dual load path design features in flight control systemsThe need to re-assess continuous airworthiness of dual load path design features in flight control systems 

Improvement of Maintenance Criteria - Task 3 7 Improvement of maintenance criteria - Task 3 Contents Background Recommendation 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

Improvement of Maintenance Criteria - Task 3 8 Through an iterative process, an Enhanced Zonal Analysis Procedure was developed.Through an iterative process, an Enhanced Zonal Analysis Procedure was developed. Starting point: ATA’s MSG-3 Zonal Analysis Procedure previously used to develop Zonal Inspection ProgramsStarting point: ATA’s MSG-3 Zonal Analysis Procedure previously used to develop Zonal Inspection Programs Development of new logic This had to address the findings from the non-intrusive inspections performed during the Task 1 survey. Its focus was to address wiring installations.This had to address the findings from the non-intrusive inspections performed during the Task 1 survey. Its focus was to address wiring installations. Enhanced zonal analysis procedure 

Improvement of Maintenance Criteria - Task 3 9 Development of new logic

Improvement of Maintenance Criteria - Task 3 10 Development of new logic Many findings related toMany findings related to –Inappropriate or deteriorated repairs –Mechanical damage –Contamination –Inadequate attachment of wires and bundles House keeping issues - most would be evident during existing inspections. They were seen but not addressedHouse keeping issues - most would be evident during existing inspections. They were seen but not addressed Learned complacency needs to be overcome - enhanced awareness is necessaryLearned complacency needs to be overcome - enhanced awareness is necessary Findings analysis 

Improvement of Maintenance Criteria - Task 3 11 Development of new logic Findings analysis (cont’d) 

Improvement of Maintenance Criteria - Task 3 12 Development of new logic Findings analysis (cont’d) 

Improvement of Maintenance Criteria - Task 3 13 Development of new logic Findings analysis (cont’d) 

Improvement of Maintenance Criteria - Task 3 14 Development of new logic Findings analysis (cont’d) 

Improvement of Maintenance Criteria - Task 3 15 Development of new logic Primary concern is the potential fire hazardPrimary concern is the potential fire hazard EZAP must identify tasks to minimize this potentialEZAP must identify tasks to minimize this potential The results must be realisticThe results must be realistic Any new tasks must not increase potential for new discrepanciesAny new tasks must not increase potential for new discrepancies

Improvement of Maintenance Criteria - Task 3 16 Development of new logic EZAP starts with identification of zones containing wiringEZAP starts with identification of zones containing wiring For each zone, the enhanced logic is performed ifFor each zone, the enhanced logic is performed if – Combustible materials may be present or –Wiring is installed close to primary and back-up hydraulic/mechanical flight controls It will always be applied in flight compartment and avionics / electronic baysIt will always be applied in flight compartment and avionics / electronic bays Application process 

Improvement of Maintenance Criteria - Task 3 17 Development of new logic NO wiring portion Is wiring close to primary and back-up hydraulic or mechanical flight controls ? Combustible materials in zone ? (f) Zone contains wiring? YES (e) non-wiring portion NO (i)

Improvement of Maintenance Criteria - Task 3 18 Development of new logic Logic first leads to identification of task(s) to address actual or potential contaminationLogic first leads to identification of task(s) to address actual or potential contamination These may includeThese may include –Removal of heavy accumulations of dust/lint –Drying pools of fluids –Cleaning/discard of contaminated insulation blankets –Detailed inspection of high pressure hydraulic lines in close proximity to wiring Application process (cont’d) 

Improvement of Maintenance Criteria - Task 3 19 Development of new logic Define Task and Interval Is there an effective task to significantly reduce the likelihood of accumulation of combustible materials? YES (h) (g)

Improvement of Maintenance Criteria - Task 3 20 Development of new logic Logic then identifies wiring inspection tasksLogic then identifies wiring inspection tasks Inspection level determined with consideration toInspection level determined with consideration to – Potential effect of localized fire on adjacent systems – Size of inspection area – Density of installed equipment Inspection interval determined with consideration toInspection interval determined with consideration to – Potential for accidental damage – Environment Application process (cont’d) 

Improvement of Maintenance Criteria - Task 3 21 Development of new logic Wiring inspection task determination Inspection level definition Inspection level verification Interval determination See Figure 6-5-2

Improvement of Maintenance Criteria - Task 3 22 Development of new logic In conclusion, for each zone, the enhanced logicIn conclusion, for each zone, the enhanced logic –Permits identification of Tasks to reduce likelihood of significant build-up of combustible materialsTasks to reduce likelihood of significant build-up of combustible 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 zoneor –Confirms that existing zonal inspection is adequate Enhanced logic: summary  Any new tasks identified will need to be included in the Systems and Power Plant programsAny new tasks identified will need to be included in the Systems and Power Plant programs

Improvement of Maintenance Criteria - Task 3 23 Development of new logic Some breeches were discovered in the wiring insulationSome breeches were discovered in the wiring insulation These are not expected to be found by visual inspectionThese are not expected to be found by visual inspection Inspection techniques used during Intrusive Inspections are not appropriate for routine in-service useInspection techniques used during Intrusive Inspections are not appropriate for routine in-service use Enhancements to maintenance practices and reduction in potential fire hazard will mitigate the existence of such breechesEnhancements to maintenance practices and reduction in potential fire hazard will mitigate the existence of such breeches Intrusive inspections 

Improvement of Maintenance Criteria - Task 3 24 Improvement of maintenance criteria - Task 3 Contents Background Recommendation summary Development 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

Improvement of Maintenance Criteria - Task 3 25 Revised inspection definitions General Visual Inspection Definition now readsDefinition now reads –“A visual examination of an interior or exterior area, installation or assembly to detect obvious damage, failure or irregularity. This level of inspection is made from within touching distance, unless otherwise specified. A mirror may be necessary to ensure visual access to all surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight or droplight and may require removal or opening of access panels or doors. Stands, ladders or platforms may be required to gain proximity to the area being checked” 

Improvement of Maintenance Criteria - Task 3 26 Revised inspection definitions Detailed inspection Definition now readsDefinition now reads –“An intensive visual examination of a specific item, installation or assembly to detect damage failure or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an interval deemed appropriate. Inspection aids such as mirrors, magnifying glasses etc may be necessary. Surface cleaning and elaborate access procedures may be required” Accomplishment instructions may thus now include tactile security checksAccomplishment instructions may thus now include tactile security checks 

Improvement of Maintenance Criteria - Task 3 27 Revised inspection definitions Most GVIs are performed as part of Zonal Inspection ProgramsMost GVIs are performed as part of Zonal Inspection Programs These may provide an acceptable opportunity to find significant deterioration in wiringThese may provide an acceptable opportunity to find significant deterioration in wiring Guidance on types of deterioration expected to be found and addressed by such inspections has been developed and will be widely distributed in forthcoming Advisory Circular and in training materialGuidance on types of deterioration expected to be found and addressed by such inspections has been developed and will be widely distributed in forthcoming Advisory Circular and in training material Inspection effectiveness 

Improvement of Maintenance Criteria - Task 3 28 Improvement of maintenance criteria - Task 3 Contents Background Recommendation summary Development of new logic Revised inspection definitions Single element dual load path designSingle element dual load path design Consequences for operatorsConsequences for operators ConclusionConclusion

Improvement of Maintenance Criteria - Task 3 29 Single element dual load path design Used in flight control systems to provide load path redundancy and thus permit compliance with FAR Used in flight control systems to provide load path redundancy and thus permit compliance with FAR Includes features such as ‘tubes within tubes’ and ‘back to back fittings’Includes features such as ‘tubes within tubes’ and ‘back to back fittings’ Degradation and/or failure of one load path may not be visible. Assurance of Continued Airworthiness has been questionedDegradation and/or failure of one load path may not be visible. Assurance of Continued Airworthiness has been questioned Task 3 WG recommended that existing designs are re-evaluated using MSG-3 techniquesTask 3 WG recommended that existing designs are re-evaluated using MSG-3 techniques

Improvement of Maintenance Criteria - Task 3 30 Single element dual load path design A300 artificial feel and trim limit Inner shaft Main shaft Bellcrank assembly

Improvement of Maintenance Criteria - Task 3 31 Improvement of maintenance criteria - Task 3 Contents Background Recommendation summary Development of new logic Revised inspection definitions Single element dual load path design Consequences for operatorsConsequences for operators ConclusionConclusion

Improvement of Maintenance Criteria - Task 3 32  Consequences for operators Summary 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 tasksReassessment of dual load path items may lead to new tasks

Improvement of Maintenance Criteria - Task 3 33 Improvement of maintenance criteria - Task 3 Contents Background Recommendation summary Development of new logic Revised inspection definitions Single element dual load path design Consequences for operators ConclusionConclusion

Improvement of Maintenance Criteria - Task 3 34 Improvement of maintenance criteria - Task 3 Conclusion EZAP developed to enable closer attention to be given to wiring during maintenance program development Operators will need to address the consequences of the Task 3 activity relating to new tasks, revised inspection criteria and enhanced maintenance practices Taken together, these actions will result in a significant enhancement in the condition of wiring installations