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Improvement of Maintenance Criteria ATSRAC Task 3 presented by T J Harbottle

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. Contents. Background Recommendation summary Development of new logic Revised inspection definitions

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Improvement of Maintenance Criteria ATSRAC Task 3 presented by T J Harbottle

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

  2. 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 • Conclusion

  3. 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 • Conclusion

  4. Background • 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 with • Maintenance program development • Inspection and maintenance task accomplishment • Maintenance practices • A list of recommendations were developed and agreed by ATSRAC in Jan 2001

  5. 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 • Conclusion

  6. Recommendation summary  These recommendations include • Application of an Enhanced Zonal Analysis Procedure • Clarification of GVI and Detailed Inspection • Guidance on the expectations of a GVI performed as part of Zonal Inspection • Protections 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 systems

  7. 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 • Conclusion

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

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

  10. Development of new logic • Primary concern is the potential fire hazard • EZAP must identify tasks to minimize this potential • The results must be realistic • Any new tasks must not increase potential for new discrepancies

  11. Development of new logic  Application process • EZAP starts with identification of zones containing wiring • For 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 bays

  12. Development of new logic  Application process (cont’d) • Logic first leads to identification of task(s) to address actual or potential contamination • These 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

  13. Development of new logic  Application process (cont’d) • Logic then identifies wiring inspection tasks • Inspection 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 to • Potential for accidental damage • Environment

  14. Development of new logic  Enhanced logic: summary • In conclusion, for each zone, the enhanced logic • Permits identification of • Tasks to reduce likelihood of significant build-up of combustible materials • Detailed Inspections of some or all wiring in a zone • Standalone GVIs of some or all wiring in a zone or • Confirms that existing zonal inspection is adequate • Any new tasks identified will need to be included in the Systems and Power Plant programs

  15. Development of new logic  Intrusive inspections • Some breeches were discovered in the wiring insulation • These are not expected to be found by visual inspection • Inspection techniques used during Intrusive Inspections are not appropriate for routine in-serviceuse • Enhancements to maintenance practices and reduction in potential fire hazard will mitigate the existence of such breeches

  16. 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 • Conclusion

  17. Revised inspection definitions  General Visual Inspection • Definition 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”

  18. Revised inspection definitions  • “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” Detailed inspection • Definition now reads • Accomplishment instructions may thus now include tactile security checks

  19. Revised inspection definitions  Inspection effectiveness • Most GVIs are performed as part of Zonal Inspection Programs • These 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 material

  20. 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 • Conclusion

  21. Single element dual load path design • Used in flight control systems to provide load path redundancy and thus permit compliance withFAR 25. 671 • 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 questioned • Task 3 WG recommended that existing designs are re-evaluated using MSG-3 techniques

  22. 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 • Conclusion

  23. Consequences for operators  Summary • Some detailed wiring inspections will be required • Removal of contamination to become normal practice • Protection and cautions to be enhanced and adhered to • Zonal inspection expectations to be better understood • Sufficient time to be made available for visual inspections • General awareness of wiring issues to be enhanced • Reassessment of dual load path items may lead to new tasks

  24. 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 • Conclusion

  25. 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 significantenhancement in the condition of wiring installations

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