ewis and airworthiness
DESCRIPTION
Presentation given to the AEROSPACE Electrical Systems Expo on April 2, 2014. A short, 17 slide, presentation that looks at several aspects of EWIS (Electrical Wiring Interconnection System).TRANSCRIPT
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Electrical Wiring Interconnection System (EWIS) Handbook A Process to Assess Overall Condition, Service Life Extension
(SLE) and Continued Airworthiness
Lectromec - Michael Traskos
April 2014
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Agenda
• Handbook Overview
• 7 Tasks
– Task 1 – Physical and Function Assessment
– Task 2 – Data Mining
– Task 3 – On-Aircraft Inspection
– Task 4 – EWIS Aging Analysis
– Task 5 – Overall EWIS Assessment
– Task 6 – Action Plan
– Task 7 – Periodic Assessment
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Why?
Source: United States Air Force Aircraft Accident Investigation Board Report - F-22A, T/N 00-4013, 15 November 2012
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Why?
• Create clear recommendations for EWIS sustainment on military aerospace platforms
• Too often fleet management offices had to develop their own methodologies for assessment or base decisions on anecdotal evidence
• Align the EWIS life extension guidelines with industry recommendations and military risk assessment standard practices
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Handbook Basis
• MIL-STD-1798, Mechanical Equipment and Subsystems (MECSIP) Integrity Program
• MIL-STD-516, Airworthiness Certification Criteria
• MIL-STD-882D, Standard Practice For System Safety
• MIL-HDBK-454, General Guidelines For Electronic Equipment
• MIL-HDBK-522, Guidelines For Inspection Of Aircraft Electrical Wiring Interconnect Systems
• JSSG-2009, Air Vehicle Subsystems
• TO 01-1A-14, Installation and Repair Practices for Aircraft Electrical and Electronic Wiring
• AS 50881, Wiring Aerospace Vehicles
• FAA AC43.11B, Chapter 11, Aircraft Electrical Systems
• FAA AC 25.1701-1, Certification of Electrical Wiring Interconnection Systems on Transport Category Airplanes
• FAA AC120-102, Incorporation of Electrical Wiring Interconnection Systems for Continued Airworthiness
• FAA Advisory Circular 120-94 (EWIS training)
• FAA Advisory Circular 25-26 (Standard Wiring Practices Manual)
• FAA Advisory Circular 25-27A (Enhanced zonal analysis procedure – EZAP)
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Overview
Source: MIL-HDBK-525
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Task #1 – Physical and Functional Assessment
Task Objective: Gather EWIS data and perform analysis to identify EWIS failure impact
• Gather EWIS functional data including protection devices, critical circuit paths, and equipment functionality.
• Gather EWIS physical data including environmental, routing and separation information.
• Perform prelim. EWIS component failures aircraft impact assessment and document an aircraft functional hazard assessment.
• Assess potential physical damage from EWIS failures.
Source: MIL-HDBK-525
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
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Task #2 – Data Mining
Task Objective: Gather data to direct on-aircraft inspection and testing activities.
• Collect and analyze EWIS failure and maintenance data and document how it is collected and analyzed
• Review and assess mishap and maintenance databases and applicable Airworthiness Directives (ADs)
• Interview maintenance and engineering support staff
• Examine maintenance and failure data using keyword search (Attachment D provides guidance)
• Review findings, maintenance actions, discrepancies and repairs carried out as part of mandatory or voluntary inspections
• Organize data by zone/station, probability and seriousness of failure
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
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Task #2 – Data Mining
Electrical Wiring System Manhours 200501-02125
51 - Flight Instruments
44 - Lighting System
42 - Electrical Power System
49 - Misc Utilities (Fire Detection, etc)
11 - Airframe
14 - Flight Controls
13 - Landing Gear
UNK
46 - Fuel System
61
52
72
Electrical Wiring System Manhours 200501-02125
51 - Flight Instruments
44 - Lighting System
42 - Electrical Power System
49 - Misc Utilities (Fire Detection, etc)
11 - Airframe
14 - Flight Controls
13 - Landing Gear
UNK
46 - Fuel System
61
52
72
12 - Crew Station System
27 - Power Plant
47 - Oxygen System
64 - Interphone System
71 - Radio Navigation
Misc Systems
Man-hours1. Flight Instruments2. Lighting Systems3. Electrical Power4. Misc Utilities5. Airframe6. Flight Controls7. Landing Gear
Aircraft Electrical Wiring Repair Man-Hours by
System (200501 thru 201205)
Aircraft Electrical Wiring Job Count by System (200501 thru 201205)
Count
51 - Flight Instruments
44 - Lighting System
42 - Electrical Power System
13 - Landing Gear
11 - Airframe
04 - UNK
46 - Fuel System
14 - Flight Controls
12 - Crew Station System
49 - Misc Utilities (Fire Detection, etc)
61
72
52
27 - Power Plant
64 - Interphone System
47 - Oxygen System
03
71 - Radio Navigation
Misc Systems
Count
51 - Flight Instruments
44 - Lighting System
42 - Electrical Power System
13 - Landing Gear
11 - Airframe
04 - UNK
46 - Fuel System
14 - Flight Controls
12 - Crew Station System
49 - Misc Utilities (Fire Detection, etc)
61
72
Man-hours1. Flight Instruments2. Lighting Systems3. Electrical Power4. Misc Utilities5. Airframe6. Flight Controls7. Landing Gear
Source: MIL-HDBK-525
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Task #3 – On-Aircraft EWIS Inspection
Task Objective: Physical inspection to determine EWIS condition and identify areas for EWIS component removal. • Task 1 and 2 finding are used to select zones for
inspection.• Use AS50881 and applicable design/installation
documents for guidance • Develop an inspection checklist for selected
zones• Look for exposed conductors, loss of mechanical
properties, excessive splicing, contamination, discoloration and overheating evidence
• There are three types of inspections that are utilized when performing physical aircraft inspections.
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
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Task #3 – On-Aircraft Assessment
1. A detailed inspection (DET) is an intensive examination of a specific item, installation, or assembly. Inspection aids such as mirrors, flashlights, and magnifying lenses are highly recommended.
2. A general visual inspection (GVI) is a visual examination of an interior or exterior area, installation or assembly. No equipment is removed and the inspector should be within physical touching distance of the equipment.
3. A zonal inspection utilizes a combination of DETs and GVIs, applied to a specific aircraft zone, in order to assess component integrity within the zone. Source: USAF - AFRL
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Task #4 – EWIS Aging Analysis
Task Objective: In laboratory assessment for EWIS component degradation assessment. • Use findings from Tasks 1, 2 and 3 to
select EWIS components to remove
• Conduct electrical, mechanical, chemical and destructive materials analysis as needed
• Assessment may include insulation and conductor integrity, harness, shield and ground termination condition, connector contact integrity and shielding effectiveness, circuit breaker/relay/switch contact integrity, etc.
• Compare condition of materials with new materials
• Apply aging assessment and degradation models to determine remaining life (if available)
XL-ETFE
Polyimide
Composite
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
Photo Source: Lectromec/ Lectromec/ FAA
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Task #5 – Overall EWIS Risk Assessment
Task Objective: Perform EWIS risk assessment and identify areas/systems/components posing the greatest risk to the aircraft.
• Using data collected in Tasks 1 through 5, analyze and provide overall EWIS risk and life assessment
• Apply EWIS risk assessment algorithms that combine failure histories, failure modes and mechanisms, material properties and environmental and maintenance conditions.
• Combine EWIS failure criticality effect on aircraft safety, reliability and availability
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
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Task #5 – Overall EWIS Risk Assessment
• Consider electrical fires and system reliability/availability in overall assessment
• Prepare final risk assessment report
• Identify risk at device, system and aircraft level
Photo Source: MIL-HDBK-525
Component Degradation Impact on Risk
Risk Categorization
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Task #6 – Action Plan
Task Objective: Define actions necessary to reduce EWIS risk.
• Mitigation techniques recommended for EWIS risk reduction:
– Design changes: Identify and develop a mitigation strategy for components with high failure severity values. Once a mitigation strategy is developed, a secondary risk assessment shall be performed to determine the impact of changes to the system
– Replacement: This method should only be considered when design changes can not provide the desired severity values. Replacement should be based on the individual platform needs and constraints
– Maintenance changes: The EWIS inspection program (Task 3) should be directed toward monitoring components with performance deterioration through periodic inspections in hot-spot areas (main drivers of maintenance action)
• Schedule inspections over system life
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
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Task #7 – Periodic Reassessment
Task Objective: Ensure recommendations have been acted upon and setup periodic monitoring to maintain airworthiness.
• Iterative EWIS assessment is used to track the degradation of EWIS components and update replacement/retirement actions.
• This is accomplished by reapplying tasks 1- 6
• EWIS component reassessment should align results with the existing data to allow for direct comparison.
• Reexamination of action plan assessment may require modification of current mitigation techniques
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #4–Lab Eval.
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
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Questions?
+1 (703) 263-7100
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Blog: www.lectromec.com/blog
MIL-HDBK-525 Available for Download: http://quicksearch.dla.mil
Task #1–Analysis
Task #2–Maint. Data
Task #3–Inspection
Task #5–EWIS Risk
Task #6–Mitigation
Task #7–Reassess
Task #4–Lab Eval.