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).

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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
ElectricalWiringSystem Manhours 200501-02125
51 - FlightInstruments
44 - Lighting System
42 - Electrical Power System
49 - Misc Utilities (Fire
Detection,etc)
11 - Airframe
14 - FlightControls
13 - Landing Gear
UNK
46 - Fuel System
61
52
72
ours 200501-02125
51 - FlightInstruments
44 - Lighting System
42 - Electrical Power System
49 - Misc Utilities (Fire
Detection,etc)
11 - Airframe
14 - FlightControls
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-hours
1. Flight Instruments
2. Lighting Systems
3. Electrical Power
4. Misc Utilities
5. Airframe
6. Flight Controls
7. Landing Gear
Aircraft Electrical Wiring
Repair Man-Hours by System
(200501 thru 201205)
Aircraft Electrical Wiring Job
Count by System
(200501 thru 201205)
51 - Flight Instruments
44 - Lighting System
42 - Electrical Power System
13 - Landing Gear
11 - Airframe
04 - UNK
46 - Fuel System
14 - Flight Controls
12 - CrewStation System
49 - Misc Utilities (Fire
Detection, etc)
61
72
52
27 - Power Plant
64 - Interphone System
47 - OxygenSystem
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 - CrewStation System
49 - Misc Utilities (Fire
Detection, etc)
61
72
Man-hours
1. Flight Instruments
2. Lighting Systems
3. Electrical Power
4. Misc Utilities
5. Airframe
6. Flight Controls
7. 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
info@lectromec.com
www.lectromec.com
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.