The document provides a comprehensive handbook on assessing the condition and service life extension of Electrical Wiring Interconnection Systems (EWIS) in military aerospace platforms. It outlines a structured approach, detailing seven key tasks including data collection, physical inspections, aging analysis, risk assessment, and action planning to ensure continued airworthiness. The guidance aligns with military standards and aims to create consistent methodologies for fleet management and safety assessments.

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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.