Standard Practice for Inspection of Aircraft Electrical Wiring Systems

SIGNIFICANCE AND USE
4.1 The term “electrical system” as used in this practice means those parts of the aircraft that generate, distribute, and use electrical energy, including their support and attachments.  
4.2 The satisfactory performance of an aircraft is dependent upon the continued reliability of the electrical system.  
4.3 Damaged wiring or equipment in an aircraft, regardless of how minor it may appear to be, cannot be tolerated. It is, therefore, important that maintenance be accomplished using the best techniques and practices to minimize the possibility of failure.  
4.4 When inspecting and evaluating EWIS, improper wiring, routing, or repairs shall be corrected regardless of the origin of the error.  
4.5 This practice is not intended to supersede or replace any government specification or specific manufacturer’s instruction regarding electrical system inspection and repair
SCOPE
1.1 This practice covers basic inspection procedures for electrical wiring interconnect systems for aircraft electrical wiring systems.  
1.2 This practice is not intended to replace any instructions for continued airworthiness published by the aircraft or accessory manufacturer or type design holder.  
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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Publication Date
31-May-2019
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2696 − 14 (Reapproved 2019)
Standard Practice for
Inspection of Aircraft Electrical Wiring Systems
This standard is issued under the fixed designation F2696; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.3 SAE Documents:
SAE ARP1870 Aerospace Systems Electrical Bonding and
1.1 This practice covers basic inspection procedures for
Grounding for Electromagnetic Compatibility and Safety
electrical wiring interconnect systems for aircraft electrical
SAE Aerospace ARP5583 Guide to Certification of Aircraft
wiring systems.
in a High Intensity Radiated Field (HIRF) Environment
1.2 This practice is not intended to replace any instructions
for continued airworthiness published by the aircraft or acces-
3. Terminology
sory manufacturer or type design holder.
3.1 Acronyms:
1.3 The values stated in inch-pound units are to be regarded 3.1.1 EWIS—electrical wiring interconnection system
as standard. The values given in parentheses are mathematical
3.1.2 HIRF—high-intensity radiated fields
conversions to SI units that are provided for information only
3.1.3 ICA—instructions for continued airworthiness
and are not considered standard.
3.1.4 LRU—line-replaceable unit
1.4 This standard does not purport to address all of the
3.1.5 MS—military standard
safety concerns, if any, associated with its use. It is the
3.1.6 MTBF—mean time between failures
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1.7 PTFE—polytetrafluoroethylene
mine the applicability of regulatory limitations prior to use.
3.1.8 RF—radio frequency
1.5 This international standard was developed in accor-
3.1.9 STC—supplemental type certificate (Federal Aviation
dance with internationally recognized principles on standard-
Administration)
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4. Significance and Use
mendations issued by the World Trade Organization Technical
4.1 The term “electrical system” as used in this practice
Barriers to Trade (TBT) Committee.
means those parts of the aircraft that generate, distribute, and
use electrical energy, including their support and attachments.
2. Referenced Documents
2 4.2 The satisfactory performance of an aircraft is dependent
2.1 Military Standard:
upon the continued reliability of the electrical system.
MIL-C-85049 Connector Accessories, Electrical, General
4.3 Damaged wiring or equipment in an aircraft, regardless
Specification for
3 of how minor it may appear to be, cannot be tolerated. It is,
2.2 FAA Guidance Material:
therefore, important that maintenance be accomplished using
FAA Advisory Circular 33.4-3 Instructions for Continued
the best techniques and practices to minimize the possibility of
Airworthiness; Aircraft Engine High Intensity Radiated
failure.
Fields (HIRF) and Lightning Protection Features
4.4 When inspecting and evaluating EWIS, improper
wiring, routing, or repairs shall be corrected regardless of the
origin of the error.
This practice is under the jurisdiction of ASTM Committee F39 on Aircraft
Systems and is the direct responsibility of Subcommittee F39.02 on Inspection,
4.5 This practice is not intended to supersede or replace any
Alteration, Maintenance, and Repair.
government specification or specific manufacturer’s instruction
Current edition approved June 1, 2019. Published June 2019. Originally
regarding electrical system inspection and repair
approved in 2008. Last previous edition approved in 2014 as F2696–14. DOI:
10.1520/F2696–14R19.
Available from the U.S. Government Publishing Office, 732 N. Capitol Street
NW, Washington, DC 20401, http://www.gpo.gov.
3 4
Available from Federal Aviation Administration (FAA), 800 Independence Available from SAE International (SAE), 400 Commonwealth Dr.,Warrendale,
Ave., SW, Washington, DC 20591, http://www.faa.gov. PA 15096, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2696 − 14 (2019)
5. Causes of Wire Degradation 6.1.3 Misalignment of electrically driven equipment;
6.1.4 Poor electrical bonding (broken, disconnected, or
5.1 The following are considered the principal causes of
corroded bonding strap) and grounding, including evidence of
wiring degradation and should be used to help focus mainte-
corrosion;
nance programs:
6.1.5 Dirty equipment and connections;
5.1.1 Vibration—High-vibration areas tend to accelerate
degradation over time resulting in “chattering” contacts and 6.1.6 Improper, broken, inadequately supported wiring and
intermittent symptoms. High vibration of tie-wraps or string
conduit, loose connections of terminals, and loose ferrules;
ties can cause damage to insulation. In addition, high vibration
6.1.7 Poor mechanical or cold solder joints;
will exacerbate any existing wire insulation cracking.
6.1.8 Condition of circuit breaker and fuses;
5.1.2 Moisture—High-moisture areas generally accelerate
6.1.9 Insufficient clearance between exposed current-
corrosion of terminals, pins, sockets, and conductors. Note that
carrying parts and ground or poor insulation of exposed
wiring installed in clean, dry areas with moderate temperatures
terminals;
appears to hold up well.
6.1.10 Broken or missing safety wire, broken bundle lacing,
5.1.3 Maintenance—Scheduled and unscheduled mainte-
cotter pins, and so forth;
nance activities, if done improperly, may contribute to long-
6.1.11 Operational check of electrically operated equipment
term problems and degradation of wiring. Metal shavings and
such as motors, inverters, generators, batteries, lights, protec-
debris have been discovered on wire bundles after
tive devices, and so forth;
maintenance, repair, or alteration work has been performed.
6.1.12 Condition of electric lamps; and
Extra attention shall be given to EWIS inspections around
6.1.13 Missing safety shields on exposed high-voltage ter-
areas of previous aircraft maintenance, repair, or alterations.
5.1.4 Repair—Since wire splices are more susceptible to minals (that is, 115/200 V ac).
degradation, arcing, and overheating, extra care shall be given
6.2 Functional Check of Standby or Emergency
when inspecting repaired wiring.
Equipment—Anaircraftshouldhavefunctionaltestsperformed
5.1.5 Alterations—Alterations introduce another area for
at regular intervals as prescribed by the manufacturer.
enhanced scrutiny for similar reasons as repairs. In addition, an
6.3 Bus Bars—Annually check bus bars for general
alteration may not be documented in the aircraft Instructions
condition, cleanliness, and security of all attachments and
for Continued Airworthiness and therefore need independent
terminals. Grease, corrosion, or dirt on any electrical junction
inspection and a concern for proper wiring, attachments,
may cause the connections to overheat and eventually fail. Bus
mounting, and wiring routing.
bars that exhibit corrosion, even in limited amounts, shall be
5.1.6 Indirect Damage—Events such as pneumatic duct
disassembled, cleaned and brightened, and reinstalled.
ruptures or duct clamp leakage can cause damage that, while
not initially evident, can later cause wiring problems. When
6.4 Generating System—Inspect generator(s)/alternator(s)
events such as these occur, surrounding EWIS shall be care-
for general condition, cleanliness, and security of attachment
fully inspected to ensure that there is no damage or potential
and terminals. Any sign of overheating terminals or wiring is
for damage evident. Indirect damage caused by these types of
reason for rejection. Inspect drive belts for condition and wear.
eventsmaybebrokenclampsorties,brokenwireinsulation,or
Replace any belt showing signs of abnormal wear or overheat-
even broken conductor strands. In some cases, the pressure of
ing. Inspect brushes for proper condition and wear patterns.
the duct rupture may cause wire separation from the connector
Inspect brush holders for condition and signs of arcing or
or terminal strip.
overheating. Inspect voltage regulation components and wiring
for condition and security. Inspect generator(s)/alternator(s)
6. Procedure
warning system for condition and operation.
6.1 Inspection and Operation Checks—Inspect equipment,
6.5 Battery Inspection—Battery inspection procedures vary
electrical assemblies, and wiring installations for damage,
with the types of chemical technology and physical construc-
general condition, and proper functioning to ensure the con-
tion. Always follow the battery manufacturer’s approved pro-
tinued satisfactory operation of the electrical system. Adjust,
cedures.Batteryperformanceatanytimeinagivenapplication
repair, overhaul, and test electrical equipment and systems in
will depend upon the battery’s age, state of health, state of
accordance with the recommendations and procedures in the
charge, and mechanical integrity.
aircraft or component manufacturer’s maintenance instructions
6.5.1 Aircraft Battery Inspection:
or both. Replace components of the electrical system that are
6.5.1.1 Inspect battery sump jar (if installed) and lines for
damaged or defective with identical parts, aircraft manufactur-
condition and security.
er’s approved equipment, or its equivalent to the original in
6.5.1.2 Inspect battery terminals and quick-disconnect plugs
operating characteristics, mechanical strength, and environ-
and pins for evidence of corrosion, pitting, arcing, and burns.
mental specifications. A list of suggested problems to look for
Clean as required. Inspect battery cables for condition and
and checks to be performed are:
signs of chafing.
6.1.1 Damaged, discolored, or overheated equipment,
connections, wiring, and installations; 6.5.1.3 Inspect battery drain and vent lines for restriction,
6.1.2 Excessive heat or discoloration at high-current- deterioration, and security. Battery drain areas shall be checked
carrying connections; for signs of structure corrosion.
F2696 − 14 (2019)
6.5.1.4 Routine preflight and postflight inspection proce- (61 cm), except when contained in troughs, ducts, or conduits.
dures shall include observation for evidence of physical The supporting devices shall be of a suitable size and type with
damage, loose connections, and electrolyte loss. the wires and cables held securely in place without damage to
6.5.1.5 Perform capacity performance test of battery per the insulation. Inspect wire and cable clamps for proper
tightness. Where cables pass through structure or bulkheads,
manufacturer’s instructions to ensure continued airworthiness.
inspect for proper clamping and grommets. Inspect for suffi-
6.5.1.6 Inspect battery warning system components (if in-
cientslackbetweenthelastclampandtheelectronicequipment
stalled) for condition and operation.
to prevent strain at the cable terminals and to minimize adverse
6.5.1.7 For nickel-cadmium battery installations, inspect
effects on shock-mounted equipment.
battery temperature sensing, over-temperature warning, and
battery failure-sensing systems for proper operation. Inspect 6.8.2 Mechanical standoffs shall be used to maintain clear-
ance between wires and structure. Using tape or tubing is not
the means for disconnecting the battery(ies) for the charging
source in the event of an over-temperature condition. acceptable as an alternative to standoffs for maintaining clear-
ance.
6.6 Emergency Power Supply/Battery Inspection:
6.8.3 Phenolic blocks, plastic liners, or rubber grommets are
6.6.1 Emergency power supplies or batteries shall be in-
installed in holes, bulkheads, floors, or structural members
spected and functionally tested per the manufacturer instruc-
where it is impossible to install off-angle clamps to maintain
tions.
wiring separation. Inspect the EWIS to ensure separation
6.6.2 Perform capacity performance tests of batteries per
between the wire and the hole, bulkhead, floor, or structural
manufacturer’s instructions to ensure continued airworthiness.
member.
6.6.3 Inspect installations for condition, security, and rout-
6.8.4 Wires and cables in junction boxes, panels, and
ing of wiring.
bundles are properly supported and laced to provide proper
6.7 Electrical Switch Inspection:
grouping and routing.
6.7.1 Special attention should be given to electrical circuit
6.8.5 Clamp-retaining screws are properly secured so that
switches, especially the spring-loaded type, during the course
the movement of wires and cables is restricted to the span
of normal airworthiness inspection. An internal failure of the
between the points of support and not on soldered or mechani-
spring-loaded type may allow the switch to remain closed even
cal connections at terminal posts or connectors.
though the toggle or button returns to the OFF position. During
6.8.6 Wire and cables are properly supported and bound so
inspection, attention should also be given to the possibility that
that there is no interference with other wires, cables, and
an unapproved switch substitution may have been made.
equipment.
6.7.1.1 With the power off, suspect aircraft electrical
6.8.7 Wires and cables are adequately supported to prevent
switches should be checked in the ON position for opens (high
excessive movement in areas of high vibration.
resistance) and in the OFF position for shorts (low resistance)
6.8.8 Insulatingtubingissecuredbytying,tiestraps,orwith
with an ohmmeter.Apower-on check can be made by checking
clamps.
the voltage drop across the switch. A voltage drop across the
6.8.9 Continuous lacing (spaced 6 in. (15 cm) apart) is not
switch indicates abnormal internal resistance of the switch
used except in panels and junction boxes where this practice is
contacts.
optional. When lacing is installed in this manner, outside of
6.7.1.2 Any abnormal side-to-side movement of the switch
junction boxes, it shall be removed and replaced with indi-
should be an alert to imminent failure even if the switch tested
vidual loops.
was shown to be acceptable with an ohmmeter.
6.8.10 Do not use tapes (such as friction or plastic tape) that
6.7.1.3 When a switch is activated, it should have a notice-
will dry out in service, produce chemical reactions with wire or
able detent feel when switched. If a switch does not have a
cable insulation, or absorb moisture.
detent
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