ewis job-aid 2.0 508-accessible

8/2/2019 EWIS Job-Aid 2.0 508-Accessible

1/67

Slide1:AircraftElectricalWiringInterconnectSystem(EWIS)BestPractices

JobAid

Revision: 2.0

[Speakernotes]

Thisjobaidcoversapplicable14CFRpart25aircraft(althoughitisalsowidelyacceptablefor

usewithothertypesofaircraftsuchasmilitary,smallairplanes,androtorcraft). Thisjobaid

addressespolicy;industryEWISpractices;primaryfactorsassociatedwithEWISdegradation;

informationonTC/STCdatapackagerequirements;EWISselectionandprotection;routing,

splicingandterminationpractices;andEWISmaintenanceconcepts (includinghowtoperform

aEWISgeneralvisualinspection). ThejobaidalsoincludesnumerousactualaircraftEWIS

photosandexamples.

[Endspeakernotes]

Slide2:AdditionalNotes

Thisslidedoesnotpertaintothisaccessibleversion:

Thispresentationcontainsadditionalspeakernotesformostslides. Itsadvisabletoreadthesenoteswhileviewingtheslidepresentation

Slide3:PrintingtheAdditionalNotes

Thisslidedoesnotpertaintothisaccessibleversion:

To

print

the

slides

and

accompanying

speaker

notes:

NavigatebacktotheFAAAircraftCertificationjobaidswebpage OpenandprintPrintableSlidesandNotes.

Slide4:Background

1. WhytheneedforEWISbestpracticesJobAid?a. Accident/IncidentServiceHistoryb. AgingTransportSystemsRulemakingAdvisoryCommittee(ATSRAC)c. EnhancedAirworthinessProgramforAirplaneSystem(EAPAS)d. EAPASRuleMaking

[Speakernotes]

Historically,wiringandassociatedcomponentswereinstalledwithoutmuchthoughtgivento

theagingaspects:

Fitandforget. Unanticipatedfailuremodesandtheirseverity.


2/67

Arctracking. Arcing. Insulationflashover.

Maintenanceprogramsoftendidnotaddresstheseagingaspects. Servicehistoryalsoindicates

thatForeignObjectDamage(FOD)suchasdrillshavings,causticliquids,etc.doescauseEWIS

degradationthat

can

lead

to

EWIS

faults.

[Endspeakernotes]

Slide5:Introduction

Late1980s,wiringsafetyconcernsraisedduetoaccidents&incidents

Investigationsfoundcommondegradingfactorsinairplaneelectricalwiringsystems

Investigationintowiring

issuesdonebyindustry,

civil

aviation

authorities,

othergovernment

agencies

[Speakernotes]

Theagingissuesinwiringsystemsweremadeknownbythefollowing:

Inthelate1980s,wiringsafetyconcernswereraisedduetoaccidents&incidents Investigationsfoundcommondegradingfactorsinairplaneelectricalwiringsystems Investigationintowiringissuesdonebyindustry,civilaviationauthorities,government

agencies

[Endspeakernotes]

Slide6:WiringInvestigationFindings

Design Maintenance Operation Training Repair Installation

[Speakernotes]

Aslistedhere,theinvestigationoftheaircraftwiringrevealedthereareseveralfactors,

togetherwithtime,thatplayaroleinwiringdegradation.

[Endspeakernotes]


3/67

Slide7:AgingTransportSystemsRulemakingAdvisoryCommittee

(ATSRAC)PhaseI

TaskedtodevelopandproposerecommendationsforairworthinessenhancementstotheFAA.

TaskscompletedandreportsapprovedbyATSRACinJanuary2001.PhaseII

TaskedtodevelopedandproposeairworthinessenhancementsbasedontherecommendationsdevelopedinPhaseI.

TaskscompletedandreportsapprovedbyATSRACinJanuary2003.PhaseIII

TaskedtoassistFAAwiththeimplementationoftheenhancementsdevelopedinPhaseII.

[Speakernotes]

AgingTransport

Systems

Rulemaking

Advisory

Committee

PhaseIThefollowingtaskswereundertakenbyATSRACinthisphasefordevelopingand

proposingrecommendationsforairworthinessenhancementstotheFAA:

Samplinginspectionofthefleet

Reviewoffleetservicehistory

Improvementofmaintenancecriteria

Reviewandupdatestandardpracticeforwiring

Reviewaircarrierandrepairstationinspectionandrepairtrainingprograms

PhaseIIThefollowingtaskswereundertakenbyATSRACinthisphasetodevelopand

proposeairworthinessenhancementsbasedontherecommendationsdevelopedinPhaseI:

Improving

wire

system

certification

requirements

Enhancingwiringmaintenanceproceduresandinstructions

Enhancingandaugmentcurrenttrainingprograms

StandardizingtheformatofStandardWiringPracticesManual

Studyofagingissuesinsmalltransportairplaneselectricalwiring

PhaseIII ThefollowingtasksarecurrentlyundertakenbyATSRACinthisphasetoassistFAA

withtheimplementationoftheenhancementsdevelopedinPhaseII:

Provideassistanceinimplementationoftheairworthinessenhancementsand,ifrequested,

developalternativestorulemakingforimplementationoftrainingandmaintenance

enhancements.

Assistinreviewandimplementationofnewtechnologiesdevelopedformitigatingtheaging

issuesin

aircraft

wiring

systems.

Studyanddevelopenhancementsforwiringmaintenanceproceduresforsmalltransport

airplanes(withapassengercapacitybetween6to30andlessthan7,500poundpayload).

[Endspeakernotes]


4/67

Slide8:Routing/ChafingIn-ServiceExamples

[Graphic]

Wireschafingagainstmetalframeandchaffngagainsteachother

[Endgraphic]

[Speakernotes]

Thesephotosshowexamplesoffindings.Theseexamplesshowthepotentialforchafingand

arcing.

[Endspeakernotes]

Slide9:AccumulationofDirtandLint

[Graphic]

Wirescoveredindirtandlint

[Endgraphic]

[Speakernotes]

Accumulationofdirtandlintcreateapotentialforsmokeandfire,makinginspectionofthe

EWISimpossible.

[Endspeakernotes]

Slide10:CoilandStowIn-ServiceExample/Result

[Graphic]

Cutwireswithendsexposedandcutantennathatisexposed

[Endgraphic]

[Speakernotes]

Thisslideshowsanexampleofimproperterminationofunusedwires. Ontheleftside,there

arenoterminationcapsanditsimproperlystowed.

Ontherightsideisaphotoofanimpropermaintenanceaction. Coaxialcablewasleft

attachedtoanantennainsteadofbeingremovedinitsentiretyatleastitshouldhavebeen

detachedfromtheantenna. Consequently,lightningattachedtotheantenna,traveledalong

theEWIS,andcausedafireinthecabin.

[Endspeakernotes]

Slide11:BendRadiusProblemIn-ServiceExample

[Graphic]

Wiresbent180degreesandbundledtogether

[Endgraphic]

[Speakernotes]


5/67

Thisphotoshowsanimproperbendradiusinstallationofelectricalwire.Theproperbend

radiusforwireonaircraftshouldbe10timestheoutsidediameterofthelargestdiameterwire

inthebundleforonesidesupported(3timesfortwosidessupported.) Standardindustrial

practiceandisinAC43.131bandStandardWiringPracticesManual(SWPM).

[Endspeakernotes]

Slide12:ArcingEvent

[Graphic]

Arcingresultswithterminalsandwires

[Endgraphic]

[Speakernotes]

Thesephotosillustrateanimpropermaintenanceactioncausedwhentheairplanes

airworthinesscertificatewasrelocated. Theattachscrewpenetratedthepowercables. The

FAA

maintenance

inspector

riding

on

the

jump

seat

caught

his

clothing

on

fire.

Thearcingevent,whichoriginatedfrominsidetheelectricalpowercenter,burnedahole

throughtheleftsideofthehallway(lookingforward)betweenthecockpitandcabin.

[Endspeakernotes]

Slide13:EffectofImproperMaintenance

[Graphic]

Topshowschafingwirescausedconduitburnthroughongeneratedpowerfeederinconduit.

Thebottomshowsthatheatfromarcingcausedholesinfuelline.

[Endgraphic]

[Speakernotes]

Theleftsideofthisphotoshowsfailureofwireduetochafinginsideametallicconduit.

Createdanarc,whichcreatedholesinthefuellinebelowtheconduit. Causedbyimproperly

replacinganexistingpowerfeeder.

[Endspeakernotes]

Slide14:EffectofPoorDesign

[Graphic]

Burnholesonsideofairplaneandinthefloorunderapassengerseat

[Endgraphic]

[Speakernotes]

ThisshowsarcingduetolavatoryservicinglinesleakingondamagedEWIS,creatinganarcthat

causedafirethatledtoextensivedamageinsideandoutsideoftheairplane.Businessclass

lavatorydripshieldnotinstalledwatershortedcannonpluginwirebundlebelowdeck.

Maintenance,design,training,operationsallneedimprovement.


6/67

[Endspeakernotes]

Slide15:PreviousRegulationsInadequate

Previousregulationsfellshortofprovidingspecificwiringrelatedrequirements. Specificwiringrelatedrequirementsneededtobeincludedincertificationand

operationalregulations.

Slide16:CultureShift: EAPASSafetyInitiative

RecognizingimportanceofEWISinsafeoperationofairplanesleadstobeingmoreproactive;FAAis

o Treatingwiringasasystemo MandatingDAHsupportoftheinitiativeo IntegratingFAAlinesofbusiness;

jointAFS/AIRactivity;andcooperationwith&betweenDAHsandoperators

[Speakernotes]

Tocompletelyandthoroughlyaddresstheagingissuesinaircraftwiringrequiredaculturalshift

comprisingof:

Recognizingimportanceofelectricalwiringinsafeoperationofairplanesleadstobeingmore

proactive;FAAis

Treatingwiringasasystem MandatingDAHsupportoftheinitiative IntegratingFAAlinesofbusiness:

jointAFS/AIRactivity;andcooperationwith&betweenDAHsandoperators

[Endspeakernotes]

Slide17:GoalofEPASRule

Bannerwithmotto:Enhancesafetybyimprovingallaspectsofaircraftelectricalwiring

Goalisbasedono Industry/governmentcommitteedatadriven

recommendations

o Maximizingharmonization[Speakernotes]

ThegoalofEAPASwastoenhancesafetybyimprovingallaspectsofaircraftelectricalwiring

Goalis

based

on

Industry/governmentcommitteedatadrivenrecommendations

MaximizingharmonizationwithinternationalauthoritiesSonowyouhopefullyhaveabetterunderstandingofthehistorybehindtheEAPASrulemaking

andhowitcameintobeing.WearenextgoingtoprovideadefinitionforanEWIS.

[Endspeakernotes]


7/67

Slide18:EWIS

E Electrical

W Wiring

IInterconnection

S System

[Speakernotes]

Wiringneedstobetreatedasanimportantsystemonairplanes.Wiringisnowreferredtoas

theElectricalWiringInterconnectionSystem(EWIS).

[Endspeakernotes]

Slide19:EWISDefinition

AnEWIS

isis

[per

new

25.1701(a)]:

Anywire,wiringdevice,orcombinationofthese,includingterminationdevices,installedin

anyareaoftheairplaneforthepurposeoftransmittingelectricalenergybetweentwoormore

intendedterminationpoints....

Slide20:EEWWIISSiissnotnot[25.1701(a)]

Electricalequipmentoravionicsqualifiedtoacceptableenvironmentalconditionsandtestingprocedures

Portable

electrical

devices

not

part

of

airplanes

type

design

Fiberoptics

Slide21:KeyPointtoRemember...

WWiirreeaannddaassssoocciiaatteeddccoommppoonneennttssnnoowwttrreeaatteeddaassaannaaiirrppllaanneessyysstteemm

Slide22:EWISDegradationFactors

[Graphic]

Inthecenter,EWISDegradationsurroundedPhysicalProperties,Age,Installation,Maintenance

andEnvironmentpointingintoEWISDegradation.

[Endgraphic]

[Speakernotes]

EWISdegradation


8/67

EWISdegradationisaprocessthatisafunctionofseveralvariables;agingisonlyoneofthese. OthermainfactorsthatinfluenceEWISdegradationarethe:

Environmentinwhichitisinstalled.

PhysicalpropertiesoftheEWIS.

ActualphysicalinstallationoftheEWIS.

Maintenance(cleaning

and

repair)

of

the

EWIS.

CharacteristicsofagingEWIS

ThemannerinwhichEWISdegradesisthereforedependentupontheEWIStype,howitwasoriginallyinstalled,theoveralltimeandenvironmentexposedtoin

service,andhowtheEWISwasmaintained.

ServicehistoryshowsthathowtheEWISisinstalledhasadirecteffectonEWISdegradation. Inotherwords,EWISthatisnotselectedorinstalledproperlyhas

anincreasedpotentialtodegradeatanacceleratedrate. Therefore,good

aircraftEWISpracticesarefundamentalrequirementsforEWIStoremainsafely

intact.

[Endspeakernotes]

Slide23:CausesofEWISDegradation

Vibration Moisture Maintenance

[Speakernotes]

VibrationHighvibrationareastendtoacceleratedegradationovertime,resultingin

"chattering"contacts

and

intermittent

symptoms.

High

vibration

can

also

cause

tie

wraps,

or

stringtiestodamageinsulation. Inaddition,highvibrationwillexacerbateanyexisting

problemwithwireinsulationcracking.

MoistureHighmoistureareasgenerallyacceleratecorrosionofterminals,pins,sockets,and

conductors. ItshouldbenotedthatEWISinstalledinclean,dryareaswithmoderate

temperaturesappearstoholdupwell.

MaintenanceUnscheduledmaintenanceactivities,ifdoneimproperly,maycontributetolong

termproblemsandEWISdegradation. Repairsthatdonotmeetminimumairworthiness

standardsmayhavelimiteddurability. Repairsthatconformtomanufacturersrecommended

maintenancepracticesaregenerallyconsideredpermanentandshouldnotrequirereworkif

properlymaintained.

Metalshavingsanddebrishavebeendiscoveredonwirebundlesaftermaintenanceorrepairshavebeenconducted. Careshouldbetakentoprotect

wirebundlesandconnectorsduringmodificationwork,andtoensureall

shavingsanddebrisarecleanedupafterworkiscompleted.


9/67

Asageneralrule,EWISthatisundisturbedwillhavelessdegradationthanEWISthatisreworked. AsEWISbecomemorebrittlewithage,thiseffectbecomes

morepronounced.

[Endspeakernotes]

Slide24:CausesofEWISDegradation,cont.

Indirectdamage Chemicalcontamination Heat Installation

[Speakernotes]

IndirectdamageEventssuchaspneumaticductrupturescancausedamagethat,whilenot

initiallyevident,canlatercauseEWISproblems.Whensuchaneventhasoccurred,

surroundingEWIS

should

be

carefully

inspected

to

ensure

no

damage

is

evident.

ChemicalcontaminationChemicalssuchashydraulicfluid,batteryelectrolytes,fuel,

corrosioninhibitingcompounds,wastesystemchemicals,cleaningagents,deicingfluids,paint,

andsoftdrinkscancontributetodegradationofEWIS. EWISinthevicinityofthesechemicals

shouldbeinspectedfordamageordegradation.Recommendedoriginalequipment

manufacturercleaninginstructionsshouldbefollowed.

Hydraulicfluids,forexample,requirespecialconsideration. Hydraulicfluidisverydamagingtoconnectorgrommetandwirebundleclamps,leadingto

indirectdamage,suchasarcingandchafing. EWIScomponentsthatmayhave

beenexposedtohydraulicfluidshouldbegivenspecialattentionduringEWIS

inspections.

HeatEWIScomponentsexposedtohighheatcanacceleratedegradation,insulationdryness,andcracking. Directcontactwithahighheatsourcecanquicklydamageinsulation. Evenlow

levelsofheatcandegradeEWISoverlongperiodsoftime. Thistypeofdegradationis

sometimesseenonengines,ingalleys,andbehindlights.

InstallationEWISnotinstalledproperlycanfurtheracceleratetheEWISdegradationprocess.

Improperrouting,clamping,andterminatingduringinitialinstallationorduringamodifications

canleadtoEWISdamage.

[Endspeakernotes]

Slide25:

Current

FAA

Guidance

[Graphic]

Inthecenter,EWISPractices,surroundedwithPart25,Part26,AC25.17011,PolicyANM01

04,AC2510,AC2516,AC43.131bandAC25.27A

[Endgraphic]

[Speakernotes]


10/67

Therearedirectspecificpart25andpart26EWISpracticesrelatedto14CFR.

Therearesomespecificelectricalpowerwiringrequirements,suchas25.1353,buttheydo

notspecificallyaddressallaircraftEWIS.

14CFR25.1729requiresthatinstructionsforcontinuedairworthinessaredevelopedusing

analyticalprocedures,whichwouldincludemaintenancetasksandintervalsforEWIS.Alarge

bodyof

FAA

general

guidance

for

wiring

practices

is

in

Chapter

11

of

AC

43.13

1b.

[Endspeakernotes]

Slide26:Part25

Newpart25requirementsforcertificationofelectricalwiringinterconnectionsystems(EWIS)

o RevisedexistingEWISrelatedcertificationrequirementsandrelocatedsomeofthem

o CreatednewEWIScertificationrequirementsand

placed

them

in

anew

subpart

H

o NewEWISICArequirements

Slide27:Part26

Affectscontinuedairworthinessissuesand/orsafetyimprovementsfortransportairplanesaddressedviaoperationalrules

Supportstheabilityofoperatorstocomplywiththeoperationalrulerequirements EAPASPart26RequiresactionsofDesignApprovalHolders(DAHs),suchas:

o instructionsforcontinuedairworthiness,o

distribution

of

information

to

affected

operators

Slide28:Part26ModelApplicability

Existingairplaneswithamaximumtypecertificatedpassengercapacityof30ormore,or

Existingairplaneswithamaximumpayloadcapacityof7,500poundsormore(reference119.3)

ExistingairplanemodelswithatypecertificateissuedonorafterJanuary1,1958.

Slide29:AC25.1701-1

ThisAdvisoryCircular(AC)providesguidanceforcertificationofelectricalwiringinterconnectionsystems(EWIS)ontransportcategoryairplanes

o 14CFRpart25,subpartH,sections25.1701through25.1733o H25.4andH25.5ofAppendixHtopart25.


11/67

Slide30:AC25.27A

ProvidesguidancefordevelopingmaintenanceandinspectioninstructionsforEWIS Usesanenhancedzonalanalysisprocedure(EZAP). Forairplanemodelswhosemaintenanceprogramsalreadyincludeazonalinspection

program,thelogicdescribedhereprovidesguidanceonimprovingthoseprograms.

Slide31:AC25.27A,cont.

Forairplaneswithoutazonalinspectionprogram,useofthislogicwillproducezonalinspectionsforEWISthatcanbeaddedtotheexistingmaintenanceprogram.

ContainsinformationthatcanbeusedbyoperatorstoImproveEWISmaintenancepractices.

StressestheimportanceofinspectingEWISandpromotesaphilosophyofprotectandcleanasyougowhenperformingmaintenance,repair,oralterationsonanairplane.

Slide32:PolicyANM-01-04

DesigndatashouldNOTleavetheinstallationtothediscretionoftheinstaller. RoutingofEWISshouldfollowthecriteriaestablishedbytheFAAinthecertification

basis,asreflectedintheholdersoriginalorsubsequentlyapprovedtypedesign.

Installationdrawings/instructionsshouldcompletelydefinetherequiredroutingandinstallationwithsufficientdetailtoallowrepeatabilityoftheinstallation.

Slide33:Guidance:AC43.13-1b

AC43.131b: AcceptableMethods,Techniques,andPractices AircraftInspectionandRepair

AC43.13

1b:

o FlightStandardsACo Chapter11 AircraftElectricalSystems

NOTE: TheguidanceprovidedinAC43.131bisgeneralinnatureandisnottobereferencedor

usedasasubstituteforEWISinstallationdrawingsand/orEWISdiagrams.

[Speakernotes]

AC43.131bcoversafairlycomprehensivewiderangeofbasicEWISpracticestopics.

NOTE:The

guidance

provided

in

AC

43.13

1b

is

general

in

nature

and

is

not

to

be

referenced

or

usedasasubstituteforEWISinstallationdrawingsand/orEWISdiagrams.

[Endspeakernotes]

Slide34:Guidance:AC25-16

AC25 16: ElectricalFaultandFirePreventionandProtection(4/5/91)AC25 16:


12/67

o Providesacceptablemeanstoaddresselectricallycausedfaults,overheat,smoke,andfireintransportcategoryairplanes

[Speakernotes]

AC2516provideswiringpracticesguidanceasitrelatestoaircraftfireandsmokesafetywith

emphasison

wiring

flammability,

circuit

breaker

protection,

wiring

near

flammable

fluids,

and

associatedacceptabletestmethods.

ThisACiscurrentlybeingconsideredforupdating.

[Endspeakernotes]

Slide35:Guidance:AC25-10

AC25 10: GuidanceforInstallationofMiscellaneous,NonrequiredElectricalEquipment(3/6/87)

AC25 10:

o Providesacceptablemeanstocomplywithapplicable14CFRsassociatedwithinstallation

of

electrical

equipment

such

as

galleys

and

passenger

entertainment

systems

[Speakernotes]

AC2510mainlycoversnonrequiredequipmentinstallationssuchasgalleys,passenger

entertainmentsystems,etc. Fromawiringstandpoint,allsystemsshouldbetreatedequally,

regardlessofthefunctionscriticalitybecauseofpotentialfireandsmokehazards.

ThisACcontainsminimalwiringpracticesspecifics,includinggeneralloadanalysisrequirements

andcircuitbreakerprotectionrequirements,whicharemorethoroughlycoveredinAC43.13

1bandAC2516,sowearenotgoingtobecovering2510inanydetail.

[Endspeakernotes]

Slide36:ElectricalLoadDetermination

Loadanalysiso Ensurethattotalelectricalloadcanbesafelycontrolledormanagedwithinrated

limitsofaffectedcomponentsofaircraftselectricalsystem(25.1351)

o Neworadditionalelectricaldevicesshouldnotbeinstalledwithoutanelectricalloadanalysis

(AC43.131b)

[Speakernotes]

Electricalloaddeterminationistoensureeachaircraftelectricalbuscansafelysupporta

predeterminedamountofelectricalloadthatisbasedontheelectricalcapacityoftheaircraft

generatorsandtheaircraftsoverallelectricaldistributionsystem.

25.1351requirement: Itmustbedeterminedthroughanalysisthatallelectricaldevicescan

besafelycontrolledormanagedbytheaircraftselectricalsystem.


13/67

AC43.131b:Wheneveranelectricaldeviceisadded,aloadanalysisshouldbeperformedto

ensurethatthenewloadonthebuscanbepoweredadequatelysuchthatthereisadequate

electricalpowermargintoavoidoverloadingthebus.

Wherenecessaryasdeterminedbyaloadanalysis,wire,wirebundles,andcircuitprotective

deviceshavingthecorrectratingsshouldbeaddedorreplaced.

[Endspeaker

notes]

Slide37:CircuitBreakerDevices

Mustbesizedtoopenbeforecurrentratingofattachedwireisexceeded,orbefore

cumulativeratingofallconnectedloadsisexceeded,whicheverislower(25.1357)

[Speakernotes]

Section25.1357requiresthatautomaticprotectivedevicesbeusedtominimizedistresstothe

electricalsystemandminimizehazardtotheairplaneintheeventofwiringfaultsorserious

malfunction

of

the

system

or

connected

equipment.

[Endspeakernotes]

Slide38:CircuitBreakerProtection

Acircuitbreakermustalwaysopenbeforeanycomponentdownstreamcanoverheatandgeneratesmoke

orfire.(AC43.131b,para.1148)

Circuitbreakersaredesignedascircuitprotectionforthewire,notforprotectionofblackboxesorcomponents...(AC43.131b,

para.1151)

[Speakernotes]

AC43.131bcontainssomeconflictingstatements. Thebulletsinthisslidearesomewhat

contradictory. Thefirstbulletsaysthatthebreakermustprotectagainstanydownstream

componentfailure. ThesecondbulletsaysbreakersaredesignedsuchthattheyDONOT

protectcomponentsorLRUs.

Inreality,breakersaresizedtoprotecttheaircraftwiringasthemaindesignconstraint. Any

furtherprotectionofcomponentsorLRUsisdesirablebutnotmandatory.

Ideally,circuitbreakersshouldprotectagainstanywiringfaultthatleadstoarcing,sparking,

flames,orsmoke. Butaswewilllearn,thermalcircuitbreakersdonotalwaysdetectarcing

events.

[Endspeakernotes]

Slide39:CircuitBreakerProtection,cont. Useofacircuitbreakerasaswitchisnotrecommended

o Repeatedopeningandclosingofcontactscanleadtodamageandprematurefailureofcircuitbreakers


14/67


15/67

Theyshouldnotbeusedinapplicationswheretheywillbesubjectedtoexcessivevibration,

repeatedbending,orfrequentdisconnectionfromscrewtermination.

[Endspeakernotes]

Slide42:

Wire

Selection,

cont.

Conductorstrandingo Minimizesfatiguebreakage

Platingsforallcopperaircraftwiringo Platedbecausebarecopperdevelops

surfaceoxidefilmapoorconductor

Tin


16/67

Slide44:DeterminingWireSystemDesign

AC43.131b,Section5:tablesandfiguresprovideanacceptablemethodof determiningwire

systemdesign

[Speakernotes]

Theapplicant

should

ensure

that

the

maximum

ambient

temperature

that

the

wire

bundles

will

besubjectedto,plusthetemperatureriseduetothewirecurrentloads,doesnotexceedthe

maximumconductortemperaturerating.

Insmallerharnesses,theallowablepercentageoftotalcurrentmaybeincreasedastheharness

approachesthesinglewireconfiguration.

ThecontinuouscurrentratingscontainedinthetablesandfiguresinAC43.131bwerederived

onlyforwireapplication,andcannotbeapplieddirectlytoassociatedwireterminationdevices

(e.g.,connectorcontacts,relays,circuitbreakers,switches). Thecurrentratingsfordevicesare

limitedbythedesigncharacteristicsofthedevice. Careshouldbetakentoensurethatthe

continuouscurrentvaluechosenforaparticularsystemcircuitshallnotcreatehotspotswithin

anycircuit

element

which

could

lead

to

premature

failure.

[Endspeakernotes]

Slide45:WireSubstitutionforRepairsandMaintenance

Whenreplacementwireisrequired,reviewaircraftmaintenancemanualtodetermineiforiginalaircraftmanufacturer(OAM)hasapprovedanysubstitution

o Ifnotapproved,thencontactOAMforanacceptablereplacement

[Speaker

notes]

MostaircraftEWISdesignsaretospecificationsthatrequiremanufacturerstopassrigorous

testingofwiresbeforetheyareapprovedoraddedtoaQualifiedProductsList. Aircraft

manufacturerswhomaintaintheirownwirespecificationsexerciseclosecontroloftheir

approvedsources. Therefore,itisimportanttoreviewtheaircraftmaintenancemanualor

contacttheoriginalaircraftmanufacturer(OAM)whenwiresubstitutionsarenecessary.

TheOAMmayhavespecialconcernsregardingshielding,insulation,etc.forcertainwiringon

theaircraftthatperformcriticalfunctionsorwiringthatischosenbasedonasetofunique

circumstances.

[Endspeakernotes]

Slide46:EWISRouting

Eliminatepotentialforchafingagainststructureorothercomponents Positiontoeliminate/minimizeuseashandholdorsupport Minimizeexposuretodamagebymaintenancecrewsorshiftingcargo Avoidbatteryelectrolytesorothercorrosivefluids


17/67


18/67

[Endspeakernotes]

Slide50:EWISasaHandhold

[Graphic]

Showspersons

hand

holding

onto

the

EWIS

with

international

not

symbol

superimposed

acrossit.

[EndGraphic]

[Speakernotes]

RouteEWISsothatitisnotusedasahandholdorasasupportformaintenancepersonnel.

Inaddition,routeEWISsothatitavoids:

Damagebypersonnelmovingwithintheaircraft. Damagebystowageorshiftingcargo. Damagebybatteryoracidicfumesorfluids.

Abrasion

in

wheel

wells

where

exposed

to

rocks,

ice,

mud,

etc.

Damagefromexternalevents(zonalanalysis/particularrisksanalysisdemands). Harshenvironmentssuchasseverewindandmoistureprone(SWAMP)areas,

hightemperatures,orareassusceptibletosignificantfluidorfume

concentration.

EWISshouldberoutedtopermitfreemovementofshockandvibrationmountedequipment,

designedtopreventstrainonwires,junctions,andsupports,and,theEWISinstallationshould

permitshiftingofEWISandequipmentnecessarytoperformmaintenancewithintheaircraft.

Inaddition,wirelengthsshouldbechosentoallowforatleasttworeterminations.

[Endspeakernotes]

Slide51:

EWIS

Routing,

cont.

ProtectEWISinwheelwellsandotherexposedareas RouteEWISabovefluidlines,ifpracticable Usedriploopstocontrolfluidsorcondensedmoisture Keepslacktoallowmaintenanceandpreventmechanicalstrain

[Speakernotes]

EnsurethatEWIScomponentsareadequatelyprotectedinwheelwellsandotherareaswhere

theymaybeexposedtodamagefromimpactofrocks,ice,mud,etc. (IfreroutingofEWISis

notpracticable,

protective

jacketing

may

be

installed.)

This

type

of

installation

must

be

held

to

aminimum.

Wherepractical,routeEWISsandcablesabovefluidlines.Wiresandcablesroutedwithin6

inchesofanyflammableliquid,fuel,oroxygenlineshouldbecloselyclampedandrigidly

supported. Aminimumof2inchesmustbemaintainedbetweenwiringandsuchlinesor

relatedequipment,exceptwhenthewiringispositivelyclampedtomaintainatleast1/2inch

separationorwhenitmustbeconnecteddirectlytothefluidcarryingequipment.


19/67

Ensurethatatrapordriploopisprovidedtopreventfluidsorcondensedmoisturefrom

runningintoEWISandothercomponents.EWIS installedinbilgesandotherlocationswhere

fluidsmaybetrappedareroutedasfarfromthelowestpointaspossibleorotherwiseprovided

withamoistureproofcovering.

[Endspeakernotes]

Slide52:EWISAboveFluidLines

Brokenwireshallnotmakecontactwithfluidline

[Graphic]

Showsbrokenwireexposedendtouchingthefluidline

[EndGraphic]

[Speakernotes]

EWIS

above

fluid

lines.

The

clamps

should

be

a

compression

type

and

should

be

spaced

so

that,assumingawirebreak,thebrokenwirewillnotcontacthydrauliclines,oxygenlines,

pneumaticlines,orotherequipmentwhosesubsequentfailurecausedbyarcingcouldcause

furtherdamage.

[Endspeakernotes]

Slide53:Graphic

Wiresimproperlytied,ridingonhydrauliclines,contaminatedwithcausticfluid

[Graphic]

Showswires

touching

hydraulic

lines

[EndGraphic]

[Speakernotes]

Thisexampleshowsanumberofproblems:

Wiresinthebundlesarenottiedproperly. Thewirebundleisridinghardonthehydrauliclines. Thewirebundleappearstobecontaminatedwithhydraulicfluidresidue.

[Endspeakernotes]

Slide54:YTypeWireBundleBreakouts

[Graphic]

Bundleshowingfigure8loopasbundlesplitsintotwobundles.GraphicsaysFigure8loopmay

belocatedbeforeoraftertailofYandHeadofstrapshallnotbelocatedinthisareaortouching

anythingtocausechafing

[Endgraphic]


20/67

[Speakernotes]

Wirebundlebreakouts. Therearethreebasicwirebundlebreakouttypesusedinrouting

aircraftEWIS. TheyarecalledtheY,T,andComplextypes.

TheYtypeofbreakoutisusedwhenaportionofEWISfromonedirectionofthewirebundle

departsthe

bundle

to

be

routed

in

another

direction.

Careshouldbetakenwhenplastictiewrapsareusedtoprovidewirecontainmentatthebreakoutsothatthetiewrapheaddoesnotcausechafing

damagetothewirebundleatthebreakoutjunction.

[Endspeakernotes]

Slide55:TTypeWireBundleBreakouts

[Graphic]

BundleshowsaTtypebundlewithacrisscrosstieatjunctionaroundtheT.Gradphicsays

Headof

strap

shall

not

be

located

in

this

area

or

touching

anything

to

cause

chafing

referring

to

the

topofthebundleandthesideoftheTgoingup.

[Endgraphic]

[Speakernotes]

TheTtypeofbreakout(alsocalled90breakout)isusedwhenportionsofEWISfromboth

directionsinthewirebundledepartthebundletoberoutedinanotherdirection.

[Endspeakernotes]

Slide56:ComplexTypeWireBundleBreakouts

[Graphic]

Showsaterminalblockwiththewireconnections

[Endgraphic]

[Speakernotes]

AComplextypeofbreakoutisgenerallyusedtoroutecertainwiresoutofawirebundletoa

terminalstrip,moduleblock,orothertermination.

Foralltypesofbreakouts,thereshouldbesufficientslackinthewiresthatarebeingbrokenout

ofthebundletoavoidstrainonthewirebetweenthewirebundleandthetermination.

[Endspeakernotes]

Slide57:Stand-offs

UsestandoffstomaintainclearancebetweenEWISandstructureo Employingtapeortubingisgenerallynotacceptableasanalternativenot

ExceptionException:WhereimpossibletoinstalloffangleclampstomaintainEWISseparationinholes,bulkheads,floors,etc.

:


21/67

[Speakernotes]

TheEWISdesignshouldprecludewirebundlesfromcontactingstructure. Standoffsshouldbe

usedtomaintainclearancebetweenEWISandstructure.

Employingtapeorprotectivetubingasanalternativetostandoffsshouldbeavoidedasa

primarymeans

of

preventing

EWIS

contact

with

structure.

Exception: Usingtapeortubingisallowedincaseswhereitisimpossibletoinstalloffangle

clampstomaintainEWISseparationinholes,bulkheads,floors,etc.

[Endspeakernotes]

Slide58:UsingStand-offs

[Graphic]

GraphicshowstheImpropermethodwithwiresimmediatelytouchingthebaseafterusinga

standoff.Propermethodshowswiresinstandoffnottouchingbase.

[End

graphic]

[Speakernotes]

Whenusingstandoffsforadditionalclearance,clampsshouldnotbeinstalledinamannerthat

defeatsthestandoffspurposeofprovidingadditionalclearancebetweenEWISandstructure.

[Endspeakernotes]

Slide59:Bundleridingonstructure

[Graphic]

showingbundletouchingaircraftstructure

[Endgraphic]

[Speakernotes]

OneofthemorecommonaircraftEWISproblemsischafingduetowirebundlescominginto

contactwithaircraftstructureorotheraircraftequipment.

[Endspeakernotes]

Slide60:Graphic

[Graphic]

Wirebundle

too

close

to

control

cable

[Endgraphic]

[Speakernotes]

Thispictureshowsawirebundlethatisinclosecontactwithacontrolcable. Adequate

distancebetweenEWISandcontrolcablesshouldbemaintainedtoaccountformovementdue

toslackandmaintenance.


22/67


23/67


24/67


25/67

[Speakernotes]

AcommonprobleminaircraftEWISisclamppinching. Thisoccurswhentheclampis

improperlyinstalledortheclampistoosmall. Clampsonwirebundlesshouldbeselectedso

thattheyhaveasnugfitwithoutpinchingwires.

[Endspeaker

notes]

Slide69:TypicalNylonClosed-FaceClampInstallation

[Graphic]

Showsbundleofwiresinclamponastandoff.Itsaysdonotpinchherereferringtothepoint

wheretheclampcomestogether.

[Endgraphic]

[Speakernotes]

It

is

important

when

adding

wiring

to

an

existing

wire

bundle

to

evaluate

the

existing

clamp

sizinginordertoavoidpossibleclamppinching. Insomecasesitmaybenecessarytoincrease

thesizeoftheclampstoaccommodatethenewwiring.

[Endspeakernotes]

Slide70:EngageClampTabinSlot

[Graphic]

Showsimproperwhereclamptabshaveaseparationandproperwhereclamptabsandtight

andflushtoeachother

[Endgraphic]

[Speakernotes]

Whenusingclamptabs,makesurethatthetabsareproperlyengaged. Otherwise,thetab

couldbecomelooseandcausesubsequentwiredamage.

DuringEWISinstallationinspections,ensurethattheclampissnappedbeforeinstallingandtighteningthebolt.

[Endspeakernotes]

Slide71:ClampPinching

[Graphic]

Shows improperwherethewiresarepinchedatwheretheclampcomestogetherandproper

wherethewiresdonotpinchintheclamp.

[Endgraphic]

[Speakernotes]Thisslidefurtherillustrateshowwirescanbepinchedanddamageddueto

improperclampinstallation.[Endspeakernotes]


26/67

Slide72:ClampPinching,cont.

[Graphic]

Shows improperwheretherearetwowiresintheclampcausingpinchingandproperwhere

theright

sized

clamp

is

used

and

not

causing

any

pinching.

[Endgraphic]

[Speakernotes]

Toomuchwiringinaclamporimproperlyinstalledclampscanleadtopinchingofthewires

[Endspeakernotes]

Slide73:Graphic

[Graphic]

Openfaced

nylon

clamp

with

cable

build

up

(missing

hardware)

[Endgraphic]

[Speakernotes]

ThispicturewastakenduringageneralvisualEWISinspectionofawidebodytransportaircraft.

Notethemissingclamphardware. Alsonotethattheblackcableusedatapebuildupatthe

clamp. SomemanufacturersEWISspecificationsallowforwirecablebuildupundercertain

circumstances.

[Endspeakernotes]

Slide74:

Wire

Bend

Radii

Minimumbendradius 10timestheoutsidediameterofthelargestwireorcableinthegroupunsupported

o Exceptions Terminations/reversingdirectioninbundle(supportedatbothendsof

loop) 3timesthediameter

RFcables 6timesthediameter Thermocouplewire 20timesthediameter

[Speakernotes]

Theminimum

radius

of

bends

in

wire

groups

or

bundles

must

not

be

less

than

10

times

the

outsidediameterofthelargestwireorcable,exceptthatattheterminalstripswherewires

breakoutatterminationsorreversedirectioninabundle.

Wherethewireissuitablysupported,theradiusmaybe3timesthediameterofthewireor

cable.

Whereitisnotpracticaltoinstallwiringorcableswithintheradiusrequirements,thebend

shouldbeenclosedininsulatingtubing.


27/67

Theradiusforthermocouplewireis20timesthediameter. (Thisisverydelicatewire.)

EnsurethatRFcables,(forexample,coaxialandtriaxial,arebentataradiusofnolessthan6

timestheoutsidediameterofthecable.

[Endspeakernotes]

Slide75:MinimumBendRadii

[Graphic]

Wirebundleillustrating

Nosupportatendofbendo Min.bendradius10xparameterofwireorcable

Supportatendofbendo Min.bendradius3xdiameterofwire

Ttypebendo Min.bendradius3xdiameterofwire

[Endgraphic]

[Speakernotes]

Thisillustrationshowstheproperbendradiiforthreedifferentscenarios.

[Endspeakernotes]

Slide76: Graphic

[Graphic]

Bendradiiokay Greaterthan3timesdiameter(securedatbothendsofloop)

[Endgraphic]

[Speakernotes]

Thisphotographshowsawireloopsecuredatbothendsoftheloop. Inthiscase,thebend

radiusshouldbenolessthan3timesthediameterofthelargestwireinthewirebundle.

[Endspeakernotes]

Slide77:Graphic

[Graphic]

Bendradiiproblem Lessthan3timesthediameter

[Endgraphic]

[Speakernotes]

Alsosupportedateachendoftheloop,thiswirebundledoesnotmeetbendradiusstandards

duetothelargewiresinthebundle.

[Endspeakernotes]


28/67


29/67

Slide82:SpareWireTerminationUsingEndcap

[Graphic]

Showing

Wireandcapinpositionforcaptoslideoverwire Installendcapoverwireendandshrinkinplace Bundleusingadhesiveandfiberglasstyingtape

[Endgraphic]

[Speakernotes]

Installingprefabricatedendcapsareaneffectivemethodofprotectingunusedwireswith

exposedconductors.

Thisslidedepictsatypicalexampleoftheuseofaprefabricatedendcap.[Endspeakernotes]

Slide83:UnusedWires

[Graphic]

Unusedwiring Improperterminationwithexposed conductor(shouldbeproperlyinsulated

andsecuredtobundle)

[Endgraphic]

[Speakernotes]

FoundduringageneralEWISvisualinspection,thisexampleshowstwounusedwiresthathave

beencutandtheconductorsareunprotected. Inaddition,theunusedwiresarenotsecuredto

thewirebundle.

[Endspeakernotes]

Slide84:CoilandStowMethods

Coilandstowshortwirebundlesinlowvibrationareas

[Graphic]

wirebundlecoiledinaloopwithaclampandwire tiestoholdittogether[Endgraphic]

[Speakernotes]

Coilandstowmethodsareoftenusedtosecureexcesslengthofawirebundleortosecure

wirebundlesthatarenotconnectedtoanyequipment,suchaswiringprovisioningforafuture

installation.

[Endspeakernotes]

Slide85:CoilandStowMethods,cont.Coilandstowlongwirebundlesinlowvibrationareas


30/67

[Graphic]

excesswireloopedbackandforthtoremovetheexcess.Useswiretiesandclamp

tobundletogether[Endgraphic]

[Speakernotes]

Thekeyobjectivetocoilingandstowingwiringistosafelysecurethewirebundletoprevent

excessivemovementorcontactwithotherequipmentthatcoulddamagetheEWIS.

[Endspeakernotes]

Slide86:CoilandStowMethods,cont.

Coilandstowinmediumandhighvibrationareas

[Graphic]

wirebundle,

with

aradius

between

two

bundles,

tied

to

awire

bundle

at

the

top

andbottomusingTeflontape[Endgraphic]

[Speakernotes]

Coilandstowinmediumandhighvibrationareasrequiresadditionaltiestraps,sleeving,and

support.

[Endspeakernotes]

Slide

87:

Stowing

Unused

Wires

[Graphic]

Impropermethodwithbundletiedtoasinglewireaboveit.Propermethodwith

bundletiedandnottiedtoanythingelse[Endgraphic]

[Speakernotes]

Thesephotosshowimproperandproperstowingofunusedwires.

[Endspeakernotes]

Slide88:EWISReplacement

EWIScomponentsshouldbereplacedwhen:o Chafedorfrayedo Insulationsuspectedofbeingpenetratedo Outerinsulationiscrackingo Damagedbyorknowntohavebeenexposedtoelectrolyte,oil,hydraulic

fluid,etc.


31/67

o Evidenceofoverheatingcanbeseen[Speakernotes]

EWISneedstobereplacedunderanumberofcircumstances:

Wiringthathasbeensubjectedtochafingorfraying,thathasbeendamaged,orthat

primary

insulation

is

suspected

of

being

penetrated.

Wiringonwhichtheouterinsulationisbrittlewhenslightflexingcausesittocrack.

Wiringthathasweathercrackedouterinsulation. NOTE:somewireinsulationtypesappearstobewrinkledwhenthewireisbentandmaynotbedamaged.

Wiringthatisknowntohavebeenexposedtoelectrolyteoronwhichtheinsulationappearstobe,orissuspectedofbeing,inaninitialstageof

deteriorationduetotheeffectsofelectrolyte.

Thereisvisibleevidenceofinsulationdamageduetooverheating.[Endspeakernotes]

Slide89:HeatDiscoloration

[Speakernotes]

Thisphotographshowsanexampleofheatdiscolorationonprotectivesleevingwhichispartof

thewirebundle. Thelargeclampwasmovedtoseethedifferenceincolor. Inthiscase,the

wiringthatisnotcoveredinsleevingshowsnosignsofheatdistress. Anadjacentlightbulb

wasradiatingenoughheattocausediscolorationovertimetotheprotectivesleeving.

Althoughthisconditionisnotideal,itisacceptable.

[Endspeaker

notes]

Slide90:WireReplacement

Wireshouldbereplacedwhen:o Wirebearsevidenceofbeingcrushedorkinkedo Shieldonshieldedwireiffrayedand/orcorrodedo Wireshowsevidenceofbreaks,cracks,dirt,ormoistureinplasticsleevingo Sectionsofwirehavesplicesoccurringatlessthan10ftintervals

[Speakernotes]

Continuing,theseareadditionalcircumstancesthatwarrantreplacingEWIS:

EWISthatbearsevidenceofhavingbeencrushedorseverelykinked. ShieldedEWISonwhichthemetallicshieldisfrayedand/orcorroded. Cleaning

agents(whichcancausewiredamage)orpreservativesshouldnotbeusedto

minimizetheeffectsofcorrosionordeteriorationofwireshields.


32/67

EWISshowingevidenceofbreaks,cracks,dirt,ormoistureintheplasticsleevesplacedoverwiresplicesorterminallugs.

Sectionsofwireinwhichsplicesoccuratlessthan10footintervals,unlessspecificallyauthorized,duetoparallelconnections,locations,orinaccessibility.

[Endspeakernotes]

Slide91:WireReplacement,cont.

Shieldingrequirementso Replacementwiresmusthavethesameshieldingcharacteristicsastheoriginal

wire,suchasshieldopticalcoverageandresistanceperunitlength

o Replacementwiresshouldnotbeinstalledoutsidethebundleshield[Speakernotes]

Replacementwiresshouldhavethesameshieldingcharacteristicsastheoriginalwires,suchas

shieldoptical

coverage

and

resistance

per

unit

length.

Ifanywiresaregoingtobereplacedinsideashieldedwirebundle,thereplacementwires

shouldnotbeinstalledoutsidethebundleshield.

Formoreinformationonshielding,theLightning/HIRFVideoandSelfstudyGuideisavailable.

(Toobtain,seeyourDirectoratetrainingmanager.)

[Endspeakernotes]

Slide92:AddingorReplacingWiresonaBundle

[Graphic]

Improperprocedurewithloosewiresnottieddownbetweenclamps.Proper

procedure

with

all

wires

tied

to

the

bundle

between

clamps.

[Endgraphic]

[Speakernotes]

Whenaddingorreplacingwiresonorinawirebundle,thereplacementoraddedwireshould

beroutedinthesamemannerastheotherwiresinthewirebundle.

Wirebundleclampsand/ortiesmayneedtobeloosenedorremovedinordertoproperlyaddorreplacewires.

Whenthenewwireisinstalled,thetiesandclampsshouldbeopenedoneatatimetoavoidexcessivedisassemblyofthewirebundles.

[Endspeakernotes]

Slide93:AddingWiresonaBundle

[Graphic]

FirstimageshowsImproperlyroutedoutsideofthetiewrapthatsecuresthe

clampandthesecondimageshowwiringroutedcorrectly[Endgraphic]


33/67

[Speakernotes]

Properandimproperlyroutedwiresinabundle

[Endspeakernotes]

Slide94:

Wire

Splicing

Keeptoaminimum Avoidinhighvibrationareas Locatetopermitinspection Staggerinbundlestominimizeincreaseinbundlesize Useselfinsulatedspliceconnector,ifpossible

[Speakernotes]

SplicingispermittedonEWISaslongasitdoesnotaffectthereliabilityandtheelectro

mechanicalcharacteristicsoftheEWIS. Splicingofpowerwires,coaxialcables,multiplexbus,

andlarge

gauge

wire

should

be

avoided.

If

it

cant

be

avoided,

then

the

power

wire

splicing

musthaveapproveddata.

Splicingofelectricalwireshouldbekepttoaminimumandavoidedentirelyinlocationssubjecttoextremevibrations. Splicingofindividualwiresinagroupor

bundleshouldhaveengineeringapprovalandthesplice(s)shouldbelocatedto

allowperiodicinspection.

Manytypesofaircraftspliceconnectorsareavailableforusewhensplicingindividualwires.

Useofaselfinsulatedspliceconnectorispreferred;however,anoninsulatedspliceconnectormaybeusedprovidedthespliceiscoveredwithplasticsleeving

thatissecuredatbothends.

EnvironmentallysealedsplicesthatconformtoMILT7928provideareliablemeansofsplicinginSWAMPareas. However,anoninsulatedspliceconnector

maybeused,providedthespliceiscoveredwithdualwallshrinksleevingofa

suitablematerial.

[Endspeakernotes]

Slide95:StaggeredSplices

[Graphic]

Imageshowsasmallsectionwith4splicesandthewiretieplacedsothattwo

splicesareononesideandtwoontheother[Endgraphic]

[Speakernotes]

Splicesinbundlesshouldbestaggeredsoastominimizeanyincreaseinthesizeofthebundle

thatwould:

Preventbundlefromfittingintodesignatedspace. Causecongestionadverselyaffectingmaintenance.


34/67

Causestressonthewires.[Endspeakernotes]

Slide96:Graphic

[Graphic]

Overheatedwireatthesplice

[Endgraphic]

[Speakernotes]

Splicesthatarenotcrimpedproperly(underorover)cancauseincreasedresistanceleadingto

overheatconditions.

[Endspeakernotes]

Slide

97:

Graphic

[Graphic]

Gangedwiresplices

[Endgraphic]

[Speakernotes]

Ifsplicesarenotstaggered,properstrainreliefshouldbeprovidedinordertoavoidstresson

thewires. Inthisparticularinstallation,strainreliefwasappliedtoavoidstressonthewires.

[Endspeakernotes]

Slide98:

Graphic

[Graphic]

Gangedwiresplices,9spliceswith7spliceswithslackand2splicesthataretauntbetweenthe

clamps.

[Endgraphic]

[Speakernotes]

Thetoptwowiresinthisphotoareexperiencingstressduetoapreloadcondition. Alsonote

thatthewirebundleisnotproperlyclamped

[Endspeakernotes]

Slide99:Terminals

Tensilestrengthofthewiretoterminaljointshouldbeatleasttheequivalenttensilestrengthofthewire

Resistanceofthewiretoterminaljointshouldbenegligiblerelativetothenormalresistanceofthewire


35/67

[Speakernotes]

Tensilestrengthterminalsareattachedtotheendsofelectricalwirestofacilitateconnectionof

thewirestoterminalstripsoritemsofequipment. Thetensilestrengthofthewiretoterminal

jointshould

be

at

least

equivalent

to

the

tensile

strength

of

the

wire

itself.

Resistanceofwiretoterminaljointshouldbenegligible,relativetothenormalresistanceof

thewire.

Selectionofwireterminals. Thefollowingshouldbeconsideredintheselectionofwireterminals.

Currentrating.

Wiresize(gauge)andinsulationdiameter.

Conductormaterialcompatibility.

Studsize.

Insulationmaterialcompatibility.

Applicationenvironment.

Solder/solderless.

[Endspeakernotes]

Slide100:BendingofStraightCopperTerminals

[Graphic]

Firstimageshowscopperterminalendbent90degreesmaxtotheleftorright.Secondimage

showsterminalendbentupordown30degreesmax.Thirdimageshowscopperterminalbent

upordown45degreesmax.Fourthimageshowsabrazedjointwithamax30degreeandthe

tongueshouldbeevenwiththeendoftheterminal.

[Endgraphic]

[Speakernotes]

Ifbendingofaterminalisnecessary,careshouldbetakentoavoidoverbendingtheterminal

whichcancausedamagetotheterminal. Also,aterminalcanonlybebentoncesinceany

additionalbendingcancausedamage.

Preinsulatedcrimptyperingtongueterminalsarepreferred. Thestrength,size,and

supportingmeansofstudsandbindingposts,aswellasthewiresize,shouldbeconsidered

whendeterminingthenumberofterminalstobeattachedtoanyonepost.

Inhightemperatureapplications,theterminaltemperatureratingmustbegreaterthanthe

ambienttemperature

plus

current

related

temperature

rise.

Use

of

nickel

plated

terminals

and

ofuninsulatedterminalswithhightemperatureinsulatingsleevesshouldbeconsidered.

Terminalblocksshouldbeprovidedwithadequateelectricalclearanceorinsulationstrips

betweenmountinghardwareandconductiveparts.

Terminalsaresensitivetobendingatthejunctionbetweentheterminalringandtheterminal

crimpbarrel. Bendingtheterminalmorethanonceorexceedingpredeterminedterminal

bendlimitswillusuallyresultinmechanicalweakeningordamagetotheterminal.


36/67

ThisslideisanexampleoflimitsestablishedbytheOAMwithregardtobendingtheterminal

priortoinstallation.

[Endspeakernotes]

Slide101:

Terminal

Strips

Barrierstopreventadjacentstudsfromcontactingeachother Currentshouldbecarriedbyterminalcontactsurfaceandnotbystud Studsanchoredagainstrotation Replacedefectivestudswithstudsofsamesizeandmaterial,mountsecurely,tighten

terminalsecuringnut

[Speakernotes]

Wiresareusuallyjoinedatterminalstrips. Aterminalstripfittedwithbarriersshouldbeused

toprevent

the

terminals

on

adjacent

studs

from

contacting

each

other.

Studsshouldbeanchoredagainstrotation.Whenmorethanfourterminalsaretobeconnectedtogether,asmallmetalbusshouldbemountedacrosstwoor

moreadjacentstuds. Inallcases,thecurrentshouldbecarriedbytheterminal

contactsurfacesandnotbythestuditself.

Defectivestudsshouldbereplacedwithstudsofthesamesizeandmaterialsinceterminalstripstudsofthesmallersizesmayshearduetoovertightening

thenut. Thereplacementstudshouldbesecurelymountedintheterminalstrip

andtheterminalsecuringnutshouldbetight.

[Endspeakernotes]

Slide102:TerminalStrips,cont.

Mountstripssoloosemetallicobjectscannotfallacrossterminal

Providesparestudforbreaksandfutureexpansion

Inspectterminalperiodicallyforlooseconnections,metallicobjects,dirt,andgrease

accumulation

Cancausearcing,resultinginfireorsystemsfailure

[Speakernotes]

[Endspeaker

notes]

Slide103:Terminalsoncircuitbreakers

[Graphic]

terminalwiresconnectedtocircuitbreakerswithseparatescrews

[Endgraphic]


37/67

[Speakernotes]

Connectorsandterminalsinaircraftrequirespecialattentiontoensureasafeandsatisfactory

installation. Everypossibilityofterminalsnotbeingtorquedproperly,duetomisinstallation,

poormaintenance,andservicelife,shouldbeaddressedinthedesign.

Electricalequipmentmalfunctionhasfrequentlybeentracedtopoorterminalconnectionsatterminalboards.

Loosecontactsurfacescanproducelocalizedheatingthatmayignitenearbycombustiblematerialsoroverheatadjacentwireinsulation.

Notethegreentorquestripespaintedontheterminalfastenersinthispicture. Thisisan

excellentmethodtoquicklydetermineifaterminalfastenerisstilltorquedtoitsoriginalvalue.

[Endspeakernotes]

Slide104:Graphic

[Graphic]

Powerfeederterminals

[Endgraphic]

[Speakernotes]

Again,youcanseetheredcoloredtorquestripesappliedtothesehighcurrentpowerfeeder

terminations. Highcurrentterminalsaremoresensitivetoincreasedresistanceduetoa

improperlytorquedterminal.

Asasidenote,thepowerfeedercablesshouldnotbetouchingeachotherwithoutbeingsuitablytiedwithspacersorothersecuringdevice.

[Endspeaker

notes]

Slide105:TerminalLugs

Connectwiringtoterminalblockstuds Nomorethan4lugs,or3lugsand

abusbar,perstud

Lugholesizeshouldmatchstuddiametero Greatestdiameteronbottom,

smallestontop

o Tighteningterminalconnectionsshouldnotdeformlugs

[Speakernotes]


38/67

Wireterminallugsshouldbeusedtoconnectwiringtoterminalblockstudsorequipment

terminalstuds. Nomorethanfourterminallugsorthreeterminallugsandabusshouldbe

connectedtoanyonestud.

Totalnumberofterminallugsperstudincludesacommonbusbarjoiningadjacentstuds. Fourterminallugsplusacommonbusbarthusarenot

permittedon

one

stud.

Terminallugsshouldbeselectedwithastudholediameterthatmatchesthediameterofthe

stud. However,whentheterminallugsattachedtoastudvaryindiameter,thegreatest

diametershouldbeplacedonthebottomandthesmallestdiameterontop.

Tighteningterminalconnectionsshouldnotdeformtheterminallugsorthestuds. Terminal

lugsshouldbesopositionedthatbendingoftheterminallugisnotrequiredtoremovethe

fasteningscrewornut,andmovementoftheterminallugswilltendtotightentheconnection.

[Endspeakernotes]

Slide106:TerminalLugs,cont.

Aluminumlugso Crimpedtoaluminumwireonly

Specialattentionneededtoguardagainstexcessivevoltagedropatterminaljunction

Inadequateterminalcontactarea Stackingerrors Impropertorquing

o Usecalibratedcrimptools[Speakernotes]

Aluminumterminallugsshouldbecrimpedtoaluminumwireonly.Thetongueofthealuminumterminallugsorthetotalnumberoftonguesofaluminumterminal

lugswhenstacked,shouldbesandwichedbetweentwoflatwashers(cadmiumplated)when

terminatedonterminalstuds. Spacersorwashersshouldnotbeusedbetweenthetonguesof

likematerialterminallugs.

Specialattentionshouldbegiventoaluminumwireandcableinstallationstoguardagainst

conditionsthatwouldresultinexcessivevoltagedropandhighresistanceatjunctionsthatmay

ultimatelyleadtofailureofthejunction.

Examplesofsuchconditionsareimproperinstallationofterminalsandwashers,impropertorsion(torquingofnuts),andinadequateterminalcontactareas.

Notethat

aluminum

wire

is

normally

used

in

sizes

of

10

gauge

and

larger

to

carry

electrical

powerinlargetransportcategoryaircraftinordertosaveweight. Althoughnotasgooda

conductorascopper,aluminumislighterwhencomparedtocopperandtheweightsavingscan

besignificantforalargeaircraftthatmayhaveseveralhundredfeetofpowerfeedercable.

Becausealuminumisusedprimarilyforhighcurrentpowerapplications,theterminaljunctions

aremoresensitivetoconditionsleadingtoincreasedjunctionresistancewhichcancausearcing

andlocalizedheatdistress.


39/67

[Endspeakernotes]

Slide107:TerminalStacking(likematerials)[Graphic]

ExplodediagramofTerminalstacking.Frombottomtotop:terminalstud,copperterminallugs,

flatwasher,

lock

washer

and

nut.

[Endgraphic]

[Speakernotes]

Terminalstackingmaterialsandmethods

Multiplewiresoftenterminateontoasingleterminalstud. Careshouldbetakentoinstalltheterminalproperly. Thematerialsthattheterminalsareconstructed

ofwillimpactthetypeofstackingmethodsused. Dissimilarmetals,whenin

contact,canproduceelectrolysisthatcancausecorrosion,thusdegradingthe

terminaljunctionresistanceandcausingarcingorhotspots.

For

stacking

terminals

that

are

made

of

like

materials,

the

terminals

can

be

stackeddirectlyontopofeachother.

[Endspeakernotes]

Slide108:TerminalStacking(unlikematerials)[Graphic]

ExplodediagramofTerminalstacking.Frombottomtotop:terminalstud,flatwasher,

aluminumterminal,flatwasher,copperterminal,flatwasher,aluminumterminal,flatwasher,

lockwasherandnut

[Endgraphic]

[Speakernotes]

Whenstackingunlikematerialstogether(forexample,aluminumandcopper),acadmium

platedflatwasherisusuallyneededtoisolatethedissimilarmetals.

[Endspeakernotes]

Slide109:TerminalStackingMethods

[Graphic]

Explodediagramof"onesidedentrywithtwoterminals.".Frombottomtotop:terminalstud,

crimpbarrel

(belly

down),

crimp

barrel

(belly

up),

flat

washer,

lock

washer

and

nut

[Endgraphic]

[Speakernotes]

Whentwoterminalsareinstalledononesideoftheterminalstrip,careshouldbetakento

ensurethattheterminalcrimpbarrelsdonotinterferewithoneanother. Onemethodtoavoid

thisproblemistoinstalltheterminalswiththebarrelsbacktoback.


40/67

[Endspeakernotes]

Slide110:TerminalStackingMethods,cont.

[Graphic]

Explodediagram

of

"one

sided

entry

with

3terminals."

From

bottom

to

top:

terminal

stud,

crimpbarrel(bellydown)in"V"split,crimpbarrel(bellydown)in"V"split,crimpbarrel(belly

up))incenterof"V"split,flatwasher,lockwasherandnut

[Endgraphic]

[Speakernotes]

Thisillustrationdepictsaterminalinstallationwiththreeterminalsenteringononeside.

[Endspeakernotes]

Slide

111:

Terminal

Stacking

Methods,

cont.

[Graphic]

Explodediagramof"onesidedentrywith4terminals"..Frombottomtotop:terminalstud,

crimpbarrel(bellydown)in"V"split,crimpbarrel(bellydown)in"V"split,crimpbarrel(belly

up))incenterof"V"split,crimpbarrel(bellyup))incenterof"V"split,flatwasher,lock

washerandnut

[Endgraphic]

[Speakernotes]

Thisillustrationdepictsaterminalinstallationwithfourterminalsenteringononeside.

Thestackingmethodusedtoconnectterminalstoterminalstripsshouldcausenointerference

betweenterminals

that

could

compromise

the

integrity

of

the

terminal

junction.

[Endspeakernotes]

Slide112:TerminalTighteningHardware

[Graphic]

Impropertightening:terminalstud,flatwasher,terminals,flatwasher,lockwashernot

compressed,space,andnut.Propertightening:terminalstud,flatwasher,terminals,flat

washer,lockwashercompressed,andnut.

[Endgraphic]

[Speakernotes]

Servicehistoryhasshownthathardwarestackupatterminalsispronetohumanerror.

Omissionoflockwashers,incorrectwashers,impropersizingofwashers,etc.hasbeena

definiteproblem.


41/67


42/67

Slide116:Grounding

Typesofgroundingo ACreturnso DCreturnso Others

Avoidmixingreturncurrentsfromvarioussourceso Noisewillbecoupledfromonesourcetoanotherandcanbeamajorproblem

fordigitalsystems

[Speakernotes]

Groundingtypes: ACreturns,DCreturns,andothers.

Mixingreturncurrents. Ifwirescarryingreturncurrentsfromdifferenttypesofsources,such

assignalsorDCandACgenerators,areconnectedtothesamegroundpointorhavea

commonconnectioninthereturnpaths,aninteractionofthecurrentswilloccur. This

interactionmaynotbeaproblem,oritcouldbeamajornonrepeatableanomaly.

Tominimizetheinteractionbetweenvariousreturncurrents,differenttypesofgroundsshouldbeidentifiedandused. Asaminimum,thedesignshoulduse

threegroundtypes: (1)ACreturns,(2)DCreturns,and(3)allothers.

Fordistributedpowersystems,thepowerreturnpointforanalternativepowersourcewouldbeseparated.

Forexample,inatwoACgeneratorsystem(oneontherightsideand

theotherontheleftside),iftherightACgenerator weresupplying

backuppowertoequipmentlocatedintheleftside,(leftequipment

rack)thebackupACgroundreturnshouldbelabeledACRight. The

returncurrentsfortheleftgeneratorshouldbeconnectedtoaground

pointlabeledACLeft.

[Endspeakernotes]

Slide117:Grounding,cont.

Designofgroundpathshouldbegivenasmuchattentionasotherleadsinthesystem Groundingshouldprovideaconstantimpedance Groundequipmentitemsexternallyevenwheninternallygrounded

o Avoiddirectconnectionstomagnesiumstructureforgroundreturn[Speakernotes]

Designof

ground

paths.

The

design

of

the

ground

return

circuit

should

be

given

as

much

attentionastheotherleadsofacircuit.

Constantimpedance. Arequirementforpropergroundconnectionsisthattheymaintainan

impedancethatisessentiallyconstant.

Groundreturncircuitsshouldhaveacurrentratingandvoltagedropadequateforsatisfactoryoperationoftheconnectedelectricalandelectronicequipment.


43/67

EMIproblems,thatcanbecausedbyasystemspowerwire,canbereducedsubstantiallybylocatingtheassociatedgroundreturnneartheoriginofthe

powerwiring(e.g.,circuitbreakerpanel)androutingthepowerwireandits

groundreturninatwistedpair.

Specialcareshouldbeexercisedtoensurereplacementongroundreturnleads.The

use

of

numbered

insulated

wire

leads

instead

of

bare

grounding

jumpers

mayaidinthisrespect.

Externalgroundingofequipmentitems. Ingeneral,equipmentitemsshouldhaveanexternal

groundconnection,evenwheninternallygrounded. Directconnectionstoamagnesium

structure(whichmaycreateafirehazard)mustnotbeusedforgroundreturn.

[Endspeakernotes]

Slide118:Grounding,cont. Heavycurrentgrounds

oAttach

to

individual

grounding

brackets

attached

to

aircraft

structure

with

a

propermetaltometalbond

o Accommodatenormalandfaultcurrentsofsystemwithoutcreatingexcessivevoltagedropordamagetostructure

o Givespecialattentiontocompositeaircraft[Speakernotes]

Heavycurrentgrounds. Powergroundconnectionsforgenerators,transformerrectifiers,

batteries,externalpowerreceptacles,andotherheavycurrentloadsmustbeattachedto

individualgroundingbracketsthatareattachedtoaircraftstructurewithapropermetalto

metalbondingattachment.

Thisattachmentandthesurroundingstructuremustprovideadequateconductivitytoaccommodatenormalandfaultcurrentsofthesystemwithout

creatingexcessivevoltagedropordamagetothestructure.

Atleastthreefasteners,locatedinatriangularorrectangularpattern,mustbeusedtosecuresuchbracketsinordertominimizesusceptibilitytoloosening

undervibration.

Ifthestructureisfabricatedofamaterialsuchascarbonfibercomposite(CFC),whichhasahigherresistivitythanaluminumorcopper,itwillbenecessaryto

provideanalternativegroundpath(s)forpowerreturncurrent.

[Endspeakernotes]

Slide119:Bonding

Equipmentbondingo Lowimpedancepathstoaircraftstructurerequiredforelectronicequipmentto

provideradiofrequencyreturncircuits

o FacilitatesreductioninEMIformostelectricalequipment


44/67

CasesofcomponentsthatproduceEMIshouldbegroundedtostructure[Speakernotes]

Equipmentbonding. Lowimpedancepathstoaircraftstructurearenormallyrequiredfor

electronicequipmenttoprovideradiofrequencyreturncircuitsandformostelectrical

equipmentto

facilitate

reduction

in

EMI.

The

cases

of

components

that

produce

electromagneticenergyshouldbegroundedtostructure.

Toensureproperoperationofelectronicequipment,itisparticularlyimportanttoconformthesystemsinstallationspecificationwheninterconnections,

bonding,andgroundingarebeingaccomplished.

[Endspeakernotes]

Slide120:Bonding,cont.

Metallicsurfacebondingo Electricallyconnectingconductiveexteriorairframecomponentsthroughmechanicaljoints,conductivehinges,orbondstraps

Protectsagainststaticchargesandlightningstrikes[Speakernotes]

Metallicsurfacebonding. Allconductingobjectsontheexterioroftheairframemustbe

electricallyconnectedtotheairframethroughmechanicaljoints,conductivehinges,orbond

strapscapableofconductingstaticchargesandlightningstrikes.

Exceptionsmaybenecessaryforsomeobjectssuchasantennaelements,whosefunctionrequiresthemtobeelectricallyisolatedfromtheairframe. Such items

shouldbeprovidedwithanalternativemeanstoconductstaticchargesand/or

lightningcurrents,

as

appropriate.

[Endspeakernotes]

Slide121:Bonding,cont. Staticbonds

o Requiredforallisolatedconductingpartswithareagreaterthan3in2 andalineardimensionover3"subjectedtoappreciableelectrostaticchargingdueto

precipitation,fluid,orairinmotion

Resistanceoflessthan1ohmwhencleananddryusuallyensuresstaticdissipationonlargerobjects

[Speakernotes]

Staticbonds. Allisolatedconductingpartsinsideandoutsidetheaircraft,havinganarea

greaterthan3in2andalineardimensionover3inches,thataresubjectedtoappreciable

electrostaticchargingduetoprecipitation,fluid,orairinmotion,shouldhaveamechanically

secureelectricalconnectiontotheaircraftstructureofsufficientconductivitytodissipate

possiblestaticcharges.


45/67

Aresistanceoflessthan1ohmwhencleananddrywillgenerallyensuresuchdissipationonlargerobjects. Higherresistancesarepermissibleinconnecting

smallerobjectstoairframestructure.

[Endspeakernotes]

Slide122:EWISIdentification

Necessaryfor:o Safetyofoperationo Safetytomaintenancepersonnelo Easeofmaintenance

Toidentifyperformancecapability,usewirematerialpartnumberandfivedigit/lettercodeidentifyingmanufacturer

[Speakernotes]

Purpose.The

proper

identification

of

EWIS

components

with

their

circuits

and

voltages

is

necessarytoprovidesafetyofoperation,safetytomaintenancepersonnel,andeaseof

maintenance.

Commonmanufacturermarkingprocess. Eachwireandcableshouldbemarkedwithapart

number. Itiscommonpracticeforwiremanufacturerstofollowthewirematerialpartnumber

withthefivedigit/letterC.A.G.E.codeidentifyingthewiremanufacturer. Usingthiscode,

existinginstalledwirethatneedsreplacementcanbeidentifiedastoitsperformance

capabilities. Thishelpstopreventtheinadvertentuseoflowerperformanceandunsuitable

replacementwire.

NOTE:Specialcareshouldbetakenwhenhotstampingwire. Servicehistoryhasshownproblemsassociatedwithhotstampingduetoinsulationdamagecaused

duringthe

process.

ThemethodofidentificationshouldnotimpairthecharacteristicsoftheEWIS. Originalwireidentification. Tofacilitateinstallationandmaintenance,retain

theoriginalwiremarkingidentification. Thewireidentificationmarksshould

consistofacombinationoflettersandnumbersthatidentifythewire,thecircuit

itbelongsto,itsgaugesize,andanyotherinformationtorelatethewiretoa

EWISdiagram. Allmarkingsshouldbelegibleinsize,type,andcolor.

IdentificationandinformationrelatedtotheEWISdiagrams. Thewireidentificationmarkingshouldconsistofsimilarinformationtorelatethewireto

aEWISdiagram.

[Endspeaker

notes]

Slide123:EWISIdentification,cont. Wireidentificationmarksidentifywire,circuit,andgaugesize Markingsshouldbelegibleinsize,type,andcolorat15inchmaximumintervalsalong

thewire(directlyonwireorindirect[sleeve/tag])


46/67

Lessthan3inchesneedsnomarkingo Readablewithoutremovingclamps,ties,orsupportingdevices

[Speakernotes]

MarkingEWISinaircraft. Identificationmarkingsgenerallyareplacedateachendofthewire

andat

15

inch

maximum

intervals

along

the

length

of

the

wire.

Wireslessthan3incheslongneednotbeidentified. Wires3to7inchesinlengthshouldbeidentifiedapproximatelyatthecenter. Addedidentificationmarkersleevesshouldbelocatedsothatties,clamps,or

supportingdevicesneednotberemovedinordertoreadtheidentification.

Thewireidentificationcodemustbeprintedtoreadhorizontally(fromlefttoright)orvertically(fromtoptobottom). Thetwomethodsofmarkingwireor

cableareasfollows:

(1) Directmarkingisaccomplishedbyprintingthecablesouter

covering.

(2)

Indirect

marking

is

accomplished

by

printing

a

heat

shrinkable

sleeveandinstallingtheprintedsleeveonthewireorcablesouter

covering. Indirectmarkedwireorcableshouldbeidentifiedwithprinted

sleevesateachendandatintervalsnotlongerthan6feet. Theindividual

wiresinsideacableshouldbeidentifiedwithin3inchesoftheir

termination.

Themarkingshouldbepermanentsuchthatenvironmentalstressesduringoperationandmaintenancedonotadverselyaffectlegibility.

[Endspeakernotes]

Slide124:MarkingaWireBundle

[Graphic]

Firstimageshowsbundlewithnomarkingandthesecondimageshowsbundlemarkedwith

identificationnumberonatag.

[Endgraphic]

[Speakernotes]

Therecanbeseriousrepercussionswhenthereisasituationinwhichanumberofunmarked

cablesaredisconnected.Whenthecablesreconnected,thechancesarehighthattheywillbe

connectedincorrectly,

thus

causing

numerous

problems.

[Endspeakernotes]

Slide125:Connectors

Manytypes,howevercrimpedcontactsgenerallyused


47/67

o Circulartypeo Rectangularo Moduleblocks

Selectedtoprovidemaximumdegreeofsafetyandreliabilitygivenelectricalandenvironmentalrequirements

o Useenvironmentallysealedconnectorstopreventmoisturepenetration[Speakernotes]

Connectors. ThenumberandcomplexityofEWIShaveresultedinanincreaseduseofelectrical

connectors. Theproperchoiceandapplicationofconnectorsisasignificantpartoftheaircraft

EWISsystem. Connectorsshouldbekepttoaminimum,selected,andinstalledtoprovidethe

maximumdegreeofsafetyandreliabilitytotheaircraft. Fortheinstallationofanyparticular

connectorassembly,thespecificationofthemanufacturershouldbefollowed.

Purposeandtypes. Theconnectorusedforeachapplicationshouldbeselectedonlyaftera

carefuldeterminationoftheelectricalandenvironmental requirements. Considerthesize,

weight,

tooling,

logistic,

maintenance

support,

and

compatibility

with

standardization

programs.

Foreaseofassemblyandmaintenance,connectorsusingcrimpedcontactsaregenerallychosenforallapplicationsexceptthoserequiringahermeticseal.

Areplacementconnectorofthesamebasictypeanddesignastheconnectoritreplacesshouldbeused.

Withacrimptypeconnectorforanyelectricalconnection,theproperinsertion,orextractiontoolshouldbeusedtoinstallorremovewiresfromsucha

connector. Refertomanufactureroraircraftinstructionmanual.

Aftertheconnectorisdisconnected,inspectitforloosesolderedconnectionstopreventunintentionalgrounding.

Connectorsthataresusceptibletocorrosiondifficultiesmaybetreatedwithachemicallyinertwaterproofjellyoranenvironmentallysealedconnectormaybe

used.

NOTE: AlthoughnotrequiredbyAC43.131b,moistureproofconnectorsshouldbeusedinallareasoftheaircraft,includingthecabin. Servicehistoryindicates

thatmostconnectorfailuresoccurduetosomeformofmoisturepenetration.

Eveninthepressurized,environmentallycontrolledareasofthecockpitand

cabin,moisturecanoccurduetorainintheplanetypeofcondensationthat

generallyisaprobleminallmoderntransportcategoryaircraft.

[Endspeaker

notes]

Slide126:CircularConnectors

[graphic]

Threeimagesshowing6differenttypesofcircularconnectors

[Endgraphic]


48/67

[Speakernotes]

AlthoughAC43.131bdoesnotaddresspinlayoutdesignaspects,considerationshouldbe

giventothedesignofthepinarrangementtoavoidsituationswherepintopinshortscould

resultinmultiplelossoffunctionsand/orpowersupplies. Forexample,youwouldavoid115

Vac,400Hzbeinglocatedadjacenttolowpowerwires,suchas28and5Vdc.

Awide

variety

of

circular

environment

resistant

connectors

are

used

in

applications

where

theywillprobablybesubjectedtofluids,vibration,thermal,mechanicalshock,corrosive

elements,etc. Inaddition,firewallclassconnectorsincorporatingthesesamefeaturesshould

beabletopreventthepenetrationofthefirethroughtheaircraftfirewallconnectoropening

andcontinuetofunctionwithoutfailureforaspecifiedperiodoftimewhenexposedtofire.

Hermeticconnectorsprovideapressuresealformaintainingpressurizedareas.

WhenEMI/RFIprotectionisrequired,specialattentionshouldbegiventotheterminationofindividualandoverallshields. Backshelladaptersdesignedfor

shieldtermination,connectorswithconductivefinishes,andEMIgrounding

fingersareavailableforthispurpose.

[Endspeakernotes]

Slide127:CircularConnectors,cont.[graphic]

Imagesshows3differentlockingdevices

[Endgraphic]

[Speakernotes]

Inmediumorhighvibrationareasitmaybenecessarytoprovidealockingdevicetokeepthe

connectorsfrom

loosening.

[Endspeakernotes]

Slide128:ImproperLockWireInstallation

[Speakernotes]

Thisslideshowsalockwireimproperlyinstalled. Thelockwireisinstalledonthe"loosening

sideoftheconnector;itshouldbeonthelighteningside.

[Endspeaker

notes]

Slide129:ProperLockWireInstallation

[Speakernotes]


49/67

Thisisanexampleofaproperlyinstalledlockwireonthelighteningside.

[Endspeakernotes]

Slide130:

Rectangular

Connectors

[graphic]

Imageshowsfourtypesofrectangularconnectors

[Endgraphic]

[Speakernotes]

Rectangularconnectorsaretypicallyusedinapplicationswhereaverylargenumberofcircuits

areaccommodatedinasinglematedpair. Theyareavailablewithagreatvarietyofcontacts,

whichcanincludeamixofstandard,coaxial,andlargepowertypes. Couplingisaccomplished

byvariousmeans.

Smallertypesaresecuredwithscrewsthatholdtheirflangetogether.

Larger

ones

have

integral

guide

pins

that

ensure

correct

alignment,

or

jackscrews

thatbothalignandlocktheconnectors.

Rackandpanelconnectorsuseintegralorrackmountedpinsforalignmentandboxmounting

hardwareforcouplings.

[Endspeakernotes]

Slide131:ModuleBlocks(TerminalBlocks)

[Graphic]

Showstwotypesofmodularblocks

[Endgraphic]

[Speakernotes]

Moduleblocksacceptcrimpedcontactssimilartothoseonconnectors. Someuseinternal

busingtoprovideavarietyofcircuitarrangements.

Moduleblocks(orterminalblocks)areusefulwhereanumberofwiresareconnectedforpowerorsignaldistribution.Whenusedasgroundingmodules,

theysaveandreducehardwareinstallationontheaircraft.

Standardizedmodulesareavailablewithwireendgrommetsealsforenvironmentalapplicationsandaretrackmounted.

[Endspeakernotes]

Slide132:TerminalBlockGrommetDistortion

[Speakernotes]


50/67

Forcomplexwirebreakoutsthatareterminatedintoterminalblocks,caremustbetakento

allowenoughslacktopreventexcessiveforcesfrompullingtheterminatedwiresthatare

insertedintotheterminalblock.

Thisconditioncanleadtoterminalblockgrommetdistortion,whichcanleadtowiredamageorawirethatwillbepulledfreefromtheterminalblock.

[Endspeaker

notes]

Slide133:GrommetDistortion

[Graphic]

FirstimageshowsImproper:grommetdistortionduetotightwires;notenoughslack.Second

imageshowsProper:noexcessivetensiononwires;enoughslacktoavoidgrommetdistortion

[Endgraphic]

Slide

134:

Conduits

Purposeo Mechanicalprotectionofwiresandcableso Groupingandroutingwires

Standardso Absenceofabrasionatendfittingso Properclampingo Adequatedrainholesfreeofobstructionso Minimizeddamagefrommovingobjectso Properbendradii

[Speakernotes]

Purpose. Primarilythepurposeofconduitsisformechanicalprotectionofcablesorwires.

Secondarily,conduitsareusedforenvironmentalprotectionandgroupingofwiresbysignal

type.

Standards

Conduitshouldbeinspectedfor: properendfittings;absenceofabrasionattheendfittings;properclamping;distortion;adequatedrainholesthatarefreeof

dirt,grease,orotherobstructions;andfreedomfromabrasionordamagedueto

movingobjects,suchasaircraftcontrolcablesorshiftingcargo.

Sizeofconduit. Conduitsizeshouldbeselectedforaspecificwirebundleapplication

to

allow

for

ease

in

maintenance,

and

possible

future

circuit

expansion,byspecifyingtheconduitinnerdiameter(I.D.)about25percent

largerthanthemaximumdiameterofthewirebundle.

Conduitfittings.Wireisvulnerabletoabrasionatconduitends. Suitablefittingsshouldbe

affixedtoconduitendsinsuchamannerthatasmoothsurfacecomesincontactwiththewire.

Whenfittingsarenotused,theendoftheconduitshouldbeflaredtopreventwireinsulation

damage. Conduitshouldbesupportedbyuseofclampsalongtheconduitrun.


51/67

[Endspeakernotes]

Slide135:ConduitInstallationGuidelines

Donotlocateconduitwhereserviceormaintenancepersonnelmightuseashandholdor

footstep

Provideinspectabledrainholesatthelowestpointinconduitrunremovedrillingburrscarefully

Supportconduittopreventchafingagainststructureandavoidstressingendfittings[Speakernotes]

Conduitinstallation. Conduitproblemscanbeavoidedbyfollowingtheseguidelines:

Donotlocateconduitwhereserviceormaintenancepersonnelmightuseitasahandholdorfootstep.

Provideinspectabledrainholesatthelowestpointinaconduitrun. Drillingburrs

should

be

carefully

removed.

Supportconduittopreventchafingagainststructureandtoavoidstressingits

endfittings.

[Endspeakernotes]

Slide136:ConduitCovering

[Graphic]

Firstimageshowsdamagedconduitcovering.Secondimageshowsanacceptableconduit

coveringwithnodamage

[Endgraphic]

[Speakernotes]

FODisabigproblemwithdamagedconduitcovering.

[Endspeakernotes]

Slide137:WireInsulationSelection

Chosecharacteristicsbasedonenvironmento Abrasionresistanceo Arcresistanceo Corrosionresistanceo Cutthroughstrengtho Dielectricstrengtho Flameresistanto Mechanicalstrength


52/67

o Smokeemissiono Fluidresistanceo Heatdistortion

[Speakernotes]

Environmentalcharacteristics. Asshowninthisslide,therearemanyinsulationmaterialsand

combinationsusedinaircraftwiring.Wireinsulationcharacteristicshouldbechosenbasedon

meetingFAAflameresistanceandsmokeemissionrequirements(25.869)andtheenvironment

inwhichthewireistobeinstalled.

[Endspeakernotes]

Slide138:FlameResistantInsulatingMaterials

Polymer MilSpec

PTFE 22759/12

ETFE 22759/16

Aromaticpolyamide 81381

Composite 22759/8092

[Speakernotes]

Thesearethefourmostcommontypesofinsulationmaterialsusedinaircrafttoday. Allofthe

wireinsulatingmaterialsinthisslidemeettheminimumFAAsmokeandflammability

standards.

[Endspeakernotes]

Slide139:SelectingInsulatingMaterials

FFAACCTT:: Thereisnnooppeerrffeeccttiinnssuullaattiioonnssyysstteemmforaerospacewireandcable

TThheeddeessiiggnneerrssttaasskk::

Considertradeoffstosecurebestbalanceofproperties Considerinfluenceofdesign,

installationand

maintenance

..........ffoorreeaacchhaapppplliiccaattiioonn!!


53/67

Slide140:HowtoChooseWireInsulation

Seekthebestbalanceofproperties:o Electricalo Mechanicalo Chemicalo Thermal

PPlluuss

Nonflammabilityandlowsmoke

Slide141:ComparativePropertiesofWireInsulationSystems

Ranking1ismostdesirableand4istheleastdesirable

RelativeRanking 1 2 3 4

Weight

PIE

TFE

COMP

PTFE

Temperature PTFE COMP PI ETFE

Abrasionresistance PI ETFE COMP PTFE

Cutthroughresistance PI COMP ETFE PTFE

Chemicalresistance PTFE ETFE COMP PI

Flammability PTFE COMP PI ETFE

Smokegeneration PI COMP PTFE ETFE

Flexibility PTFE ETFE COMP PI

Creep(attemperature) PI COMP PTFE ETFE

Arcpropagation

resistance

PTFE ETFE COMP PI

[Speakernotes]

PI[AromaticPolyimide(KAPTON)] (milspec81381)

Desirableproperties: abrasion/cutthrough,lowsmoke/nonflame,weight/space

Limitations: arctrackresistance,flexibilityETFE(TEFZEL) (milspec22759/16)

Desirableproperties: chemicalresistance,abrasionresistance,easeofuse Limitations: hightemperature,cutthrough, thermalrating(150C)

Composite

(TKT)

(mil

spec

22759/80

92)

Desirableproperties:hightemperaturerating(260C),cutthroughresistance,arctrackresistance

Limitations:outerlayerscuffingPTFE(TEFLON) (milspec22759/12)

Desirableproperties: 260Cthermalrating,lowsmoke/nonflame,highflexibility

Limitations: Cutthroughresistance,creepattemperature


54/67

[Endspeakernotes]

Slide142:ConclusiononInsulation

Aircraftdesignercanchooseamongmanypolymericmaterials Physicalandchemicalpropertiesareequallyimportant Safestsystemcombinesbalanceofpropertieswithinherentflameand/orsmoke

resistance

Slide143:AC25-16:ElectricalFaultandFireDetection

SupplementsexistingguidanceprovidedinAC43.131b Shouldapplytonewairplanes,aswellasmodifications Notintendedtotaketheplaceofinstructionsorprecautionsprovidedby

aircraft/equipmentmanufacturers

[Speakernotes]

ThepurposeofAC2516,ElectricalFaultAndFirePrevention,istoprovideinformationon

electricallycausedfaults,overheat,smoke,andfireintransportcategoryairplanes. Acceptable

meansareprovidedtominimizethepotentialfortheseconditionstooccur,andtominimizeor

containtheireffectswhentheydooccur. Anapplicantmayelecttouseanyothermeansfound

tobeacceptablebytheFAA.

ThisACiscurrentlybeingreviewedandwillberevisedbasedonrecentservicehistoryand

ATSRACrecommendations.

[End

speaker

notes]

Slide144:AC25-16: CircuitProtectionDevices(CPDs)

Circuitbreakerresetso Cansignificantlyworsenanarcingevento Crewshouldonlyattempttoresetatrippedbreakeriffunctionisabsolutely

required

InformationshouldbeprovidedinAFMsorAFMrevisionsorsupplements

[Speakernotes]

InformationshouldbeprovidedinFAAapprovedAirplaneFlightManuals(AFM)orAFM

revisionsorsupplementsthatthecrewshouldonlyattempttorestoreanautomatically

disconnectedpowersourceorresetorreplaceanautomaticallydisconnectedcircuitprotection

device(CPD)thataffectsflightoperationsorsafety.

NOTE: Itisstronglyrecommendedthatcircuitbreakersfornonessentialsystemsnotberesetinflight.


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MosttransportOAMsandoperatorsarerevisingtheirprocedurestonotallowcircuitbreaker

resetsinflightfollowingacircuitbreakertripevent. Servicehistoryhasshownthatresettinga

circuitbreakercangreatlyinfluencethedegreeofarcingdamagetotheEWIS. Eachsuccessive

attempttorestoreanautomaticallydisconnectedCPD,canresultinprogressivelyworsening

effectsfromarcing.

[Endspeaker

notes]

Slide145:ArcTrackingandInsulationFlashover

(Causedbymultiplecircuitbreakerresets)[Graphic]

showswiringburnedandbrokenfromarcing

[Endgraphic]

[Speakernotes]

Thispictureshowstheeffectsofmultiplecircuitbreakerresets. Inthiscase,theoriginalarcing

eventwas

not

able

to

be

determined

due

to

the

severe

secondary

damage

following

the

circuit

breakerresets.

[Endspeakernotes]

Slide146:EWISSeparation

Regulatoryrequirementso Sections25.1707,25.1709,25.903(d),25.631

Manufacturersstandardso Power/signalwireseparation

EMI

concerns

[Speakernotes]

EWISseparation/segregationisafundamentaldesigntechniqueusedtoisolatefailureeffects

suchthatcertainsinglefailuresthatcancompromiseredundancyareminimized. EWIS

separationisalsousedtocontroltheeffectsofEMIinaircraftEWIS.

Fromaregulatorystandpoint,wehaveregulationsinplacethatmayinfluenceEWISdesignwithrespecttoseparation/segregation.

Inaddition,manufacturersmayhavecompanydesignstandardswhichestablishEWISseparationrequirementswithrespecttopowerandsignalroutingwhich

areusuallydrivenfromaEMIstandpoint.

Thenext

few

slides

briefly

present

the

primary

regulations

associated

with

EWIS

separation/segregation.

[Endspeakernotes]

Slide147:SystemSeparation:EWIS25.1707

AppliestoeachEWISonairplane


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RequiresadequatephysicalseparationbetweenEWISandcertainairplanesystemsknowntohavepotentialforcreatingahazardouscondition,forexample:

o Fuelsystemso Hydraulicsystemso Oxygensystemso Water/wastesystems

Slide148:SystemSeparation:EWIS25.1707,cont.

Adequatephysicalseparationmustbeachievedbyseparationdistanceorbyabarrierthatprovidesprotectionequivalenttothatseparationdistance

Hazardous mustperformaqualitativedesignassessmentofinstalledEWISo Useengineering&manufacturingjudgmento EvaluaterelevantservicehistorytodecidewhetheranEWIS,anyothertypeof

system,or

any

structural

component

could

fail

so

that

acondition

affecting

the

airplanesabilitytocontinuesafeoperationcouldresult

Slide149:SystemSafety:EWIS2

ewis job-aid 2.0 508-accessible

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