Bibliography of PublicationsHuman Factor MaintenanceGood Practices in Visual InspectionDrury.docx

Bibliography of PublicationsHuman Factor MaintenanceGood Practices in Visual InspectionDrury.docx

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BibliographyofPublicationsHumanFactorMaintenanceGoodPracticesinVisualInspectionDrury

gOODpRACTICESINVISUALiNSPECTION

ColinG.Drury

AppliedErgonomicsGroupInc.

98MeadowbrookRoad

Willimasville,NY14221-5029

JeanWatson

FederalAviationAdministration

FlightStandardsService

May2002

TableofContents

1.0ExecutiveSummary2

2.0Objectivesandsignificance3

2.1Objectives3

2.2Significance3

3.0Introduction3

3.1VisualInspectionDefined4

3.2CharacteristicsofVisualInspection4

4.0TechnicalBackground:

NDIreliabilityandhumanfactors7

4.1NDIReliability7

4.2HumanFactorsinInspection13

5.0ResearchObjectives21

6.0Methodology21

6.1HierarchicalTaskAnalysis22

7.0results25

7.1DetailedGoodPractices25

7.2ControlMechanisms25

8.Conclusions51

Appendix1-TaskdescriptionandtaskanalysisofeachprocessinVISUALinsepction59

Appendix2HUMANFACTORSBESTPRACTICESFOReachprocessinvisualinspection78

1.0ExecutiveSummary

VisualInspectionisthesinglemostfrequently-usedaircraftinspectiontechnique,butisstillerror-prone.Thisprojectfollowspreviousreportsonfluorescentpenetrantinspection（FPI）andborescopeinspectioninderivinggoodpracticestoincreasethereliabilityofNDIprocessesthroughgenerationofgoodpracticesbasedonanalysisofthehumanroleintheinspectionsystem.

Inspectioninaviationismainlyvisual,comprising80%ofallinspectionbysomeestimates,andaccountingforover60%ofADnoticesina2000study.ItisusuallymorerapidthanotherNDItechniques,andhasconsiderableflexibility.Althoughitisusuallydefinedwithreferencetotheeyesandvisiblespectrum,infactVisualInspectionincludesmostothernon-machine-enhancedmethods,suchasfeelorevensound.Itisperhapsbestcharacterizedasusingtheinspectors’senseswithonlysimplejobaidssuchasmagnifyingloupesormirrors.Assuch,VisualInspectionformsavitalpartofmanyotherNDItechniqueswheretheinspectormustvisuallyassessanimageoftheareainspected,e.g.inFPIorradiography.AnimportantcharacteristicofVisualInspectionisitsflexibility,forexampleinbeingabletoinspectatdifferentintensitiesfromwalk-aroundtodetailedinspection.Fromavarietyofindustries,includingaviation,weknowthatwhenthereliabilityofvisualinspectionismeasured,itislessthanperfect.Visualinspectors,likeotherNDIinspectors,makeerrorsofbothmissingadefectandcallinganon-defect（missesandfalsealarmsrespectively）.

ThisreportusedaHierarchicalTaskAnalysis（HTA）techniquetobreakthetaskofVisualInspectionintofivemajorfunctions:

Initiate,Access,Search,DecisionandResponse.Visitstorepairfacilitiesanddatacollectedinpreviousprojectswereusedtorefinetheseanalyses.TheHTAanalysiswascontinuedtogreaterdepthtofindpointsatwhichthedemandsofthetaskwereill-matchedtothecapabilitiesofhumaninspectors.Thesearepointswhereerrorpotentialishigh.Foreachofthesepoints,HumanFactorsGoodPracticeswerederived.Overall,58suchGoodPracticesweredeveloped,bothfromindustrysourcesandhumanfactorsanalyses.ForeachoftheseGoodPractices,aspecificsetofreasonswereproducedtoshowwhythepracticewasimportantandwhyitwouldbehelpful.

Acrossthewholeanalysis,anumberofmajorfactorsemergedwhereknowledgeofhumanperformancecanassistdesignofVisualInspectiontasks.Thesewerecharacterizedas:

Timelimitsoncontinuousinsepctionperformance

Thevisualenvironment

Postureandvisualinspectionperformance

Theeffectofspeedofworkingoninspectionaccuracy

Trainingandselectionofinspectors

Documentationdesignforerrorreduction

Eachiscoveredinsomedetail,astheprinciplesapplyacrossavarietyofinspectiontasksincludingvisualinspection,andacrossmanyofthefunctionswithineachinspectiontask.

Overall,these58specificGoodPracticesandsixbroadfactorshelpinspectiondepartmentstodesigninspectionjobstominimizeerrorrates.Manycanbeapplieddirectlytothe“reading”functionofotherNDItechniquessuchasFPIorradiography.

2.0Objectivesandsignificance

ThisstudywascommissionedbytheFederalAviationAdministration（FAA）,OfficeofAviationMedicineforthefollowingreasons:

2.1Objectives

Objective1.Toperformadetailedhumanfactorsanalysisofvisualinspection.

Objective2.TousetheanalysistoprovideHumanFactorsguidance（bestpractices）toimprovetheoverallreliabilityofvisualinspection.

2.2Significance

Visualinspectioncomprisesthemajorityoftheinspectionactivitiesforaircraftstructures,powerplantsandsystems.Likeallinspectionmethods,visualinspectionisnotperfect,whetherperformedbyhuman,byautomateddevicesorbyhybridhuman/automationsystems.Whilesomeinspectionprobabilityofdetection（PoD）dataisavailableforvisualinspectionmostrecommendationsforvisualinspectionimprovementarebasedonunquantifiedanecdotesorevenopiniondata.Thisreportusesdatafromvariousnon-aviationinspectiontaskstohelpquantifysomeofthefactorsaffectingvisualinspectionperformance.Thehumanfactorsanalysisbringsdetaileddataonhumancharacteristicstothesolutionofinspectionreliabilityproblems.Asaresultofthisresearch,aseriesofbestpracticesareavailableforimplementation.Thesecanbeusedinimprovedtrainingschemes,procedures,designofequipmentandtheinspectionenvironmentsoastoreducetheoverallincidenceofinspectionerrorinvisualinspectiontasksforcriticalcomponents.

3.0Introduction

Visualinspectionisthemostoftenspecifiedtechniqueforairframes,powerplantsandsystemsinaviation.TheFAA’sAdvisoryCircular43-204（1997）1onVisualInspectionforAircraftquotesGoransonandRogers（1983）2totheeffectthatover80%ofinspectionsonlargetransportcategoryaircraftarevisualinspections（page1）.ArecentanalysisofAirworthinessDirectivesissuedbytheFAAfrom1995to1999（McIntireandMoore,1993）3foundthat561outof901inspectionADs（62%）specifiedvisualinspection.Infact,whenthesenumbersarebrokendownbycategory,only54%ofADsarevisualinspectionforlargetransportaircraft,versus75%fortheothercategories（smalltransport,generalaviation,rotorcraft）.

3.1VisualInspectionDefined

Thereareanumberofdefinitionsofvisualinspectionintheaircraftmaintenancedomain.Forexample,initsAC-43-204,1theFAAusesthefollowingdefinition:

“Visualinspectionisdefinedastheprocessofusingtheunaidedeye,aloneorinconjunctionwithvariousaids,asthesensingmechanismfromwhichjudgmentsmaybemadeabouttheconditionofaunittobeinspected.”

TheASNT’sNon-DestructiveTestingHandbook,Volume8（McIntireandMoore,1993）3hasanumberofpartialdefinitionsindifferentchapters.UnderSection1,Part1,DescriptionofVisualandOpticalTests（page2）,itdefines:

“….Visualandopticaltestsarethosethatuseprobingenergyfromthevisibleportionoftheelectromagneticspectrum.Changesinthelight’spropertiesaftercontactwiththetestobjectmaybedetectedbyhumanormachinevision.Detectionmaybeenhancedormadepossiblebymirrors,borescopesorothervision-enhancingaccessories.”

Morespecificallyforaircraftinspection,onpage292inSection10,Part2,foroptically-aidedvisualtestingofaircraftstructure,visualinspectionisdefinedbywhatitcandoratherthanwhatitis:

“visualtestingistheprimarymethodusedinaircraftmaintenanceandsuchtestscanrevealavarietyofdiscontinuities.Generally,thesetestscoverabroadareaoftheaircraftstructure.Moredetailed（smallarea）testsareconductedusingopticallyaidedvisualmethods.Suchtestsincludetheuseofmagnifiersandborescopes.”

However,thereismoretovisualinspectionthanjustvisualinformationprocessing.

3.2CharacteristicsofVisualInspection

Asusedinaviation,visualinspectiongoesbeyond“visual,”i.e.beyondtheelectro-magneticspectrumofvisiblewavelengths.Inasense,itisthedefaultinspectiontechnique:

ifaninspectionisnotoneofthespecificNDItechniques（eddycurrent,X-ray,thermography,etc.）thenitisusuallyclassifiedasvisualinspection.Thus,othersensescanbeusedinadditiontothevisualsense.Forexample,visualinspectionoffastenerstypicallyincludestheactionoffeelingforfastener/structurerelativemovement.Thisinvolvesactiveattempts,usingthefingers,tomovethefastener.Inhumanfactors,thiswouldbeclassifiedastactileormoregenerallyhapticinspection.Adifferentexampleischeckingcontrolcablesforfrayingbyslidingaragalongthecabletoseewhetheritsnags.Otherexamplesincludethesenseofsmell（fluidleakage,overheatedcontrolpivots）,noise（inbearingsordoorhinges）andfeelofbacklash（inengineblades,alsoinhingesandbearings）.Thepointisthat“visual”inspectionisonlypartiallydefinedbythevisualsense,eventhoughvisionisitsmainfocus.

Visualinspectionisofthegreatestimportancetoaviationreliability,forairframes,powerplantsandsystems.Itcanindeeddetectavarietyofdefects,fromcracksandcorrosiontoloosefasteners,ill-fittingdoors,wearandstretchingincontrolrunsandmissingcomponents.Itisubiquitousthroughoutaircraftinspection,sothatfewinspectorswillperformaspecializedNDItaskwithoutatleasta“generalvisualinspection”oftheareaspecified.Visualinspectionalsohastheabilitytofinddefectsinassembledstructuresaswellascomponents.Withremotesensing,e.g.borescopesandmirrors,thisinsitucharacteristiccanbeextendedconsiderably.Visualinspectionistheoldestinspectiontechnique,inusefr