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Subject:COMPOSITEAIRCRAFTSTRUCTUREDate:9/8/09Initiatedby:AIR-100ACNo:20-107BChange:1.PurposeofthisAdvisoryCircular(AC).ThisACsetsforthanacceptablemeans,butnottheonlymeansofshowingcompliancewiththeprovisionsofTitle14oftheCodeofFederalRegulations(14CFR)parts23,25,27,and29regardingairworthinesstypecertificationrequirementsforcompositeaircraftstructuresinvolvingfiberreinforcedmaterials,e.g.,carbonandglassfiberreinforcedplastics.Guidanceinformationisalsopresentedonthecloselyrelateddesign,manufacturing,andmaintenanceaspects.Theinformationcontainedhereinisforguidancepurposesandisnotmandatoryorregulatoryinnature.2.ToWhomthisACApplies.TheaudienceofthisACmayincludeapplicants,certificate/approvalholders,partsmanufacturers,materialsuppliers,maintenance,andrepairorganizations.3.Cancellation.AC20-107A,CompositeAircraftStructure,datedApril25,1984,iscancelled.4.RelatedRegulationsandGuidance.Thematerialcontainedhereinappliestonormal,utility,acrobatic,commuter,andtransportcategoryaircrafttypecertificatedunderCivilAviationRegulations(CARs)3,4b,6,7;and14CFRparts23,25,27,29;anditisproducedincompliancewith14CFRpart21,§§21.125,or21.143asmaybeappropriate.Thesectionsof14CFR,parts23,25,27,and29applicabletoeachparagraphofthisACarelistedinAppendix1.OthersupportingguidancerelevanttotheACisalsoprovidedinAppendix1.5.General.a.TheproceduresoutlinedinthisACprovideguidancematerialforcompositestructures,particularlythosethatareessentialinmaintainingtheoverallflightsafetyoftheaircraft(“criticalstructure”asdefinedinAppendix2),andareconsideredacceptabletotheFAAforshowingcompliancewithcertificationrequirementsofcivilcompositeaircraft.Thiscircularispublishedtoaidintheevaluationofcertificationprogramsforcompositeapplicationsandtoreflectthecurrentstatusofcompositetechnology.ItisexpectedthatthiscircularwillbemodifiedU.S.DepartmentofTransportationFederalAviationAdministrationAdvisoryCircular9/8/09AC20-107BPage2periodicallytoreflectthecontinuedevolutionofcompositetechnologyandthedatacollectedfromserviceexperienceandexpandingapplications.b.Therearefactorsuniquetothespecificcompositematerialsandprocessesusedforagivenapplication.Forexample,theenvironmentalsensitivity,anisotropicproperties,andheterogeneousnatureofcompositescanmakethedeterminationofstructuralfailureloads,modes,andlocationsdifficult.Thereliabilityofsuchevaluationdependsonrepeatablestructuraldetailscreatedbyscaledmanufacturingorrepairprocesses.Theextentoftestingand/oranalysismaydifferforastructuredependinguponthecriticalitytoflightsafety,expectedserviceusage,thematerialandprocessesselected,thedesignmargins,thefailurecriteria,thedatabaseandexperiencewithsimilarstructures,andonotherfactorsaffectingaparticularstructure.ItisexpectedthatthesefactorswillbeconsideredwheninterpretingthisACforuseonaspecificapplication.c.DefinitionsoftermsusedinthisACcanbefoundinAppendix2.6.MaterialandFabricationDevelopment.Allcompositematerialsandprocessesusedinstructuresarequalifiedthroughenoughfabricationtrialsandteststodemonstrateareproducibleandreliabledesign.Oneoftheuniquefeaturesofcompositeconstructionisthedegreeofcareneededintheprocurementandprocessingofcompositematerials.Thefinalmechanicalbehaviorofagivencompositematerialmayvarygreatlydependingontheprocessingmethodsemployedtofabricateproductionparts.Specialcareneedstobetakenincontrollingboththematerialsbeingprocuredandhowthematerialisprocessedoncedeliveredtothefabricationfacility.Regulatoryrequirementsin14CFR,parts2X,§§2x.603and2x.605specifytheneedtoprocureandprocessmaterialsunderapprovedmaterialandprocessspecificationsthatcontrolthekeyparametersgoverningperformance.14CFR,parts2X,§§2x.609and2x.613outlinesaneedtoprotectstructuresagainstthedegradationpossibleinservice.Theyalsorequirethatthedesignaccountforanychangesinperformance(e.g.,environmentalandvariabilityeffects)permittedbymaterialandprocessspecifications.a.MaterialandProcessControl.(1)Specificationscoveringmaterial,materialprocessing,andfabricationproceduresareestablishedtoensureabasisforfabricatingreproducibleandreliablestructure.Materialspecificationsarerequiredtoensureconsistentmaterialisbeingprocured,andbatchacceptancetestingorstatisticalprocesscontrolsareusedtoensurematerialpropertiesdonotdriftovertime.Specificationscoveringprocessingproceduresshouldbedevelopedtoensurethatrepeatableandreliablestructureisbeingmanufactured.Themeansofprocessingqualificationandacceptancetestsdefinedineachmaterialspecificationshouldberepresentativeoftheexpectedapplicablemanufacturingprocess.Theprocessparametersforfabricatingtestspecimensshouldmatchtheprocessparametersusedinmanufacturingactualproductionpartsascloselyaspossible.Bothtestandproductionpartsmustconformtomaterialandprocessspecifications.(2)Oncethefabricationprocesseshavebeenestablished,changesshouldnotoccurunlessadditionalqualification,includingtestingofdifferencesiscompleted(refertoAppendix9/8/09AC20-107BPage33).Itisimportanttoestablishprocessingtolerances;materialhandlingandstoragelimits;andkeycharacteristics,whichcanbemeasuredandtrackedtojudgepartquality.(3)