Designation:F319−09(Reapproved2014)StandardPracticeforPolarizedLightDetectionofFlawsinAerospaceTransparencyHeatingElements1ThisstandardisissuedunderthefixeddesignationF319;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONElectricallyconductivecoatingsusedinaerospacetransparenciesforheatingpurposesmaycontainflawsresultingfromimperfectionsofmaterials,imperfectionsofmanufacturingtechniques,handlingdamage,orcontamination.Flawsmaydevelopbefore,during,oraftercoatingandprocessingandusuallyappearashairlinecracks,scratches,orpinholes.Whentheseflawsareofsufficientsize,hotspotscanoccurasaresultofdisruptionandconcentrationoftheflowofelectricalcurrentadjacenttotheflaws.Thesehotspotsmayresultinreducedservicelifeofthetransparency.Hotspotflawsinthetransparencymayalsoproduceundesirabletemporarydistortionofvisionduringpoweredoperationoftheheaterandpermanentvisiondistortionafterrepeatedcyclingoftheheater.Polarizedlightiswidelyusedtodetectelectricallyconductivecoatingflawsduringaerospacetransparencyprocessing.1.Scope1.1Thispracticecoversastandardprocedurefordetectingflawsintheconductivecoating(heaterelement)bytheobservationofpolarizedlightpatterns.1.2Thispracticeappliestocoatingsonsurfacesofmono-lithictransparenciesaswellastocoatingsimbeddedinlaminatedstructures.1.3ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.ForspecificprecautionarystatementsseeSection6.2.Terminology2.1Definitions:2.1.1transparentconductivecoating—atransparentthinfilmofelectricallyconductivematerialsuchas...
