Electrical Short Circuit/Arcing of Aged Aircraft Wiring

Table 7. Description of alternate abrasion configurationsDescription Results Comments IllustrationTwo Bundles that arealigned much like thelongitudinal abraderdescribe in the maintext but in this case themetal shavings areglued to one of thebundles with a epoxy.This test results indamage to theinsulation withrelatively thinshavings. Flash eventscan occur.The gluing of theshaving may mimic theadhesion of the shavingto bundle byanti-corrosion fluidfound in the field .However, theintroduction of a foreignagent such as epoxy isundesirable .In this test a shaving isplaced between thewires in a bundle. Oneend of the bundle is fixwhile the other ismoved back and forthperpendicular to theaxis of the wire bundle.While there is somerelative motion of thewires to the shaving itis small and does notproduce much damage.There were no flashingevents during thesetests.This test is appealingbecause one canvisualize this situation tobe found on an aircraft.The test is alongitudinal typeabrasion test with twopieces square bar stockwith a shallow channelacting as wire holders.The lip of the channelhold the wire in placewith shaving placedbetween the two rows.The amount of damageto the wires dependson how much force isholding the two wireholders together. Aflash event occurredwhen a spring loadedclamp is used.The wire holder supportsthe wire much like alarge bundle would.However the wire holderand clamps used are notfound on aircraft whichmakes the setupundesirable .In this test two row ofwire are wrappedaround a 3" mandrelwith shaving trappedbetween. The top row issqueezed into thenloosened from thebottom row by theoscillating bar.The squeezing didcause damage to theinsulation and in onecase caused a smallflash.Again the wire holderand clamps used are notfound on aircraft whichmakes the setupundesirable .Electrical Arcing of Aged Aircraft Wire.Lectromechanical Design CompanyReport No. N191-RPT4AU99 August 12, 199953