A Standardized Procedure for Evaluating the Relative Thermal Life and Temperature Rating of Thin-Wall Airframe Wire Insulation

The need for a standard procedure for evaluating the relative thermal life and temperature rating of new thin-wall general-purpose aircraft wire insulation is presented from the point of view of the aircraft manufacturer. Problems relative to safety considerations, cost, expected life, temperature rating, and the confusion resulting from the lack of standard test procedures are presented and discussed. A simple specific procedure utilizing the Arrhenius plot is demonstrated and is proposed as a basis for an IEEE Standard for determining the relative thermal life and temperature rating of aerospace wire insulation. Test data on life curves and thermal ratings are presented on six types of wire insulation of present interest in the aircraft industry. These results illustrate the ease of directly comparing the thermal life of various new thin-wall insulation systems relative to the older insulation systems of known service characteristics. Included in the paper are three irradiated insulation systems as well as various insulations that utilize polyimide polymers.