| ABSTRACT: | NONDESTRUCTIVE EVALUATION OF AIRCRAFT AND SPACECRAFT WIRING
E.J. Tucholski1, and R.E. Green, Jr.2
1U.S. Naval Academy, Annapolis, MD. U.S.A.; 2Johns Hopkins University, Baltimore, MD,U.S.A.
Spacecraft and especially aircraft often fly well past their original design lives and, therefore, the need to
develop nondestructive evaluation procedures for inspection of vital structures in these craft is extremely
important. One of the more recent problems is the degradation of wiring and wiring insulation. The most
common aircraft wire insulation flaws are chafes, cracks, cuts, delaminations, burns and embrittlement. The
factors contributing to the insulation deterioration are mechanical vibrations, mechanical stress, moisture,
elevated temperatures, repeated temperature fluctuations and exposure to chemicals. The principal
technique for inspecting aviation and spacecraft wiring components used to date remains visual inspection.
These inspections are unable to detect all existing flaws and are subject to discrepancies and errors. It is
imperative that an alternative method be developed to reliably detect the status of wiring insulation without
removing it from the airplane or spacecraft. In this paper, three methods are described which have been
assessed to determine their suitability for assessing the status of wiring in situ. A global imaging approach
was used to appraise the condition of as many wires in a bundle as possible at one time. Once this technique
indicated the presence of a possible damage area on a given wire, a higher resolution technique was used to
obtain a permanent image of that local area and an electrical test was conducted to examine the dielectric
characteristics of the insulation. The primary techniques described in this presentation are infrared
thermographic imaging, pulsed x-radiography, and electrical time domain reflectivity.
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