Frequency-domain reflectometry for on-board testing of aging aircraft wiring

Aging aircraft wiring poses a significant safety threat and has been implicated in losses of both military and commercial aircraft. This paper describes the conceptual design and function of a "smart wiring system" based on a low-cost frequency-domain reflectometer (FDR) that can be used to test the integrity of aircraft cables nondestructively on board. This system will enable the pilot or maintainer to test all critical wiring systems prior to flight at the push of a button. The details and test results from the FDR system on realistic aircraft wires are described. The system has a bandwidth of 0.8-1.2 GHz, a range of 4.5 m, and a resolution of 3 cm and can determine the length and terminating impedance of a cable harnesses from measurements at a single end. The system is now being miniaturized to be imbedded in a "connector saver" format for aftermarket installation on common existing platforms.