Because the voltage is higher than that normally used in airplanes, the electrical pulse will jump like a rabbit from the smallest wiring insulation fault (which to ordinary instrumentation seems undamaged) either to the bulkhead or to another nearby damaged wire. That spark — like static electricity leaping from hand to doorknob — in effect lights up the invisibly damaged spot like a tracer bullet lights up a night target. The amount of time it takes for the current to return to its source is analyzed by the automated test-set to tell within inches how far the break is from the test entry point.
The device, about the size of a small suitcase, can be plugged into aircraft-installed wire harnesses, 40 wires at a time, to check for the very small insulation breaks associated with intermittent faults.
“Rather than reacting to a problem, these systems can find a fault before it manifests into a catastrophic event,” says Sandia team leader Larry Schneider. “Rather than ripping apart the fuselage for access to a faulty harness that may run the length of the plane, airline mechanics will be able to use this new tool to efficiently locate and repair the intermittent fault.”