Hello readers! Today, we will present information about the Disadvantages of Kapton Insulated Wire (tap here to read about the Advantages of Kapton insulated wire). After years of use in many different civilian and military platforms including the F-16, UH-60, AH-1, F-15, and F-18, serious safety issues began to appear.
Once the Kapton wire was in service and started to age it was found to have very poor resistance to mechanical wear; mainly abrasion within cable harnesses due to aircraft movement and during normal maintenance. After the wire has been damaged and the brittle Kapton insulation layer is cracked, the wiring was found to be susceptible to three potential problems which appeared to be unique to polyimide (Kapton) insulated wire:
- Hydrolysis – a phenomenon characterized by cracking and breakdown of the insulation material through exposure to moisture; the speed of breakdown depending on both temperature and stress.
- Wet Arc Tracking – occurs when contaminating moisture or aircraft fluids create a short circuit between an exposed conductor and the aircraft structure or an adjacent exposed conductor at a different potential.
- Dry Arc Tracking – occurs in dry conditions when one or more conductors are shorted as a result of abrasion from the aircraft structure, wire to wire abrasion, and installation error or battle damage.
Either form of arc-tracking can create a very dangerous situation for any air vehicle. When arc tracking occurs it can destroy an entire wire bundle, and, since many bundles contain wiring for multiple systems, this can result in serious loss of functionality. In extreme cases, entire aircraft could be lost. It was postulated by some that Swissair Flight 111 (which crashed in September 1998 killing 299 passengers and crew) was a result of an electrical fire caused by Kapton insulated wire.
Unfortunately, there’s no “easy fix” other than wire replacement. In many cases, complete aircraft rewiring is the best solution, especially for older airframes where the rewiring can be accomplished as part of an upgrade and Service Life Extension Program (SLEP).
Fortunately, InterConnect has the solution with one of its various wire replacement programs. For those who need a complete aircraft rewire, take a look at our eBook titled, “Introduction to Aircraft Wiring Harness Diagrams, Engineering Design, and Disconnects”.