How's Your Wiring?

By H. Dean Chamberlain
Reprinted with permission of FAA Aviation News

If your neighbor walked up to you and asked, 'How's your wiring?' You might begin to wonder about your neighbor's sanity. However, if your aircraft's mechanic asked the same question, you might want to stop and answer the question.

No, this writer has not lost his mind (although some question if he ever had one) but all joking aside, this is an important safety issue for both general aviation (GA) and air transport category aircraft. After reviewing comments about two transport category aircraft accidents, TWA Flight 800 on July 17, 1996, and Swiss Air Flight 111 which crashed off Nova Scotia on September 2, 1998, and then completing the FAA's Aircraft Certification Services online Aircraft Wiring Practices (Job Aid), this writer believes owners of GA aircraft need to be aware of the issues surrounding both of these accidents and the potential problems that have been identified as a result of the accidents that are applicable to general aviation aircraft.

The TWA aircraft broke up in flight after an explosion believed caused by the center wing fuel tank. The aircraft had just taken off from New York's JFK Airport en route to Europe. The electrical wiring in the fuel tank is believed to have been the ignition source for the explosion. In the case of the Swiss Air flight, smoke in the cockpit and fire damage in the overhead cockpit and overhead first class area is believed to have been caused by an electrical fire.

These accidents caused FAA to take action involving both fuel tank design and the types of insulation used in aircraft.

If you think these problems are limited to aging transport category aircraft, you need to remember the average age of the general aviation fleet is approaching 30 years of age. My own aircraft that is being upgraded with new wiring was made in 1953. It is old enough to be a baby boomer. It was time to replace the old wiring as it was undergoing a major equipment upgrade. Some of the removed wiring was original dating back to 1953. The question is how old is the wiring in your aircraft?

At your next annual inspection, you might to ask your mechanic to give you a report about your aircraft's wiring condition. Although I happen to like reading FAA Advisory Circular (AC) 43.13-1B, I realize not everyone has read the book or wants to read the manual. For those who have never seen a copy, the AC explains the FAA's recognized methods of working on aircraft. The value of the AC is it provides the non-technical aircraft owner the opportunity to review what are acceptable aircraft maintenance techniques.

For those who have no interest in reading a detailed maintenance technique manual, enter the 164 slide PowerPoint' presentation titled FAA Aircraft Certification's Aircraft Wiring Practices (Job Aid). The job aid was designed for FAA engineers and aviation safety inspectors.

According to the site, the job aid covers applicable 14 Code of Federal Regulations, policy, industry wiring practices, primary factors associated with wire degradation, information on type certificate/supplemental type certificate data package requirements, wire selection and protection, splicing and termination practices, wiring maintenance concepts, including how to perform a wiring general visual inspection, and the job aid includes numerous actual aircraft wiring photos and examples.

Briefing notes are included to help explain the slides. The briefing notes are designed to help someone give the slide presentation to a group of people. They also help explain the slides for those who may not be subject matter experts in wiring practices.

I think the job aid is a good overview of FAA recognized wiring practices that can benefit the typical GA aircraft owner. Since the slide show contains examples of recognized good and bad wiring practices, they provide the non-technical aircraft owner or pilot a means to recognize potentially unsafe wiring in an aircraft.

Are we trying to make a non-qualified person an electrical expert in 164 slides? No. Can the 164 slides help a non-expert identify a possible wiring problem? FAA Aviation News thinks so.

Looking at my own aircraft and looking at similarly aged aircraft, the title of one of my favorite movies comes to mind, 'The Good, The Bad, and The Ugly.' As various modifications have been made to many GA aircraft over the years, I think it is safe to say some of the work has been good; some has been bad, and some is simply ugly. I also think it is safe to say the more complex the aircraft and its systems and its electrical and electronic installation and components, and the more complex its wiring; the uglier the wiring situation may become as the aircraft ages.

If you doubt this observation, when was the last time you looked behind your instrument panel or behind the bulkhead panels hiding your aircraft's wiring? You might be surprised at what you may find. Does the wiring meet the guidelines outlined in the slide show?

To avoid being surprised, you just might want to review the Aircraft Wiring Practices (Job Aid) and then inspect your aircraft. Or you might want to wait until your next annual inspection or whenever your aircraft is scheduled for maintenance and ask your mechanic to review your aircraft's wiring with you. After all, you will have reviewed the recommended ways to secure wiring through bulkheads, seen the proper way to secure wiring in clamps, read how to recognized hot or burnt wiring, and reviewed the proper way to check terminal blocks and other FAA recommended safe wiring practices. You might even impress your mechanic with your newfound knowledge. Just remember that a little knowledge can be dangerous. So before you decide to rewire your entire aircraft next weekend by cutting and slicing your way through its ugly wiring, you might want to ask your mechanic for his or her advice before you start. However, a wiring upgrade may be something to add to your next maintenance check.