“I can’t figure out why the radio stopped working,” said Bill. The instrument panel was upside down on the top of the cowling.
Cindy looked at the mass of wires and shook her head from side to side as if to loosen stray cobwebs from her face. “That’s a rat’s nest.”
“Hey! Be careful with the praise. I’m no electrician. Everything was working. I only have 20 hours on the airplane.”
“Did anything strange precede the failure?”
“Yes. A hard landing.”
“Then I know what it is.” Cindy pulled her glasses out of her shirt pocket. She examined the wiring leaving the back of the panel. “Here it is.” She pointed to a bus bar with a disconnected wire. “You used fork terminals here; you should have used ring terminals. None of these are tight.”
It was time for Bill to shake his head in dismay. “OK. I’ll get on it.”
“Be glad it wasn’t worse than just losing radio power. I recommend tracing and labeling these wires and lacing them up so vibration doesn’t cause problems.”
What does the wiring in your project look like? Since you are reading this magazine, it probably looks excellent. Everything is labeled, wires are Tefzel or Teflon, you have bundled the wires neatly and used wire ties or lacing to secure them.
In my work as a technical counselor, I see all manner of strange things on airplane projects. The electrical systems contain an assortment of automotive wiring, multiple power and ground blocks, a mix of fuses, a lack of labels and plastic hobby-type terminals. If one ground wire is good, lots of them are better.
Don’t misunderstand; 80% of the projects I visit have very good workmanship. But the rest need help. It’s not deliberate, either; it’s simply a lack of understanding around what the standards are and not taking the time to study the directions. Here are a few tips for electrical systems.
Wiring Tips
• Read the manufacturer’s directions and do what they recommend.
• Take a class—ideally a hands-on workshop—or online self-study seminar on electrical systems for aircraft. Watch the EAA videos.
• Have a couple of the classic texts at hand—AC-43.13: Acceptable Methods, Techniques, and Practices and AeroElectric Connection by Bob Nuckolls. Look through the EAA and Amazon book listings on aircraft electrical and electronic systems. To get started, read Best Practices—Electrical in the July, August and September 2017 issues of KITPLANES by Dave Prizio.
• Simplify. Find out from the kit manufacturer if you can use a “hotbox” on your electric start ultralight, or a PPS, or primary power system, on your Experimental homebuilt. A PPS is a solid-state electrical system designed for Experimental aircraft that combines circuit protection and some major components in one box.
• Fully label circuits. Masking tape is fine until you get to the end. Then make readable labels. You can find an assortment of products online.
• Work with an A&P for a day when they are assembling or repairing wiring systems.
• Don’t hide fuses. Think about the ease of troubleshooting and the necessity of replacing a fuse in flight. One project I saw had the fuse panel under the passenger seat. Not all setups have circuit breakers on the panel.
• Organize your electrical and electronic diagrams in your build binder where you can find them easily. If you go to the trouble of organizing a pilot handbook for the airplane, this information is great to have there too.
No more rats.
