Heavier wire is used for high-demand motors, pumps, and some lighting. This makes it much easier to track down a problem in a thick bundle. Your Maintenance manual will have a list of the wiring codes’ corresponding circuits. OEM wiring is usually coded about every six to twelve inches. Some wires are also reinforced with nylon. Until the early 90’s, wire was insulated with PVC, but it has since been phased out and replaced with Tefzel. The switch is split to separate the two systems.Īircraft wiring usually consists of tin-coated copper-stranded wire covered by insulation. The left side of the master switch provides 5-amp power to energize the alternator. This completes the circuit to the buss (named after the founder of Buss Fuses, years ago) and the airplane is powered up. The right side of the master switch provides the connection to ground that closes the contactors in the solenoid. Located strategically, solenoids can save a lot of wire weight. A solenoid is a switch that’s capable of handling a large amount of power, but may be controlled by a very small amount of power. The negative side (anode) of the battery is connected to the airframe and engine. The positive side of the battery (cathode) is connected directly to the master solenoid and the alternator. Most batteries are lead acid though lithium and nickel cadmium batteries are becoming more popular. The power source in our airplanes is the battery. In this piece, we’ll concentrate on 14-volt systems, though the theory is the same for both. The downside of a 28-volt system is the expense of the battery-which didn’t seem to bother the designers. The 28-volt systems use even lighter wiring and lighting, and appliances are designed differently so nothing is interchangeable. Today’s aircraft have two different systems: 14-volt and 28-volt. In fact, Plane Power (an alternator manufacturer in Texas, builds a 150-amp alternator that weighs less than an old 40-amp generator. They create AC current that is rectified into DC. Alternators were simpler, lighter, cheaper, and much more dependable. At idle or low RPM, demand on the battery could cause it to run out of power. Generators suffered from high weight, unreliability, and their output was directly tied to the RPMs of the engine. Older aircraft were built with generators that produced DC current. The main components of our system are a battery, an alternator or generator, a master solenoid, a master switch, a buss bar, wire, switches and, finally, the appliances. We do this because the wire gauge can be much smaller (for weight and space considerations), the voltage is much lower, thus safer, and because the energy is “quieter.” DC current flows in a straight line and is also called Constant Current, as there are no fluctuations in the current value. ![]() We use DC power in our airplanes (and, for that matter, most other vehicles) as opposed to AC which we use in our houses. ![]() Our electrical systems are pretty simple. We don’t want to teach electrical engineering here, rather create an understanding of the basic system. This discussion will tell you how an aircraft electrical system works, not why. Piece of cake-it called for different skills, but it was cool! But if you have a starter, and if you have a radio, then you will need an electrical system on board. ![]() I once lost an alternator and finished a flight by flying a Grumman Tiger like a Piper Cub for 600 miles. All airplanes have them and they are independent of the electrical system. Some of these systems are easier to understand than others, but one system that has many owners flummoxed is the electrical system. Still, all of us can benefit from fundamental systems knowledge, especially when it comes to telling your mechanic about a problem so that he or she can better understand it and work more efficiently to troubleshoot and repair that problem. While some of us simply enjoy working on our birds as part of the hobby aspect of flying, there are others who don’t necessarily want to get their hands dirty. After all, that’s why we have mechanics, right? As an aircraft owner and writer, I’ve devoted years of work to familiarizing pilots and owners with the basics of how and why our airplanes work. Naturally, we can’t be expected to know everything about our airplanes. Everything You Need to Know about Aircraft Electrical in 1,000 Words (more or less)
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