What type of wiring method is most often employed in metal aircraft electrical and electronic systems?

• A. Single wire method (negative ground)
• B. Dual conductor with shield
• C. Multi-conductor with shielded jacket
• D. Fiber optic wiring

Answer: (A)

The wiring approach most commonly used on metal aircraft is a single hot conductor with the airframe serving as the return path, known as a negative-ground system. In this setup, the electrical current travels from the power source to a device along one conductor, and the device’s return is completed through the metal airframe back to the source. Using the structure as the return path keeps wiring simple and lightweight, which is a big win in aviation where weight matters, and it provides a common ground reference for the system.

Shielded or multi-conductor cables (with shields or jackets) are used when EMI sensitivity or noise is a concern, but they add weight and complexity and aren’t the default approach for the general electrical/electronic network in a metal airframe. Fiber optic wiring is great for data and EMI immunity, but it isn’t carrying electrical power like the single-wire negative-ground method, so it isn’t the typical method for the overall electrical system.