Characteristics of Aircraft Wiring

Aircraft wiring systems play a vital role in adequately operating electrical equipment. Therefore, qualified technicians must install, inspect and maintain them carefully.

Wires carry significant loads and are subject to a combination of vibration, moisture, heat, and physical installation stresses, which can result in deterioration and failure. In addition, it is often a precursor to arc tracking and subsequent fires.

These wires are customized high-strength wire ropes designed to endure the extreme climatic conditions prevalent aboard an airplane, such as high temperatures and dampness. Aviation cable, commonly known as galvanized wire rope, typically comprises carbon steel drawn galvanized.

Insulation

The insulation characteristics of aircraft wiring are critical to the electrical system’s safety. They include dielectric strength, charging current, arc resistance, and tracking susceptibility.

Insulation rapidly deteriorates when it is subjected to high temperatures and mechanical stress. As a result, it leads to reduced insulation performance and can affect the safety of the wires.

Aromatic polyimide insulation is another common choice for aviation wires. Unfortunately, it possesses serious arcing and surface-tracking issues that can lead to catastrophic failures.

Conductor Materials

Conductor materials have a variety of characteristics that affect their ability to transport electricity. These include conductivity (how easily electrons pass through the fabric) and resistance (how easily the electrons are repelled).

Metals like copper or aluminum are common conductors, though other materials may be used in specific applications. Silver, for example, is often plated on copper wires and is also a good conductor, although it can be costly.

Steel is another conductor material but is less commonly used than copper or aluminum. It is because it needs to move electricity more effectively.

In aircraft, wiring insulation is generally synthetic and polymeric. The term “polymer” includes many organic materials, from natural materials such as wool to very complex synthetic materials such as silicone.

Installation

Every airplane has a complicated network of electrical wiring that keeps it flying smoothly. One mile of cable is expected for every four passengers in a modern aircraft. It implies the average passenger airliner has 100 to 200 miles of wire running through it.

Aircraft wiring must be selected to meet the environmental conditions associated with its application. These include moisture, heat, and physical installation stresses (vibration and flexing).

Wires must also be routed away from high-temperature equipment or lines to prevent insulation deterioration. Additionally, they must be rated to withstand the current-related conductor temperature rise and residual heating effects that occur when aircraft are parked for extended periods.

Unique wire products are fabricated to meet these requirements. 

Temperature Rating

Characteristics of aircraft wiring include its voltage rating and maximum conductor surface temperature. It also must withstand moisture, sunlight, and oil – all of which can cause wires to deteriorate.

Temperature ratings are based on the thermal aging characteristics of the polymers used in the insulation and jacket. Generally, the higher the temperature, the shorter the cable’s life.

A wire or cable’s temperature rating should equal the maximum current it can carry without exceeding its operating temperature. Derating is necessary when multiple conductors carrying full-load power are installed in an installation that may be wet or oily. These conditions can increase the heat generated by the wires’ metallic resistance.