In brief – to ensure the airworthiness of the aircraft. Any modern aircraft, especially fighters like the F-15, F-16, F-22 and F-35 have thousands of wires. The integrity of the electrical wiring interconnect system (EWIS) affects the ability to gather data, communicate, fire weapons and even control the aircraft in flight.
Now imagine you’re a technician manufacturing, testing, modifying or repairing part of the electrical system. Being able to identify exactly what wires you need to work on is critical to performing your job and keeping the electrical system in the correct configuration. The way this is accomplished is by giving every wire in the aircraft a unique identifier in the engineering data, maintenance manuals and on each wire itself. Typically the aircraft manufacturer assigns wire numbers to each wire segment during the design of the wiring system. There are variations between manufacturers but most rely on a system similar to that found in AS50881 where the wire ID is composed of several codes that help identify its function. The ID is then applied to the wire itself during wire harness manufacturing. Laser marking the ID is preferable wherever possible. In cases where the wire cannot be laser marked, identification markers are most frequently made from Mil-Spec shrink tubing with a thermal-printed ID.