Electrical Wiring Interconnection System
Every wire, wiring device, and combination thereof installed in any area of an aircraft for transmission of electrical energy between two or more termination points, including supporting components such as clamps, connectors, and bundle hardware.
Technical detail
EWIS is defined in 14 CFR §25.1701 and covers conductors, splices, terminations, connectors, clamps, conduits, sleeves, ties, supports, and any ancillary hardware whose failure could affect the electrical performance of the wire system.
The EWIS construct treats the wire system as an integrated system rather than a collection of individual components. That framing is what enables the §25.1700 series — including §25.1703 design, §25.1707 separation, §25.1711 protective features, and §25.1717 maintainability — to apply consistent installation, test, and continued-airworthiness requirements across all wire-system hardware.
Any certification submission for a transport-category aircraft or a major modification under an STC touches EWIS. Treating the wire system as 'just wiring' rather than as an EWIS in scope of §25.1700 is one of the most common ways a cert basis gets reopened.