Heavy Current Cable

Per FAA 25.1707(c), a wire or cable of 16 AWG or larger, or any conductor whose arcing failure could cause significant damage to nearby systems. Heavy current cables and their associated EWIS components must be physically separated and electrically isolated under fault conditions.

Technical detail

The 16 AWG floor captures most power feeders. The 'significant damage on arcing failure' clause extends the definition upward in energy: a smaller conductor on a high-energy bus, or a conductor whose fault current can sustain an arc, can also be classified as a heavy current cable for §25.1707(c) purposes.

Compliance can be shown for the particular case — the specific installation as designed — or for the general case, which produces a broader recommendation but typically forces larger keep-out distances than any single installation requires.

When it matters

Power-feeder layouts, generator-tie routing, and battery-bus installations all require explicit heavy-current-cable assessment under §25.1707(c).

Related terms

FAA 25.1707 — System Separation Requirements
The Federal Aviation Regulation that requires EWIS to be physically separated and electrically isolated from other EWIS, aircraft systems, fluid lines, control cables, and heated equipment such that no credible failure can produce a hazardous condition.
Wet Arc Track Propagation
A failure mode in which a contaminating fluid lowers the surface dielectric strength of wire insulation, allowing an arc to track along the insulation and propagate from a single initial breach to multiple adjacent conductors.
Arc Damage Modeling Tool
Lectromec's arc damage simulation tool. Simulates wire failures that produce arcing events and the subsequent damage to nearby harnesses, structure, and fuel or hydraulic lines. Used in certification packages for aerospace organizations.