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.
Technical detail
Wet arc-tracking is distinct from dry arcing in propagation rate and damage radius. Aged Kapton constructions are particularly susceptible. Mean propagation rate, propagation duration, and reach into adjacent bundles are the design-driving outputs of a wet arc-track test.
Lectromec wet arc-track propagation testing is one of the substantiation methods used for compliance arguments under §25.1707(a) and (c).
When it matters
Any cert work on a Kapton or mixed-insulation airframe, particularly under aged-wire reassessment programs.
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.
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.
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.