FAA Advisory Circular 25.1701-1

The FAA Advisory Circular that provides guidance on compliance with the §25.1700 EWIS regulations, including the scope of EWIS, the EMI sources to assess, and the definition of 'independent airplane power source'.

Technical detail

AC 25.1701-1 is the primary guidance document referenced by §25.1707. It enumerates the EMI sources to consider under §25.1707(b): bus-bar noise, cable cross-talk, cable-to-aerial coupling, equipment operating out of spec, parasitic eddy currents and voltages, lightning, static discharge, and dissimilar generator frequencies.

It also defines 'independent airplane power source' as covering the engines, the APU-driven generators, and the batteries — the boundary used to apply §25.1707(d) ground separation requirements.

When it matters

Whenever a cert plan claims compliance with §25.1707, the AC is the document inspectors expect to see referenced for the underlying interpretive guidance.

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.
FAA 25.1701 — EWIS Definition and Scope
The Federal Aviation Regulation that defines what an Electrical Wiring Interconnection System is and identifies the components in scope of the §25.1700 series.