Electrical wiring interconnection systems (EWIS) maintenance program

This regulation requires Part 121 air carriers operating larger transport category turbine airplanes (generally those with 30+ passenger seats or 7,500+ pounds payload capacity, type certificated after January 1, 1958) to include specific electrical wiring interconnection systems (EWIS) maintenance in their programs.

Since March 10, 2011, operators must incorporate FAA-approved inspections and procedures for EWIS based on the manufacturer's Instructions for Continued Airworthiness. This covers the airplane's original certification and any supplemental type certificates. When alterations are made that affect EWIS, operators must add the related maintenance procedures before returning the aircraft to service.

All EWIS program changes require Principal Inspector review and approval.

The regulation recognizes that aging aircraft wiring poses safety risks, so it mandates systematic inspection and maintenance of these critical electrical systems. Thirteen older airplane models are specifically exempted, including the Lockheed L-188, Concorde, and BAC 1-11.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*