New and revised certification specifications were introduced through CS-25 “Certification Specifications for Large Aeroplane” amendment 5 with a new Subpart H – Electrical Wiring Interconnection Systems – EWIS. The new amendment has been published as part of the ED Decision No. 2008/006/R on the 29th August 2008 and enters into force on September 5th, 2008.
The requirement for existing TC holders to develop EWIS Instructions for Continued Airworthiness (ICA) derived from the Enhanced Zonal Analysis Procedure (EZAP) is imposed through the provisions of Part 21A.3B(c)1 for existing TCs, 21A.21(c)(3) for applicants for TC and 21A.103(a)(2)(iii) for applicants for changes to TC. TC holders have been notified of the applicability of those provisions through a dedicated letter that was sent in October 2008. This letter gives further details on the affected aeroplanes (see Question "The letter dated 07.01.2009 (the letter sent by DOA Section) specifies certain aircraft class in the footer. Where can we find this specified in a current regulation?"), deliverables and compliance dates.
Note: The Agency has used this letter in the absence of a regulatory tool similar to FAR Part 26.