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United States Department of Transportation United States Department of Transportation

AC 25-27A - Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using and Enhanced Zonal Analysis Procedure

Document Information

Number
25-27A
Title
Development of Transport Category Airplane Electrical Wiring Interconnection Systems Instructions for Continued Airworthiness Using and Enhanced Zonal Analysis Procedure
Status
Active
Date issued
2010-05-04
Office of Primary Responsibility
ANM-100, Aircraft Certification Service, Transport Airplane Directorate
Description

Airworthiness Program for Airplane Systems/Fuel Tank Safety (EAPAS/FTS)” rule. That rule requires design approval holders (DAHs) and applicants to develop instructions for continued airworthiness (ICA) consisting of maintenance and inspection tasks, intervals, and procedures for the representative airplane’s electrical wiring interconnection systems (EWIS) for each affected type design. The DAH must also review any fuel tank system ICA it has developed in compliance with Special Federal Aviation Regulation No. 88 (SFAR 88) in order to ensure compatibility with the EWIS ICA, including minimizing redundant requirements. The DAH must then submit the EWIS ICA to the Federal Aviation Administration (FAA) oversight office for review and approval.

This AC provides guidance for developing maintenance and inspection instructions for EWIS using an enhanced zonal analysis procedure (EZAP). For the purposes of this AC, the term “maintenance” encompasses both “maintenance” and “preventive maintenance,” as those terms are defined in Title 14, Code of Federal Regulations (14 CFR) 1.1. For airplane models whose maintenance programs already include a zonal inspection program, the logic described here provides guidance on improving those programs. For airplanes without a zonal inspection program, use of this logic will produce zonal inspections for wiring that can be added to the existing maintenance program. This AC contains information that can be used by operators to improve EWIS maintenance practices. It stresses the importance of inspecting EWIS and
promotes a philosophy of “protect and clean as you go” when performing maintenance, repair, or alterations on an airplane.
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