MIL-HDBK-525

Abstract

<strong>Purpose.</strong> <br>This handbook provides weapons systems program offices a systematic process to assess an aircraft Electrical Wiring Interconnect System (EWIS) for overall condition, service life extension, and continued airworthiness. It aligns with the Mechanical Equipment and Subsystems Integrity Program (MECSIP) (see MIL-STD-1798) and makes extensive use of lessons learned from EWIS-related military, industry, and Federal Aviation Administration (FAA) Advisory Circulars (ACs) concerned with maintaining aircraft airworthiness. It contains a framework to achieve and maintain the physical and functional integrity of the EWIS. This process should be tailored to meet specific platform, program office, system and/or subsystem requirements or constraints. The process and core tasks should also be tailored relative to platform status: whether in design, newly fielded, or based on years in sustainment. A program's use of this process should provide the information necessary to initiate the appropriate trades relative to the cost of modification or integrity initiatives versus required performance, maintenance and mission impact, total operating cost, and aircraft availability. This handbook is for guidance only and cannot be cited as a requirement.<b><u>Intended Use:</u></b> The intent of EWIS design is to build a system with the same longevity as the airframe structure per FAA AC 25.1701 (d) (8) (a). However, the current age of some legacy weapon systems significantly exceed the original service life requirements. Moreover, the calculated longevity of these legacy EWIS systems are not uniform throughout the aircraft, but are averaged. Some EWIS system components have a much shorter lifespan than the average, and some components' lifespan are much longer than average. EWIS exposure to environmental stresses or personnel performing maintenance will limit EWIS life. Alternately, EWIS in areas infrequently accessed by maintenance personnel or in pressurized or protected environments may increase EWIS life. This handbook outlines a process to capture the available data required to establish and execute an effective EWIS Integrity Program and for service life extension. It should be tailored based upon aircraft specific circumstances (such as maintenance data availability, financial constraints, new platform versus legacy, planned service life, current aircraft age, current or expected mission requirements, etc.) Execution of the EWIS program as outlined in this handbook will assist in identification and justification of resources required to maintain EWIS integrity and ultimately aircraft airworthiness. Strategies to develop an EWIS integrity action plan will vary from platform to platform considering aircraft specific circumstances and may include full aircraft rewiring, targeted rewiring, training initiatives, automated wiring test, scheduled inspections, periodic data monitoring, improved chafe protection, and more. These processes may also be modified as required to provide metrics on the effectiveness of the implemented EWIS integrity strategy (e.g., maintenance data trending/analysis, follow-on hazard assessment, etc.). A properlyapplied EWIS Integrity Program will ensure a reliable and airworthy EWIS which will translate into lower aircraft life cycle costs and improved mission availability.<br>