CS 25.1701 Definition

1 Paragraph CS 25.1701 defines EWIS for the purposes of complying with the subpart H requirements and other EWIS-related requirements of CS 25. CS 25.1701 clearly identifies which wires and components these requirements apply to. Although this definition is located in subpart H to CS 25, it applies to all EWIS requirements regardless of location within CS 25. 2 Subparagraph CS 25.1701(a) defines EWIS as any wire, wiring device, or combination of these, including termination devices, installed in any area of the aeroplane for the purpose of transmitting electrical energy, including data and signals between two or more intended termination points. The term “wire” means bare or insulated wire used for the purpose of electrical energy transmission, grounding, or bonding. This includes electrical cables, coaxial cables, ribbon cables, power feeders, and data busses. 3 Subparagraph CS 25.1701(a) of the requirement provides a listing of the component types that are considered part of the EWIS. These component types are listed as items CS 25.1701(a)(1) through CS 25.1701(a)(13). While these are the most widely used EWIS components it is not an all inclusive list. There may be components used by an applicant to support transmission of electrical energy that are not listed but meet the EWIS definition. They will be EWIS components subject to EWIS related regulatory requirements. 4 CS 25.1701(b) says that EWIS components located inside shelves, panels, racks, junction boxes, distribution panels, and back-planes of equipment racks (e.g., circuit board back-planes, wire integration units, external wiring of equipment) are covered by the EWIS definition. These components are included in the EWIS definition because the equipment they are inside of or part of, is typically designed and made for a particular aeroplane model or series of models. So the requirements that apply to aeroplane EWIS components must be applied to the components inside that equipment. These contrast with avionics components that must be sent back to their manufacturer or a specialized repair shop for service. Components inside shelves, panels, racks, junction boxes, distribution panels, and back-planes of equipment racks are maintained, repaired, and modified by the same personnel who maintain, repair, and modify the EWIS in the rest of the aeroplane. For example, in an electrical distribution panel system separation must be designed and maintained within the panel just like the EWIS leading up to that panel. Identification of components inside the panel is just as important as outside the panel since the wiring inside the panel is treated much the same. Also, while this type of equipment is designed for its intended function and is manufactured and installed to the same standards as other EWIS, it is typically not qualified to an environmental standard such as EUROCAE ED-14 / RTCA DO-160. 5 There are some exceptions to the EWIS definitions and those are given in CS 25.1701(c). Paragraph excepts EWIS components inside the following equipment, and the external connectors that are part of that equipment:

5.1 Electrical equipment or avionics that is qualified to environmental conditions and testing procedures when those conditions and procedures are appropriate for the intended function and operating environment, and acceptable to the Agency.

5.2 Portable electrical devices that are not part of the type design of the aeroplane including personal entertainment devices and laptop computers.

5.3 Fibre optics. 6 The first exception means EWIS components located inside avionic or electrical equipment such as flight management system computers, flight data recorders, VHF radios, primary flight displays, navigation displays, generator control units, integrated drive generators, and galley ovens, if this equipment has been tested to industry-accepted environmental testing standards. Examples of acceptable standards are EUROCAE ED-14 / RTCA DO-160, and equipment qualified to a European Technical Standard Order (ETSO) 7 An applicant may use any environmental testing standard if the applicant can demonstrate that the testing methods and pass/fail criteria are at least equivalent to the widely accepted standards of EUROCAE ED-14 / RTCA DO-160, or a specific ETSO. Applicants should submit details of the environmental testing standards and results of the testing that demonstrate the equipment is suited for use in the environment in which it will be operated.

[Amdt 25/5]