Title 14—Aeronautics and Space--Volume 1
PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
§ 25.1701   Definition.
(a) As used in this chapter, electrical wiring interconnection system (EWIS) means any wire, wiring device, or combination of these, including termination devices, installed in any area of the airplane for the purpose of transmitting electrical energy, including data and signals, between two or more intended termination points. This includes:
(1) Wires and cables.
(2) Bus bars.
(3) The termination point on electrical devices, including those on relays, interrupters, switches, contactors, terminal blocks and circuit breakers, and other circuit protection devices.
(4) Connectors, including feed-through connectors.
(5) Connector accessories.
(6) Electrical grounding and bonding devices and their associated connections.
(7) Electrical splices.
(8) Materials used to provide additional protection for wires, including wire insulation, wire sleeving, and conduits that have electrical termination for the purpose of bonding.
(9) Shields or braids.
(10) Clamps and other devices used to route and support the wire bundle.
(11) Cable tie devices.
(12) Labels or other means of identification.
(13) Pressure seals.
(14) EWIS components inside shelves, panels, racks, junction boxes, distribution panels, and back-planes of equipment racks, including, but not limited to, circuit board back-planes, wire integration units, and external wiring of equipment.
(b) Except for the equipment indicated in paragraph (a)(14) of this section, EWIS components inside the following equipment, and the external connectors that are part of that equipment, are excluded from the definition in paragraph (a) of this section:
(1) Electrical equipment or avionics that are qualified to environmental conditions and testing procedures when those conditions and procedures are—
(i) Appropriate for the intended function and operating environment, and
(ii) Acceptable to the FAA.
(2) Portable electrical devices that are not part of the type design of the airplane. This includes personal entertainment devices and laptop computers.
(3) Fiber optics.
§ 25.1703   Function and installation: EWIS.
(a) Each EWIS component installed in any area of the aircraft must:
(1) Be of a kind and design appropriate to its intended function.
(2) Be installed according to limitations specified for the EWIS components.
(3) Perform the function for which it was intended without degrading the airworthiness of the airplane.
(4) Be designed and installed in a way that will minimize mechanical strain.
(b) Selection of wires must take into account known characteristics of the wire in relation to each installation and application to minimize the risk of wire damage, including any arc tracking phenomena.
(c) The design and installation of the main power cables (including generator cables) in the fuselage must allow for a reasonable degree of deformation and stretching without failure.
(d) EWIS components located in areas of known moisture accumulation must be protected to minimize any hazardous effects due to moisture.
§ 25.1705   Systems and functions: EWIS.
(a) EWIS associated with any system required for type certification or by operating rules must be considered an integral part of that system and must be considered in showing compliance with the applicable requirements for that system.
(b) For systems to which the following rules apply, the components of EWIS associated with those systems must be considered an integral part of that system or systems and must be considered in showing compliance with the applicable requirements for that system.
(1) § 25.773(b)(2) Pilot compartment view.
(2) § 25.981 Fuel tank ignition prevention.
(3) § 25.1165 Engine ignition systems.
(4) § 25.1310 Power source capacity and distribution.
(5) § 25.1316 System lightning protection.
(6) § 25.1331(a)(2) Instruments using a power supply.
(7) § 25.1351 General.
(8) § 25.1355 Distribution system.
(9) § 25.1360 Precautions against injury.
(10) § 25.1362 Electrical supplies for emergency conditions.
(11) § 25.1365 Electrical appliances, motors, and transformers.
(12) § 25.1431(c) and (d) Electronic equipment.
§ 25.1707   System separation: EWIS.
(a) Each EWIS must be designed and installed with adequate physical separation from other EWIS and airplane systems so that an EWIS component failure will not create a hazardous condition. Unless otherwise stated, for the purposes of this section, adequate physical separation must be achieved by separation distance or by a barrier that provides protection equivalent to that separation distance.
(b) Each EWIS must be designed and installed so that any electrical interference likely to be present in the airplane will not result in hazardous effects upon the airplane or its systems.
(c) Wires and cables carrying heavy current, and their associated EWIS components, must be designed and installed to ensure adequate physical separation and electrical isolation so that damage to circuits associated with essential functions will be minimized under fault conditions.
(d) Each EWIS associated with independent airplane power sources or power sources connected in combination must be designed and installed to ensure adequate physical separation and electrical isolation so that a fault in any one airplane power source EWIS will not adversely affect any other independent power sources. In addition:
(1) Airplane independent electrical power sources must not share a common ground terminating location.
(2) Airplane system static grounds must not share a common ground terminating location with any of the airplane's independent electrical power sources.
(e) Except to the extent necessary to provide electrical connection to the fuel systems components, the EWIS must be designed and installed with adequate physical separation from fuel lines and other fuel system components, so that:
(1) An EWIS component failure will not create a hazardous condition.
(2) Any fuel leakage onto EWIS components will not create a hazardous condition.
(f) Except to the extent necessary to provide electrical connection to the hydraulic systems components, EWIS must be designed and installed with adequate physical separation from hydraulic lines and other hydraulic system components, so that:
(1) An EWIS component failure will not create a hazardous condition.
(2) Any hydraulic fluid leakage onto EWIS components will not create a hazardous condition.
(g) Except to the extent necessary to provide electrical connection to the oxygen systems components, EWIS must be designed and installed with adequate physical separation from oxygen lines and other oxygen system components, so that an EWIS component failure will not create a hazardous condition.
(h) Except to the extent necessary to provide electrical connection to the water/waste systems components, EWIS must be designed and installed with adequate physical separation from water/waste lines and other water/waste system components, so that:
(1) An EWIS component failure will not create a hazardous condition.
(2) Any water/waste leakage onto EWIS components will not create a hazardous condition.
(i) EWIS must be designed and installed with adequate physical separation between the EWIS and flight or other mechanical control systems cables and associated system components, so that:
(1) Chafing, jamming, or other interference are prevented.
(2) An EWIS component failure will not create a hazardous condition.
(3) Failure of any flight or other mechanical control systems cables or systems components will not damage the EWIS and create a hazardous condition.
(j) EWIS must be designed and installed with adequate physical separation between the EWIS components and heated equipment, hot air ducts, and lines, so that:
(1) An EWIS component failure will not create a hazardous condition.
(2) Any hot air leakage or heat generated onto EWIS components will not create a hazardous condition.
(k) For systems for which redundancy is required, by certification rules, by operating rules, or as a result of the assessment required by § 25.1709, EWIS components associated with those systems must be designed and installed with adequate physical separation.
(l) Each EWIS must be designed and installed so there is adequate physical separation between it and other aircraft components and aircraft structure, and so that the EWIS is protected from sharp edges and corners, to minimize potential for abrasion/chafing, vibration damage, and other types of mechanical damage.
§ 25.1709   System safety: EWIS.
Each EWIS must be designed and installed so that:
(a) Each catastrophic failure condition—
(1) Is extremely improbable; and
(2) Does not result from a single failure.
(b) Each hazardous failure condition is extremely remote.
§ 25.1711   Component identification: EWIS.
(a) EWIS components must be labeled or otherwise identified using a consistent method that facilitates identification of the EWIS component, its function, and its design limitations, if any.
(b) For systems for which redundancy is required, by certification rules, by operating rules, or as a result of the assessment required by § 25.1709, EWIS components associated with those systems must be specifically identified with component part number, function, and separation requirement for bundles.
(1) The identification must be placed along the wire, cable, or wire bundle at appropriate intervals and in areas of the airplane where it is readily visible to maintenance, repair, or alteration personnel.
(2) If an EWIS component cannot be marked physically, then other means of identification must be provided.
(c) The identifying markings required by paragraphs (a) and (b) of this section must remain legible throughout the expected service life of the EWIS component.
(d) The means used for identifying each EWIS component as required by this section must not have an adverse effect on the performance of that component throughout its expected service life.
(e) Identification for EWIS modifications to the type design must be consistent with the identification scheme of the original type design.
§ 25.1713   Fire protection: EWIS.
(a) All EWIS components must meet the applicable fire and smoke protection requirements of § 25.831(c) of this part.
(b) EWIS components that are located in designated fire zones and are used during emergency procedures must be fire resistant.
(c) Insulation on electrical wire and electrical cable, and materials used to provide additional protection for the wire and cable, installed in any area of the airplane, must be self-extinguishing when tested in accordance with the applicable portions of Appendix F, part I, of 14 CFR part 25.
§ 25.1715   Electrical bonding and protection against static electricity: EWIS.
(a) EWIS components used for electrical bonding and protection against static electricity must meet the requirements of § 25.899.
(b) On airplanes having grounded electrical systems, electrical bonding provided by EWIS components must provide an electrical return path capable of carrying both normal and fault currents without creating a shock hazard or damage to the EWIS components, other airplane system components, or airplane structure.
§ 25.1717   Circuit protective devices: EWIS.
Electrical wires and cables must be designed and installed so they are compatible with the circuit protection devices required by § 25.1357, so that a fire or smoke hazard cannot be created under temporary or continuous fault conditions.
§ 25.1719   Accessibility provisions: EWIS.
Access must be provided to allow inspection and replacement of any EWIS component as necessary for continued airworthiness.
§ 25.1721   Protection of EWIS.
(a) No cargo or baggage compartment may contain any EWIS whose damage or failure may affect safe operation, unless the EWIS is protected so that:
(1) It cannot be damaged by movement of cargo or baggage in the compartment.
(2) Its breakage or failure will not create a fire hazard.
(b) EWIS must be designed and installed to minimize damage and risk of damage to EWIS by movement of people in the airplane during all phases of flight, maintenance, and servicing.
(c) EWIS must be designed and installed to minimize damage and risk of damage to EWIS by items carried onto the aircraft by passengers or cabin crew.
§ 25.1723   Flammable fluid fire protection: EWIS.
EWIS components located in each area where flammable fluid or vapors might escape by leakage of a fluid system must be considered a potential ignition source and must meet the requirements of § 25.863.
§ 25.1725   Powerplants: EWIS.
(a) EWIS associated with any powerplant must be designed and installed so that the failure of an EWIS component will not prevent the continued safe operation of the remaining powerplants or require immediate action by any crewmember for continued safe operation, in accordance with the requirements of § 25.903(b).
(b) Design precautions must be taken to minimize hazards to the airplane due to EWIS damage in the event of a powerplant rotor failure or a fire originating within the powerplant that burns through the powerplant case, in accordance with the requirements of § 25.903(d)(1).
§ 25.1727   Flammable fluid shutoff means: EWIS.
EWIS associated with each flammable fluid shutoff means and control must be fireproof or must be located and protected so that any fire in a fire zone will not affect operation of the flammable fluid shutoff means, in accordance with the requirements of § 25.1189.
§ 25.1729   Instructions for Continued Airworthiness: EWIS.
The applicant must prepare Instructions for Continued Airworthiness applicable to EWIS in accordance with Appendix H sections H25.4 and H25.5 to this part that are approved by the FAA.
§ 25.1731   Powerplant and APU fire detector system: EWIS.
(a) EWIS that are part of each fire or overheat detector system in a fire zone must be fire-resistant.
(b) No EWIS component of any fire or overheat detector system for any fire zone may pass through another fire zone, unless:
(1) It is protected against the possibility of false warnings resulting from fires in zones through which it passes; or
(2) Each zone involved is simultaneously protected by the same detector and extinguishing system.
(c) EWIS that are part of each fire or overheat detector system in a fire zone must meet the requirements of § 25.1203.
§ 25.1733   Fire detector systems, general: EWIS.
EWIS associated with any installed fire protection system, including those required by §§ 25.854 and 25.858, must be considered an integral part of the system in showing compliance with the applicable requirements for that system.
§ 25.1801   SFAR No. 111—Lavatory Oxygen Systems.
The requirements of § 121.1500 of this chapter also apply to this part.