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Conformance with the provisions of this document is intended to provide wiring system safety, performance, reliability, maintainability, service life and life cycle cost equivalent to that achieved when conforming to the provisions of MIL-W When practicable, paragraph numbers of this specification have been arranged to agree with their counterparts in MIL-W It is recommended that this overall set of requirements be used as a part of an aerospace vehicle specification in order to provide an overall set of requirements for wiring system provision.

The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user. SAE invites your written comments and suggestions.

Copyright Society of Automotive Engineers, Inc. All rights reserved. SCOPE: 1. Aerospace vehicles include airplanes, helicopters, lighter-thanair vehicles, and missiles. Although many of the requirements are written as mandatory and shall be considered as such, there is also considerable material which is intended to denote optional, preferential or guidance type requirements. In interpreting the material contained herein, it is intended that the philosophy of the entire document be considered for the wiring of each new type of vehicle.

This philosophy is safety of the personnel, safety of the vehicle, satisfactory performance and reliability of the vehicle and ease of maintenance, and service life all at the least cost to the operator.

The intent of this document will be fulfilled by tailoring the requirements in each new type or class of aerospace vehicle designed, to the proper application. Unless otherwise indicated, copies of federal and military specifications, standards and handbooks are available from the Standardization Documents Order Desk, Bldg.

Unless otherwise specified, the issues of documents not listed in the DODISS are the issues of the documents cited in the solicitation see 6. Industry association specifications and standards are generally available for reference from libraries. They are also distributed among technical groups and using Federal agencies.

Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. CHAFING: Repeated relative motion between wiring system components, or between a wiring system component and structure or equipment, which results in a rubbing action that causes wear which will likely result in mechanical or electrical failure during the aerospace vehicles specified service life.

End faces are either cleaved or cleaved and polished so as to optimize their light transmission characteristics. In signal applications, the transmitter and receiver include devices that are used to convert between optical and electronic pulses. A connector system consists of mated connectors, fully wired, backshells or conduit assemblies, and mounting hardware installed on a structural panel firewall.

The firewall and the attached components or fittings shall withstand flame penetration and shall not exhibit backside ignition for the required test time 15 minutes. These conditions are generally the results of fuel or hydraulic line failures, heat duct failures, or engine case burn through allowing high pressure and high temperature gas to escape from the engine, and similar types of failures.

Some typical fire zones are the engine nacelles, APU compartment, fuel burning heaters, weapon exhaust areas, and other combustion equipment installations. Other areas such as wheel wells, may also be considered a fire zone area due to the heat generated from the brakes. A harness may be an open harness or a protected harness.

Such losses are normally the result of air gaps, misalignment and angularity between termini end faces, cable bends, and the inherent characteristics of cabling materials. The added protection may consist of an overbraid, tape wrap, conduit or some other form of protection.

The various types of termini are designed either to be mechanically crimped or epoxy bonded to a fiber optic cable. When used as a verb it is the act of fabricating and installing these items in the vehicle. A wire segment that has been broken and then repaired is still considered to be one wire segment. All requests for deviations shall include sufficient engineering information to substantiate the deviations. Conflicting requirements: In case of discrepancies between this specification and the type or detail specification for a particular vehicle part, the type or detail specification shall prevail.

Parts and materials shall be procured from QPL sources when they exist. Nonstandard parts and materials must be equivalent to or better than similar standard parts and materials. When this specification fails to provide an applicable specification or standard, the contractor shall use other established specifications or standards in the order of precedence set forth in MIL-STD Parts and materials selected from other than this specification are not standard, and approval must be obtained prior to their use in aerospace vehicles.

Each vendor source for a nonstandard part or material requires approval. When a nonstandard part is used where a suitable standard part exists, the contractor shall reference the standard part on the drawing, parts lists, or data package, and the installation shall provide for replacement with the standard part.

Commercial utility parts: Commercial utility parts, such as screws, bolts, nuts, cotter pins, etc. The contractor shall provide substantiating test data and, when required by the procuring activity, shall provide samples for test.

Commonality: An objective in the selection of parts shall be to maximize commonality and minimize the variety of wiring components and related servicing tools required in the construction, installation and maintenance of the electrical wiring system. Government-furnished Aircraft Equipment GFAE : Wiring and wiring devices furnished by the Government shall be installed without modification unless otherwise authorized or directed by the procuring activity. Modification: The contractor shall not alter, rework or modify wiring or wiring devices built to and meeting Government specifications, unless authorized or directed by the procuring activity, and such modification shall be subject to Government inspection.

Modified parts shall have the Government identifying part number removed and shall be identified by contractor part number. These goals shall be subject to procuring activity approval. Adequate protective means, both physical and electrical, shall be employed to provide reliability and safety commensurate with this requirement. This standard establishes requirements for the selection and protection of dissimilar metal combinations and other significant corrosion behavior factors.

Nonmetals: Nonmetals used, including plastics, fabrics and protective finishes, shall be moisture and flame resistant, shall not support fungus growth, shall not support combustion, and shall not be adversely affected by weathering, applicable fluids and propellants, temperature and ambient conditions encountered during operation of the vehicle.

Materials that give off a minimum amount of noxious gases shall be selected. Nonmetals may be treated to conform to this requirement. Insulating materials: Insulating materials shall have an arc resistance capability which will meet the circuit requirements. Sealing materials: Only materials that are elastomeric and reversion resistant shall be used. Overaged material shall not be used.

The sealing material shall be held in place by suitable forms during the curing process. Epoxy adhesives: Only epoxies that can withstand sustained use without degradation of mechanical and adhesive properties at the maximum ambient temperatures shall be used for the bonding of fiber optics cables to termini.

The time and temperature used for curing of epoxy adhesive used in fiber optics terminations shall be controlled so that a consistent bond is provided under all service conditions.

In addition, selection and installation considerations shall be made relative to vehicle operation and servicing environments to ensure that they are not subjected to conditions exceeding the limits specified in the applicable wiring component specifications. All wiring shall be accessible, repairable and replaceable at the maintenance level specified by the procuring activity.

Other specific requirements concerning maintenance are specified in the appropriate paragraph on the subject. Wiring selection: Wiring shall be of a type suitable for the application.

Wire shall be selected so that the rated maximum conductor temperature is not exceeded for any combination of electrical loading, ambient temperature, and heating effects of bundles, conduit and other enclosures. Typical factors to be considered in the selection are voltage, current, ambient temperature, mechanical strength, abrasion, flexure and pressure altitude requirements, and extreme environments such as Severe Wind and Moisture Problem SWAMP areas or locations susceptible to significant fluid concentrations.

The wire shall be selected in accordance with Appendix A of this specification. The wire selection shall take into account all requirements of this specification and the following design considerations. These effects shall be taken into account in the selection and application of wiring. Tin plated conductors: Tin-copper intermetallics will form resulting in an increase in conductor resistance. The increase is inverse to size, being up to 4 percent for the smallest gage.

Due to potential fire hazard, silver plated conductors shall not be used in areas where they are subject to contamination by ethylene glycol solutions. These conditions should be considered in the application of wiring using these conductors. Solderability: Both tin plated and silver plated copper conductors will exhibit degraded solderability after exposure to continuous elevated temperature. Compensating steps shall be included in maintenance procedures for retermination.

Aluminum wire: The use of aluminum wire requires procuring activity approval. Aluminum wire shall be restricted to size 8 and larger. Aluminum wire shall neither be directly attached to engine mounted accessories nor installed in other areas of severe vibration. It shall not be installed where frequent connections and disconnections are required.

All installations of aluminum wire shall be relatively permanent. Aluminum wire shall not be used where the length of run is less than 3 feet, nor in areas where corrosive fumes exist. Aluminum wire shall be terminated only by terminations specifically approved for this application see 3. Fiber Optics Cable Selection: The type, size, construction and distinct identification for fiber optics cable shall be suitable for the application and shall be approved for use by the procuring activity.

Cable shall be of a construction which provides the required optical performance under all service conditions when the overall characteristics of end face polish, cable length, number of connections, installation bend radii and environmental degradation are taken into account.

Cable shall be resistant to environmental degradation and handling damage and shall be of a continuous temperature rating that is compatible with assembly process and installation environment. Strength member: Fiber optics cable shall include a layer of fiberglass, aramid, or other nonmetallic material that can be mechanically attached to termini assemblies for the purpose of resisting tensile loads. Jacket: External jacket of fiber optics cable shall be resistant to moisture, mechanical damage and temperature degradation.

Coaxial cables: Coaxial cables shall be suitable for the application and shall be selected in accordance with For applications above MHz and in critical RF circuits, critical electrical characteristics such as attenuation, capacitance, structural return loss, environmental requirements, short leads and grounding shall be considered in design.

Coaxial cable operating in the Transverse Electromagnetic Mode TEM and coaxial cable with tubular metal outer surfaces shall be identified by a violet colored marker 1 inch nominal width at intervals not greater than 24 inches of length and within 6 inches of termination.

Open harnesses are preferred for maintenance considerations. Harnesses may be designed to meet mechanical or shielding requirements. The use of protected harnesses shall be avoided unless wiring design considerations dictate their use and is subject to the approval of the procuring activity.

The design details of protected harnesses are also subject to the approval of the procuring activity. Insulation compatibility with sealing and servicing: Wiring terminations in devices where the wiring must be sealed to provide an environment resistant joint, shall have insulation compatible with the sealing feature of the device. Sealing on tape wrapped, braided, striped, or other than smooth circular insulations shall be specifically tested for compatibility and shall be subject to procuring activity approval, unless compatibility has been demonstrated in the qualification of the terminating device.

After installation in the vehicle, the integrity of the sealing features of all such devices shall be intact, and able to perform their function. A device shall be considered as sealed if the outermost sealing feature web is in full contact with the device when visually inspected.

The wiring shall be installed so that transverse loads will not destroy the integrity of the sealing feature of the wire. Wire diameter: The finished wire outside diameter shall be within the limits specified for the grommet specified in the appropriate component specification and shall not exceed the capability of contact servicing tools to insert and release contacts.

Insulation degradation: Wiring shall be handled, stripped and installed so as not to distort, roughen or damage the insulation on which sealing is to be effected.



Conformance with the provisions of this document is intended to provide wiring system safety, performance, reliability, maintainability, service life and life cycle cost equivalent to that achieved when conforming to the provisions of MIL-W When practicable, paragraph numbers of this specification have been arranged to agree with their counterparts in MIL-W It is recommended that this overall set of requirements be used as a part of an aerospace vehicle specification in order to provide an overall set of requirements for wiring system provision. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.


What Is SAE-AS50881 and How Does It Relate To Wiring Harness Design?



SAE AS50881


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