Over the past two and one-half decades several metal clad fibers and fabrics have been developed to provide aerospace vehicle designers with a conductive, lighter weight alternative to coated copper, coated stainless steel and steel wire used for cable and wire shielding and harness overbraids on electrical cables. Several of these candidates have been unable to provide the strength or thermal stability necessary for the aerospace environment. However, several polymer-based products have shown remarkable resistance to the rigorous environment of aerospace vehicles. Concurrent with these fiber developments, there have been changes in the structures of aerospace vehicles involving greater use of nonmetallic outer surfaces. This has resulted in a need for increased shielding of electrical cables which adds substantial weight to the vehicle. Thus, a lighter weight shielding material has become more critical to meet the performance requirements of the vehicle.
This specification establishes the requirements for various types and colors of electrical insulating sleeving that will shrink to a predetermined size upon the application of heat. This specification includes provisions for demonstrating compliance with qualification requirements (see Section 4 and 7.3), in process inspection, and statistical process control inspections (see 4.4). The continuous operating temperature ranges for the sleeving classes covered by this specification are from -112 to +482 °F (-80 to +250 °C). The continuous operating temperature range for each sleeving class is given in the applicable detail specification.
This test method provides performance data on candidate insulation systems as a function of time and temperature. These data give engineering information on the wire insulation candidate relative to the performance of materials already in use with a backlog of experience. These tests expose candidate insulation systems to a wide range of temperatures for short and long periods of time, while measuring the degradation of its physical properties. For aerospace use, end-point proof tests include mandrel bend, water soak, and dielectric integrity.
AS22759 specification covers fluoropolymer-insulated single conductor electrical wires made with tin-coated, silver-coated, or nickel-coated conductors of copper or copper alloy as specified in the applicable detail specification. The fluoropolymer insulation may be polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVF2), ethylene-tetrafluoroethylene copolymer (ETFE), or other Fluoropolymer resin. The fluoropolymer may be used alone or in combination with other insulation materials. These abbreviations shall be used herein. When a wire is referenced herein, it means an insulated conductor (see 7.7).