AFGS�87219B APPENDIX A
c. Short, easy replaceable harnesses to go between the equipment and aircraft wiring should be considered for use with equipment that is frequently removed (such as liquid oxygen converters). As the equipment is removed and replaced, the connectors become worn and have to be replaced. After a few replacements, the wires are no longer long enough and an entire harness must be replaced.
d. Aluminum wire is used on some aircraft to feed power to the load centers from the engine pylons, and from the load centers to points throughout the aircraft. Loose connections, electrolysis, and galvanic reactions have led to corrosion and arcing at the terminal boards. Fires and loss of electrical power have resulted. Therefore, aluminum wire should not be approved for use unless solutions to termination problems have been proven.
A.4.2.9 Major components. A.4.2.9.1 Aircraft wiring.
Compliance with the requirements of 3.2.9.1 for the design and installation of wiring shall be
verified by inspection.
VERIFICATION RATIONALE (A.4.2.9.1)
Verification of proper component selection requires analyses of the operational environment and performance requirements and analyses of the characteristics of the selected component. Visual inspections of wiring mockups and the first aircraft are necessary to verify proper installation. Performance is verified by aircraft continuity and dielectric checks and by operational tests of the aircraft subsystems.
VERIFICATION GUIDANCE (A.4.2.9.1)
a. Ensure that there are sufficient analyses and inspections of the aircraft wiring components and their installation to verify compliance with this requirement.
b. A physical mockup of the wiring installation should be required.
VERIFICATION LESSONS LEARNED (A.4.2.9.1)
One aircraft development program included no formal physical mockup of electrical wiring and equipment installations. Consequently, verification of physical installation requirements was delayed until the first aircraft was available for inspection. The inspection revealed numerous wiring discrepancies such as inadequate clearances, inadequate support, and improper wire lengths. Since the inspection occurred only a few days prior to first flight when several aircraft were in final assembly, corrective actions were costly and were only partially implemented. On other programs a mockup of the wiring installation has served as a useful design tool and has allowed verification of installation requirements much earlier in the program. The mockup can then be used for future aircraft modifications.
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