AFGS�87219B APPENDIX A
VERIFICATION LESSONS LEARNED (A.4.2.8)
Verification of the control and protection system to isolate and remove faults is essential. This will result in the system still being able to provide power to the non-affected areas. One system failed to detect a small fault that eventually grew until the entire electrical system shut down. Adequate fault detection and isolation would have prevented this.
A.3.2.9 Major components.
Criteria shall be established for major components of the EPS as necessary to enable the requirements of the integrated subsystem to be met.
A.3.2.9.1 Aircraft wiring.
The design and installation of wiring associated with the electric power subsystem shall be as follows: .
REQUIREMENT RATIONALE (A.3.2.9.1)
EPS performance and reliability is dependent to a large extent on the integrity of the wiring which interconnects the subsystem. Wiring components must be suitable for the application with particular attention given to the environment. Considerations for wiring installation should include maximum reliability, minimum interference and coupling between subsystems, accessibility for inspection and maintenance, and protection against damage. Since the wiring is normally expected to last for the entire service life of the aircraft, special care is required in its design and installation. SAE-AS50881, DH 1-6, and DH 2-3 provide guidance based on years of experience with aircraft wiring installations and on the capabilities of wiring components.
REQUIREMENT GUIDANCE (A.3.2.9.1)
Use SAE-AS50881 for wiring requirements. Older systems may reference the inactive standard, MIL-W-5088.
REQUIREMENT LESSONS LEARNED (A.3.2.9.1)
a. Most problems with aircraft wiring have involved deterioration caused by the environment, aging, improper application of materials and components, and abuse of various kinds. Moisture, heat, vibration and rough handling are common hazards which should be recognized and guarded against during subsystem design.
b. In Vietnam, aircraft experienced a major problem when the potting compound in the electrical connectors reverted to a sticky, gummy mass because of heat and humidity. This cost millions of dollars and extensive downtime to repair. Environmentally-sealed connectors which do not require potting are now preferred for most applications. Where potting is required, use should be restricted to those materials which have been qualified to the service environment.
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