AFGS�87219B APPENDIX A
VERIFICATION LESSONS LEARNED (A.4.2.7)
The power distribution system on some aircraft has malfunctioned or been improperly designed, with the result that a failure in the distribution system resulted in partial or total loss of all electrical power. The distribution system needs the same careful design and analysis effort as the main electrical system itself.
A.3.2.8 Control and protection.
The electric power subsystem shall include all control and protective functions necessary for safe and effective operation.
a. Routine operations of the EPS such as normal start-up, shut-down, paralleling, and voltage and frequency regulation which require no crew decisions shall be performed automatically.
b. The crew shall be provided with the instruments and manual controls necessary for effective control of the EPS for normal and abnormal operation. This shall include indications of all system faults and malfunctions which affect flight safety or mission effectiveness.
c. Automatic protective functions shall be provided for abnormal conditions of the electric power subsystem which require a prompt predetermined response and for which no crew decisions are needed. Faults and malfunctions shall be detected, isolated, and de- energized in a manner which eliminates the hazardous condition with minimum effect on the safety and performance of the aircraft.
d. All distribution circuits including generator feeders, bus ties, and load circuits shall be protected against short circuits and overloads throughout their total length. Each load circuit shall be individually protected to prevent a single fault from affecting more than one critical function.
e. Multiple-wire feeder circuits shall be used as necessary to meet reliability and vulnerability requirements.
f. Redundant power circuits and components shall be routed/located separately to minimize vulnerability. Means shall be provided for detecting the failure of each redundant component.
g. Distribution buses shall be enclosed within junction boxes to reduce vulnerability. The junction boxes shall be located to take maximum advantage of the protection offered by aircraft structure.
h. Circuit breakers which are essential for flight safety shall be easily resettable by the crew.
i. Other requirements for control and protection are as follows: ------------.
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