AFGS�87219B APPENDIX A
The current issue of MIL-STD-704 should be specified for the electric power interface for new aircraft unless there are overriding considerations which arise. Specify the appropriate limits/interfaces from MIL-STD-704 and/or the peculiar aircraft limit/interface requirements. Commercial specifications such as SAE-AS1831 are very similar to MIL-STD-704 and should be given consideration as an alternative power quality standard if trade studies show a cost or weight savings.
When the EPS of an existing aircraft is modified, the specified power quality must be compatible with the original aircraft requirements. Therefore, the current MIL-STD-704 should be specified only if it ensures power quality equal to or greater than the original requirement.
It will be necessary to compare the requirements of the current version of MIL-STD-704 with
earlier versions of the specification to make this determination. The utilization equipment must also be compatible with the original power quality.
For unmanned aircraft, special requirements may dictate electrical power with different characteristics than MIL-STD-704. In these cases MIL-STD-704 should be considered a guide when preparing the electrical power characteristics specifications for both EPS and the using equipment.
Although this standard only defines the electrical power quality of the EPS, the system contractor must also assure that all utilization equipments are compatible with the EPS. The contractor must include the power quality specification in each vendor specification and assure that all utilization equipments are tested prior to installation on the vehicle.
REQUIREMENT LESSONS LEARNED (A.3.2.1)
Some aircraft have had problems of incompatibility between aircraft power and using equipment. In some cases, the EPS had to be reworked to accommodate the equipment even though the original power quality requirements were met. Frequently, utilization equipments are not designed or tested to the vehicle power quality standards, resulting in incompatibilities and redesign of the equipments. These problems point out that the power interface requirements must be carefully chosen and consistently applied to both the EPS and the using equipment.
A.4.2.1 Electrical power characteristics.
EPS compliance with the requirements of 3.2.1 shall be verified by analyses and tests as follows:
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VERIFICATION RATIONALE (A.4.2.1)
In order for the EPS to provide power having the required characteristics and quality, the individual subsystem components which contribute to these characteristics must perform as required. Verification of component performance can be obtained by qualification testing. In addition, it may be possible to perform certain analyses to show that the integrated EPS will
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