MIL-STD-704 Aircraft Electrical Power Characteristics is a Department of Defense standard that describes a standardized power interface between a military aircraft and its equipment and carriage stores.
Topics covered include:
- Voltage
- Frequency
- Phase
- Power factor
- Ripple
- Maximum current
- Electric noise
- Abnormal conditions such as overvoltage and undervoltage
Another way of looking at it: MIL-STD-704 establishes the requirements and characteristics of aircraft electric power provided at the input terminals of electric utilization equipment.
MIL-STD-704 covers the power generation system by citing the requirements that the power system is to provide at the utilization equipment power terminals. The testing evaluates the utilization equipment for compatibility with the cited performance of the power system.
EMC is not covered by the standard but compliance to the applicable aircraft EMC requirements is stated with reference to MIL-STD-461 and MIL-STD-464.
If the information in the reference documents conflicts with MIL-STD-704, then MIL-STD-704 takes precedence. This is also true of MIL-STD-461, so if MIL-STD-704 conflicts with MIL-STD-461, the prevailing authority would have to resolve the conflict with the outcome most likely applying the more conservative requirement for overall system compatibility.
MIL-STD-704 was issued in October 1959, as a standard superseding the engineering document MIL-E-7894 dealing with aircraft electrical power. The initial MIL-STD-704 considered only 28 Vdc and 115/200 Vac at 400 Hz from a three-phase, four-wire, “y” source.
The requirements were based on the available technology for power generation and distribution without undue weight and volume demands within the airframe capacity. Revisions have been made over the years to implement new requirements, add voltage ranges, clarify and correct errors, update limits and establish more standardized test methods.
In addition to new revisions, change notices were released to make corrections between revision releases.
Want to know more? Tonex offers MIL-STD-704 Training | Aircraft Electrical Power Characteristics, a 2-day course that covers details of standardized power interface between a military aircraft and its equipment and carriage stores. Learn about MIL-STD-704 requirements, testing and measurements to ensure compatibility between the aircraft electric system, external power and airborne utilization equipment.
For more information, questions, comments, contact us.