As noted in an earlier blog post, the tests you run to ensure that airborne utilization equipment is compatible with an aircraft’s power system are specified in a series of MIL-HDBKs, specifically MIL-HDBK-704-1 through MIL-HDBK-704-8. To run these tests, a sophisticated power source is essential to simulate various power conditions. In addition, you also need whatever equipment is required to monitor the unit under test (UUT) while running the test.

Recognized as a world leader in programmable power, AMETEK Programmable Power has provided test equipment for compliance tests for airborne utilization equipment for decades. Over the years, we’ve updated our systems to cover the latest versions of MIL-STD-704 and to make our test equipment more effective and easier to use. Our MIL-STD-704 test solutions are in use by customers in U.S. and in countries all over the world.

Rev. F doesn’t negate earlier versions

Although the latest version of MIL-STD-704 is rev. F, you may have to run tests that comply with previous versions of the standard. The reason for this is that aircraft platforms tend to have a long life, and the power systems in those aircraft may be designed to comply with an earlier version of MIL-STD-704. When testing the utilization equipment for a particular platform, then, it’s imperative that you know what revision of MIL-STD-704 that the aircraft platform was designed to comply with.

The early versions of MIL-STD-704 specified the requirements for fewer types of power systems than the later revisions. Rev. A, for example, described the requirements for only three aircraft electric power systems:

  • three-phase 115V/400Hz AC,

  • single phase 115V/400Hz AC for devices requiring less than 500VA, and

  • 28V DC.

In rev. B, the authors added requirements for the 270V power system.

In rev. F, there are specifications for seven different power systems. In addition to the four already mentioned, rev. F includes specifications the following aircraft electric power systems:

  • single-phase, 115V/360-800Hz various frequency,

  • three phase 115V/360-800Hz various frequency, and

  • single-phase 115V/60Hz to power commercial, off-the-shelf (COTS) equipment.

Figure 1. Select the MIL-STD-704 version as needed.

Because utilization equipment may have to comply with earlier versions of MIL-STD-704, AMETEK Programmable Power’s test solutions allow users to easily select the appropriate version of the specification when setting up the test. As shown in Figure 1, test engineers and technicians, simply choose the appropriate revision from a drop-down menu.

Figure 2. Select the appropriate power group.

The next step is to choose the type of power that the power source is to supply to the utilization equipment. This is done by selecting one of the power groups as shown in Figure 2.

MIL-HDBK-704-1 through MIL-HDBK-704-8 specify the acronyms used for the seven power groups. They are:

  • SAC (single phase 115V/400Hz),

  • TAC (three phase 115V/400Hz),

  • SVF (single phase 115V various frequency),

  • TVF (three phase 115V various frequency),

  • SXF (single phase 115V/60Hz),

  • HDC (270V DC), and

  • LDC (28V DC).

Once these have been selected, the power source will supply power that simulates the various operating conditions as specified in MIL-STD-704. These include normal, transfer, abnormal, emergency, electric starting and power failure conditions. When subjected to these power conditions, the utilization equipment is expected to operate normally and perform to specifications.

These documents, including MIL-STD-704 (revisions A through F) are available online at EverySpec.Com. For information on how to use AMETEK power sources to run MIL-STD-704, contact AMETEK Programmable Power. You can send an e-mail to sales.ppd@ametek.com or phone 800-733-5427.

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