MIL-STD-1399 Testing: Your Contract May Cite a Cancelled Revision

Standards & compliance · 4 min read · 23 cited facts

MIL-STD-1399-300B, the shipboard electric power interface standard dated 24 April 2008, was cancelled by Notice 1 on 25 September 2018 and superseded by MIL-STD-1399-300-1 — Section 300 Part 1, Low Voltage Electric Power, Alternating Current. Medium-voltage systems moved to Part 2. Vendor pages and test-lab capability sheets still cite 300B routinely, which is how a cancelled revision keeps finding its way into new acceptance procedures.

That matters at contract level. Check which document the contract invokes before the acceptance procedure is written, because the part numbering alone will not tell you. A procedure drafted against 300B verifies conformance to a document that was cancelled in 2018; whether that is a finding or a formality depends on the contract language, and the time to find out is before the procedure is signed, not at acceptance.

Three power types, and two of them are 400 Hz

The figures below are from the superseded 300B text — still the most widely republished version — because we have not read the current 300-1. Treat them as the superseded revision's figures until you hold the current document. §5.1.1 is where 300B defines them.

• Type I — 440 V rms, 60 Hz, three-phase ungrounded ship service power, with 115 V rms derived through transformers.
• Types II and III — 440 V rms at 400 Hz.
• Type III at 115/200 V rms, 400 Hz, three-phase four-wire grounded wye — the supply provided for avionics shops and aircraft servicing.

Type I and Type II characteristics were coordinated with STANAG 1008 Edition 8. If the programme carries an allied-interoperability clause, that coordination traces through the superseded revision — one more reason to confirm what the current 300-1 actually says rather than assume continuity.

A 60 Hz bench cannot cover the aviation side of the ship

Two of the three power types run at 400 Hz, and the Type III grounded-wye supply exists precisely for the equipment that services aircraft. A bench built only for 60 Hz covers Type I ship service power and stops there: it cannot power, let alone tolerance-test, anything on the 400 Hz side. A shipboard programme that reaches the avionics shop needs a source that does both frequencies, or a frequency-conversion stage in front of the bench.

The Type III figures are familiar for a reason: 115/200 V three-phase at 400 Hz is also an aircraft power type under MIL-STD-704F, which holds 400 Hz steady-state voltage at 108.0–118.0 V RMS line-to-neutral and frequency at 393–407 Hz (both Table I). Equipment that moves between the ship's servicing supply and the aircraft answers to both documents, and the acceptance limits are not interchangeable between them.

The other requirement riding on the same power leads

Shipboard equipment also answers to MIL-STD-461G CS101, conducted susceptibility on power leads: audio-frequency ripple injected in series from 30 Hz to 150 kHz, applicable to AC inputs drawing up to 30 A per phase and to all DC inputs. It is a different test with different equipment — a coupling transformer and a drive chain rather than a shipboard power simulation — but it lands on the same leads, and it belongs in the same bench conversation from the start.