Testing avionics & aircraft equipment to MIL-STD-704F
An aircraft bus is not a clean supply, and MIL-STD-704F is the document that says exactly how unclean it is allowed to get. You are testing avionics LRUs, ground power units, aircraft actuators and converters on 115/200 V 400 Hz AC, 28 VDC, 270 VDC, proving that the box keeps working when the aircraft bus misbehaves. The standard turns on 400 Hz and voltage transients; it says nothing about harmonic immunity sweeps or humidity/bias reliability, which belong to a different qualification entirely. Reproducing it takes programmable AC source to ≥180 V RMS L-N (≥271.8 V peak), 3-phase, 360–800 Hz plus 60 Hz, with phase-angle control and millisecond-resolution voltage/frequency envelope sequencing. DC sources to ≥50 V (28 V bus) and ≥350 V (270 V bus) with ripple injection.
What you are testing
- Device under test
- avionics LRUs, ground power units, aircraft actuators and converters
- Bus
- 115/200 V 400 Hz AC, 28 VDC, 270 VDC
- Who buys this
- airframe and avionics suppliers qualifying to a platform spec
What MIL-STD-704F does not cover
- harmonic immunity sweeps
- humidity/bias reliability
- grid ride-through
If your programme needs those, they come from a different standard and often different hardware.
The limits this test has to reproduce
The 400 Hz bus is the whole game here, and the transient envelopes are what separate a source that can run this test from one that merely reaches the voltage.
| Parameter | Value | Clause |
|---|---|---|
| Steady-state voltage (400 Hz AC, L-N) | 108.0–118.0 V RMS | Table I |
| Frequency | 393–407 Hz, modulation 4 Hz | Table I |
| Distortion factor | ≤0.05 | Table I |
| Crest factor | 1.31–1.51 | Table I |
| Peak voltage | ±271.8 V | Table I |
| Normal AC transient | surge 180 V for 10 ms; sag 80 V for 10 ms | Figure 3 |
| Abnormal AC overvoltage | V = 124.6 + 2.77/t for 0.05 ≤ t ≤ 6.925 s | Figure 4 |
| 28 VDC steady state | 22.0–29.0 V, ripple ≤1.5 V | Table IV |
| 28 VDC transient | 50 V for 12.5 ms; sag 18 V for 15 ms | Figure 13 |
| Emergency 28 V | 16–29 V | §5.3.2.3 |
| Electric starting | 12–29 V | §5.3.2.4 |
| Abnormal AC sustained | 125 V sustained (undervoltage mirror 100 V) | Figure 4 |
| Frequency rate of change | 250 Hz/s normal, 500 Hz/s abnormal | Table II |
| 28 VDC abnormal | V = 31.38 + 0.931/t; 31.5 V sustained (under 20.0 V) | Figure 14 |
The clauses aviation programmes actually face, as published in MIL-STD-704F, revision F, 12 March 2004. See every limit in MIL-STD-704F. Certification work should be run against the published standard.
What decides the rig here
The requirements that separate a system that can run this programme from one that only meets the headline numbers.
Peak, not RMS, sizes the source
The transient envelope reaches well above nominal. A source rated only on steady-state RMS will clip the surge and the test is invalid before it starts.
Frequency has to move, not just sit
Variable-frequency platforms need programmable df/dt, and a fixed-400 Hz source cannot run those clauses at all.
The DC bus is a second test programme
28 V and 270 V clauses are a separate rig from the AC work. Programmes routinely budget for one and discover the other late.
Equipment that covers it
Other standards this DUT usually faces
Further reading on MIL-STD-704F
- 28 VDC Aircraft Bus Testing: The Second Programme Inside MIL-STD-704F
- CAGE, UEI and NAICS: What a Prime's Supplier-Vetting Search Actually Resolves
- DFARS 252.204-7012 for Test-Equipment Suppliers: The 72-Hour Report and the Media You Must Not Wipe
- DO-160 vs MIL-STD-704: Where Civil and Military Aircraft Power Standards Split
- MIL-STD-1399 Testing: Your Contract May Cite a Cancelled Revision
- Sizing a 400 Hz Source for Inrush: kVA Is the Last Number to Pick
- Specifying Test Equipment in a Federal Contract: Name the Method, Freeze the Revision, Agree What Pass Means
- Solid-State 400 Hz Sources vs Motor-Generator Sets: What Actually Changes
- 400 Hz AC Source Buyer's Checklist: Sizing for Inrush, Crest Factor and Nonlinear Loads
- MIL-STD-704F for Test Engineers: The Conditions Your AC Source Must Actually Reproduce
Send us the clauses you have to satisfy
We will come back with the source and load capability that covers them — and tell you plainly if something in your spec needs hardware we would not supply.
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