Quick answer: Under gjb 150a, clause 150.16A maps to MIL Method 514 and 150.18A to Method 516. The real gap is where levels come from: tailoring sets them.
Table of contents
- Mapping GJB 150A Clauses to MIL Methods
- Where the Levels Diverge: 30 g and 3 dB
- The Tailoring Report GJB 150A Demands
- Report Format, Retained Samples, Five-Year Retest
- FAQ
1. Mapping GJB 150A Clauses to MIL Methods
When a programme cites both standards, the first question is not which test to run but which clause matches which. GJB 150A splits into 28 parts by environmental agent, each tracking one MIL-STD-810F method. Numbering differs; the thing judged does not.
What does not line up is the edition. GJB 150A was written against MIL-STD-810F, the 500 series with .5 suffixes; laboratories now quote 810H, which has moved to .8. Different tolerances and procedure counts follow, so dropping an 810H level into a GJB 150A clause is the commonest mismatch in a quotation.
| GJB clause | MIL method | Where they diverge |
|---|---|---|
| 150.3A high temperature | 501.5 | +70 °C ceiling, soak timed to thermal equilibrium |
| 150.4A low temperature | 502.5 | -55 °C floor, cold-soak judged on internal channel |
| 150.16A vibration | 514.5 | Level and spectrum tailored from measured road data |
| 150.18A shock | 516.5 | Peak set by mission profile, not a fixed nominal |
The last column is what gets skipped. The first three can be matched from a table; the fourth cannot, because the shock clause fixes method and procedure but not a peak. That number lives in the tailoring report.
This explains a familiar argument: two laboratories test one case and report 30 g and 40 g. Neither is wrong. They are citing documents at different levels.
2. Where the Levels Diverge: 30 g and 3 dB
The 10 g gap is a 25% difference in acceleration margin. On a 12 kg case with an 11 ms pulse, the velocity change falls from 2.2 m/s to 1.65 m/s, and the equivalent force at the latch seat drops by about a quarter.
The difference is in how values are set, not an error. MIL supplies a default for programmes with no measured data; GJB 150A supplies a method and expects the level to be derived from the mission profile. A unit on a wheeled chassis over broken gravel may measure 28 g, so 30 g already carries margin; the same clause tailored for an air-drop case can exceed 60 g.
| Test | GJB typical | MIL typical | Gap |
|---|---|---|---|
| Shock peak | 30 g / 11 ms | 40 g / 11 ms | 25% lower |
| Vibration level | 3 dB below reference | Reference spectrum | Half the power |
| High temperature | +70 °C | +71 °C | 1 °C lower |
| Low temperature | -55 °C | -51 °C | 4 °C lower |
Read the four rows together. The temperature rows sit within 1 °C and 4 °C, so the climatic levels were always close and the real divergence is mechanical, which is also where the case works hardest and quotations spread widest.
A 30 g level is not the lenient option. Lower peaks are gentler on ultimate strength but harder on fatigue: an equivalent test needs longer duration or more cycles, and the case sits on its resonances for longer.
A decibel is a power ratio, so 3 dB off the acceleration is a factor of 0.707: 0.071 Grms becomes 0.05 Grms. Every resonance between 10 Hz and 500 Hz scales down together, and time to bolt loosening stretches out.
Longer is not exempt. A case that cracks after 1 h per axis, 3 h total, at the reference may need 4 h at 0.05 Grms to show the same crack. The report therefore has to state whether duration was increased to offset the level; cut the level and stay silent, and the criterion has quietly been relaxed.
Two more numbers get lost here. Fixture first resonance should sit above 500 Hz, or the fixture absorbs the top of the spectrum. Control tolerance is usually held to ±3 dB; exceed it and the problem is the fixture or the amplifier, not the case.
3. The Tailoring Report GJB 150A Demands
Tailoring is where the two systems part company. MIL discusses it; GJB 150A makes it a deliverable that justifies each chosen level clause by clause.
| Report section | What it must contain | Usual rejection |
|---|---|---|
| Mission profile | Transport mode, road class, handling count | "Road transport" with no class |
| Measured environment | Channel location, sample rate, valid samples | Channel on the lid, not inside |
| Level derivation | Factor from measurement to test level | Factor quoted with no source |
| Test sequence | Seven steps and the checks between them | Sequence differs from the plan |
| Pass criteria | Structural and functional, listed apart | "No damage" alone |
| Deviations | Every departure from the clause text | Deviation omitted or added late |
Two sections draw most rejections. Level derivation must show whether the measured spectrum was enveloped or fatigue-equated, since the two give different numbers from one data set. Deviations must list everything not done as written; a missing entry reads as an omission.
Exclusions count as content. If a test was waived because the unit never meets that environment, the report states it and gives the basis.
4. Report Format, Retained Samples, Five-Year Retest
The report follows the GJB format, not the MIL one. Cover, conditions, equipment list, process record and conclusion are laid out differently, and a translated English report usually fails at the conditions section: GJB expects the tailoring conclusion there, MIL only cites the method.
Retention is the other divergence. A mechanical campaign usually keeps 1 sample, runs the full sequence on it, then seals it with a label carrying lot number, test date and tests performed. Sealed samples are not reused; the next campaign draws a fresh one.
Retest interval is set by the programme document, commonly 5 years, or at once on a design or material change. The figure is not in the standard: impact strength falls roughly 1%–2% a year under UV and thermal-oxidative exposure, so a decade costs a fifth of the margin.
Conclusion
GJB 150A and MIL-STD-810 share an origin but not an edition, and share methods but not levels: 150.16A lines up with Method 514, 150.18A with Method 516, and the numbers return to the tailoring report. The 30 g, 3 dB and -55 °C gaps are paths, not mistakes.
This article covers case-side specifications only and does not address any handling, loading or use of the contents.
Related Reading
- The GJB military case standard system
- Military packaging: GJB against MIL
- MIL-STD-810H compliance points for cases
- Setting vibration level and sweep rate
- Military packing box standards and marking
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