38999 Part-Number Decode Worksheet
Based on §7.8 of the MIL-DTL-38999 deep dive — the worked example and its caveats live there; this page turns them into a form you fill in against your part number and your manufacturer's catalog.
D38999 part-number schemas vary by manufacturer (Amphenol, Glenair, Souriau, ITT Cannon, TE, Eaton). Finish letters, available arrangements, and accessory codes are not identical across vendors. Always decode against the specific manufacturer's catalog/decoder, and verify against the QPL when qualification matters. "Mil-spec style," "MIL-compatible," or "built to a military standard" does not automatically mean the exact part is qualified. A conforming part number from two vendors is not automatically interchangeable — match series, shell size, insert arrangement, contact type, finish, and keying.
The worksheet
Example column decoded per the manufacturer catalog cited in §7.81 — your letters may mean something else in your vendor's schema. Fill in the last two columns from the catalog you are actually buying against, and record the catalog document + revision at the bottom.
| Field | Example: D38999/26WE26PN | Meaning in the example's decoder | Your part number | Meaning per your catalog |
|---|---|---|---|---|
| Base spec + shell style | D38999/26 | Series III; /26 = straight plug in this decoder family | ||
| Finish / material class | W | Corrosion-resistant olive-drab cadmium-plated aluminum (finish letters vary by manufacturer) | ||
| Shell-size letter | E | Maps through the catalog to shell size 17 | ||
| Insert arrangement | 26 | Read with the shell size: full designation 17-26 | ||
| Contact type | P | P = pin, S = socket | ||
| Polarization / keying | N | N = normal (positions N, A, B, C, D, E) |
Read it as linked fields: the shell-size letter gives the shell size, and the trailing number is the insert arrangement within that shell size. The arrangement number alone is not the full insert arrangement — the same number means different things in different shell sizes, so always pair them.
Keying positions: the master keyway stays fixed; the minor keyways rotate per position. Angles differ by shell size — decode from the catalog.
Record with the decode
- Manufacturer and catalog/decoder document, with revision/date
- Full insert-arrangement designation (shell size + arrangement), from the arrangement drawing
- Contacts included or ordered separately ("less-contact" part numbers exist — §7.9)
- Keying position documented in the ICD — don't rely on technician memory
- QPL/QPD status of the exact part number, where qualification matters
This is a working tool, not a standard. The manufacturer's catalog, the applicable specification, and program requirements always win.