MIL-DTL-38999 Series III circular connector | Vibration resistant | Salt spray resistant | High temperature resistant | Waterproof | Shockproof military circular connector，Aerospace Plug&Socket, D38999 20FF11PCN

The Board-Side Half of a Series III Pair

This MIL-DTL-38999 Series III circular connector is the fixed half of a pair: a square flange receptacle whose four screws pull the flange flat against a panel, a bulkhead or an equipment housing while the plug stays with the cable assembly. What sets it apart from a wire-terminated receptacle is the back of the insert — PC short PCB pins stand out of the shell and solder into plated through-holes, so the termination sits inside the enclosure instead of inside a backshell. The contacts are gold-plated copper alloy, rated 5 A for signal circuits and 23 A for power feeds, and where a hybrid layout is needed, signal, power, coaxial and high-speed data contacts can share the same shell. Coupling is the Series III triple-start thread. Three starts pick up together, the plug comes down in a short turn, and it cannot back off unless the thread is turned out deliberately. A program that already specifies an aerospace D38999 connector on the cable assembly usually keeps the same interface here, so the mating plug is already defined.

How the Shell Copes With Salt, Heat and Vibration

• Salt air and wash-down. The electroless nickel layer is the surface that has to be salt spray resistant; it absorbs corrosion and scuffing while the aluminium alloy underneath stays sound, which is why this finish appears on shells that are handled, wiped and cleaned often.
  • Water. The interfacial seal closes only when the halves mate, and the flange gasket closes the joint at the panel. Treat the plug, its backshell and this receptacle as one waterproof military circular connector assembly, because an open shell or an open cable entry is not a sealed joint. A high temperature military connector is judged on whether the pins keep their position and the seal recovers, not on whether the shell survives a soak.
  • Vibration. With the coupling fully home, thread preload holds the plug against the flange, which is why the shell is specified as a vibration resistant circular connector on engine brackets, suspension pans and airborne racks.
  • Shock. A keyed insert and sprung contact sleeves keep the interface stable at the 100 G shock level the series is rated for, so a hard landing or a strike under a vehicle does not walk a pin out of its hole — the trait a shockproof military circular connector is picked for.
  • Mass. An aluminium shell on a gimbal, a rack shelf or a rotating mount adds very little weight, which counts on UAV and satellite hardware.

Fitting It to a Board and a Panel

1. Check the flange outline and the four fixing holes against the panel drawing before any hole is drilled; a burr under the flange tips the shell and loads one side of the gasket.
2. Solder the PCB pins into the board with the shell held square, and let the joints cool before the flange is drawn down, so the pins do not carry panel load.
3. Fit the panel gasket, set the flange in place and tighten the screws in a cross pattern; the gasket is the half of the seal that lets the installed receptacle behave as a waterproof military circular connector.
4. Keep the insert dry and free of chips while the board is handled; a smear of flux or a stray strand across the contact face is the usual reason for a poor reading at first power-up.
5. Line the keyway up and start the triple-start thread by hand. It should pick up without force; if it fights, the halves are not keyed correctly and turning harder will damage the thread.
6. Turn the coupling down until it bottoms out, then fit the backshell, boot or strain relief that matches the cable diameter so the plug carries the cable load rather than the contacts.
7. On a mount that shakes, add the locking accessory or safety wire your work instruction calls for, and check continuity again once the loom is routed and clamped.

Where This Flange Gets Bolted Down

Avionics racks and instrument panels are the usual home: the unit carries the board, the flange is fixed to the unit wall, and the aircraft loom plugs in from the front. Dash panels, weapon-station controls and power distribution boxes on armoured vehicles use the same arrangement through a bulkhead, and radar or missile-guidance racks, flight data recorders and UAV or satellite subsystems take it where the board is the reference and the cable is the part that moves.

Shipboard and offshore cabinets are harder on any plated shell, and industrial assemblies — oil and gas sensors, maritime navigation, emergency-response equipment — borrow the same sealed, keyed interface where a commercial connector is not worth the risk. What these installations share is a panel that stays put while the plug is worked, cleaned or replaced.

Configuration and Ratings for 20FF11PCN

Details to Settle Before Release

Quote the complete part number with the F finish, the F11 layout and the N keying, because changing any one field produces a different connector. If the drawing predates the current build, send it as it stands and we will cross-reference each field against what we make. Two fields account for most of the back-and-forth: contact style, where PL long PCB pins replace the PC tails when the board sits further back inside the housing, and keying, where A, B, C and D positions exist so two similar connectors on one panel cannot be cross-mated.

Say what should travel with the goods. As a D38999 connector factory we can confirm which documents accompany a batch — traceability paperwork, test records and a packing list — and note any export classification your program needs at the quotation stage. As a MIL-DTL-38999 connector manufacturer we keep finish, layout and keying on file, so a repeat order matches the first and the board drawing does not need touching.

A repair depot order and a production order need different handling, and a military circular connector supplier who knows which is which can keep later deliveries consistent. Tell your sales contact which one applies when the order is placed.

Technical Support & Model Matching

Choosing the right shell size, contact arrangement, keying and coupling for a cable assembly is where most ordering problems start, so our engineers work through it with you before anything is shipped. Send a part number, drawing or photo of the connector you are replacing and we will cross-reference it against our MIL-DTL-38999 range and confirm the closest equivalent. After delivery we stay available for mating and installation guidance, wiring questions and fault finding, and we are glad to quote bulk orders and custom designs.

FAQ