Rob writes:

<<<I do not know if MS38999 connectors (known as "thirty-eight triple-nine" connectors) are the same connectors as the AMP Circular Plastic Connectors that Brent recommends.>>>

They are not. Many connector manufacturers (Cannon, Amphenol, Glenair, Souriau, Hypertronics etc.) produce connectors that are compliant to MIL-C-38999. Under that specification there are many combinations of pins sizes, number of contacts, shell material, strain relief, mounting configuration and mating latch type. The Chelton Flight Logic (certified) IDUs use 38999 connectors on the back of their trays for connection to the airframe.  The IDU to Tray connection utilizes ARINC-600 pins and sockets in a custom design.

The 38999 is an excellent choice for most aerospace applications. Recognizing this, Bell Helicopter requires that I get permission to use anything other than a 38999 in the new Chelton 10.4" system we are designing for the 417.  There are better connectors for specialized applications. For example, on the benthic Telemanipulators (Alvin submersible) I used a mineral oil back filled, hermetically sealed geo-marine connector that would tolerate a 20,0000 PSI differential pressure. At $600 each for a 35 pin connector you tended to use as few as possible.

The AMP CPC connectors are a commercial plastic shell connector that is similar in design to a 38999 type III. They have no high frequency shielding and a lower vibration and temperature rating but are a very good cost to performance value. Lancair has been using these in their instrument panels for years and they work fine in the passenger compartment. I would not recommend them for use in the engine compartment but many have. Amp also makes machined (aerospace style) contacts (with 30 micron gold plating) for these connectors, also recommended.

Regards
Brent Regan