What are major differences between MIL-DTL-38999 Series I, II, III connectors?

What are major differences between MIL-DTL-38999 Series I, II, III connectors?

MIL-DTL-38999 connectors are designed and developed to meet the most strict requirements of the aerospace industry and the military. There are four series of MIL-DTL-38999 connectors consist of threaded, bayonet, and Breech Lok coupling mechanisms. They are environmentally immune connectors that use removable crimp contacts and can work in a wide range of temperature from -65 to +200°C. Many companies in the U.S. are the leading military component suppliers to the aerospace industry and the military.
Common characteristics of connectors:
Connectors usually comprise of a mating pair (plug and receptacle) each provided with male (pin) or female (socket) contacts. In order to reduce mechanical stresses, one of the connector halves, or its contacts, should be floating.

Types of connectors:

• Electrical connector contacts are usually Beryllium copper or Phosphor bronze which is coated with gold or some other highly-conductive, non-corrosive metal. The contacts are held by a dielectric insulator and are placed in an enclosure, that is mostly die-cast aluminum and plated to protect from corrosion. The contacts either can be captive or removable using a special tool.

• Fiber optic connectors are so-called male or typically plugs connectors with an extending ferrule that grips the fibers and arranges two fibers for mating. They make use of an adapter to mate the two connectors that suit the securing mechanism of the connectors.

The main differences between MIL-DTL-38999 series I, II, and III are:

• MIL-DTL-38999 series I connectors are bayonet coupled connectors and Series I connectors are bayonet coupled and posses high-vibration properties. They have almost 100% scoop proof design, available for connector size from 9 to 25. Series I connectors are ideal for moisture environment and heavy wind. They are employed when a fast disconnect coupling system is needed.

• MIL-DTL-38999 series II connectors are bayonet coupled low profile connectors. They have a non-scoop proof design, available for connectors size 8 to 24. Series II is used when space or weight is limited, or in high moisture, low-vibration, and strong wind conditions.

• MIL-DTL-38999 series III connectors are coupled by a thread. They have 100% scoop proof design, available for connector size 9 to 25. They are best matched for normal mating and unmating applications and can withstand high temperature, wind, moisture, or vibration environment.