MIL-DTL-38999 Connector Reference & Guide

Welcome to your comprehensive resource for MIL-DTL-38999 connectors. This guide provides detailed information on specifications, part number decoding, insert arrangements, accessories, and applications for these high-performance connectors widely used in military and aerospace industries.

What is MIL-DTL-38999?

MIL-DTL-38999 is a United States military specification that describes four series of miniature, high-density, circular connectors designed for harsh environments. These connectors are widely used in military and aerospace applications due to their high performance, reliability, and ability to withstand extreme conditions such as shock, vibration, and extreme temperatures. They feature quick coupling mechanisms and EMI/RFI shielding capabilities, making them suitable for both digital and analog signal transmission, as well as power applications.

Connector Series and Types

MIL-DTL-38999 connectors are categorized into four series, each with unique coupling methods, features, and applications:

Connector Series

Military Part Numbers

The connectors are identified using standardized military specification sheet numbers (D38999/XX), where XX designates the specific connector type and series. Below are common military part numbers associated with each series:

Technical Specifications

MIL-DTL-38999 connectors are engineered to meet stringent military and aerospace requirements. Below are key technical specifications:

Refer to manufacturer datasheets and the official MIL-DTL-38999 specifications for detailed engineering information and additional parameters.

Advantages and Disadvantages

Advantages

• High contact density in a compact form factor
• Excellent EMI/RFI shielding capabilities
• Multiple coupling mechanisms for quick and secure connections
• Wide range of materials and finishes for different environmental conditions
• High resistance to shock and vibration
• Operating temperature range from -65°C to +200°C
• Scoop-proof designs prevent contact damage during mating
• Multiple keying options to prevent mismating

Disadvantages

• Higher cost compared to other connector types due to advanced features
• Smaller contacts may be more delicate and require careful handling
• Complexity in selecting the appropriate configuration among numerous options

Insert Arrangements

MIL-DTL-38999 connectors offer a variety of insert arrangements to accommodate different contact types and configurations. These arrangements define the number of contacts, their sizes, and their positions within the connector.

Understanding Insert Arrangement Numbers

Insert arrangements are identified by a two-part number, indicating the shell size and a specific arrangement code. For example, "15-5" refers to shell size 15 with arrangement 5.

Common Insert Arrangements

Special Contact Types

MIL-DTL-38999 connectors support various special contact types:

• Coaxial Contacts: For RF signals
• Twinax and Quadrax Contacts: For high-speed data transmission
• Fiber Optic Contacts: For optical communication
• Power Contacts: For high-current applications

Selecting an Insert Arrangement

Consider the following factors:

• Electrical Requirements: Current, voltage, signal type
• Contact Density: Number and size of contacts needed
• Environmental Conditions: Temperature, sealing requirements
• Mechanical Constraints: Available space, connector size

Keying and Polarization

MIL-DTL-38999 connectors offer multiple keying positions to prevent mismating in systems using multiple identical connectors. This is achieved through rotational polarization of the inserts and shell keying arrangements.

Insert Arrangement Charts

For detailed diagrams and specifications, refer to:

• Amphenol Aerospace MIL-DTL-38999 Connectors
• Glenair D38999 Connectors

Part Number Decoder

MIL-DTL-38999 part numbers provide detailed information about the connector's configuration, including series, material, finish, shell style, insert arrangement, contact type, and keying position. Understanding the part numbering system is crucial for specifying the correct connector.

Example Part Number Structure:

D38999/ 26   F    A   35    P   N
│        │    │    │   │     │   └─ Polarizing Position: N, A, B, C, D, E
│        │    │    │   │     └───── Contact Type: P - Pin, S - Socket
│        │    │    │   └─────────── Insert Arrangement
│        │    │    └─────────────── Shell Style/Type
│        │    └──────────────────── Material/Finish Code
│        └───────────────────────── Specification Sheet Number
└────────────────────────────────── Basic Specification (MIL-DTL-38999)
                

Part Number Breakdown

1. Basic Specification: Indicates the military specification. For MIL-DTL-38999 connectors, it is "D38999".
2. Specification Sheet Number: "/26" designates the specific connector type and series. For example:
   • /20: Series III Wall Mount Receptacle
   • /24: Series III Jam Nut Receptacle
   • /26: Series III Straight Plug
3. Material/Finish Code: Indicates the material and finish of the connector. Common codes include:
   • F: Electroless Nickel Plated Aluminum
   • W: Olive Drab Cadmium over Nickel Plated Aluminum
   • K: Passivated Stainless Steel
   • J: Conductive Black Zinc Nickel (RoHS Compliant)
4. Shell Style/Type: Indicates the connector's shell style. Examples:
   • A: Standard Plug
   • B: Plug with RFI Shielding
   • E: Square Flange Receptacle
   • F: Jam Nut Receptacle
5. Insert Arrangement: Specifies the insert arrangement code that defines the contact configuration (e.g., "35"). Refer to the insert arrangement charts for details.
6. Contact Type: Indicates whether the connector has pins or sockets:
   • P: Pin Contacts
   • S: Socket Contacts
   • H: Hermetic Seal
7. Polarizing Position: Defines the rotational position of the insert for keying purposes to prevent mismating. Common positions are "N" (Normal), "A", "B", "C", "D", "E".

Example Explained

For the part number D38999/26FA35PN:

• D38999/26: MIL-DTL-38999 Series III Straight Plug
• F: Electroless Nickel Plated Aluminum
• A: Standard Plug Shell Style
• 35: Insert Arrangement Number 35
• P: Pin Contacts
• N: Normal Polarizing Position

Additional Notes

• Always refer to manufacturer catalogs or the MIL-DTL-38999 specification for exact definitions of codes, as there may be variations.
• Certain connectors may have additional modifiers or codes for specific features such as filter contacts, special seals, or other options.
• When specifying connectors, it's important to ensure all parts of the part number accurately reflect the desired connector configuration.

For a comprehensive guide, consult the manufacturer's part number decoder tools or the official MIL-DTL-38999 documentation.

Accessories and Backshells

Enhance connector performance with various accessories:

• Backshells: For strain relief and EMI/RFI shielding
• Protective Caps: Prevent contamination when connectors are unmated
• Cable Adapters: Facilitate different cable types and terminations
• Heat Shrink Boots: Provide environmental sealing and insulation
• Grommets and Seals: Enhance ingress protection

Cross-Reference Guides

Find equivalent connectors across different manufacturers:

Technical Resources

Access detailed technical documents and datasheets:

• MIL-DTL-38999 Specification Document
• Amphenol Aerospace MIL-DTL-38999 Connectors
• Glenair D38999 Connectors

Applications

MIL-DTL-38999 connectors are ideal for applications requiring high reliability in harsh environments:

• Aerospace Systems: Avionics, flight control systems, navigation equipment
• Military Equipment: Communications, ground vehicles, weapon systems
• Space Exploration: Satellites, spacecraft instrumentation
• Commercial Aviation: In-flight entertainment, cockpit systems
• Industrial Automation: Robotics, control systems in harsh environments
• Oil & Gas: Downhole tools, exploration equipment
• Medical Equipment: Imaging systems requiring reliable connections
• Transportation: Railway signaling, marine navigation

FAQs

Common questions about MIL-DTL-38999 connectors:

What are the differences between the series (I, II, III, IV)?

The series differ mainly in their coupling mechanisms and performance characteristics:

• Series I: Bayonet coupling, general-purpose connectors
• Series II: Scoop-proof bayonet coupling to prevent contact damage
• Series III: Threaded coupling with triple-start threads for quick mating, high-density, and superior EMI shielding
• Series IV: Quick-disconnect coupling using breech-lock mechanism for rapid mating/unmating

How do I select the appropriate plating or finish?

Choose based on environmental requirements:

• Olive Drab Cadmium over Nickel: Good corrosion resistance, conductive, commonly used in military applications
• Electroless Nickel: High conductivity, excellent EMI shielding
• Black Zinc Nickel: RoHS compliant alternative to cadmium
• Stainless Steel Passivated: Best for highly corrosive environments
• Composite Materials: Lightweight and corrosion-resistant

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