M Series Connectors
Are lightweight triplestart ratchet coupling type connectors designed for avionics, aerospace, Harsh Environment Connectors, security, motorsport and heavy duty applications.
Product Information
The Comprehensive Guide for D38999 Connector
26
Sep
Sep
Introduction to D38999 Connectors
1. What is MIL-DTL-38999?
The MIL-DTL-38999 series connectors are high-performance circular electrical connectors that comply with the U.S. Department of Defense technical standard (latest revision: Type G). Their European equivalent standard is EN3645. D38999 connectors are widely used in military, aerospace, industrial automation, and other harsh environments. Since their development in the 1960s, the D38999 series has continuously enhanced electromagnetic compatibility (EMC) and resilience to extreme conditions, becoming the global benchmark for high-reliability interconnect solutions.
2. Key Features of D38999 Connectors
- High-Density Design:
Supports 2–100+ contacts per shell, meeting high-density wiring requirements.
- Environmental Resistance:
Operating temperature: -65°C to +200°C (short-term up to +260°C).
Salt spray test: ≥500 hours without corrosion (MIL-STD-202 Method 101).
Protection rating: IP67–IP68 (immersion up to 10 meters).
- Quick Coupling:
Triple-start thread with self-locking mechanism, enabling single-handed connection in under 3 seconds.
- Vibration & Shock Resistance:
Compliant with MIL-STD-202 vibration and shock standards.
- Versatile Contact Types:
Capable of integrating signal, power, fiber optic, and coaxial contacts.
- Lightweight Construction:
Titanium alloy shells are 30% lighter than aluminum while maintaining high strength.
3. D38999 Series Classification
The MIL-DTL-38999 connector family is divided into four series (I, II, III, and IV). Each series represents a different coupling mechanism and performance level, which directly influences the part number decoding process.
For most aerospace and defense applications, D38999 iii remains the preferred choice due to its IP68 sealing and vibration resistance. Series I and II are suitable for applications requiring faster mating or ground-based systems. Series IV and I.5 serve more specialized niches such as space and next-generation aviation.
4. D38999 Applications
Aerospace: D38999 connectors are widely used in avionics, engine control, and flight control systems, providing reliable performance under high vibration and extreme temperature variations.
5. D38999 Part Number Guide
The D38999 part number follows a modular coding system, where each character represents a specific parameter (shell, arrangement, plating, keying, gender, etc.). Understanding the meaning of each segment is essential for correct connector selection.
D38999 Part Number Breakdown
The D38999 I Series uses a bayonet coupling mechanism, and its part numbers typically highlight faster mating speed and lightweight design, making it suitable for ground-based and quick-disconnect applications.
Example: MS27467T21F35PN-H
The D38999 III Series features a Tri-Start threaded coupling with self-locking, and its part numbers indicate IP68 sealing and maximum durability, making it the preferred choice in aerospace and harsh environments.
Example:D38999/20WB35PN-H
Common Confusions in D38999 Part Numbers
Contact arrangement vs. shell size: These are independent parameters and must not be confused.
Keying codes: Letters A–E represent different anti-mismating structures; an incorrect choice will prevent proper mating.
Plating codes: Cadmium plating (W) vs. nickel plating (F) directly affects corrosion resistance.
Contact gender: S = socket (female), P = pin (male); incorrect pairing may result in contact damage.
6. Configuration Guide
D38999 Connector Contact Types and Sizes
When selecting MIL-DTL-38999 connectors, the choice of contact type and size is crucial for ensuring electrical performance and reliability.
Engineers should carefully select contact types based on current capacity, signal integrity, and data transmission requirements. For example, size 22D contacts are ideal for low-current signal applications such as MIL-STD-1553B buses, while size 8 power contacts can support up to 100A, suitable for energy storage systems or high-load UAV applications. Fiber optic contacts (LC type) are increasingly used in aerospace and defense projects requiring high-bandwidth, EMI-immune connections.
D38999 Backshells and Accessories
Backshells and accessories enhance connector performance under demanding environments:
EMI shielding backshells: provide ≥90dB shielding effectiveness, essential for radar, avionics, and satellite communication systems.
Strain relief clamps: support ≥100N tensile strength, preventing cable breakage and extending service life in mobile platforms.
Environmental sealing backshells (IP68): designed for underwater robotics, submersibles, and harsh marine conditions. Selecting the correct backshell not only improves reliability, but also ensures compliance with EMC and IP protection standards.
D38999 Mounting Methods
D38999 connector can be installed in multiple ways depending on the application environment, vibration level, and sealing requirements.
D38999 Jam nut mounting is recommended for high-vibration environments such as aerospace engines or defense vehicles, while box mounting provides a reliable sealing solution for industrial cabinets.
D38999 Environmental Sealing Options
To ensure long-term durability and resistance to extreme environments, D38999 connectors can be configured with different sealing technologies:
Fluororubber O-rings: withstand temperatures from -40°C to +200°C, suitable for aerospace and military-grade applications.
Silicone rubber sealing plugs: block unused contact cavities, providing IP68 protection.
Epoxy potting compounds: applied for space systems such as satellite propulsion units, ensuring hermetic sealing and vibration resistance. Proper sealing extends connector lifespan and guarantees stable performance in aerospace, defense, and industrial automation.
7. D38999 Equivalent Part Numbers
When sourcing D38999 connectors, engineers often face the challenge of finding equivalent part numbers across different brands such as Amphenol, Souriau, and Renhotec. Since all of these connectors conform to the MIL-DTL-38999 military standard, they are designed to be intermateable and interchangeable as long as the series (e.g., Series III) and keying code are the same. This means that connectors from Renhotec, Souriau 8D, or Souriau EN3645 series can often serve as drop-in replacements for each other without impacting electrical or mechanical performance.
D38999 Cross-Reference Chart
Below is a D38999 cross reference chart showing typical equivalent part numbers from Renhotec, Souriau-8D, and Souriau-EN3645 series.
| Renhotec | Souriau-8D | Souriau-EN3645 |
| D38999/26WA35SN | 8D5-09W35SN | EN3645W6AN35FN |
| D38999/24WA35PN | 8D7-09W35PN | EN3645W7AN35MN |
| D38999/26WB35SN | 8D5-11W35SN | EN3645W6BN35FN |
| D38999/24WB35PN | 8D7-11W35PN | EN3645W7BN35MN |
| D38999/26WB35SA | 8D5-11W35SA | EN3645W6BN35FA |
| D38999/24WB35PA | 8D7-11W35PA | EN3645W7BN35MA |
| D38999/26FB35PN | 8D5-11F35PN | EN3645F6BN35MN |
| D38999/20FB35SN | 8D0-11F35SN | EN3645F0BN35FN |
| D38999/26WC98SN | 8D5-13W98SN | EN3645W6CN35FN |
| D38999/20WD97PN | 8D0-15W97PN | EN3645W0DN97MN |
| D38999/20WB35PN | 8D0-11W35PN | EN3645W0BN35MN |
| D38999/20WD5PN | 8D0-15W5PN | EN3645W0DN5MN |
| D38999/20WE6PN | 8D0-17W6PN | EN3645W0EN6MN |
| D38999/20WC4PN | 8D0-13W4PN | EN3645W0CN4MN |
| D38999/20WC98PN | 8D0-13W98PN | EN3645W0CN98MN |
| D38999/20WB5PN | 8D0-11W5PN | EN3645W0BN5MN |
| D38999/20WB4PN | 8D0-11W4PN | EN3645W0BN4MN |
| D38999/20WB98PN | 8D0-11W98PN | EN3645W0BN98MN |
| D38999/20WA98PN | 8D0-09W98PN | EN3645W0AN98MN |
| D38999/20WA35PN | 8D0-09W35PN | EN3645W0AN35MN |
| D38999/20WD19PN | 8D0-15W19PN | EN3645W0DN19MN |
| D38999/26WD5SN | 8D5-15W5SN | EN3645W6DN5FN |
| D38999/26WE6SN | 8D5-17W6SN | EN3645W6EN6FN |
| D38999/26WC4SN | 8D5-13W4SN | EM3645W6CN4FN |
| D38999/26WB5SN | 8D5-11W5SN | EN3645W6BN5FN |
| D38999/26WB4SN | 8D5-11W4SN | EN3645W6BN4FN |
| D38999/26WB98SN | 8D5-11W98SN | EN3645W6BN98FN |
| D38999/26WA98SN | 8D5-09W98SN | EN3645W6AN98FN |
| D38999/26WD19SN | 8D5-15W19SN | EN3645W6DN19FN |
| D38999/26WD97SN | 8D5-15W97SN | EN3645W6DN97FN |
| D38999/26FD5SN | 8D5-15F5SN | EN3645F6DN5FN |
| D38999/20FD5PN | 8D0-15F5PN | EN3645F0DN5MN |
| D38999/20WD19SN | 8D0-15W19SN | EN3645W0DN19FN |
| D38999/26WD35PN | 8D5-15W35PN | EN3645W6DN35MN |
| D38999/26WC98SA | 8D5-13W98SA | EN3645W6CN98FA |
| D38999/26WC35SN | 8D5-13W35SN | EN3645W6CN35FN |
| D38999/26WC35SB | 8D5-13W35SB | EN3645W6CN35FB |
| D38999/26WC35SA | 8D5-13W35SA | EN3645W6CN35FA |
| D38999/26WG35SB | 8D5-21W35SB | EN3645W6GN35FB |
| D38999/26WG35SA | 8D5-21W35SA | EN3645W6GN35FA |
| D38999/26WE8PN | 8D5-17W8PN | EN3645W6EN8MN |
| D38999/24WE8SN | 8D7-17W8SN | EN3645W7EN8FN |
| D38999/26FB5PN | 8D5-11F5PN | EN3645F6BN5MN |
| D38999/20FB5SN | 8D0-11F5SN | EN3645F0BN5FN |
| D38999/26FG35SN | 8D5-21F35SN | EN3645F6GN35FN |
| D38999/24FG35PN | 8D7-21F35PN | EN3645F7GN35MN |
The complete cross-reference list ensures engineers can quickly identify an equivalent Souriau EN3645 part when only a Renhotec or Amphenol part number is available. This simplifies procurement, especially in industries where supply chain flexibility is critical, such as aerospace, defense, and industrial automation.
Tips for Selecting Equivalent D38999 Connectors
Even though D38999 connectors are standardized, engineers must pay attention to several critical details when selecting alternative or replacement part numbers:
- Match the insert arrangement code
The insert arrangement (e.g., 35, 98, 19) defines the number and size of contacts. A mismatch will lead to pinout incompatibility. Example: D38999/26WA35SN (Renhotec) can be replaced by Souriau 8D5-09W35SN or EN3645W6AN35FN because they share the same arrangement.
- Verify plating and material finish
Surface finish impacts corrosion resistance and durability. Cadmium-plated shells are common in military applications, while nickel or black zinc nickel plating may be required for RoHS compliance.
- Check mechanical interfaces
Ensure compatibility between threaded coupling (Tri-Start thread) and bayonet coupling. They are not interchangeable. For example, a Series III Tri-Start connector (Amphenol TV series, Renhotec D38999/26, or Souriau 8D5) must be matched with the same threaded interface.
- Consider brand-specific designations
Amphenol often uses “TV” or “LJT”part numbers. Souriau designates them as 8D series or EN3645 (for European aerospace compliance). Renhotec follows the D38999 nomenclature directly.
8. Tips for Selecting the Right D38999 Connector
When choosing a D38999 connector, the right selection depends on your operating environment, usage pattern, and application requirements. Below are practical tips that help engineers and procurement teams avoid costly mistakes.
Consider the Operating Environment
High vibration or shock → Choose Tri-Start thread coupling (Series III), which provides strong resistance to loosening.
Corrosive or marine environments → Opt for stainless steel shells or cadmium plating for maximum corrosion resistance.
High temperature applications → Select connectors with high-temperature-rated materials and insulators to ensure long-term reliability.
Balance Sealing vs. Connection Frequency
Frequent connect/disconnect → Use bayonet (Series I) or double-start (Series II) connectors for faster mating.
Long-term sealing → Choose Series III with environmental sealing grommets, ideal for aerospace and defense systems requiring durability.
Common Mistakes to Avoid
Wrong keying position → May lead to mismating; always verify the keyway code.
Ignoring plating options → Plating impacts corrosion resistance and service life; match it to the environment.
Overlooking contact type → Power, signal, and data contacts have different current ratings—ensure correct configuration.
By carefully considering these factors, engineers can select the most reliable MIL-DTL-38999 connector for demanding applications, reducing maintenance costs and preventing system failures.
FAQ
- How to Determine Whether You Need a D38999 Pin or Socket?
For most applications, the cable end requires a Pin, while the equipment or panel end uses a Socket. Always match the Keyway orientation to ensure proper connection and avoid miswiring.
- Can Pins and Sockets Be Interchanged in a D38999 Connector?
No. Pins and sockets are not interchangeable. Each is designed for a specific connector end. Attempting to swap them may cause poor contact or connector damage.
- How to Identify Keying Direction and Its Importance?
The Keying (Polarization) code ensures the connector can only mate in the correct orientation, preventing misconnection or short circuits. Do not change the Keyway, as it will make the connector incompatible.
- How to Select the Appropriate D38999 Shell Size and Insert Arrangement?
Choose shell size and insert arrangement based on the number of contacts, current rating, and available space. Refer to standard D38999 insert arrangement charts or manufacturer datasheets for accurate selection.
- What Contact Types and Sizes Does D38999 Support, and What to Consider When Choosing a Replacement?
D38999 connectors support Pin, Socket, coaxial, and fiber contacts in sizes #8, #12, #16, and #20. When selecting a replacement, ensure the series, shell size, Keyway, material, and plating match to maintain connector reliability.
Downloadable Resources
D38999 Catalog (PDF)
D38999 Part Number Datasheet (PDF)
Certificate & Test Report (PDF)
Support and Service
The key to selecting the right D38999 connector is “matching the environment + decoding the correct part number.” By understanding series differences, contact configurations, and equivalent part number cross-references, engineers can identify the most reliable solutions and avoid costly failures caused by incorrect selection. If you encounter any challenges during your selection process, our expert engineering team is ready to provide one-on-one support. We offer tailored services including:
- Technical consultations for your specific applications
- Customized part selection guidance
- Detailed datasheets and catalogues
- 3D models and engineering drawings
- D38999 equivalent part cross-reference
- Free Samples Request
Feel free to contact us or leave a comment, and we’ll help you find the optimal connector solution for your project. Learn more about our military circular connectors MS5015, 26482, D38999.