MIL-DTL-38999 connectors are the most widely used military circular connectors in aerospace and defense. Engineered for high-density performance in extreme conditions, they support the mission-critical power, signal, and RF requirements found across modern platforms.
For OEMs, integrators, and program teams, these connectors deliver long-term reliability, rugged construction, and standardized performance. When those connectors must be integrated into a fully validated harness or cable assembly, XACT provides AS9100-certified builds manufactured for the environments defense and aerospace systems face every day.
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Why MIL-DTL-38999 Connectors Dominate Defense & Aerospace
MIL-DTL-38999 connectors are built for the demanding conditions where commercial connectors fail. Key advantages include:
High-Density Performance
38999 connectors deliver exceptional contact density for their footprint and can support mixed-signal applications: power, low-voltage signal, RF, coax, twinax, and triax.
Environmental and Mechanical Ruggedness
Designed to resist vibration, shock, dust, fluid ingress, corrosion, and thermal extremes, these connectors maintain reliable performance under continuous operational stress.
Electrical Integrity and EMI Protection
38999 connectors support stable ground paths and effective EMI/RFI shielding—critical for avionics, mission systems, radar, C4ISR electronics, and high-speed digital equipment.
Long-Term Mil-Spec Stability
With decades of program adoption and specification control, MIL-DTL-38999 provides a dependable base for long lifecycle defense platforms.
The Four MIL-DTL-38999 Series
MIL-DTL-38999 connectors are available in four series, each suited for different design priorities.
Series I – Bayonet Coupling
- Fast mating/unmating
- Scoop-proof interface
- Excellent for equipment that requires rapid service access
Series II – Low-Profile Bayonet
- Minimal weight and footprint
- Used in space-constrained avionics and electronics bays
Series III – Tri-Start Threaded
- Industry’s most common variant
- Superior environmental sealing and vibration performance
- Widely used in aerospace, ground vehicles, naval systems, and ISR payloads
Series IV – Breech-Lock
- Ideal for blind-mate applications
- Excellent mechanical retention in tight-access assemblies
Where MIL-DTL-38999 Connectors Are Used
38999 connectors support mission-critical systems across:
- Military aircraft (avionics, engines, flight controls)
- UAVs, UAS, and ISR sensors
- Ground vehicles and vetronics
- C4ISR and tactical communications systems
- Naval combat and shipboard electronics
- Missile and ordnance guidance systems
- Harsh-environment industrial applications
- Space and high-altitude electronics
Where performance under duress is required, MIL-DTL-38999 remains the connector of choice.
XACT’s Military Grade Cable Assemblies and EMI/Thermal Materials
Why Engineering Teams Choose XACT for MIL-DTL-38999 Assemblies
XACT manufactures rugged, reliable MIL-DTL-38999 cable assemblies engineered for harsh military and aerospace environments.
AS9100-Certified Manufacturing
All assemblies are produced under aerospace-grade controls with documented workmanship standards.
Overmolding & Environmental Sealing
Custom overmolds, backshell integration, and strain-relief solutions support durability against:
- Vibration
- Shock
- Fluid exposure
- Mechanical stress
- Repeated mating cycles
EMI/RFI Shield Terminations
XACT provides 360° shield termination capability for power, signal, coax, twinax, and triax harnesses—critical for EMI-sensitive avionics and mission systems.
Full Electrical & Mechanical Testing
Testing capabilities include:
- Continuity
- Insulation resistance
- Hi-Pot
- Pull strength
- Flex/bend testing
Traceability & Documentation
XACT provides fully traceable builds with QA documentation, including lot-level controls aligned with aerospace and defense requirements.
Repair & Recertification Services
XACT can restore MIL-DTL-38999 cable assemblies—even those originally built by another supplier.
FAQ: Testing and Reliability at XACT EMS
How do MIL-DTL-38999 part numbers work?
A typical mil-spec part number looks like:
D38999/26WG11SN
Each segment specifies the connector style, finish, shell size, insert arrangement, contact type, and keying orientation. This structured format ensures compatibility across platforms and suppliers.
What are common MIL-DTL-38999 part numbers?
Common examples include:
- D38999/20WA35PN
- D38999/26WB98SN
- D38999/24ZC04PN
- D38999/26FG16SN
- D38999/46HB35PN
These numbers follow standard mil-spec formatting used throughout defense and aerospace.
What shell sizes are most commonly used?
Typical shell sizes include:
9, 11, 13, 15, 17, 19, 21, 23, 25
What insert arrangements are typical?
Common arrangements include:
11-35, 13-98, 15-05, 17-06, 19-32, 21-75, 23-53, 25-37, 25-61
What contact types are supported?
38999 connectors can be used with:
- Crimp contacts
- Solder contacts
- Coax
- Twinax
- Triax
Can XACT repair or recertify existing assemblies?
Yes. XACT offers restore-to-spec services including inspection, re-termination, overmold replacement, and updated documentation.
Which industries rely most on MIL-DTL-38999 connectors?
Defense, aerospace, UAVs, naval systems, rugged industrial automation, and space applications.
