How to Choose MIL-SPEC Connectors for Avionic Applications

While connectors may appear to be relatively inconsequential components, those used in military aircraft must meet uncompromising performance standards. These items enable the stable transmission of power, data, and signals between critical systems, making a significant impact on an aircraft’s performance and safety. With this said, it is essential for anyone involved in military and defense operations to know how to choose the appropriate Military Specification (MIL-SPEC) connectors. In this blog, we will cover everything you need to know about MIL-SPEC connectors, from the standards governing their design to which popular types are best suited for military aviation.

Understanding MIL-SPEC Standards

Generally, MIL-SPEC parts are engineered to meet strict performance standards set by the United States Department of Defense (DoD), validating that they can operate under the intense vibration, temperature fluctuations, exposure to moisture or corrosive fluids, electromagnetic interference (EMI), and mechanical stressors typical of military environments. The Defense Logistics Agency (DLA) oversees the development and enforcement of these specifications to promote compatibility and quality consistency across all branches of the U.S. military.

For avionic connectors specifically, standards such as MIL-DTL-38999, MIL-DTL-26482, and MIL-DTL-5015 provide detailed guidelines regarding materials, performance, and environmental sealing. These standards are focused primarily on circular connectors, which are favored in aerospace for their compact build, secure coupling, and ability to support multiple contact configurations. Keeping these various specifications in mind will help ensure that selected components will align with the integration requirements of military aircraft.

Notable MIL-SPEC Connector Types for Avionics

MIL-DTL-38999 Series

The MIL-DTL-38999 series is among the most regularly implemented circular connector standards for military aviation due to their high-density contact arrangements, compact size, and excellent resistance to harsh environmental conditions. These connectors have current capacities ranging up to 23A per contact depending on the size, while their voltage ratings are around 500V RMS. Moreover, they are compatible with a varied range of signal types when equipped with the appropriate insert configurations.

Key Features

• This series is divided into four variants (I, II, III, and IV), each optimized for specific coupling methods such as bayonet, breech-lock, or threaded engagement. They are also available with different insert arrangements to suit diverse contact types.
• All MIL-DTL-38999 connectors provide built-in EMI shielding and corrosion resistance for long-term durability. EMI shielding is achieved through conductive plating, shell-to-shell grounding, and rear accessories like backshells and shielding clamps.
• Most connectors in this series are constructed using lightweight aluminum or composite shells to minimize weight.

Typical Uses

• Flight control systems
• Engine instrumentation
• Avionics data interfaces

MIL-DTL-26482 Series

MIL-DTL-26482 connectors are another common choice for aerospace employment, particularly where moderate ruggedness and ease of use are sought out. These connectors primarily offer low- to mid-power electrical signal transmission and are compatible with both AC and DC circuits. Depending on the contact size, current ratings can reach up to 13A, with voltage ratings landing around 1000V RMS. Although they offer less EMI shielding and mechanical strength compared to the 38999 series, they are an economical solution for secondary or non-critical avionic systems.

Key Features

• These connectors use a bayonet-style locking mechanism for fast and secure mating with minimal effort.
• MIL-DTL-26482 connectors offer resistance to moderate levels of vibration and moisture infiltration, this being supported by rubber grommets and interfacial seals.
• Their shell sizes range from 8 to 24, as well as support many contact arrangements for flexible system design.
• Limited EMI protection is achievable through aluminum shells and conductive finishes.

Typical Uses

• Cabin electronic systems
• Navigation interfaces
• Auxiliary power connections

MIL-DTL-5015 Series

The MIL-DTL-5015 series is designed for high-power applications that require durable electrical interfaces. These circular connectors handle significantly high currents, often up to 150A determined by their contact configuration, whereas their voltage ratings reach 1250V RMS. Additionally, they accommodate both AC and DC power transmission.

Key Features

• These connectors are capable of operating across a broad temperature range, usually between -67 to 257°F.
• Their threaded coupling ensures robust mating under stressors and supports approximately 500 mating cycles.
• With steel and aluminum alloy shells, MIL-DTL-5015 connectors provide superior strength and environmental protection.
• Their EMI shielding can be enhanced through the use of conductive gaskets and shielded backshells when specified in the connector’s configuration, as these additions are optional and application-dependent.

Typical Uses

• Power distribution in radar systems
• Actuation systems in landing gear
• Weapon system interfaces

MIL-DTL-83513 (Micro-D Connectors)

Most MIL-SPEC connectors used in avionics are circular, but the MIL-DTL-83513 series represents a widely adopted rectangular option. Commonly referred to as Micro-D connectors, these have a compact form to support high-density layouts in limited-space environments, with signal integrity maintained across their closely spaced contacts. Furthermore, micro-D connectors can optimally carry low-voltage analog and digital signals, being rated for currents up to 3A per contact.

Key Features

• MIL-DTL-83513 connectors provide high contact reliability through precision-machined contacts.
• Their latching mechanisms ensure secure mating while allowing for quick disconnection when needed, with screw-lock versions providing additional security in critical systems.
• EMI shielding and environmental sealing can be incorporated in these connectors to meet specific system requirements, with shielded variants using metal hoods and braided cable shields terminated through backshells.

Typical Uses

• Miniaturized avionic control modules
• Data links in unmanned aerial vehicles (UAVs)
• Internal avionics subsystems that aim to have space-saving configurations

Obtain Trustworthy MIL-SPEC Electrical Connectors on Aviation Sourcing Solutions

As illustrated, it is imperative to select MIL-SPEC connectors that conform with the demands of the application at hand. However, it is just as important to get them from dependable and certified sources. Aviation Sourcing Solutions, an ASAP Semiconductor-operated platform, provides a vast selection of military-grade and other industry compliant components for your connector needs and beyond.

Every item available through Aviation Sourcing Solutions is meticulously sourced from reputable manufacturers and suppliers, and many products undergo quality assurance checks prior to shipment. This, combined with our competitive pricing options, fast lead times, curated solutions, and exceptional service, means you can always anticipate a seamless procurement experience. With such commitments in mind, be sure to check out our inventory and get in touch with our experts so we can serve you with advantageous procurement options.