Why MIL-STD-1553 Products Are a Cut Above

Posted in: MIL-STD-1553

You need MIL-STD-1553 connectivity products, but what exactly are they? This blog post breaks it down, explaining what MIL-STD-1553 means, how such products are made differently, and what their chief applications are. Along the way we explain the differences between MIL-STD-1553A, 1553B, and 1553C, and define the key terms “message” and “architecture.” We conclude with a summary of MilesTek’s MIL-STD-1553 products, the vast majority of which you will find in stock and with same-day shipping.

What Is MIL-STD-1553?

MIL-STD-1553, also known as “Military Standard 1553,” is a standard that defines a communication protocol for avionics systems used in military aircraft. It was originally developed by the U.S. Department of Defense in the 1970s and has since become widely adopted in the aerospace industry.

The purpose of MIL-STD-1553 is to establish a reliable, robust, and standardized method of communication between various subsystems and components within an aircraft. It specifies the electrical and data characteristics, as well as the protocol and message format for the exchange of information between different avionics devices, such as sensors, control systems, and displays.

Central bus controller manages flow. The communication protocol of MIL-STD-1553 is based on a dual-redundant bus architecture, where a central bus controller manages the flow of data between multiple remote terminals. The bus operates in a time-division multiplexing manner, where data is transmitted in fixed-length messages called “words.” Each word consists of a synchronization pattern, command or data information, and error-checking bits.

Data integrity ensured. MIL-STD-1553 supports both asynchronous and synchronous data transfer modes, and it provides error detection and correction mechanisms to ensure data integrity. It also defines a set of standardized command and status words that allow devices to request information, issue commands, and report their operational status.

Not just military. While initially designed for military applications, MIL-STD-1553 has found extensive use in commercial aerospace as well. It offers benefits such as deterministic communication, fault tolerance, and the ability to interface with legacy systems.

Differences Between MIL-STD-1553A, 1553B and 1553C

MIL-STD-1553A: This was the initial version of the standard, published in 1973. It defined a 1 Mbps serial data bus with a dual-redundant architecture. Version A specified the electrical characteristics, command format, and protocol for data transmission. It used a 20-bit word format with a 16-bit data field, allowing for up to 31 remote terminals (RTs) on a single bus.

MIL-STD-1553B: This version, published in 1978, introduced significant enhancements and improvements over the previous version. It increased the data rate to 1 Mbps, added more functionality, and refined the protocol. Version B introduced Manchester encoding, which improved the reliability of data transmission. It also expanded the data word to 20 bits, allowing for additional command and status information.

MIL-STD-1553C: The C version, published in 2007, is the most recent and current version of the standard. It maintains the data rate of 1 Mbps but introduces several updates to improve interoperability and performance. Version C introduces changes to the electrical interface and adds support for higher voltage levels. It also incorporates improvements to system testing and verification procedures.

What Is a MIL-STD-1553 Message?

A MIL-STD-1553 message refers to the data structure and format used for communication between devices on a MIL-STD-1553 data bus. The message is composed of various fields that carry information such as command and control data, status information, and payload data. The message format ensures consistent and reliable data exchange between avionics systems.

The key components of a MIL-STD-1553 message are: sync field, command word (CW), status word (SW), data words, parity bits, and end of message (EO).

What Is MIL-STD-1553 Architecture?

The MIL-STD-1553 architecture refers to the overall system design and organization of devices and components that use the MIL-STD-1553 data bus for communication. It defines how the avionics systems and devices are connected and interact with each other − the structure, roles, and interactions of the bus controller, remote terminals, data bus, couplers, and transformers. This standardized architecture enables the integration and communication of avionics systems in military and aerospace applications.

The MIL-STD-1553 architecture follows a dual-redundant design, where two separate data buses (Bus A and Bus B) are used for increased reliability. The bus controller communicates with the remote terminals on both buses simultaneously to ensure redundancy and fault tolerance.

How Are MIL-STD-1553 Cable Assemblies Made Differently?

MIL-STD-1553 cable assemblies are constructed differently from other assemblies to meet the requirements of the MIL-STD-1553 communication protocol and the demanding conditions of avionics and aerospace applications. Here are some differentiators:

  • Electrical Characteristics: MIL-STD-1553 cable assemblies are designed to meet specific electrical characteristics defined by the standard. This includes impedance, capacitance, and signal attenuation requirements to ensure reliable signal transmission and to minimize data errors. The cables maintain consistent electrical performance across their length.
  • Dual Redundancy: MIL-STD-1553 employs a dual-redundant bus architecture, meaning it uses two sets of cables for communication. Such cable assemblies include both the primary and secondary buses to provide redundancy. The cables are often color-coded or marked to identify their specific roles.
  • Shielding and Protection: Due to the critical nature of avionics systems, MIL-STD-1553 cable assemblies feature robust shielding to protect against electromagnetic interference (EMI) and radio frequency interference (RFI). The shielding helps maintain signal integrity and prevents data corruption. The cables may also have additional protective layers to withstand harsh environments, such as temperature extremes, moisture, and vibrations.
  • Connectors and Contacts: MIL-STD-1553 cable assemblies use specific connectors and contacts that comply with the standard. These connectors are designed for secure and reliable connections and are often keyed to prevent incorrect mating. The contacts are typically gold-plated to ensure low contact resistance, corrosion resistance, and long-term reliability.
  • Data Bus Couplers: In MIL-STD-1553 systems, data bus couplers are sometimes used to tap into the communication bus for testing or monitoring purposes. These couplers are integrated into the cable assemblies and allow for non-intrusive access to the data bus while maintaining the integrity of the communication.
  • Compliance and Certification: MIL-STD-1553 cable assemblies may undergo rigorous testing and certification processes to ensure compliance with the standard. This includes testing for electrical characteristics, mechanical integrity, EMI/RFI shielding effectiveness, and environmental performance.

What Industries Use MIL-STD-1553 Connectivity?

MIL-STD-1553 connectivity products are primarily used in industries that require the most reliable and ruggedized communication systems for avionics and aerospace applications. Here are some industries where these components find use:

  • Aerospace and Defense: MIL-STD-1553 is widely employed in military and defense aircraft, including fighter jets, transport planes, helicopters, and unmanned aerial vehicles (UAVs). It ensures efficient communication between various avionics subsystems, such as flight controls, navigation systems, weapon systems, and communication systems.
  • Space Exploration: MIL-STD-1553 is also used in space missions for both military and civilian purposes. It provides a reliable means of communication between spacecraft components, satellites, and ground stations. This standard has been used in missions conducted by organizations like NASA and international space agencies.
  • Commercial Aviation: While newer avionics systems in commercial aircraft often use more advanced communication protocols, MIL-STD-1553 is still found in some older aircraft or specific subsystems within newer planes. It allows for compatibility with legacy systems and supports the integration of new equipment with existing infrastructure.
  • Automotive and Transportation: In certain specialized applications within the automotive and transportation industries, such as military vehicles, armored vehicles, and specialized ground vehicles, MIL-STD-1553 can be employed for data communication between different vehicle systems and components.

MilesTek’s MIL-STD-1553 Product Lines

For over 40 years, MilesTek has been expanding its array of MIL-STD-1553 products. Below we provide links to all 12 of our product categories and summarize the main features of four of them.

If you don’t find exactly what you need, please know we accommodate special requests, small- and large-volume production runs, and custom designs through our Cable Assembly Wizard and our Adapter Wizard. Also keep in mind that we offer quick RFQ responses and rapid production timelines.

Four of our biggest product categories:

MIL-STD-1553 Bus and Stub Cable Assemblies

MilesTek offers a complete range of MIL-STD-1553 cable assemblies for data bus applications. We engineer and build them with standard or high-temperature twinaxial cable, plugs that are standard or right-angle and solder/clamp or full-crimp, and with or without bend relief. We also stock bus and scope test cables. Check out our shopping primer for data bus cable assemblies.

MIL-STD-1553 Data Bus Couplers

MilesTek carries the most complete line of data bus couplers for MIL-STD 1553 applications, including box-style and in-line coupler designs. Configurations include box-style couplers with up to eight stubs, inline couplers with up to four stubs, and bus coupler kits. See our blog post on bus coupler considerations.

MIL-STD-1553 Adapters

MilesTek TRB adapters allow you to couple two cable assemblies, convert a male connection into a female or vice versa, and send one input to two outputs or two inputs to one output. The TRB bayonet design withstands severe shocks and vibrations.

MIL-STD-1553 Connectors

We offer both three-slot and two-slot concentric bayonet twinaxial TRB connectors. Bayonet mounts hold more tightly than threaded mounts and are easier to attach, especially when you’re working in a small space. Other connector features we offer include bend relief, bulkhead jacks, front mount and rear mount. See our blog on MIL-STD-1553 connectors.

Our Other MIL-STD-1553 Product Categories

To see all of our MIL-STD-1553 product categories, click here. For help on choosing what product is best for you, contact the MilesTek sales team at 1-877-924-1134 or via email at sales@milestek.com. And don’t forget that almost all our products are in stock and ready to ship today.

June 20, 2023