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The Non-Military User's Guide to Military Connectors

The military is responsible for so many inventions that we take for granted today. The microwave oven, canned food and duct tape (or duck tape if you prefer) are all products of the defence industry.

Connectors were not a military invention, but the defence and aerospace industries were quick to embrace connector technology. This really took off (no pun intended) with the explosion in commercial air travel in the early part of the 20th century. The world-famous Douglas DC-3 used a circular connector called the AF from US manufacturer Cannon. As the dark clouds of conflict gathered in the late 1930s, there was a huge growth in military development.

Adopting a Standard

One of the outcomes of this growth was the idea of standardized patterns. By creating and imposing a standard design, a product could be manufactured in almost any location, safe in the knowledge that it would be compatible with an equivalent item made elsewhere. This legacy remains with us today in the form of military standards, more often known as Mil-Specs.

Nowhere is this truer than in the connector industry, possibly because connectors are the interface between systems and equipment.  Military platforms such as aircraft or ships are assembled from a huge range of sub-systems, all manufactured by different companies.  Using a mil-spec to define the connector interface ensures that the final assembly will be straightforward.

However, the extensive use of connectors in a wide variety of situations means that there is now a bewildering array of mil-specs to choose from. For customers not used to the specification numbers, acronyms and jargon, it can all be a little confusing. In these articles, we’ll try to make the world of mil-spec connectors a little less scary.

Getting To Know Your Military Connectors

Military connectors fall into a number of categories. The first group is made up of connectors that were not originally designed for military use, but have found widespread use in defence applications.  Possibly the best-known example of this is the humble D-subminiature connector.  Developed in the 1950s, the D-sub found many customers in the military industry as it offered a real alternative to the bulky circular connectors that had dominated the market for the previous two decades. 

The slim profile of the D-sub, combined with a high contact count, made it particularly attractive as the new generation of aircraft and electronics were being developed at the height of the cold war.  As a result, the D-sub connector was awarded its own military standard in the USA, called MIL-C-24308, often shortened to M24308. The D-sub has been continuously developed since its introduction, and the M24308 standard has been updated as new features were added, making it as relevant today as it was six decades ago.

In contrast, the next group of connectors were specifically developed with a military application in mind.  As an example, the MIL-C-38999 (shortened to D38999) connector was released in the early 1970s. At that time, the 4th generation of combat aircraft was in development.  Aircraft like the F-16 Fighting Falcon in the US and the Mirage 2000 in Europe were introducing new developments, from Head-Up Displays (HUD) to Fly-by-Wire (FBW) flight controls. 

Evolving Military Applications: the Dassault Mirage 2000. Image: Airliners.net/Fred Willemsen

The amount of data processed by these new systems required a new generation of connectors, with more contacts packed into smaller spaces. The D38999, and others like it, were developed to provide solutions for these challenges. The D38999 has been one of the most successful connectors of the last few decades. It has expanded its role from a purely airborne solution to encompass all areas of industry and is available in different styles and materials for use in harsh conditions

There is even a group of connectors that were designed as military connectors, but have since passed into industrial use. The MIL-C-5015 connector has been around for well over 70 years.  Although it is obsolete for use in current military systems, it is very popular in industrial equipment.  Known under many names, the “fifty-fifteen” is still offered by several manufacturers.

Why Mil-Spec?

What is it that non-military users find so attractive in military connectors? There are many reasons, but some of the most important are:

  • Availability:  This one is simple. If a standardized product is available from several different sources, it should be easier to find.  Industrial users are free from so-called “single-source” products, giving them logistical and financial benefits.
  • Robustness:  Military connectors are designed to work in challenging conditions.  Whether it is the heat of the tropics or the cold of the arctic, military equipment must work in some of the toughest environments on Earth. This makes them ideally suited for use in industrial applications that might experience similar conditions. From the battlefield to the mining industry, or field signals equipment to outside broadcast trucks, there is a mil-spec connector that will solve an industrial problem.

Mining - Tougher than the battlefield? Image: Power Hydraulik

  • Familiarity:  By designing connectors to a common standard, the manufacturers have created a range of products that are used by thousands of users worldwide. This means that there is a huge group of people who have practical experience in the installation and operation of these connectors. This has benefits ranging from operator training to the availability of tooling, all of which make the adoption of these connectors easier for the industrial customer.

To Be Continued…

Hopefully, the benefits of using military specification connectors in industrial applications are a little clearer.  In the next part of this article, we’ll take a look at the anatomy of military connectors and try to understand the details that make them useful for industrial customers.  We’ll try to give you some tips and hints, and we might even be able to bust a myth or two.  Tune in next time…

Read Part 2 now.

Connector Geek is Dave in real life. With 29 years in the industry, Dave still likes talking about connectors almost as much as being a Dad to his two kids. He still loves Lego too...

28 Apr 2020, 8:16