Connectors for operational success in military & aerospace applications

Author : Emily Rowe & John Skinner | European Product Managers | PEI-Genesis

01 February 2022

PEI Genesis_Connectors for operational success in military & aerospace applications_ship
PEI Genesis_Connectors for operational success in military & aerospace applications_ship

In challenging applications like military & commercial transportation, electrical failure can be costly. Engineers working in these environments rely on robust & reliable electrical equipment to ensure successful operational outcomes. And whether they’re used in commercial aircraft or onboard military vehicles, not many electrical components are subjected to extreme conditions in the same way connectors are.

This article was originally featured in the February 2022 issue of EPDT magazine [read the digital issue]. And sign up to receive your own copy each month.

Here, European Product Managers at mission critical electrical connector specialist, PEI-Genesis, Emily Rowe & John Skinner respectively discuss the benefits of using D38999 connectors in these applications, before explaining how reverse bayonets gained their stellar reputation as reliable and robust connectors for challenging applications…

Connectors, particularly those used in aerospace and military applications, must endure extreme conditions. Often subjected to rapid temperature variations or persistent vibrations, impacts and signal interference, they need to be robust enough to continue operating reliably and safely under these conditions to ensure users can have 100% trust that the product will get the job done.

Take the industry standard D38999 connector. This military-specification electrical connector was originally designed in the 1970s and is now on its third-generation design. The main reason the D38999 connector soared to popularity is that it offers a far higher density of contacts than its predecessors – 128 contacts compared to only 19 for 5015 connectors.

Like similar connectors, it’s comprised of a few basic components: a hard outer shell; a neoprene rubber insert with holes to house the pins or contacts; and sometimes a backshell on the outer housing that provides additional shielding and durability. However, one benefit of D38999 connectors is the wide variety of customisation options it can offer, including different shell types, materials, finish and insert arrangements. This makes them appealing to more customers – particularly those in industries that often require a bespoke solution, such as the military & aerospace sectors.

Meeting industry needs

In military applications, there are increasing needs for shielding and durability, with electrical connectors expected to be in service for up to 20 years. This is another area where D38999 connectors shine. With lifespans between 500 and 1,500 mating cycles, they can last for up to 30 years, depending on the application.

Many customers from aerospace and military industries require custom components for their applications, and D38999 connectors facilitate this, since their backshells and contacts are easily customisable. For example, backshells can be supplied in aluminium, stainless steel or composite materials, depending on the requirements. Newer composite options are growing in popularity, because they are lightweight, offer high performance levels in harsh environments, and are also REACH-compliant and QPL-qualified for use in military applications.

The customisation options available with D38999 connectors is also causing them to grow in popularity in other industries where they were not widely used before, such as industrial, marine and automotive.

For every new application where these connectors are used, customisations can help make it robust and reliable for that industry. Meanwhile, a reliable connector supplier can provide guidance on the best solution available to you. PEI-Genesis provides an extensive range of D38999 connectors from Amphenol, ITT Cannon, TE Deutsch, Souriau Eaton and Conesys. Not only that, but it also stocks large volumes of component parts and is able to build millions of connector types, with lead times of 48 hours. Furthermore, it can offer standard solutions or work with customers to create bespoke designs using its in-house team of design engineers. In addition, it supplies a wide range of accessories for D38999 connectors, such as protective caps, backshells, contacts, nut plates for receptacles and tooling.

PEI Genesis_Connectors for operational success in military & aerospace applications_plane
PEI Genesis_Connectors for operational success in military & aerospace applications_plane

Reverse bayonet connectors

Reverse bayonet connectors are often used in military and commercial transportation, as well as industrial applications, because of their relatively low cost and highly reliable design. Where intense vibrations are common for connectors used in these industries, operators need assurance that they can withstand any challenge. So, what is it about reverse bayonets that make them a connector of choice in these industries?

Rapid mating & unmating

Any coupling and decoupling system needs to be simple and efficient and must provide excellent resistance to shock, vibration and environmental contaminants to ensure the continued performance of the connector.

Originally designed for NATO combat vehicles, reverse bayonet connectors simply need a 120° turn to mate, enabling quick and easy mating and unmating. Their design also allows users to confirm mating in three different ways: tactile, audible and visual. The user feels the connector lock into position when mated, and a loud click is heard as the three studs snap into place when the coupling nut is fully engaged. Additionally, a coloured triangle on the receptacle aligns with a dot on the coupling nut when the connector is properly mated. These simple design features ensure users can be confident the connector is mated, and significantly reduce the risk of accidental de-coupling. This is critical because if, for example, reverse bayonets are being used in the communications equipment of a military vehicle, accidental decoupling because of user error or excessive vibration could negatively impact safety.

O-ring, wave spring & washer

Reverse bayonet connectors come with either an O-ring and/or a wave spring and washer. Wave springs are specified in VG95234 and rail-specific reverse bayonets, while O-Rings are used in commercial variants. These components provide resistance when the user connects the plug to the receptacle and twists the coupling nut. The resistance gives a positive mating and prevents vibrations from making the connector loose. O-rings also ensure IP67 protection when connectors are mated.

Standard reverse bayonet connectors have mating cycles of 500 times without any decrease in performance. However, some ranges feature a wear pin on the receptacle, which increases mating cycles to 2000 times. Not only is it better value for money to increase the lifecycle of a connector, but operators are also guaranteed high performance for longer.

Resilient & versatile

Above all else in harsh environments, resilience and versatility are vital. Reverse bayonet connectors offer reliable performance over a temperature range of -55 to +125 degrees Celsius, as well excellent shock resistance and IP67 protection when mated.

To achieve this, reverse bayonet connectors use insulators and grommets made from chloroprene. This synthetic rubber is extremely durable, and is a good electrical insulator. This is vital in commercial transportation, military and industrial settings, where varying temperatures and exposure to environmental contaminates are common. For some rail applications, specialised ‘low-smoke’ inserts are used that comply with rail industry flammability standards.

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