PCOTS versus LRU: COTS moving up the integration food chain

The COTS proposition, taking state-of-the-art commercial semiconductor technology and deploying it on open-standard military board architectures, is rapidly migrating up the technology food chain to the preconfigured subsystem level. Packaged COTS () subsystems are being driven by customer interest in reducing design risk and time to market, leading them to turn to traditional board vendors who have expertise in packaging and thermal management. PCOTS fully integrated “standard” systems enable development cost and improvements to be distributed over multiple users and programs, which drives increases in performance and economies of scale. There is also a place for both Line Replaceable Units (LRUs) as individual modules and packaged subsystems based on LRUs.

The packaged COTS advantage

In addition to ensured interoperability of the boards and mezzanine cards that populate their system, the PCOTS approach significantly simplifies system development by reducing vendor interaction to a “one-stop shop” – easing the pain that can occur when multiple third-party vendors are depended upon. The reality is that almost all deployed systems will require some unique modification. While vendors are able to offer a comprehensive range of proven, qualified systems that match most of a customer’s requirements, Non Recurring Engineering (NRE) will be needed to get to the completed system. But the advantage for the customer is fast turnaround on a deployable system from an integrator who is using a common set of familiar building blocks and proven IP. PCOTS also frees the customer from the time and cost of dedicating a hardware integration team, enabling them instead to focus on the software, where true uniqueness and their value-add typically resides.

This is not to say that PCOTS is a panacea. When making this decision, customers considering PCOTS need to calculate the size of the NRE against their true overall development costs including salaries, operational costs, and so on. For example, test house costs included in a (CWCEC) PCOTS project typically provide an engineer onsite for the duration of testing, and include production of the test procedures, test equipment, and test reports.

Benefits of the LRU approach

There are clear cases where it is preferable for the customer to stay with the traditional LRU acquisition approach, spec’ing and acquiring the range of needed boards and mezzanine cards from one or more vendors and handling the integration themselves. These cases include situations in which the customer’s application demands a high level of programmatic, for example, requiring a dedicated team who must produce earned value reporting every month during a multiple-year time period.

Another case in which the advantages of LRUs outweigh PCOTS is when the application software demands a high level of custom hardware development. If the needed system cannot be built efficiently from a Size, Weight, Power, and Cost (SWaP-C) perspective using COTS components and packaged in a “COTS wrapper,” then the PCOTS approach will typically not be a good fit.

The PCOTS trend on the rise

At CWCEC we are seeing increased interest from major defense contractor customers who need a PCOTS system to help them meet the challenge of increasing their card counts in space- and weight-limited ground, air, and sea vehicle environments – rather than reinvent the wheel or expend their engineering resources on packaging problems.

To get a standard PCOTS offering to meet a customer’s unique application can require such modifications as custom front-panel pinouts (made simpler through a high level of modularity), and custom backplanes. One notable area of growth is the use of Air Flow Through (AFT) cooling. As interest in 6U AFT, defined by .5, is increasing in the embedded defense and aerospace market, we are seeing a rise in the number of customers considering it. Figure 1 shows examples of CWCEC’s avionics and vetronics PCOTS rugged systems developed from COTS components and tailored to specific customer requirements.

Moreover, as defense and aerospace customers discover the advantages of PCOTS – cutting schedule and performance risk while reducing their costs – the benefits of COTS will increasingly be associated not just with off-the-shelf modules but with fully integrated systems, too.

Figure 1: Avionics and vetronics PCOTS rugged systems developed from COTS components from Curtiss-Wright Controls Embedded Computing
(Click graphic to zoom by 1.9x)

To learn more, e-mail Steve at Steve.Edwards@curtisswright.com.