COTS devices find their way into long-life, high-reliability military applications

Use of commercial off-the-shelf (COTS) components in military and aerospace applications is an accepted fact. The move encompasses not just individual components, but sometimes entire subassemblies based on COTS devices. As a result, military and aerospace grades have shrunk from 9% of the overall electronics market in 1984, to just 0.9% in 2005. COTS is here to stay.

The impact of this change is already evident, particularly in terms of obsolescence. Projects with development phases that last up to 20 years and in-service lifetimes of 40 years are being built using components with life cycles measured in months. The scale of the problem is illustrated by recent estimates suggesting that electronic components are now being obsoleted at a rate of over 13,000 per month.

The effects in terms of reliability, whilst equally important, are less clear at this point. That's simply because insufficient in-service data exists to assess real failure rates and lifetimes.

Against this background, it remains imperative that military and aerospace engineers ensure the reliability, safety integrity, and lifetime of their designs. In particular, whole-life component management planning is essential to ensure adequate supplies of fit-for-purpose components and subassemblies throughout the CADMID (concept, assessment, development, manufacture, in-service, disposal) cycle.

A whole-life component management plan has three overarching goals. The first is to ensure that COTS parts selected can satisfy the performance requirements of the military and aerospace environment. This might be in terms of rad-hardness, resistance to shock and vibration, or temperature range; and it means not just "survival," but also remaining fit-for-purpose under any conditions.

This front-end process impacts design, as much as procurement and testing. For example, programmable logic and memory are both following a trend of shrinking device geometry, bringing higher capacity and lower supply voltages as time goes by. The designer should be planning for this development to allow for technology insertion during subsequent design and production phases.

The second aim is to ensure continuity of component supply (and, in the end, security of production and maintenance). In practice this means implementing many of the obsolescence management best practices that have become established in recent years. Given the need to provide decades of product life with components whose life cycles run into months, this may include strategies such as advance procurement and long-term storage of components.

Finally, the plan needs to compensate for the lack of provenance of COTS parts. Unlike MIL SPEC components, COTS devices don't come with a certificate of conformity. There's no guarantee that, from batch to batch, components will be manufactured or assembled in the same facility, let alone with the same process. This requires a rigorous testing and inspection regime.

The whole-life plan commences at the concept phase with an evaluation of failure methods in current components, a process that extends well into the assessment stage. This establishes base criteria for the performance of available devices and can be structured into a formal quality criteria plan for the components.