Prognostics and health management for improved dispatchability of integrated modular avionics equipped aircraft

Integrated modular avionics (IMA) is being suggested as the means by which new capabilities can be deployed on aircraft at an affordable cost. RTCA SC-200 is presently considering the guidance document for IMA. All of the functionality that IMA offers can be achieved through a conventional federated architecture; however, the cost, size and weight penalties of the federated solution make it uneconomic. IMA is seen as the way forward. It is assuming greater importance as the aircraft industry transitions to commercial off-the-shelf (COTS) technology with its attendant obsolescence and reliability concerns. IMA may be one of the most cost-effective ways by which rapid obsolescence can be managed. Ironically, this move to COTS is also the greatest threat to IMA systems. IMA achieves reductions in size, cost and weight by providing a set of flexible hardware and software resources that can be statically or dynamically mapped to a set of required avionics functional capabilities. This introduces a number of new complexities such as mixed criticalities and reconfiguration. We do not address these issues here. Rather, we discuss the mechanisms by which electronics degrades and how a classical safety assessment of a reconfigurable IMA system can be nullified by this degradation. We argue that with the advent of COTS, it is no longer justifiable to consider that electronics has an effectively constant failure rate. Physical considerations suggest that electronics failure occurs when environmental and operating stress causes the accumulation of damage to the underlying structures to exceed the threshold strength of the constituent materials and interfaces. Finally, we suggest how finite-life electronics effects may be mitigated.