A "man-in-the-middle" approach for enhancing legacy safety-critical Avionics systems

Legacy Avionics systems, specifically those related to safety-critical functions of an aircraft, usually impose a series of constraints (tight-coupling of the hardware and software system elements, lost knowledge due to dissemination of engineering teams after project end, supplier-locked system documentation, obsolescence of development and enabling systems, etc.) that may hinder or even prevent their adaptation to new use cases or satisfying specific customer needs that were not part of the initial development. While system replacement could seem the obvious solution to these issues, that approach on safety-critical systems with multiple embedded functions imposes a heavy certification risk and may result in an unjustifiable business case due to the unnecessary scope increase. Our research has shown how to enlarge the scope of already-existing Display & Control (D&C) systems in military aircraft by interposing a new complementary system in-between the legacy systems using a man-in-the-middle approach. This new architectural concept [20] just focuses on the added-value control functions, transparently performing data blending from both ends and adapting certain streams of data as required so the end-systems and the final user remain unaware of the intruder. In this way, the certification of the legacy elements that still perform their intended function is not affected, while at the same time we are able to expand the system capabilities, reducing the technical development effort to an acceptable level. We have also shown how the research activities for such an innovative architectural concept continued into the development phase of a new flexible product portfolio that allowed Airbus Defence and Space to offer a new plethora of capabilities to our existing customers, covering their needs within an admissible framework of time, budget and technical performance.