Obsolescence in Aviation Systems of Systems with Applications in ATM

Abstract Systems-of-Systems theory is enlarging the perspective that engineers have on the objects of their work. Previously, efforts were focused at the system level, and by managing system inputs and outputs, all interactions between systems were thought to be addressed. With age, a system-of-systems designed individually at different moments in time will degrade as an overall fitness to purpose, will grow to a certain degree of obsolescence. In aviation this is most evident since systems invented and put in place 60 years ago are still operating. The assumptions made originally when the system was created became obsolete, gradually or in quantum leaps. This paper uses examples from air navigation to illustrate that the fitness for purpose for an individual system does change over time and with the changes in the environment the system is working in. The first time a system is established as an industry standard, its first design, and its first architecture presumably best fit the requirements, the specifications. Although these specifications of the system do not change in time, the fitness to the purpose does change and usually decays. This is only obvious in a systems-of-systems analysis, done for the system now part of a system-of-systems. The paper studies the following cases of obsolescence with impact on Air Traffic Management: Radar Altimeters, ILS Glide Slope intercept from above, Continuous Descent Approach effects on turbine engines, and evolution of SSR transponder utility.