Hierarchical Modelling of the Impact of Obsolescence on System Availability

Technological advances, changing needs and market dynamics generate a multitude of obsolescence issues in almost all sectors of activity. This represents serious challenges for companies, particularly in terms of quality, availability and maintainability. These challenges are particularly acute for complex systems with a long lifespan such as trains or planes, which must maintain acceptable levels of performance for many years. The obsolescence of components, documentation, tools and personnel skills are all industrial risks that must be controlled. In this context, this research presents models to represent the impact of obsolescence on the availability of complex systems. The objective is to show the mechanisms of these impacts. These models, built using Petri nets, then make it possible to estimate the possible degradation of availability following the occurrence of obsolescence, an aspect not addressed in this article. The modelling is based on a principle of classifying components into four classes, allowing to model the multilevel architecture of a system. By associating a set of Petri models with each class, and by synchronising the models between them, the impact of obsolescence on availability is clearly described. The article ends with a number of conclusions and in particular with a presentation of the research carried out to predict the availability of systems in the presence of obsolescence of components, documentation, personnel or tools.