The strong interaction between the discrete dynamic and the one continue is now seriously taken into account in the model. These models newborn so-called hybrid models describe at one time the two dynamics and are already used as well in control systems as in analysis. The methods and present tools of the dependability of systems are either of quantitative order or qualitative one. The avenue of the hybrid models obliges the scientific community to compose with this new modelling. The scientific objective of the present article is the presentation of a methodology of research on diagnosis of the hybrid dynamic systems. These are modellised by linear hybrid automatons. The analysis of reachability of the states described by these automatons is it a means of the dependability in the hybrid dynamic systems?.
