Safety assessment for an ATM system change: a methodology for the ANSPs

Air Traffic Management (ATM) is a continuously evolving process, where many current system elements derive from a time when ATM characteristics were very different from today. Nowadays, the provision of ATM services has to design new solutions and adapt to new scenarios. Although ESARR 4 and EU Regulation 1035/2011 define the need of evaluating ATM system risks before implementing any change, they do not define a practical tool to support the decision-makers. The aim of this paper is to fill this gap, proposing a systematic methodology; the Preliminary System Safety Assessment Tool (PSSA-T) capable of helping the decision makers in evaluating safety implications due to system changes. PSSA- T relies on the definition of two Indexes, which have been built according to the Aerospace Performance Factor (APF) methodology, and allow safety assessment of any proposed change. In detail, the former Index compares the evolutionary scenario with the current one and the latter evaluates the evolutionary scenario in which there is a failure of intervention, in the hypothesis the system change has been implemented already. A preliminary study about the change from Flight Progress Strip (FPS) to the Electronic-FPS clarifies the outcome of the study