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Problem Statement

The SESAR concept of operations beyond 2020 (SESAR2020+) involves a series of changes relative to the current ATM situation. Central to these changes is the paradigm shift that aircraft should fly according to agreed conflict free 4D trajectory plans which are made known to all actors involved as Reference Business Trajectories (RBT’s). The big unknown in this RBT framework is how everything works under various kinds of uncertainties, as a result of which one or more aircraft may not realize their RBT’s. There are several categories of uncertainties (including unexpected disturbances) that cannot be totally avoided, such as:
• Meteorological uncertainties;
• Data related uncertainties;
• Human related uncertainties;
• Technical systems related uncertainties.

In principle the SESAR2020+ ConOps has been designed to take care of these kinds of uncertainties through the possibility to revise 4D trajectory plans, and also to allow air traffic control to issue tactical flight instructions to pilots if the 4D planning layer has ran out of time. Although these tactical instructions are quite similar to the established way of working by an air traffic controller, there also are significant differences.

Under SESAR2020+ an air traffic controller is expected to handle significantly more aircraft in its sector. Therefore the SESAR2020+ ConOps also foresees dedicated tactical decision support tools for air traffic controllers. The key issue is how to optimize the socio-technical collaboration between the 4D planning layer and the tactical layer in order to manage air traffic most effectively while taking into account the various uncertainties.

In conventional ATM, medium term planning is provided by the planning controller, flight crews and their Flight Management Systems (FMS), whereas the tactical loop is formed by the tactical controller and flight crews. Thanks to decades of evolutionary developments, the collaboration between these two layers has been optimized. For SESAR2020+ a similar optimization of the novel 4D planning layer with the tactical layer is needed. Because the collaboration between these layers involves dynamic interactions between human decision makers, technical support systems, aircraft evolution, weather and other uncertainties, the combined effects result in types of emergent behaviours that cannot be predicted from the sum of the elemental behaviours. This can easily lead to negative emergent behaviours at time scales that remain invisible using established evaluation techniques.