Air traffic functions in the NextGen and SESAR airspace

The air traffic system enabled by NextGen and SESAR will allow functions to be executed by the most appropriate element given the strategic and tactical situation rather than limited to the existing roles predicated on 1960´s technology and procedures. The current allocation of functions is based on historical technical limitations. To ensure the most efficient air traffic system (in terms of throughput, safety, environmental impact, etc.), the functions need to be assessed for their best allocation to prevent over-optimizing one area of the system at the expense of other areas. The information-based, shared situational awareness, and collaborative decision making paradigm enables the redistribution of functions both strategically and tactically. The functions may also be distributed differently for different stakeholders. The method for establishing which element has the tools and information needed to execute these functions is defined in the systems engineering process. The systems engineering process entails developing and evaluating alternative functional allocations based on the system requirements. The most advantageous functional allocation is determined through a requirements-based and benefits-based selection process. This process develops trades of the alternatives, lists the pros and cons, and then selects the best alternative. This is important because ldquobestrdquo can be different for varying scenarios and elements. The major elements, or actors, in the air traffic system are the airplane, ATC, and AOC. These are composed of sub-elements themselves and require assessment of the allocation of functions by management time horizon. The proposed management time horizons are capacity, flow, traffic, separation, and collision avoidance. Once functions have been allocated, simulations (fast-time and human-in-the-loop) and field trials can be used to develop and validate performance requirements for those functions. Finally an example of the possible re-all- ocation of one of the functions of the Air Transportation system is discussed along with the benefits of this alternate allocation.