Metropolis 2 aimed to provide the fundamentals for concrete solutions for U-space U3/U4 services that are needed to enable high-density urban aerial operations, with a unified approach to the following U-space services: strategic deconfliction, tactical deconfliction, and dynamic capacity management. It considered three different separation management concepts, differing in how separation is performed (strategic/tactical, ground/air).
The objectives of the project are formulated as follows:
Objective 1: Extend the segmentation and alignment principles of geovectoring to an operational concept for airspace rules to enable high- capacity urban airspace.
Objective 2: Develop a unified design approach to the management of traffic in high-density urban airspace on all timescales, based on the segmentation and alignment principles of geovectoring, in combination with flight planning and detect and avoid paradigms that are designed to leverage the alignment principles from geovectoring, to define robust and efficient flight plans, as well as safe and compliant resolution strategies, which are suitable for operation in a densely used airspace.
Objective 3: Determine the benefits and drawbacks of separation management paradigms with different approaches to who acts as separator: the drone, the U-space service, or a combination thereof, and different combinations of procedural and tactical separation.
Objective 4: Investigate a priority-based integration of manned aviation in urban (drone-only) airspace that robustly integrates with airspace rules and separation provision, such that safety for manned flight is guaranteed, while minimizing degradation of capacity.
Objective 5: Demonstrate the final concept coming out of the Metropolis 2 project in a real-world demonstration.
Conclusions:
With respect to the degree of centralisation, it was seen that having centralised strategic control over all flights, where a joint optimisation is made, did not result in superior performance in terms of safety, compared to reactive, purely tactical separation management, even when no stochastic elements were present in the simulation. This can be seen because the level of intrusions between the two extremes, centralised and decentralised, was similar. However, an improvement in safety seen in constrained airspace for the hybrid concept shows the potential benefit of combining strategic management of traffic (flows) with tactical separation management.
The results of the hybrid concept also reconfirm the safety benefits of an alignment promoting airspace design. In the hybrid concept, the “ring-road” design of open airspace reduced the number of conflicts and intrusions. However, this “ring-road” concept in the hybrid system did tend to add more flight distance and time as compared to the other concepts. This shows that in urban air operations there is an important trade-off between efficiency and safety when considering the airspace structure and strategic routing. Strict pre-planning may have the unintended disadvantage of reducing the accessibility and overall capacity of the airspace.
