The time windows and the routes identified at the strategic level (read our insight on strategic planning) need to be validated at the tactical level, i.e. from an operational point of view. At this stage, we perform scenario simulations of the en-route phase of all flights present in a selected (large) portion of the airspace over a selected time horizon, such as one day. The input to these simulations are
- the planned 4-D trajectories for all considered flights obtained in the strategic planning phase and
- (ii) the associated Time Windows. Such data will feed the agent based model (ABM) developed within the SESAR WP-E ELSA project (Gurtner, et al., 2017, Bongiorno, et al., 2017).
The simulations will be performed in accordance with the tactical scenarios, and will help us in understanding whether the proposed time windows are meaningful from an operational point of view. In other words, we assess
- whether or not they lead to a situation where Air Traffic Controllers (ATCOs) can still manage the air traffic present in their sector and
- whether or not their introduction could cause additional delays in the tactical phase due to the fact that the planned trajectories must be modified in order to make them conflict-free. In fact, in the determination of the Time windows at the strategic level, only the nominal capacity of each sector is taken into account as that is the only certain information available in that phase.
Hotstops and coldpots
In addition, through the use of the ELSA model we will investigate in a statistically robust way which are the navigation points of a given sector characterized by a number of flights higher or lower than expected (hotspots and “coldspots”, respectively). Coldspots are also important as they can signal portions of airspaces routinely avoided by aircraft. In some cases, these coldspots might provide a useful alternative to hotspots. Such statistical analysis can be performed within a certain time horizon (i.e., one or two hours) thus giving an intraday profile of the over-(under-)
used navigation points over the day (Gurtner, et al., 2017).
The statistical characterization of hotspots and coldspots at the tactical level has a twofold importance. On one side, we want to check whether the hotspots/coldspots detected starting from the strategically planned and actual trajectories are the same or not. Operatively this should indicate whether the introduction of time windows mitigate the risk of congestion in a limited way or they really lead to a less congested airspace. On the other side, the detection of hotspots/coldspots at the tactical level might identify regions of the airspace that are structurally different from others and where the mitigation of congestion probably requires a heavier and deeper re-planning of the flight trajectories or of the network infrastructure.