Real-time Conflict Detection and Resolution

The stage

At very high altitudes, aircraft move primarily horizontal, straight, and at a steady speed, with the occasional climb or descent; not very challenging from the computing perspective. Air traffic in lower controlled airspace is primarily vertical. Most aircraft are either climbing to attain their cruising altitude, or descending to approach their destination airport. Air traffic controllers issue clearances to climb or descent, ensuring that aircraft can transition between altitudes without conflicts. This is no small cognitive feat, as Homo sapiens tends to think in two dimensions.

The software

In 2011, the R&D division of DFS Deutsche Flugsicherung, the German air navigation service provider, contracted GLVI to develop the conflict detection and resolution software components of their CATO Controller Assistance Tools research prototype. The tools assist controllers in two ways: They alert air traffic controllers to existing conflicts in the current situation, and they continuously run extensive clearance simulations.

The first function acts as another pair of eyes for the air traffic controllers. The cognitive workload on controllers in dense traffic situations can be quite demanding. The software makes sure, that no conflict escapes the attention of the controllers.

The second function is a bit less obvious: A clearance simulation is to speculate “What would the situation probably look like, if this aircraft were cleared to this altitude? Would that situation be free of conflicts?” The software conducts these simulations extensively: For every aircraft on frequency, for every clearable flight level, for every clearable climb rate, for every clearable heading, for every clearable waypoint, what would the situation be if this were the clearance given to this aircraft? Would the situation be free of conflicts? Like a chess computer, the software determines the consequences of possible next steps to take. Information thus gained is presented to controllers on occasion and when useful.

On the operational display of the air traffic control system, whenever a menu is opened to clear a flight, all available options will be colour coded. For every option there will be an indication whether such a clearance would be free of conflicts, or whether it would entail some conflict, or whether it would need additional constraints to remain free of conflicts. Presenting this information in a proper fashion, imparts additional situational awareness on controllers. Usually, they look onto a flat screen, and perceive air traffic from the bird’s eye perspective. Presenting available flight levels in a ladder-like fashion, or available headings in a pie-chart fashion – all colour coded to indicate conflicts or additional constraints – conveys a first-person perspective i.e. lets the controller perceive the situation from the perspective of the aircraft to be cleared.

The software has been validated and proven feasible for significantly higher amounts of air traffic than today while maintaining or improving safety levels. The software is currently going into service at DFS Deutsche Flugsicherung.