Evaluation of a conflict probe which, promises to be a key element of the future US "free-flight" air-traffic-management system is under way at Indianapolis. The prototype conflict probe, named the user-requirement evaluation tool (URET), has been developed for the US Federal Aviation Administration by Mitre's Center for Advanced Aviation System Development.

In the free-flight concept, each aircraft will be flown on its optimum flight path, with ATC monitoring separation and providing information on position and short-term intent. The conflict probe will be used to project aircraft flight-plans, to check for any airspace or runway contention.

The URET prototype maintains flight-plan-based trajectories for aircraft being handled by the Indianapolis centre, predicts aircraft positions up to 20min into the future, and alerts the controller to any conflicts between two or more aircraft, or between aircraft and restricted airspace. The URET allows the controller to try out proposed flight-plan amendments before clearances are issued.

The prototype is now being operated in "shadow mode" to provide support to the existing data controller, who is responsible for longer-term "strategic" ATC decisions and who co-ordinates with the radar controller responsible for shorter-term "tactical" ATC decisions. The URET has been "favourably received" by controllers, according to Mitre.

Mitre is now planning trials of another free-flight element - the self-managed arrival time system. This will enable airline dispatchers to change the arrival sequence of aircraft to suit their needs. An operational evaluation is planned, with United Parcel Service using the system to match aircraft arrivals to capacity at its Louisville, Kentucky, hub. Aircraft speed will be adjusted en route to eliminate fuel wasting while holding over Louisville.

Source: Flight International