Free Flight in a Crowded Airspace?

In the report of the RTCA Free Flight Task Force, Free Flight is presented as a range of concepts, allowing selfoptimisation of the routes by the airlines. The document also describes a mechanism for airborne separation as a part of the Free Flight concept. Whether airborne separation is allowed depends on, among other things, the so-called “dynamic density”. This dynamic density is a measure of the density and the complexity of the traffic pattern. According to the original airborne Free Flight concept as described in the RTCA document, when the dynamic density is too high, less freedom will be allowed and separation will remain on the ground. This is based on the assumption that central co-ordination is required in these cases. However, this paper will try to demonstrate via analysis and simulation results, why it is precisely high density situations that require the power of a distributed system. It describes the concept as designed in the NLR study as an example of the implementation of the Free Flight concept. The lessons learned apply to most airborne separation concepts. The effect of a distributed ATM system will be illustrated by looking at some sample scenarios, the robustness and the conflict rates. Biography of authors J.M. Hoekstra graduated in 1991 at the Technical University of Delft at the Faculty of Aerospace Engineering. He joined NLR at the Flight Simulation and Handling Qualities department. He worked on model development, display design, handling qualities, human factors studies and accident analysis. Topics include Head-Up Displays, Flight Control Systems, Flight Management Systems, Controller Pilot Data Link and Free Flight. In the beginning of 1998, he transferred to the human factors department and is now project manager of the NLR/NASA Free Flight project. Rob Ruigrok graduated in 1992 at the Delft University of Technology, Faculty of Aerospace Engineering. He has been working at NLR's Flight Simulation department, on Flight Management Systems, Controller-Pilot Datalink, Take Off Performance Monitoring Systems, Windshear detection systems, Traffic Alert and Collision Avoidance Systems and Free Flight. Since two years he has been working in NLR's Flight Mechanics department on Free Flight and the integration of warning systems (terrain, traffic, weather) in the cockpit. He holds a Private Pilot Licence. Ronald van Gent has studied aeronautical engineering at the Delft University of Technology where he received his MSc in 1987. After that he has been working in the area of Human Factors, first at TNO in Soesterberg, later in Amsterdam at the NLR. Main projects he was involved in were pilot-controller datalink studies and the Free Flight studies. In 1999 he has become the Human Factors department head at the NLR.