Refinement of a conflict probe algorithm and display to support well clear: Concept and implementation

For Unmanned Aircraft Systems to meet the intent of the Federal Aviation Regulations, a technical solution is being developed to enable a Sense and Avoid capability. To contribute to a reduction in the overall Near Mid Air Collision encounter probability, the intended function of conflict probe displays is to provide the pilots with increased awareness of potential future conflicts, resulting in timely preventive maneuvers. A probe contour is generated by computing the locations where a conflict starts and where it ends for a range of ownship tracks. The resulting shape is determined by the specification of the conflict space. At present, various candidate quantitative definitions for “well clear” have been proposed. In previous research it was demonstrated how a probe using the modified-tau algorithm can be used to depict a conceptual well-clear boundary. However, the use of a constant temporal threshold in all probing directions can result in a contour that seems to be connected to ownship even in conflict-free situations. Mitigation of this undesired effect is performed via tau-weakening, a refinement to the existing probing function. Furthermore, how the specification of a Horizontal Miss Distance as part of the well clear definition impacts the depiction of the conflict space is discussed in this paper. Also, the potential impact of wind for the situation in which constant airspeed is maintained during a maneuver rather than constant ground-speed is discussed. The paper concludes with a set of recommendations for conflict geometries that aim to allow the potential benefits of the depiction of the conflict space to be measured and enable the impact of different definitions of well clear to be analyzed.