The integration of Remotely Piloted Vehicles (RPVs) into civil airspace will require new methods of ensuring traffic avoidance. This paper discusses issues affecting requirements for RPV traffic avoidance systems and describes the safety evaluation process that the international community has deemed necessary to certify such systems. Alternative methods for RPVs to perform traffic avoidance are discussed, including the potential use of new seeand-avoid sensors or the Traffic Alert and Collision Avoidance System (TCAS). Concerns that must be addressed to allow the use of TCAS on RPVs are presented. The paper then details the safety evaluation process that is being implemented to evaluate the safety of TCAS on Global Hawk. The same evaluation process can be extended to other RPVs and traffic avoidance systems for which thorough safety analyses will also be required.
Time-based metering is an efficient air traffic management alternative to the more common practice of distance-based metering (or "miles-in-trail spacing"). The efficiency benefit is most pronounced where air traffic flows merge, such as in terminal airspace, at enroute choke points, overhead merge points, or where severe-weather avoidance routes converge-the primary bottlenecks in today's system. To date, the practice of time-based metering in the United States has been confined to arrival airspace, and only in lessconstrained regions, such as the West and South, in part due to limitations in the national airspace system infrastructure. Thus, time-based metering has not been available to redress the most critical bottlenecks in the national airspace system and, coincidently, those where time-based metering would be most advantageous. This paper discusses a prototype time-based metering system designed to overcome limitations of the national airspace system to produce a more versatile and scalable timebased metering capability. Results of a live, operational field test are presented which validate that the prototype-the Multi-center Traffic Management Advisor-can extend time-based metering operations beyond the terminal area to improve traffic flow at critical bottlenecks en route and on departure. In the field test, which focused specifically on Philadelphia-bound traffic in four Air Route Traffic Control Centers, airborne delay and airborne holding were significantly less when Multi-center Traffic Management Advisor was in use relative to control periods. The results demonstrate that the Multi-center Traffic Management Advisor is effective in coordinating time-based metering programs among adjacent air traffic control facilities, even in the complex Northeast corridor of the United States. This is a necessary step toward addressing the most critical air traffic bottlenecks in the national airspace system. Potential for nationwide time-based metering and its implications for the next-generation air transportation system also are discussed.
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