Researchers at the NASA Langley ResearchCenter are developing the Airborne Precision Spacing (APS) concept to increase runway arrival throughput at capacity-constrained airports. Under APS operations, arrival capacity is increased by improving the precision of inter-arrival spacing at the runway threshold. Flight crews achieve this improved precision with the assistance of a new flight-deck system, which allows spacing operations to commence even while the aircraft and its lead are on different arrival routes to the runway. However, the increases in traffic volume that could be enabled by APS operations could also elevate noise concerns at busy airports.Noise-and fuel-efficiency concerns have independently motivated the air traffic management community to investigate Continuous Descent Approaches (CDAs) as alternatives to traditional arrival route profiles. However, uncertainties associated with CDA operations can cause runway capacity to be sacrificed. For this reason, CDA routes have only been implemented during lowdensity traffic operations.In this paper we report on current research into the integration of these two advancements, by employing APS operations to merge and space aircraft that are flying CDA arrival routes. Results obtained to date indicate that, while retaining the benefits of both techniques may be unachievable, APS operations can achieve narrow distributions of inter-aircraft spacing errors at the runway threshold for CDA routes. Analysis of the data also indicates that the spacing error distribution may be sensitive to inaccuracies in modeling the CDA trajectories for the aircraft and its lead.

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NASA researchers are developing new airborne technologies and procedures to increase runway throughput at capacity-constrained airports by improving the precision of interarrival spacing at the runway threshold. In this new operational concept, pilots of equipped aircraft are cleared to adjust aircraft speed to achieve a designated spacing interval at the runway threshold, relative to a designated lead aircraft. A new airborne toolset, prototypes of which are being developed at the NASA Langley Research Center, assists pilots in achieving this objective. The current prototype allows precision spacing operations to commence even when the aircraft and its lead are not yet in-trail, but are on merging arrival routes to the runway. A series of fast-time evaluations of the new toolset were conducted at the Langley Research Center during the summer of 2004. The study assessed toolset performance in a mixed fleet of aircraft on three merging arrival streams under a range of operating conditions. The results of the study indicate that the prototype possesses a high degree of robustness to moderate variations in operating conditions.

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Interval Management is a suite of ADS-B-enabled applications that allows the air traffic controller to instruct a flight crew to achieve and maintain a desired spacing relative to another aircraft. The flight crew, assisted by automation, manages the speed of their aircraft to deliver more precise inter-aircraft spacing than is otherwise possible, which increases traffic throughput at the same or higher levels of safety. Interval Management has evolved from a long history of research and is now seen as a core NextGen capability. With avionics standards recently published, completion of an Investment Analysis Readiness Decision by the FAA, and multiple flight tests planned, Interval Management will soon be part of everyday use in the National Airspace System. Second generation, Advanced Interval Management capabilities are being planned to provide a wider range of operations and improved performance and benefits. This paper briefly reviews the evolution of Interval Management and describes current development and deployment plans. It also reviews concepts under development as the next generation of applications.