Methods for maintaining benefits for merging aircraft on terminal RNAV routes

Current terminal operations are changing as more terminal area navigation (RNAV) routes are defined that aircraft are expected to fly. Previously, arriving aircraft filing a standard terminal arrival route (STAR) were given vectors to guide them to the runway when the aircraft transitions from the STAR and enters the terminal area. There are, however, efforts underway to extend these STARs as routes in the terminal area that overlay the current traffic patterns resulting from the vectors that controllers give to the aircraft. With the introduction of more terminal RNAV arrival procedures, anticipated benefits range from reduced voice communication, improved situational awareness, reduced flying time and distance, improved predictability to increased throughput. However, to achieve these benefits, the aircraft must remain on the planned RNAV routes. This is a change in paradigm from the current practice of vectoring the aircraft to achieve the proper sequence and spacing in the terminal area. This paper reports on a concept for allowing the aircraft to remain on RNAV routes while managing the flow of the aircraft to the final approach segment. The concept discussed in this paper is part of a broader suite of concepts currently being investigated to address merging and spacing problems arising from structured RNAV and required navigation performance (RNP) routes in the terminal environment. This suite of concepts is referred to as spacing of performance-based arrivals on converging routes (SPACR) and is intended to address the near-term merging and spacing problem, relying on existing cockpit and ground automation capabilities. SPACR includes applications of cockpit capabilities such as FMS offsets and required time of arrival (RTA) and ground automation functionalities such as the embedded ghosting function in the STARS and new STARS graphical user interface (GUI) functionalities. The concept described in this paper involves using the current implementation of the converging runway display aid (CRDA) as a controller aid to visualize the relative spacing for uncoordinated terminal merges with speed control and the lateral offset function of many current flight management systems (FMS) to resolve spacing problems. A parametric analysis was performed of the controllability of such a concept and a controller-in-the-loop simulation using typical terminal area geometry was run to explore several issues. These issues include mixed equipage, route design and airspace usage as well as initial thoughts on controller acceptance. The results of the analysis and simulation as they pertain to maintaining terminal RNAV benefits are reported in this paper.