978-1-4799-1538-5/13/$31.00 ©2013 IEEE 1A2-1 EVALUATION OF THE TERMINAL SEQUENCING AND SPACING SYSTEM FOR PERFORMANCE-BASED NAVIGATION ARRIVALS Jane Thipphavong, Dr. Jaewoo Jung, Harry Swenson, NASA Ames Research Center, Moffett Field, CA Dr. Lynne Martin, San Jose State University, San Jose, CA Melody Lin, Jimmy Nguyen, Optimal Synthesis, Los Altos, CA Abstract NASA has developed the Terminal Sequencing and Spacing (TSS) system, a suite of advanced arrival management technologies combining time- based scheduling and controller precision spacing tools. TSS is a ground-based controller automation tool that facilitates sequencing and merging arrivals that have both current standard ATC routes and terminal Performance-Based Navigation (PBN) routes, especially during highly congested demand periods. In collaboration with the FAA and MITRE’s Center for Advanced Aviation System Development (CAASD), TSS system performance was evaluated in human-in-the-loop (HITL) simulations with currently active controllers as participants. Traffic scenarios had mixed Area Navigation (RNAV) and Required Navigation Performance (RNP) equipage, where the more advanced RNP-equipped aircraft had preferential treatment with a shorter approach option. Simulation results indicate the TSS system achieved benefits by enabling PBN, while maintaining high throughput rates-10% above baseline demand levels. Flight path predictability improved, where path deviation was reduced by 2 NM on average and variance in the downwind leg length was 75% less. Arrivals flew more fuel-efficient descents for longer, spending an average of 39 seconds less in step-down level altitude segments. Self-reported controller workload was reduced, with statistically significant differences at the p<0.01 level. The RNP-equipped arrivals were also able to more frequently capitalize on the benefits of being “Best-Equipped, Best- Served” (BEBS), where less vectoring was needed and nearly all RNP approaches were conducted without interruption. Introduction The United States Next Generation Air Transportation System (or NextGen) is being designed to support the predicted increases in traffic volume and to increase the capacity, efficiency and safety of the National Airspace System (NAS). The Federal Aviation Administration (FAA) identifies Performance-Based Navigation (PBN) as a key enabling capability in NextGen and is actively developing and implementing PBN procedures and routes at major airports nationwide [1]. PBN defines aircraft performance requirements in terms of navigation specifications. There are two kinds of navigation specifications: Area Navigation (RNAV) and Required Navigation Performance (RNP). RNP is a higher-fidelity RNAV specification with the addition of on-board performance monitoring and alerting as part of the avionics functionality. Aircraft equipped with RNP can fly procedures that are contained within a tightly defined corridor of airspace, which would increase predictability of flight paths to assist in the planning of efficient flows. To incentivize RNP aircraft equipage, these aircraft may have preferential routing with shortened flight distance or reduced separation requirements. Over 90% of commercial jets are already RNAV-equipped and less than half have advanced RNP equipage [2]. PBN Standard Terminal Arrival Routes (STAR), procedures, and approaches are designed to be fuel- efficient optimal profile descents (OPDs) and also account for unique operational requirements such as avoiding terrain or other obstacles, de-conflicting airspace, or resolving environmental constraints [3]. PBN arrivals have been shown to increase efficiency and reduce delays, but their use is limited during periods of high traffic demand due to the complexity of merging multiple streams of aircraft to the same airport. Arrivals in the Terminal Radar Approach Control (TRACON) area are still primarily controlled using radar vectoring and step-down descents, resulting in high workload for controllers and