Douglas R. Isaacson

A Concept for Robust, High Density Terminal Air Traffic Operations

This paper describes a concept for future high-density, terminal air traffic operations that has been developed by interpreting the Joint Planning and Development Office’s vision for the Next Generation (NextGen) air transportation system and coupling it with emergent National Aeronautics and Space Administration (NASA) and other technologies and procedures during the NextGen timeframe. The concept described in this paper includes five core capabilities: 1) extended terminal area routing, 2) precision scheduling along routes, 3) merging and spacing, 4) tactical separation, and 5) off-nominal recovery. Gradual changes are introduced to the National Airspace System by phased enhancements to the core capabilities in the form of increased levels of automation and decision support as well as targeted task delegation. NASA will be evaluating these conceptual technological enhancements in a series of human-in-the- loop simulations and will accelerate development of the most promising capabilities in cooperation with the Federal Aviation Administration through the Efficient Flows Into Congested Airspace Research Transition Team.

FUZZY REASONING-BASED SEQUENCING OF ARRIVAL AIRCRAFT IN THE TERMINAL AREA

A fuzzy reasoning-based method for scheduling air traffic in the terminal area has been designed at the NASA Ames Research Center and operationally tested at the Dallas/Fort Worth Terminal Radar Approach Control (TRACON). The scheduling system sequences and assigns landing times to arrival aircraft by utilizing continuous updates of aircraft radar data and controller inputs. The scheduling algorithm contains a knowledge base which was refined during several thousand hours of controller-in-the-loop real-time simulations. This knowledge base applies fuzzy reasoning to evaluate propositions that consider both performance criteria and workload criteria, such as delay reduction and conflict avoidance. Operational test results show that the algorithm determines an efficient arrival plan to land aircraft in a manner acceptable to the air traffic controllers. This paper details the scheduling algorithm and presents data regarding its effectiveness in predicting the landing order of arrival aircraft.

KNOWLEDGE-BASED RUNWAY ASSIGNMENT FOR ARRIVAL AIRCRAFT IN THE TERMINAL AREA

A knowledge-based system for scheduling arrival traffic in the terminal area, referred to as the Final Approach Spacing Tool (FAST), has been implemented and operationally tested at the Dallas/Fort Worth Terminal Radar Approach Control (TRACON) facility. Two types of controller advisories are generated by FAST: sequence number and runway assignment. The knowledge base for runway assignment employs a set of hierarchical rules and decision logic that evaluates both performance and workload criteria. This formulation is based on over 2,000 hours of controller-in-the-loop, real-time simulations. In the field tests, controllers had the option to accept or reject the FASTgenerated runway assignments. Results indicate strong adherence to the advisories and increased capacity, with no significant impact on controller workload.

A KNOWLEDGE-BASED CONFLICT RESOLUTION ALGORITHM FOR TERMINAL AREA AIR TRAFFIC CONTROL ADVISORY GENERATION

NASA researchers, working under the Aviation System Capacity Program and in conjunction with the FAA Free Flight Program Office, have developed a set of decision support tools to assist terminal area air traffic controllers with control of arrival and departure traffic. Two of these tools, the Final Approach Spacing Tool (FAST) and the Expedite Departure Path (EDP) tool, provide air traffic controllers with heading, speed and altitude advisories to assist in spacing aircraft. This paper describes the conflict prediction and resolution algorithm shared by aFAST and EDP to produce conflict-free aircraft trajectories with realistic conflict resolution maneuvers. The process is accomplished in three stages: prediction, classification and resolution. A conflict prediction scheme is documented which incorporates all applicable FAA separation requirements, including automatic detection of separation during transition from staggered to simultaneous parallel approach operations. A method of classifying predicted conflicts with a limited set of criteria is detailed. Finally, a knowledge-based conflict resolution process is presented which allows for resolution of predicted conflicts in a manner consistent with controller practice: including prioritization of resolution tactics and mixture of multiple degrees of freedom to achieve separation. The scheme has been employed in both closed-loop simulations to determine solution stability and controller-in-the-loop simulations to begin development of the resolution tactics knowledge base.

Tactical Scheduling for Precision Air Traffic Operations: Past Research and Current Problems

Future air transportation systems stand to benefit significantly in safety and efficiency from the predictable movement of aircraft along precisely defined paths in the airspace. Such aircraft movement, hereafter referred to as Precision Air Traffic Operations (PATO), is not widely used during periods of peak air traffic in today’s system, but is the foundation of high-capacity operations envisioned for the future. Automation and deployment of PATO, being a relatively young field of research, has not had time to establish structured theories and standardized reference literature. As a consequence, researchers interested in entering this field have difficulty applying to it classical techniques of operations research and optimal control theory. The main obstacle to such applications is the lack of access to the finer domain knowledge of air traffic operations (most importantly, knowledge of the operational constraints) needed to formulate research problems that promise deployable automation tools. Such a formulation requires the researcher to characterize and assess the research efforts and tendencies that emerged in the recent decades to address diverse problems, some outwardly similar yet essentially different. The research field of PATO has now matured to a stage where this requirement can start being met. This paper, aimed as a step in this direction, provides (a) a formulation of the general problem of defining conceptually, constructing, and using a schedule for PATO that contains specification of merging sequences and provides aircraft separation continuously in time, (b) the context necessary for understanding the formulation and its limitations, and (c) a review of prior research on future Air Traffic Operations (ATO) and, in particular, on the role of Air Traffic Control (ATC) in these operations.

Efficient Computation of Separation-Compliant Speed Advisories for Air Traffic Arriving in Terminal Airspace

A class of problems in air traffic management asks for a scheduling algorithm that supplies the air traffic services authority not only with a schedule of arrivals and departures, but also with speed advisories. Since advisories must be finite, a scheduling algorithm must ultimately produce a finite data set, hence must either start with a purely discrete model or involve a discretization of a continuous one. The former choice, often preferred for intuitive clarity, naturally leads to mixed-integer programs, hindering proofs of correctness and computational cost bounds (crucial for real-time operations). In this paper, a hybrid control system is used to model air traffic scheduling, capturing both the discrete and continuous aspects. This framework is applied to a class of problems, called the Fully Routed Nominal Problem. We prove a number of geometric results on feasible schedules and use these results to formulate an algorithm that attempts to compute a collective speed advisory, effectively finite, and has computational cost polynomial in the number of aircraft. This work is a first step toward optimization and models refined with more realistic detail.

Separation-compliant speed control in terminal airspace

To accommodate the growing air traffic demand, flights will need to be planned and navigated with a much higher level of precision. The Next Generation Air Transportation System (NextGen) stands to benefit significantly in safety and efficiency from such movement of aircraft along precisely defined paths. Air Traffic Operations (ATO) relying on such precision–the Precision Air Traffic Operations or PATO–are the foundation of high throughput capacity envisioned for the future airports. In PATO, the preferred method is to manage the air traffic by assigning a speed profile to each aircraft in a given fleet in a given airspace (in practice known as speed control). In this paper, we develop an algorithm, set in the context of a Hybrid Control System (HCS) model, that determines whether a speed control solution exists for a given fleet of aircraft in a given airspace and if so, computes this solution as a collective speed profile that assures separation if executed without deviation. In this paper, uncertainties such as weather are not considered but the algorithm can be modified to include uncertainties. The algorithm first computes all feasible sequences by looking at all pair combinations of aircraft. Then the most likely sequence is determined and the speed control solution is constructed by a backward algorithm starting with the aircraft last out and proceeds to the first out. This computation for all sequences can be done in parallel which helps to reduce the computation time.

Laboratory Evaluation of Dynamic Routing of Air Traffic in an En Route Arrival Metering Environment [STUB]

Arrival air traffic operations in the presence of convective weather are subject to uncertainty in aircraft routing and subsequently in flight trajectory predictability. Current management of arrival operations in weather-impacted airspace results in significant flight delay and suspension of arrival metering operations. The Dynamic Routing for Arrivals in Weather (DRAW) concept provides flight route amendment advisories to Traffic Management Coordinators to mitigate the impacts of convective weather on arrival operations. DRAW provides both weather conflict and schedule information for proposed route amendments, allowing air traffic managers to simultaneously evaluate weather avoidance routing and potential schedule and delay impacts. Subject matter experts consisting of retired Traffic Management Coordinators and retired Sector Controllers with arrival metering experience participated in a simulation study of Fort Worth Air Route Traffic Control Center arrival operations. Data were collected for Traffic Management Coordinator and Sector Controller participants over three weeks of simulation activities in October, 2017. Traffic Management Coordinators reported acceptable workload levels, a positive impact on their ability to manage arrival traffic while using DRAW, and initiated weather mitigation reroutes earlier while using DRAW. Sector Controllers also reported acceptable workload levels while using DRAW.