Amy Spencer

Strategies for designing distributed systems: case studies in the design of an air traffic management system

The air traffic management system in the USA is an example of a distributed problem-solving system. It has elements of both cooperative and competitive problem-solving. It includes complex organizations such as Flight Operations Centers, the FAA Air Traffic Control Systems Command Center (ATCSCC), and traffic management units at en route centers that focus on daily strategic planning, as well as individuals concerned more with immediate tactical decisions (such as air traffic controllers and pilots). The design of this system has evolved over time to rely heavily on the distribution of tasks and control authority in order to keep cognitive complexity manageable for any one individual operator, and to provide redundancy (both human and technological) to serve as a safety net to catch the slips or mistakes that any one person or entity might make. Within this distributed architecture, a number of different conceptual approaches have been applied to deal with cognitive complexity and to provide redundancy. These approaches can be characterized in terms of the strategy for distributing: (1) control or responsibility, (2) knowledge or expertise, (3) access to data, (4) processing capacity, and (5) goals and priorities. This paper will provide an abstract characterization of these alternative strategies for distributing work in terms of these 5 dimensions, and will illustrate and evaluate their effectiveness in terms of concrete realizations found within the National Airspace System.

Requirements for Super Dense Operations for the NGATS Terminal Airspace

We present requirements for super dense operations (SDO) in a future next generation air transportation system (NGATS), targeted at a 2025 timeframe. The requirements emphasize the needs for dynamic weather avoidance maneuvering and performance-based services (PBS) based on required navigation performance (RNP). A net-centric operation (NCO) will provide a mechanism to inform all users of weather forecast information, hazardous weather constraints, and weather avoidance routing requirements. The future air traffic management (ATM) system will move away from static jet route navigation toward a system where routes are defined more dynamically, adjusted during the course of the day as required by traffic demand and the geometry of severe weather constraints. Such a concept of operation (ConOps) will be particularly useful for time periods where weather is a major terminal area constraint in the national airspace system (NAS), making it possible to achieve SDO, reduce traffic delays, and ensure safe operations that would otherwise not be feasible in current day operations.

Dealing with the challenges of distributed planning in a stochastic environment: coordinated contingency planning

Because of its cognitive complexity, the responsibility for operating the National Airspace System (NAS) is distributed among many organizations and individuals. An understanding of how this distributed work system functions requires consideration not only of the allocation of control and responsibility, but also of the distribution of data, knowledge, processing capacities and characteristics, goals and priorities. It further requires consideration of how alternative architectures for distributing work (as defined by these different dimensions) impact performance on different types of tasks described by P. J. Smith et al., (1999). Given such a distributed system, one of the most significant challenges is how to plan at a system level in the face of uncertainty, where the level of uncertainty changes over time. In this paper, we explore a future vision that allows traffic managers and dispatchers to more fully communicate their beliefs about possible weather and traffic constraints described by P. J. Smith et al., (2003), and to indicate how they would respond (or would prefer as a response by someone else who has control and responsibility for responding at that point), depending upon the state of their knowledge at the time when they must act. Instead of communicating their beliefs about the single most likely scenario (weather at BYP from 1400-1500Z), they would communicate their beliefs about the range of possible scenarios that could potentially occur. Then, instead of communicating a single plan, the traffic managers and dispatchers would communicate preferences, constraints or intentions (depending upon whom would have control to make the relevant decision) for each of these contingencies. In addition, because the degree of uncertainty about weather and traffic varies over time and often becomes smaller as the

Traffic flow management strategies to support super-dense operations in the terminal area

In order to achieve the goals associated with the NextGen concept of Super-Dense Operations (SDO) in the terminal area, it is necessary to integrate more tightly strategic and tactical operations. New tactical capabilities offer the potential to increase throughput by enabling reduced separation, more effective sequencing, parallel approaches and flexible arrival and departure routes. The foundation for these tactical capabilities include advanced communication, navigation and surveillance (CNS) functions that enable control based on more closely spaced 4D trajectories enabled by aircraft with tighter Required Navigational Performance (RNP) and RNAV capabilities. Especially in weather scenarios, however, use of these tactical capabilities must be embedded in an integrated approach to managing the traffic flows providing arrivals and departures through SDO airspace. This paper focuses on the development of Collaborative Traffic Flow Management (CTFM) strategies to deliver aircraft to airports and metroplexes (groups of geographically close airports) in a manner that enables effective use of advanced tactical operations making use of Trajectory-Based Operations (TBO) -using 4D Trajectories as a basis to support closely spaced, parallel approaches and departures and the optimization of trajectories to reduce fuel consumption and minimize environmental impacts.

A critique of an operational concept for managing traffic in super dense operations airspace

In a previous paper we outlined an operational concept for managing traffic in Super Dense Operations (SDO) airspace based on a knowledge elicitation effort involving traffic managers and pilots. In this paper we extend this effort, soliciting feedback from a new set of 10 experienced controllers, asking them to evaluate the assumptions and design recommendations making up this operational concept. In the previous paper at this conference, we presented an operational concept for the functioning of airspace operating under Super Density Operations (SDO) that assumes that, in the mid-term (2018) the controllers for SDO for Next Generation Air Transportation System (NextGen) airspace are still responsible for separation assurance and for the merging and spacing of arrivals, departures and overflights. The concept further proposes extensive use of procedural separation based on a predefined “plays” based on a set of alternative advanced Area Navigation (RNAV) arrival and departure routes and based on a set of alternatives for using airspace for arrivals and departures. Assuming datalink capabilities to communicate a new route to the flight deck, the concept further allows for dynamically generated advanced RNAV arrival and departure routes [1–3] when the set of predefined “plays” is insufficient to deal with weather or traffic constraints. In general, the participants were strongly in favor of having predefined route and airspace structures in SDO airspace, with the ability to deal with weather and traffic constraints using predefined alternatives or “plays” whenever possible, but considering dynamically generated route and airspace structures when the predefined “plays” are inadequate. Additional details are provided below.

Future Concepts for Collaborative Traffic Flow Management in the National Airspace System

Because of its cognitive complexity, the responsibility for operating the National Airspace System (NAS) is distributed among many organizations and individuals. An understanding of how this distributed work system functions requires consideration not only of the allocation of control and responsibility, but also of the distribution of data, knowledge, processing capacities and characteristics, goals and priorities. It further requires consideration of how alternative architectures for distributing work (as defined by these different dimensions) impact performance on different types of tasks. Given such a distributed system, one of the most significant challenges is how to plan at a system level, in the face of uncertainty about critical NAS conditions, where the level of uncertainty changes over time. In this paper, a number of concepts for distributing responsibility in the NAS in order to better deal with uncertainty will be discussed, focusing on the need to allocate responsibility so that it better matches access to the knowledge and data necessary to make effective decisions to maintain capacity, safety and equality

Managing arrivals in super-dense operations: Guidance based on a cognitive walkthrough

This paper describes the results of a cognitive walkthrough which was used to structure a knowledge elicitation effort. The goal of this task was to further define and evaluate alternative operational concepts to support evolution toward a Next Generation Air Transportation System (NextGen) in which it is possible to dynamically design the flows for arrivals through super-dense operations (SDO) airspace for an airportal in order to safely maximize throughput given different levels and patterns of traffic demand and given convective weather constraints.

Supporting distributed management of the airport surface

In this report, a simulation system called the Collaborative Airport Traffic System (CATS) was used as a testbed to study human factors issues that arise in the design of a departure metering program [1-11] to manage the inventory delivered to the spots at an airport over time. The focus of this particular study was on procedures, functional requirements, information requirements and interface design concepts for supporting collaboration [12-19] between ARTCC and TRACON TMCs and the Departure Reservoir Coordinator (DRC) responsible for managing a departure metering program during a convective weather scenario.

Airport surface management as a distributed supervisory control task

This paper outlines design concepts that approach airport surface management as a distributed supervisory control system. It emphasizes the need to both distribute the management tasks among a number of different Stakeholders and to support supervisory control by human operators at different levels of abstraction in order to deal with the full range of relevant scenarios and distributed tasks. More specifically, the discussion uses a concrete scenario to describe conceptual solutions to support more effective supervisory control, and illustrates design concepts consistent with these conceptual solutions.

Integrated management of airport surface and airspace constraints for departures: An operational sequence

This paper provides an operational sequence identifying a set of future roles and responsibilities for Air Navigation Service Provider (ANSP) and flight operator staff. It also identifies procedures and technologies necessary to support activities proposed within future operational concepts for an Integrated Arrival/Departure Control Service, Dynamic Departure Routing and airport surface management, with a focus on near-to mid-term (2015–2018) technical capabilities. This operational sequence is then utilized to identify critical human factors considerations at an abstract level. The operational sequence is organized according to a timeline and the assumed context for the scenario. All times are reported in Zulu (Greenwich Mean) Time.