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Crew Activity Tracking System (CATS)
CTAS-FMS Integration, 2002 (CFI'02)
Distributed Air Ground Traffic Management (DAG-TM)
Multi-Sector Planner

Crew Activity Tracking System (CATS):

The Crew Activity Tracking System (CATS) tracks human operator activities to detect deviations from correct operations that may impact the safety of complex systems. It supports visualization and analysis of operator-caused deviations and the context surrounding them. CATS has a computational hierarchical model of the preferred way to control the system. With data about the current state of the system and constraints on its behavior, CATS generates a representation of the current operational context and predicts operator activities according to its model. CATS compares each actual operator action it detects to its predictions to determine if the action is: (1) preferable according to the model, (2) part of a valid alternative method for performing a required function, or (3) an error of commission. CATS also ensures that human operators perform activities to meet high-level control requirements; if not, CATS signals errors of omission. In addition to tracking operator activities, CATS also provides a framework for intelligent agents that can control simulated complex systems in predictable ways to support design.

CTAS-FMS Integration, 2002 (CFI'02):

CFI'02 compares a sector-oriented approach to arrival flow management to a candidate trajectory-oriented approach. The sector-oriented approach is bases on current day operations for handling arrival traffic in a time-based metering situation. The trajectory-oriented approach provides advanced tools for the controller and introduces a more active interaction with the traffic management coordinator (TMC). These additions may help manage an arrival flow from a broader perspective, helping controllers, especially controllers in upstream sectors, to use strategic clearances to improve the downstream flow at the meter fix merge.

CFI'02 seeks to validate the assumed benefits associated with a trajectory-oriented approach. This research will be conducted in two operational modes. The first is a baseline condition resembling current day operations for time-based metering. The trajectory-oriented approach is the other condition, adding such tools as CTAS/FMS descent procedures, conflict prediction, trial planning, speed advisories, automation to support controller-controller clearance coordination, and TMA-derived meter fix RTA advisory updates to en route aircraft.

The CFI'02 experiment gives us an opportunity to determine what benefits can be gained by introducing ground-based procedures for trajectory-oriented traffic management, and to develop scenarios and metrics to support other DAG-TM concepts.

Distributed Air Ground Traffic Management (DAG-TM):

The Distributed Air/Ground Traffic Management (DAG-TM) concept is a coherent set of conceptual elements that describe possible modes of operation within the outlines of the Free Flight concept defined by the RTCA Task Force. It may be viewed as one possible approach to the potential implementation of Free Flight, progressing along the path started by the Free Flight Phase 1 activities. This DAG-TM concept was developed by the Advanced Air Transportation Technologies (AATT) Project.

Distributed Air/Ground Traffic Management is a National Airspace System concept in which flight deck (FD) crews, air traffic service providers (ATSP) and aeronautical operational control (AOC) facilities use distributed decision-making to enable user preferences and increase system capacity, while meeting air traffic management requirements. DAG-TM will be accomplished with a human-centered operational paradigm enabled by procedural and technological innovations. These innovations include automation aids, information sharing and Communication, Navigation, and Surveillance (CNS) / Air Traffic Management (ATM) technologies.

DAG-TM is a proposed concept for gate-to-gate NAS operations beyond the year 2015. It will address dynamic NAS constraints such as bad weather, Special Use Airspace (SUA) and arrival metering/spacing. The goal of DAG-TM is to enhance user flexibility/efficiency and increase system capacity, without adversely affecting system safety or restricting user accessibility to the NAS. The DAG-TM concept is intended to address all user classes (commercial carriers, general aviation, etc.) with an emphasis towards ensuring access to airspace resources for the entire user community. It covers all flight phases (Pre-Flight Planning, Departure, Cruise and Arrival) and operational domains in the NAS (Surface, Terminal Airspace and En route Airspace). Although other operational domains (e.g., European, oceanic, and under-developed airspace) are outside the scope of the current DAG-TM concept, research activities will give due consideration to global interoperability issues.

For more information, see the DAG-TM website here.

Multi-Sector Planner

The Federal Aviation Administration (FAA) is investigating a concept that introduces a new multi-sector planner (MSP) position within air traffic operations. A key research issue is the determination of roles and responsibilities of the MSP in relation to the current controller and traffic management teams. The AOL works closely with the FAA in developing, and evaluating technologies, and operational procedures to assess the impact of this new team concept on future airspace operations.

Problem and Prior Research

Air traffic control in the en route airspace environment in the United States (U.S.) has traditionally been performed by a team, consisting of a radar-controller (R-side) and a second controller referred to as a data-controller (D-side) or a radar-associate. Several developments in the technology supporting air traffic management- digital data communication among controllers and between controllers and aircraft, improved positioning accuracy for flight operations, conflict prediction, and sector complexity assessment- have enabled consideration of new organizational structure and functional standards for team operations. One such consideration is a modification of a standard configuration to include a "multi-sector planner" (MSP) position in the team. This MSP position has been investigated in several research and field studies, both in the U.S. and in Europe. The concept provides a spectrum of redistributed roles and responsibilities among the air traffic management team members including physical relocation. The feasibility and effectiveness of two variations of these concepts were investigated initially with the Cognitive Systems Engineering evaluative methodology described in Corker et al (2007).

Image of Multi-Sector Planner WorkstationThe two concepts for the MSP position that were developed for the FAA in 2005 by researchers from NASA Ames and San Jose State University were: a "Multi-D" concept, where the MSP acts as a D-side controller for several radar controllers, and an "area flow planner" concept. In 2006, a human in the loop (HITL) simulation was conducted to compare both concepts to a baseline condition. Results from this simulation led to selection of the area flow planner concept for further development.

The role of the area flow planner MSP, as tested in 2006, was to support the radar controller by planning ahead and smoothing "medium-term" traffic flows for the three sectors within their area of responsibility. Under this concept the MSP had responsibility for managing traffic flows and balancing traffic loads within the multi-sector region of airspace.

While the 2006 simulation demonstrated initial feasibility of the MSP position as an effective member of the air traffic controller team, it was not designed to assess how successfully the MSP could monitor and manage flow problems within his or her own area while also providing assistance to adjacent MSPs. Follow-on research in this area was recommended and is now ongoing, along with the development of communication tools and decision aids, and of appropriate procedures, roles and responsibilities for effective integration of this position within the facility and the NAS.

Follow-up Research

Current research activities build on the results from 2006 and follow the primary recommendations. The objectives include:

(1) Develop procedures for MSP-MSP interactions both within and across facility boundaries. Evaluate impact and feasibility considering that (a) each MSP is actively managing within-area flow responsibilities, while responding to external requests for assistance; and (b) there is an inherent dependency on upstream actions to accomplish local goals. This dependency means that effective collaboration procedures are crucial to the position's success.
(2) Expand the definition of roles, responsibilities, and procedures, integrating the MSPs within the larger context of air traffic control and traffic management operations.
(3) Determine the information and decision support tool the MSP needs for situation assessment, traffic flow manipulation, and for coordination with others (R-sides, D-sides, adjacent MSPs, adjacent and underlying facilities, TMU, and front-line managers).

These objectives are being addressed in a series of activities, including: cognitive walkthroughs, simulation shakedown/walkthroughs, and a 4-week HITL evaluation. The objective of the first two walkthroughs was to develop and refine the MSP concept of operations, with particular focus on interactions between the MSP and other positions; the MSP's information and automation support requirements; and identifying research issues and planning the 2009 HITL simulation. Technologies available on the MSP position as well as communication means to facilitate automated interaction with other ATC operators are prototyped by the AOL R&D team based on the 2006 findings and the walkthrough activities described above.

Mock-up of Multi Sector Planner workstation for upcoming simulation in 2009
Mock-up of Multi Sector Planner (MSP) workstation for upcoming Human-in-the-Loop simulation in 2009


K. Corker, D. . Liang, P. U. Lee, & T. . Prevot (2007) New Air Traffic Management Concepts Analysis Methodology: Application to a Multi-Sector Planner in US Airspace, Air Traffic Control Quarterly Vol 15 (4)

T. . Prevot, P. U. Lee, L. . Martin, J. S. Mercer, E. A. Palmer, & N. M. Smith (2006) Tools for Trajectory-Based Air Traffic Control and Multi Sector Planning, HCI-Aero 2006, Seattle, WA, September 2006

Point of Contact: Nancy Smith, NASA Ames Research Center


The Operational Airspace Sectorization Integrated System (OASIS) tool assists Area Supervisors in their planning of sector combine/decombine operations as well as opening/closing of Data-side (D-side) control positions. These advisory solutions are tailored to the predicted traffic demand over the next few hours.

Dynamic Airspace Configuration (DAC) is a new operational paradigm that proposes to migrate from the current structured, static airspace to a dynamic airspace capable of adapting to user demand while meeting changing constraints of weather, traffic congestion and complexity, as well as a highly diverse aircraft fleet.

DAC research consists of three major components: 1) the overall organization of the airspace; 2) dynamically changing airspace to meet the demand; and 3) a generic airspace characterization. The first component relates to a strategic organization of airspace and the creation of new classes of airspace to take advantage of concepts and technologies that are expected to be available by 2025. The second component relates to the dynamic airspace reconfiguration that is needed to accommodate a fluctuating demand. The third component relates to "generic" airspace designs that could promote interchangeability among facilities and controllers by removing structural and functional components of the airspace that would require site-specific training of the airspace.


The National Airspace System (NAS) is an interconnected system of airports, air traffic facilities, equipment, navigation aids, and airways. Airspace design engineers and air transportation policy makers are continually adjusting system parameters in an attempt to anticipate changes in system demand that result as a consequence of foreseen (e.g. time of day) and unforeseen factors (e.g. weather systems that disrupt the NAS), or because of changes in air traffic management (ATM) policies that govern the operations in the NAS. One key element in guiding the safe and efficient operations of the NAS is airspace management. Airspace management requires predicting the load that is being placed and the capacity possible in the NAS. The current NAS architecture is reaching the limits of its ability to accommodate increases in traffic demand.

An essential element of the NAS transformation is to use more efficient allocation of airspace as a capacity management technique. The NextGen concept calls for a future system in which daily operations are managed with four-dimensional (4D) aircraft trajectories while the airspace structure and controller resources are continually adjusted to meet user needs. The airspace structural adjustments needed to manage traffic demands and capacity issues are being examined at NASA as part of a set of research activities called Dynamic Airspace Configuration (DAC) under the NGATS ATM-Airspace project.

Prior Research

In 2007 to 2008, we were engaged in two activities in support of the initial stages of DAC research. The first activity involved documenting current state-of-the-art on the airspace design and configuration practices in order to provide a baseline from which the future system can improve upon. The second activity was a human-in-the-loop simulation on the effects of mixed equipage on airspace configuration.

Examination of Current Airspace Structural Components and Configuration Practices

To understand how the air traffic system can transform from current airspace structures and operational practices to what is envisioned in the NextGen operations, we cataloged DAC-relevant airspace components and operations used in the present day, as well as research and near-term operational implementations that are currently being pursued. Dynamic airspace reconfiguration in current operations has limited options in terms of how sectors and airspace can be reconfigured due to various technological and human factors issues. DAC envisions the future sectors to be substantially more dynamic, changing fluidly with the changes in traffic, weather, and resource demands.

Effects of Mixed Operations on Airspace Configuration

Future airspace configuration is largely uncharted and one of the most interesting areas of research. As the new concepts such as automated separation assurance (e.g. automation detects and resolves conflicts between aircraft that meet minimum equipage requirement) evolve, the airspace must be designed and configured to support them. One of key assumptions that need to be defined before designing new airspace configuration methodologies is to determine whether the future airspace should be segregated or integrated. Segregated (also known as exclusionary) airspace refers to that airspace which only allows aircraft that are supported by either ground-based or air-borne separation management automation. Integrated (also known as non-exclusionary) airspace refers to that airspace which allows both types of aircraft, aircraft that are supported by separation management automation and aircraft that are not supported by such automation. Under the segregated airspace operations where the automation is responsible for conflict detection and resolution; the role of controller is largely confined to monitoring, if deemed useful, under normal operations. Under the integrated airspace operations the automation is responsible for conflict detection of all aircraft and resolution of aircraft that are equipped or capable of being supported by such automation whereas the controller is responsible for conflict resolution of aircraft that are not equipped to support the automated separation.

An experiment was conducted to investigate the effects of Mixed Operations on Airspace Configuration. A general hypothesis of the study was that mixed equipage operations would be feasible during moderate traffic levels for both the unequipped aircraft that the controllers needed to control and the total number of aircraft in the sector. It was also hypothesized that there exists a certain critical airspace complexity threshold that once exceeded would make the mixed operations infeasible. In order to explore the effects of traffic densities and the associated airspace complexity, the experiment varied two traffic factors, namely the traffic levels of unequipped and the equipped aircraft.

Image of Controller display with equipped (dim limited datablock) and unequipped (colored full datablock) aircraft in mixed separation-assurance airspace
Controller display with equipped (dim limited datablock) and unequipped (colored full datablock) aircraft in mixed separation-assurance airspace

Follow-up Research

A human-in-the-loop simulation study was conducted in 2009 to examine the limits of the number and the types of changes in the airspace that the controllers can handle in dynamic airspace reconfiguration of future operations. Some of the interesting variables that may affect the ability of the controllers to adapt to airspace changes include:

- Boundary change methodology- airspace boundaries can change instantaneously from one sector configuration to another, or they can "morph" incrementally
- Rapidity of changes- how often can the boundaries be changed before exceeding controllers' cognitive capability to adapt
- Level of traffic complexity at the boundary change- e.g. number of climbing/descending aircraft, complexity of merge points, etc.
- Number of variables that change at the boundary change- e.g. changes in route structures, radio frequencies, area of responsibility (e.g. change in controlled airspace altogether), etc.
- Amount of coordination and/or training required prior to the airspace change
- Assumptions about decision support tools and separation responsibilities- e.g. automation support for transfer-of-communication, conflict detection, conflict resolution, etc.

A team of researchers- consisting of algorithm developers who were researching ways to optimally change airspace boundaries, operational experts who understood trigger events that lead to airspace changes in current operations, and human factors researchers - worked together to explore the impact of dynamic airspace changes on the controllers and the feasible limits of the changes that are possible in the future airspace.

Click to download the complete Separation Assurance research report Download the full Dynamic Airspace Configuration Synopsis (PDF - 612KB)


Boetig, R.C., Borowski, M., & Wendling V.S. (2004). ZOA HAR design and Q Route validation, MP04W0000236, The MITRE Corporation, McLean, VA.

Doble, N.A., Hoffman, R., Lee, P.U., Mercer, J., Gore, B., Smith, N., & Lee, K. (2008). Current Airspace Configruation Practices and their Implications for Future Airspace Concepts, AIAA 8th Aviation Technology Integration Operations Seminar, Anchorage, AK.

Lee, P.U., Mercer, J., Gore, B., Smith, N., Lee, K., & Hoffman, R. (2008). Examining Airspace Structural Components and Configruation Practices for Dynamic Airspace Configuration, AIAA Guidance, Navigation, and Control Conference and Exhibit 18 - 21 August 2008, Honolulu, HI.

Kopardekar, P., Bilimoria, K., & Sridhar, B. (2007). Initial concepts for Dynamic Airspace Configuration, 7th Aviation Technology, Integration and Operations (ATIO) Seminar.AIAA, Belfast, Northern Ireland.

Point of Contact: Paul Lee, Ph.D, San Jose State University/NASA Ames Research Center
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Curator: Phil So
NASA Official: Everett Palmer
Last Updated: July 18, 2014