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Supporting the Future Air Traffic Control Projection Process

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Supporting the Future Air Traffic Control Projection Process t Supporting the Future Air Traffic Control Projection Process Hayley J. Davison & R John Hansman, Jr. International Centerfor Air Transportation Massachusetts Institute of Technology Cambridge, MA USA ABSTRACT traffic systems that are being designed for the In air traffic control, projecting what the air traffic future. situation will be over the next 30 seconds to 30 minutes is The air traffic control system is at a point of a key process in identifying conflicts that may arise so transition that could potentially change the that evasive action can be taken upon discovery of these conflicts. A series of field visits in the Boston and New controller’s projection task. As the demand for York terminal radar approach control (TRACON) more fuel-efficient and environment-fnendly facilities and in the oceanic air traffic control facilities in procedures increases, there is a need for increased New York and Reylqavlk, Iceland were conducted to flexibility currently required by the FAA and other investigate the projection process in two different ATC air traffic authorities. It is critical to determine the domains. The results from the site visits suggest that two role of the existing structure in the airspace and types of projection are currently used in ATC tasks, procedures in the controller’s projection task before depending on the type of separation minima and/or traffic it is removed or changed. restriction and information display used by the controller. As technologies improve and procedures change, care One example of a procedure increasing route should be taken by designers to support projection flexibility is the constant deceleration approach through displays, automation, and procedures. It is procedures that reduce noise pollution over cities, critical to prevent time/space mismatches between but these procedures also require the aircraft to interfaces and restrictions. Existing structure in traffic follow a deceleration profile determined by the dynamics could be utilized to provide controllers with aircraft’s automation rather than a profile cleared by useful behavioral models on which to build projections. the air traffic controller (Clarke & Hansman, 1997). Subtle structure that the controllers are unable to An example of a procedure increasing lateral route internalize could be incorporated into an ATC projection flexibility is the free-routing procedure being aid. implemented over the oceans that cut down both flight time and fuel usage on overseas flights. KEYWORDS These free routing procedures require flexibility projection, situation awareness, air traffic control, from strict tracks structures used to ensure adequate information requirements, decision support separation over poorly-surveilled oceanic environments (NAT-IMG, 1999). This paper investigates how the air traffic control INTRODUCTION Projection is one of the three critical stages that projection is currently performed, including the role of structure, and discusses the limitations of human contribute to an air traffic controller’s situation awareness (Endsley, 2000). A controller must be projection. Suggestions are provided to support these human projection limitations in the future. able to project current aircraft states in order to identify conflicts so that they can be resolved before they occur. However, it is unclear how controllers METHOD perform this critical task in the current air traffic Preliminary models of controller cognition were environment. The difficulty in understanding produced, based on a more general ATC cognitive current projection limitations complicates the model proposed in Reynolds, et al. (2002) and establishment of projection requirements for air modified using job/task analyses for TRACON and oceanic air traffic controllers (Endsley & Jones, 1995; Lenorovitz, Schaghaghi, Felbinger, & Tyler, sector, the controller must descend aircraft from the 2000). entry point of the sector to the final approach Site visits were then performed at terminal radar altitude while directing the aircraft to capture the approach control (TRACON) facilities and at ILS beam on an instrument approach. The majority oceanic facilities to revise the cognitive models of traffic in this sector are in transition both created and to specifically probe the projection laterally and vertically. Precise commands are process. TRACON site visits included four 4-hour required of the controller to direct aircraft to the visits to Boston and two 4-hour visits to New York. physical constraint of the ILS beam, and there are Oceanic site visits included four 4-hour visits to stringent requirements on the communication and New York and five 4-hour visits to Reykjavik, surveillance systems within the TRACON to allow Iceland. the controller to ensure the 3nm lateral separation requirement between aircraft is maintained. The site visits consisted of focused interviews with controllers and training personnel as well as Figure 1 depicts an example of an air traffic control observations of live operations. Specific interview cognitive projection model for TRACON questions were created to elicit how the projection controllers. In this model, information is fed into was accomplished under different operational the controller through Perception, primarily circumstances (e.g., “How do you determine if two through the radar screen and the VHF radio aircraft will be separated at a particular crossing communication. This information is then point?’ and “How do you determine if an aircraft Comprehended in relation to the goal-relevant will meet the 15 minutes-in-trail restriction?”) tasks of the controller. The controller then Projects the aircraft into the future, using information about the aircraft’s COGNITIVE MODELS current position, intended trajectory, and the point Cognitive models based on a conflict projection of interest to which the projection is to be made. task were created for the TRACON and oceanic air This information is fed into the working mental traffic controllers, which was developed These model of the aircraft. The Working Mental Model models incorporate the Situation Awareness is created based on the expected behavior of the concept presented by Endsley (2000) and the aircraft given the attributes observed in the decision processes presented by Pawlak (1996). environment and the behaviors that the controller These models were then evaluated against and associates with those attributes. Information about modified based on actual conflict projection tasks behaviors associated with attributes is stored in the verbally explained by the air traffic controllers. Knowledge Base of the controller. The projection TRACON Environment process results in a estimation of future spatial To consider the TRACON projection process, it is position on the radar screen relative to another useful to discuss the process in terms of a particular aircraft due to the primary task of maintaining projection example. In the final approach control minimum separation requirements between aircraft. Figure 1: Example model of TRACON projection process. Because the TRACON environment requires communicate aircraft position and clearances to and precise projection and control, detailed transitional from the aircraft on high frequency (HF) due to the behavior models are required to make adequate lack of very high frequency (VHF) coverage over projections for the controller’s task. For example, the oceans. Due to the difficulties in surveillance controllers developed discretizations among aircraft and the third-party involved in communications vertical transition behavior based upon whether the with the aircraft, the oceanic controllers are unable aircraft is a propeller aircraft, a new jet, or an old to make the precise projections and control jet. Observed pilot behavior, wind information, commands that TRACON controllers are able to airline information and equipage information can make. The separation requirements reflect this also provide observable attributes on which to base difficulty-the average separation requirements the working mental model. over the oceans are 50-100 nm laterally and 1000- The projection resulting from the Situation 2000 ft vertically. In the North Atlantic oceanic Awareness component of the controller’s cognition airspace, the lateral aircraft routes are structured to is then fed into the Decision Processes. The maintain this minimum lateral separation and there Decision Processes are monitor, evaluate, and plan is little deviation from these preferred “tracks.” functions. Because of the communication and surveillance Metering can be used in the TRACON constraints and the tracks structure, oceanic environment, and this traffic initiative imposes a controller projection over the North Atlantic is a minutes-in-trail requirement upon longitudinal significantly more procedural task. For example, separation between aircraft rather than the usual before an aircraft enters a Reykjavik oceanic sector, miles-in-trail separation. Because of the natural its flight strip appears in the top area of the mapping of spatial separation requirements to electronic flight strip bay depicted in Figure 2. The surveillance by the radar display, TRACON oceanic controller then drags the flight strip to the controllers will often project the separation in terms altitude grouping at which the aircraft is flying. All of spatial distance (e.g., 5 nm) and then convert the of the flight strips are grouped initially by cleared distance to a time through a mental heuristic (e.g., altitudes
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