Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90)

The proceedings of the SOAR workshop are presented. The technical areas included are as follows: Automation and Robotics; Environmental Interactions; Human Factors; Intelligent Systems; and Life Sciences. NASA and Air Force programmatic overviews and panel sessions were also held in each technical area

Human-centered automation of air traffic control operations in the terminal area

Cover titleNovember 2, 1994Series statement handwritten on coverProposal for the Interdepartmental Doctoral Program in Human Factors and AutomationIncludes bibliographical references (p. 70-73)Introduction: Air Traffic Control operations are described extensively in the ATC manuals such as the Airman's Information Manual [1] and the ATC Controller's Handbook [2]. Mathematical analysis has also been conducted for the ATC operations as evident in the many theses that have been published in ATC research [3, 4, 5]. A brief description is due here however in order to provide a background for the following document. There are six major ATC functions in the terminal area and a summary of their description in Sadoune's thesis [5] follows: Flow Management: The flow management purpose is to provide efficient transition between the en-route corridors and the terminal area through the metering fixes. The en-route corridors are the airways connecting the airports, the terminal area is the designated space around the airport, and the metering fixes are the points at which aircraft enter the terminal area under the flow control process called metering. The flow management system is capable of delivering the aircraft to the metering fix at predetermined time, altitude, and speed, minimizing fuel consumption and flight time. Beyond the metering fix however the concern in no longer fuel and cost, it is the separation between the aircraft and the landing schedule. Ground-based flight path generation is needed at that point. Runway Scheduling: The runway capacity is the limiting factor of the flow of traffic at congested airports. There are many reasons why runways are not used efficiently in the current tactical practice. These include the independent scheduling of landings and takeoffs, the ad hoc fashion in which takeoffs are inserted between landings, and the common use of the first-come-first-serve approach which is fair but not optimal. Runway scheduling is a queuing process and can be optimized for maximum throughput, long term service, and minimum delays of aircraft, taking into account fuel consumption, duration of flight, and other factors. The difficulty is in the dynamic nature of the schedule where modifications are needed as new entrants arrive or as environmental conditions change. The determination of the runway capacity and its improvement through the use of advanced technologies are discussed in Flow Control: Through traffic redistribution the flow control process helps smooth the demand fluctuations leading to a controlled number of aircraft simultaneously present in the terminal area. Two processes accomplish flow control: metering and holding. Metering divides the approach to the airport into successive stages between metering fixes. The flow management system delivers the aircraft to the metering fixes at the predetermined time, altitude, and speed. Holding points are assigned where holding aircraft are stacked and isolated from traffic. Holding aircraft circle in holding patterns awaiting landing clearance. Therefore, while metering moves the delays resulting from the runway capacity upstream, holding extends the flight path in time to accommodate arrival delays. These practices however can result in idle runway time in favor of more flow control leading to less efficient use of the runway. Flight Path Generation: There are standard routes both from the terminal area entry points to the runway for approach and from the runway to the en-route corridors for departure. These predefined routes can be used at low traffic flow rates, and add to the precision since automatic flight control systems are capable of flying along them automatically. However they are not optimal in using the space, or in exploiting the aircraft capabilities, or in maximizing the runway capacity. Automated flight path generation allows the incorporation of the space organization, the ATC separation criteria, the landing and takeoff schedule, the aircraft dynamics and performance limitations, and the maneuvering characteristics of the pilot in generating more optimal and flexible paths. This subject will be emphasized further in this document. Path Conformance Monitoring: In order to supervise the execution of the flight path plan, the radar surveillance system provides vague and non-precise measurement of the position of the aircraft. The controllers base their estimates of the conformance on 2-dimensional radar displays, and have to wait few intervals to estimate the direction of the aircraft. To adjust for the path conformance error the controllers issue heading, altitude, and speed clearances (vectors) to the pilots. Communication between controllers and pilots is done via radio transmission. Errors result from misunderstanding between the pilot and the controller, pilot response, as well as wind and unexpected atmospheric disturbances. Again new technologies and more automation are expected to improve the path conformance capabilities. These include better surveillance using satellites, digital data links for communication between the controller and the pilot, and display of the path to the pilot on board the aircraft. Questions of resolution and threshold of the conformance error become critical to the automation of the monitoring function. Hazard Monitoring: This includes detecting possible collisions between aircraft and with the ground. There is a trade off between false alarms and missed alarms in setting the threshold for the hazard alarm. Namely the more conservative the alarm threshold is set, the less is the risk of collision due to a missed alarm. But the disturbance to the traffic flow caused by the large number of false alarms is higher