Reprinted with the permission of the Air Traffic Control Association, Inc., 2300 Clarendon Blvd., Suite 711, Arlington, VA 22201.
Contributors are expressing their personal points of view and opinions, which are not necessarily those of their employers or the Air Traffic Control Association. Therefore, the Journal of Air Traffic Control does not assume responsibility for statements made and opinions expressed. It does accept responsibility for giving contributors an opportunity to express such views and opinions. Articles may be edited as necessary without changing their meaning.
The Journal of Air Traffic Control
April-June 1996
Vol. 38 No. 2
FAST Times at DFW
by Ron Nichol
ADSYSTECH, Inc.
On January 25, 1996, at 12:10 a.m. (0610 UTC) DFW TRACON (Terminal Radar Approach Control) controller John Nowakowski accepted a handoff from Fort Worth Center over the Scurry (southeast) cornerpost on BVN7403 (radio call-sign Show Me), a cargo-carrying Cessna 210. Everything about this activity was routine except that the ARTS (Automated Radar Terminal System) tag included information that had never been provided to a controller in a live-traffic environment before. "Show Me" 7403's ARTS tag had a sequence number and runway assignment on the third line of the data block. The FAA-sponsored and NASA-developed Final Approach Spacing Tool (FAST) was operating in the first shakedown test in the DFW control room. Within minutes of John's acceptance of the handoff on "Show Me", area supervisor Mike Prichard and controller Ray Ellison were working American, Delta, Federal Express, United Parcel Service and TWA aircraft inbound to DFW that were also assigned sequence numbers and runway assignments by FAST.
For the better part of six decades, air traffic controllers have not only been responsible for providing separation for the aircraft under their control, they have also been required to make almost continuous tactical decisions on arrival sequences, and in many cases, runway assignments. Due to the constantly changing traffic picture and merging flows at busy airports, controllers may often have to wait until the aircraft are within 10-miles or so from the runway before a final sequence is established. Last-minute runway/sequence changes are usually made to "fill a hole" or take advantage of some other opportunity to expedite traffic. An unfortunate by-product of the changes is increased workload in the cockpit for crews who have to make adjustments when they [are] relatively close-in to the airport.
These tactical decisions by controllers have become increasinglycritical in recent years with the advent of the hub and spoke system in use by most of the major airlines at the busiest airports. Large banks of aircraft are scheduled to arrive within a relatively short time span and highly efficient use of the airspace and available runways is essential for the airlines to meet their schedules and make optimum use of their gates. The men and women of the ATC system have responded magnificently to the demands placed upon them by these arrival rushes, but clearly there had to be a way to make use of the automation tools that were becoming available to help them to focus on their principal role of providing a safe and orderly flow of traffic.
Approximately five years ago, NASA and FAA entered into a partnership whereby the NASA Ames Research Center located on Moffett Field in Mountain View, CA would develop a set of automation software tools, referred to as the Center/TRACON Automation System (CTAS). These tools would be designed to provide controllers with advisories on their radar scopes that would enable them to reduce their workload, enhance safety and maximize the utilization of the available runways through improved balancing and optimized spacing. A team of engineers and computer scientists under the direction of chief scientist Dr. Heinz Erzberger and project leader Tom Davis is now in the process of validating FAST, a key component of CTAS, through operational testing in the field at DFW TRACON.
Dallas/Fort Worth TRACON
The concept of field development is one of the many unique attributes of the CTAS program and the FAST. Initially, a System Design Team (SDT) comprised of controllers, supervisors and staff personnel from a number of large facilities including New York, Los Angeles, Boston, Chicago, Denver and Dallas-Fort Worth was assembled by the Air Traffic Requirements Service (ATR) at the Ames Research Center to provide input to the NASA engineers on ATC procedures. This input provided the basis for the software development. As the project matured, the SDT membership was gradually reduced to include only DFW personnel who participated in approximately one thousand hours of site-specific simulations in the laboratories at Ames and the FAA Technical Center (FAATC) in Atlantic City.
The prototype product that has been developed from the simulations has benefited from continuous input from working controllers who will be the ultimate users of the system. This has only been possible due to the support provided by the Traffic Flow Management Terminal and En Route Product Team that is lead by John Rekstad, the Air Traffic Requirements Service, the Massachusetts Institute of Technology Lincoln Laboratory, and the Southwest Region Air Traffic and Airway Facilities Divisions. The National Air Traffic Controllers Association (NATCA) has also been a full partner in the process at both the local and the national levels. They are represented with two members on the SDT and have participated in a number briefings and demonstrations. DFW Air Traffic Manager Jo-Ellen Casilio, and her predecessor, Larry Viselli, have also been enthusiastic supporters of the field development.
Controllers using FAST at Dallas/Fort Worth TRACON
On February 14, 1996, with the successful shakedown test completed in January, it was time to give FAST its first opportunity to function during an arrival rush. At 6:00 a.m. the specially-trained controller cadre and the NASA engineers gathered to make final preparations and conduct a briefing on fall-back procedures, etc. It was decided to take on the "eight o'clock push." The controllers worked this traffic without any problems and during the debrief, they requested to do it again for the next rush at 9:30 a.m. This also went off without a hitch and during the debrief they pressed to continue the test through what is affectionately known by the DFW people as the "noon balloon."
The "noon balloon" is one of the busiest periods of the day. A heavy influx of aircraft is scheduled to arrive between 11:30 a.m. and 12:30 p.m. placing a strain on Fort Worth Center, which must delay and meter aircraft to the TRACON to meet an agreed upon acceptance rate. The DFW controllers must also cope with this surge in traffic caused by a heavy demand on the runways. In order to provide some relief, the DFW tower usually releases one of the inboard parallel runways, which are normally used for departures, to approach control to provide more concrete for additional arrivals. The trade-off in this scheme is that although the departure demand during this period is relatively low, some departures may encounter brief delays because their runway is being used for landings. During the test it was agreed that approach control would not use the inboard runways at all in order to maximize the pressure on the FAST. The end result was that the FAST performed exceptionally well during this rush at balancing the runways and providing advisories to the controllers on sequences. Feedback from the TRACON controllers, the tower controllers and the traffic managers was highly positive.
This initial operational testing was accomplished on the south flow. The next step was to return to the FAATC for north flow validation, which took place during the week of February 26.
NASA returned to DFW for continuing assessment the week of March 25, and thanks to a strong spring cold front, they were able to "shadow" the FAST in the north flow configuration for a day before beginning operational testing with the controller cadre. The north flow testing also went very well during several rushes, particularly the runway allocation logic which was described by one traffic manager as "impressive." Previous south flow testing was accomplished in mostly VFR weather with three runways available for landing. The weather system associated with the cold front gave FAST the opportunity to function on two runways with both simultaneous and staggered ILS approaches used at various times.
NASA will conduct another four weeks of operational testing between now and mid-May, when they will begin preparation of their assessment report to the FAA, which is due in August. The current testing at DFW is limited to what is now called "Passive" FAST, which includes the runway assignment and sequence number in the data block. Under ongoing development is the "Active" portion of FAST, which will also provide advisories on speed and headings to the controller to assist in spacing the aircraft to meet the FAST-predicted arrival times. These scheduled arrival times are based on highly detailed knowledge of the type of aircraft, weather/wind conditions and landing direction.
The controller is the final authority and always has the option of changing the sequence or runway assignment, when deemed necessary. During simulations, it was common for the controller to question the FAST logic based on what they were seeing on the radar at the time. When they were encouraged to follow the advisories and watch the situation develop, they were usually surprised to see that the CTAS software had been able to evaluate the traffic picture that was beyond their view in Center airspace and the advisories were highly accurate. When CTAS is fully operational, the Traffic Management Advisor (TMA) will begin scheduling the arrival aircraft at approximately 200 miles from the airport. The Descent Advisor (DA) which has been field-tested at Denver Center with cooperating airlines, will eventually be able to provide controllers with the optimum top-of-descent point for the aircraft and conflict-free advisories to the terminal airspace arrival gate. As the aircraft gets nearer to the airport, the terminal radar will take over for the final sequencing based on a scheduled time to touchdown.
Fort Worth Center is serving as the development site for the TMA. Testing of a two-way interface between the Host computer and CTAS has been successfully completed at the FAATC en route laboratory and field-testing with CTAS-derived metering times is scheduled to take place in the Spring through Summer of 1996. Results of that test will be reported here as well.
It's beginning to look like the days when controllers had to make decisions based on what they could see within their 50-mile radar eyes may be coming to an end. FAST times are here!
Ron Nichol is the site coordinator for the CTAS project in the Dallas-Fort Worth area, supporting AUA-540. His prior experience includes controller, FAA Academy instructor, area supervisor, FAA headquarters procedures specialist, and assistant air traffic manager at Bay TRACON. Ron retired from the FAA at the end of 1991 as the air traffic hub manager at Austin, TX. He is currently employed by ADSYSTECH, Inc.
