Exploring ADS-B Technology

MITRE's Aviation Center Joins the FAA and the Cargo Airline Association to Improve Airspace Safety and Efficiency

November 2001

Hardly a day passes without the aviation community's getting slammed in the media for inefficiencies, lost baggage, and the delays that have become all too commonplace for airline travelers. Over the past five years alone, airline delays have increased by 58 percent according to U. S. Department of Transportation statistics. To help turn things around, The MITRE Corporation's Center for Advanced Aviation System Development (CAASD) is working closely with the Federal Aviation Administration (FAA), as well as with passenger and cargo airlines, advisory groups such as RTCA, and others in aviation research and development.

One promising research area that CAASD has been working in involves Automatic Dependent Surveillance-Broadcast (ADS-B) technologies and applications. In essence, ADS-B uses Global Positioning System (GPS) satellite data to provide specially equipped aircraft with an array of information displayed on the instrument panel that helps pilots "see" other equipped aircraft (or ground-based vehicles). The display enables the pilot to visualize where his aircraft is in relation to other aircraft in the immediate area. The same information is transmitted to other equipped aircraft in the vicinity and to air traffic controllers via digital broadcast datalink, enabling radar-like air traffic control (ATC) services in non-radar areas.

OpEval-2: Progress One Step at a Time

In October, the Cargo Airlines Association (CAA) and FAA conducted the second in a series of Operational Evaluations, (OpEval-2) at Louisville International Airport (Standiford Field). This followed the successful OpEval completed in July 1999 in Wilmington, Ohio, that also explored ADS-B technologies.

At OpEval-2, participating aircraft and an ADS-B-equipped surface van transmitted real-time GPS position information via datalink to other aircraft and to ground-based ATC equipment. The evaluation included multiple day and night flight and surface movement scenarios using 17 commercial, private, and government aircraft. The fleet included five UPS and FedEx Boeing 727 air freighters, three FAA aircraft from the William J. Hughes Technical Center in Atlantic City, NJ, a wide range of business and general aviation jet and propeller aircraft, and a van. Pilots using avionics developed by several manufacturers provided valuable human factors data on the use of ADS-B in the cockpit. Louisville air traffic controllers, observing the ADS-B data that was integrated into the FAA's terminal automation system at the Louisville Terminal Radar Control (TRACON) facility, also provided human factors data.

This is an instrument panel with the Cockpit Display of Traffic Information (CDTI), the rectangular module in the upper right. As configured here with a moving map of the runways, the CDTI helps the pilot "see" where he is on the runway, and locates other ADS-B– equipped vehicles.

The ADS-B equipage consists of a digital datalink transceiver that sends the aircraft's identification, location,

and altitude at 1-second intervals and receives data from other equipped craft. A processor sorts the "targets," which are then visually presented on the controller's screen as well as on a CDTI (cockpit display of traffic information).

While the first OpEval tested equipment operability and human factors issues associated with the hardware and led to certified applications for "enhanced see-and-be-seen awareness," OpEval-2 built on those results in showing how ADS-B could be used operationally both within the designated airspace and on the airport surface. The aim was to demonstrate how advanced technologies and newly developed air traffic procedures could improve flight safety and at the same time increase capacity at hub airports. The test scenarios focused on optimizing final approach and departure spacing to maximize runway capacity and on enhancing airport surface safety using moving maps to improve situational awareness.

The Louisville exercises relied on the collaboration of pilots, air traffic controllers, human factors engineers, dispatchers, and a host of others from the FAA, the CAA, Lockheed Martin, NASA, MITRE/CAASD, UPS Aviation Technologies, and other organizations. All together, pilots flying everything from sleek business jets and commercial cargo jets to small piston-powered single- and multi-engined aircraft, accumulated more than 100 hours of flight time between October 26 and 30, 2000.

As the runway/taxiway markers in the foreground suggest, sometimes it's hard to know just where you're located on the tarmac. Had the pilot of this Convair 220, holding short of Runway 17R, been ADS-B–equipped, a moving map display on the instrument panel would have shown him precisely where he is on the tarmac.

Significantly, OpEval-2 was conducted in "real time" under various weather conditions during the day and at night using ADS-B in a number of different scenarios. While the gains associated with optimizing approach and departure spacing may seem small—saving a few seconds here and there—when these gains are plugged into a full daily cycle and annualized, they may well translate into major savings for the airlines. And in the case of the second major goal, namely, enhancing situational awareness on the airport surface, the FAA is aggressively looking for new ways to reduce runway incursions, which, in spite of increased effort by the agency, have continued to grow. In fact, as FAA Administrator Jane Garvey recently said,

"We now know that taxiing on the airport surface is the most hazardous phase of flight... today the FAA is committed—as we have never before been committed—to improving runway safety."

Equally important in OpEval-2 was the evaluation of air traffic controller use of ADS-B in the terminal environment, including the development and evaluation of procedural changes and air traffic controller scopes needed to support certification and operational approval for ADS-B. Assessing the response of air traffic controllers in using ADS-B in all air traffic control applications will be critical to operational acceptability of these applications.

CAASD's Role in OpEval-2

Much of the initial planning for OpEval-2—and also for the first OpEval—was done on the McLean, VA campus of CAASD. An industry/ government team known as the OpEval Coordination Group (OCG), co-headed by representatives from CAA and the FAA's Safe Flight 21 office (SF-21), planned virtually every aspect of the event, from the highly detailed safety and operational planning to the debriefings that followed each exercise. The objectives for OpEval-2 included the evaluation of the avionics and procedures needed to support operational approval for each of the CDTI applications of OpEval-2—approach spacing, final approach/runway occupancy awareness, airport surface situational awareness, and departure spacing. Another major objective for OpEval-2 was the evaluation of air traffic controller use of ADS-B information on their ATC displays focusing on these same CDTI applications. CAASD played an important role in establishing flight profiles, in collecting and interpreting data, and in establishing test matrices.

MITRE's CAASD staff was well represented at the operational evaluation held at Louisville International Airport in October. Of the 17 persons gathered in front of a beautifully restored P-51 Mustang, nine are licensed pilots, with ratings ranging from private and commercial pilot to certified flight instructor.

For the initial training, simulations were carried out in CAASD's I-Lab where flight crews manned CAASD's flight simulator and controllers operated simulated ATC automation at other stations in the lab. On site in Louisville, MITRE researchers teamed up with researchers from the FAA's William J. Hughes Technical Center, the FAA Civil Aeromedical Institute, NASA, the Department of Transportation's Volpe National Transportation Systems Center, the Johns Hopkins University, and others to collect data at the Louisville TRACON on the effect of CDTI applications on ATC operations and the usability of SF-21 displays. Their observations and comments were recorded during each of the flight periods, following which were debriefings in which participants discussed each flight period in detail. At the same time, data was collected from the Standiford Field Tower, with monitors observing tower procedures and communications during the flight sessions. (One observer was assigned to monitor ground control while another monitored local control.)

Human factors personnel also served as observers on board aircraft, collecting data during each flight. They were trained on how to collect data and what to collect, and had the additional task of interviewing flight crews after flight sessions were completed. In addition to this information, a wealth of data—video tape, occulometry, and various anthropometric measurements—was collected.

Aside from helping develop the demanding technical requirements for such a complex series of events, CAASD plays another role that is equally essential. As lead engineer Oscar Olmos summarized it,

"We're essentially the bridge between the FAA and industry. We build consensus. Air Traffic Control has their ideas, the Cargo Airlines Association has theirs, and we act as the conduit, bringing everything together. For example, in mapping out procedures, we were able to bring pilots and controllers to the table and in our labs. We got their input on the flight profiles, and, with simulated ARTS [automated radar terminal system], we were able to prototype what we wanted to test in the field.

Of course it helps that we're seen primarily as engineers and researchers with no vested interest in the outcome. That doesn't mean it's been easy. The CAA—pushing the envelope, in effect forcing the FAA to answer hard questions—has caused growing pains, but we're breaking the mold. In the old days, you'd work on something a long, long time and take more time to field it. Now, we're working to establish an initial set of capabilities and get it into the field in a fraction of that time."

One measure of OpEval-2's significance was FAA Administrator Jane F. Garvey's visit during the "public day" ceremonies. In spite of a morning speaking engagement in New Orleans, the Administrator flew to Louisville, took a demonstration ride in one of the FAA aircraft, and held a press conference. In addition to underscoring the promise of such new technologies as ADS-B, Ms. Garvey commented on how pleased she was to see the results of the broad collaboration taking place at Louisville. She also noted the need on the part of the agency to streamline the certification process to accommodate a new way of developing operational capability.

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