Increased automation of air traffic management, on the ground and in the air, will be a driving force for future change

Like a colossus, the controller walks around her sector, keeping watch on arrivals and departures in the terminal area. Around her a myriad of miniaturised aircraft, holographically replicated in time and space, move towards the final approach path along glowing grid lines projected against a dark background.

Others pass briefly through the controller's view after take-off as they speed on their way towards cruising altitude. With a single stride, the controller can cover 5km (3 miles) and view the terminal area from a completely different angle if necessary.

Unlike her 20th century predecessors, this controller hardly speaks to any of the targets under her watch. Approach and departure flows are carefully automated, but there are occasional airspace issues to resolve. Mechanical failures are virtually unheard of, and aircraft enhanced vision systems ensure that weather is hardly ever a significant factor. The biggest issue is the sheer volume of traffic, and her prime purpose is to intervene the second any perturbation threatens to disrupt the smooth flow.

This advanced virtual reality scenario, familiar to fans of Star Trek and its holodeck (or holographic environment simulator), could be one direction that air traffic management (ATM) will take in the 21st century. Increased automation, both in the air and on the ground, will be a driving force for change, says NASA, which is working with the US Federal Aviation Administration and industry to pioneer new concepts for the safe transition to free flight. Some of the basic steps towards this vision are under way thanks to various initiatives such as the Center-TRACON Automation System (CTAS), and FutureFlight Central - a simulated tower built by NASA to solve capacity problems of future airports.

Fuzzy reasoning

CTAS is a suite of automation tools that essentially help air traffic controllers do their job more efficiently. Funded by NASA's Advanced Air Transportation Technologies project under its Aviation System Capacity programme, CTAS generates advisories that help controllers handle complex ATC situations in real time. A principal aim of the system is to lower the stress on air traffic controllers and to give them more time to think strategically about the traffic situation. As the bottom line is likely to be no less important in the 21st century than it was in the last, CTAS will also have a financial benefit. The system is expected to increase airport efficiency by reducing delays which, in 1998, cost US airlines around $4.5 billion - of which only $1 billion was attributed to weather.

CTAS is basically a software suite that combines radar data, controller inputs, airline preferences, flight plans and weather data. Using expert system and fuzzy reasoning technologies, it is able to crunch the data to make intelligent ATC decisions. CTAS is made up of more than 500,000 lines of software running on a distributed network of Sun workstations. Described by one FAA official as "the most important advance in air traffic control since radar", the first elements of CTAS are already in place at two major US sites: Dallas/Fort Worth, Texas, and Denver, Colorado.

One CTAS tool, the Traffic Management Advisor (TMA), helps regulate flow into the terminal area, and uses "smart" algorithms to anticipate future demand. It optimally sequences and schedules traffic through "arrival gates" at the TRACON boundary and, since the start of operational testing at Dallas/Fort Worth, has reduced inbound delays by more than 2min per aircraft and increased capacity by 5%.

Understanding controllers

"We have been creating tools to assist controllers. The key is assist, and not replace," emphasises NASA's Len Tobias. "We really need to understand how controllers solve problems, so we are using knowledge-based engineering to assist us. The controller has to be right on the money, and that takes a while to achieve through training and building experience. These things are hard to define so we use a mathematical system called fuzzy logic which works with fuzzy reasoning," says Tobias. The result, he believes, will be building blocks towards automation in the future.

"Complete automation may not happen for a very long time because first you have to understand how controllers work," he says. "Automation will not be possible without taking the intermediate steps of understanding how the system works, and how controllers work within that. Once you start to get that understanding, you can begin to develop a framework in which automation will be possible with a variety of fully integrated tools".

Another CTAS element is the Final Approach Spacing Tool (FAST), which helps controllers optimise traffic flows on to runways to cut delays and increase throughput. In trials at Dallas/Fort Worth, FAST is computing the most efficient landing sequence, approach spacing and runway assignments. Landing rates have increased by 9-13% as a result. TMA and FAST will gradually be deployed throughout the US airspace system over the next two to three years, says NASA.

Saving time and fuel

Other enhancements are on the way. Direct-To is a point-and-click interface that provides clearance advisories for time and fuel-saving direct routes. Potentially this will save roughly 1,800min flying time a day, or about 2.5 minutes per aircraft, at airports such as Dallas/Fort Worth. Expedite Departure Path, now in early development, will help controllers guide departing aircraft more efficiently to their desired cruise altitude and route.

The Surface Management System (SMS), already tested in prototype form at Atlanta, Georgia, helps tower and ramp operators plan surface operations by providing estimates of aircraft landing time, at-gate times and forthcoming departure loads. In initial trials, SMS reduced average taxi-out times by 1min per aircraft.

With the huge dependence of the airlines on hub operations, the Collaborative Arrival Planner (CAP) is seen as having exceptional potential. CAP takes TMA data and provides airlines with more accurate arrival time estimates and airport landing information. "In the longer term, we are looking at providing more data to enable the airlines to influence the arrival characteristics of their aircraft. In other words, the CAP could be used to prioritise changes at the hubs on a day-to-day basis, and within the day itself," says Tobias.

"Say an aircraft has a maintenance issue, or has a large group of special interconnecting passengers - for example, the Des Moines aircraft may be slotted in earlier because it has a group of 60 singers who are connecting to their international flight - the system would automatically give the aircraft low, medium and high preference ratings," he says. "But it can't tell the controller to do this; it just advises what is doable and what isn't."

The newest tool for future airport planning was inaugurated at NASA Ames, California, in December. Called FutureFlight Central, the joint FAA/NASA project is a sophisticated simulator which enables risk-free operational testing of new airport and ATM technologies without the need to go to a real airport.

"We wanted to build a facility that involved pilots, controllers and ramp operators and this site does that," says NASA's Nancy Dorighi. Sized to replicate towers as large as those at sites such as Chicago O'Hare, FutureFlight Central has three main functions. First, it will be used to quantify new tools and technologies developed to increase airport throughput.

Second, it will simulate airport construction projects, such as new taxiways and runways, and evaluate their effects as well as help develop improved surface procedures. Lastly, it will be used to develop new ground flow procedures, such as two-way taxiways, that are planned to reduce congestion.

Speech recognition

FutureFlight Central will also test speech recognition systems which will be used to issue clearances to aircraft digitally, rather than tie up the already congested radio frequencies. The fully customisable simulator has a 360í, three-dimensional view of the airport projected on 12 screens.

A bank of operators, each "flying" up to 12 simulated aircraft, will represent real-time traffic. "Theoretically we have a 'lights out' tower, in which it will be possible to manage the airport without having to see it," says Dorighi.

In parallel with the windowless tower concept, the site may also test an enhanced vision tower. This will incorporate "see-through" displays on the windows which will combine infrared, millimetre-wave radar and other sensor data with a graphical image of the outside world.

Source: Flight International