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Involving the Pilot in Air Traffic Control
How much information is enough to give pilots By Jane M. Sanders |
Three jumbo jets are converging on a major airport on different flight paths. Somewhere in between the ground and the sky, air traffic controllers relentlessly dish out commands, knowing those little blips on those little screens represent tons of metal and hundreds of lives.
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Pilots follow the directives, sometimes second guessing the air traffic controllers. But they don't know what's on the screen.
What if they did? Perhaps the efficiency of air traffic management would improve.
The technology is available. Called Cockpit Display of Traffic Information (CDTI), it provides an enhanced cockpit display that allows pilots to see other aircraft around them and the distances between them.
But there's a reluctance to fully implement CDTI in commercial aircraft. So far, only low-end versions of CDTI have been installed in commercial aircraft, primarily to help pilots react more quickly in collision avoidance maneuvers.
"There is a reluctance to implement CDTI because of the procedural changes it would require for both air traffic controllers and pilots," says Dr. Amy Pritchett, an assistant professor in the Georgia Tech School of Industrial and Systems Engineering. "But CDTI would allow controllers to give higher types of commands and communicate more directly with the pilots. For example, instead of just telling the pilot what speed to fly, the controller can also tell them what aircraft they will be following in to land and how far behind them to be. This can give the pilot more involvement in air traffic management."
But there is a fine line between giving pilots the right information and overwhelming them with too much. So Pritchett and her students are conducting studies to help set the standard, in hopes that CDTI will be more widely accepted and efficiency improved.
For now, efficiency of air traffic management is compromised for safety. Historically, controllers have put in extra safety margins between approaching and departing aircraft in case one of them exceeds a specified speed. This has resulted in uneven gaps of time between landings and departures. With CDTI getting pilots more involved, controllers could allow aircraft to fly closer together and maintain a consistent pattern of landing and departing planes, making air traffic management more efficient and safer, Pritchett says.
With CDTI in place, air traffic controllers would continue to monitor aircraft, but not have to give navigational commands every couple of minutes. For example, instead of the controller telling the pilot to adjust his speed to a certain value, the controller would tell him or her to stay 10 miles behind the lead aircraft as they approach the airport.
"It's like the difference between the teacher asking a student to write a paper and then letting them do it instead of standing over them while they do it," Pritchett says.
All of this is contingent upon pilots having the right amount of cockpit display information, and that is the focus of Pritchett's current study funded by NASA's Ames Research Center. She and graduate student L.J. Yankosky have modeled and numerically simulated several different air traffic control procedures that would use CDTI. They also conducted flight simulator experiments with 12 commercial airline pilots examining different CDTI implementations. Now, they are analyzing their data. A final report will go to NASA in early 2000, but preliminary results are giving the researchers insight into CDTI's future.
Cockpit Display of Traffic Information technology would provide an enhanced cockpit display that allows pilots to see other aircraft around them and the distances between them.
(300-dpi JPEG version - 585k)
Modeling and simulation studies led the researchers to this hypothesis: Pilots using CDTI must be able to easily assess speeds of surrounding aircraft to safely and efficiently respond to an air traffic controller's higher-level commands (e.g., stay 10 miles behind the lead aircraft).
The researchers tested their hypothesis with flight simulator experiments involving pilots who ranged in experience from co-pilots on 727s to captains on the newest aircraft types. Pilots flew seven, 15- to 20-minute runs, simulating their arrival at any of four fictitious major metropolitan airports. On the runs, pilots viewed any of three different CDTI displays, offering varying amounts of information. Pritchett posed as the controller, and Yankosky was the co-pilot.
"Pilots had some concerns, depending on how good the display was," Pritchett says. "They liked more detailed information, but with the display presenting the most information, the pilots were concerned that it might be too much. . . . All of the pilots were intrigued by CDTI. But they still want air traffic controllers to be involved -- not to watch them, but to watch what the other guy is doing."
This latter concern resulted, in part, from the pilots' seventh runs, when researchers simulated an "off-nominal" event as two streams of air traffic merged and approached the airport. The "controller" asked the pilot to stay four miles behind the lead aircraft. Meanwhile, the other aircraft slowed 50 knots more than it should have.
"In the display without the information on the other aircraft's speed, it was hard for pilots to react to this situation," Pritchett says. "But they reacted quickly when they had this information."
Pritchett presented the research results in October 1999 at the AIAA/IEEE/SAE Digital Avionics Systems Conference. She hopes the results will assist the Federal Aviation Administration in its decision on when and whether to fully implement CDTI in commercial aircraft. Pritchett believes that approval could come within the next five years.
"Things are ripe for change in air traffic control," Pritchett says. "Equipment is antiquated. There is concern about change. But there must be change because of the equipment and the demand for air transportation."
Pritchett sees the implementation of CDTI in commercial aircraft as an intermediate step in changing technology and air traffic control procedures. Beyond it is the concept of "free flight," which would allow pilots to select their routes based on daily conditions. For now, controllers select routes often based on old airways and without considering conditions, such as winds.
"CDTI is a good intermediary step because air traffic controllers will overall still be in charge," Pritchett says. "They will just be able to give higher-level commands."
In addition to CDTI's potential for improving the efficiency of air traffic management, Pritchett believes its implementation could increase air traffic safety. With CDTI, pilots have a better chance of knowing if air traffic controllers or other pilots might be making mistakes. It could help pilots see a problem forming 10 to 20 minutes before a potential mid-air collision occurs. Still, CDTI is so novel, it will take time to be accepted, Pritchett adds.
For now, CDTI is being tested by the Cargo Airlines Association, which typically involves aircraft flying in off-peak periods and without passengers. CDTI has been used in military aircraft, which are equipped with complementary radar displays, for a number of years.
photo by Stanley Leary
For more information, you may contact Dr. Amy Pritchett, School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0205. (Telephone: 404-894-0199) (E-mail:
amy.pritchett@isye.gatech.edu)
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Last updated: February 10, 2000
