Jan. 27, 2000 When the teacher gives you a homework assignment, she doesn't usually stand behind your shoulder watching you do it. That would be an inefficient method of teaching.
This analogy applies, however, to the roles of air traffic controller and commercial airline pilot in the arena of air traffic management. Though very safe, the friendly skies aren't always so efficient. But a Georgia Institute of Technology researcher hopes the results of her study on an enhanced aircraft cockpit display system will lead to a smoother-running operation.
The system is called Cockpit Display of Traffic Information (CDTI), and it 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 to 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," said 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 into 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 conducted studies, funded by NASA's Ames Research Center, to help set the standards for enhanced cockpit displays.
Pritchett and graduate student L.J. Yankosky 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 have analyzed their data and are preparing a final report for NASA. Their results are giving the researchers insight into CDTI's future.
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 said. "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 lead 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 said. "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 said. "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 intermediary 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 said. "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 added.
For now, the Cargo Airlines Association is testing CDTI. Cargo planes typically fly 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.
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