ChallengeBy Edward Cone | Posted 2002-04-08 Email Print
Its tortuous route to modernizing air traffic control systems has cost the Federal Aviation Administration billions. Has the agency finally learned its lessons?: Fixing System of Systems">
Challenge: Fixing System of Systems
The challenge is immense.
Current air navigation systems are organized by assigning planes to preset flight paths, defined by a series of radio beacon codes; flight progress is monitored by radar, with controllers speaking instructions over radio. The FAA would like to move to a system that makes more use of satellite-assisted navigation, giving pilots moving displays of the other planes in their vicinity, and decreasing reliance on voices by adding a digital data link between controllers and pilots.
First, the agency has to break free of the limitations of systems designed in the 1950s and '60s. For example, one of the backbone systems, the Host Computer System, continues to run on software written in a dead mainframe computer language, Jovial, and even those scarce Jovial programmers still working have a hard time navigating all the patches that have been applied to the software over the years.
The system has been upgraded by adding new mainframe hardware, and a new front end was added through a project called the Display System Replacement (DSR) that gave the controllers Unix-based workstations.
Host is one of many systems that was supposed to be replaced by AAS, but the agency is only now ramping up a replacement project. Under the FAA's new strategy of proceeding a step at a time, replacing an old mainframe system that still basically works just hasn't been a priority.
The air traffic control system is really several interlocking systems. Airport tower controllers are in charge of landing, take-off, runway assignments, and preventing collisions on the ground.
Flight arrivals and departures are managed by Terminal Radar Approach Control facilities (TRACONs), which track and direct planes from just outside the range at which they are visible from the tower (about 5 miles) to a range of 40 or 50 miles. Although a TRACON is typically located at a major airport, TRACON controllers also have to worry about traffic bound for smaller airports in their region, helicopter flights over nearby cities, and so on.
For years, TRACONs have used the computer system called ARTS that was originally built by IBM and is now in the hands of Lockheed Martin, which acquired IBM's old Federal Systems business. The replacement for ARTS, Raytheon's STARS, wound up running about four years behind schedule.
Both ARTS and STARS track arriving and departing flights using radar data, display the position of each plane on a controller's screen, and help with the process of making sure planes don't get too close together. There are many versions of ARTS in use, including some with updated color displays that rival those offered by STARS, but STARS is supposed to provide one common replacement system that makes more use of open standards like Unix and off-the-shelf hardware. <[>As a departing flight moves away from the airport, TRACON controllers take it to the edge of the area they control and hand it off to the next control center in its flight path. Usually, for a cross-country flight, that's an En Route facilityone of the air traffic control centers that specialize in managing the long-haul portion of a flight.
Here, the key computer systems are Host, the legacy back end, and DSR, the more modernized controller's workstation. It's also where URET is being deployed, as a sort of sidecar to DSR for the second member of a controller team. While one controller watches the real-time radar monitor, his partner uses URET's 20-minute projections of flight paths to detect and avert conflicts that would put one plane into the path of another.