Air Traffic Control

During the past year, air traffic control centers have experienced a series of outages, some of which were caused by the Display Channel Complex (DCC)--a mainframe computer system that processes radar and other data into images on controllers' screens. These outages, which were traced to old, out-of-production equipment, have disrupted air traffic, producing costly airline delays because air traffic control centers must reduce traffic volumes to compensate for lost system capability. These outages are likely to become increasingly disruptive as the availability of DCC spare parts and repair technicians shrink. The Federal Aviation Administration (FAA) has made good progress in replacing DCC with an interim system, known as DCC Rehost. Although key acquisition milestones, events, and risks remain, FAA is now on track to deliver promised capabilities ahead of schedule and within budget. FAA's success ultimately depends, however, on how well it carries out key remaining tasks, such as system-level testing, and how effectively it manages known acquisition risks. Two risks associated with upcoming concurrent system-level testing--contention for human test resources and test baseline configuration change control--are not being formally managed, and FAA has few assurances that either risk will be carefully and effectively mitigated.

GAO found that: (1) DCC, built and deployed over 30 years ago, is critical to FAA's ability to display aircraft situational data in five of FAA's 20 air route traffic control centers; (2) DCC is also responsible for most of the major outages at the five centers from September 1994 through May 1996, accounting for about 48 percent of the total number of major outages and nearly 87 percent of unscheduled system downtime associated with these outages; (3) according to FAA, DCC was able to exceed its availability requirement from fiscal year (FY) 1990 to 1993, on average at the five centers, because of heroic maintenance efforts using "chewing gum and chicken wire"; (4) however, it fell slightly short of the requirement in FY 1994 and 1995, and FAA expects availability to decrease further because of shortages of spare parts and experienced DCC technicians; (5) decreases in DCC availability will result in costly delays for airlines and passengers; (6) FAA has made good progress in acquiring DCCR, but much remains to be accomplished; (7) thus far, the fourth and final DCCR software build is complete, and the number of reported software defects, while cumulatively slightly higher than projections, is showing a favorable trend when adjusted for defect severity; (8) also, FAA is ahead of schedule in completing informal system-level tests, formal testing is generally on schedule, and the first site is ready to begin the system acceptance process; (9) DCCR's development has benefitted from formal risk management and quality assurance programs, and FAA has plans in place to accelerate completion of formal system-level tests; (10) contractor financial reports show that DCCR is under spending estimates; (11) in light of its progress to date, FAA has an opportunity to deliver promised DCCR capabilities on time and within contract budgets; (12) the likelihood of doing so can be increased, however, by acting to mitigate two known risks associated with remaining development activities; (13) specifically, FAA's test plans call for conducting three system-level tests concurrently rather than sequentially, as is normally done; (14) by doing so, FAA expects to implement DCCR early; (15) however, FAA is not formally managing two risks associated with DCCR concurrent testing, which are: (a) staffing three test activities at the same time and thus potentially spreading test personnel too thin; and (b) not defining how it will control and synchronize changes to three system test configurations so as to prevent configuration differences among the three during testing; and (16) by formally managing these risks, FAA will greatly reduce the chances of them impeding future DCCR progress.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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