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Computer-Related Incidents with Commercial Aircraft

U.S. Air Traffic Control Center Outages and the Advanced Automation System

1996-1997

Synopsis As reported occasionally in RISKS, the U.S. Air Traffic Control (ATC) system has suffered degradation of service and occasionally complete outages, due to power failures and computer problems. Some of the equipment running the Air Route Traffic Control Centers (ARTCCs) is very old, not maintained by the manufacturer any more, and only with difficulty maintained by the user - and many of the skilled maintenance engineers are reaching retirement age. This is the well-known problem of `legacy equipment'.

The FAA's system modernisation effort was started in 1981. The Advanced Automation System (AAS) contract with Loral (formerly IBM Federal Systems Division) was cancelled in mid-1994 because of `schedule slips and cost overruns', and a much-reduced AAS design is being implemented. The NTSB produced Special Investigation Report NTSB/SIR-96-01 on January 23, 1996 in which they assessed the safety implications of the outages and the planned modernisation effort. They found that, despite sometimes severe degradation of service (delays to traffic), for the one-year period from September 12, 1994 to September 12, 1995, there was only one reported `operational error', a loss-of-separation incident, at Oakland Center on August 9, 1995, and that the modernisation efforts were appropriate in their new, evolutionary, form.

The U.S. General Accounting Office (GAO) has also kept a close watch on the AAS. Reports RCED-97-51, Air Traffic Control: Status of FAA's Standard Terminal Automation System Replacement Project, AIMD-97-30, Air Traffic Control: Complete and Enforced Architecture Needed for FAA Systems Modernization, AIMD-97-47, Air Traffic Control: Immature Software Acquisition Processes Increase FAA System Acquisition Risks are available on the WWW. Overviews of what the GAO calls High-Risk Projects, which it considers "at high risk for waste, fraud, abuse and mismanagement" (!), and which include the FAA AAS, are also available: HR-97-1, High-Risk Series: An Overview, HR-97-9, High-Risk Series: Information Management and Technology, and HR-97-2, High-Risk Series: Quick Reference Guide.

A recent perspective on the U.S. Air Traffic Control system, suggesting that the most worrying aspects lie on the human side, in the working conditions of air traffic controllers as air traffic increases, was proposed by pilot and journalist William Langewiesche in the October 1997 Atlantic Monthly article Slam and Jam. Whether one agrees with Langewiesche's perspective or not, he writes responsibly and well, and is a joy to read.

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