include: equipment internal to facilities (e.g., flight and radar data processors, displays, and workstation devices); equipment that interfaces with the facilities (e.g., radars and communications equipment); and airport local equipment (e.g., runway lighting, local navigation aids, and instrumentation). Automation has been increasingly applied, at varying levels, to the following maintenance tasks: monitoring of equipment status, configuration, and performance; control (including adjustment and configuration); diagnosis of hardware and software problems for equipment and some subsystems; restoration of equipment and some subsystems experiencing outages; validation that equipment is ready for use in air traffic control; logging of maintenance events and related data; and supporting aircraft accident and other incident investigations.
Automation and computer assistance are applied at different levels in different systems. Automation has been widely applied to maintenance activities through built-in equipment-level diagnostic tests and off-line diagnostic tools. A logging system that prompts the manual entry of maintenance and incident data supports both maintenance and incident/accident investigations. In general, automation and computer assistance are provided to support such functions as information retrieval, alarm reporting, remote control, and data recording. Only rarely is automation used to perform such higher level cognitive functions as trend analysis, failure anticipation, system-level diagnostics and problem determination, and final certification judgments.
Historically, the application of automation to relatively lower-level cognitive tasks has been supported by FAA policy. Federal Aviation Administration Order 6000.30B (1991d) and Order 6000.39 (1991a) establish a long-term policy for national airspace system maintenance by recommending that automation be applied to repetitive maintenance tasks and that the airway facilities specialist be left ''free to accomplish higher level, decision-oriented work" (p. 5).
However, changes in this policy have been spurred by recent programs aimed at modernizing the air traffic control system and introducing automation on a large-scale. These modernization programs include the advanced automation system (AAS) and its progeny: the replacement of the en route HOST computer; the display system replacement (DSR), which modernizes en route processors and workstations; the standard terminal automation replacement system (STARS), which modernizes the automated radar terminal system processors and workstations; and the tower control computer complex, which modernizes tower processors and workstations. Each of these systems includes new distributed architectures, networks, and built-in automated features that diagnose system faults and perform online reconfigurations to maintain system availability.
Formal certification of national airspace system equipment, systems, and services is an especially critical procedural and legal responsibility of system