7
Support Functions

The operation of the air traffic control system is supported by training and maintenance. In both cases, technology plays an important role in how the services are designed and delivered. In this chapter we review trends in technology and the human factors questions surrounding the implementation of new approaches.

TRAINING

Technology Advances

Advances in computing and networking technology have expanded the options for training design and delivery. In addition to classroom and traditional simulation facilities (which are dynamic interactive mockups), training is now possible through personal computer-based simulations and by exercises that are embedded in operational equipment. Moreover, the future holds promise for the use of virtual environment technology in both standalone and networked applications.

As noted in the panel's Phase I report, the Federal Aviation Administration is currently examining methods for providing simulations on personal computers. These computers will provide a high-fidelity emulation of the radar and keyboard as they appear in the live environment. Some specific advantages offered over traditional training simulators are that they can be started, stopped, and rewound at any point in the simulation; they can use voice recognition technology to simulate pseudo-pilots, thus saving on personnel to play these roles; they have



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The Future of Air Traffic Control: Human Operators and Automation 7 Support Functions The operation of the air traffic control system is supported by training and maintenance. In both cases, technology plays an important role in how the services are designed and delivered. In this chapter we review trends in technology and the human factors questions surrounding the implementation of new approaches. TRAINING Technology Advances Advances in computing and networking technology have expanded the options for training design and delivery. In addition to classroom and traditional simulation facilities (which are dynamic interactive mockups), training is now possible through personal computer-based simulations and by exercises that are embedded in operational equipment. Moreover, the future holds promise for the use of virtual environment technology in both standalone and networked applications. As noted in the panel's Phase I report, the Federal Aviation Administration is currently examining methods for providing simulations on personal computers. These computers will provide a high-fidelity emulation of the radar and keyboard as they appear in the live environment. Some specific advantages offered over traditional training simulators are that they can be started, stopped, and rewound at any point in the simulation; they can use voice recognition technology to simulate pseudo-pilots, thus saving on personnel to play these roles; they have

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The Future of Air Traffic Control: Human Operators and Automation software that can generate user-friendly scenarios in minutes; and the costs of purchase and operation are lower. Another approach to training that is being actively pursued by the military services is to build training capabilities into operational systems. This approach, known as embedded training, can be used either by interrupting or overlying normal operations, allowing operators to enter the training mode using their own equipment. Embedded training can be used to acquire initial skills or for skill maintenance. According to Strasel et al. (1988), a fully functional embedded training system should: Require operators and maintainers to perform normal tasks in response to simulated inputs, Present realistic scenarios including degraded modes of operation, Provide an interactive capability whereby the system would assess the action of the operator and respond realistically, and Record performance and provide feedback after the session. In the face of increasing automation of the decision making functions of the air traffic control system, embedded training appears to be an extremely useful approach to helping controllers maintain their skills in manual separation of aircraft—a skill that will be called on when an automated system degrades or otherwise forces the controller to function at a lower-level of automation. Such training can be scheduled for periods when regular operations are slow. A number of concerns associated with embedded training should be mentioned. One is that it may cause additional wear on the operational equipment and, as a result, increase the potential for down time and the need for maintenance support. Another is the concern that embedded training must not interfere with operational capabilities or with safety. Yet another is the question of whether the operational system can support embedded training given the requirements for the reliability, availability, maintenance, and staffing associated with training delivery. Good developmental studies can resolve these issues. Work is also being conducted on using virtual reality in training. In 1996, Science Applications International Corporation conducted a review of virtual reality technology and assessed its readiness for use in training for the FAA. A virtual environment system consists of a human operator, a human-machine interface, and a computer. The computer and the displays and controls in the interface are designed to immerse the operator in a computer-generated three-dimensional environment. In a fully immersive system, the user would experience the virtual world though sight, sound, and touch (Durlach and Mavor, 1995). At the current level of development, there is not sufficient knowledge and computing power to create high-fidelity virtual environment that is interactive with the user in real-time. Systems such as SIMNET, which provide real-time interactive

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The Future of Air Traffic Control: Human Operators and Automation training over a computer network, use tank simulators (which provide realistic force feedback) and low-fidelity images. As the virtual environment technology continues to develop, it will open new opportunities for knowledge acquisition and skill training. Hughes Aircraft (1995) has introduced the virtual tower and the virtual controller. The virtual tower is a desktop trainer with a 180-degree field of view of the airport. It includes a radar situation display and training for the following positions: local tower controller station, ground controller station, flight data position, supervisor station, and pseudo-pilot station air/ground. This system runs on a pentium or 486-66 with 32-bit multitasking processors. The virtual controller (Hughes Aircraft, 1995) is based on an extension of video game logic. It is a turnkey system that includes voice communications across all training positions as well as radar data, maps, video overlays, fixes, navigational aids, air routes, airspace sectorization, and weather data. The displays are high-resolution color or monochrome. Scenarios can be built rapidly and, once initiated, exercises can be frozen, reversed, and replayed in every detail. This system can be used as a single terminal facility or as a network. Human Factors Issues The major concern in designing a training experience is how well the knowledge and skill acquired in the training environment transfers to job performance in the operational environment. This has led to a continuing and not yet well answered question regarding the degree of required fidelity or realism. Transfer of training research suggests that single theories of transfer will not hold for both cognitive and motor tasks (Schmidt and Young, 1987). Hays and Singer (1989) suggest starting with an analysis to determine the major emphasis of the task to be trained—if the task is cognitively oriented, it is likely that the training system should emphasize functional fidelity, which refers to the accuracy of representation of the system's procedures. If there are strong psychomotor elements, then physical fidelity should be emphasized. Physical fidelity refers to the accuracy of representation of the physical design and layout of the system. Virtual environment training may be particularly suited to increasing the probability of transfer because of its flexibility and feedback capabilities (Durlach and Mavor, 1995). A more complete discussion of training transfer and the surrounding methodological difficulties can be found in Druckman and Bjork (1994). MAINTENANCE Functionality The equipment, systems, and facilities that support air traffic control and that must be monitored, controlled, and maintained by airway facilities specialists

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The Future of Air Traffic Control: Human Operators and Automation 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. History 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

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The Future of Air Traffic Control: Human Operators and Automation maintainers. This certification responsibility involves the validation by airway facilities specialists that the equipment, systems, and services are performing within specified tolerances—as well as the legal attestation of certification with accompanying accountability. Equipment, systems, and the services they provide (e.g., radar data) can be accepted for use by air traffic controllers only if they have undergone a process of verification followed by formal, written certification. Certification is performed when the equipment or systems are first accepted for use, when they are restored to use after interruption or maintenance, and periodically as scheduled. The increased reliability of computer-based systems and the automation support for diagnostics that are often embedded in such systems offer the following possibilities for certification: extension of the acceptable certification intervals; increasing reliance on the results of built-in diagnostics that can support certification while the equipment remains in operation; more performance of remote certification, replacing the need to examine the equipment directly; and more automated maintenance logging and equipment performance recording. These trends and the application of automation to the certification process must be considered in the light of the current formal procedures for performing certification, defined in FAA Order 6000.15B (1991b) and FAA Order 6000.39 (1991a), which emphasize that the choice of methods used for certification—including the use of available automation assistance—must be left to the professional judgment of the certifying technician. A major challenge in the maintenance context is therefore whether and how to apply automation to such higher level cognitive tasks as estimating trends and predicting, diagnosing interactions between systems, responding to outages that involve interacting system components, and planning maintenance tasks. Such automation would support the turn in maintenance philosophy away from an emphasis on corrective and regularly scheduled preventive maintenance toward an emphasis on performance-based maintenance that takes advantage of automated trend analyses to identify the most efficient scheduling for maintenance to prevent failures. Under the assumption that sufficient automation support will be available, maintenance philosophy is also turning away from concentration on on-site diagnosis and repair of elements of equipment (using local maintenance control centers) toward more centralized and consolidated operational control centers that remotely monitor and control equipment and systems across facilities, accompanied by automated localization of problems to line-replaceable units that are replaced and sent to contractors for repair. The focus on "systems within one's jurisdiction" is being replaced by a focus on sharing of information, resources, and responsibilities across jurisdictions (Federal Aviation Administration, 1995b, 1995c).

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The Future of Air Traffic Control: Human Operators and Automation Human Factors Implementation The maintenance control center (MCC) is the central workstation suite from which maintenance specialists monitor and control the air traffic control system for a given facility or set of sites. The maintenance control center at an en route center, for example, typically consists of an extensive set of separate indicator panels, control panels, keyboards, video displays, and printers that, taken together, provide the capability to monitor and control: radars and radar processing; the HOST components and peripheral devices; computers that process the radar and flight data for presentation at the controllers' workstations; the controllers' plan view displays; communications equipment; and facility environment systems. Because modernization has been accomplished through many different programs in the FAA involving many different vendors of equipment and systems, and because the national airspace system is the focus of rapidly advancing technologies, maintenance specialists face a variety of new technologies, provided by different vendors, with varying levels of automation and different human-machine interface designs. In contrast, the procedures and human-machine interface for air traffic controllers have undergone more controlled growth and change. The specialists who monitor and control the supporting equipment are typically provided with new monitoring and control devices that are tacked onto the array of such devices for other equipment in a loosely arranged maintenance control center that lacks integration (Theisen et al., 1987). The FAA has specified standardized protocols and data acquisition and processing requirements to guide the integration of new national airspace system components and systems in a manner that continues to support the centralized monitoring and control workstations (Federal Aviation Administration, 1994a). However, these and other recommendations (Federal Aviation Administration, 1991a) address only the lower-level automation tasks mentioned above. They do not address the allocation of higher level tasks between human and machine, the integration of automation functions across disparate systems, or the integration of the associated human-machine interface. There appears to be a significant need for the specification of a maintenance control center human-computer interface into which all new designs must fit well, and a corresponding need for an overall maintenance control center automation strategy against which proposed automation designs can be evaluated. These same needs apply to the design of tools that support other airway facilities activities, such as off-line diagnosis of equipment, maintenance logging, and maintenance of software. The ongoing development of the national airspace system infrastructure management system is an opportunity to address this need. It consolidates the existing 79 maintenance control centers into four centralized operations control centers and modernizes the current national maintenance coordination center into a

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The Future of Air Traffic Control: Human Operators and Automation national operations coordination center. It will be automatically fed data from the centralized operations control centers and may include automation enhancements that support prediction, response, and planning tasks. The success of this consolidation and integration effort hinges on the degree to which new systems pass relevant data to the centralized operations control centers, the manner in which automation is applied at the centralized operations control centers and the national operations coordination center to support the cognitive tasks of the maintainers, and the successful application of human factors research and design efforts to the development of effective centralized operations control centers and national operations coordination center workstations. It is therefore encouraging that the FAA Technical Center human factors organization is undertaking research and providing design support for the effort. Human Factors Issues The impact of automation when new components or systems are introduced is often experienced more directly by maintainers than by air traffic controllers. The new components or systems occasionally include increased automation of air traffic control functions; often they represent modernization of aging equipment without significant change to the human-machine interface for the air traffic controllers. In either case, the new systems increasingly include automation of such maintenance functions as diagnostics, fault localization, status and performance monitoring, logging, and reconfiguration using backup components when the primary components fail. Although these automation enhancements are likely to prove transparent to the air traffic controllers, they can impose on maintenance specialists the requirements to learn new and often complex functional and human-machine characteristics of the modernized equipment. Cognitive Task Analysis The FAA has developed detailed job task analyses for maintenance tasks and has applied these analyses to the development of training plans and programs (Federal Aviation Administration, 1993a). The job task analyses have been accompanied by identification of knowledge, skills, and abilities prerequisite for effective task performance, as well as 14 cognitive and sensory attributes of 4 types of task (entry, receipt, analysis, and communication). The cognitive and sensory attributes identified for the national airspace system operations manager are listed in Table 7.1. Table 7.2 provides examples that illustrate the meanings of the cognitive/sensory attributes listed in Table 7.1. These attributes map well to the hierarchy of cognitive functions applied to the summary of automation applications in this report (see the introduction to Part II), as shown in Table 7.3 (which also includes

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The Future of Air Traffic Control: Human Operators and Automation TABLE 7.1 Task Set and Cognitive/Sensory Attributes of the National Airspace Systems Operations Manager Task Set Cognitive/Sensory Attributes Number of Tasks Entry Coding 134 Receipt Movement detection 3   Spatial scanning 34   Filtering 43   Image/pattern recognition 42   Decoding 157 Analysis Visualization 7   Short-term memory 35   Long-term memory 10   Deductive reasoning 107   Inductive reasoning 16   Probabilistic reasoning 43   Prioritization 23 Communication Verbal filtering 132 TABLE 7.2 Examples of Cognitive/Sensory Attributes Attributes Examples Coding Enter information into the maintenance log Movement detection Listen for alarm printouts Spatial scanning Observe status panels for status data Filtering Identify significant status data on status panel Pattern recognition Form mental picture of facility status Decoding Read a facility configuration display screen Visualization Determine operations impacts from weather picture Short-term memory Remember status information to record in log Long-term memory Remember procedures Deductive reasoning Determine that facility data are questionable Inductive reasoning Estimate impact from historical trend data Probabilistic reasoning Evaluate the nature of a degradation Prioritization Establish order for restoring equipment Verbal filtering Identify relevant verbal information

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The Future of Air Traffic Control: Human Operators and Automation TABLE 7.3 Cognitive/Sensory Attributes Arranged by Cognitive Function Hierarchy Cognitive Functions (Higher To Lower) Cognitive/Sensory Attributes Number of Tasks Plan/resolve Prioritizing 23 Predict longer term Inductive reasoning 16 Compare, predict shorter term Deductive reasoning, pattern recognition, probabilistic reasoning, visualization 199 Transmit information Coding, decoding, verbal filtering 423 Remember Short-term memory, long-term memory 45 Identify Filtering, movement detection, spatial scanning 80 summation of the tasks to which the cognitive/sensory attributes were found to apply). The information in Table 7.3 suggests that: Since lower-level cognitive tasks (identifying and remembering) may be presumed to underlie higher level cognitive tasks, the relatively small number of maintainer tasks for which lower-level cognitive/sensory attributes are currently required supports the general conclusion that automation has been widely applied to these lower-level tasks. The relatively large number of tasks for which moderate-complexity (transmit information, compare, predict shorter term) cognitive/sensory attributes are required suggests an opportunity for automation of these moderate-complexity tasks. Although the number of tasks for which higher level (plan, resolve, predict longer term) cognitive attributes are required is relatively small, these tasks may be taken as a critical culmination of the results of lower-level cognitive tasks and represent a significant challenge for future automation. In addition, Blanchard and Vardaman (1994) have developed an outage assessment inventory to study factors relating to equipment and system outages, such as system and equipment design factors; human behavioral processes; personnel factors; logistics factors; and physical environment factors. Expanding Blanchard and Vardaman's work to address cognitive tasks and attributes in greater detail might represent a useful framework for investigating, within the

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The Future of Air Traffic Control: Human Operators and Automation context of a standard maintenance task sequence, variables that may interact with automation to mediate the effectiveness of automation applied to maintenance. Workload FAA maintenance specialists experience sudden transition from low-workload troughs to high-workload peaks. Scheduling of preventive maintenance and certification tasks is currently a commonly applied method to average workload. Maintainers also schedule tasks that affect air traffic control operations in coordination with air traffic controllers, taking into consideration the controllers' workload. The most significant high-workload challenge for maintenance personnel occurs when multiple critical elements fail, creating or threatening service outage. Under these situations, maintenance personnel face the complex task of rapidly diagnosing the cause from the pattern of failures, while simultaneously assessing the progress of the diagnosis, logistics support factors, and the utility of applying alternative solutions to maintain or restore service. Training and Selection Selection of maintenance technicians has been neither centralized nor standardized. Each region hires new technicians by evaluating the experience and education reported in candidates' SF-171 applications against knowledge and skill criteria for the specializations that the regional office requires. These specializations have traditionally included: navigation, communication, radar, and computers. Guidance for the knowledge and skill criteria applicable to each specialization is available in formal qualifications standards and position descriptions. There is no prehire selection test for maintenance personnel. Hirees typically have electronics backgrounds, usually developed in military service and/or through technical education. Until 1994, the focus of electronics specialists was on specific subsystems or items of equipment to which they were assigned. In recognition of the need to develop generalists who focus on system-level functions and the delivery of services across interacting systems, the FAA created the GS-2101 job classification, which emphasizes systems engineering skills. The knowledge, skills, and task emphases of the GS-2101 specialist include: ability to work with automation tools for diagnostics and maintenance, ability to perform centralized monitoring and control, ability to perform system- and service-level certification, breadth of knowledge across systems rather than depth of knowledge of specific items of equipment, knowledge of how information flows between systems, ability to work with information management systems, maintaining end-product services for national airspace system users, performance of independent actions, and ability to work well in interaction with others (Federal Aviation Administration, 1995d).

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The Future of Air Traffic Control: Human Operators and Automation The GS-2101 job classification, which now covers the majority of electronics technicians, is likely to require change in the population from which hirees are selected. There is no known FAA documentation of the strategy for identifying this population or for determining the precise relationship between selection criteria, performance during training, and on-the-job performance. Demographic data for the FAA's maintenance workforce suggest that, within 10 years, there will be a simultaneous retirement of significant percentages of experienced technicians and the equipment on which they have developed their experience (Federal Aviation Administration, 1993b). Whereas this suggests that the introduction of the GS-2101 job classification is quite timely—fostering the hiring and training of new types of people for new types of equipment—it also adds to the urgency of validating the GS-2101 hiring and training devices and procedures. The training process has two goals: (1) certification of the technician's abilities with respect to given systems and equipment, so that he or she may be authorized to certify the systems and equipment for use in air traffic control and (2) career progression of the technician, so that, by demonstrating proficiency, he or she can progress to journeyman status. In principle, these goals are met by providing theory through course material and application through subsequent on-the-job training. There is currently no training track that specifically addresses the position descriptions of the GS-2101; these trainees currently receive tailored instruction selected from among the pool of instructional sources that were developed to train the specialists in radar, navigation, communications, and computer systems. Communication and Coordination Restoration to service of failed equipment, systems, or entire facilities requires close cooperation between maintainers and air traffic controllers, both on-site and across sector, regional, and national levels, because outages at one facility can affect systems and services at other facilities, and because the responses to outages may require support and approval from the other locations. In addition, each maintenance coordination center reports all equipment and system outages and restoration activities to the national maintenance coordination center, whose staff monitor situations and coordinate resolutions with the national, centralized air traffic control system command center. In all cases involving interruption and restoration of items affecting air traffic control, maintainers function in a supportive capacity. Controllers must decide the priorities by which maintainers apply their resources. However, in so doing, controllers must consider recommendations from maintainers that take into account the likelihood of restoring the affected item(s) within desired time frames, the levels of functioning available with degraded equipment, and potential temporary work-around strategies. The outage of automated systems or

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The Future of Air Traffic Control: Human Operators and Automation functions is a problem that must be jointly solved. Such cooperative problem solving is currently addressed by experience and procedures rather than by automated supports, at both the local and national levels. The responsibility for restoration also highlights the need for teamwork within the maintenance organization. Maintainers currently rely on one another's expertise to solve problems. A frequent requirement during restoration is to call back needed off-duty specialists, when those on duty do not possess specialized knowledge to address a given problem. A move toward more breadth of responsibility, as reflected by the GS-2101 job description, may affect the dynamics of such teamwork. The FAA has recently begun to study maintenance teamwork at its Civil Aeromedical Institute in the following areas: knowledge and skills that predict successful membership in and leadership of self-managed teams; tools to assess the progress of work teams; organizational culture factors that inhibit or facilitate acceptance of new technology by the maintenance workforce; and methods for introducing new technology (e.g., quality circles, town hall meetings, goal setting, and teaming). Organization Traditionally, the national airspace system operations manager has been supported by specialists in computer systems, radar, communications, and navigation aids equipment, and these specialists have been supported by hardware and software technicians. National airspace system operations managers have been traditionally selected from among the ranks of specialists whose expertise crosses the computer systems and radar areas. In the past, they have represented systems-level expertise. The reclassification of virtually all specialists as GS-2101 "automation systems specialists" brings into question this traditional understanding of organizational ties and roads to promotion and introduces the possibility of considering new organizational arrangements for maintainers. The primary staffing unit for maintenance technical activities in support of en route and terminal operations is the airway facilities sector, which is staffed as a "self-contained and self-sufficient" work unit. The FAA is in the process of consolidating the 79 existing sectors into 33 system management offices. The planned consolidation of these offices into four operations control centers will introduce a new, as yet unknown, organizational structure. Automation Issues Error Human error, particularly by maintenance staff who control the automation equipment, can cause or contribute to outages. One option frequently considered

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The Future of Air Traffic Control: Human Operators and Automation by maintenance specialists when complex systems demonstrate performance decrements is to do nothing, since experience has shown that frequently performance decrements are transient, and complex systems sometimes salvage themselves. One general rule followed by experienced maintenance specialists is: analyze before you act. This suggests that important features of automation for maintenance are the extent to which the design of the device contributes to system self-stabilization, the extent to which it supports system analysis, and the extent to which it discourages (e.g., foolproofs) human error and recovers from them. Trust Certification provides an example of how questions of trust with respect to automation of maintenance tasks are considered within the FAA. A significant practical consideration is: How does the automation of certification affect legal liability? If automation is relied on for certification and it errs, is it appropriate (legally) to blame the machine or to blame the certifier whose judgment accepted the machine's error? It is important to emphasize that the certification process represents formalization and operationalization of trust. When a maintenance specialist certifies a system, that specialist formally and legally expresses the FAA's conclusion that the system is trustworthy. When the specialist ceases to trust a system, the specialist formally decertifies the system. Therefore, when a certified system fails, the issue of trust extends through multiple orders: the air traffic controllers may question not only their trust in the system and its equipment, but also their trust in the individual(s) who certified the system. This introduces mistrust in the qualifications of the certifier (and therefore in the process by which the certifier was "certified to certify") and in the process of equipment/system certification, which ultimately and formally (by FAA Order 6000.15B) relies on the "professional judgment of the certifier." One response to these concerns has been the suggestion that the certification process should be as automated as possible—in which case the question arises: Who will certify that certifier? A significant question regarding the application of automation to maintenance is: Will the maintenance specialists be able to effectively restore equipment and systems to service when (1) the equipment or systems that have failed contain automation on which air traffic controllers rely heavily to perform their duties and when (2) maintainers themselves rely on automation to perform the restoration, but the maintenance automation has failed or is difficult to work with? Improper design or application of automation to both air traffic control and maintenance can produce a compounding of difficulties that complicates extremely any problems relating to failure of the automation supporting air traffic tasks, as discussed elsewhere in this report.

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The Future of Air Traffic Control: Human Operators and Automation Skill Degradation The rationale for the GS-2101 job classification relies partly on the expectations that new systems are likely to automate current component- and subsystem-level monitoring, diagnostic, and reconfiguration functions and that the systems will be modularized to permit failed components to be removed, replaced with equivalent modules (pull-and-replace maintenance), and returned to the manufacturer for repair. The concern is that these assumptions may lead to the conclusion that the new class of employees can focus on system- and service-level activities, relying on automation to monitor and control lower-level functions—and that training for these lower-level functions can therefore be eliminated. Such ''dumbing down" of training would be suspect in the light of questions about what will happen when the automation fails, and how the GS-2101 will maintain proficiency in the automated tasks. Mental Models There are no known descriptions of the maintainer's mental model of the national airspace system. However, to the extent that maintainers and controllers must communicate on the diagnosis and repair of automated function, as we discuss below, it would appear to be important that they both maintain simulation mental models of the equipment. Communication and Organization Currently, air traffic controllers and maintainers share supervisory control tasks. Controllers monitor and control air traffic patterns and activities. In the process of doing so, they also monitor the apparent quality of the data appearing on their workstations and the performance of their display and control devices. For example, controllers will question the quality of radar-provided data and have limited control over the selection of radar parameters for display. However, it is the responsibility of maintainers to monitor and control all equipment that ultimately supports the controllers, to inform the controllers of the status and performance of equipment and systems on which their tasks depend (including the controllers' workstations), to reconfigure and maintain degraded or failed equipment in a manner that minimizes interference with air traffic control tasks, and to respond to requests for service from controllers. Air traffic supervisory control tasks must therefore be viewed as cooperative efforts of both controllers and maintainers. In addition, controllers and maintainers share the responsibility for installing and evaluating new, increasingly automated equipment as well as software and hardware upgrades to existing equipment. Maintainers have always shared with controllers the responsibility for and the philosophy of maintaining the safe and efficient flow of air traffic; it is open

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The Future of Air Traffic Control: Human Operators and Automation to question whether the maintainer roles within the team will actually increase with increased automation, or whether increased automation will require that the controller roles expand into supervisory control functions currently performed by maintainers. The results of the FAA's recent employee attitude survey (Federal Aviation Administration, 1995e) indicate that maintenance employees report low to moderate satisfaction with the impact of new technologies on their jobs. Attitudes were assessed about whether new technology is appropriate and sufficient, whether timely information on the new technology is provided by management, and whether the organization is generally quick to adopt new work methods. Such attitudes form part of the organizational culture within which user involvement transpires during the acquisition of new systems and users accept or reject new technology. Conclusion The FAA is reconceptualizing its approach to maintenance. This reconceptualization is reflected in several trends: Centralization of monitoring and control functions and capabilities (into work centers, centralized operations control centers, and an overriding national maintenance coordination center). This presumes a significant amount of additional automation to support system-level diagnostics, certification, and restoration after outages. Increased automation of higher level cognitive tasks, permitted and required by the centralization mentioned above, and accompanying large-scale modernization of the technology supporting both air traffic control and maintenance activities. In the past, the focus has been on automating lower-level cognitive functions. Changing roles within the maintenance organization (e.g., the shift away from specialization toward broader systems engineering required by the new GS-2101 job classification); changing roles between maintenance and air traffic personnel, which will result from the movement of maintenance specialists to centralized facilities (e.g., differing lines of communication, possibly different responsibilities). Changing maintenance philosophy toward more preventive and predictive maintenance. Changing culture, emphasizing management and delivery of services to customers (e.g., system reliability and availability maintained for air traffic control) and to internal business managers (e.g., meeting goals for efficient use of resources). This new culture of performance-based management is expected to be fostered

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The Future of Air Traffic Control: Human Operators and Automation by the introduction of supporting automation that includes: shared distributed databases, expert systems, distributed systems, data and telecommunications networks, decision support systems, mobile computing, computer-based planning tools, and simulation and modeling tools (Federal Aviation Administration, 1995c). Adkisson et al. (1994) identified applications of artificial intelligence (e.g., expert systems, artificial neural networks, expert neural systems, fuzzy logic, natural language processing, intelligent databases, distributed artificial intelligence, and machine learning) to such maintenance activities as alarm processing, monitoring, information retrieval, administrative functions, problem resolution, certification, preventive maintenance, and training. There is, however, scant discussion of human factors research in descriptions of these shifts in direction for maintenance.

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