4
Flight Information

This chapter provides an analysis of the flight information system in the air and on the ground. We begin with a description of the flight management system, its functions, its history, the human factors issues associated with its development and use, and lessons learned that may be useful in introducing other automated systems. The second part of the chapter presents a discussion of flight information processing through HOST and ARTS and the state of human factors research on flight progress strips, lists, and data blocks.

FLIGHT MANAGEMENT SYSTEM

Functionality

The flight management system (FMS) of a modern jetliner should not be thought of as a mere component or even a computer, but rather as the heart and soul of the plane. The flight management system, along with sensors, system interfaces, and a flight management computer (FMC), produces a full-flight control and information system. This system provides the aircraft with navigational guidance, thrust control, instrumentation (including the horizontal situation indicator map and other modes), vertical guidance, and flight path optimization.

The flight management system contains two flight management computers that operate independently and compare results with each other. Each supports one or more multipurpose control display units, which contain an alphanumeric keyboard and a limited cathode ray tube for text-only display.



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The Future of Air Traffic Control: Human Operators and Automation 4 Flight Information This chapter provides an analysis of the flight information system in the air and on the ground. We begin with a description of the flight management system, its functions, its history, the human factors issues associated with its development and use, and lessons learned that may be useful in introducing other automated systems. The second part of the chapter presents a discussion of flight information processing through HOST and ARTS and the state of human factors research on flight progress strips, lists, and data blocks. FLIGHT MANAGEMENT SYSTEM Functionality The flight management system (FMS) of a modern jetliner should not be thought of as a mere component or even a computer, but rather as the heart and soul of the plane. The flight management system, along with sensors, system interfaces, and a flight management computer (FMC), produces a full-flight control and information system. This system provides the aircraft with navigational guidance, thrust control, instrumentation (including the horizontal situation indicator map and other modes), vertical guidance, and flight path optimization. The flight management system contains two flight management computers that operate independently and compare results with each other. Each supports one or more multipurpose control display units, which contain an alphanumeric keyboard and a limited cathode ray tube for text-only display.

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The Future of Air Traffic Control: Human Operators and Automation The following are the major functions of a flight management system (Honeywell, 1989): Flight planning. Navigational computation of a plane's position. Guidance commands for the autopilot and flight director, in conjunction with integrated thrust management and autothrottle control, to fly optimal vertical profiles while also flying the lateral path. Navigation display data to generate a horizontal situation indicator map display and features. Navigation radio tuning. Storage of database for navigation, aerodynamic, and engine data. Interface to inertial reference system (IRS). Performance optimization. Thrust calculation. Autothrottle control. Polar navigation/operation capability. Simulator capability to allow for simulator training and flight operations. The relevance of the flight management system to air traffic control is threefold. First, as we reviewed in the Phase I report, many of the human factors lessons learned in automation of the flight management system are directly relevant to air traffic control automation. Second, the flight management system provides the aircraft with opportunities to fly extremely efficient user-preferred routes, a source of frustration to the airlines that must often remain on air traffic control-preferred airways. Third, given that the aircraft flight plans are encoded digitally, when linked digitally to the ground by data link, there is the capability to send information downward to air traffic control regarding intent and upward regarding flight control, as well as to share information between aircraft. This enhanced data sharing has profound implications for the future automation of the national airspace system. History In the late 1970s, microprocessor technology had developed to the point at which not only were the electronic devices becoming more and more sophisticated, but also the individual devices could be linked to form a flight management system, rather than a collection of independent, albeit sophisticated, boxes (Billings, 1996b). The individual devices architecture was exemplified by the wide-body aircraft of the period: B-747, L-1011, and DC-10. In these planes, inertial and radio (e.g., Loran and Omega) navigation not only located the plane on the earth's surface, but could also provide guidance commands to the autopilot

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The Future of Air Traffic Control: Human Operators and Automation system, allowing point-to-point steering. Such systems were called generically "area navigation." The aircraft of the next decade took this a great step forward: the flight management systems that appeared on the B-767 in 1982 provided the functions listed above, tying together for the first-time navigation (vertical and horizontal), thrust control, data storage, optimization, and in the extreme, autoland. Billings (1996b:40) referred to this as a "fundamental shift in aircraft automation." For a more complete history of aircraft automation, see Billings (1996b:Part 1). The autoland system in the modern jet airliner is a combination of a number of systems. These include autopilot, autothrottles, the flight management system, and instrument landing system. The airport and its instrument landing system must have special equipment that is rigorously certified by the Federal Aviation Administration (FAA) in order to permit aircraft to land under low-visibility. During the cruise phase of the flight, the autopilot is very precise in maintaining altitude and track. During an autoland, both track and height above the ground are even more precisely maintained. In the aircraft, the autoland system is normally selected by the pilot approximately 5 miles from the landing. Human Factors Implementation It is difficult to speak of the implementation of the flight management system as a single system, because one would have to include the entire flight regime (and some ground regime) of the aircraft. Numerous authors have written on the human factors implications of cockpit automation (see, for example, Wiener and Curry, 1980, for an early warning on the possibility of negative as well as positive consequences). In the mid-1980s these authors concentrated on field studies on various models (Curry, 1985; Wiener, 1985, 1989), and later in that decade Sarter and Woods began their highly prolific collaboration in applying cognitive engineering to the automated flight deck (e.g., Sarter and Woods, 1994, 1995a, 1995b). All these authors wrote of both positive and adverse consequences. The adverse consequences include mode confusion, excessive head-down time, an invitation to large errors ("blunders"), automation-induced complacency, possibly diminished situation awareness, lack of an operational doctrine to govern usage, unpredictable workload, and others. Furthermore, the air traffic control systems of today are not cordial to the advanced aircraft. Wiener (1988) stated, "years from now we will look back and call this the era of clumsy automation," clumsy in the sense of hard to operate, error inducing, and at times workload inducing. Human Factors Issues Because of the central position of the flight management system in the advanced cockpit aircraft, it is not possible to review all human factors issues. We

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The Future of Air Traffic Control: Human Operators and Automation will take note of three basic and important issues: workload, head-down time, and cockpit communication. Readers who wish more comprehensive coverage are directed to papers and reports by Billings (1996a, 1996b), Sarter and Woods (1995b), and Wiener (1988, 1993). Workload Workload is at the center of automation. Especially without an effective workload measurement tool, there does not exist at this time much insight into the fundamental question: Does automation affect total workload? Or more properly put, under what conditions does automation increase or decrease workload, or have little or no effect? What little evidence we have is based on attitude questionnaires and subject workload measures (e.g., National Aeronautics and Space Administration TLX). Wiener et al. (1991) compared subjective workload estimates of DC-9 and MD-88 pilots who had just flown the same line-oriented flight teams scenario. The MD-88 (glass cockpit version of a DC-9) pilots rated their workload higher than did the DC-9 pilots, by a slight but statistically significant amount. Wiener (1989) also expressed the belief that the effect of automation was to increase workload when it was already high, and decrease it when it was low. Most of the researchers in the area seem to agree (Rudisil, 1996), and research using simpler single-axis autopilots supports the assertion that automation increases cognitive workload while decreasing motor workload (Wickens and Kessel, 1980). Since it is motor workload that is observable, the designers may have gained a false impression that led to their claims of workload reduction. An observer can easily see manual activities in the cockpit but can view only by inference the cognitive processes and demands of a job. Billings (1996b:131) generalizes this result: "workload removed from one element of the system will often be reflected in additional workload elsewhere." Most people agree that a high degree of automation keeps the pilots' attention inside the cockpit (head-down), to the detriment of extra-cockpit scanning for traffic. It is not at all unusual to see both pilots "inside the cockpit" working on the control display unit. Check airmen, who observe and assess the activities of flight crews, are attuned to this, and make it part of their check ride. Langer (1990) put it most colorfully: "I have discovered that the flight management system control display units, in addition to being means of controlling the system, also act as cockpit vacuum cleaners … that is, they suck eyeballs and fingertips into them. I've given check rides on these airplanes and have seen four eyeballs and ten fingertips caught in two flight management system control display units at the same time. This is bad enough at cruise altitude, but it can be lethal in the terminal area."

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The Future of Air Traffic Control: Human Operators and Automation Crew Coordination and Resource Management Issues Relatively little has been written on the subject of crew coordination in aircraft in which electronic displays are used to present information—''the glass cockpit" (Wiener, 1993; Wiener et al., 1991). Helmreich and his colleagues have been studying attitudes about national culture and automation for several years (Sherman et al., 1997). Data have been collected on preferences for automation, and attitudes regarding automation use have been collected from pilots of glass cockpit aircraft in 11 nations on 5 continents. The degree of variability in attitudes and preferences was surprisingly large. Preference for automated over standard aircraft across nations ranged between 34 and 98 percent. More critical were attitudes in the area of skill degradation, head-down time, and perceived company policy regarding automation use. For example, agreement with the item, "I am concerned that the use of automation will cause me to lose flying skills" ranged from 19 to 73 percent across the 11 countries. The item "When workload increases, it is better to avoid reprogramming the FMC" elicited a range of agreement between 36 and 66 percent. Similarly, the item, "My company expects me to always use automation" showed a range between 49 and 100 percent. On most items, responses of pilots from the United States fell in the middle of the distribution. The data suggest that automation is viewed very differently by respondents from different cultures. McClumpha and James (1994) have noted considerable differences in response to automation of the same aircraft among pilots from different airlines. Similar variability may be found in reactions to flight in a more automated air traffic system. It seems clear that there are communication perils induced by the flight management computer aircraft, but it is equally clear that these can be overcome by crew resource management training and checking, as well as making effective communication part of the culture of the flight management system cockpit. Just how this should be done is not clear. Airbus Industrie has taken an aggressive approach by packaging crew resource management training, which they call AIM—airman integrated management—with the initial airplane training that they provide for customers of their new aircraft. This is a highly unusual step: customarily crew resource management training is provided by the end user airline, not the manufacturer. The communications problem has as its origin the fact that, due to the design of the automated cockpit, it is often difficult for one pilot to see what the other is doing. The cockpit may be described as two side-by-side workstations (Segal, 1995). The placement of the control display units creates a problem. Many airlines have a procedure that requires the pilot who did not enter the data (e.g., route changes) into the control display unit to review and approve what has been input before it can be executed.1 In practice this is seldom done, due to the 1   When new data are put into the control and display unit, the system is unaffected until the Execute button is pressed. Prior to execution, a new route, for example, is shown in white, making it easy to detect errors. This is one of the great safety features of the FMS—the ability to check out a plan before execution. When executed, the course line would change from white to magenta, the magenta line representing the course that the plane will fly.

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The Future of Air Traffic Control: Human Operators and Automation difficulty of leaning across the central pedestal to see the other pilot's display. The problem may be exacerbated if there are large disparities in knowledge of the many sophisticated and complex modes of the flight management system between the two crew members in the cockpit. Automation Issues Error Management and Control Error management is essential in flying FMS aircraft, as cockpit automation can be friend or foe. The previous issues are part of error control. Procedures are also an essential part: the FMS forces the issue of proper cockpit procedures to control error (Degani and Wiener, 1994). Assignment of duties ("who does what") is particularly critical in two-pilot FMS aircraft. Complacency and Boredom Most pilots agree that the modern FMS aircraft have very high reliability. They also frequently warn that this may lead to crews relaxing their vigilance and missing aberrations when they occur. The human factors issue is how to maintain vigilance in a somewhat boring, high-reliability environment. Evidence of the fallibility of the FMS (and its underlying database) was provided by the recent crash near Cali, Colombia (Strauch, 1997). Training and Proficiency Maintenance There is little written on the subject of training and proficiency maintenance for the modern cockpit. These are actually separate issues: how to conduct transition training to the glass cockpit, especially for the first-time glass pilot; the other issue is maintenance of skill through recurrent training, part-task simulator devices, and the role of line check airmen in maintaining cognitive proficiency In both instances, revealing studies by Sarter and Woods (1994, 1995a, 1995b) suggest the poor understanding that pilots have of the total mode structure of the FMS. Irving et al. (1994) and Casner (1995) have both suggested highly interactive training and simulation techniques whereby this training might be improved. A third, and somewhat obscure issue, is "reverse transition," training pilots who go from the flight management computer back to traditional cockpits as part of their career path (e.g., a high-seniority first officer on glass returns to the traditional cockpit of a less automated airplane in order to upgrade to captain).

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The Future of Air Traffic Control: Human Operators and Automation Job Satisfaction The question of job satisfaction in a highly automated environment was first raised by Wiener and Curry (1980). Since then, both authors have stated that in their field studies they found no trace of automation-induced apathy or job dissatisfaction (Curry, 1985; Wiener, 1985, 1989). If anything, pilots seem to be proud to be flying a modern aircraft and highly satisfied with the job. However, it should be noted that satisfaction with the automation provided by the FMS can vary greatly, depending on the attitude fostered by airline management (McClumpha and James, 1994). Danger of Catastrophic Failure Catastrophic failure is a threat to crew and passengers in any aircraft. There was some concern in the early days of FMS aircraft of total electrical failure, due to the fact that the aircraft is so electrically dependent. So far the only accident we are aware of that might be termed catastrophic failure was the Lauda Air B-767 that crashed in Thailand in 1991. The accident was due to an uncommanded deployment of a thrust reverser, not related to the flight management system or any other automatic feature. Incompatibility with Current Air Traffic Control Systems There is little argument that the current air traffic control systems are inadequate to control and optimize the flight paths of the modern aircraft. In short, the outdated air traffic control systems of today do not allow the crews of FMS aircraft to fully exploit its remarkable capabilities. This is one of the major complaints of the flight management system by aircraft pilots. The situation was explored in detail in a field study by Wiener (1989). Although the data collection of that study is now about 10 years old, the situation has changed little and will probably not change until the air traffic control systems are improved. When this occurs, and assuming that data link will enable direct digital communication between air traffic control and FMS, it will be important to ensure that there is harmony between the logic of the maneuvers in both ground and air-based systems. Conclusion The modern flight management system, beginning with the Boeing 767 in the early 1980s, brought a new era to flight guidance and control. It gave the pilot sophisticated, highly reliable tools to manage flight path control and power plant control with great precision. But with these ingenious tools came problems at the human-computer interface, resulting in some degree of distrust on the part of the

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The Future of Air Traffic Control: Human Operators and Automation pilots and, in the extreme, some spectacular incidents and accidents (Hughes and Dornheim, 1995). The great potential for precise, safe, and economical flight has been marred by these events. It is essential that the same mistakes not be made in the implementation of the next generation of air traffic management systems. One of the problems that must be confronted is the incompatibility between the new flight management system aircraft and the geographic and spatial constraints of the current air traffic control system, which is not compatible with the flight management system-equipped aircraft. The full potential of the flight management system cannot be exploited in today's air traffic control environment. Put simply, the planes are far more sophisticated than the ground-based systems, resulting in suboptimal use of the vehicle. This problem may be resolved when advanced air traffic management systems come online in the next decade. This may solve the problem of "impedance mismatch" between the vehicle and the ground-based systems, allowing more nearly optimal use of the flight management system and conservation not only of fuel, but also of that one, irreplaceable asset—airspace. FLIGHT INFORMATION PROCESSING AND PRESENTATION In this section we discuss key elements of the flight information processing system, as well as the human factors aspects of the presentation of flight information to controllers. Flight Information Processing Before complete flight information can be presented to controllers, flight plan and radar information must be acquired by the system, processed, and associated with each other. Figure 4.1 illustrates the key elements of the flight information processing and display system that supports the en route and terminal facilities. Primary elements of the system are the HOST computer, which provides processed flight plan information to terminal facilities and both radar and flight plan information to en route facilities, and the ARTS system, which processes radar data and associates them with HOST-provided flight plan information for terminal facilities. HOST Processing The HOST computer is divided into two systems, the flight data processor (FDP) and the radar data processor (RDP). The flight data processor provides flight planning analysis and automatically distributes flight progress strips to air route traffic control center (ARTCC) sectors and to towers and TRACONs through flight strip printers. The flight data processor takes flight plain input from the air traffic controllers and from aircraft users; determines the time it will take

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The Future of Air Traffic Control: Human Operators and Automation FIGURE 4.1 Key radar and flight information processing elements. to go from the departure point to the destination; identifies the fixes the flight plan will utilize; assigns a preferential route if necessary; and then posts flight progress strips to the appropriate tower/TRACON and the ARTCCs that will control the aircraft. The strips are printed on a flight data input/output (FDIO) device located at the various ARTCC sectors and at the towers and TRACONs. The time at which the strips are printed at the various sectors and facilities is a parameter that is set to ensure that they are printed in sufficient time for the controllers to plan for their traffic. The HOST radar data processor processes radar information from a variety of radars and supports presentation of a digital display of alphanumeric information, such as aircraft identity, altitude (mode C), climbing or descending information, ground speed, and assigned altitude. The flight plan information from the flight data processor is associated with the radar data so that the controller can project the aircraft's flight path on the radar display. The radar data processor allows the controller to make automated handoffs from one sector to another or to another ARTCC or TRACON. If the radar data processor fails, a backup system called the direct access radar channel provides the controller with alphanumeric information of aircraft on the radar display but is not associated with the flight data processor. When the flight data processor fails, there is no backup system. When this occurs, it usually has more impact on the air traffic control system than if radar fails. Prior to automation, flight progress and flight plan analysis were done by the controller. When a flight plan was filed, a controller would develop the route and

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The Future of Air Traffic Control: Human Operators and Automation determine the time to various fixes and to the destination based on the knowledge of the aircraft's performance and the upper winds. Estimates were passed from one facility to another indicating when the receiving facility or sector could expect to have control of the flight. The first air traffic function to see some automation was flight planning and progress strips. In the early 1960s, some of the large ARTCCs began to take advantage of rudimentary electronic computers to process flight plan information and print flight progress strips for manual distribution within the ARTCC sectors. These systems led to the development of the IBM 9020A mainframe computer. However, there was no standard computer program; each ARTCC with a 9020A developed "local programs." The first national program, developed to meet 80 to 85 percent of the requirements of each facility, became operational in 1972. Its extension to the remaining ARTCCs allowed flight progress information to be automatically passed to all air traffic control facilities throughout the United States. The radar data processor was added to the 9020s in the mid-1970s. The 9020s were replaced in the late 1980s with the HOST system, which handles more capacity with greater speed. Automated Radar Terminal System In the service of terminal (TRACON and tower) controllers, the automated radar terminal system (ARTS) performs radar data processing independent of the HOST computer, but relies on the HOST for flight data processing functions. ARTS performs additional processing involving a combination of radar data processor and flight data processor information. ARTS is a ground-based system that provides the air traffic controller with alphanumeric information superimposed on a raw radar target return. The information presented to the air traffic controller is aircraft identity (call sign), mode C altitude (if the aircraft is so equipped), ground speed of the aircraft, type of aircraft, whether or not the aircraft is considered a heavy jet (this is required for separation purposes), and miscellaneous information such as destination airport or first fix on the route of flight. The ARTS supports display of this information in the form of a data block that is constantly associated with the actual radar target through a software tracking program. The ARTS system was introduced to assist the controller with memory tasks. Providing information on the display rather than only on flight progress strips, the ARTS was intended to allow the controller more time to look directly at the display and to have real-time information available, such as aircraft identity, aircraft type, altitude, and ground speed. The first ARTS systems, called ARTS I and ARTS IA, were deployed in the New York and Atlanta facilities in the early and mid-1960s. They were essentially prototypes that led to the ARTS III, which was introduced to major TRACONs beginning in late 1969. ARTS II, which has less functionality (e.g.,

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The Future of Air Traffic Control: Human Operators and Automation no tracking capabilities), was introduced to lower-activity TRACONs in the 1970s. Presentation of Flight Information As noted above, one of the first air traffic control functions to see some level of automation was flight planning and flight progress strips. Over the years, flight progress strips have become what Hopkin (1991a) has called the "emblem of air traffic control," and it is not surprising that there has been a marked reluctance to replace them with an electronic version as part of the automation process. It is recognized that, in the current air traffic control systems, one of the major contributors to controller workload is the requirement for manual processing and distribution of flight data within and between units. Electronic "flight strips" of some description are necessary to support the automation of this activity. The concept of an electronic flight strip in automated systems, however, understates the objective of modernizing the processing and display of flight data. The issue that needs to be addressed in the research and development process is less one of perpetuating the current roles and functionality of paper strips than of how to achieve an effective electronic embodiment of flight data. Hopkin (1989, 1991b, 1995) has described many of the design issues that need to be addressed in a systematic integration of control information and has articulated the current challenge for interface design: A tabular information display of flight progress strips, whether electronic or manual, is difficult to integrate cognitively with a plan view of the air traffic. The consequent problem of cross-referral between radar and strip information is aggravated if traffic is heavy: there are more data to search through whenever there is less time to spare for searching. Windows of tabular information within the display do not wholly resolve this problem. A continuing challenge is the integration of these different kinds of information into a single practical format (1995:26). Integration of information from the radar, progress strips, and communications has enabled the controller to build up a picture or mental model of the traffic situation (Harper and Hughes, 1991; Whitfield and Jackson, 1983). The replacement of paper flight strips with a more automated electronic mode could, unless carefully designed, affect the construction of the mental model and its cognitive strength, variables that directly impact situation awareness (Endsley and Rodgers, 1994; Isaac, 1997; Harper and Hughes, 1991). Another concern in replacing paper strips with an electronic representation is that strips have provided a kind of "witnessability" that enabled another controller to determine what was being done and what needed to be done. Air traffic control can be viewed as a collaborative activity in which strips are an embodiment of the working division of labor. In their description of an ethnographic analysis of air traffic control, Hughes,

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The Future of Air Traffic Control: Human Operators and Automation Randall, and Shapiro (1993) refer to strips as work sites, publicly accessible to all members of the sector suite. Thus, the gradual modernization of air traffic control and the continuing concern for the reduction of operational errors have converged on the issues surrounding workstation and interface design, and particularly on the implications for controller performance of moving to a stripless environment. The following paragraphs provide an overview of research related to these questions that has been undertaken by the FAA Technical Center, the FAA Civil Aeromedical Institute (i.e., the Vortac studies), and other air traffic control organizations. Research Studies Issues in Transitioning to Electronic Displays An early evaluation by the FAA Technical Center of a touch-entry electronic tabular display for an en route environment (Rosenberg and Zurinskas, 1983) produced a favorable assessment of the concept by en route specialists. However, the results of the study showed that alternative data entry and update approaches should be developed to reduce errors, increase speed, and improve accuracy. Although empirical data to verify the purported role of flight strips are scarce, it can be reasoned that the process of physically manipulating the paper strips facilitates the controller's awareness of the physical relationships between aircraft (Hopkin, 1991a; Stein and Garland, 1993; Zingale et al., 1992; Vortac et al., 1993). Sorting the paper flight strips or cocking them on the strip board further facilitates the controller's understanding and memory for the flight data. Similarly, the automated presentation and updating of information could result in an emphasis on monitoring rather than on processing information in memory. This in turn could affect the creation and revision of the controller's mental picture and situation awareness. A set of four studies, conducted by the FAA Civil Aeromedical Institute and the University of Oklahoma to investigate these and other possible effects on the controllers' cognitive processing of converting from paper to electronic representations of flight progress data, have been summarized by Manning (1995). One of the research interests was to evaluate the hypothesis that utilizing an electronic flight strip display would improve controller performance and cognitive processing because the computer would reduce workload by assuming much of the associated manual activity of updating and maintaining flight progress information. The results of the studies generally supported the reduced-workload hypothesis. Their aggregate observations suggest that an interactive integrated display or interface that provides more direct access to both flight and radar data could enhance controllers' performance without a reduction in situation awareness. None of the studies, however, was intended to evaluate directly this automation option.

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The Future of Air Traffic Control: Human Operators and Automation Integrated Interfaces with Automation Operational evaluations of integrated displays have been undertaken to support the development of the Canadian Automated Air Traffic System (CAATS) (Stager, 1991, 1996). Experimentation on the design requirements for a stripless system was performed in France by the Eurocontrol Experimental Centre (EEC) (David, 1991) and the Centre D'études de la navigation aérienne (CENA) (Dujardin, 1990, 1993). In 1986, the EEC formed the Operational Display and Input Development (ODID) Group that subsequently performed a series of operational simulations. ODID is a subgroup of the Eurocontrol Member States' Expert Group for the Coordination of the Studies, Tests, and Applied Research (STAR) Programme on Color Displays and Stripless Systems. One of its responsibilities is to "design and establish an operationally acceptable and efficient control environment using electronic displays to replace strips" (Prosser et al., 1991:1). The first ODID simulation (Prosser and David, 1988) studied the use of colored electronic data displays as a means of replacing traditional flight progress strips. The second ODID simulation (Prosser and David, 1989) studied the use of the colored electronic displays and raster-scan colored situation displays. The results indicated a need for more closely integrated displays. In the third study, ODID III (Prosser et al., 1991), an electronic version of the then-current strip format was compared with a set of analog displays for the planning controller. In addition, the performance of two controllers working side-by-side was compared with their performance when separated and communicating only through their displays and communications link. Initially, the electronic strip display held too much permanently displayed data without a visible depiction of which tasks were outstanding; the planning controller, without a dynamic radar display, had to refer constantly to the display of the executive controller. In a second organizational format, a dynamic radar display was included for the planning controller, and there was a minimum display of tabular data. Speed of input is critical to the success of future automation in air traffic control. ODID IV (Day and Strut, 1993; Graham et al., 1994) used a graphical point-and-click interface. ODID IV was a stripless environment that took advantage of advanced planning aids used by the controller to assist the tactical radar (executive) controller in separating and optimizing air traffic flow. The ODID IV simulation is now a testbed for advanced air traffic control concepts and design principles, which are developed under the ODID program and then applied to other air traffic control systems. The PHIDIAS project (Dujardin, 1990, 1993) at CENA has worked in liaison with the ODID program to develop the controller interface, primarily for an en route sector, based on a stripless environment. The working positions are an integral component in the upgrading of the air traffic control system in France and will involve a phased introduction of a new radar system, an air-ground data link capability, and intelligent control aids. Research programs are currently in

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The Future of Air Traffic Control: Human Operators and Automation place to make comparative evaluations between ODID and the traditional PVD workstation. Such comparisons appear to offer promising benefits for ODID (Skiles et al., 1997). The Transition from Paper Strips The transition away from the use of conventional flight strips has provided particular challenges in design that have been largely common to all systems undergoing a modernization process. The design requirements that affect operational acceptability include the need to: Compensate for the redundancies provided by paper flight strips without being constrained by the direct replication of a paper-based model; Recognize how the characteristics of flight progress paper strips (and procedures associated with them) support the cognitive processes of the controller and are integral to task organization; Develop effective (i.e., rapid and simple) means of data entry; Fully integrate flight data within an electronic work environment; and Provide for a gradual operational transition period. Human Factors Issues in En Route and Terminal Flight Data Processing Workload When the HOST and ARTS flight information processing systems were first introduced, the keyboard entries were somewhat lengthy. Functions had to be identified by a keystroke followed by entering the appropriate data for that function (flight data, handoff information, etc.) Although the information was displayed on the radar display, the controller had to look away from the display to make the entries. The more keystrokes required, the longer his or her attention was diverted from the radar display. Data entry by point-and-click procedures were rare. With the introduction of programming enhancements called implied functions, the en route and terminal flight information processing systems were able to identify relevant functions on the basis of the context of displayed information. These implied functions eliminated the need to repetitively select function keys and then to enter data and command actions through the keyboard. They also provided for greater use of the point-and-click method for data entry. Training Training for the initial implementation of ARTS III was extremely efficient and effective. Teams of air traffic control specialists were trained on the system at either the developer's site or the Aeronautical Center in Oklahoma City. These specialists were then deployed to their home facilities prior to implementation, where they taught a cadre of on-site instructors how to use the system. This cadre of facility instructors then taught the remaining facility personnel.

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The Future of Air Traffic Control: Human Operators and Automation When the system was ready for operational use, it was introduced gradually to allow controllers to adjust to the system and gain trust. Small, quick-reference cards were available to the controllers as cues for keyboard entries. Communication and Coordination Pilot-controller communications were reduced by the introduction of the en route and terminal flight information processing systems. Constant updates on altitude and speed were no longer needed, since they were displayed on the radar screen. Automated acquisition of aircraft as they entered the radar range of the controller reduced the need for asking pilots to verify where they were in relation to a fix or geographic reference point. The human role in interfacility coordination was significantly reduced by the introduction of automated handoffs, a feature of the ARTS software and the ARTCC radar data processor. There was no longer a need for verbal coordination between air traffic control facilities when making or receiving handoffs. This was, however, evolutionary. In the early stages of the use of ARTS and the radar data processor, verbal coordination was required to verify the data that were transferred electronically. As the system became trusted, the requirement to verify data was eliminated. System Reliability Display errors with the initial en route and terminal flight information processing systems were very rare, and trust in the systems was quickly earned. Two major safety enhancements, the minimum safe altitude warning, the ground version of the airborne ground proximity warning system, and the conflict alert, were installed. Both enhancements generated a large number of false alerts in the ARTS system—a result of the programming. The algorithms used in the program are based on predictions of where the target will be in a given number of seconds and minutes rather than the actual proximity. In the case of the minimum safe altitude warning, aircraft that are in a planned steep rate of descent or are being vectored in an area of terrain will usually generate an alarm even though there is no danger. Aircraft that are operating under visual flight rules but are being tracked in the ARTS for traffic advisories and are flying below the minimal vectoring altitude will also generate an alarm. The conflict alert creates the same problem. Aircraft being tracked in the ARTS are usually within an airport area of minimum airspace, and as they are vectored to final approach courses, they are predicted to come within close proximity to other traffic. Although the separation is under control in this situation, the computer program does not know this and generates an alarm. Although both of these enhancements can be selectively inhibited, they usually are not (minimum safe altitude warning is inhibited for aircraft that are on visual flight rules transponder codes), because controllers value the correct alarms. More sophisticated versions of the same predictive function, the conflict probe tool, are discussed in Chapter 6.

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The Future of Air Traffic Control: Human Operators and Automation Team Environment Although controllers still work in teams, and their supervisors are called team supervisors, the en route and terminal flight information processing systems permit controllers to work more independently than they did before the introduction of these systems. With automatic handoffs and radar target acquisition and data being presented on the radar display, there is less need for controllers to seek help from a coordinator or handoff person, and, since requests for assistance have been reduced, there is an associated tendency on the part of coordinators and handoff persons to pay less attention to what the radar controller is doing.