Flight to the Future Human Factors in Air Traffic Control (1997) / Chapter Skim
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5 COGNITIVE TASK ANALYSIS OF AIR TRAFFIC CONTROL
5 COGNITIVE TASK ANALYSIS OF AIR TRAFFIC CONTROL
Pages 89-111
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From page 89... ...
Part II HUMAN FACTORS AND AUTOMATION ISSUES
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From page 91... ...
We then describe the ways in which human cognitive processes both are an asset in air traffic control and are vulnerable to environmental and system variables, discussing factors that moderate these vulnerabilities. Such an analysis has equal relevance for training as it does for design.
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From page 92... ...
These include the filing of flight plans, pilot requests for clearance, changes in aircraft trajectories, handoffs from other controllers, and changes in weather. Other important events, however, may occasionally occur at an airport or in an air traffic control facility itself, such as blocked runways and instrument or power failures.
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From page 94... ...
Expectations may be based on specific past events (a plane is expected to continue on a given heading, a pilot is expected to read back the clearance provided and to change the aircraft's speed, altitude, or heading accordingly; Monan, 1986) , or they can be based on general scripts of how the air traffic control process operates (Schank and Abelson, 1977)
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From page 95... ...
Experience in a domain often leads to long-term memory structures that permit more efficient and/or insightful encodings or "chunking" of multiple events (Chi et al.,1981~. In the air traffic control domain, for example, experienced controllers may directly identify important types of events involving multiple aircraft (such as conflict)
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From page 96... ...
For example, strategies for allocating perceptual attention among external events may help controllers handle situations with a high event rate (Stein, 1993; Gopher, 1993~. Strategies for prioritizing tasks may also help when workload is high (Gopher et al., 1994~.
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From page 97... ...
However, once the problem is noticed, it can be handled with little or no cognitive effort, as long as the controller is reasonably experienced and the event rate is reasonably low; the formulation of intentions and actions remains fairly routine. Unexpected events that are somewhat more complex (e.g., the announcement of an unanticipated newly arriving aircraft, a request for diversion)
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From page 98... ...
at which a controller has worked for years may trigger knowledge-based behavior in a facility or sector new to that controller, where local procedures may differ as well as the nature of equipment, the sector structure, the terrain, the traffic mix, and the air routes. The heavy impact of facility-specific learning in air traffic control has important implications for the difficulty of generic training (see Chapter 3~.
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From page 99... ...
Visual Sampling and Selective Attention Because much of human visual search and pattern recognition is serial, with event-filled displays the controller is vulnerable to missing critical events through breakdowns in the serial visual scanning process (Stein, 1993~. This is particularly true to the extent that many of these events must be inferred from signals that are not particularly salient to the untrained eye (e.g., a future conflict, a change in the altitude field in the data, a pilot's failure to implement a requested course alteration)
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From page 100... ...
Such errors can also be expected to form a major source of breakdown in communications within the air traffic control facility (see Chapter 7~. Working Memory Working memory is very susceptible to interference, both from other items competing for the same processes and from other information-processing activities.
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From page 101... ...
, and its vulnerabilities in the national airspace system have been well documented by Nagel (1988) , who notes that the largest single cause of air traffic control incidents relates to breakdowns in information transfer (see also Kanki and Prinzo,1995~.
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From page 102... ...
. Still, the nature of most air traffic control decision making is relatively routine and enables controllers to select appropriate procedures to apply once they correctly identify and classify the existing situation.
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From page 103... ...
This fact is the inevitable down side of the highly advantageous quality of human flexibility and adaptability, which we discussed as a great cognitive strength for air traffic control. Indeed, it is a strength that the human operator brings to any complex system (Rasmussen et al., 1995~.
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From page 104... ...
The crash of Airbus A320 near Strasbourg, France, was apparently the partial result of a mode error, when the pilot apparently believed that the autopilot was in a 3.3degree flight path angle descent mode, when in fact the same "3" setting triggered a 3,300 ft/minute descent mode. Slips of action occur when the correct intention is formulated, but the incorrect action slips out of the controller's fingers (in the case of keyboard entry)
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From page 105... ...
Visual Sampling Difficulties with visual sampling can be exacerbated by the low arousal resulting from sleep loss, fatigue, and circadian rhythms, by cluttered displays or a cluttered visual environment, by display environments that have many similar appearing elements; and by the distraction of high workload. Many of these problems can be attenuated by automated assists that recognize critical events and translate them into salient abrupt onset signals (e.g., conflict alerts, minimum safe altitude warnings)
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From page 106... ...
discussed in Chapters 7 and 12 can accomplish this function, although elimination of auditory channels via datalink would destroy redundancy. Attention to task analysis, minimizing unnecessary auditory stimulation, and minimizing the existence of potentially confusing (similar)
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From page 107... ...
Furthermore, replacement of voice communications received by the pilot from air traffic control by datalink may eliminate many important nonlinguistic cues available to the pilot, such as the degree of urgency of an instruction. In contrast, efforts to support shared situation awareness, perhaps through common displays or common training, can facilitate communications.
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From page 108... ...
is unlikely to result in improved performance by air traffic controllers (Means et al., 1993~. However, decision making may be improved by training and displays that are sensitive to strategies that do work well in real-world environments.
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From page 109... ...
Decluttering of a display to facilitate visual selective attention may hide information necessary to sustain situation awareness. Silencing auditory chatter to avoid interference with working memory may also have a corresponding negative effect on situation awareness, by removing useful communications channels (Pritchett and Hansman, 1993~.
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From page 110... ...
Research should address the efficacy of analog predictors of aircraft altitude. The panel identified a number of opportunities for improvements in the air traffic control environment: · Communication is facilitated by shared knowledge or situation awareness between speaker and listener, and it is important to preserve this wherever possible, perhaps enhancing it through display technology or training.
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From page 111... ...
Although air traffic control errors are inevitable to some extent, they can be minimized by providing attention to good human factors design. Their impact on system performance can be minimized by adopting a design philosophy that preserves some redundancy of human information transmission (redundant displays, multiple operators)
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