required procedures, the negative impact on organizational functioning should be minimized. However, it is possible that subtle shifts in authority from the R-side controller to the D-side (who is more likely to have direct access to CTAS advisories) could have unpredictable consequences. We explore these consequences further in the discussion of conflict probes in the following section.

Conclusion

CTAS appears to be a well-conceived automation concept, addressing a valid concern of the less automated system and designed with an appropriate philosophy that is based on automated advice-giving, rather than automation-based control. As such it is characterized by a relatively low point on the level of automation action scale, discussed in Chapter 1, which accordingly diminishes (but does not eliminate) the extent of concern for complacency. Finally, CTAS has been developed and introduced gradually, in a manner sensitive to human factors issues, and to the importance of filtered controller input into the functioning of the system. Careful human factors monitoring of the system's field use should be continued.

CONFLICT PROBE AND INTERACTIVE PLANNING

The core of the controller's job is to maintain a continuous flow of air traffic while also preserving adequate separation. There are three interrelated automation functionalities that can potentially assist in these goals: conflict probes, interactive planning tools, and conflict resolution advisors. The conflict probe is essentially a preview of the current flight trajectory of a given aircraft, to assess whether it will create a loss of separation with another aircraft at some time in the future. Current probes exist in the ARTS and HOST computer systems, yielding alerts if conflicts are predicted (discussed in Chapter 4). Similar conflict probe logic also characterizes the TCAS system (discussed in Chapter 5). These current air traffic control probes are not sophisticated, in the sense that their predictive logic is based on an extrapolation of the current ground velocity (or, in the case of TCAS, the rate of closure). They may also be described as tactical, in that they forecast only a short duration (i.e., a few minutes or less) into the future.

In contrast, however, far more intelligent probes, such as those embedded in CTAS, can include models of different aircraft capabilities, head winds, and even flight plans, to more accurately estimate the future four-dimensional trajectory of the aircraft. Smart probes, such as those incorporated into CTAS and COMPAS are far more strategic in nature, allowing much longer look-ahead. Figure 6.6 illustrates a CTAS conflict probe display (see color plate). It should be noted, however, that, although systems such as COMPAS and CTAS are highly sophisticated conflict resolution systems, they leave the final authority for implementing that resolution squarely with the human. Some other development efforts



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