Uncertainty management in enroute air traffic control: a field study exploring controller strategies and requirements for automation

Abstract

The management of uncertainty is a critical aspect of current as well as future air traffic control operations. This study investigated: (1) sources of uncertainty in enroute air traffic control, (2) strategies that air traffic controllers adopt to cope with uncertainty, (3) the trade-offs and contingencies that influences the adoption of these uncertainties, and (4) the requirements for system design that support controllers in following these strategies. The data were collected using a field study in two enroute air traffic control centres, involving “over the shoulder” observation sessions, discussions with air traffic controllers, and document analysis. Three types of uncertainty coping strategies were identified: reducing uncertainty, acknowledging uncertainty, and increasing uncertainty. The RAWFS heuristic (Lipshitz and Strauss in Organ Behav Hum Decis Process 69:149–163, 1997) and anticipatory thinking (Klein et al. in Anticipatory thinking, Proceedings of the eighth international NDM conference, Pacific Grove, CA, 2007) were used to identify reduction and acknowledgement strategies. Recent suggestions by Grote (Saf Sci 71:71–79, 2015) were used to further explore strategies that increase uncertainty. The study presents a new framework for the classification of uncertainties in enroute air traffic control and identified the uncertainty management strategies and underlying tactics, in context of contingencies and trade-offs between operational goals. The results showed that controllers, in addition to reducing and acknowledging uncertainty, may deliberately increase uncertainty in order to increase flexibility for other actors in the system to meet their operational goals. The study describes new tactics for acknowledging and increasing uncertainty. The findings were summarized in the air traffic controller complexity and uncertainty management model. Additionally, the results bring to light system design recommendations that allow controllers to follow these different coping strategies, including (1) the design of alerts, (2) the transparency of prediction tools, and (3) system flexibility as a requirement for acknowledging and increasing uncertainty. The results are particularly important as uncertainty is likely to increase in future operations of enroute air traffic control, requiring automation support for controllers. Implications for future air traffic management scenarios as envisioned within the SESAR Joint Undertaking (SESAR JU in European ATM Master Plan, 2 eds, 2012) and NextGen (FAA in FAA’s NextGen implementation plan, 2014) operational concepts are discussed.

Appendix: Overview of controller support tools (adapted from Corver and Aneziris 2014)

Stripless tools	Description of the tool
Electronic coordination
E-coordination tool	The E-coordination tool (Fig. 2) allows controllers of different sectors to electronically coordinate changes to the trajectory of a flight, e.g. by proposing a rate of descent/ascent, a flight level, or a direct route
Medium-term conflict detection tools
Horizontal scanning tool (HST)	The horizontal scanning tool (HST, Fig. 3) is a conflict detection function whose outcome is displayed on the radar display, in the aircraft label and in a separate window which lists potential conflicts (encounters) having a horizontal separation of 10 nautical mile or 15 nautical mile or less (encounter threshold)
Exit conditions assistance tool (ECAT)	The exit conditions assistance tool (ECAT, Fig. 4) supports controllers in planning aircraft through the sector in a timely manner by listing all aircraft planned to exit at an exit point, sorted according to their predicted exit times. Potential exit conflicts are identified by highlighting the exit flight levels of these flights. In addition, controllers are presented with a suggested solution. Exit conflicts arise if exit conditions (typically three or more minutes of separation between aircraft, or as specified in letters of agreement between centres) cannot be complied with
Dynamic scanning tool (DST)	The dynamic scanning tool (DST, Fig. 5) displays a prompt window when a controller enters a solution which, according to the system, is unsafe. This prompt window displays information about the potential crossings, including minimum distance and time until minimum distance is expected. The trajectories are marked in red where loss of separation is predicted
Analysis support tool
Crossing tool	The crossing tool (Fig. 6) helps controllers in the analysis of a potential conflict situation and with the monitoring of a crossing situation. When using the crossing tool, the controller selects the two aircraft to be monitored against each other and the system extrapolates their positions to calculate the minimum separation between them
Click and hold	The click and hold tool (Fig. 7) allows controllers to analyse the traffic situation by selecting a flight level in a dropdown menu. Only traffic which is cleared to this flight level and/or descends/climbs trough this level is highlighted
Planning and measuring tools
Planning tools	Planning tools include speed vectors for each aircraft, which can be extrapolated based on the present heading and speed, as a result of the interaction with the mouse wheel (extrapolation of the future position in increments of minutes), thus giving visual information about the future position of the aircraft
Measuring tool	The measuring tool supports controllers in measuring distances between aircraft, between trajectories, or critical points)
Monitoring aids
Cleared level adherence monitoring function (CLAM)	The cleared level adherence monitoring function (CLAM, Fig. 8) is a monitoring aid that monitors actual flight level of the aircraft against the cleared flight level (CFL) given to the pilot and entered by the controller in the system. It provides a warning in case of a deviation
Route adherence monitoring (RAM) function	The route adherence monitoring (RAM) function is a monitoring aid to support controllers in detecting that an aircraft has deviated from the trajectory as known to the system. An alert warns the controller if the current aircraft flight path deviates from the trajectory as expected by the system