Thesis

The effect of feedback delays on the next generation route assessment tool

Predicted increases in air traffic are driving a paradigm shift in the Air Traffic Management system. The ATM research community has identified the adoption of Trajectory-Based Operations a viable concept of operation to accommodate the traffic growth while maintaining system safety and efficiency. This transition would require pilots and controllers to use trial planner tools to create, evaluate, modify trajectories that are exchanged between the ground and airborne systems. However, various lags (e.g., in communications or computation of trajectories) can induce delays in providing the feedback to the user during conflict search and trial planning processes. This research addresses this issue by conducting an experiment to study the effects of feedback delays on pilots during conflict detection and avoidance tasks. Twelve pilots participated in 40 en-route flight part-task simulations that required them to avoid separation violations with surrounding aircraft while maintaining flight safety and fuel efficiency. Actual air traffic over Kansas City airspace was simulated in the experiment and scaled to have moderate and higher density than current day level. The traffic was displayed on the NASA Ames Cockpit Situation Display, which featured a trial planner tool equipped with conflict alerting functionality. Feedback delays of 0, 2, 4 and 8 seconds were added to the conflict alerting functionality to observe any significant changes in pilot comfort as well as route efficiency and safety. Irrespective of the levels of feedback delays, pilots showed no significant decrease in performance in moderate traffic density simulations. However, the results were considerably different in the high traffic density condition, where the efficiency decreased significantly at levels of delay greater than 0 seconds and the pilot decision time increased significantly. In addition, pilots were more likely to commit to unsafe routes in high-density conditions with feedback delays greater than 0 seconds. It is reasonable to assume that delays are impossible to completely eradicate, but perhaps they need not be completely removed from these systems to successfully meet flight and business objectives. With thorough calculations stakeholders may be able to extrapolate the amount of feedback delay that can be deemed as acceptable in order to meet safety as well as business requirements.

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