Clothoid-Augmented Trajectories for Perspective Flight-Path Displays

Abstract

Perspective flight-path displays allow pilots to accurately follow complex curved approach trajectories. The current practice to define the tunnel reference trajectory as a concatenation of straight and circular segments, however, leads to difficult transition maneuvers between these segments, strongly contributing to pilot workload. To achieve a smooth interception, clothoid transition paths can be inserted between the straight and circular sections. A clothoid function defines a trajectory curvature that changes from 0 (a straight trajectory) to the desired curvature (the circular trajectory) in a certain amount of space traveled. Because the reference path better matches the natural aircraft response, the clothoid transients are hypothesized to make the task of flying complex curved approaches easier. A pilot-in-the-loop experiment, conducted in a fixed-base flight simulator, confirms this hypothesis and shows that clothoid-augmented trajectories yield improved path-following performance, require fewer pilot control actions, and result in higher comfort levels.Curved approach profiles are expected to increase the flexibility of air traffic management near large airports. Flying these inevitably more complex approaches results in a higher task demand load and requires a high level of pilot situation awareness. Improving the transfer of information to the pilot through intuitive, pictorial displays can mitigate these problems considerably. Research indicates that perspective flight-path displays, such as the tunnel-in-the-sky dis-