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.