Using asymmetric vibrations for feedback on flight envelope protection

Abstract

Modern aircraft use a variety of fly-by-wire control devices and combine these with a flight envelope protection system to limit pilot control inputs when approaching the aircraft limits. The current research project aims to increase pilot awareness of such a protection system through the use of force feedback on the control device, i.e., haptics. This paper describes a new iteration of a design with the specific aim to warn the pilot when approaching a limit and provide a clear direction of suggested control input. This is achieved by using vibrations asymmetric in both amplitude, i.e. the mean of the signal is non-zero, and time, i.e. a cue which has a rise time different from the fall time. An evaluation is performed where 24 active PPL/LAPL pilots flew a challenging vertical profile and encountered a windshear. The pilots are divided in two groups: one group performing four flights with haptic feedback, followed by four without, the other groups has a reversed order. Although acceptance ratings slightly improved when providing haptic feedback, the other metrics are unchanged when switching between haptic feedback conditions, due to a large training effect during the first four runs. The results do show that enabling the haptic feedback does seem to improve the learning rate over the first runs, and no after effects are present when feedback is removed. As such, next to the fact that most pilots indicated that they expect an improved safety, this experiment shows a potential training benefit of haptic feedback.