The Effect of Visual System Time Delay on Helicopter Control

Abstract

There is interest in the development of synthetic visual systems to improve the capability of aircraft to takeoff and land in poor visibility. These systems often have inherent processing delays that can affect a pilot's ability to control an aircraft and a pilot's sense of orientation. The goal of the current study was to determine how much time delay a pilot could tolerate before control was affected, and whether physiological effects would be apparent at the same point. Pilots hovered at a predetermined position in a full flight simulator equipped with a Computer Image Generation (CIG) system and a helmet mounted display. The pilot's visual image was delayed by 67 to 334 milliseconds and varying levels of turbulence were applied to increase the task difficulty. Pilot performance was assessed by collecting objective data on aircraft position error. Handling qualities ratings and reports of physiological symptoms were collected by questionnaire. The results showed that visual time delay increased the variability of position error when as little as 134 ms of delay was encountered. At long delays, sickness symptoms were reported in addition to handing qualities decrements. Turbulence had a minimal effect on performance with long time delays, however it resulted in increased station keeping errors and degraded handling qualities at low delays.