Time Delays In Visually Coupled Systems During Flight Test and Simulation

Abstract

Increasing control system time delays have well-documented detrimental effects on pilot-in-the-loop performance. With increased use of helmet-mounted displays in aircraft, pilots may soon be exposed to both control system and visual display system time delays. They may be sensitive to both the magnitude and source of the time delay, that is, some pilots may be more sensitive to visual delays than to control delays, or vice versa. In the current study, control and visual delays were examined in two experiments, the first conducted in a helicopter and the second conducted in a flight simulator. A helmet-mounted display was used to present external imagery and symbology in both experiments. Standardized low-level maneuvering tasks were used to examine changes in system handling qualities ratings as a function of time delays in the control and visual display processing loops. The addition of delays in both the control and the visual loops impaired the system handling qualities and increased the magnitude of position maintenance error. Differences between control and visual delays were evident in reports of motion sickness symptoms, which were more frequent for visual delay conditions. Motion sickness symptoms and related physiological effects induced by delays may increase pilot fatigue. Therefore, determination of acceptable latency criteria for design and implementation in systems with visually coupled components is critical.