Effect of Control System Augmentation on Handling Qualities and Task Performance in Good and Degraded Visual Environments

Abstract

An experiment in the NASA-Ames Vertical Motion Simulator examined and quantified the effects of limited-authority control system augmentation on handling qualities and task performance in varying visual environments. The simulated vehicle was the OH-58D with similar characteristics to the Bell 407 civilian helicopter often used for emergency medical services. The control systems investigated were a baseline rate command system, a short-term attitude command/attitude hold system, a "modernized control laws" system that provides an attitude command/attitude hold control response type, and modernized control laws with a position hold function. Evaluation tasks included a number of ADS-33 mission task elements, as well as a proposed emergency medical services task consisting of an approach and landing at a minimally prepared landing site. Degraded visual environments were simulated with an unaided night scene and using night vision goggles. Results showed that handling qualities ratings were improved with a control system providing short-term attitude response over a rate command system, although the improvements were not sufficient to produce Level 1 handling qualities in degraded visual environments. Using modernized control laws showed that borderline Level 1 handling qualities could be achieved in degraded visual environments using a 10% authority stability augmentation system.