The Effects of Degraded Visual Cueing and Divided Attention on Obstruction Avoidance in Rotorcraft

Abstract : The FAA is investigating rotorcraft obstruction related accidents. This report is a small part of that effort. It is based on analysis, ground-based simulation, and flight testing conducted in support of the U.S. Army rotorcraft flying qualities specification. Portions of that work involved the evaluation of rotorcraft flying qualities in degraded visual environments. These tests showed that a deterioration in the effective rotorcraft flying qualities occurred in conditions of degraded (but not zero) visual cueing. in such flight conditions, the pilot workload was very high, just for aircraft control. This left the pilot very little excess workload capacity to maintain awareness of the rotorcraft position and rates with respect to obstructions or the ground. This indicates that the combined effects of a degraded visual environment, turbulence, and only fair basic rotorcraft handling can lead to a workload that exceeds the pilot's capability. This leads to a loss of situational awareness and it explains many accidents where experienced pilots have committed seemingly absurd errors. For example, pilots drifted into objects in their field-of-view, inadvertently transitioned into rearward or sideward flight, and flew into the ground. Army experiments indicate that the addition of artificial stabilization can substantially improve flying qualities in degraded visual environments. This results in a dramatic decrease in the aftentional demand required for rotorcraft control and more capacity to maintain situational awareness. Thus increased stabilization may have a more positive impact on decreasing collision avoidance accidents in degraded visual environments than many more intuitively obvious solutions (e.g., cockpit warning lights, horns, etc.)