Effects of Hover Symbology Display Scaling on Performance and Workload

Rotorcraft symbology can provide pilots with the flight information necessary to replace the visual cues lost when operating in degraded visual environments. However, tuning symbology for effective use is a time-consuming process as it generally requires considerable in-flight testing and extensive trial and error. In this work, two experiments are conducted to assess how changes in the display scaling of a position-velocity-acceleration architectured symbology set affects pilot performance and workload. In the first experiment, participants attempt a modified single-axis precision hover using a simulated helicopter and nonconformal symbology set while display parameters relating to acceleration, velocity, and position cue scaling are varied. Performance is measured using the root mean square of the position error relative to a target location, and participant workload is assessed using their cyclic control activity and Bedford ratings. In the second experiment, an analytical pilot-in-the-loop simulation is conducted to validate the performance results obtained in the first experiment and to investigate the underlying system characteristics that contribute the observed trends. For the implemented symbology and Bell UH-1H model, the results from both experiments concur that a combination of low-to-mid range acceleration cue scaling and mid-to-high range position cue scaling enable strong performance without inflating workload. Results indicate an insensitivity to velocity vector scaling, likely due to the symbology architecture and nature of the control task. The results of these experiments establish a predictable relationship between display scaling and pilot response, which can aid in streamlining the tuning process for similarly-styled symbology, helicopter and task envelope combinations.