Terence S. Abbott

Comparison of workload measures on computer-generated primary flight displays

Four Air Force pilots were used as subjects to assess a battery of subjective and physiological workload measures in a flight simulation environment in which two computer-generated primary flight display configurations were evaluated. A high- and low-workload task was created by manipulating flight path complexity. Both SWAT and the NASA-TLX were shown to be effective in differentiating the high and low workload path conditions. Physiological measures were inconclusive. A battery of workload measures continues to be necessary for an understanding of the data. Based on workload, opinion, and performance data, it is fruitful to pursue research with a primary flight display and a horizontal situation display integrated into a single display.

Integration of Altitude and Airspeed on a Primary Flight Display

Electronically generated primary flight displays were evaluated in a fixed-base simulator configured as the Research Flight Deck of the NASA Transport Systems Research Vehicle (TSRV). The primary flight display included vertical tapes for altitude and airspeed. Several key questions relating to the representation of information on moving-tape formats were examined during this study and are: (1) if airspeed/altitude trend vectors should be included, (2) if the actual or desired airspeed/altitude values should be centered on the tapes, and (3) if high or low numbers should be at the top of the airspeed scale. These combinations resulted in eight display configurations. Two pilots were used as subjects. They were required to fly eight unique paths which changed in altitude or airspeed every 15 seconds. Each path took approximately 3 minutes to fly. Both pilots flew all eight paths with each of the eight display configurations. They were also required to listen to high-pitched and low-pitched tones presented via a headset and count the number of low-pitched tones both as a secondary task and in order to obtain Auditory Evoked Potential (AEP) data. In addition to objective performance measures, workload was assessed with both the Subjective Workload Assessment Technique (SWAT) and the (AEP) data. An opinion questionnaire was also used. Each question was scored from 1 to 5 with higher scores representing a higher positive opinion. Preliminary data analysis was performed on the two display configurations which, prior to data collection, were anticipated to produce the greatest differences in performance and workload. Highest performance and lowest workload was expected of display configuration 1, which included airspeed/altitude trend vectors, had actual airspeed/altitude values centered on the tapes, and had the larger numbers at the top of the airspeed scale. Poorest performance and highest workload was expected from display configuration 8, which excluded all trend vectors, had desired airspeed/altitude centered on the tapes, and had the smaller numbers at the top of the airspeed scale. For this analysis, the quantitative data showed that configuration 1 had a mean altitude RMS error of 16.47 ft in contrast with an altitude RMS error of 30.29 ft with configuration 8 (p = .0005). There was also a significant difference in the means on the opinion questionnaire with configuration 1 yielding an opinion rating of 3.81 and configuration 8 a rating of 2.63 (p = .0008), indicating a preference for configuration 1. As a secondary portion of this study, the relationship between the AEP data and other workload data will be determined. Initial analysis was again performed on the two display configurations. This analysis showed that although the mean SWAT scores and the AEP P300 amplitudes for configuration 1 and configuration 8 indicated the same general trends, the differences were not statistically significant. However, it is noteworthy that a separate analysis, which included all of the display configurations, has shown a statistically significant correlation to exist between the P300 amplitude data and SWAT.