An experiment was conducted to investigate the impact of various flight-related tasks on the workload imposed by the requirement to compute new headings, course changes and reciprocal headings. Nine instrument-rated pilots were presented with a series of heading-change tasks in a laboratory setting and in a single-place instrument trainer. Two levels of difficulty of each of three tasks were presented verbally (numeric values embedded in simple commands), spatially (headings were depicted on a graphically drawn compass) and combined (each of the previous displays were given simultaneously). In the instrument- trainer setting problems were presented orally by one of the experimenters and no effort was made to manipulate display types. Performance was measured by evaluating the speed (response times) and accuracy (percent correct and time outs) of the responses. The workload experienced by the pilots under each experimental condition was determined by responses to a standard set of bipolar rating scales. These subjective measures reflected the differences between levels of difficulty and types of tasks, but were generally insensitive to the manipulation of display type. The performance measures, however, displayed significant differences for all manipulations. Problems presented in the combined and alpha display formats, were done significantly faster and with significantly greater accuracy than problems in the compass format alone suggesting that the pilots were primarily using the alpha information contained in the combined display to perform the calculations. Workload ratings for the compass-only laboratory condition and the instrument trainer portion of the study were virtually identical across all conditions.