J. W. Frazier

A task difficulty—G stress experiment

This paper describes a study of methods to design manual tracking tasks. These tasks are to be used to help investigate performance changes as humans are subjected to G acceleration stress. The design of the tasks had to meet two criteria. First, the tasks were required to differ from one another in terms of subjective difficulty (as well as showing a performance change empirically). Secondly, each task had to be sensitive enough to show performance changes in a stress/non-stress environment. The tasks used were of a sum of sines design approach which occurs commonly in manual control theory. The type of environmental stress considered in this study was a + Gz acceleration to which aircraft pilots are exposed during flight manoeuvres. The experiment was conducted on the Dynamic Environmental Simulator (D.E.S.), a three degree of freedom human centrifuge located at the Air Force Aerospace Medical Research Laboratory at Wright Patterson Air Force Base, Ohio.

Changes in time estimating abilities through workload analysis as measured by +Gz acceleration

The time estimation of pilots under various workloads was investigated. Eight subjects completed four days of randomized testing and were exposed each day to two simulated aerial combat maneuvering (SACM) profiles of 180-s duration and with a maximum level of +8 Gz. Counting and noncounting (rate projection) tasks were used as time estimation techniques. The time intervals measured were 2, 8, and 16 s. The duration of the noncounting task (the most accurate task to estimate) was found to be greater than 8 s. The production task was much more accurate to estimate than the reproduction task, and long-duration tasks were found to be most influenced by the intensity of the G stress, as well as if the G stress was decreasing.<<ETX>>