Four empirical operator workload (OWL) scales were applied to ground control operations of the Aquila RPV during a recent field test: NASA TLX, SWAT, Overall Workload (OW), and the Modified Cooper-Harper (MCH). Seventeen sets of individual assessments of mission segments were made by the four members of each of four crews and one replacement crewman. Jackknife factor analysis revealed the presence of only a single factor and indicated that the mean factor loadings formed a consistent ordering (F(3,48) = 503.5, p < .00005): TLX (.910) > SWAT (.893) > OW (.869) > MCH (.833). ANOVAs also examined the effects of various variables on the composite workload factor scores; significant findings were found which reflected both upon the system and its test. These findings as well as informal lessons learned are discussed in the context of the development and validation of a methodology for assessing OWL.
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