QuanUfic4tion of Pilot Workload via Instrument Scan tMtS ToUO.Z). AT Staph«n«(1.3). R.L Harris.Sr.(4). and A. Ephrath(S) 1.Harvard/MIT Division of Haalth Soianoss and Tochnology 2.Currant Addrass: Biomsdical Enginatring. Vorcastar Polytachnic Inatituta

■ ■ \ This papar dascrlbss work in prograss on tha usa of visual scanning bahavior as an indicator of pilot workload. Tha study is investigating tha relationship bstwaan laval of porfornanca on a constant piloting task under siaulated IFR conditions, the skill of the pilot, th* level of mental workload induced by an additional verbal task imposed on the basic control task, and visual scanning behavior. _J HThe results indicate an increase in fixation dwell times, especially on the primary instrument with increased mental loading. Skilled subiects ''stared" less under increased loading than did novice pilots. Sequences of instrument fisations were also esamined. The percentage occurrence of the subiect's most used sequences decreased with increased task difficulty for novice subiects but not for highly skilled subiects. \ Entropy rate (bits/sec) of the sequence of fixations was also used to quantify the scan pattern. It consistently decreased for most subiects as the four loading levels used increased An exponential equation in task difficulty was found to be agood predictor of entropy rate. When solved for task difficulty, the equation provided an estimate of the level of task difficulty perceived by 4 subiect. J Piloting and numbet task performance measures were recorded and a combined performance measure was computed. Skill was estimated independently via a method based on pilot experience. These measures were combined with entropy rate to develop a model relating performance, skill. and mental workload. The exponential model fit the data well enough to suggest that this approach has promise in the evaluation of interactions among these variables.