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The Effects of Tool Type and Barrier on Time Required for a Remove and Replace Task

The Air Force's CREW CHIEF is a computer-graphics model of the physical characteristics of a maintenance technician. It is used to evaluate the ability of maintenance personnel to work in areas with respect to arm reach, operation of hand tools, strength available for torquing with wrenches, strength for manual materials handling, vision analysis, and accessibility analysis. A new CREW CHIEF feature under development is the Task Time Estimator, which will predict the time required to perform a remove/replace task in an obstructed environment. The goal of this experiment was to gather time to completion data and determine the effect of different tool type combinations. The task, performed while standing erect in a simulated work area, was to remove and replace a flange coupling while reaching through a six by eight inch opening. On half of the trials a barrier was positioned so as to restrict hand and tool movement. On the other half of the trials, no barrier was used. Thirty subjects, representative of USAF personnel, were divided into five groups, each of which utilized a different combination of wrenches (ratchet/box, box/box, box/open, open/box, and open/open). The ratchet/box and box/box tool combination resulted in the fastest completion times. The open/box combination resulted in intermediate completion times, while the box/open and open/open conditions produced the slowest completion times. Barrier presence increased the time required to complete both tasks and removal took less time than installation. Several noteworthy interactions and implications regarding tool selection are discussed.