Analysis Techniques For Man-Machine Systems Design

NATO UNCLASSIFIED49 - AC/243(Panel-8)TR/7Volume 2ICAdvantagesThe approach is simple, and involves minimum effort.Users report it to be low COSL It is well suited to thedevelopment of equipment or simple systems whichevolve comparatively slowly through severalgenerations such as guns and land transport vehicles,and some armoured fighting vehicles.DisadvantagesThe approach lacks standardization and traceability. Theonly evidence that the new system will perform well isthat available from the previous system.The assumption that functions should be allocated on thebasis of whatever can be done by machine means thatoperators perform whatever functions are lett, that cannotbe done by machine. Generally this results in a reductionin the complexity and interest of the humanresponsibilities, to the point where the operator's functionsare boring. Such tasks are not performed reliably over longperiods.Another potential problem is that the tasks "left over"from the machines may not form a coherent set. In thedevelopment of a two-place strike aircraft, the use of thisapproach resulted in the tasks of the pilot and systemsoperators being uncoordinated.Relative contributionSome users rate this as the best available method for simple systems. or for systems based on available equipment orsub-systems.ApplicationsThe technique was used for a recent major upgrade of a destroycr, the development of a two-place strike aircraft. andthe development of a mine-sweeper.cdQuality assurance considerationsThe lack of documentation and traceability limits the reliability of the technique. The most effective way of ensuringquality is to validate the function-allocation decisions using additional analyses, such as time lines or workloadpredictions. This is sometimes referred to as the "trial and error" approach (US Department of Defense, 1987).Relationship to system performance requirementsIn the destroyer upgrade project, the approach was used specifically to meet the contractual requirement thatperformance be at least as good as that of the predecessor system. Users have related the output to system performancethrough the modification and update of existing performance specifications.NATO UNCLASSIFIED49 -