Document 5D7qX2VoBwYEreOBvaRnXgDyN

Human Factors Engineering V FlC 5-4 --Control B is designed to eliminate errors m the information-processing and machine con trolling functions (See Fig 5-13 ) Perceptual requirements near or be yond the physiological limits or that conflict with established perceptual patterns Response requirements that are phy sically difficult, conflict with established patterns, or cannot be readily checked or monitored for adequacy Decisions that require undue reliance on short-term memory or must be accom plished within too short a time interval in view of other necessary tasks Tasks that overload the human, resulting m imbalanced workload/time distribution, or do not permit adequate or timely monitor ing of the system Communication requirements that con flict with other activities Often, the man's contribution to a system is to provide a counter-measure in the event of system malfunction or component failure To do this he must know that a failure has oc curred and what to do about it Generally, displays provide the failure in formation and, therefore, must be designed to communicate such information to the oper ator The operator must then perform the proper response with the controls provided with a minimum of error-- yet it is at this point that breakdowns in the system frequently occur (Displays are discussed later, under "Function 1 --Man as Sensor") Task analysis Just as equipment can be designed to fit human limitations and capabilities, so, too, can jobs (or tasks) be designed for humans Human factors engineenng research has shown that man needs to be challenged but not overburdened If a job is to easy, too routine, that monotony, boredom, and even tually errors (and accidents) will become prevelant Machines have a built-in upper tolerance limit If an electncal circuit, for example, is overloaded, the fuse will blow and no harm to the system will result Man, on the other hand, does not have a "safety fuse box " He can work for short penods under overloaded conditions, e g, high production demands, however, when such an overload reaches some undefinable point, the human mav completely break down Such stress overloading may account for the co-worker who suddenly "flies off the handle " The task of the job designer, then, is to find the happy blend between "easy" and "diffi cult" jobs With very low levels of psycho logical stress (boring jobs) performance is also low, as stress increases, however, per formance also increases --to a point The task is to design jobs that will be cen tered around optimum performance (See Fig 5-5) How to predict task requirements Human tasks are predicted from the design of the equipment and from the tentative organiza- 106