STUDIES OF HUMAN FACTOR IN PANEL DESIGN 



167 



performance will be. To a large degree, of 

 course, whether just finger and wrist motions 

 or motions involving the use of the shoulders 

 will be necessary depends a great deal upon 

 whether controls are placed within easy 

 reach of the operator or out on the periphery 

 of the practical working area. 



Relieving the Eyes of Work 



The biggest problem of this sort on the 

 display side is the overloading of the eyes. 

 The eyes can only do so much work in finite 

 time, but there has been a tendency, in the 

 design of equipment, to display most in- 

 formation visually. A few studies have in- 

 vestigated the possibihties of greater use 

 of other sensory modahties than vision to 

 get information to an operator. Some 

 aviation research has been devoted to this 

 question, for the display problem there is 

 as complex as anywhere. Both British and 

 American laboratories have experimented 

 with the use of auditory signals in the 

 attitude system of instrument flying (6, 16), 

 In the American system, called Flybar 

 (flying by auditory reference), it is recom- 

 mended that turn, bank, and airspeed indi- 

 cations be given by auditory signals of 

 different frequencies, intensities, and inter- 

 ruption rates to the two ears. In a pur- 

 suitmeter task, it has already been shown 

 that direction can be given by such auditory- 

 signals. The auditory indication is as good 

 as the visual when only one item of in- 

 formation is given; when two items are given 

 or all three, turn, bank, and airspeed, use of 

 the visual system is superior. More re- 

 search on this problem may work out more 

 practical methods for giving auditory in- 

 formation of this sort. 



Confusion Errors 



Since accurate and rapid identification of 

 controls and displays on a panel is an im- 

 portant prerequisite for efficient performance 

 by the human operator, it is necessary, in 

 the design of equipment, to guard against 

 any possible confusion of one control or 



display with another. In the case of many 

 controls and displays, their general appear- 

 ance, location, or mode of action are 

 sufficiently distinctive so that confusion 

 rarely occurs. But as panels become more 

 crowded and the same type of knob or dial 

 is used for more than one control or display, 

 greater demands are made on the operator's 

 discriminative capacities, and it becomes 

 necessary to take special precautions to 

 avoid the accidental use of one control or 

 display in place of another. In any prac- 

 tical panel design situation, three basic prob- 

 lems must be investigated if confusion errors 

 are to be reduced to a minimum: (1) finding 

 which controls or displays actually are con- 

 fused in the operation of equipment, (2) 

 determining what conditions will make 

 human discrimination the easiest and most 

 accurate, and (3) planning the arrangement 

 of panels and the design of controls and 

 displays so that as many as possible of 

 these conditions are satisfied. Some head- 

 way toward the solution of these problems 

 in the cockpit has been made in recent 

 studies in the Army Air Forces. 



In one investigation of aircraft controls 

 where 460 pilots were asked to describe one 

 error which they remembered making in 

 flight, it was found that about 50% of the 

 mistakes reported could be classified as er- 

 rors of confusion (13). Of these, 39% were 

 made on the throttle quadrant where the 

 throttle, propeller pitch, and gas mixture 

 controls are located. It turns out that 

 these three controls have diff"erent positions 

 on the quadrant in different types of air- 

 craft: in the B-25, the order from left to 

 right is throttle, propeller, and mixture; in 

 the C-47, it is propeller, throttle, and mix- 

 ture; and in the C-82, mixture, throttle, 

 propeller. The confusion in this case arises 

 from the fact that the pilot has learned to 

 rely on the kinesthetic cues arising from his 

 own movements to guide him in selecting 

 the proper control, yet the patterns of move- 

 ment learned in one airplane are in- 

 appropriate in other ones. It would be like 



