164 



PANEL DESIGN 



In following this system, then, the pri- 

 mary decision is made in the placement of 

 the main items in a group; then the allied 

 items are grouped around them in a pattern 

 that makes for easiest use by the operator. 

 Certain practical difficulties may be en- 

 countered in following this logic, how^ever. 

 For example, in some models of planes, it 

 was found that there was not enough room 

 to place the artificial horizon above the di- 

 rectional gyro, since both of these are large 

 case instruments. As an alternative ar- 

 rangement for such planes, it was decided 

 to place the artificial horizon to the right of 

 the directional gyro. Then the rate of climb 

 indicator and other associated instruments 

 were relocated in the best functional re- 

 lationship to the new positions of the basic 

 instruments. In actual test, it turned out 

 that there was very httle difference in per- 

 formance with these two alternative arrange- 

 ments when pilots were required to fly 

 prescribed courses on instruments (26). 

 Interestingly enough, of the fourteen pilots 

 studied in this situation, nine preferred the 

 second panel to the first. Both of these 

 items of information are important to know 

 in deciding between alternative panel ar- 

 rangements. 



Functional Grouping 



It has been pointed out frequently in 

 the literature that both controls and displays 

 are best used when arranged in functional 

 groups (11, 15, 25). While it can be ac- 

 cepted as a matter of common sense that 

 items on a panel that are used together 

 ought to be placed together, there has been 

 some disagreement over what makes up a 

 functional group. It should be made clear 

 that grouping of controls and displays ac- 

 cording to machine function does not always 

 make sense from the operator's point of 

 view. It has been pointed out, for example, 

 that pilots have to use flight instruments 

 and engine instruments together all of the 

 time, so that separation of engine and ffight 

 instruments would actually be detrimental 



to efficiency (20). What is needed is an 

 analysis of the behavior of an experienced 

 operator using his equipment. Then, when 

 it is learned which controls and displays are 

 used together, they can be arranged in func- 

 tional groups and patterns that will be the 

 least wasteful of motion and eye movements 

 and the easiest for the operator to carry out. 

 Not too much research has been done to 

 indicate what groupings of displays are the 

 best for human use, but some recommenda- 

 tions have been made. One analysis of air- 

 craft instruments suggests that they may be 

 classified according to w^hether they are to 

 be read quantitatively, qualitatively, or 

 merely given a check-reading. For instru- 

 ments to be check-read, it is suggested that 

 similar purpose items may be arranged in a 

 compact group in such a way that all the 

 indicators face in the same direction when 

 the instruments are set properly (8, 25). 

 In general, displays that are read in sequence 

 should be arranged so that eye movements 

 are kept at a minimum. Similarly, related 

 groups of displays should be located in re- 

 spect to each other so that they can be ob- 

 served one after the other with minimum 

 eye and head movements. By means of 

 eye movement studies it is possible to show 

 the sequence which an experienced operator 

 follows in reading instruments in normal 

 operation. Redesign of the panel layout 

 can then achieve the goal of minimum eye 

 and head movements. This sort of pro- 

 cedure has proven helpful in industry, and 

 can be applied successfully to tasks as com- 

 plex as piloting military aircraft. More ad- 

 vantage should be taken of this tool in the 

 study of optimal panel layouts. 



Analysis of Links 



Another procedure that might be used, 

 not only for the arrangement of displays, 

 but also for controls, is a technique 

 developed for the arrangement of men and 

 machines in a complex communications cen- 

 ter (9). Basically, the method is to deter- 

 mine the functional links that exist among 



