654 DISPLAY SYSTEM DESIGN PROBLEMS 



brightness or gain control for the pilot. The data in Fig. 12-26 indicate 

 definite optimum settings for the receiver gain and pedestal amplitude. 

 This, of course, applies to a particular display. Similar data should be 

 determined experimentally for the scope selected for the display being 

 discussed. 



Attack Display. After detection and lock-on, conversion to the attack 

 mode is effected and the aircraft is precisely flown along a straight-line 

 attack course to the missile launch point. The heading error relative to the 

 correct course must be displayed in such a manner that the tracking error 

 caused by the pilot is maintained at less than 1° rms as specified in Para- 

 graph 2-27. The time to launch must also be displayed as well as the 

 interceptor attitude. After launching, a breakaway symbol must be 

 presented when there is a danger of collision. 



The attack display will be specified to be very similar to the heading 

 error and attitude symbols in the search display. There will be a fixed 

 horizontal reference line across the center of the scope. Attitude will be 

 indicated by the motion of an inverted tee relative to this line. The motion 

 of this tee in response to roll and pitch of the aircraft will be identical with 

 that in the search display previously described. 



The attack course error will be indicated by a circle which moves relative 

 to the center of the scope. As in the search display, the size of the circle 

 will be proportional to the allowable error. The size of this circle will of 

 course be somewhat smaller than that for the vectoring phase. Time-to-go 

 until missile hit will be indicated by a thermometer type of symbol on one 

 side of the scope. Full-scale reading of the time-to-go thermometer will be 

 40 seconds. This type of attack display is illustrated in Fig. 12-35. 



The data in Fig. 12-33 can be used to determine the best choice of scope 

 sensitivity. These results establish that there is very little improvement 

 in pilot tracking performance with scope sensitivities greater than 2.5° /inch. 

 In general, a small scope sensitivity is desirable to give as large as possible 

 a linear dynamic range for the error. With 2.5° /inch on the 7-inch scope, 

 the dynamic range will be ±2.5° X 3.5 = ±8.8°. This should be sufficient 

 since a relatively smooth transition will be made from the vectoring display 

 where the error sensitivity is considerably less. The diameter of the error 

 circle with a radius corresponding to the 1° allowable tracking error will be 

 0.8 inch. This should be satisfactory. From Fig. 12-33b, the tracking error 

 with a scope sensitivity of 2.5° /inch is only slightly larger than the actual 

 noise on the scope. Thus, if the noise on the scope can be kept less than 

 1° rms per channel, the aircraft tracking accuracy will be within the 

 specified bounds. From these considerations, it is indicated that the attack 

 display illustrated in Fig. 12-35 will provide satisfactory performance, and 

 it is adopted as a satisfactory solution to the system requirement. 



