652 DISPLAY SYSTEM DESIGN PROBLEMS 



We suppose that the AI radar system has parameters similar to those in 

 the example of Sec. 3-2 with a beamwidth of about 4° and a 1-Msec pulse 

 width. If the 60° azimuth scan pattern is presented over the full 5 inches, 

 only 60° /4° = 15 horizontal resolution elements are required. The vertical 

 resolution, however, must be quite good, since there will be 20 X 12 = 240 

 1-microsecond range elements within the 20-n.mi. maximum range. The 

 number of vertical elements per inch will be 48, allowing a 21-mil spot size. 

 In order to be on the safe side, we will require a spot size of 10 mils, which 

 is a practical goal. 



In order to present information on the azimuth and elevation look angles 

 of the antenna, separate strobes will be required. The azimuth strobe is 

 specified to move horizontally below the B display with the elevation strobe 

 moving vertically at the side of the display. Range strobes can also be 

 conveniently used to bracket the expected target ranges and reduce the 

 uncertainty volume which the pilot must scan during detection. 



It is desirable that the display of heading command or error and aircraft 

 attitude not overlay the B pattern, as the flight information can very easily 

 mask a faint target. Unfortunately, there would not be room on a 7-inch 

 scope for both the B display and the flight information separately, and 

 the search presentation will have to be overlaid. In order to minimize any 

 deterioration in the detection function, we shall specify the use of a two- 

 color tube to present the search and flight data in two diff"erent colors. 



There are several possibilities for the presentation of heading information. 

 One would be to display a plan view of the locations and courses of both the 

 interceptor and target in order to give the pilot a good idea of the general 

 tactical situation. This type of presentation will allow considerable 

 flexibility in the pilot's selection of the most appropriate type of approach. 

 A typical display of this type was illustrated in Fig. 12-3. Because of the 

 small scale required to represent the large distances involved, however, the 

 accuracy with which a desired course will be flown might be marginal. An 

 alternate possibility, where the approach doctrine is prescribed, is simply 

 to present the heading error. Greater vectoring accuracy can be obtained 

 in this manner and possibly a smoother transition to the track mode at the 

 expense of restriction to a single mode of approach. The vectoring doctrine 

 originally adopted in Paragraph 2-11, which applies to this AI example, 

 actually contemplates a single type of vectoring, i.e., a collision approach 

 to minimize bomber penetration. 



The type of display of heading commands which has been selected for 

 the present example is simply to present the heading error or deviation 

 from the computed collision course rather than the complete tactical 

 situation. This will be accomplished by horizontal movement of an error 

 circle along a horizontal reference line. The size of the error circle will 

 represent the allowable piloting error during vectoring, which was specified 



