2-27] 



ANALYSIS OF THE CONVERSION PROBLEM 



123 



firing. The maximum allowable launching error for a 10-second time of 

 flight may be plotted from the data of Fig. 2-42 as shown in Fig. 2-44. As 



10 



<o 



Op: 



30 60 90 120 150 



ANGLE OFF TARGET'S NOSE (deg) 



180 



Fig. 2-44 Maximum Allowable Launching Errors. 



can be seen, head-on and tail-on attacks impose the most severe require- 

 ments upon overall aiming accuracy. 



The functions and overall accuracy required from the fire control system 

 have now been defined. The next problem is to specify how this error is 

 to be divided among the possible sources of error in the system. 



Fire-Control System Error Specification. The sources of system 

 error can be listed as follows: 



(1) AI radar measurements [Rm^ Rm, Om, Lyi) 



(2) Flight-data measurements (altitude, speed) 



(3) Fire-control computation 



(4) Pilot-airframe-display interaction 



There are two general types of errors — predictable bias errors and 

 random errors. 



Predictable bias errors arise from the dynamic response characteristics 

 of the measuring device. For example, in the lead-collision system specified, 

 the variables R, R, L, and 6 can change rapidly as the launching point is 

 approached (Fig. 2-45). ^^ Dynamic lags in the measuring devices will cause 

 measurement errors whose values may be predicted from a knowledge of 

 the input parameters and the dynamics of the measuring device. The 



i-In this application, the system must continue to track after missile launch to provide 

 illumination for the missile seeker. Thus, dynamic lags are also important after missile launch 

 (r< 10 seconds); it will be noticed in this connection, that the dynamic inputs are quite 

 severe for this case. This point will be discussed further in Paragraph 2-29. 



