108 THE DEVELOPMENT OF WEAPONS SYSTEM REQUIREMENTS 



where Ld = the collision course lead angle for perfect collision vectoring 



6 = the angle off the target's nose. 



A plot of the required collision course lead angle versus angle off target's 

 nose is shown in Fig. 2-30. The vectoring system computes this angle from 



50 



Qo 40 



;2 30 



q 10 



30 60 90 120 



ANGLE OFF TARGET NOSE, 6 (deg) 



150 



180 



Fig. 2-30 Collision Course Lead Angles Versus Angle off Target's Nose. 



the AEW radar measurements. It transforms this lead angle into a space 

 heading command which is transmitted to the interceptor. The pilot flies 

 the aircraft so that the heading as measured by the aircraft compass 

 corresponds to the vectoring system heading command. 



Distribution of Aircraft Headings due to Vectoring Errors. 



Because of errors in the vectoring system measurements, the commanded 

 heading does not always correspond to the correct collision-course lead 

 angle. In addition, the ability of the pilot to follow the commanded heading 

 is limited by the resolution of his display, compass accuracy, the aircraft 

 stability and control characteristics, and the distracting effects of the search 

 and acquisition functions he must perform just prior to lock-on. 



The diagram of Fig. 2-31 may be used for an analysis of the heading error 

 distributions. The uncertainties of the vectoring system cause errors to 

 develop in a sequence that may be examined as follows: 



The interceptor-target sight line established by the vectoring system may 

 differ from the true sight-target line by an amount which can be expressed 

 approximately as 



