2-28] 



LOCK-ON RANGE AND LOOK-ANGLE REQUIREMENTS 



133 



Limits of Correctable 

 Steering Error ±36° 



H- 



R=8 n.mi, 

 e.=60° 



Heading Error 

 Distribution o-=21,5' 



Area of 

 Siiaded Region =Pc 



LEAD ANGLES 



62.5 



Fig. 2-51 Method for Calculating Conversion Probability. 



The calculation of conversion probability by this technique is approxi- 

 mate. Certain kinematic effects such as the change of collision-course 

 lead-angle with time-to-go and the effects of initial steering error on the 

 ultimate attack course flown by the pilot are neglected. Evaluation of these 

 effects requires elaborate simulation programs. In a practical case, it is 

 usually desirable to investigate these areas by more elaborate techniques. 



This simplified analysis, repeated for many values of lock-on range and 

 aspect angle, culminates in curves like those in Fig. 2-52. Notice that as 

 one would expect, the head-on attack provides the most stringent require- 

 ments for lock-on range. The assumed system requirement stated that the 

 conversion probability must be at least 0.825 for any aspect angle. The 

 corresponding viewing probability requirement was 0.95. Thus for this 

 hypothetical system approximately 10 n.mi. lock-on range is required to 

 achieve the requisite conversion probability. 



The look-angle requirements are dictated by vectoring considerations, 

 since the collision-course lead-angle is greater than the lead-collision-course 

 lead-angle for the same range and aspect angle (see Fig. 2-48). From 

 Fig. 2-34 we may determine that a 10 n.mi. lock-on range and a vectoring 

 probability requirement of 0.95 combine to dictate a look-angle capability 

 of 67°. 



