Thanks Gerry - that makes sense...I guess the only time you don't roll for target lock numbers is when Argentine aircraft is being attacked by warships in San Carlos Water during 'Naval Fire' in Surface to Air combat. There a '1' is enough to kill the aircraft (after rolling a die on the 1-mile range of the warship).
I think that's right! (I have misplaced my rules for the moment...)
You also roll a new target lock after radar lock for every new distance the incoming aircraft reach during Surface To Air Combat. The missile system(s) rating at the current range (lowest if multiple systems are in range) will determine which die is used.