Fee,
First off thanks for helping out. I did a test last night which involved the following.
1 A10C and 1 Shilka placed in map. I was engaged by shilka no triggers, waypoint options etc etc. A10C Blue and Shilka red.
1 SU-25T and 1 M163 Vulcan never engaged me with same settings above. Even put shots across his nose all he did was move a short distance never fired.