Well, this is one of the cases where you can admire how realistic the AI is:
- they instantly know where you are no matter what. You need to get to 4.3 km, they shoot at you from 4.5 km. If you play hide and seek you're dead.
- If on the other hand you just fly straight at them they won't shoot at you even if you get close enough to shake their hands. They might shoot at you when you've passed them and fly away again.
- So, if I want to shoot tanks I go to a sufficient altitude, stabilize in their direction, engage altitude hold (or adjust collective to fly level) and fly towards them at around 120 km/h. Shoot one or two, turn around, maybe weave through the buildings to feel important and then just rinse and repeat.
I don't need to tell you how realistic this is but it works...