do a search for collisions /ramming and or collision detection.
and no bombers aren't invunerale to ramming. The other day I had a spitfire ram into my il2 ,came in fast my low 6- hit the right wing from behind and I lost part of the wing. I jumped back to the tail gunner in time to see him come in then try to avoid collision...there were no guns firing-audible or visually. Watch actually relly cool - wish I had it on film...seemed like the collison was in slow motion. Sometime you get lucky and actually enjoy somehing like that.
of course, he flew off pretty much undamaged...
My query is - If i would've stayed in the pilots seat instead of jumping to the gunner posistion, would I have not "seen" the collision.
To gun or not to gun..that is the question.