What is the best way to take out a tank? Bombs or can you use Aircraft 20mm or 30mm cannon fire? What about 50 cal. machine gun fire? 
Tanks you generally want to fly the IL-2 and Hurricane 2D - the IL-2 has the option for armored piercing 20mm or 37mm cannons (I suggest the 37mm), the Hurricane has a pair of 40mm cannons. The B-25H has a 75mm Cannon but its High Explosive (still a rear shot can destroy a tank) only thing is it handles like a dog.
You have to dive near vertical on the tank to destroy them, you can hit them from a flat straight line, problem is tanks will shoot back it still can be done though - if you use ZOOM to look at their turret when you are flying towards them you can
see if their turret is aimed at you or not.
If it is, I suggest climbing out, if not then continue an attack.