First off the 40mm cannons rock. Second you are doing the wrong angle of attack. When attack heavily armored vehicals like the tiger, T34, Panzer, or Ostwind, you have to come diving down on them from above, where the only thing you see is the roof of the tank. Cut your throttle zoom in a close as you can and fire. This is how you disable or destroy a tank. Practice this offline on the tanks they have. Best to take off protect objects in your Arena Settings so you don't have to fly to enemy base then end up getting shot down.
