During the Second World War, German pilots practised the vertical mounting of guns on their fighters, nicknamed "Schräge Musik" or "Strange Music" — this design allowed them to fly safely to the unprotected undersides of enemy bombers and destroy them unopposed.
And there are aircraft with this design in War Thunder: Bf 110 G-4, Ju 388 J, Do 217 N-2, Ki-45 tei and others are equipped with "Schräge Musik", try it yourself!
Assign the Aim button in Aircraft → "Schräge Musik" cannon activation, fly up to the enemy in combat from below, aim and fire!