[Kyt]

A simple question. What principals made for a good fighter aircraft during WW2?

Why were some aircraft outstanding and others mediocre or just plain usless? Leave aside tactics and crew proficiency - let's concentrate on the machine.

For every ying there has to be a yang - range limited armour, armour affected speed, etc.

If you had to design your own fighter aircraft what would you consider the most important features? No flights of fancy (no pun intended), designs must within acceptable limits of what was available during the war.