Originally Posted by
john_tullamarine
One other advantage of having twin tails on a fighter
I suspect that the main reason is for high alpha manoeuvring with alignment of vortices shed from up front. Mind you, that has its own problems eg FA18 fatigue ..
You also get a nice freebie with tailoring the directional stability term (Nv or Cn-beta) with Mach number, too. At low M the twin fins aerodynamically interfere, reducing their effect, and as m increases the shock cones shield the fins from each other, increasing their effectiveness just as you start to need increase to compensate for the body destabilising effect increasing. It's not necessarily a reason in itself, but it helps tip the scales (and avoids having Tornado-sized fins!)