I'm attempting to make a game similar to Ace Combat, and I'm still confused about banked turns, namely the speed of bank turning depending on the aircraft's roll.

Can I assume, for simplicity's sake, that it's something like Rgy = K * Rz, where Rgy is the rate of turning on the global Y axis (the banked turn's angular speed), Rz is the roll angle of the aircraft, and K is a constant? And if I can do so, how do I calculate K?