The radius of turn, in feet, is given by the formula:
$
radius = \frac{v^2}{11.26\tan(Φ)}
$
where $v$ is the true airspeed of the aircraft in knots, and $Φ$ is the bank angle in degrees.
To improve turning performance and decrease turn radius, the pilot needs to increase bank angle, and/or decrease speed. For additional information, see *Radius of Turn* (pgs. 5-39 to 5-40) in the *Pilot's Handbook of Aeronautical Knowledge*.