Rule of thumb for turning radius
Hi,
I was told in training as a general rule of thumb, 1% of G/S for 25-30 degree AOB for a 90 degree turn.
For example joining a DME arc at 90 deg with a G/S of 200kt, you need to initiate the turn 2nm before the arc so as not to overshoot the arc.
Of course we don't always join the DME arc at 90deg. Say if you join at 45deg, you need only 1nm in the above example.
Same applies for QDR intercepts if you are told to fly over a VOR to intercept a radial outbound.