Approximation for Turn Radius

[your_dreamguy]

Hello,
I was flying to Mexico a few days ago. The approach to airport we were going to had a teardrop.
The captain I was flying with, stated we could approximate the radius of turn, using a formula. Radius of Turn approx equals 10% of groudspeed.
Does this formula really work? If the formula works, what does it mean? For example if your G/S is 180 KTS, then you could make a 360 degree turn of an airplane and the radius of the circle your groundtrack would trace would be 1.8 NM?
Also, what assumptions does this make? No wind conditions, using 30 deg of bank???
Finally, this formula wouldn't work in a teardrop scenario...would it? I would think for a teardrop, you would need the formula to calculate arc length of a circle.

Looking for your input.:confused:

[blackmail]

hello dreamguy,

hereunder some rules of thumb :

for a rate one turn : bank angle required = speed /10 + 8
e.g. 180kts = 18 + 8 = 26° bank angle.
associated turn radius = groundspeed(kts)/100 = turnradius in km
e.g. 180kts/100 = 1.8 km or
turn radius = groundspeed(kts)/200 = turnradius in nm
e.g. 180kts/200 = 0.9 nm ( assume here 1nm = 2km, which is accurate enough in our example. normally of course 1nm = 1852m).
kind regards,
bm,