Just had a chat with some little schoolboys.....Their answer was:
180 Kts means 180 NM per hour....
divided by 60 minutes gives 3 NM / min
multiplied by 2 min (as in "standard turn") gives 6 NM which is the complete circle.
This divided by 3.1415 gives 1.9099 NM as the diameter
This divided by 2 gives
0.9549 as the radius....
The rule of thumb divides 180 by 200 which equals
0.9......
Now...where was the problem???
