Lancaster201:
Now that your thoroughly confused, here's a very practical use for the 1:60 rule, especially if your GPS is T.U.
When passing abeam a station you can apply the 1:60 rule to determine your ground speed.
Examle:
You are 60 NM east of a VOR, on the 090 radial. You start your clock and note that it takes 3 minutes to cross 10 radials. Applying the 1:60 conversion ie 10 radials at 60 NM = 10 NM. It took you 3 minutes to go 10 miles therefore your present groundspeed is 200 Kts. (60/3=20 x 10 =200).
Another practical use of the 1:60 rule is using your Radar to determine the approximate tops of Convective Clouds.
Example:
You are 60 NM (radar distance), away from a CB maintaining 9000'. You notice that it takes about 7 degrees of up tilt on your radar to make the image dissappear from your screen. If we apply the 1:60 rule, we arrive at the following. 7 degrees at 60 NM = 7 miles. One mile = 5280' so 7 miles = 36,960'. Now add your a/c altitude of 9,000'+ 36,960' and we get 45,960'. So now you have an approximation of the tops of cloud. This will give you a pretty good idea of how much of a course deviation you will need to avoid the nastier WX.
The above calculation is only a 'rule of thumb' and only for an approximation. I know someone may want to comment on the use of the statute mile conversion of 5280' but I think everyone can remember that one.
Hope this helps.
Cheers, OffshoreIgor
PS. Never let your aircraft take you where your brain hasn't already been in the last five minutes.
[This message has been edited by offshoreigor (edited 07 December 2000).]