First work out your 'max drift'. This is simply the wind speed divided by your TAS (in nautical miles per minute) and the answer is in degrees - don't worry about why, it's all to do with 1 in 60 style approximation. So if the wind is 30 kts and your TAS is 90 Kts, max drift is 30 divided by 3/2, i.e. 20 degrees.
Then examine the angle between your track and the wind - and remember how an analogue watch face looks! Obviously if the wind was 90 deg off track, you'd apply all of max drift. If it was 60 off, you'd use 86.6%, 45 off 70.7%, 30 off 50%, etc, etc. But that's too hard, so if you assume that 60 or more degrees off is 1x max drift, 45 off is 3/4, 30 off is 1/2, 20 off is 1/3, 15 off is 1/4 (the same fractions as minutes of an hour) then it becomes close enough for approximate use and is easy. Thus if you're doing a TAS of 90 kts on a track of 050 and the W/V is 100/30, to maintain track you need to turn right by about 3/4 of the max drift of 20 deg, i.e. to a heading of 065 deg.
Similarly, consider the groundspeed. If the wind is 90 deg off, it should have no effect on GS, if it's on the nose it'll have 100% effect. So again you can use the 'clock code' - if the wind is 60 deg off use (90-60) as the clock fraction to use, i.e. 30 or 1/2 the wind strength. In the case above the wind was 50 off the nose, so you'd use 90-50=40, i.e. 2/3 of the windspeed (2/3 of 30 being 20) to apply to your TAS to obtain groundspeed - in this case it would become 70 kts. So what would have taken 7 minutes in still air will now take 9......
If you work out max drift before flight and draw the W/V on your map, you can fairly quickly come up with heading and GS without needing a whizz wheel! It's called 'Mental Dead Reckoning' or 'MDR', by the way. But don't forget to NB whether it's a head or tailwind that you're dealing with!!
[ 12 January 2002: Message edited by: BEagle ]</p>