"Bart" wrote in message
...
Anybody have a rule of thumb that helps break wind speed/dir into its
crosswind
headwind components?

Here are a few... the first two are most important, but put all four
together and it is all you need.

(1)
A 45 degree wind will have crosswind and headwind components of roughly 70
percent.

(2)
30 degrees (off the nose)- the crosswind is 50% and the headwind you can
round up to 90%.

(3)
For less than 30 degrees, the crosswind component versus the angle is close
to linear. In other words, for 15 degrees, 25% is close, 10 degrees, about
15-20%. Also, the headwind component is almost equal to the total wind in
this range, you might as well round it off. You can fudge the number by
subtracting 1 or 2 knots from your headwind if it makes you feel better


Here is an example:

Runway 14, wind 180 at 20 knots. The angle is 180-140=40 degrees. Pretty
close to 45... so use 75% and approximate the crosswind to 14 knots and the
headwind to 14 knots. Using a calculator I get 13 and 15- not bad!

Another example:

Runway 09, wind 070 at 15 knots. I get 20 degrees for the angle, that is
less than 30 degrees, in fact, it is 2/3 of 30, so instead of 50% I will use
2/3 of 50%. So, crosswind? 50% of 15 knots is 8, and 2/3 of that is 6.
Headwind? The angle is so narrow let's say 15 knots. The calculator says 5
knots crosswind and 14 knots headwind. If I had fudged the headwind down by
1 knot then I would have been right on.


And the last rule, which is really just the second and third ones over
again-

(4)
For greater 60 degrees and greater than 60 degrees, just switch the
crosswind and headwind rules with each other for the 30 and less than 30
rules.

(5)
Wait- a bonus rule, useful "on the fly" on cross country to get a crab
angle. 6 degrees equals 10 percent. So if you have a 10 knot crosswind and
you're going 100 knots, crab 6 degrees towards the crosswind. This will
give you a good starting point to correct your ground track from.


Hope this helps