Bill Daniels wrote:
OK, David, I hope you are right.

However, if the computer doesn't know the glider's heading, how does it
solve the wind triangle without turns? If the computer can't solve for the
true wind data how can it compute the headwind component?

The "headwind" = TAS - (Ground speed). It's the "effective" headwind
along your course (GPS ground track), not the actual headwind on the
glider's heading.


People keep telling me that TAS + or - Groundspeed will give a "good enough"
headwind/tailwind component. My experience is that the wind data gets very
stale during a long final glide.

Yes, and a way to handle in some glide computers is to manually update
the wind value in use, using the measured "effective" headwind.

After a few circles to get fresh wind data, the final glide numbers look a
lot different. If the wind shifts or I descend through a wind layer, I need
to know it RIGHT NOW.

The effective "headwind" seems to do this quite well, based on my
experience with a 302 and Glide Navigator (GN). GN also displays the
error between the effective headwind and the headwind calculated using
the last vector wind determination. If the error is more than a knot or
two, I know the vector wind has changed.

Of course, knowing it's changed doesn't tell you what it is, but once
alerted, I can circle or deviate my course to pick up the new vector
wind. For mountain flying, I'm often turning frequently anyway, so it
hasn't been the problem that the long straight glides in the open
sometimes are. Still, having an update to the vector wind every 20
seconds or so would be a nice.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA