On 10/3/2010 11:09 AM, Brad wrote:
On Oct 3, 10:44 am, wrote:

Brad, I thought your come back was funny and I certainly deserve it.

What I get from your opening thread is perhaps your reluctance to
trust the wind information you are seeing or you are looking for
supporting information that would increase your trust in the
information.
Transitioning to ridge would require accurate wind information, but
you write you do this without fear all the time.
If you would elaborate a little more on what you are thinking
regarding wind data , I'm sure others have helpful input and comments.
Myself , operating a 302 with a CAI M-25 backup...they become accurate
as long as I thermal and slowly diverge / degrade with long stretches
of glides. A few turns and I am amaze how quickly they recapture the
wind. I was able to run trials base on observation of smoke coming off
the burning sugarcane fields and learn my instrument.
R
I do feel confident that the wind information is reliable enough to
use within a certain amount of time/airspace. What I mean by that is
since I only get wind info from circling (with my set-up) it is good
only for a certain amount of time until I start circling again. So, If
I climb up and get wind info X, then start a long glide the wind could
be different when I finish my glide and I'll not know what it is until
I start circling again and get a new fix. Probably not a big deal when
I think about it.

It could be a big deal if you are ridge flying, or flying in the
mountains (that's' _in_ not _over_), or wave is present but not strongly
established. Under those conditions, the wind can change significantly
from where you last circled due to valley flows, mountain peaks/ridges
diverting the wind, or wave dipping down into the convection layer (or
coming and going as the speed, direction, and air mass change).

My experience is wind derived from circling is adequate for relatively
open areas, like the Columbia basin in Eastern Washington state, but
"current headwind" derived from an air-data vario like the my 302 is
very useful in the ridge/mountain/wave situations. And, of course,
during long glides (like a final glide), where the glider sinks
thousands of feet lower than the altitudes I at which I was circling and
getting wind measurements.

If wind is important to you, spend the money for an air-data instrument.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz