On Thursday, 6 May 2021 at 00:15:44 UTC+3, Eric Greenwell wrote:
"The mathematical system theory also answers the question under what conditions
a wind estimation is possible. In the case of a borderline case of an exact
straight flight movement and completely calm air, this is not possible. All
triangles are identical. We (Huang and Meyr) could show, however, that the
random changes in the air movement are sufficient to make the system
"observable.” "
--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

For wind vector you need two TAS-GS difference/track vectors. If they are identical (same direction of flight), you have no wind solution (as stated in paper). Optimum would be two vectors with 90 degrees difference, and measured in extremely short duration (this is how Oudie "live wind" tries to do it, though I haven't got it working). This would give an ok solution in circling flight, but at the same time the angular speed while circling is not very high, so sensing wind vector at different parts of thermal is rather slow (on steep turn with AIR Glide S gives you basically 20-25 separate wind measurements with 1 sec average). In straight flight Hawk is relying on miniscule differences in flight track. Instead of two wind vector components with 90 degree difference in direction they have vectors that have only few degrees difference on average. I would love to see someone comparing wind indications of Hawk and Glide S someday.