On Mar 16, 11:19 pm, Ramy wrote:
On Mar 16, 7:07 pm, BB wrote:



I mean, when I think about it, I come to the conclusion that you
always have to (and can only) optimise your speed through the airmass
by flying MC (putting aside what that actually means in reality). If
the resultant XC speed given by MC theory is less than the windspeed,
well, you're stuffed.

Dan

That's correct. The assumption is that you're flying in thermals, and
thermals drift with the airmass. Actually thermals usually drift a bit
less than airmass, and if you've got ridge or wave, those are
stationary with respect to the ground. But otherwise, by definition
there is no way to fly faster than the optimum speed through the
airmasss -- the fact that the ground is moving around below you is
irrelevant.

John Cochrane

So the conclusion is that the wind has effect only on the final glide,
and requires adjusting the MC setting manually (and keep adjusting as
the wind changes) to optimize the glide over the ground, which in some
cases (long glides into significant head wind) will make the
difference between making it back or landing short. However, while
normally MC values can not be determined by the flight computer since
it doesn't know if,when and how strong the next climb will be, the MC
value for best final glide into the wind CAN be determined by the
flight computer. Wouldn't this be a useful feature, to be able to
select an auto MC for final glides?

Ramy

I think the conclusion is that the wind has effect on the altitude
required for the final glide, but not the speed that you would fly it
at. The speed is determined by the climb rate at the top of the last
thermal.

Some flight computers do an automatic MC setting for a final glide. I
think both Winpilot and Seeyou Mobile do this.

Todd