On Friday, November 27, 2015 at 4:00:05 PM UTC, David Salmon wrote:
At 13:30 27 November 2015, wrote:
"This is a fundamental flaw in Flarm, which surely could be much improved
b=
y=20
building in a wind algorithm to correct the indication nearer to
heading.=
=20
All navigation programs have them."

As another poster mentioned, you really need a heading input to achieve
thi=
s. Whilst PNA's use drift while circling amongst other methods to
determin=
e the wind, they require frequent & sustained 'circles' to achieve this -
n=
ot so good for wave & ridge. LX quote 3 circles from memory and all the
op=
erating notes warn of the associated unreliability. An attempt to use an
a=
lgorithm to achieve this in Flarm would result in large variations in
accur=
acy. Sometimes the relative bearings provided would be correct and
sometim=
es, they wouldn't. Though currently an imperfect system, at least it's
con=
sistent.

CJ

I only mentioned wave to illustrate the extreme example. Some error is
always there unless you are flying straight up or down wind. It is far
from consistent, the amount depends on the wind speed and your angle to it,
two variables.
So whats wrong with flying 2/3 circles, I often circle in wave. In any case
Paolo Ventrafridda developed a method for LK8000, of flying S & L on one of
several headings for say 10 secs at a constant airspeed.
If the will is there, it can be done, and even if slightly imperfect, it
would be better than the present almost always wrong indication.
However another approach would be a way of manually putting the wind into
Flarm, using the vario/navigator readout, which I'm sure everyone flying
with Flarm, is equipped with as well.
Dave

My colleague corresponded with Flarm during our Scottish trial in 2007 about the possibility of correcting the track/heading difference by wind estimates from circling and they said they would look it it but never introduced it. One of the obvious issues is that the modes of flight during which this difference is most obvious (ridge and wave) are less likely to entail a lot of circling. Also in mountain ridge flying we are more likely to experience varying local winds.

I think that trying to do this would introduce too many uncertainties and different calculations between gliders.

Even without Flarm a pilot who can't figure out his track versus heading when ridge flying would be looking out the window in the wrong place for conflicting gliders.

John Galloway