February 21st 13, 01:04 AM
posted to rec.aviation.soaring
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Best performing Vario?
On Thursday, February 14, 2013 4:24:54 PM UTC-8, Bill D wrote:
On Thursday, February 14, 2013 3:19:21 PM UTC-7, Kimmo Hytoenen wrote:
After Argentina some competition pilots were quite disappointed
with the new variometers using acceleration to calculate lift. I
have not tested myself, just telling their opinion.
At 21:49 14 February 2013, John Galloway wrote:
If the butterfly -- or clearnav, with future software -- did
read
out 3 d
w=
ind 20 times a second, this would be a big advantage. Not
only could you
de=
tect lift long before F =3D MA gets the glider moving upward,
you could
tel=
l upward gusts from forward gusts and sideways gusts.
Dynamic soaring
might=
even become possible, or at least better energy extraction
from gusts.
Eve=
n the 302 has the necessary sensors, my impression is that
we're all
waitin=
g on the software development.=20
John Cochrane
Regarding gusts, the Butterfly website (in FAQ) already claims:
"A conventional variometer uses changes in air pressure (TE-
pressure, static- and total-pressure) to determine energy
changes the aircraft experiences. Butterfly Vario does the
same.
Additionally it uses an inertial sensing platform that allows for
real-time determination of airmass-movement and realtime
determination of wind. With this technology a pilot can judge
the difference between gust induced energy changes and
thermal induced energy changes."
John Galloway
Not sure, but I suspect they are mixing frames of reference. In theory, the way to do this is solve the TE equations in the inertial and air-data domains separately then compare them. A gust will show up strongly in the air-data but less so in the inertial data so a computer - or a pilot - can tell the difference.
A purely inertial vario will require a full IMU with GPS updating. These things are probably still too expensive for sailplanes but only just.
Sparkfun has several IMU systems under $150: https://www.sparkfun.com/categories/160
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