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.

If we have some EE guys here, SparkFun electronics offers several IMU sensor system under $150: https://www.sparkfun.com/categories/160

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

To me the best vario would have audio the pilot can really relate to. This allows adjustments to thermal turns to be consciously made by the idiot behind the stick, while looking at the display usually marketed by Mecaplex.
Jim