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