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Old June 21st 18, 02:44 PM posted to rec.aviation.soaring
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Default Vario Comparison

Hello Cristoph-

Thanks for your thoughts and insights. Much appreciated. Some comments interspersed below.

On Thursday, June 21, 2018 at 7:29:22 AM UTC-6, wrote:
Hi Gary,

I have flown with both, ClearNav (500h) and AirGlide varios (100h). I also used both in parallel last season. In terms of variometry, both varios have a comparable performance. In fact, the readings in climb mode were almost identical. But I preferred the AirGlide user interface, wind calculation and physical quality of the product, so I sold the CNv last year.

Regarding short latency with high accuracy: From my experience, the fastest latency with high accuracy rather depends on the quality of your TE probe than on the vario itself. There are significant differences in signal quality between different TE probes. Small latency is only needed while circling. In cruise mode you may want to have a longer latency in order not to be distracted with every single turbulence.

This is true when determining cruise speeds using S2F and related strategies, which I don't use. Since achieved XC velocities are relatively insensitive to precise cruise speed, a filtered average works well in S2F based methods. What I would like to find for what I am doing is something much faster during rapid transient events as a result of control inputs. Most of the modern varios claim "instantaneous" sensing but then something like "updated every second" which is very slow for my purposes.

Regarding TE compensation: Both varios offer TE probe and electronic compensation along with some kind of air-mass filter which reduces signals from horizontal gusts in cruise mode. With the AirGlide, this filter is based on inertial sensors - not sure about the ClearNav. TE probe compensation with both varios works well while electronic compensation of static pressure signal did not work at all with both varios in my setup (LS8 with fuselage side static sources). With TE probe compensation on an esa DN/ST probe, I used a slight electronic adjustment of 2-3%. This gave perfect results.

I have a good TE probe. The instrument is the weak link in my system. Are the inertial sensors only used to provide delta adjustments of the horizontal components, or do some of them use inertial input for vertical variation. If so, is this giving faster, reliable indications that aren't filtered through a 1 second gate?

The AirGlide offers a wide range of configuration option for the air mass filters and I am still working on the perfect setup. Seems that a longer integration time works better.

My personal opinion on the topic on how to determine air mass information: It is not a matter of the sensors being used. Even older analog varios gave a signal quality comparable to AirGlide and CNv - specifically Zander 820D / 940 / ZS1 and Westerboer VW910 varios (I consider older LX types to be worse in that respect). It is rather about what conclusion the pilot draws out of the data being presented. A good user interface simplifies that.


Thanks again for your inputs, Christoph.