AA Butterfly versus CNv LCD wind calculation

On Friday, September 16, 2016 at 1:23:48 PM UTC-7, wrote:
The Air Avionics Butterfly has developed an outstanding reputation as having a competitive advantage for its ability to "instantaneously" calculate wind direction.

Does the CNv (with latest 3.3.3899 or beta 3.4.4089) calculate wind as quickly as the Butterfly?

T8, what is the wind direction update rate of the CNv?

If anyone has experience using both varios at the same time, please share your opinions.

The Air Vario updates the wind once a second and calculates it much more often than that.

When I first began using it, I was skeptical, but have come to pretty much believe what it says. Every time I thought it had a surprising value, in any situation I could confirm, it was correct. I have discovered convergence lines, shear lines, and wave using it. I have also discovered some local weather patterns which can be exploited, no one else seems to know they are there nor did I, until the Air Vario.

I thought accurate straight line glide computer wind accuracy required a fixed compass (aka LXNAv) for the best not thermaling wind detection sensitivity. My S10 is going to have a compass module shortly. But I really can't imagine a need that that much wind accuracy. The wind where you are now isn't the problem. It's accurate anticipation of what the wind is 1, 5 10 and 20 miles ahead, just like sailing, but much less critical.

Am I right or wrong on the compass module?

I believe the butterfly an fixed compass built in, and this is the reason that it is more energetic on updates? Correct?

On Monday, September 19, 2016 at 2:42:36 AM UTC+2, Sean wrote:
I thought accurate straight line glide computer wind accuracy required a fixed compass (aka LXNAv) for the best not thermaling wind detection sensitivity. My S10 is going to have a compass module shortly. But I really can't imagine a need that that much wind accuracy. The wind where you are now isn't the problem. It's accurate anticipation of what the wind is 1, 5 10 and 20 miles ahead, just like sailing, but much less critical.

Am I right or wrong on the compass module?

I believe the butterfly an fixed compass built in, and this is the reason that it is more energetic on updates? Correct?

There is no need for a compass module with S8x/S10x, the wind calculating system is doing a fine job in straight flight.
I have flown about 150h with the S80 this year, and I’m still surprised every time I take off that the wind calculation is accurate already in the tow. I measure this by comparing the wind vector before and after the first thermal after release and they are more or less the same in most situations.

On Monday, 19 September 2016 03:42:36 UTC+3, Sean wrote:
I thought accurate straight line glide computer wind accuracy required a fixed compass (aka LXNAv) for the best not thermaling wind detection sensitivity. My S10 is going to have a compass module shortly. But I really can't imagine a need that that much wind accuracy. The wind where you are now isn't the problem. It's accurate anticipation of what the wind is 1, 5 10 and 20 miles ahead, just like sailing, but much less critical.

Am I right or wrong on the compass module?

I believe the butterfly an fixed compass built in, and this is the reason that it is more energetic on updates? Correct?

There are ways to calculate wind vector on straight flight without compass module, Oudie claims to do it by comparing track/gs to different straight paths (did not get it to work, though), so it is possible at least theoretically.

But bottom line is: you either have full inertial platform with 3D acceleration, rate gyros and compass data, or you don't. Former gives you instant airmass data in all directions instantly, if implemented correctly. That's big IF.

It is not enough to throw in electric compass if the system is not up to it.. Many variometer systems have compass option that manufacturers do not use for any meaningful data. Representative of one company told me of pilot who was very happy after installing optional compass module. He didn't have the heart to tell pilot that variometer firmware version couldn't use compass data at all. I always take pilot reports with a grain of salt.

And no, we do not *need* anything, you can fly perfectly well with seat-of-pants feeling. It just nice to have all that data.

Only compass that works as a data source for wind vector calculations, to my knowledge, is the Zander's. Of course, it is part of the Zander system (can't add the Zander compass interface to instruments by other manufacturers).

I would discourage anyone from adding an electronic compass module to their existing computers, as it's just not working properly. Probably due to extreme sensibility to pitch changes, and software unable to correct that.
If on a low budget, buy a working, used Zander set.
If on a higher budget, try the newer inertial varios.

I agree that accurate and real-time wind calculation is of very high interest to soaring techniques. I used it for years and I just can't adapt to fly woithout it.

all IMVHO, of course!

Aldo Cernezzi




It is not enough to throw in electric compass if the system is not up to it. Many variometer systems have compass option that manufacturers do not use for any meaningful data. Representative of one company told me of pilot who was very happy after installing optional compass module. He didn't have the heart to tell pilot that variometer firmware version couldn't use compass data at all. I always take pilot reports with a grain of salt.

tiistai 27. syyskuuta 2016 16.50.57 UTC+3 kirjoitti:
Only compass that works as a data source for wind vector calculations, to my knowledge, is the Zander's. Of course, it is part of the Zander system (can't add the Zander compass interface to instruments by other manufacturers).

I would discourage anyone from adding an electronic compass module to their existing computers, as it's just not working properly. Probably due to extreme sensibility to pitch changes, and software unable to correct that.
If on a low budget, buy a working, used Zander set.
If on a higher budget, try the newer inertial varios.

I agree that accurate and real-time wind calculation is of very high interest to soaring techniques. I used it for years and I just can't adapt to fly woithout it.

all IMVHO, of course!

Aldo Cernezzi



Even Zander compass was very sensitive to installation. I installed one Zander system to a LS8 for WGC years ago and calibrated it with factory calibration compass. It worked fantastically giving very accurate readings. After that my club bought similar system to D2 and it didn't work at all, even after many calibration attempts. I have flown third glider with similar setup, and that also did not work. We never understood why. With current knowledge of compass sensor installation problems, there might have been speaker or something too close to compass.

On Sunday, September 18, 2016 at 5:42:36 PM UTC-7, Sean wrote:
I thought accurate straight line glide computer wind accuracy required a fixed compass (aka LXNAv) for the best not thermaling wind detection sensitivity. My S10 is going to have a compass module shortly. But I really can't imagine a need that that much wind accuracy. The wind where you are now isn't the problem. It's accurate anticipation of what the wind is 1, 5 10 and 20 miles ahead, just like sailing, but much less critical.

Am I right or wrong on the compass module?

I believe the butterfly an fixed compass built in, and this is the reason that it is more energetic on updates? Correct?

The Butterfly (Air) vario wind is inertially derived and calculated many times a second. As far as I know they are the only ones really doing this. I'm pretty sure they use air speed, GPS speed, etc for long term calibration, but the instantaneous wind is derived from the MEMS sensors. For example I will get an accurate instantaneous wind in my motorglider with the engine running. The tail pitot is in the prop wash and indicates about 45 knots over the actual speed. The Oudie or XCSoar will say I have a 45 knot headwind whenever it is running. The Air vario gives accurate wind, even with it running.

It is pretty difficult to get an independent verification of the wind vector. Headwind and tailwind component not that hard in stable conditions. Circling, unless very close to the ground, will only give you a vague notion. In the western mountains at least, the wind is quite dynamic in and around thermals, a fact that iGlide uses as a thermal centering device.

The instantaneous wind IS of immediate interest at least some times. I have found many days (in western mountains again) when there is a rather abrupt shear at say 14,500 ft. The cloud bases are 15,500. But you are heading upwind. When you hit the shear you leave the thermal. Going downwind, obviously carry it right to the cloud. This information is verifiable by checking TAS agains GPS speed. But most soaring instruments determine this too late to be of much use. There are other times when wave was dipping into the boundary layer again producing a sudden change of instantaneous wind. When I saw this I knew to look around for wave. I have discovered there is often a strong south wind blowing up the Minden valley late in the afternoon above about 12,000 ft. Never saw that before on other instruments, I'm not in it long enough for their filters to figure it out. Yet it can be exploited by flying down the middle of the valley rather than cutting straight across which seems otherwise more logical. Again these readings can be verified by observing TAS and GPS speeds.

On Friday, September 16, 2016 at 4:23:48 PM UTC-4, wrote:
If anyone has experience using both varios at the same time, please share your opinions.

When you have 2 or more systems how can you possibly know which wind reading is more accurate?
Without flying in a giant laboratory with controlled winds how do you know what the truth is to compare each system to?
I would imagine each system needs to average the data over some time period, so unless you can set them to be the same how can you tell?
If you make note of the in flight wind indications then reviewed that part of the flight in SeeYou would that be useful?

Chris

Actually in some conditions it is very easy. Stop and circle. I find in mountains and along shear lines that the wind can change 30 to 180 degrees in a very short distance. Many traditional varios and computers will take 10 to 15 minutes to adjust.

Do you really fly a perfect circle of constant radius? I certainly
don't. I think without that, the wind calculation is really a best
guess based on the assumption that you're flying a circle. One could
argue that an accurate wind calculation is necessary to fly the correct
drift angle to your target, but this is soaring. Who flies in a
straight line?

On 9/18/2016 10:05 PM, Tim Taylor wrote:
Actually in some conditions it is very easy. Stop and circle. I find in mountains and along shear lines that the wind can change 30 to 180 degrees in a very short distance. Many traditional varios and computers will take 10 to 15 minutes to adjust.

--
Dan, 5J