Where is the LX S80?

[[email protected]]

Supposed to be released in March 2014.
Looks like a direct competitor to the Butterfly vario.
Anyone actually have one?

[Richard[_9_]]

On Friday, September 19, 2014 10:06:34 AM UTC-7, wrote:
> Supposed to be released in March 2014.
>
> Looks like a direct competitor to the Butterfly vario.
>
> Anyone actually have one?

I am told I should have some at the end of this month or first part of October. Most are sold but have a couple available.

Richard
www.craggyaero.com

[[email protected]]

> Looks like a direct competitor to the Butterfly vario.

I wonder if it will have a similar vertical airmass indicator based on inertial reference that essentially eliminates horizontal gust induced energy changes like the Butterfly vario does. I am hoping there will be a dedicated indicator for this reading that can be directly compared to the "regular" vario indicator to help determine if that lift indication is due to a horizontal gust or not.

The specs make no mention of a magnetometer, only a gyro based system. Curious how this effects instantaneous wind calculations.

[[email protected]]

> The specs make no mention of a magnetometer, only a gyro based system. Curious how this effects instantaneous wind calculations.

A careful reading of the literature on the S80 shows that a magnetic compass module is needed for instantaneous winds.

[jfitch]

On Friday, September 19, 2014 2:18:08 PM UTC-7, wrote:
> > The specs make no mention of a magnetometer, only a gyro based system. Curious how this effects instantaneous wind calculations.
>
>
>
> A careful reading of the literature on the S80 shows that a magnetic compass module is needed for instantaneous winds.

That kind of suggests that the wind is really calculated from GPS/TAS/Heading, doesn't it?

On the Butterfly, wind is inertially derived and truly instantaneous - like 20 times per second. If you use iGlide you can see this in the thermal assistant: every second there is a proportional lift dot, in each lift dot is an instantaneous wind direction arrow, and (at least in nicely organized thermals) these point towards the center of the thermal.

[jherzog]

The user's manual for the S80 is now available (http://www.lxnav.com/downloads/manuals/LXS80ManualEnglishVer0500.pdf) so hopefully it will be available in the U.S. soon.

I'm interested in one to replace my Cambridge LNAV/SNAV/vario combination, which will free up two instrument holes. I would like to see a few initial reports from users before pulling the trigger on purchasing.

[Richard[_9_]]

On Wednesday, October 8, 2014 9:05:56 AM UTC-7, jherzog wrote:
> The user's manual for the S80 is now available
>
> (http://www.lxnav.com/downloads/manuals/LXS80ManualEnglishVer0500.pdf)
>
> so hopefully it will be available in the U.S. soon.
>
>
>
> I'm interested in one to replace my Cambridge LNAV/SNAV/vario
>
> combination, which will free up two instrument holes. I would like to
>
> see a few initial reports from users before pulling the trigger on
>
> purchasing.
>
>
>
>
>
>
>
>
>
> --
>
> jherzog

I should have some LXNAV S80 vario systems in a couple of week. Since they are similar to the LXNAV V7 except for the software I would expect few problems.

Richard
www.craggyaero.com

[[email protected]]

What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?

The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.

[Richard[_9_]]

On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
> What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>
>
>
> The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.

Where did you see that a compass module can be connected to a S80? I did not see that in the manual.

S80
Inertial platform 3 axis digital +-8g accelerometer, 3 gyroscopes (for inertial vario, AHRS and wind calculation)

The question about the difference between the butterfly and the S80 is probably proprietary information for both companies.

Richard
www.craggyaero.com

[jfitch]

On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
> What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>
>
>
> The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.

There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).

It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.

[[email protected]]

If you go to Cumulus Soarings website and read the information on the S80 it makes a short mention of the compass module.
Then if you go to the compass module section of his catalog it says it is for the S80.

[[email protected]]

There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.

I want to hear from LX how the winds are computed.

[[email protected]]

On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
> There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
>
>
>
> I want to hear from LX how the winds are computed.

Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"

http://www.lxnav.com/products/lxnav-varios/s80.html

The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.

Interesting feature is ability to set the battery chemistry and battery warnings.

[[email protected]]

Thank you for reading the S80 manual so closely. The internal conflicts are important.

I am trying to decide on the Butterfly vario vs the S80. The sophistication of the Butterfly ICU really draws me in but then I get confused when the company that makes the FLARM unit has such a poor FLARM display and funtionality in their Butterfly Vario.

Then the S80 release is delayed and delayed and delayed and the manual does not clear the air on some fundamental questions.

[jfitch]

On Wednesday, October 8, 2014 7:47:11 PM UTC-7, wrote:
> On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
>
> > There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
>
> >
>
> >
>
> >
>
> > I want to hear from LX how the winds are computed.
>
>
>
> Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"
>
>
>
> http://www.lxnav.com/products/lxnav-varios/s80.html
>
>
>
> The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.
>
>
>
> Interesting feature is ability to set the battery chemistry and battery warnings.

It is curious that it has no magnetometer and no GPS. I wonder how they stabilize the AHRS? AHRS hardware included in every unit but it costs $1120 to turn it on? No GPS so no flight recorder function? S80 + Nano + AHRS option seems quite a bit more $$ than the Butterfly which includes all those functions and more? And you still need an external compass?

There must be more to the story than we know, because right now it doesn't seem to add up.

The Butterfly lacks a good Flarm display (by design, they claim), but gives excellent Flarm voice warnings which are quite a bit more useful. Still, I would like to see a good Flarm display.

[s6]

Le vendredi 19 septembre 2014 13:06:34 UTC-4, a écrit*:
> Supposed to be released in March 2014.
>
> Looks like a direct competitor to the Butterfly vario.
>
> Anyone actually have one?

There is a new inertial vario on the market from Australia called Vaulter

at; WharingtonSmith.com

[[email protected]]

Bad address.

[s6]

Le vendredi 19 septembre 2014 13:06:34 UTC-4, a écrit*:
> Supposed to be released in March 2014.
>
> Looks like a direct competitor to the Butterfly vario.
>
> Anyone actually have one?

This one works;

rbe-avionik.de

[Richard[_9_]]

On Wednesday, October 8, 2014 7:47:11 PM UTC-7, wrote:
> On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
>
> > There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
>
> >
>
> >
>
> >
>
> > I want to hear from LX how the winds are computed.
>
>
>
> Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"
>
>
>
> http://www.lxnav.com/products/lxnav-varios/s80.html
>
>
>
> The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.
>
>
>
> Interesting feature is ability to set the battery chemistry and battery warnings.

I heard from LXNAV

Compass can be connected via can bus. In the moment compass is not available.
Maybe some sounds are not implemented , but will be in future releases.

Concerning Winds: I have both the PowerFlarm-V7-Ultimate Le system and the Butterfly Vario in my glider. I do not see a significant difference in the wind calculation between the systems. Approx 400 hours of flying comparing the systems.

Richard
www.craggyaero.com

[jfitch]

On Thursday, October 9, 2014 7:31:08 AM UTC-7, Richard wrote:
> On Wednesday, October 8, 2014 7:47:11 PM UTC-7, wrote:
>
> > On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
>
> >
>
> > > There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > I want to hear from LX how the winds are computed.
>
> >
>
> >
>
> >
>
> > Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"
>
> >
>
> >
>
> >
>
> > http://www.lxnav.com/products/lxnav-varios/s80.html
>
> >
>
> >
>
> >
>
> > The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.
>
> >
>
> >
>
> >
>
> > Interesting feature is ability to set the battery chemistry and battery warnings.
>
>
>
> I heard from LXNAV
>
>
>
> Compass can be connected via can bus. In the moment compass is not available.
>
> Maybe some sounds are not implemented , but will be in future releases.
>
>
>
> Concerning Winds: I have both the PowerFlarm-V7-Ultimate Le system and the Butterfly Vario in my glider. I do not see a significant difference in the wind calculation between the systems. Approx 400 hours of flying comparing the systems.
>
>
>
> Richard
>
> www.craggyaero.com

Richard, how do the winds compare in instantaneous changes? Also what to you have the wind filter set to?

I don't have a V7 (never seen one) but it appears to calculate winds by the traditional schemes: either thermal drift or GPS track velocity compared to heading and airspeed. On my Butterfly, in steady state conditions the inertial wind compares with the traditionally derived schemes as seen on PDA, Cambridge, etc. However the Butterfly reports momentary abrupt changes in wind in and around thermals, and sometimes during glides, that these traditional methods miss entirely. Based on other available data, I believe the Butterfly is correct.

If you fly with iGlide, Butterfly uses the rapid instantaneous wind changes in thermals for their thermalling assistant, which presents a wind direction arrow in each lift dot each second. At least in well organized thermals, the instantaneous wind reliably points towards the center of lift, and can be used to center.

At other times (notably on final glides over the Carson valley heading back to Truckee) there will be a sudden increase in wind that lasts for many minutes (or perhaps an altitude band, or geographic location) before reverting the the prevailing wind. For example it will go from 8 knots southwest to 28 knots south for 5 minutes, then back - as reported by the Butterfly. This can be confirmed by comparing GPS to TAS. After some time, the traditional methods will agree. When the strong wind is cross, the traditional method may never show it, while the Butterfly does.

My conclusion is that in steady state, and particularly for headwind/tailwind components, averaged over some time, the traditional and inertial methods agree well. But the traditional methods miss a lot of rapid changes and there are times when this is significant.

One problem with observing every change in wind is that if final glide calculations are based on them, you see it varying rapidly as wind gradients are encountered. As far as I know, the Butterfly itself has no way to set the averaging filters differently for final glide calcs, which would be desirable.

A curiosity (but proof of Butterfly's method) is that while the engine in my ASH26e is running, traditional wind calculation is off by a huge amount since the tail pneumatics are in the prop wash. However the Butterfly correctly calculates the wind during engine runs.

[[email protected]]

Excellent questions and observations.
I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.

[Richard[_9_]]

On Thursday, October 9, 2014 9:36:20 AM UTC-7, jfitch wrote:
> On Thursday, October 9, 2014 7:31:08 AM UTC-7, Richard wrote:
>
> > On Wednesday, October 8, 2014 7:47:11 PM UTC-7, wrote:
>
> >
>
> > > On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
>
> >
>
> > >
>
> >
>
> > > > There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > I want to hear from LX how the winds are computed.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > http://www.lxnav.com/products/lxnav-varios/s80.html
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Interesting feature is ability to set the battery chemistry and battery warnings.
>
> >
>
> >
>
> >
>
> > I heard from LXNAV
>
> >
>
> >
>
> >
>
> > Compass can be connected via can bus. In the moment compass is not available.
>
> >
>
> > Maybe some sounds are not implemented , but will be in future releases.
>
> >
>
> >
>
> >
>
> > Concerning Winds: I have both the PowerFlarm-V7-Ultimate Le system and the Butterfly Vario in my glider. I do not see a significant difference in the wind calculation between the systems. Approx 400 hours of flying comparing the systems.
>
> >
>
> >
>
> >
>
> > Richard
>
> >
>
> > www.craggyaero.com
>
>
>
> Richard, how do the winds compare in instantaneous changes? Also what to you have the wind filter set to?
>
>
>
> I don't have a V7 (never seen one) but it appears to calculate winds by the traditional schemes: either thermal drift or GPS track velocity compared to heading and airspeed. On my Butterfly, in steady state conditions the inertial wind compares with the traditionally derived schemes as seen on PDA, Cambridge, etc. However the Butterfly reports momentary abrupt changes in wind in and around thermals, and sometimes during glides, that these traditional methods miss entirely. Based on other available data, I believe the Butterfly is correct.
>
>
>
> If you fly with iGlide, Butterfly uses the rapid instantaneous wind changes in thermals for their thermalling assistant, which presents a wind direction arrow in each lift dot each second. At least in well organized thermals, the instantaneous wind reliably points towards the center of lift, and can be used to center.
>
>
>
> At other times (notably on final glides over the Carson valley heading back to Truckee) there will be a sudden increase in wind that lasts for many minutes (or perhaps an altitude band, or geographic location) before reverting the the prevailing wind. For example it will go from 8 knots southwest to 28 knots south for 5 minutes, then back - as reported by the Butterfly. This can be confirmed by comparing GPS to TAS. After some time, the traditional methods will agree. When the strong wind is cross, the traditional method may never show it, while the Butterfly does.
>
>
>
> My conclusion is that in steady state, and particularly for headwind/tailwind components, averaged over some time, the traditional and inertial methods agree well. But the traditional methods miss a lot of rapid changes and there are times when this is significant.
>
>
>
> One problem with observing every change in wind is that if final glide calculations are based on them, you see it varying rapidly as wind gradients are encountered. As far as I know, the Butterfly itself has no way to set the averaging filters differently for final glide calcs, which would be desirable.
>
>
>
> A curiosity (but proof of Butterfly's method) is that while the engine in my ASH26e is running, traditional wind calculation is off by a huge amount since the tail pneumatics are in the prop wash. However the Butterfly correctly calculates the wind during engine runs.

I usually fly with my wind filter in the Butterfly at 20 sec. I agree with you for the traditional and inertial for final glide. Also the V7 uses some inertial assist. I have it set to 4 of 4 . I also have the butterfly set to 50% for vertical airmass filter Inerital vs TE.
If you want to set the wind filter at l or 2 sec you can see rapid wind changes with the butterfly but I am more concerned with the final glide winds..

I don't see a way to change the butterfly filter just for final glide. That is a question for Marc at Butterfly.

Richard
www.craggyaero.com

[jfitch]

On Thursday, October 9, 2014 10:55:48 AM UTC-7, Richard wrote:
> On Thursday, October 9, 2014 9:36:20 AM UTC-7, jfitch wrote:
>
> > On Thursday, October 9, 2014 7:31:08 AM UTC-7, Richard wrote:
>
> >
>
> > > On Wednesday, October 8, 2014 7:47:11 PM UTC-7, wrote:
>
> >
>
> > >
>
> >
>
> > > > On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > I want to hear from LX how the winds are computed.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > http://www.lxnav.com/products/lxnav-varios/s80.html
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > Interesting feature is ability to set the battery chemistry and battery warnings.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > I heard from LXNAV
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Compass can be connected via can bus. In the moment compass is not available.
>
> >
>
> > >
>
> >
>
> > > Maybe some sounds are not implemented , but will be in future releases.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Concerning Winds: I have both the PowerFlarm-V7-Ultimate Le system and the Butterfly Vario in my glider. I do not see a significant difference in the wind calculation between the systems. Approx 400 hours of flying comparing the systems.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Richard
>
> >
>
> > >
>
> >
>
> > > www.craggyaero.com
>
> >
>
> >
>
> >
>
> > Richard, how do the winds compare in instantaneous changes? Also what to you have the wind filter set to?
>
> >
>
> >
>
> >
>
> > I don't have a V7 (never seen one) but it appears to calculate winds by the traditional schemes: either thermal drift or GPS track velocity compared to heading and airspeed. On my Butterfly, in steady state conditions the inertial wind compares with the traditionally derived schemes as seen on PDA, Cambridge, etc. However the Butterfly reports momentary abrupt changes in wind in and around thermals, and sometimes during glides, that these traditional methods miss entirely. Based on other available data, I believe the Butterfly is correct.
>
> >
>
> >
>
> >
>
> > If you fly with iGlide, Butterfly uses the rapid instantaneous wind changes in thermals for their thermalling assistant, which presents a wind direction arrow in each lift dot each second. At least in well organized thermals, the instantaneous wind reliably points towards the center of lift, and can be used to center.
>
> >
>
> >
>
> >
>
> > At other times (notably on final glides over the Carson valley heading back to Truckee) there will be a sudden increase in wind that lasts for many minutes (or perhaps an altitude band, or geographic location) before reverting the the prevailing wind. For example it will go from 8 knots southwest to 28 knots south for 5 minutes, then back - as reported by the Butterfly.. This can be confirmed by comparing GPS to TAS. After some time, the traditional methods will agree. When the strong wind is cross, the traditional method may never show it, while the Butterfly does.
>
> >
>
> >
>
> >
>
> > My conclusion is that in steady state, and particularly for headwind/tailwind components, averaged over some time, the traditional and inertial methods agree well. But the traditional methods miss a lot of rapid changes and there are times when this is significant.
>
> >
>
> >
>
> >
>
> > One problem with observing every change in wind is that if final glide calculations are based on them, you see it varying rapidly as wind gradients are encountered. As far as I know, the Butterfly itself has no way to set the averaging filters differently for final glide calcs, which would be desirable.
>
> >
>
> >
>
> >
>
> > A curiosity (but proof of Butterfly's method) is that while the engine in my ASH26e is running, traditional wind calculation is off by a huge amount since the tail pneumatics are in the prop wash. However the Butterfly correctly calculates the wind during engine runs.
>
>
>
> I usually fly with my wind filter in the Butterfly at 20 sec. I agree with you for the traditional and inertial for final glide. Also the V7 uses some inertial assist. I have it set to 4 of 4 . I also have the butterfly set to 50% for vertical airmass filter Inerital vs TE.
>
> If you want to set the wind filter at l or 2 sec you can see rapid wind changes with the butterfly but I am more concerned with the final glide winds.
>
>
>
> I don't see a way to change the butterfly filter just for final glide. That is a question for Marc at Butterfly.
>
>
>
> Richard
>
> www.craggyaero.com

Richard,
Ok that explains why I am seeing something different. I have the wind filter set to 2 seconds. I find it very interesting to see just how dynamic the wind can be.

Some PDA software seems to have the ability to use a different wind source for final glide. I will put the feature request in to Marc for iGlide.

The S80 suggests that the inertial assist for the vario has only a small influence. I have the vertical air mass filter on the Butterfly set to 80% inertial. 100% seems to make it very twitchy. At 80% I seem to be able to see the difference between actual air mass movement and glider inefficiency. At least for the price of the Butterfly I have convinced myself I can!

[Richard[_9_]]

On Thursday, October 9, 2014 11:28:16 AM UTC-7, jfitch wrote:
> On Thursday, October 9, 2014 10:55:48 AM UTC-7, Richard wrote:
>
> > On Thursday, October 9, 2014 9:36:20 AM UTC-7, jfitch wrote:
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> >
>
> > > On Thursday, October 9, 2014 7:31:08 AM UTC-7, Richard wrote:
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> >
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> > >
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> >
>
> > > > On Wednesday, October 8, 2014 7:47:11 PM UTC-7, wrote:
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> > > >
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> > > > > On Wednesday, October 8, 2014 9:24:51 PM UTC-4, wrote:
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> > > > > > There has been soooooooo much time from the initial announcement of the S80 and the now just released manual that they may have changed the design perameters of the unit.
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> > > > > > I want to hear from LX how the winds are computed.
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> > > > > Reading through the manual, there is no mention of wind at all. Also no mention of being able to connect a compass module, which is referenced on their S80 page in the second to last line of the paragraph directly below the picture of the unit. It states: "fast wind calculation with external compass"
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> > > > > http://www.lxnav.com/products/lxnav-varios/s80.html
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> > > > > The same web page mentions under "Hardware": integrated synthesized speech output. Yet in the manual, it states on page 45 under "stall speed", that the voice module is _not_ integrated in the S80. Confusing.
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> > > > > Interesting feature is ability to set the battery chemistry and battery warnings.
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> > > > I heard from LXNAV
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> > > > Compass can be connected via can bus. In the moment compass is not available.
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> > > > Maybe some sounds are not implemented , but will be in future releases.
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> > > > Concerning Winds: I have both the PowerFlarm-V7-Ultimate Le system and the Butterfly Vario in my glider. I do not see a significant difference in the wind calculation between the systems. Approx 400 hours of flying comparing the systems.
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> > > > Richard
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> > > > www.craggyaero.com
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> > > Richard, how do the winds compare in instantaneous changes? Also what to you have the wind filter set to?
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> > > I don't have a V7 (never seen one) but it appears to calculate winds by the traditional schemes: either thermal drift or GPS track velocity compared to heading and airspeed. On my Butterfly, in steady state conditions the inertial wind compares with the traditionally derived schemes as seen on PDA, Cambridge, etc. However the Butterfly reports momentary abrupt changes in wind in and around thermals, and sometimes during glides, that these traditional methods miss entirely. Based on other available data, I believe the Butterfly is correct.
>
> >
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> > > If you fly with iGlide, Butterfly uses the rapid instantaneous wind changes in thermals for their thermalling assistant, which presents a wind direction arrow in each lift dot each second. At least in well organized thermals, the instantaneous wind reliably points towards the center of lift, and can be used to center.
>
> >
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> > > At other times (notably on final glides over the Carson valley heading back to Truckee) there will be a sudden increase in wind that lasts for many minutes (or perhaps an altitude band, or geographic location) before reverting the the prevailing wind. For example it will go from 8 knots southwest to 28 knots south for 5 minutes, then back - as reported by the Butterfly. This can be confirmed by comparing GPS to TAS. After some time, the traditional methods will agree. When the strong wind is cross, the traditional method may never show it, while the Butterfly does.
>
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> > > My conclusion is that in steady state, and particularly for headwind/tailwind components, averaged over some time, the traditional and inertial methods agree well. But the traditional methods miss a lot of rapid changes and there are times when this is significant.
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> > > One problem with observing every change in wind is that if final glide calculations are based on them, you see it varying rapidly as wind gradients are encountered. As far as I know, the Butterfly itself has no way to set the averaging filters differently for final glide calcs, which would be desirable.
>
> >
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> > >
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>
> > > A curiosity (but proof of Butterfly's method) is that while the engine in my ASH26e is running, traditional wind calculation is off by a huge amount since the tail pneumatics are in the prop wash. However the Butterfly correctly calculates the wind during engine runs.
>
> >
>
> >
>
> >
>
> > I usually fly with my wind filter in the Butterfly at 20 sec. I agree with you for the traditional and inertial for final glide. Also the V7 uses some inertial assist. I have it set to 4 of 4 . I also have the butterfly set to 50% for vertical airmass filter Inerital vs TE.
>
> >
>
> > If you want to set the wind filter at l or 2 sec you can see rapid wind changes with the butterfly but I am more concerned with the final glide winds.
>
> >
>
> >
>
> >
>
> > I don't see a way to change the butterfly filter just for final glide. That is a question for Marc at Butterfly.
>
> >
>
> >
>
> >
>
> > Richard
>
> >
>
> > www.craggyaero.com
>
>
>
> Richard,
>
> Ok that explains why I am seeing something different. I have the wind filter set to 2 seconds. I find it very interesting to see just how dynamic the wind can be.
>
>
>
> Some PDA software seems to have the ability to use a different wind source for final glide. I will put the feature request in to Marc for iGlide.
>
>
>
> The S80 suggests that the inertial assist for the vario has only a small influence. I have the vertical air mass filter on the Butterfly set to 80% inertial. 100% seems to make it very twitchy. At 80% I seem to be able to see the difference between actual air mass movement and glider inefficiency. At least for the price of the Butterfly I have convinced myself I can!

S80s are on the way.

I should have in stock on Monday.

Richard
www.craggyaero.com

[[email protected]]

On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
> Excellent questions and observations.
>
> I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.

You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.

[[email protected]]

Now that was a very sensitive, insightful, and constructive comment for this thread. Thank you.

[krasw]

On Thursday, 9 October 2014 04:18:53 UTC+3, jfitch wrote:
> On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
>
> > What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>
> >
>
> >
>
> >
>
> > The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.
>
>
>
> There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).
>
>
>
> It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.

I really can't think any scenario where I would not absolutely wan't to see variometer info and Flamr radar at same time, on separate displays. Main job of the variometer is to tell you what the glider and airmass are doing vertically. That seems to be very diffult thing to do. Flarm radar display is best shown on big moving map, with additional LED display on top of your panel.

[jfitch]

On Tuesday, October 21, 2014 5:33:24 AM UTC-7, krasw wrote:
> On Thursday, 9 October 2014 04:18:53 UTC+3, jfitch wrote:
>
> > On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
>
> >
>
> > > What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.
>
> >
>
> >
>
> >
>
> > There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).
>
> >
>
> >
>
> >
>
> > It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.
>
>
>
> I really can't think any scenario where I would not absolutely wan't to see variometer info and Flamr radar at same time, on separate displays. Main job of the variometer is to tell you what the glider and airmass are doing vertically. That seems to be very diffult thing to do. Flarm radar display is best shown on big moving map, with additional LED display on top of your panel.

Why separate displays? On the Butterfly, all the vario information is always shown, regardless of whatever screen you are looking at - traffic, AHRS included.

[jfitch]

On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
> On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
>
> > Excellent questions and observations.
>
> >
>
> > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
>
>
>
> You have a built in filter that can eliminate false readings due to gusts.. It's called your backside. If you can't feel the acceleration, it's not there.

Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.

[[email protected]]

Thank you for such a clear explanation for why vario manufacturers are working so hard on these issues. It also makes me feel better about getting fooled by "my backside" and my vario when flying cross-country.

[krasw]

On Tuesday, 21 October 2014 17:59:01 UTC+3, jfitch wrote:
> On Tuesday, October 21, 2014 5:33:24 AM UTC-7, krasw wrote:
>
> > On Thursday, 9 October 2014 04:18:53 UTC+3, jfitch wrote:
>
> >
>
> > > On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
>
> >
>
> > >
>
> >
>
> > > > What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.
>
> >
>
> >
>
> >
>
> > I really can't think any scenario where I would not absolutely wan't to see variometer info and Flamr radar at same time, on separate displays. Main job of the variometer is to tell you what the glider and airmass are doing vertically. That seems to be very diffult thing to do. Flarm radar display is best shown on big moving map, with additional LED display on top of your panel.
>
>
>
> Why separate displays? On the Butterfly, all the vario information is always shown, regardless of whatever screen you are looking at - traffic, AHRS included.

Hardly, as variometer display is only narrow tape on side of display. Not very practical in real life.

Why do we have separate instruments at all? Because it is most effective way to display data to pilot. Nowadays everyone seems to be doing only lists of different features on different instruments, with very little thought into what is important, and how does the most essential parts of instruments work (like variometer, on variometer, trivial as it sounds). And how unimportant data only makes things more confusing.

This image makes my point to perfection:

http://lxnav.com/downloads/images/S80/S80_front.png

No imagine flying under cloudstreet in gaggle at 200 kph and read some info from that screen...

[jfitch]

On Tuesday, October 21, 2014 11:18:58 AM UTC-7, krasw wrote:
> On Tuesday, 21 October 2014 17:59:01 UTC+3, jfitch wrote:
>
> > On Tuesday, October 21, 2014 5:33:24 AM UTC-7, krasw wrote:
>
> >
>
> > > On Thursday, 9 October 2014 04:18:53 UTC+3, jfitch wrote:
>
> >
>
> > >
>
> >
>
> > > > On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
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> > >
>
> >
>
> > > >
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> >
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> > >
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> >
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> >
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> >
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> > >
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> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > I really can't think any scenario where I would not absolutely wan't to see variometer info and Flamr radar at same time, on separate displays. Main job of the variometer is to tell you what the glider and airmass are doing vertically. That seems to be very diffult thing to do. Flarm radar display is best shown on big moving map, with additional LED display on top of your panel.
>
> >
>
> >
>
> >
>
> > Why separate displays? On the Butterfly, all the vario information is always shown, regardless of whatever screen you are looking at - traffic, AHRS included.
>
>
>
> Hardly, as variometer display is only narrow tape on side of display. Not very practical in real life.
>
>
>
> Why do we have separate instruments at all? Because it is most effective way to display data to pilot. Nowadays everyone seems to be doing only lists of different features on different instruments, with very little thought into what is important, and how does the most essential parts of instruments work (like variometer, on variometer, trivial as it sounds). And how unimportant data only makes things more confusing.
>
>
>
> This image makes my point to perfection:
>
>
>
> http://lxnav.com/downloads/images/S80/S80_front.png
>
>
>
> No imagine flying under cloudstreet in gaggle at 200 kph and read some info from that screen...

Actually I find the "narrow tape" on the side of the Butterfly display perfectly adequate, especially in those situations where for example an imminent collision is warned of.

In fact, current thinking in man-machine interface very much favors a single display, with those things requiring the most human attention most prominently displayed automatically. In fighter aircraft, commercial aircraft, F1 cars, etc., the trend is towards a single display glass cockpit.

There is no doubt that this can be poorly done, as your S80 example illustrates. I have no idea what that display is supposed to tell me. But one bad example does not condemn the method.

[krasw]

On Tuesday, 21 October 2014 21:31:48 UTC+3, jfitch wrote:
> On Tuesday, October 21, 2014 11:18:58 AM UTC-7, krasw wrote:
>
> > On Tuesday, 21 October 2014 17:59:01 UTC+3, jfitch wrote:
>
> >
>
> > > On Tuesday, October 21, 2014 5:33:24 AM UTC-7, krasw wrote:
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> > > > On Thursday, 9 October 2014 04:18:53 UTC+3, jfitch wrote:
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> > > > > On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
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> > > > > > What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
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> > > > > > The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.
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> > > > > There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).
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> > > > > It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.
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> > > > I really can't think any scenario where I would not absolutely wan't to see variometer info and Flamr radar at same time, on separate displays.. Main job of the variometer is to tell you what the glider and airmass are doing vertically. That seems to be very diffult thing to do. Flarm radar display is best shown on big moving map, with additional LED display on top of your panel.
>
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> > > Why separate displays? On the Butterfly, all the vario information is always shown, regardless of whatever screen you are looking at - traffic, AHRS included.
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> > Hardly, as variometer display is only narrow tape on side of display. Not very practical in real life.
>
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> > Why do we have separate instruments at all? Because it is most effective way to display data to pilot. Nowadays everyone seems to be doing only lists of different features on different instruments, with very little thought into what is important, and how does the most essential parts of instruments work (like variometer, on variometer, trivial as it sounds). And how unimportant data only makes things more confusing.
>
> >
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> > This image makes my point to perfection:
>
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> > http://lxnav.com/downloads/images/S80/S80_front.png
>
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>
> > No imagine flying under cloudstreet in gaggle at 200 kph and read some info from that screen...
>
>
>
> Actually I find the "narrow tape" on the side of the Butterfly display perfectly adequate, especially in those situations where for example an imminent collision is warned of.
>
>
>
> In fact, current thinking in man-machine interface very much favors a single display, with those things requiring the most human attention most prominently displayed automatically. In fighter aircraft, commercial aircraft, F1 cars, etc., the trend is towards a single display glass cockpit.
>

In commercial airliners the trends is to display only information that is essential and should be displayed. If you look at the screens of modern airbus etc. (screen area is probably hundredfold compared to BF Vario BTW), they are not that confusing at all.

[[email protected]]

On Tuesday, October 21, 2014 11:03:48 AM UTC-4, jfitch wrote:
> On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
>
> > On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
>
> >
>
> > > Excellent questions and observations.
>
> >
>
> > >
>
> >
>
> > > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
>
> >
>
> >
>
> >
>
> > You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.
>
>
>
> Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.

I do not agree. The scream on the vario not associated with the seat feel "true" lift is obvious when you practice enough. All these instruments are trying to do is make the vario agree with what we should feel in the seat.
This could help the less experienced or less active pilot but likely will have little benefit to the pilot that flies a lot.
UH

[jfitch]

On Tuesday, October 21, 2014 12:59:31 PM UTC-7, wrote:
> On Tuesday, October 21, 2014 11:03:48 AM UTC-4, jfitch wrote:
>
> > On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
>
> >
>
> > > On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
>
> >
>
> > >
>
> >
>
> > > > Excellent questions and observations.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.
>
> >
>
> >
>
> >
>
> > Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.
>
>
>
> I do not agree. The scream on the vario not associated with the seat feel "true" lift is obvious when you practice enough. All these instruments are trying to do is make the vario agree with what we should feel in the seat.
>
> This could help the less experienced or less active pilot but likely will have little benefit to the pilot that flies a lot.
>
> UH

Do not agree with what?

The aerodynamics is accepted by pretty much everyone. The seat of the pants feel is simply vertical acceleration (and sometimes a little lateral mixed in). This could be displayed on a very inexpensive accelerometer. If what you say is true, then you don't need a variometer at all. I hope the vario manufacturers are trying to do more (and they are). Specifically, concisely present information allowing maximum extraction of energy from the surrounding air. There are many reasons why a barometric variometer does not (and cannot) duplicate the accelerations you feel.

[Dan Marotta]

Off topic but, if the screens in the Airbus display only necessary data,
then why wasn't the simple message: "LOWER THE FREAKING NOSE" displayed
to that crew over the Atlantic?

Dan Marotta

On 10/21/2014 1:57 PM, krasw wrote:
> On Tuesday, 21 October 2014 21:31:48 UTC+3, jfitch wrote:
>> On Tuesday, October 21, 2014 11:18:58 AM UTC-7, krasw wrote:
>>
>>> On Tuesday, 21 October 2014 17:59:01 UTC+3, jfitch wrote:
>>>> On Tuesday, October 21, 2014 5:33:24 AM UTC-7, krasw wrote:
>>>>> On Thursday, 9 October 2014 04:18:53 UTC+3, jfitch wrote:
>>>>>> On Wednesday, October 8, 2014 3:30:33 PM UTC-7, wrote:
>>>>>>> What are the differences in the inertial nagivation systems between the Butterfly vario and the S80?
>>>>>>> The LX literature was confusing on how wind calculations are made and it says in one place that the S80 makes continuous wind calculations on its own but in another place it says that the S80 requires the compass module to improve wind calculations.
>>>>>> There is no information in the manual about inertial vertical air mass movement nor inertially derived wind - the two most impressive things about the Butterfly (Air).
>>>>>> It looks like it does have a very nice Flarm display and flarm warnings - the two least impressive things about the Butterfly.
>>>>> I really can't think any scenario where I would not absolutely wan't to see variometer info and Flamr radar at same time, on separate displays. Main job of the variometer is to tell you what the glider and airmass are doing vertically. That seems to be very diffult thing to do. Flarm radar display is best shown on big moving map, with additional LED display on top of your panel.
>>>> Why separate displays? On the Butterfly, all the vario information is always shown, regardless of whatever screen you are looking at - traffic, AHRS included.
>>> Hardly, as variometer display is only narrow tape on side of display. Not very practical in real life.
>>> Why do we have separate instruments at all? Because it is most effective way to display data to pilot. Nowadays everyone seems to be doing only lists of different features on different instruments, with very little thought into what is important, and how does the most essential parts of instruments work (like variometer, on variometer, trivial as it sounds). And how unimportant data only makes things more confusing.
>>> This image makes my point to perfection:
>>> http://lxnav.com/downloads/images/S80/S80_front.png
>>> No imagine flying under cloudstreet in gaggle at 200 kph and read some info from that screen...
>>
>>
>> Actually I find the "narrow tape" on the side of the Butterfly display perfectly adequate, especially in those situations where for example an imminent collision is warned of.
>>
>>
>>
>> In fact, current thinking in man-machine interface very much favors a single display, with those things requiring the most human attention most prominently displayed automatically. In fighter aircraft, commercial aircraft, F1 cars, etc., the trend is towards a single display glass cockpit.
>>
> In commercial airliners the trends is to display only information that is essential and should be displayed. If you look at the screens of modern airbus etc. (screen area is probably hundredfold compared to BF Vario BTW), they are not that confusing at all.

[jfitch]

On Tuesday, October 21, 2014 4:23:53 PM UTC-7, Dan Marotta wrote:
> Off topic but, if the screens in the
> Airbus display only necessary data, then why wasn't the simple
> message: "LOWER THE FREAKING NOSE" displayed to that crew over the
> Atlantic?
>
>

That wasn't considered necessary information for trained pilots.....

[[email protected]]

On Tuesday, October 21, 2014 2:21:38 PM UTC-7, jfitch wrote:
> On Tuesday, October 21, 2014 12:59:31 PM UTC-7, wrote:
>
> > On Tuesday, October 21, 2014 11:03:48 AM UTC-4, jfitch wrote:
>
> >
>
> > > On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
>
> >
>
> > >
>
> >
>
> > > > On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > Excellent questions and observations.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.
>
> >
>
> >
>
> >
>
> > I do not agree. The scream on the vario not associated with the seat feel "true" lift is obvious when you practice enough. All these instruments are trying to do is make the vario agree with what we should feel in the seat.

[Jim White[_3_]]

At 23:23 21 October 2014, Dan Marotta wrote:
>Off topic but, if the screens in the Airbus display only necessary data,
>then why wasn't the simple message: "LOWER THE FREAKING NOSE" displayed
>to that crew over the Atlantic?
>
>Dan Marotta
>
Airbus know better, and consider that their airplane's computers are better
at flying than the pilots. The pilots are there simply to satisfy the
regulators and the public. From this position why would you need to tell
the pilot anything at all?

[[email protected]]

On Wednesday, October 22, 2014 7:31:30 AM UTC-4, wrote:
> On Tuesday, October 21, 2014 2:21:38 PM UTC-7, jfitch wrote:
>
> > On Tuesday, October 21, 2014 12:59:31 PM UTC-7, wrote:
>
> >
>
> > > On Tuesday, October 21, 2014 11:03:48 AM UTC-4, jfitch wrote:
>
> >
>
> > >
>
> >
>
> > > > On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > > Excellent questions and observations.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > > You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > I do not agree. The scream on the vario not associated with the seat feel "true" lift is obvious when you practice enough. All these instruments are trying to do is make the vario agree with what we should feel in the seat.
>
> >
>
> > >
>
> >
>
> > > This could help the less experienced or less active pilot but likely will have little benefit to the pilot that flies a lot.
>
> >
>
> > >
>
> >
>
> > > UH
>
> >
>
> >
>
> >
>
> > Do not agree with what?
>
> >
>
> >
>
> >
>
> > The aerodynamics is accepted by pretty much everyone. The seat of the pants feel is simply vertical acceleration (and sometimes a little lateral mixed in). This could be displayed on a very inexpensive accelerometer. If what you say is true, then you don't need a variometer at all. I hope the vario manufacturers are trying to do more (and they are). Specifically, concisely present information allowing maximum extraction of energy from the surrounding air. There are many reasons why a barometric variometer does not (and cannot) duplicate the accelerations you feel.
>
>
>
> Hmmm...
>
>
>
> There seems to be some confusion here.
>
>
>
> Humans can, with varying precision, detect linear and angular acceleration and at least the first derivative thereof (the physics term is "jerk"). Humans are relatively poor at judging vertical position (altitude) and velocity (climb rate) with enough precision to be useful in soaring most of the time.
>
>
>
> The flight dynamics that result from changes in vertical versus horizontal air movement, while somewhat similar, are not identical. Experienced pilots generally can pick up the difference much of the time, but I think it is quite possible to use a combination of air data and acceleration information to compensate a vario so that its transient response to horizontal gusts reinforces, rather than conflicts with, the seat of the pants sensation and judgement of experienced pilots. I think this would be of benefit to all experience levels, but obviously of greater benefit to pilots who aren't practiced in the art of sorting the difference.
>
>
>
> 9B

9B said what I was trying to communicate better than I did.
UH

[Dan Marotta]

I would argue that they weren't "trained pilots". They were systems
managers and, when the systems performed as programmed, rather than in a
manner which the pilots expected, the pilots didn't have the wherewithal
to fly the aircraft out of a simple stall.

Dan Marotta

On 10/22/2014 12:01 AM, jfitch wrote:
> On Tuesday, October 21, 2014 4:23:53 PM UTC-7, Dan Marotta wrote:
>> Off topic but, if the screens in the
>> Airbus display only necessary data, then why wasn't the simple
>> message: "LOWER THE FREAKING NOSE" displayed to that crew over the
>> Atlantic?
>>
>>
> That wasn't considered necessary information for trained pilots.....

[krasw]

Sorry for on-topic intervention, but is the variometer technology (hardware) identical in V7, V9 and S80? Or in other words, is there any evidence to think it is not identical?

[Richard[_9_]]

On Thursday, October 23, 2014 12:15:57 AM UTC-7, krasw wrote:
> Sorry for on-topic intervention, but is the variometer technology (hardware) identical in V7, V9 and S80? Or in other words, is there any evidence to think it is not identical?

Hardware is similar but the V9 S80 has inertial sensors.
Chart explains

http://www.lxnav.com/products/lxnav-varios.html

Richard
www.craggyaero.com

[krasw]

On Thursday, 23 October 2014 16:11:45 UTC+3, Richard wrote:
> On Thursday, October 23, 2014 12:15:57 AM UTC-7, krasw wrote:
> > Sorry for on-topic intervention, but is the variometer technology (hardware) identical in V7, V9 and S80? Or in other words, is there any evidence to think it is not identical?
>
> Hardware is similar but the V9 S80 has inertial sensors.
> Chart explains
>
> http://www.lxnav.com/products/lxnav-varios.html
>
> Richard
> www.craggyaero.com

What do they use inertial sensors for, besides horizon?

[Richard[_9_]]

On Thursday, October 23, 2014 7:04:52 AM UTC-7, krasw wrote:
> On Thursday, 23 October 2014 16:11:45 UTC+3, Richard wrote:
> > On Thursday, October 23, 2014 12:15:57 AM UTC-7, krasw wrote:
> > > Sorry for on-topic intervention, but is the variometer technology (hardware) identical in V7, V9 and S80? Or in other words, is there any evidence to think it is not identical?
> >
> > Hardware is similar but the V9 S80 has inertial sensors.
> > Chart explains
> >
> > http://www.lxnav.com/products/lxnav-varios.html
> >
> > Richard
> > www.craggyaero.com
>
> What do they use inertial sensors for, besides horizon?

5.5.2.13 Inertial assisted vario
With the LXNAV S80, it is possible to adjust the influence of g-force on the vario. This
influence is very small and can be set to Off or between 0 and 4.

Richard
www.craggyaero.com

[krasw]

On Thursday, 23 October 2014 17:51:52 UTC+3, Richard wrote:
> On Thursday, October 23, 2014 7:04:52 AM UTC-7, krasw wrote:
> > On Thursday, 23 October 2014 16:11:45 UTC+3, Richard wrote:
> > > On Thursday, October 23, 2014 12:15:57 AM UTC-7, krasw wrote:
> > > > Sorry for on-topic intervention, but is the variometer technology (hardware) identical in V7, V9 and S80? Or in other words, is there any evidence to think it is not identical?
> > >
> > > Hardware is similar but the V9 S80 has inertial sensors.
> > > Chart explains
> > >
> > > http://www.lxnav.com/products/lxnav-varios.html
> > >
> > > Richard
> > > www.craggyaero.com
> >
> > What do they use inertial sensors for, besides horizon?
>
> 5.5.2.13 Inertial assisted vario
> With the LXNAV S80, it is possible to adjust the influence of g-force on the vario. This
> influence is very small and can be set to Off or between 0 and 4.
>
> Richard
> www.craggyaero.com


G-force indicates there is only acceleration sensor used, that is whole different thing as full inertial setup.

[[email protected]]

There are accelerometers for all three axis.

[krasw]

On Thursday, 23 October 2014 18:43:04 UTC+3, wrote:
> There are accelerometers for all three axis.

Yes, and if you add 3-axis (MEMS) gyros to that, you'll end up with so-called inertial sensors. You can measure acceleration all you want but those sensors alone cannot calculate the direction of acceleration, you need rate gyros for that. And even rate gyros need long-time reference from other sensors, such as 3D-compass + GPS.

[[email protected]]

Thank you.
In my next life I will try to be a physicist.
I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking. I am tired of paying full price to be a beta tester and then get abandoned.

[jfitch]

On Thursday, October 23, 2014 11:11:44 AM UTC-7, wrote:
> Thank you.
> In my next life I will try to be a physicist.
> I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking. I am tired of paying full price to be a beta tester and then get abandoned.

'I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking.'

I am a bit surprised by that statement. It is a European company, not Radio Shack down at the mall, nevertheless, my emailed requests and questions to Butterfly are nearly always answered overnight. In the one instance that I had a serious problem with released firmware, I explained what I saw, and had fixed firmware version within a couple of days.

I don't know what your expectations are, but I doubt you would do much better on this type of product unless the company president was a next door neighbor.

[krasw]

On Thursday, 23 October 2014 21:11:44 UTC+3, wrote:
> Thank you.
> In my next life I will try to be a physicist.
> I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking. I am tired of paying full price to be a beta tester and then get abandoned.

I'm only interested in LX Nav's current state of variometer technology. As a general remark, modern consumer is beta tester in every product that contains software. Sadly.

[Richard[_9_]]

On Thursday, October 23, 2014 11:11:44 AM UTC-7, wrote:
> Thank you.
> In my next life I will try to be a physicist.
> I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking. I am tired of paying full price to be a beta tester and then get abandoned.

And who would these many people be? I have not had that experience.

Richard

[[email protected]]

On Thursday, October 23, 2014 11:11:44 AM UTC-7, wrote:
> Thank you.
> In my next life I will try to be a physicist.
> I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking. I am tired of paying full price to be a beta tester and then get abandoned.

What you call "beta testers" is better described as "early adopters". I am sure Butterfly has a small subset of users that they actually enlist as beta testers.

We are lucky to have people that start companies like that which have the vision and are willing to take a inordinate risk by developing such advanced products - especially for such a small market - in the hope of establishing a sustainable business. They count on the availability of early adopters, without which their venture would most likely not be viable. On the other hand, the early adopters seek to get their hands on the latest technology as soon as possible. It is a symbiotic relationship.

It just happens that some people are just not willing or suitable early adopters. That's fine. Just wait until the product matures then consider it again. If you are expecting a completely finished product from the very first version, it is not going to happen.

Not in every case you pay full price as an early adopter. Many received a very nice discount on a Powerflarm for being one.

David

[John Carlyle]

On Thursday, October 23, 2014 6:24:29 PM UTC-4, wrote:
> On Thursday, October 23, 2014 11:11:44 AM UTC-7, wrote:
> > Thank you.
> > In my next life I will try to be a physicist.
> > I am greatly attracted to the technology in the Butterfly Vario but in asking many people about their experiences, customer service and support is lacking. I am tired of paying full price to be a beta tester and then get abandoned.
>
> What you call "beta testers" is better described as "early adopters". I am sure Butterfly has a small subset of users that they actually enlist as beta testers.
>
> We are lucky to have people that start companies like that which have the vision and are willing to take a inordinate risk by developing such advanced products - especially for such a small market - in the hope of establishing a sustainable business. They count on the availability of early adopters, without which their venture would most likely not be viable. On the other hand, the early adopters seek to get their hands on the latest technology as soon as possible. It is a symbiotic relationship.
>
> It just happens that some people are just not willing or suitable early adopters. That's fine. Just wait until the product matures then consider it again. If you are expecting a completely finished product from the very first version, it is not going to happen.
>
> Not in every case you pay full price as an early adopter. Many received a very nice discount on a Powerflarm for being one.
>
> David

I second what David said, and I also agree with Jon and Richard. I have a Butterfly Vario, and I love it. There are hiccups, sure, but I've got hiccups with my iPhone 6, too. Just like Apple has done, Butterfly has responded swiftly to fix them. Sounds to me like you're a perfectionist that wouldn't be satisfied with any piece of equipment, up to and including your glider.

-John, Q3

[[email protected]]

On Wednesday, October 22, 2014 2:03:48 AM UTC+11, jfitch wrote:
> On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
> > On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
> >
> > > Excellent questions and observations.
> >
> > >
> >
> > > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
> >
> >
> >
> > You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.
>
> Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.

A horizontal gust does NOT produce acceleration. That's why you can't feel it. If you cannot sense vertical acceleration it's not there, despite what your instruments are telling you.
To put it another way: if your vario is telling you that you are accelerating upwards at 5 knots (500 fpm or over 8 feet per second) and you cannot feel it, then you can ignore it as a gust. Why look for a complex technological solution to something so simple?
A vertical gust is a different matter. I presume by vertical gust you are referring to a vertical movement of air. What distinguishes a vertical gust from lift?

[Mike the Strike]

The issue with horizontal gusts is that if you fly into a thermal outflow (quite common where they are strong and dry), it temporarily increases your airspeed. The TE probe outputs a signal that interprets this increase in aircraft energy as lift. There is no acceleration, just an increase in energy. The seat of your pants may well be able to sense the lack of acceleration in this circumstance, but sensitive accelerometers will be even better.

Mike

[jfitch]

On Tuesday, October 28, 2014 4:39:56 PM UTC-7, wrote:
> On Wednesday, October 22, 2014 2:03:48 AM UTC+11, jfitch wrote:
> > On Monday, October 20, 2014 4:24:46 PM UTC-7, wrote:
> > > On Friday, October 10, 2014 3:50:54 AM UTC+11, wrote:
> > >
> > > > Excellent questions and observations.
> > >
> > > >
> > >
> > > > I am focused on the S80 and Butterfly primarily because they have an artificial horizon but also would like a unit that can filter out horizontal gusts that cause me/us to think we have entered a strong thermal. It also would seem that the instantaneous wind readings would be very helpful when flying convergence lines.
> > >
> > >
> > >
> > > You have a built in filter that can eliminate false readings due to gusts. It's called your backside. If you can't feel the acceleration, it's not there.
> >
> > Acceleration due to a a vertical or horizontal gust are not discernible by the human backside. Both result in an increase in lift: the former due to an increase in the angle of attack and the latter due to an increase in air speed. Both can be used to gain energy, but you will find circling in the latter a pointless exercise. Which is why every variometer manufacturer is trying to differentiate them.
>
> A horizontal gust does NOT produce acceleration. That's why you can't feel it. If you cannot sense vertical acceleration it's not there, despite what your instruments are telling you.
> To put it another way: if your vario is telling you that you are accelerating upwards at 5 knots (500 fpm or over 8 feet per second) and you cannot feel it, then you can ignore it as a gust. Why look for a complex technological solution to something so simple?
> A vertical gust is a different matter. I presume by vertical gust you are referring to a vertical movement of air. What distinguishes a vertical gust from lift?

A horizontal gust most certainly does produce acceleration, at least on this planet. It will cause a horizontal acceleration due to direct drag on the airframe, and a vertical acceleration due to an increase in lift. To refresh your memory, lift = dynamic press x coefficient of lift x wing area. The instantaneous coefficient of lift does not change at a horizontal gust (nor obviously does wing area) but dynamic pressure increases as the square of the velocity. If the gust is from ahead and say 10 knots flying at 50, you have a sudden increase in lift of 44%, therefore you will feel 1.44 Gs upward acceleration momentarily.

A vertical gust is what we call lift, though it can be quite transient, then we call it turbulence. A vertical gust increases airspeed slightly, but increases angle of attack and therefore coefficient of lift markedly. That causes vertical acceleration due to increased lift, and horizontal acceleration due to an increase in induced drag. A 10 knot vertical gust encountered at 50 knots will only give you about 1.2 Gs though, since lift/angle of attack is approximately linear.

Your variometer might also be confused in various ways (lag, TE comp, acceleration effects) but the accelerations described above are very real. In gusty conditions (or better still a high wind shear gradient) it is possible to extract energy from horizontal gusts, sufficient to soar. It has been done in full size sailplanes and is routinely done in RC gliders.

[[email protected]]

On Wednesday, October 29, 2014 11:07:05 AM UTC+11, Mike the Strike wrote:
> The issue with horizontal gusts is that if you fly into a thermal outflow (quite common where they are strong and dry), it temporarily increases your airspeed. The TE probe outputs a signal that interprets this increase in aircraft energy as lift. There is no acceleration, just an increase in energy. The seat of your pants may well be able to sense the lack of acceleration in this circumstance, but sensitive accelerometers will be even better.

[jfitch]

On Tuesday, October 28, 2014 5:07:05 PM UTC-7, Mike the Strike wrote:
> The issue with horizontal gusts is that if you fly into a thermal outflow (quite common where they are strong and dry), it temporarily increases your airspeed. The TE probe outputs a signal that interprets this increase in aircraft energy as lift. There is no acceleration, just an increase in energy. The seat of your pants may well be able to sense the lack of acceleration in this circumstance, but sensitive accelerometers will be even better.

[jfitch]

On Tuesday, October 28, 2014 5:22:42 PM UTC-7, wrote:
> On Wednesday, October 29, 2014 11:07:05 AM UTC+11, Mike the Strike wrote:
> > The issue with horizontal gusts is that if you fly into a thermal outflow (quite common where they are strong and dry), it temporarily increases your airspeed. The TE probe outputs a signal that interprets this increase in aircraft energy as lift. There is no acceleration, just an increase in energy. The seat of your pants may well be able to sense the lack of acceleration in this circumstance, but sensitive accelerometers will be even better.
> >
> > Mike
>
> I know what a horizontal gust is, and what causes it,and I am aware that it results in a false reading of lift on the vario.
> You are missing my point entirely. Despite what the vario is indicating, if you cannot feel a vertical acceleration, then it is simply not there, and you can ignore the vario. No need for a complex algoriths or hardware. You already have a sensitive accelerometer refined over millions of years: use it.

You are missing my point entirely. A horizontal gust causes actual, real, measurable, and "feelable" vertical acceleration. Ignoring the vario entirely, how can you differentiate it from that acceleration caused by a vertical gust? You cannot without additional information - vertical acceleration is vertical acceleration.

[Andy Blackburn[_3_]]

On Tuesday, October 28, 2014 5:28:19 PM UTC-7, jfitch wrote:
> You are missing my point entirely. A horizontal gust causes actual, real, measurable, and "feelable" vertical acceleration. Ignoring the vario entirely, how can you differentiate it from that acceleration caused by a vertical gust? You cannot without additional information - vertical acceleration is vertical acceleration.

No.

There are transient versus sustained effects that are different for horizontal versus vertical shears (gust versus thermal).

Saying that because a horizontal gust generates lift that it is the same as a thermal that accelerates the glider's frame of reference in a sustained vertical direction is simply incorrect.

9B

[Richard[_9_]]

On Tuesday, October 28, 2014 5:24:58 PM UTC-7, jfitch wrote:
> On Tuesday, October 28, 2014 5:07:05 PM UTC-7, Mike the Strike wrote:
> > The issue with horizontal gusts is that if you fly into a thermal outflow (quite common where they are strong and dry), it temporarily increases your airspeed. The TE probe outputs a signal that interprets this increase in aircraft energy as lift. There is no acceleration, just an increase in energy. The seat of your pants may well be able to sense the lack of acceleration in this circumstance, but sensitive accelerometers will be even better.
> >
> > Mike
>
> The Butterfly vario calculates wind, purely inertially derived from accelerometers, about 20 times a second. If you believe it (and I do mostly, based on independent checks) you learn that the wind it quite dynamic around thermals. 10 or even 15 knot changes in and around western desert thermals are common. This messes with both your backside and your compensated vario. There appear also to be pressure gradients in and around thermals, which confuses things further for barometric based varios.

John,

You can also set the wind filters to a faster number as low as 1 sec. I have mine set a 10 sec.

Richard
www.craggyaero.com

[jfitch]

On Tuesday, October 28, 2014 9:24:00 PM UTC-7, Andy Blackburn wrote:
> On Tuesday, October 28, 2014 5:28:19 PM UTC-7, jfitch wrote:
> > You are missing my point entirely. A horizontal gust causes actual, real, measurable, and "feelable" vertical acceleration. Ignoring the vario entirely, how can you differentiate it from that acceleration caused by a vertical gust? You cannot without additional information - vertical acceleration is vertical acceleration.
>
> No.
>
> There are transient versus sustained effects that are different for horizontal versus vertical shears (gust versus thermal).
>
> Saying that because a horizontal gust generates lift that it is the same as a thermal that accelerates the glider's frame of reference in a sustained vertical direction is simply incorrect.
>
> 9B

Saying that would be simply incorrect - but that is not what I said. A glider is never accelerated in a sustained way. All accelerations the glider experiences are transient, whether induced by a horizontal or vertical gust (excepting turning flight). Once the glider reaches its new velocity, vertical acceleration is zero, regardless of steady state climb rate. This is high school physics. The transient effect is acceleration, this is what you feel. The sustained effect is climb rate, this is what you hope for. But climb rate cannot be felt, only acceleration. When you feel that acceleration, you have about 2 or 3 seconds to determine its cause and react appropriately.

A transient horizontal gust (say ramping quickly from 0 to 10, then back to zero) will be felt as an upward acceleration, followed by a downward acceleration - a bump. But a sustained gust will be felt as an upward acceleration (and an airspeed increase, and a very slight angle of attack reduction, and a lagging variometer up deflection). In nice smooth well behaved air, you might be able to use the more subtle clues to differentiate that from a vertical gust, which will also cause an upward acceleration (and a smaller airspeed increase, a greater angle of attack increase, and perhaps a small momentary lagging downward variometer deflection). In rougher air (mostly what I fly in) sorting this from the noise is practically impossible most of the time. Remembering also that most gusts are neither perfectly vertical nor horizontal, but some random angle in-between.

Of those transient effects, the angle of attack change is probably the easiest to measure, which makes me wonder why this hasn't been pursued more for variometer use. But that signal has a lot of noise in it too.

[Jim White[_3_]]

All very interesting but I would bet that Seb Kawa could beat us all with
just a simple winter vario.

[[email protected]]

On Wednesday, October 29, 2014 11:00:05 AM UTC-7, Jim White wrote:
> All very interesting but I would bet that Seb Kawa could beat us all with
> just a simple winter vario.

He most likely would, and easily. But he still loves his Butterfly vario. Below is a quote from an interview with him, about his observations during the EGC in Vinon. The value of the inertially derived real-time vector wind is just beginning to be understood because it is so new. It sheds light into the microstructure of the airmass. I most definitely will be installing something like this in my next glider.

David

Source: https://www.facebook.com/air.avionics/posts/546343178758534

".. it helped very much and not only in wave. The indication changed very quick and you could get extra information about convergencies, and wave spots in the way it was not possible before. Example - flying near the thermal I was able to notice that the wind was changing towards the thermal. In the thermal wind was still. After such experience I was turning according to the updated wind dirrection and it proved that the lift was in that direction.

[jfitch]

On Wednesday, October 29, 2014 11:23:02 AM UTC-7, wrote:
> On Wednesday, October 29, 2014 11:00:05 AM UTC-7, Jim White wrote:
> > All very interesting but I would bet that Seb Kawa could beat us all with
> > just a simple winter vario.
>
> He most likely would, and easily. But he still loves his Butterfly vario. Below is a quote from an interview with him, about his observations during the EGC in Vinon. The value of the inertially derived real-time vector wind is just beginning to be understood because it is so new. It sheds light into the microstructure of the airmass. I most definitely will be installing something like this in my next glider.
>
> David
>
> Source: https://www.facebook.com/air.avionics/posts/546343178758534
>
> ".. it helped very much and not only in wave. The indication changed very quick and you could get extra information about convergencies, and wave spots in the way it was not possible before. Example - flying near the thermal I was able to notice that the wind was changing towards the thermal. In the thermal wind was still. After such experience I was turning according to the updated wind dirrection and it proved that the lift was in that direction.
> I could see the sudden wind change when passing Col de Var - it has changed rapidly to 45km/h , so I new in few seconds where to look for the hill lifts.
> Following big convergence line I used the wind indication, taking into account that wind was blowing towards the lift line.
> In the wave - we had weak wave. In the day when it was strong, my class did not fly. But - it is easy to see that wind is slowing down in lift area..."

In fact if you use iGlide, the thermal assistant makes use of this fact: each second a lift dot is placed on your track. In each lift dot there is a wind vector. In well organized thermals all of the wind vectors all around the circle point towards the center. In less well organized thermals it isn't as clear, but still you can draw some conclusions. The lift is most likely strongest where the wind is still, and vectors pointing towards the still area give you an idea of where to correct to.

The wind is surprisingly dynamic around thermals, at least as reported by the Butterfly. It is quite common (as Kawa says) to have the wind deflected towards the thermal, and still inside the thermal. Think what that means when flying directly through a thermal core: first there is an increasing tailwind component which will feel like a downward acceleration. As you enter the core the tailwind decreases to zero, then becomes a headwind as you exit the other side. To the glider, that all looks like a horizontal gust from ahead (in addition to whatever the vertical component is), with the associated accelerations and other changes. I believe that is one of the reasons that lift very often seems softer, once centered, than you thought you experienced on your first pass through. Part of it is a phantom of the wind gradient.

This last season I started using this: you enter what you think is lift but there is no clear indication of which way to turn. Looking at the instantaneous wind, turn towards it (or more properly towards its deviation). More often than not, that is the correct direction.

[Andy Blackburn[_3_]]

On Wednesday, October 29, 2014 9:51:00 AM UTC-7, jfitch wrote:
> On Tuesday, October 28, 2014 9:24:00 PM UTC-7, Andy Blackburn wrote:
> > On Tuesday, October 28, 2014 5:28:19 PM UTC-7, jfitch wrote:
> > > You are missing my point entirely. A horizontal gust causes actual, real, measurable, and "feelable" vertical acceleration. Ignoring the vario entirely, how can you differentiate it from that acceleration caused by a vertical gust? You cannot without additional information - vertical acceleration is vertical acceleration.
> >
> > No.
> >
> > There are transient versus sustained effects that are different for horizontal versus vertical shears (gust versus thermal).
> >
> > Saying that because a horizontal gust generates lift that it is the same as a thermal that accelerates the glider's frame of reference in a sustained vertical direction is simply incorrect.
> >
> > 9B
>
> Saying that would be simply incorrect - but that is not what I said. A glider is never accelerated in a sustained way. All accelerations the glider experiences are transient, whether induced by a horizontal or vertical gust (excepting turning flight). Once the glider reaches its new velocity, vertical acceleration is zero, regardless of steady state climb rate. This is high school physics. The transient effect is acceleration, this is what you feel. The sustained effect is climb rate, this is what you hope for. But climb rate cannot be felt, only acceleration. When you feel that acceleration, you have about 2 or 3 seconds to determine its cause and react appropriately.
>
> A transient horizontal gust (say ramping quickly from 0 to 10, then back to zero) will be felt as an upward acceleration, followed by a downward acceleration - a bump. But a sustained gust will be felt as an upward acceleration (and an airspeed increase, and a very slight angle of attack reduction, and a lagging variometer up deflection). In nice smooth well behaved air, you might be able to use the more subtle clues to differentiate that from a vertical gust, which will also cause an upward acceleration (and a smaller airspeed increase, a greater angle of attack increase, and perhaps a small momentary lagging downward variometer deflection). In rougher air (mostly what I fly in) sorting this from the noise is practically impossible most of the time. Remembering also that most gusts are neither perfectly vertical nor horizontal, but some random angle in-between.
>
> Of those transient effects, the angle of attack change is probably the easiest to measure, which makes me wonder why this hasn't been pursued more for variometer use. But that signal has a lot of noise in it too.

That's closer to my understanding though I would quibble about some of the details of how an aircraft responds to a horizontal gust.

Assume, for illustration, the gust is 10 knots, and follows the classic "one minus cosine" profile over a second or two. You would see a 10 knot increase in airspeed and if you kept the controls fixed it would activate a modest phugoid response but then be reversed on the back side of the gust. Presuming the glider is flying with the c.g. forward of the center of pressure you should get some onset of upward pitch, but not a lot of immediate g-force as the phugoid is generally a much longer time constant that the short period (AOA) mode. You should also experience some deceleration against the direction of flight from the higher form drag and induced drag due to the change in airspeed, though I suspect this would be harder to pick up than the airspeed change.

With a thermal entry the glider is entering an airmass with vertical velocity that is altered. Again presume 10 knots and in this case also assume it has a rapid onset like the horizontal gust (my experience is that most thermals actually build over a longer time period and are more sustained than horizontal gusts from turbulence but lets make it as similar as possible to tease out the pure differences). The glider experiences two things - a direct vertical acceleration as its inertial reference changes from still air to rising air and it starts to go up directly - this happens pretty quickly, but in the transition it also experiences an increase in angle of attack which activates the short-period longitudinal mode. Given the geometry you can imagine that a vertical air movement has much more of an effect on AOA than a horizontal gust of similar velocity so the sort-period response should be much more energetic.

The other difference is that horizontal gusts tend to look like a "one minus cosine" profile (ramp up and back down) whereas thermal ramp up but don't really ramp back down until you fly out of them several seconds later.

Of course vertical gusts that are not associated with thermals look more like thermals in everything except this symmetric versus asymmetric profile so if the big surge you feel isn't reversed immediately it's more likely a thermal.

If you are familiar with concepts of aircraft dynamics and control theory this article is somewhat informative:

http://scialert.net/fulltext/?doi=srj.2008.17.28

I think to have a vario filter out horizontal gusts you would need to have a dynamic model for the glider and both accelerometers and angular rate gyros plus air data. A simple Kalman filter could then solve for airmass movement and generate a three-dimensional airmass vector in real time. You're only really interested in the Z component so you'd discard the other info unless you were curious about decoding what your body was telling you.

Whether this is the approach vario designers are taking, whether the varios have the sensors to measure all the linear and angular rates and accelerations and whether the effects are pronounced enough to measure clearly amidst all the noise, control inputs and measurement errors and lags I couldn't really say.

9B

[jfitch]

On Wednesday, October 29, 2014 12:59:01 PM UTC-7, Andy Blackburn wrote:
> On Wednesday, October 29, 2014 9:51:00 AM UTC-7, jfitch wrote:
> > On Tuesday, October 28, 2014 9:24:00 PM UTC-7, Andy Blackburn wrote:
> > > On Tuesday, October 28, 2014 5:28:19 PM UTC-7, jfitch wrote:
> > > > You are missing my point entirely. A horizontal gust causes actual, real, measurable, and "feelable" vertical acceleration. Ignoring the vario entirely, how can you differentiate it from that acceleration caused by a vertical gust? You cannot without additional information - vertical acceleration is vertical acceleration.
> > >
> > > No.
> > >
> > > There are transient versus sustained effects that are different for horizontal versus vertical shears (gust versus thermal).
> > >
> > > Saying that because a horizontal gust generates lift that it is the same as a thermal that accelerates the glider's frame of reference in a sustained vertical direction is simply incorrect.
> > >
> > > 9B
> >
> > Saying that would be simply incorrect - but that is not what I said. A glider is never accelerated in a sustained way. All accelerations the glider experiences are transient, whether induced by a horizontal or vertical gust (excepting turning flight). Once the glider reaches its new velocity, vertical acceleration is zero, regardless of steady state climb rate. This is high school physics. The transient effect is acceleration, this is what you feel. The sustained effect is climb rate, this is what you hope for. But climb rate cannot be felt, only acceleration. When you feel that acceleration, you have about 2 or 3 seconds to determine its cause and react appropriately.
> >
> > A transient horizontal gust (say ramping quickly from 0 to 10, then back to zero) will be felt as an upward acceleration, followed by a downward acceleration - a bump. But a sustained gust will be felt as an upward acceleration (and an airspeed increase, and a very slight angle of attack reduction, and a lagging variometer up deflection). In nice smooth well behaved air, you might be able to use the more subtle clues to differentiate that from a vertical gust, which will also cause an upward acceleration (and a smaller airspeed increase, a greater angle of attack increase, and perhaps a small momentary lagging downward variometer deflection). In rougher air (mostly what I fly in) sorting this from the noise is practically impossible most of the time. Remembering also that most gusts are neither perfectly vertical nor horizontal, but some random angle in-between.
> >
> > Of those transient effects, the angle of attack change is probably the easiest to measure, which makes me wonder why this hasn't been pursued more for variometer use. But that signal has a lot of noise in it too.
>
> That's closer to my understanding though I would quibble about some of the details of how an aircraft responds to a horizontal gust.
>
> Assume, for illustration, the gust is 10 knots, and follows the classic "one minus cosine" profile over a second or two. You would see a 10 knot increase in airspeed and if you kept the controls fixed it would activate a modest phugoid response but then be reversed on the back side of the gust. Presuming the glider is flying with the c.g. forward of the center of pressure you should get some onset of upward pitch, but not a lot of immediate g-force as the phugoid is generally a much longer time constant that the short period (AOA) mode. You should also experience some deceleration against the direction of flight from the higher form drag and induced drag due to the change in airspeed, though I suspect this would be harder to pick up than the airspeed change.
>
> With a thermal entry the glider is entering an airmass with vertical velocity that is altered. Again presume 10 knots and in this case also assume it has a rapid onset like the horizontal gust (my experience is that most thermals actually build over a longer time period and are more sustained than horizontal gusts from turbulence but lets make it as similar as possible to tease out the pure differences). The glider experiences two things - a direct vertical acceleration as its inertial reference changes from still air to rising air and it starts to go up directly - this happens pretty quickly, but in the transition it also experiences an increase in angle of attack which activates the short-period longitudinal mode. Given the geometry you can imagine that a vertical air movement has much more of an effect on AOA than a horizontal gust of similar velocity so the sort-period response should be much more energetic.
>
> The other difference is that horizontal gusts tend to look like a "one minus cosine" profile (ramp up and back down) whereas thermal ramp up but don't really ramp back down until you fly out of them several seconds later.
>
> Of course vertical gusts that are not associated with thermals look more like thermals in everything except this symmetric versus asymmetric profile so if the big surge you feel isn't reversed immediately it's more likely a thermal.
>
> If you are familiar with concepts of aircraft dynamics and control theory this article is somewhat informative:
>
> http://scialert.net/fulltext/?doi=srj.2008.17.28
>
> I think to have a vario filter out horizontal gusts you would need to have a dynamic model for the glider and both accelerometers and angular rate gyros plus air data. A simple Kalman filter could then solve for airmass movement and generate a three-dimensional airmass vector in real time. You're only really interested in the Z component so you'd discard the other info unless you were curious about decoding what your body was telling you.
>
> Whether this is the approach vario designers are taking, whether the varios have the sensors to measure all the linear and angular rates and accelerations and whether the effects are pronounced enough to measure clearly amidst all the noise, control inputs and measurement errors and lags I couldn't really say.
>
> 9B

One problem complicating this is that thermals are normally accompanied by local horizontal "gusts" which are actually sustained flow field (as mentioned in some of the above posts).

However, if the phugoid response difference is your only signal, that is going to be a challenge. Most gliders are flown near the rear of the CG range, and stability pretty weak, therefore small changes in phugoid response vanishingly small. The g force you experience in either to a horizontal or a vertical gust due to changes in airspeed or AOA will be far greater than that due to stability response of the glider, even disregarding normal control movements - which are going to be happening also.

The Butterfly has full 3 axis accelerometer, rate gyro, and magnetometer (as well as air data) as I understand it, and are using this data with Kalman filters to generate an air mass movement vector in real time at approximately a 20 Hz rate. From this it displays a stable AHRS and fully inertially derived horizontal and vertical air mass movement indications which seem to be at least somewhat accurate. These provide considerably more color on what happens in the air than I was used to seeing on a good variometer. It seems to be both of academic and practical interest. In steady state, the barographicly derived vario and inertially derived VAM match pretty well. But in transient states, they frequently vary quite a bit and it is that variation which is interesting.

Something as yet unexplored is there are probably pressure gradients near thermals accompanying the wind gradients. Your barographic vario must be disturbed by those. I think I see evidence of this but it is a little hard to sort out from all the other effects.

[Andy Blackburn[_3_]]

On Wednesday, October 29, 2014 1:38:45 PM UTC-7, jfitch wrote:
>
> One problem complicating this is that thermals are normally accompanied by local horizontal "gusts" which are actually sustained flow field (as mentioned in some of the above posts).

Signal to noise can always be a problem - the good news should be that if the air is really going up you ought to be able to pick that out, but I agree if there is turbulence on the thermal entry that has greater velocity than the thermal itself and/or goes on for a long way a human observer won't be able to integrate the net effects for long enough to figure out what is going on. A computer might have a better shot at it.

> However, if the phugoid response difference is your only signal, that is going to be a challenge.

I was saying something a bit different. In the case of a horizontal gust the main dynamic reaction from the glider is some modest horizontal deceleration and a slow pitch up followed by a slow pitch down (post-gust) from the phugoid response. In a thermal entry you get mostly a vertical surge plus some downward pitching moment from the short period response if the glider has static stability. Most modern gliders don't benefit from being flown at the aft limit but even if you do the response should be different. If you have a glider that generates a nose-up pitching moment from an increase in angle of attack, that would be a real handful to fly even under benign conditions. This is at least some of the reason why thermals "feel" different. That surge you feel has a different linear acceleration vector and a different (opposite) pitch response.

If the Butterfly uses Kalman filters to separate out the air mass movement that is exactly what I was suggesting (and attempting to explain why) - you ought to be able to pick out the air movement vector IF you have the right onboard sensors AND you have an accurate enough dynamic model for the glider. The better the model represents all the aerodynamic and inertial coefficients the more accurate the answer should be. I could also imagine intelligently looking not just at the instantaneous airmass velocity, but also the profile of thermals for a given day to help identify good ones from bad ones, though that is a much more complex matter.

Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.

9B

[jfitch]

On Thursday, October 30, 2014 4:59:22 AM UTC-7, Andy Blackburn wrote:
> On Wednesday, October 29, 2014 1:38:45 PM UTC-7, jfitch wrote:
> >
> > One problem complicating this is that thermals are normally accompanied by local horizontal "gusts" which are actually sustained flow field (as mentioned in some of the above posts).
>
> Signal to noise can always be a problem - the good news should be that if the air is really going up you ought to be able to pick that out, but I agree if there is turbulence on the thermal entry that has greater velocity than the thermal itself and/or goes on for a long way a human observer won't be able to integrate the net effects for long enough to figure out what is going on. A computer might have a better shot at it.
>
> > However, if the phugoid response difference is your only signal, that is going to be a challenge.
>
> I was saying something a bit different. In the case of a horizontal gust the main dynamic reaction from the glider is some modest horizontal deceleration and a slow pitch up followed by a slow pitch down (post-gust) from the phugoid response. In a thermal entry you get mostly a vertical surge plus some downward pitching moment from the short period response if the glider has static stability. Most modern gliders don't benefit from being flown at the aft limit but even if you do the response should be different. If you have a glider that generates a nose-up pitching moment from an increase in angle of attack, that would be a real handful to fly even under benign conditions. This is at least some of the reason why thermals "feel" different. That surge you feel has a different linear acceleration vector and a different (opposite) pitch response.
>
> If the Butterfly uses Kalman filters to separate out the air mass movement that is exactly what I was suggesting (and attempting to explain why) - you ought to be able to pick out the air movement vector IF you have the right onboard sensors AND you have an accurate enough dynamic model for the glider. The better the model represents all the aerodynamic and inertial coefficients the more accurate the answer should be. I could also imagine intelligently looking not just at the instantaneous airmass velocity, but also the profile of thermals for a given day to help identify good ones from bad ones, though that is a much more complex matter.
>
> Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.
>
> 9B

I agree mostly. A horizontal gust WILL produce a vertical acceleration and this can be quite strong due to the V^2 term in dynamic pressure. This can produce a instantaneous response in the glider that is pure free body effect, superimposed on static aerodynamic stability, and they will normally be opposite. In a vertical gust the effects will in the same direction. In my experience, in strong thermals the dynamic accelerations will be of far greater magnitude than static stability effects, swamping that signal (and eliminating the need, for the most part, to model the glider dynamics closely).. On weak days or with soft well behaved thermals, maybe - but where I fly we are rarely cursed with those conditions. The horizontal air movement in and around thermals is far greater than I thought, until I "instrumented up". Once you know its there, you begin to look critically for confirming evidence and discover that is is there.

[Andy Blackburn[_3_]]

On Thursday, October 30, 2014 10:09:13 AM UTC-7, jfitch wrote:
> On Thursday, October 30, 2014 4:59:22 AM UTC-7, Andy Blackburn wrote:
> > On Wednesday, October 29, 2014 1:38:45 PM UTC-7, jfitch wrote:
> > >
> > > One problem complicating this is that thermals are normally accompanied by local horizontal "gusts" which are actually sustained flow field (as mentioned in some of the above posts).
> >
> > Signal to noise can always be a problem - the good news should be that if the air is really going up you ought to be able to pick that out, but I agree if there is turbulence on the thermal entry that has greater velocity than the thermal itself and/or goes on for a long way a human observer won't be able to integrate the net effects for long enough to figure out what is going on. A computer might have a better shot at it.
> >
> > > However, if the phugoid response difference is your only signal, that is going to be a challenge.
> >
> > I was saying something a bit different. In the case of a horizontal gust the main dynamic reaction from the glider is some modest horizontal deceleration and a slow pitch up followed by a slow pitch down (post-gust) from the phugoid response. In a thermal entry you get mostly a vertical surge plus some downward pitching moment from the short period response if the glider has static stability. Most modern gliders don't benefit from being flown at the aft limit but even if you do the response should be different. If you have a glider that generates a nose-up pitching moment from an increase in angle of attack, that would be a real handful to fly even under benign conditions. This is at least some of the reason why thermals "feel" different. That surge you feel has a different linear acceleration vector and a different (opposite) pitch response.
> >
> > If the Butterfly uses Kalman filters to separate out the air mass movement that is exactly what I was suggesting (and attempting to explain why) - you ought to be able to pick out the air movement vector IF you have the right onboard sensors AND you have an accurate enough dynamic model for the glider. The better the model represents all the aerodynamic and inertial coefficients the more accurate the answer should be. I could also imagine intelligently looking not just at the instantaneous airmass velocity, but also the profile of thermals for a given day to help identify good ones from bad ones, though that is a much more complex matter.
> >
> > Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.
> >
> > 9B
>
> I agree mostly. A horizontal gust WILL produce a vertical acceleration and this can be quite strong due to the V^2 term in dynamic pressure. This can produce a instantaneous response in the glider that is pure free body effect, superimposed on static aerodynamic stability, and they will normally be opposite. In a vertical gust the effects will in the same direction. In my experience, in strong thermals the dynamic accelerations will be of far greater magnitude than static stability effects, swamping that signal (and eliminating the need, for the most part, to model the glider dynamics closely). On weak days or with soft well behaved thermals, maybe - but where I fly we are rarely cursed with those conditions. The horizontal air movement in and around thermals is far greater than I thought, until I "instrumented up". Once you know its there, you begin to look critically for confirming evidence and discover that is is there.

I learned something from the discussion I need to find a way to go test. I've always had the sense that a decent thermal gave you a surge that felt a little tail-high. Like you were being shoved upward and a bit forward. Stick thermals have the opposite pitch sensation as do horizontal gusts - though I am less good at recognizing gusts except as random vario readings. I need to confirm whether the sensation comes from the coupling of the thermal's transient vertical air movement through to short-period pitch response via the increase in AOA. A little math and some flying are in order.

9B

[jfitch]

On Thursday, October 30, 2014 3:54:54 PM UTC-7, Andy Blackburn wrote:
> On Thursday, October 30, 2014 10:09:13 AM UTC-7, jfitch wrote:
> > On Thursday, October 30, 2014 4:59:22 AM UTC-7, Andy Blackburn wrote:
> > > On Wednesday, October 29, 2014 1:38:45 PM UTC-7, jfitch wrote:
> > > >
> > > > One problem complicating this is that thermals are normally accompanied by local horizontal "gusts" which are actually sustained flow field (as mentioned in some of the above posts).
> > >
> > > Signal to noise can always be a problem - the good news should be that if the air is really going up you ought to be able to pick that out, but I agree if there is turbulence on the thermal entry that has greater velocity than the thermal itself and/or goes on for a long way a human observer won't be able to integrate the net effects for long enough to figure out what is going on. A computer might have a better shot at it.
> > >
> > > > However, if the phugoid response difference is your only signal, that is going to be a challenge.
> > >
> > > I was saying something a bit different. In the case of a horizontal gust the main dynamic reaction from the glider is some modest horizontal deceleration and a slow pitch up followed by a slow pitch down (post-gust) from the phugoid response. In a thermal entry you get mostly a vertical surge plus some downward pitching moment from the short period response if the glider has static stability. Most modern gliders don't benefit from being flown at the aft limit but even if you do the response should be different. If you have a glider that generates a nose-up pitching moment from an increase in angle of attack, that would be a real handful to fly even under benign conditions. This is at least some of the reason why thermals "feel" different. That surge you feel has a different linear acceleration vector and a different (opposite) pitch response.
> > >
> > > If the Butterfly uses Kalman filters to separate out the air mass movement that is exactly what I was suggesting (and attempting to explain why) - you ought to be able to pick out the air movement vector IF you have the right onboard sensors AND you have an accurate enough dynamic model for the glider. The better the model represents all the aerodynamic and inertial coefficients the more accurate the answer should be. I could also imagine intelligently looking not just at the instantaneous airmass velocity, but also the profile of thermals for a given day to help identify good ones from bad ones, though that is a much more complex matter.
> > >
> > > Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.
> > >
> > > 9B
> >
> > I agree mostly. A horizontal gust WILL produce a vertical acceleration and this can be quite strong due to the V^2 term in dynamic pressure. This can produce a instantaneous response in the glider that is pure free body effect, superimposed on static aerodynamic stability, and they will normally be opposite. In a vertical gust the effects will in the same direction. In my experience, in strong thermals the dynamic accelerations will be of far greater magnitude than static stability effects, swamping that signal (and eliminating the need, for the most part, to model the glider dynamics closely). On weak days or with soft well behaved thermals, maybe - but where I fly we are rarely cursed with those conditions. The horizontal air movement in and around thermals is far greater than I thought, until I "instrumented up". Once you know its there, you begin to look critically for confirming evidence and discover that is is there.
>
> I learned something from the discussion I need to find a way to go test. I've always had the sense that a decent thermal gave you a surge that felt a little tail-high. Like you were being shoved upward and a bit forward. Stick thermals have the opposite pitch sensation as do horizontal gusts - though I am less good at recognizing gusts except as random vario readings. I need to confirm whether the sensation comes from the coupling of the thermal's transient vertical air movement through to short-period pitch response via the increase in AOA. A little math and some flying are in order.
>
> 9B

Or just basic statics: if the CG is ahead of the lifting center of the wing the upward acceleration causes a pitch down moment.

[Andy Blackburn[_3_]]

On Friday, October 31, 2014 8:08:06 AM UTC-7, jfitch wrote:
> On Thursday, October 30, 2014 3:54:54 PM UTC-7, Andy Blackburn wrote:
> > On Thursday, October 30, 2014 10:09:13 AM UTC-7, jfitch wrote:
> > > On Thursday, October 30, 2014 4:59:22 AM UTC-7, Andy Blackburn wrote:
> > > > On Wednesday, October 29, 2014 1:38:45 PM UTC-7, jfitch wrote:
> > > > >
> > > > > One problem complicating this is that thermals are normally accompanied by local horizontal "gusts" which are actually sustained flow field (as mentioned in some of the above posts).
> > > >
> > > > Signal to noise can always be a problem - the good news should be that if the air is really going up you ought to be able to pick that out, but I agree if there is turbulence on the thermal entry that has greater velocity than the thermal itself and/or goes on for a long way a human observer won't be able to integrate the net effects for long enough to figure out what is going on. A computer might have a better shot at it.
> > > >
> > > > > However, if the phugoid response difference is your only signal, that is going to be a challenge.
> > > >
> > > > I was saying something a bit different. In the case of a horizontal gust the main dynamic reaction from the glider is some modest horizontal deceleration and a slow pitch up followed by a slow pitch down (post-gust) from the phugoid response. In a thermal entry you get mostly a vertical surge plus some downward pitching moment from the short period response if the glider has static stability. Most modern gliders don't benefit from being flown at the aft limit but even if you do the response should be different. If you have a glider that generates a nose-up pitching moment from an increase in angle of attack, that would be a real handful to fly even under benign conditions. This is at least some of the reason why thermals "feel" different. That surge you feel has a different linear acceleration vector and a different (opposite) pitch response.
> > > >
> > > > If the Butterfly uses Kalman filters to separate out the air mass movement that is exactly what I was suggesting (and attempting to explain why) - you ought to be able to pick out the air movement vector IF you have the right onboard sensors AND you have an accurate enough dynamic model for the glider. The better the model represents all the aerodynamic and inertial coefficients the more accurate the answer should be. I could also imagine intelligently looking not just at the instantaneous airmass velocity, but also the profile of thermals for a given day to help identify good ones from bad ones, though that is a much more complex matter.
> > > >
> > > > Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.
> > > >
> > > > 9B
> > >
> > > I agree mostly. A horizontal gust WILL produce a vertical acceleration and this can be quite strong due to the V^2 term in dynamic pressure. This can produce a instantaneous response in the glider that is pure free body effect, superimposed on static aerodynamic stability, and they will normally be opposite. In a vertical gust the effects will in the same direction. In my experience, in strong thermals the dynamic accelerations will be of far greater magnitude than static stability effects, swamping that signal (and eliminating the need, for the most part, to model the glider dynamics closely). On weak days or with soft well behaved thermals, maybe - but where I fly we are rarely cursed with those conditions. The horizontal air movement in and around thermals is far greater than I thought, until I "instrumented up". Once you know its there, you begin to look critically for confirming evidence and discover that is is there.
> >
> > I learned something from the discussion I need to find a way to go test.. I've always had the sense that a decent thermal gave you a surge that felt a little tail-high. Like you were being shoved upward and a bit forward. Stick thermals have the opposite pitch sensation as do horizontal gusts - though I am less good at recognizing gusts except as random vario readings. I need to confirm whether the sensation comes from the coupling of the thermal's transient vertical air movement through to short-period pitch response via the increase in AOA. A little math and some flying are in order.
> >
> > 9B
>
> Or just basic statics: if the CG is ahead of the lifting center of the wing the upward acceleration causes a pitch down moment.

True that - I wonder if one effect is reliably larger than the other for a typical glider with a cg midway between forward and aft limits. In any case a solid thermal entry should generate some nose-down pitch. Also seems that if you want to feel what's going on don't mess with the elevator too much..

9B

[SoaringXCellence]

Think in terms of the relative wind and the trim speed:

When we enter the thermal, the airmass changes, there is a upward component, the nose pitches down relative to the horizon, but the trim speed remains the same. We see a pitch down but the relative wind is the same.

The opposite is true leaving the thermal or in a downdraft: it seems we can't get the nose down far enough as the downdraft pitches the nose up, or at least decreases the AoA.

Like Moffat said (paraphrase) it's easier to accelerate in lift than sink.

[krasw]

On Thursday, 30 October 2014 13:59:22 UTC+2, Andy Blackburn wrote:
> Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.
>
> 9B


Could you elaborate? I ran the numbers quickly, there is usually temperature gradient of 0,5-2 degrees (centigrade) between thermal core and "free air" around it. If we think normal smallish thermal as couple of hundred meters in radius, we would get average temperature gradient of 0,25-1 degree/100meters between core and surrouding air. Glider with temp sensors at wingtips would probably reguire 0,01-0,05 deg resolution of sensors to give any information. It could be doable, though, relative differences are easier to measure than absolute. It could give you a sort of "left or right" indication when close to thermal.

[Dan Marotta]

This was discussed at length in Soaring magazine back in the 80s or,
maybe earlier. A great winter topic which we'll all promptly forget
with the return of thermal soaring season.

Dan Marotta

On 11/2/2014 5:51 AM, krasw wrote:
> On Thursday, 30 October 2014 13:59:22 UTC+2, Andy Blackburn wrote:
>> Thermals also have temperature gradients - though the experiments I participated in recently were not conclusive.
>>
>> 9B
>
> Could you elaborate? I ran the numbers quickly, there is usually temperature gradient of 0,5-2 degrees (centigrade) between thermal core and "free air" around it. If we think normal smallish thermal as couple of hundred meters in radius, we would get average temperature gradient of 0,25-1 degree/100meters between core and surrouding air. Glider with temp sensors at wingtips would probably reguire 0,01-0,05 deg resolution of sensors to give any information. It could be doable, though, relative differences are easier to measure than absolute. It could give you a sort of "left or right" indication when close to thermal.

[Andy Blackburn[_3_]]

On Sunday, November 2, 2014 4:51:43 AM UTC-8, krasw wrote:
>
> Could you elaborate? I ran the numbers quickly, there is usually temperature gradient of 0,5-2 degrees (centigrade) between thermal core and "free air" around it. If we think normal smallish thermal as couple of hundred meters in radius, we would get average temperature gradient of 0,25-1 degree/100meters between core and surrouding air. Glider with temp sensors at wingtips would probably reguire 0,01-0,05 deg resolution of sensors to give any information. It could be doable, though, relative differences are easier to measure than absolute. It could give you a sort of "left or right"

That is the basic idea. I know from experimentation that there are measurable temperature variations out there, it's just not obvious to me what they mean with respect to the vertical movement of the airmass.

I'm curious what your running the numbers looks like. I admit I don't have a good mental model for how thermals work from a thermodynamic and aerodynamic perspective. I thought it had something to do with the fact that warm air was less dense and therefore buoyant. How that buoyancy accelerates a volume of air until some form of resistance at the edges progressively resists the acceleration and a steady rate of upward velocity is reached is beyond my understanding at a level detailed enough to relate thermal strength to temperature differences.

As to the temperature gradient across the thermal - I'm not sure it's linear from the edge to the center. Imagine a volume of air rising at 500 FPM. Presumably you have some mixing at the edges but the rest of the heat transfer would mostly be conductive over a period of 10 minutes before the thermal reaches, say, 5000'. I'm not sure what all the coefficients are, but it isn't 100% obvious to me that you'd end up with a linear temperature gradient all the way to the center of the thermal since there is so much new warm air being introduced continuously from the bottom, there isn't much time for heat to transfer to the outside air and air isn't that great a heat conductor in the first place. Have there been studies done?

9B

[krasw]

On Sunday, 2 November 2014 21:03:39 UTC+2, Andy Blackburn wrote:
> I'm curious what your running the numbers looks like. I admit I don't have a good mental model for how thermals work from a thermodynamic and aerodynamic perspective. I thought it had something to do with the fact that warm air was less dense and therefore buoyant. How that buoyancy accelerates a volume of air until some form of resistance at the edges progressively resists the acceleration and a steady rate of upward velocity is reached is beyond my understanding at a level detailed enough to relate thermal strength to temperature differences.
>
> As to the temperature gradient across the thermal - I'm not sure it's linear from the edge to the center. Imagine a volume of air rising at 500 FPM. Presumably you have some mixing at the edges but the rest of the heat transfer would mostly be conductive over a period of 10 minutes before the thermal reaches, say, 5000'. I'm not sure what all the coefficients are, but it isn't 100% obvious to me that you'd end up with a linear temperature gradient all the way to the center of the thermal since there is so much new warm air being introduced continuously from the bottom, there isn't much time for heat to transfer to the outside air and air isn't that great a heat conductor in the first place. Have there been studies done?
>
> 9B

I can't quote any sources but I bet digging into Google Scholar would result studies (boundary layer physics would be good place to start). I know that warm air in thermal bubble or column is little bit warmer (numbers quoted earlier are realistic) than surround. That temperature difference is maintained with altitude (per hydrostatic equation), and thermal is surprisingly "closed" system, mixing at the edge of ascending air is quite small compared to thermal volume. It's true that average temperature gradient is not realistic figure, the gradient is probable decade higher at edge of thermal than figure I threw out of my sleeve.

I think running constant temp difference analysis would be quite easy with simple and cheap linux computer, temp signals going through DA conversion to digital domain. Sensors could be calibrated over time to match each other, so small differences could be readable, even if absolute accuracy is something like 0,1 degrees. If this has been done in 80's, technology probably was analog electronics. Nowadays it would be more software project.

[Peter Purdie[_3_]]

There have been few systematic studies of thermal structure; the work we
did in the 1970s at Reading University with an insrtumented Falke was
reported at OSTIV Conferences in 78 and 81. The main focus of the research
was heat and water vapour transfer from surface into the troposhere (the
'fuel' that powers the heat engine we call weather). However, it was not
difficult to extract from the data some useful information of thermal
structure. For the purposes of the analysis, a thermal was defined as an
area of positive vertical air motion greater than 1 m/s and more that 50
metres horizontal extent. An important finding is that above about
one-third of the distance to the inversion, there is no significant
temperature difference between the thermal and surrounding air; near the
inversion the temperature is actually lower since the warmer air above the
inversion is being mixed down around the rising air. Humidity is a
significant indicator, H2O molecules being lighter than O2 or N2.
Therefore thermal 'detectors' based on temperature are a waste of time. It
would be nice to have a remote sensor detecting movement of entrained dust
particles, but this would take all the fun out of soaring.

The best thermal indicator remains to be a glider flown by a good pilot
circling tightly and going up fast. (Or a soaring bird).

At 20:14 02 November 2014, krasw wrote:
>On Sunday, 2 November 2014 21:03:39 UTC+2, Andy Blackburn wrote:
>> I'm curious what your running the numbers looks like. I admit I don't
>hav=
>e a good mental model for how thermals work from a thermodynamic and
>aerody=
>namic perspective. I thought it had something to do with the fact that
>warm=
> air was less dense and therefore buoyant. How that buoyancy accelerates
a
>=
>volume of air until some form of resistance at the edges progressively
>resi=
>sts the acceleration and a steady rate of upward velocity is reached is
>bey=
>ond my understanding at a level detailed enough to relate thermal
strength
>=
>to temperature differences.
>>=20
>> As to the temperature gradient across the thermal - I'm not sure it's
>lin=
>ear from the edge to the center. Imagine a volume of air rising at 500
>FPM.=
> Presumably you have some mixing at the edges but the rest of the heat
>tran=
>sfer would mostly be conductive over a period of 10 minutes before the
>ther=
>mal reaches, say, 5000'. I'm not sure what all the coefficients are, but
>i=
>t isn't 100% obvious to me that you'd end up with a linear temperature
>grad=
>ient all the way to the center of the thermal since there is so much new
>wa=
>rm air being introduced continuously from the bottom, there isn't much
>time=
> for heat to transfer to the outside air and air isn't that great a heat
>co=
>nductor in the first place. Have there been studies done?
>>=20
>> 9B
>
>I can't quote any sources but I bet digging into Google Scholar would
>resul=
>t studies (boundary layer physics would be good place to start). I know
>tha=
>t warm air in thermal bubble or column is little bit warmer (numbers
>quoted=
> earlier are realistic) than surround. That temperature difference is
>maint=
>ained with altitude (per hydrostatic equation), and thermal is
>surprisingly=
> "closed" system, mixing at the edge of ascending air is quite small
>compar=
>ed to thermal volume. It's true that average temperature gradient is not
>re=
>alistic figure, the gradient is probable decade higher at edge of thermal
>t=
>han figure I threw out of my sleeve.
>
>I think running constant temp difference analysis would be quite easy
with
>=
>simple and cheap linux computer, temp signals going through DA conversion
>t=
>o digital domain. Sensors could be calibrated over time to match each
>other=
>, so small differences could be readable, even if absolute accuracy is
>some=
>thing like 0,1 degrees. If this has been done in 80's, technology
probably
>=
>was analog electronics. Nowadays it would be more software project.
>

[Peter Purdie[_3_]]

For some reason r.a.s truncated the last letter of each line of the post
below. Mostly interpretable, but the horizontal dimension was 50 metres


At 11:03 03 November 2014, Peter Purdie wrote:
>There have been few systematic studies of thermal structure; the work w
>did in the 1970s at Reading University with an insrtumented Falke wa
>reported at OSTIV Conferences in 78 and 81. The main focus of the researc
>was heat and water vapour transfer from surface into the troposhere (th
>'fuel' that powers the heat engine we call weather). However, it was no
>difficult to extract from the data some useful information of therma
>structure. For the purposes of the analysis, a thermal was defined as a
>area of positive vertical air motion greater than 1 m/s and more that 5
>metres horizontal extent. An important finding is that above abou
>one-third of the distance to the inversion, there is no significan
>temperature difference between the thermal and surrounding air; near th
>inversion the temperature is actually lower since the warmer air above th
>inversion is being mixed down around the rising air. Humidity is
>significant indicator, H2O molecules being lighter than O2 or N2.
>Therefore thermal 'detectors' based on temperature are a waste of time.
I
>would be nice to have a remote sensor detecting movement of entrained dus
>particles, but this would take all the fun out of soaring.
>
>The best thermal indicator remains to be a glider flown by a good pilo
>circling tightly and going up fast. (Or a soaring bird).
>
>At 20:14 02 November 2014, krasw wrote:
>>On Sunday, 2 November 2014 21:03:39 UTC+2, Andy Blackburn wrote:
>>> I'm curious what your running the numbers looks like. I admit I don't
>>hav=
>>e a good mental model for how thermals work from a thermodynamic and
>>aerody=
>>namic perspective. I thought it had something to do with the fact that
>>warm=
>> air was less dense and therefore buoyant. How that buoyancy accelerate
>a
>>=
>>volume of air until some form of resistance at the edges progressively
>>resi=
>>sts the acceleration and a steady rate of upward velocity is reached is
>>bey=
>>ond my understanding at a level detailed enough to relate therma
>strength
>>=
>>to temperature differences.
>>>=20
>>> As to the temperature gradient across the thermal - I'm not sure it's
>>lin=
>>ear from the edge to the center. Imagine a volume of air rising at 500
>>FPM.=
>> Presumably you have some mixing at the edges but the rest of the heat
>>tran=
>>sfer would mostly be conductive over a period of 10 minutes before the
>>ther=
>>mal reaches, say, 5000'. I'm not sure what all the coefficients are,
but
>>i=
>>t isn't 100% obvious to me that you'd end up with a linear temperature
>>grad=
>>ient all the way to the center of the thermal since there is so much new
>>wa=
>>rm air being introduced continuously from the bottom, there isn't much
>>time=
>> for heat to transfer to the outside air and air isn't that great a heat
>>co=
>>nductor in the first place. Have there been studies done?
>>>=20
>>> 9B
>>
>>I can't quote any sources but I bet digging into Google Scholar would
>>resul=
>>t studies (boundary layer physics would be good place to start). I know
>>tha=
>>t warm air in thermal bubble or column is little bit warmer (numbers
>>quoted=
>> earlier are realistic) than surround. That temperature difference is
>>maint=
>>ained with altitude (per hydrostatic equation), and thermal is
>>surprisingly=
>> "closed" system, mixing at the edge of ascending air is quite small
>>compar=
>>ed to thermal volume. It's true that average temperature gradient is not
>>re=
>>alistic figure, the gradient is probable decade higher at edge of
thermal
>>t=
>>han figure I threw out of my sleeve.
>>
>>I think running constant temp difference analysis would be quite eas
>with
>>=
>>simple and cheap linux computer, temp signals going through DA
conversion
>>t=
>>o digital domain. Sensors could be calibrated over time to match each
>>other=
>>, so small differences could be readable, even if absolute accuracy is
>>some=
>>thing like 0,1 degrees. If this has been done in 80's, technolog
>probably
>>=
>>was analog electronics. Nowadays it would be more software project.
>>
>
>

[Andy Blackburn[_3_]]

On Monday, November 3, 2014 3:15:06 AM UTC-8, pete purdie wrote:
>...An important finding is that above about
> one-third of the distance to the inversion, there is no significant
> temperature difference between the thermal and surrounding air; near the
> inversion the temperature is actually lower since the warmer air above the
> inversion is being mixed down around the rising air. Humidity is a
> significant indicator, H2O molecules being lighter than O2 or N2.

So thermals rise, not because of the sun heating the ground and making a bubble of warm air that breaks free, but because somehow a more humid bubble of air is created. What mechanism creates the bubble of humidity?

9B

[[email protected]]

On Monday, November 3, 2014 8:33:24 AM UTC-5, Andy Blackburn wrote:
> On Monday, November 3, 2014 3:15:06 AM UTC-8, pete purdie wrote:
> >...An important finding is that above about
> > one-third of the distance to the inversion, there is no significant
> > temperature difference between the thermal and surrounding air; near the
> > inversion the temperature is actually lower since the warmer air above the
> > inversion is being mixed down around the rising air. Humidity is a
> > significant indicator, H2O molecules being lighter than O2 or N2.
>
> So thermals rise, not because of the sun heating the ground and making a bubble of warm air that breaks free, but because somehow a more humid bubble of air is created. What mechanism creates the bubble of humidity?
>
> 9B

Differences in ground surface condition.
There is also a variation in electrical potential between thermals and surrounding air. This was explored in the 70's.
UH

[Peter Purdie[_3_]]

As should have been clear from what I wrote, in the bottom third of the
thermal the air is still warmer, but steadily mixing in surrounding air.
Once properly formed the momentum of the tons of air moving is presumed to
keep the circulation active. Air close to the ground is also more humid
which increases the buoyancy. We did not fully model the mechanism, just
took measurements that illustrated the scale and characteristics of
meso-scale air motion in a range of situations, including convective
weather.


At 13:33 03 November 2014, Andy Blackburn wrote:
>On Monday, November 3, 2014 3:15:06 AM UTC-8, pete purdie wrote:
>>...An important finding is that above about
>> one-third of the distance to the inversion, there is no significant
>> temperature difference between the thermal and surrounding air; near
the
>> inversion the temperature is actually lower since the warmer air above
>the
>> inversion is being mixed down around the rising air. Humidity is a
>> significant indicator, H2O molecules being lighter than O2 or N2.
>
>So thermals rise, not because of the sun heating the ground and making a
>bubble of warm air that breaks free, but because somehow a more humid
>bubble of air is created. What mechanism creates the bubble of humidity?
>
>9B
>
>

[krasw]

On Monday, 3 November 2014 15:33:24 UTC+2, Andy Blackburn wrote:
> On Monday, November 3, 2014 3:15:06 AM UTC-8, pete purdie wrote:
> >...An important finding is that above about
> > one-third of the distance to the inversion, there is no significant
> > temperature difference between the thermal and surrounding air; near the
> > inversion the temperature is actually lower since the warmer air above the
> > inversion is being mixed down around the rising air. Humidity is a
> > significant indicator, H2O molecules being lighter than O2 or N2.
>
> So thermals rise, not because of the sun heating the ground and making a bubble of warm air that breaks free, but because somehow a more humid bubble of air is created. What mechanism creates the bubble of humidity?
>
> 9B

No it's differences in temperature. Humidity is transferred up to inversion layer with thermals (closed system), and air above inversion is much drier.. It's a good point however that warmer air from inversion is sucked down, so temperature sensing might be useless there. I don't see it totally useless when searching for a thermal closer to ground. Interesting topic.

[Andy Blackburn[_3_]]

On Monday, November 3, 2014 5:38:09 AM UTC-8, wrote:

> There is also a variation in electrical potential between thermals and surrounding air.

Enough to charge the batteries on one's FES? ;-)

[Andy Blackburn[_3_]]

On Monday, November 3, 2014 6:15:05 AM UTC-8, pete purdie wrote:
> Once properly formed the momentum of the tons of air moving is presumed to
> keep the circulation active.

Not entirely sure I buy momentum as a first-order effect since blue thermals don't typically overrun the top of the invasion level by very much, so I can't imagine the top 2/3 of the thermal is simply momentum. Also, if it's thoroughly mixed from a temperature perspective wouldn't it also be mixed from a humidity perspective as well so it wouldn't be rising from having higher humidity either?

Curious.

9B

[Peter Purdie[_3_]]

Like I said, we didn't attempt to fully model the
mechanism.

Richard Feynmen: 'If the measurements don't agree with
the theory, then the theory is probably wrong. If they do,
the theory might be right.'

At 14:38 03 November 2014, Andy Blackburn wrote:
>On Monday, November 3, 2014 6:15:05 AM UTC-8, pete purdie wrote:
>> Once properly formed the momentum of the tons of air moving is presumed
>t=
>o
>> keep the circulation active. =20
>
>Not entirely sure I buy momentum as a first-order effect since blue
>thermal=
>s don't typically overrun the top of the invasion level by very much, so
I
>=
>can't imagine the top 2/3 of the thermal is simply momentum. Also, if
it's
>=
>thoroughly mixed from a temperature perspective wouldn't it also be mixed
>f=
>rom a humidity perspective as well so it wouldn't be rising from having
>hig=
>her humidity either?
>
>Curious.
>
>9B
>
>

[[email protected]]

OK btt..

The S80 arrived after some desperate 6 month delay last week and went directly into the ship.

Flying with it the first time yesterday 3.5 hours showed exelent performance.
Great visibility even with sunshine and blue sky.
I like the fast response without any sign of being nerveous.
Even with response times of just 1.5s..

The big and bright display could be noticed without even having my eyes pointing to the dashboard.

Software ins not at the feature level of the V7 yet but will be soon as the developer promised.


So thumbs up for now!

P.

[Andy Blackburn[_3_]]

On Monday, November 3, 2014 7:15:06 AM UTC-8, pete purdie wrote:
> Like I said, we didn't attempt to fully model the
> mechanism.
>
> Richard Feynmen: 'If the measurements don't agree with
> the theory, then the theory is probably wrong. If they do,
> the theory might be right.'
>

Truth.

[krasw]

On Monday, 3 November 2014 16:15:05 UTC+2, pete purdie wrote:
> As should have been clear from what I wrote, in the bottom third of the
> thermal the air is still warmer, but steadily mixing in surrounding air.
> Once properly formed the momentum of the tons of air moving is presumed to
> keep the circulation active. Air close to the ground is also more humid
> which increases the buoyancy. We did not fully model the mechanism, just
> took measurements that illustrated the scale and characteristics of
> meso-scale air motion in a range of situations, including convective
> weather.
>
>
> At 13:33 03 November 2014, Andy Blackburn wrote:
> >On Monday, November 3, 2014 3:15:06 AM UTC-8, pete purdie wrote:
> >>...An important finding is that above about
> >> one-third of the distance to the inversion, there is no significant
> >> temperature difference between the thermal and surrounding air; near
> the
> >> inversion the temperature is actually lower since the warmer air above
> >the
> >> inversion is being mixed down around the rising air. Humidity is a
> >> significant indicator, H2O molecules being lighter than O2 or N2.
> >
> >So thermals rise, not because of the sun heating the ground and making a
> >bubble of warm air that breaks free, but because somehow a more humid
> >bubble of air is created. What mechanism creates the bubble of humidity?
> >
> >9B
> >
> >

Interesting study:

http://journals.ametsoc.org/doi/abs/10.1175/1520-0493%281996%29124%3C0769:TVWTCB%3E2.0.CO%3B2

Figure 6 gives quite good overview of temperature and humidity variability during (weakish) convective activity. Temp. differences are appr. 0,5 deg and humidity 1 g/kg close to ground.

Other Weckwerth papers are worth reading too, IMHO.

[waremark]

Surprised that software features of S80 are not up to V7 currently. What is excluded?

Wonder whether it will become a better vario since it has more sensors. It costs much more than V7.

[Richard[_9_]]

On Tuesday, November 4, 2014 6:00:49 AM UTC-8, waremark wrote:
> Surprised that software features of S80 are not up to V7 currently. What is excluded?
>
> Wonder whether it will become a better vario since it has more sensors. It costs much more than V7.

I have tested the S80 on the bench and it has more features than the V7.
Navigation, AHRS etc.

Richard
www.craggyaero.com

[[email protected]]

I just received my new S80 vario.
It might be helpful for those of us who are just now installing and calibrating our units to share.

Software bugs?
TE vs electronic compensation?
Plumbing the TE line when shared with a mechanical vario (Sage vs Winter vs Borgelt).
Flarm display results and tuning.
Two way communication with a PDA with SeeYou/GN2/etc.

[[email protected]]

Logbook is not implemented yet and Englisch only at the moment..
Different numbers in cruise/circling mode are not implemented like in the V7

AT least the undervolt warning worked for me, as I emptied both of my batteries...:-)

[Craig Funston]

On Tuesday, November 4, 2014 10:13:57 AM UTC-8, wrote:
> Logbook is not implemented yet and Englisch only at the moment..
> Different numbers in cruise/circling mode are not implemented like in the V7
>
> AT least the undervolt warning worked for me, as I emptied both of my batteries...:-)

The V7 is a lovely instrument. If the manufacturer were able to make an extension module that included the inertial vario parts and modify the software to incorporate the module it would be pretty attractive.

Craig
7Q

[Andy Blackburn[_3_]]

On Monday, November 3, 2014 6:38:22 AM UTC-8, Andy Blackburn wrote:
> Not entirely sure I buy momentum as a first-order effect since blue thermals don't typically overrun the top of the invasion level by very much, so I can't imagine the top 2/3 of the thermal is simply momentum. Also, if it's thoroughly mixed from a temperature perspective wouldn't it also be mixed from a humidity perspective as well so it wouldn't be rising from having higher humidity either?
>
> Curious.
>
> 9B

I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.

I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.

9B

[Evan Ludeman[_4_]]

On Tuesday, November 4, 2014 4:38:33 PM UTC-5, Andy Blackburn wrote:
> I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.
>
> I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.
>
> 9B

That's for an object in a vacuum. The thermal isn't surrounded by a vacuum, it's surrounded by air at almost precisely the same density.

T8

[Andy Blackburn[_3_]]

On Tuesday, November 4, 2014 3:04:41 PM UTC-8, Evan Ludeman wrote:
> On Tuesday, November 4, 2014 4:38:33 PM UTC-5, Andy Blackburn wrote:
> > I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.
> >
> > I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.
> >
> > 9B
>
> That's for an object in a vacuum. The thermal isn't surrounded by a vacuum, it's surrounded by air at almost precisely the same density.
>
> T8

Wouldn't that make it go up even less due to the frictional resistance?

[jfitch]

On Tuesday, November 4, 2014 4:24:00 PM UTC-8, Andy Blackburn wrote:
> On Tuesday, November 4, 2014 3:04:41 PM UTC-8, Evan Ludeman wrote:
> > On Tuesday, November 4, 2014 4:38:33 PM UTC-5, Andy Blackburn wrote:
> > > I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.
> > >
> > > I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.
> > >
> > > 9B
> >
> > That's for an object in a vacuum. The thermal isn't surrounded by a vacuum, it's surrounded by air at almost precisely the same density.
> >
> > T8
>
> Wouldn't that make it go up even less due to the frictional resistance?

Just doesn't weigh as much as you assumed

[Evan Ludeman[_4_]]

On Tuesday, November 4, 2014 8:10:44 PM UTC-5, jfitch wrote:
> On Tuesday, November 4, 2014 4:24:00 PM UTC-8, Andy Blackburn wrote:
> > On Tuesday, November 4, 2014 3:04:41 PM UTC-8, Evan Ludeman wrote:
> > > On Tuesday, November 4, 2014 4:38:33 PM UTC-5, Andy Blackburn wrote:
> > > > I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.
> > > >
> > > > I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.
> > > >
> > > > 9B
> > >
> > > That's for an object in a vacuum. The thermal isn't surrounded by a vacuum, it's surrounded by air at almost precisely the same density.
> > >
> > > T8
> >
> > Wouldn't that make it go up even less due to the frictional resistance?
>
> Just doesn't weigh as much as you assumed

Buoyancy.

T8

[Andy Blackburn[_3_]]

On Tuesday, November 4, 2014 5:39:22 PM UTC-8, Evan Ludeman wrote:
> On Tuesday, November 4, 2014 8:10:44 PM UTC-5, jfitch wrote:
> > On Tuesday, November 4, 2014 4:24:00 PM UTC-8, Andy Blackburn wrote:
> > > On Tuesday, November 4, 2014 3:04:41 PM UTC-8, Evan Ludeman wrote:
> > > > On Tuesday, November 4, 2014 4:38:33 PM UTC-5, Andy Blackburn wrote:
> > > > > I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.
> > > > >
> > > > > I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.
> > > > >
> > > > > 9B
> > > >
> > > > That's for an object in a vacuum. The thermal isn't surrounded by a vacuum, it's surrounded by air at almost precisely the same density.
> > > >
> > > > T8
> > >
> > > Wouldn't that make it go up even less due to the frictional resistance?
> >
> > Just doesn't weigh as much as you assumed
>
> Buoyancy.
>
> T8

Added that in. Buoyancy works opposite to gravity but momentum still based on total mass of the air.

The math seems to indicate that the momentum of a bubble of air is actually small compared to the buoyancy effects of even slight changes in temperature. I also looked at air density versus temperature and humidity. The humidity effects are real but generally small as well. Even a giant swing in humidity from 80 percent to 30 percent generates an increase in density equivalent to just 2 degrees F. I can see why it pays to look for thermals downwind of cattle tanks in the desert, and why you might get a kick in the climb rate at several thousand feet, but it doesn't explain for me why thermals go up in the first place.

I suppose this confirms why a Skew-T plot generally predicts thermal heights based on temperature differences - the height where e a parcel of air at the surface, when adiabatically lifted, reaches the ambient temperature in the sounding. There's no adjustment for mixing of the thermal down low and no adjustment for momentum of the rising air or the humidity of the air - the thermal goes to the height where the core of the thermal adiabatically cools to the surrounding air temperature and it stops.

9B

[jfitch]

On Wednesday, November 5, 2014 1:01:27 PM UTC-8, Andy Blackburn wrote:
> On Tuesday, November 4, 2014 5:39:22 PM UTC-8, Evan Ludeman wrote:
> > On Tuesday, November 4, 2014 8:10:44 PM UTC-5, jfitch wrote:
> > > On Tuesday, November 4, 2014 4:24:00 PM UTC-8, Andy Blackburn wrote:
> > > > On Tuesday, November 4, 2014 3:04:41 PM UTC-8, Evan Ludeman wrote:
> > > > > On Tuesday, November 4, 2014 4:38:33 PM UTC-5, Andy Blackburn wrote:
> > > > > > I did the simple physics on this. A volume of air rising at 600 fpm with no other forces acting on it other than gravity has enough momentum to rise an additional 1.6 feet before its upward velocity reaches zero.
> > > > > >
> > > > > > I am now officially at a loss as to why thermals go up if there is no temperature difference versus the surrounding air.
> > > > > >
> > > > > > 9B
> > > > >
> > > > > That's for an object in a vacuum. The thermal isn't surrounded by a vacuum, it's surrounded by air at almost precisely the same density.
> > > > >
> > > > > T8
> > > >
> > > > Wouldn't that make it go up even less due to the frictional resistance?
> > >
> > > Just doesn't weigh as much as you assumed
> >
> > Buoyancy.
> >
> > T8
>
> Added that in. Buoyancy works opposite to gravity but momentum still based on total mass of the air.
>
> The math seems to indicate that the momentum of a bubble of air is actually small compared to the buoyancy effects of even slight changes in temperature. I also looked at air density versus temperature and humidity. The humidity effects are real but generally small as well. Even a giant swing in humidity from 80 percent to 30 percent generates an increase in density equivalent to just 2 degrees F. I can see why it pays to look for thermals downwind of cattle tanks in the desert, and why you might get a kick in the climb rate at several thousand feet, but it doesn't explain for me why thermals go up in the first place.
>
> I suppose this confirms why a Skew-T plot generally predicts thermal heights based on temperature differences - the height where e a parcel of air at the surface, when adiabatically lifted, reaches the ambient temperature in the sounding. There's no adjustment for mixing of the thermal down low and no adjustment for momentum of the rising air or the humidity of the air - the thermal goes to the height where the core of the thermal adiabatically cools to the surrounding air temperature and it stops.
>
> 9B

I think you need to recheck your math. 600 fpm is 10 fps. That would be around 20 ft at 1G with no other retarding forces and mass = weight. But in this case mass >> weight depending on the buoyancy, i.e., much less than 1G deceleration acting on it. When the density matches the surrounding air, the air bubble is weightless (A due to G = 0), and therefore will carry on forever absent another retarding force. Of course as it rises through an inversion of less dense air, it will lose buoyancy and G will begin to have some effect, also there are frictional effects of the surrounding atmosphere which I imagine are hard to calculate. Much for that 1.6 feet though.

[Andy Blackburn[_3_]]

On Wednesday, November 5, 2014 3:10:29 PM UTC-8, jfitch wrote:

> I think you need to recheck your math. 600 fpm is 10 fps. That would be around 20 ft at 1G with no other retarding forces and mass = weight. But in this case mass >> weight depending on the buoyancy, i.e., much less than 1G deceleration acting on it. When the density matches the surrounding air, the air bubble is weightless (A due to G = 0), and therefore will carry on forever absent another retarding force. Of course as it rises through an inversion of less dense air, it will lose buoyancy and G will begin to have some effect, also there are frictional effects of the surrounding atmosphere which I imagine are hard to calculate. Much for that 1.6 feet though.

Must've missed a decimal place, but even with that corrected, the inertial effects seem to be a lot less than the buoyancy effects, which is mostly driven by temperature profile in the atmosphere versus a dry adiabat. Humidity matters a little, but is the equivalent of a a fraction of a degree to maybe a couple of degrees of temperature variation - which is way less than the variations you see in a typical sounding. Temperature seems like more than an order of magnitude more important than humidity, which itself is roughly an order of magnitude more important than inertia effects.

Where's Dr Jack when I need him?

9B

[Craig Funston]

On Wednesday, November 5, 2014 3:22:46 PM UTC-8, Andy Blackburn wrote:
> On Wednesday, November 5, 2014 3:10:29 PM UTC-8, jfitch wrote:
>
> > I think you need to recheck your math. 600 fpm is 10 fps. That would be around 20 ft at 1G with no other retarding forces and mass = weight. But in this case mass >> weight depending on the buoyancy, i.e., much less than 1G deceleration acting on it. When the density matches the surrounding air, the air bubble is weightless (A due to G = 0), and therefore will carry on forever absent another retarding force. Of course as it rises through an inversion of less dense air, it will lose buoyancy and G will begin to have some effect, also there are frictional effects of the surrounding atmosphere which I imagine are hard to calculate. Much for that 1.6 feet though.
>
> Must've missed a decimal place, but even with that corrected, the inertial effects seem to be a lot less than the buoyancy effects, which is mostly driven by temperature profile in the atmosphere versus a dry adiabat. Humidity matters a little, but is the equivalent of a a fraction of a degree to maybe a couple of degrees of temperature variation - which is way less than the variations you see in a typical sounding. Temperature seems like more than an order of magnitude more important than humidity, which itself is roughly an order of magnitude more important than inertia effects.
>
> Where's Dr Jack when I need him?
>
> 9B

The inertial effects are inversely proportional to the thread drift coefficient...

Cheers,
Craig

[jherzog]

There are a couple of nice videos of the S80 in flights has been posted by a Danish soaring club: http://herningsvaeveflyveklub.dk/nyhedsartikler/klubflyene-far-lxnav-s80

The installation is in the back seat of ask ASK-21 -- not sure if it is showing an S80 back seat repeater in use or a primary S80.

[[email protected]]

On Wednesday, November 5, 2014 8:31:07 PM UTC-5, Craig Funston wrote:
> On Wednesday, November 5, 2014 3:22:46 PM UTC-8, Andy Blackburn wrote:
> > On Wednesday, November 5, 2014 3:10:29 PM UTC-8, jfitch wrote:
> >
> > > I think you need to recheck your math. 600 fpm is 10 fps. That would be around 20 ft at 1G with no other retarding forces and mass = weight. But in this case mass >> weight depending on the buoyancy, i.e., much less than 1G deceleration acting on it. When the density matches the surrounding air, the air bubble is weightless (A due to G = 0), and therefore will carry on forever absent another retarding force. Of course as it rises through an inversion of less dense air, it will lose buoyancy and G will begin to have some effect, also there are frictional effects of the surrounding atmosphere which I imagine are hard to calculate. Much for that 1.6 feet though.
> >
> > Must've missed a decimal place, but even with that corrected, the inertial effects seem to be a lot less than the buoyancy effects, which is mostly driven by temperature profile in the atmosphere versus a dry adiabat. Humidity matters a little, but is the equivalent of a a fraction of a degree to maybe a couple of degrees of temperature variation - which is way less than the variations you see in a typical sounding. Temperature seems like more than an order of magnitude more important than humidity, which itself is roughly an order of magnitude more important than inertia effects.
> >
> > Where's Dr Jack when I need him?
> >
> > 9B
>
> The inertial effects are inversely proportional to the thread drift coefficient...
>
> Cheers,
> Craig

Length of the thread is also inversely proportional to relevance to the real world.
UH

[[email protected]]

THanks.
Would be nice to see Flarm, map function, and horizon displays.
Soon