Hi-

I've searched the archives of this oft-discussed topic, but am not finding specific answers I'm seeking. If you have good experience or knowledge about the specific issues below, I would much appreciate your insights.

1) Latency with accuracy. What is the quickest vario with accuracy? Are they all limited by a 1 sec. latency with updates, or do some update faster? While several now describe their inputs as including both pressure sensor and inertial inputs from gyros and accelerometers, I can't find clarity on the mixture of these in the protocol. Some seem to link inertial inputs more to wind/track sensing than vario responses.

2) TE Compensation. Most all offer pneumatic or electronic, and at least some a gain loop on a pneumatic source so that compensation can be adjusted. However, pneumatic comp alone will only be accurate for one condition (g loading, alpha delta, etc.) Whereas electronic gain loops have been around for decades, it seems rather archaic that modification of the input is limited to a single gain function. Does anyone provide modification to several points on a curve whether g loading, v, or another pertinent metric?

I am looking at designing a new set of sensors and instruments that would display fundamentally different parameters for a type of flight strategies/optimization which is inertially based in a rapidly changing frame of reference. However, in the mean time I fly very dynamically and would appreciate experienced and accurate input about current vario offerings. I would also appreciate specific comments from pilots who have experience with both AirGlide (Butterfly), LxNav S8 or 80, and/or ClearNav Varios. Pluses and minuses wrt the above two capabilities in particular and notable general issues would be greatly appreciated.

Thanks, and sorry for posting from my wife's account- I don't post often enough to remember my login commands and am away from home records. You can email me directly if you wish:

Gary Osoba

Hi Gary,

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

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

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

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

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

Best
Christoph

Hi Gary,
Mike Borgelt is developing such a unit, see: http://www.borgeltinstruments.com/?p=126
Called dynamis.

Hello Cristoph-

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

On Thursday, June 21, 2018 at 7:29:22 AM UTC-6, wrote:
> Hi Gary,
>
> I have flown with both, ClearNav (500h) and AirGlide varios (100h). I also used both in parallel last season. In terms of variometry, both varios have a comparable performance. In fact, the readings in climb mode were almost identical. But I preferred the AirGlide user interface, wind calculation and physical quality of the product, so I sold the CNv last year.
>
> Regarding short latency with high accuracy: From my experience, the fastest latency with high accuracy rather depends on the quality of your TE probe than on the vario itself. There are significant differences in signal quality between different TE probes. Small latency is only needed while circling. In cruise mode you may want to have a longer latency in order not to be distracted with every single turbulence.

This is true when determining cruise speeds using S2F and related strategies, which I don't use. Since achieved XC velocities are relatively insensitive to precise cruise speed, a filtered average works well in S2F based methods. What I would like to find for what I am doing is something much faster during rapid transient events as a result of control inputs. Most of the modern varios claim "instantaneous" sensing but then something like "updated every second" which is very slow for my purposes.
>
> Regarding TE compensation: Both varios offer TE probe and electronic compensation along with some kind of air-mass filter which reduces signals from horizontal gusts in cruise mode. With the AirGlide, this filter is based on inertial sensors - not sure about the ClearNav. TE probe compensation with both varios works well while electronic compensation of static pressure signal did not work at all with both varios in my setup (LS8 with fuselage side static sources). With TE probe compensation on an esa DN/ST probe, I used a slight electronic adjustment of 2-3%. This gave perfect results.

I have a good TE probe. The instrument is the weak link in my system. Are the inertial sensors only used to provide delta adjustments of the horizontal components, or do some of them use inertial input for vertical variation. If so, is this giving faster, reliable indications that aren't filtered through a 1 second gate?
>
> The AirGlide offers a wide range of configuration option for the air mass filters and I am still working on the perfect setup. Seems that a longer integration time works better.
>
> My personal opinion on the topic on how to determine air mass information: It is not a matter of the sensors being used. Even older analog varios gave a signal quality comparable to AirGlide and CNv - specifically Zander 820D / 940 / ZS1 and Westerboer VW910 varios (I consider older LX types to be worse in that respect). It is rather about what conclusion the pilot draws out of the data being presented. A good user interface simplifies that.
>
> Best
> Christoph

Thanks again for your inputs, Christoph.

Gary

Hi Gary,

please find my comments below.


Am Donnerstag, 21. Juni 2018 15:44:19 UTC+2 schrieb :
> Hello Cristoph-
>
> Thanks for your thoughts and insights. Much appreciated. Some comments interspersed below.
>
> On Thursday, June 21, 2018 at 7:29:22 AM UTC-6, wrote:
> > Hi Gary,
> >
> > I have flown with both, ClearNav (500h) and AirGlide varios (100h). I also used both in parallel last season. In terms of variometry, both varios have a comparable performance. In fact, the readings in climb mode were almost identical. But I preferred the AirGlide user interface, wind calculation and physical quality of the product, so I sold the CNv last year.
> >
> > Regarding short latency with high accuracy: From my experience, the fastest latency with high accuracy rather depends on the quality of your TE probe than on the vario itself. There are significant differences in signal quality between different TE probes. Small latency is only needed while circling. In cruise mode you may want to have a longer latency in order not to be distracted with every single turbulence.
>
> This is true when determining cruise speeds using S2F and related strategies, which I don't use. Since achieved XC velocities are relatively insensitive to precise cruise speed, a filtered average works well in S2F based methods. What I would like to find for what I am doing is something much faster during rapid transient events as a result of control inputs. Most of the modern varios claim "instantaneous" sensing but then something like "updated every second" which is very slow for my purposes.

The varios are technically capable of very fast responses, but I don't consider this useful while cruising. I am rather trying to optimize my flight path such that I stay in lines of lift rather than sink. I don't stick to the proposed S2F but prefer the concept of block speeds. Adjustable audio deadbands help with that.

> >
> > Regarding TE compensation: Both varios offer TE probe and electronic compensation along with some kind of air-mass filter which reduces signals from horizontal gusts in cruise mode. With the AirGlide, this filter is based on inertial sensors - not sure about the ClearNav. TE probe compensation with both varios works well while electronic compensation of static pressure signal did not work at all with both varios in my setup (LS8 with fuselage side static sources). With TE probe compensation on an esa DN/ST probe, I used a slight electronic adjustment of 2-3%. This gave perfect results.
>
> I have a good TE probe. The instrument is the weak link in my system. Are the inertial sensors only used to provide delta adjustments of the horizontal components, or do some of them use inertial input for vertical variation. If so, is this giving faster, reliable indications that aren't filtered through a 1 second gate?

The AirGlide has this capability, as far as I know the CNv does not. It provides an air-mass indication (blue dot on the display) which can be configured independently from the vario reading. This air-mass info can be set up to be 100% inertially measured. You can also adjust it to very fast latency cycles, but so far I did not test this.

> >
> > The AirGlide offers a wide range of configuration option for the air mass filters and I am still working on the perfect setup. Seems that a longer integration time works better.
> >
> > My personal opinion on the topic on how to determine air mass information: It is not a matter of the sensors being used. Even older analog varios gave a signal quality comparable to AirGlide and CNv - specifically Zander 820D / 940 / ZS1 and Westerboer VW910 varios (I consider older LX types to be worse in that respect). It is rather about what conclusion the pilot draws out of the data being presented. A good user interface simplifies that.
> >
> > Best
> > Christoph
>
> Thanks again for your inputs, Christoph.
>
> Gary

On Thursday, June 21, 2018 at 1:23:46 PM UTC+1, wrote:
> Hi-
>
> I've searched the archives of this oft-discussed topic, but am not finding specific answers I'm seeking. If you have good experience or knowledge about the specific issues below, I would much appreciate your insights.
>
> 1) Latency with accuracy. What is the quickest vario with accuracy? Are they all limited by a 1 sec. latency with updates, or do some update faster? While several now describe their inputs as including both pressure sensor and inertial inputs from gyros and accelerometers, I can't find clarity on the mixture of these in the protocol. Some seem to link inertial inputs more to wind/track sensing than vario responses.
>
> 2) TE Compensation. Most all offer pneumatic or electronic, and at least some a gain loop on a pneumatic source so that compensation can be adjusted.. However, pneumatic comp alone will only be accurate for one condition (g loading, alpha delta, etc.) Whereas electronic gain loops have been around for decades, it seems rather archaic that modification of the input is limited to a single gain function. Does anyone provide modification to several points on a curve whether g loading, v, or another pertinent metric?
>
> I am looking at designing a new set of sensors and instruments that would display fundamentally different parameters for a type of flight strategies/optimization which is inertially based in a rapidly changing frame of reference. However, in the mean time I fly very dynamically and would appreciate experienced and accurate input about current vario offerings. I would also appreciate specific comments from pilots who have experience with both AirGlide (Butterfly), LxNav S8 or 80, and/or ClearNav Varios. Pluses and minuses wrt the above two capabilities in particular and notable general issues would be greatly appreciated.
>
> Thanks, and sorry for posting from my wife's account- I don't post often enough to remember my login commands and am away from home records. You can email me directly if you wish:
>
> Gary Osoba


At the last BGA conference I asked a technical guy from LX Nav how the inertial platform was used in the variometry of LX 8/9000 family of instruments and he said it was only used in the wind calculations.

On Thursday, June 21, 2018 at 5:23:46 AM UTC-7, wrote:
> Hi-
>
> I've searched the archives of this oft-discussed topic, but am not finding specific answers I'm seeking. If you have good experience or knowledge about the specific issues below, I would much appreciate your insights.
>
> 1) Latency with accuracy. What is the quickest vario with accuracy? Are they all limited by a 1 sec. latency with updates, or do some update faster? While several now describe their inputs as including both pressure sensor and inertial inputs from gyros and accelerometers, I can't find clarity on the mixture of these in the protocol. Some seem to link inertial inputs more to wind/track sensing than vario responses.
>
> 2) TE Compensation. Most all offer pneumatic or electronic, and at least some a gain loop on a pneumatic source so that compensation can be adjusted.. However, pneumatic comp alone will only be accurate for one condition (g loading, alpha delta, etc.) Whereas electronic gain loops have been around for decades, it seems rather archaic that modification of the input is limited to a single gain function. Does anyone provide modification to several points on a curve whether g loading, v, or another pertinent metric?
>
> I am looking at designing a new set of sensors and instruments that would display fundamentally different parameters for a type of flight strategies/optimization which is inertially based in a rapidly changing frame of reference. However, in the mean time I fly very dynamically and would appreciate experienced and accurate input about current vario offerings. I would also appreciate specific comments from pilots who have experience with both AirGlide (Butterfly), LxNav S8 or 80, and/or ClearNav Varios. Pluses and minuses wrt the above two capabilities in particular and notable general issues would be greatly appreciated.
>
> Thanks, and sorry for posting from my wife's account- I don't post often enough to remember my login commands and am away from home records. You can email me directly if you wish:
>
> Gary Osoba

As far as I can tell, the Air Vario is the only one using inertial sensors for variometry, represented in the Vertical Air Mass movement needle. This has a setting to be derived from any mix ratio of 100% barometric to 100% inertial. If set to 100% inertial I find it too twitchy, but set to 80% inertial it can be flown like a variometer, but leads it by a second or more. It is confused by other things, such as changing flap position. I can thermal with it even with the engine boom out, which totally hoses the tail pneumatics.

Every other vario since the 302 has had inertial sensors and some claimed to use them, but none seem to. Currently flying with both Air Vario and Clear Nav vario installed.

This seems like maybe a fair place to interject a relevant advertisment... Just yesterday I posted an ad on wingsandwheels.com for an Air Vario, Display S (Butterfly vario) in perfect condition for $1950. It's in the "Misc" category there.

Thank you. This is very helpful but it contradicts what an earlier poster stated. If it is adjustable as you have indicated, this is a very good feature.

Gary

> As far as I can tell, the Air Vario is the only one using inertial sensors for variometry, represented in the Vertical Air Mass movement needle. This has a setting to be derived from any mix ratio of 100% barometric to 100% inertial. If set to 100% inertial I find it too twitchy, but set to 80% inertial it can be flown like a variometer, but leads it by a second or more. It is confused by other things, such as changing flap position. I can thermal with it even with the engine boom out, which totally hoses the tail pneumatics.
>
> Every other vario since the 302 has had inertial sensors and some claimed to use them, but none seem to. Currently flying with both Air Vario and Clear Nav vario installed.

On Thursday, June 21, 2018 at 12:34:06 PM UTC-7, wrote:
> Thank you. This is very helpful but it contradicts what an earlier poster stated. If it is adjustable as you have indicated, this is a very good feature.
>
> Gary
>
> > As far as I can tell, the Air Vario is the only one using inertial sensors for variometry, represented in the Vertical Air Mass movement needle. This has a setting to be derived from any mix ratio of 100% barometric to 100% inertial. If set to 100% inertial I find it too twitchy, but set to 80% inertial it can be flown like a variometer, but leads it by a second or more. It is confused by other things, such as changing flap position. I can thermal with it even with the engine boom out, which totally hoses the tail pneumatics.
> >
> > Every other vario since the 302 has had inertial sensors and some claimed to use them, but none seem to. Currently flying with both Air Vario and Clear Nav vario installed.

I don't think is contradicts. The Air Vario draws several virtual needles on the screen, one is the variometer which is strictly barographic like others. The VAM needle (actually a blue ball) represents vertical air mass movement, and can be used like a variometer to a great extent. It is that reading that can be varied from barometric to inertial. You have both displayed at all times. The audio represents the barographic variometer needle (a triangular pointer). Both are useful - in theory the VAM does not react to horizontal gusts and leads the variometer. There are several adjustments to filtering on both to play with.

On Thursday, 21 June 2018 22:34:06 UTC+3, wrote:
> Thank you. This is very helpful but it contradicts what an earlier poster stated. If it is adjustable as you have indicated, this is a very good feature.
>
> Gary
>
> > As far as I can tell, the Air Vario is the only one using inertial sensors for variometry, represented in the Vertical Air Mass movement needle. This has a setting to be derived from any mix ratio of 100% barometric to 100% inertial. If set to 100% inertial I find it too twitchy, but set to 80% inertial it can be flown like a variometer, but leads it by a second or more. It is confused by other things, such as changing flap position. I can thermal with it even with the engine boom out, which totally hoses the tail pneumatics.
> >
> > Every other vario since the 302 has had inertial sensors and some claimed to use them, but none seem to. Currently flying with both Air Vario and Clear Nav vario installed.

Why not just read Air Glide S user manual, available online, to get all answers to your questions?

Read the manual? What kind of a man are you?

Boggs

Thanks jfitch- your comments are very helpful. I'm sorry if I gave the wrong impression- I thought someone had stated that none of the current offerings are using inertial inputs in the z dimension. Possibly someone wrote this to me privately. Your comments show that your vario has this capability as well as the ability to mix the inputs at different ratios. Clearly your experience with this is most helpful.

Gary

Thank for this good suggestion. Of course seeking advice from people with much good experience is golden, as manufacturer's manuals are not always accurate with instructions or claims. Empirical results from reliable sources can lead to better decision.

Thanks again,

Gary

krasw wrote on 6/22/2018 12:15 AM:
> On Thursday, 21 June 2018 22:34:06 UTC+3, wrote:
>> Thank you. This is very helpful but it contradicts what an earlier poster stated. If it is adjustable as you have indicated, this is a very good feature.
>>
>> Gary
>>
>>> As far as I can tell, the Air Vario is the only one using inertial sensors for variometry, represented in the Vertical Air Mass movement needle. This has a setting to be derived from any mix ratio of 100% barometric to 100% inertial. If set to 100% inertial I find it too twitchy, but set to 80% inertial it can be flown like a variometer, but leads it by a second or more. It is confused by other things, such as changing flap position. I can thermal with it even with the engine boom out, which totally hoses the tail pneumatics.
>>>
>>> Every other vario since the 302 has had inertial sensors and some claimed to use them, but none seem to. Currently flying with both Air Vario and Clear Nav vario installed.
>
> Why not just read Air Glide S user manual, available online, to get all answers to your questions?

Perhaps too late to be useful, but I've read the manual, and it just covers the
basics. Not much in there that Gary is seeking, or even a less advanced pilot.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

On Thursday, 21 June 2018 22:23:46 UTC+10, wrote:
> Hi-
>
> I've searched the archives of this oft-discussed topic, but am not finding specific answers I'm seeking. If you have good experience or knowledge about the specific issues below, I would much appreciate your insights.
>
> 1) Latency with accuracy. What is the quickest vario with accuracy? Are they all limited by a 1 sec. latency with updates, or do some update faster? While several now describe their inputs as including both pressure sensor and inertial inputs from gyros and accelerometers, I can't find clarity on the mixture of these in the protocol. Some seem to link inertial inputs more to wind/track sensing than vario responses.
>
> 2) TE Compensation. Most all offer pneumatic or electronic, and at least some a gain loop on a pneumatic source so that compensation can be adjusted.. However, pneumatic comp alone will only be accurate for one condition (g loading, alpha delta, etc.) Whereas electronic gain loops have been around for decades, it seems rather archaic that modification of the input is limited to a single gain function. Does anyone provide modification to several points on a curve whether g loading, v, or another pertinent metric?
>
> I am looking at designing a new set of sensors and instruments that would display fundamentally different parameters for a type of flight strategies/optimization which is inertially based in a rapidly changing frame of reference. However, in the mean time I fly very dynamically and would appreciate experienced and accurate input about current vario offerings. I would also appreciate specific comments from pilots who have experience with both AirGlide (Butterfly), LxNav S8 or 80, and/or ClearNav Varios. Pluses and minuses wrt the above two capabilities in particular and notable general issues would be greatly appreciated.
>
> Thanks, and sorry for posting from my wife's account- I don't post often enough to remember my login commands and am away from home records. You can email me directly if you wish:
>
> Gary Osoba

test

On Thursday, 21 June 2018 22:23:46 UTC+10, wrote:
> Hi-
>
> I've searched the archives of this oft-discussed topic, but am not finding specific answers I'm seeking. If you have good experience or knowledge about the specific issues below, I would much appreciate your insights.
------------
Charlie Quebec mentioned that I was developing such a unit called Dynamis.
It is actually done and entering production.
Immune to horizontal gusts, both long and short period. Also provides very accurate vector wind display updated once a second (averaged over much more frequent calculations. Currently flying in a Quintus here in Queensland. Will be re-installed in an ASH25 (the test vehicle) and LS8 and Nimbus 3DM within the next few weeks.

All pressure based instruments will suffer from much the same problems. It does not matter whether the TE compensation is by TE probe or derived from the pitot - static. TE probes are easier as pitot - static compensation introduces potential mismatches between the time the pressure signals arrive at the sensors and as you are subtracting two large signals to look at a small one it is easy to get large transient indications.There are also noticeable second order effects from changing G loads and angle of attack.
We did a nice little experiment by placing a blown up balloon over the end of a TE probe and recording the time constant of the pressure signal. Flasks or other capacities are bad news.

Eliminating horizontal gust effects is NOT a filtering problem as both real vertical motion of the air and horizontal gusts cause effects on the variometer of comparable time scales and magnitude. Because of these gusts, existing variometers cannot be made all that fast in response. A time constant of 2 to 3 seconds is what you end up with. Faster than this you will be averaging the pointer bouncing around by eye and this results in slower perception of changes and is work load intensive.

By eliminating sensitivity to horizontal gusts the variometer can respond more quickly to real vertical component changes in the air. During testing we were seeing more structure in the thermals because of this and lower workload by being able to rely on the indication instead of constantly trying to decide whether the change is due to a gust or real lift.
Dynamis works on principles not used before in variometers and is the end result of over 40 years of thinking, testing and experimentation.

No I'm not going to tell you how it is done. I've even managed to write the manual without revealing that. Sufficient that it works and works well.

Please do not reply to this gmail address. It NEVER gets checked. See our website for the correct one.

Mike Borgelt

Mike,

Congrats on the new gadget. It sounds great. Since you are here and talking about TE compensation, there is a dumb question that I've often wondered about.

In theory TE = MGH + 1/2MV**2

but ideally, should V be the plane speed vector with respect to the air or ground?

-Stu

On Tuesday, 28 August 2018 23:13:24 UTC+10, wrote:
> Mike,
>
> Congrats on the new gadget. It sounds great. Since you are here and talking about TE compensation, there is a dumb question that I've often wondered about.
>
> In theory TE = MGH + 1/2MV**2
>
> but ideally, should V be the plane speed vector with respect to the air or ground?
>
> -Stu

The air. But that isn't as simple as you might think.

More on Dynamis on our website. See the article "Horizontal Gusts" and under products - Dynamis Variometer System.

I'll put up some more articles and maybe comment under "blog" on the website over the next few days. Also pricing.

I'd like to get the next few local systems installed and test flown before release to the wider world.

Mike

On Wednesday, August 29, 2018 at 3:06:24 AM UTC+1, Mike Borgelt wrote:
> On Tuesday, 28 August 2018 23:13:24 UTC+10, wrote:
> > Mike,
> >
> > Congrats on the new gadget. It sounds great. Since you are here and talking about TE compensation, there is a dumb question that I've often wondered about.
> >
> > In theory TE = MGH + 1/2MV**2
> >
> > but ideally, should V be the plane speed vector with respect to the air or ground?
> >
> > -Stu
>
> The air. But that isn't as simple as you might think.
>
> More on Dynamis on our website. See the article "Horizontal Gusts" and under products - Dynamis Variometer System.
>
> I'll put up some more articles and maybe comment under "blog" on the website over the next few days. Also pricing.
>
> I'd like to get the next few local systems installed and test flown before release to the wider world.
>
> Mike

Hi Mike, would you consider putting the Dynamis user manual (or draft) on your website for practical information about fitment requirements etc?

On Tuesday, August 28, 2018 at 7:06:24 PM UTC-7, Mike Borgelt wrote:
> On Tuesday, 28 August 2018 23:13:24 UTC+10, wrote:
> > Mike,
> >
> > Congrats on the new gadget. It sounds great. Since you are here and talking about TE compensation, there is a dumb question that I've often wondered about.
> >
> > In theory TE = MGH + 1/2MV**2
> >
> > but ideally, should V be the plane speed vector with respect to the air or ground?
> >
> > -Stu
>
> The air. But that isn't as simple as you might think.
>
> More on Dynamis on our website. See the article "Horizontal Gusts" and under products - Dynamis Variometer System.
>
> I'll put up some more articles and maybe comment under "blog" on the website over the next few days. Also pricing.
>
> I'd like to get the next few local systems installed and test flown before release to the wider world.
>
> Mike

My guess is that you incorporated a vertical accelerometer (G meter) to differentiate between a lifting air mass and horizontal gusts (which don't produce vertical acceleration). I believe this has already been done in the Butterfly vario.

Tom

On Monday, September 3, 2018 at 5:11:28 PM UTC-7, 2G wrote:
> On Tuesday, August 28, 2018 at 7:06:24 PM UTC-7, Mike Borgelt wrote:
> > On Tuesday, 28 August 2018 23:13:24 UTC+10, wrote:
> > > Mike,
> > >
> > > Congrats on the new gadget. It sounds great. Since you are here and talking about TE compensation, there is a dumb question that I've often wondered about.
> > >
> > > In theory TE = MGH + 1/2MV**2
> > >
> > > but ideally, should V be the plane speed vector with respect to the air or ground?
> > >
> > > -Stu
> >
> > The air. But that isn't as simple as you might think.
> >
> > More on Dynamis on our website. See the article "Horizontal Gusts" and under products - Dynamis Variometer System.
> >
> > I'll put up some more articles and maybe comment under "blog" on the website over the next few days. Also pricing.
> >
> > I'd like to get the next few local systems installed and test flown before release to the wider world.
> >
> > Mike
>
> My guess is that you incorporated a vertical accelerometer (G meter) to differentiate between a lifting air mass and horizontal gusts (which don't produce vertical acceleration). I believe this has already been done in the Butterfly vario.
>
> Tom

Unfortunately horizontal gusts definitely do produce a vertical acceleration, since lift is 0.5 * d * Cl * V^2. Because of the V^2 term, they produce quite a lot of vertical acceleration. A 10 knot gust at 60 knots airspeed will give you near 0.4G acceleration.

Butterfly does seem to have worked this out first though.

Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.

Lots of fun with math.

On Tuesday, September 4, 2018 at 9:07:09 AM UTC-7, George Haeh wrote:
> Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.
>
> Lots of fun with math.

More holistically, you run a Kalman filter using every sensor you have and then some. You treat the system as having three disturbances: two horizontal wind components plus vertical flow. You continuously calculate a solution yielding least square error for the six DOF system with those disturbances being of primary interest.

On Tuesday, September 4, 2018 at 10:59:26 AM UTC-7, Steve Koerner wrote:
> On Tuesday, September 4, 2018 at 9:07:09 AM UTC-7, George Haeh wrote:
> > Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.
> >
> > Lots of fun with math.
>
> More holistically, you run a Kalman filter using every sensor you have and then some. You treat the system as having three disturbances: two horizontal wind components plus vertical flow. You continuously calculate a solution yielding least square error for the six DOF system with those disturbances being of primary interest.

Making a trip in the wayback machine to my control theory and aerodynamics classes - apologies if I mess up the details...

If you have a dynamic model for the glider (a Kalman filter would typically require this) you may also be able to use the difference between activating the short period and phugoid dynamic pitch modes with respect to pitch rate. This difference is why a strong thermal has that seat of the pants surge that pitches the nose down instead of up - as you'd get with a gust under normal circumstances.

For all of this you'd get a better result if you also knew the control positions and Cm vs control position - primarily for the elevator. Also, we don't really have dynamic models for gliders though my guess is it would not be that difficult to measure with a reasonably instrumented glider and a couple of test flights. You might be able to get decent results with a generic model for a reasonably current generation racing glider (for instance), though model-specific parameters would of course be better. You're really just trying to filter out the gusts so you may not need anything all that precise to get an improvement, just Cm vs alpha and Cm vs V. Knowing the c.g. and weight will matter as well, but you might be able to calculate these effects.

I wonder if it's easier or harder to use machine learning to do this than a more deterministic least squares model...or if all of the above is overkill.

Andy Blackburn
9B

On Tuesday, September 4, 2018 at 12:49:36 PM UTC-7, Andy Blackburn wrote:
> On Tuesday, September 4, 2018 at 10:59:26 AM UTC-7, Steve Koerner wrote:
> > On Tuesday, September 4, 2018 at 9:07:09 AM UTC-7, George Haeh wrote:
> > > Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.
> > >
> > > Lots of fun with math.
> >
> > More holistically, you run a Kalman filter using every sensor you have and then some. You treat the system as having three disturbances: two horizontal wind components plus vertical flow. You continuously calculate a solution yielding least square error for the six DOF system with those disturbances being of primary interest.
>
> Making a trip in the wayback machine to my control theory and aerodynamics classes - apologies if I mess up the details...
>
> If you have a dynamic model for the glider (a Kalman filter would typically require this) you may also be able to use the difference between activating the short period and phugoid dynamic pitch modes with respect to pitch rate. This difference is why a strong thermal has that seat of the pants surge that pitches the nose down instead of up - as you'd get with a gust under normal circumstances.
>
> For all of this you'd get a better result if you also knew the control positions and Cm vs control position - primarily for the elevator. Also, we don't really have dynamic models for gliders though my guess is it would not be that difficult to measure with a reasonably instrumented glider and a couple of test flights. You might be able to get decent results with a generic model for a reasonably current generation racing glider (for instance), though model-specific parameters would of course be better. You're really just trying to filter out the gusts so you may not need anything all that precise to get an improvement, just Cm vs alpha and Cm vs V. Knowing the c.g. and weight will matter as well, but you might be able to calculate these effects.
>
> I wonder if it's easier or harder to use machine learning to do this than a more deterministic least squares model...or if all of the above is overkill.
>
> Andy Blackburn
> 9B

I agree Andy; to do a Kalman filter you'd want gyros, accelerometers and control position sensors. Position sensors are not hard though and their mapping might be learned for each installation with a smooth air test flight. The problem with Neural network AI is that you have to begin the process with a comprehensive training set. Probably Mike Borgelt has a simpler and better way to get to just the goods that we care about without a plane load of sensors. I'll be looking forward to hearing more about this.

On Tuesday, September 4, 2018 at 2:40:05 PM UTC-7, Steve Koerner wrote:
> On Tuesday, September 4, 2018 at 12:49:36 PM UTC-7, Andy Blackburn wrote:
> > On Tuesday, September 4, 2018 at 10:59:26 AM UTC-7, Steve Koerner wrote:
> > > On Tuesday, September 4, 2018 at 9:07:09 AM UTC-7, George Haeh wrote:
> > > > Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.
> > > >
> > > > Lots of fun with math.
> > >
> > > More holistically, you run a Kalman filter using every sensor you have and then some. You treat the system as having three disturbances: two horizontal wind components plus vertical flow. You continuously calculate a solution yielding least square error for the six DOF system with those disturbances being of primary interest.
> >
> > Making a trip in the wayback machine to my control theory and aerodynamics classes - apologies if I mess up the details...
> >
> > If you have a dynamic model for the glider (a Kalman filter would typically require this) you may also be able to use the difference between activating the short period and phugoid dynamic pitch modes with respect to pitch rate. This difference is why a strong thermal has that seat of the pants surge that pitches the nose down instead of up - as you'd get with a gust under normal circumstances.
> >
> > For all of this you'd get a better result if you also knew the control positions and Cm vs control position - primarily for the elevator. Also, we don't really have dynamic models for gliders though my guess is it would not be that difficult to measure with a reasonably instrumented glider and a couple of test flights. You might be able to get decent results with a generic model for a reasonably current generation racing glider (for instance), though model-specific parameters would of course be better. You're really just trying to filter out the gusts so you may not need anything all that precise to get an improvement, just Cm vs alpha and Cm vs V. Knowing the c.g. and weight will matter as well, but you might be able to calculate these effects.
> >
> > I wonder if it's easier or harder to use machine learning to do this than a more deterministic least squares model...or if all of the above is overkill.
> >
> > Andy Blackburn
> > 9B
>
> I agree Andy; to do a Kalman filter you'd want gyros, accelerometers and control position sensors. Position sensors are not hard though and their mapping might be learned for each installation with a smooth air test flight.. The problem with Neural network AI is that you have to begin the process with a comprehensive training set. Probably Mike Borgelt has a simpler and better way to get to just the goods that we care about without a plane load of sensors. I'll be looking forward to hearing more about this.

What I know is I don't have a Kalman filter going in my head: but I do have a butt which feels vertical acceleration. If it doesn't tell me I am going up, I discount the screaming vario.

Tom

On Wednesday, September 5, 2018 at 1:22:14 AM UTC-4, 2G wrote:
> On Tuesday, September 4, 2018 at 2:40:05 PM UTC-7, Steve Koerner wrote:
> > On Tuesday, September 4, 2018 at 12:49:36 PM UTC-7, Andy Blackburn wrote:
> > > On Tuesday, September 4, 2018 at 10:59:26 AM UTC-7, Steve Koerner wrote:
> > > > On Tuesday, September 4, 2018 at 9:07:09 AM UTC-7, George Haeh wrote:
> > > > > Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.
> > > > >
> > > > > Lots of fun with math.
> > > >
> > > > More holistically, you run a Kalman filter using every sensor you have and then some. You treat the system as having three disturbances: two horizontal wind components plus vertical flow. You continuously calculate a solution yielding least square error for the six DOF system with those disturbances being of primary interest.
> > >
> > > Making a trip in the wayback machine to my control theory and aerodynamics classes - apologies if I mess up the details...
> > >
> > > If you have a dynamic model for the glider (a Kalman filter would typically require this) you may also be able to use the difference between activating the short period and phugoid dynamic pitch modes with respect to pitch rate. This difference is why a strong thermal has that seat of the pants surge that pitches the nose down instead of up - as you'd get with a gust under normal circumstances.
> > >
> > > For all of this you'd get a better result if you also knew the control positions and Cm vs control position - primarily for the elevator. Also, we don't really have dynamic models for gliders though my guess is it would not be that difficult to measure with a reasonably instrumented glider and a couple of test flights. You might be able to get decent results with a generic model for a reasonably current generation racing glider (for instance), though model-specific parameters would of course be better. You're really just trying to filter out the gusts so you may not need anything all that precise to get an improvement, just Cm vs alpha and Cm vs V. Knowing the c.g. and weight will matter as well, but you might be able to calculate these effects.
> > >
> > > I wonder if it's easier or harder to use machine learning to do this than a more deterministic least squares model...or if all of the above is overkill.
> > >
> > > Andy Blackburn
> > > 9B
> >
> > I agree Andy; to do a Kalman filter you'd want gyros, accelerometers and control position sensors. Position sensors are not hard though and their mapping might be learned for each installation with a smooth air test flight. The problem with Neural network AI is that you have to begin the process with a comprehensive training set. Probably Mike Borgelt has a simpler and better way to get to just the goods that we care about without a plane load of sensors. I'll be looking forward to hearing more about this.
>
> What I know is I don't have a Kalman filter going in my head: but I do have a butt which feels vertical acceleration. If it doesn't tell me I am going up, I discount the screaming vario.
>
> Tom

What I "think" I've learned is that each day the thermals have a feel to them that takes attention to notice and adjust to. That feel also changes during the day. Variables include airmass vertical motion, the way mixing happens with altitude, horizontal gusts, vertical gusts, thermal size,and gradient within the thermal. This seems like a lot of variables to try to roll into a solution.
Horizontal gusts are a big complication and filtering obviously could help many pilots. That said, those gusts are also useful to know what may be coming.
It will be interesting to see what Mike has developed.
UH

keskiviikko 5. syyskuuta 2018 8.22.14 UTC+3 2G kirjoitti:
>
> What I know is I don't have a Kalman filter going in my head: but I do have a butt which feels vertical acceleration. If it doesn't tell me I am going up, I discount the screaming vario.
>
> Tom

The wing transforms horizontal gust into vertical, and your butt gets it wrong.

On Wednesday, September 5, 2018 at 9:20:53 AM UTC-5, krasw wrote:
> keskiviikko 5. syyskuuta 2018 8.22.14 UTC+3 2G kirjoitti:
> >
> > What I know is I don't have a Kalman filter going in my head: but I do have a butt which feels vertical acceleration. If it doesn't tell me I am going up, I discount the screaming vario.
> >
> > Tom
>
> The wing transforms horizontal gust into vertical, and your butt gets it wrong.

That's true if you only use your butt and not you're inner ear to sense the pitch rotation. A horizontal gust on the nose excites the phugoid (dCm/dV) and pitches the nose up. Vertical air movement excites the short period (dCm/dalpha) and pitches the nose down. A thermal you can climb in is likely to produce a more prolonged surge than a vertical gust. The exact magnitude of these effects depend on the specific aircraft aerodynamics and things like cg location.

Tom, you may not have a Kalman filter in your head, but you are a neural network - kind of by definition since your brain is made of connected neurons.. Pattern recognition is how we all interpret the "feel" of thermals. It helps a little if you can decompose some of the bigger dynamic effects, but there's a lot going on with lift, gusts and aircraft dynamics - as UH points out. I think a smart vario ought to be able to sort out some of these dynamic interactions better than simple total energy compensation. I figure with cheap gyros and accelerometers they would be doing a lot of this already, but I don't know how far it's gotten.

Again, apologies if I didn't completely accurately describe the engineering of aircraft dynamics. I think this is roughly correct.

Andy
9B

Andy Blackburn wrote on 9/5/2018 9:44 AM:
> On Wednesday, September 5, 2018 at 9:20:53 AM UTC-5, krasw wrote:
>> keskiviikko 5. syyskuuta 2018 8.22.14 UTC+3 2G kirjoitti:
>>>
>>> What I know is I don't have a Kalman filter going in my head: but I do have a butt which feels vertical acceleration. If it doesn't tell me I am going up, I discount the screaming vario.
>>>
>>> Tom
>>
>> The wing transforms horizontal gust into vertical, and your butt gets it wrong.
>
> That's true if you only use your butt and not you're inner ear to sense the pitch rotation. A horizontal gust on the nose excites the phugoid (dCm/dV) and pitches the nose up. Vertical air movement excites the short period (dCm/dalpha) and pitches the nose down. A thermal you can climb in is likely to produce a more prolonged surge than a vertical gust. The exact magnitude of these effects depend on the specific aircraft aerodynamics and things like cg location.
>
> Tom, you may not have a Kalman filter in your head, but you are a neural network - kind of by definition since your brain is made of connected neurons.. Pattern recognition is how we all interpret the "feel" of thermals. It helps a little if you can decompose some of the bigger dynamic effects, but there's a lot going on with lift, gusts and aircraft dynamics - as UH points out. I think a smart vario ought to be able to sort out some of these dynamic interactions better than simple total energy compensation. I figure with cheap gyros and accelerometers they would be doing a lot of this already, but I don't know how far it's gotten.
>
> Again, apologies if I didn't completely accurately describe the engineering of aircraft dynamics. I think this is roughly correct.

I'm thinking a horizontal gust on the nose is similar to a higher airspeed, and
with the glider elevator set for the lower airspeed, a pitch-up would occur.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

On Wed, 05 Sep 2018 15:21:11 -0700, Eric Greenwell wrote:

> Andy Blackburn wrote on 9/5/2018 9:44 AM:
>> On Wednesday, September 5, 2018 at 9:20:53 AM UTC-5, krasw wrote:
>>> keskiviikko 5. syyskuuta 2018 8.22.14 UTC+3 2G kirjoitti:
>>>>
>>>> What I know is I don't have a Kalman filter going in my head: but I
>>>> do have a butt which feels vertical acceleration. If it doesn't tell
>>>> me I am going up, I discount the screaming vario.
>>>>
>>>> Tom
>>>
>>> The wing transforms horizontal gust into vertical, and your butt gets
>>> it wrong.
>>
>> That's true if you only use your butt and not you're inner ear to sense
>> the pitch rotation. A horizontal gust on the nose excites the phugoid
>> (dCm/dV) and pitches the nose up. Vertical air movement excites the
>> short period (dCm/dalpha) and pitches the nose down. A thermal you can
>> climb in is likely to produce a more prolonged surge than a vertical
>> gust. The exact magnitude of these effects depend on the specific
>> aircraft aerodynamics and things like cg location.
>>
>> Tom, you may not have a Kalman filter in your head, but you are a
>> neural network - kind of by definition since your brain is made of
>> connected neurons.. Pattern recognition is how we all interpret the
>> "feel" of thermals. It helps a little if you can decompose some of the
>> bigger dynamic effects, but there's a lot going on with lift, gusts and
>> aircraft dynamics - as UH points out. I think a smart vario ought to be
>> able to sort out some of these dynamic interactions better than simple
>> total energy compensation. I figure with cheap gyros and accelerometers
>> they would be doing a lot of this already, but I don't know how far
>> it's gotten.
>>
>> Again, apologies if I didn't completely accurately describe the
>> engineering of aircraft dynamics. I think this is roughly correct.
>
> I'm thinking a horizontal gust on the nose is similar to a higher
> airspeed, and with the glider elevator set for the lower airspeed, a
> pitch-up would occur.

Isn't this countered as a glider enters a thermal because it is flying
into air with increasing vertical velocity? This will tend to lower the
effective AOA, causing the glider to accelerate forward as it tries to
return to its trimmed AOA. Hence its pilot 'feeling the surge' forward
and up.

In the past I've seen free flight competition models do this too, some
(the APS Aiglet A/1 design) would sometimes pitch down very obviously
when entering a thermal, while many/most designs can look as if they're
being sucked into a strong thermal, though with not so much visible pitch
change as the old Aiglet used to show.


--
Martin | martin at
Gregorie | gregorie dot org

Martin Gregorie wrote on 9/5/2018 4:35 PM:
> On Wed, 05 Sep 2018 15:21:11 -0700, Eric Greenwell wrote:
>

>>>
>>> That's true if you only use your butt and not you're inner ear to sense the
>>> pitch rotation. A horizontal gust on the nose excites the phugoid (dCm/dV)
>>> and pitches the nose up. Vertical air movement excites the short period
>>> (dCm/dalpha) and pitches the nose down. A thermal you can climb in is
>>> likely to produce a more prolonged surge than a vertical gust. The exact
>>> magnitude of these effects depend on the specific aircraft aerodynamics and
>>> things like cg location.
....
>> I'm thinking a horizontal gust on the nose is similar to a higher airspeed,
>> and with the glider elevator set for the lower airspeed, a pitch-up would
>> occur.
>
> Isn't this countered as a glider enters a thermal because it is flying into air
> with increasing vertical velocity? This will tend to lower the effective AOA,
> causing the glider to accelerate forward as it tries to return to its trimmed
> AOA. Hence its pilot 'feeling the surge' forward and up.
>
> In the past I've seen free flight competition models do this too, some (the APS
> Aiglet A/1 design) would sometimes pitch down very obviously when entering a
> thermal, while many/most designs can look as if they're being sucked into a
> strong thermal, though with not so much visible pitch change as the old Aiglet
> used to show.

My context, and I think Andy's, was encountering just a horizontal gust. I do
think encountering a vertical gust would cause a momentary nose-down attitude change.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

On Wednesday, September 5, 2018 at 10:09:03 PM UTC-5, Eric Greenwell wrote:
> Martin Gregorie wrote on 9/5/2018 4:35 PM:
> > On Wed, 05 Sep 2018 15:21:11 -0700, Eric Greenwell wrote:
> >
>
> >>>
> >>> That's true if you only use your butt and not you're inner ear to sense the
> >>> pitch rotation. A horizontal gust on the nose excites the phugoid (dCm/dV)
> >>> and pitches the nose up. Vertical air movement excites the short period
> >>> (dCm/dalpha) and pitches the nose down. A thermal you can climb in is
> >>> likely to produce a more prolonged surge than a vertical gust. The exact
> >>> magnitude of these effects depend on the specific aircraft aerodynamics and
> >>> things like cg location.
> ...
> >> I'm thinking a horizontal gust on the nose is similar to a higher airspeed,
> >> and with the glider elevator set for the lower airspeed, a pitch-up would
> >> occur.
> >
> > Isn't this countered as a glider enters a thermal because it is flying into air
> > with increasing vertical velocity? This will tend to lower the effective AOA,
> > causing the glider to accelerate forward as it tries to return to its trimmed
> > AOA. Hence its pilot 'feeling the surge' forward and up.
> >
> > In the past I've seen free flight competition models do this too, some (the APS
> > Aiglet A/1 design) would sometimes pitch down very obviously when entering a
> > thermal, while many/most designs can look as if they're being sucked into a
> > strong thermal, though with not so much visible pitch change as the old Aiglet
> > used to show.
>
> My context, and I think Andy's, was encountering just a horizontal gust. I do
> think encountering a vertical gust would cause a momentary nose-down attitude change.
>
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> - "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm
>
> http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

Yes. That's the difference between a horizontal and vertical gust (reminder: a sustained vertical gust is a thermal). A horizontal gust activates the dCm/dV (phugoid) mode that is nose-up because the center of lift is in front of the center of gravity. A vertical gust activates the dCm/dalpha (short period) mode which is nose down for most airfoils (in addition to vertical acceleration from the air movement itself).

Also, these two modes have different time constants by roughly a factor of 10 (they are also coupled, but over the first few seconds this doesn't come into play). So the vertical acceleration and pitch response together ought to be different for a horizontal gust versus a thermal.

Andy Blackburn
9B

On Wednesday, 5 September 2018 15:22:14 UTC+10, 2G wrote:
> On Tuesday, September 4, 2018 at 2:40:05 PM UTC-7, Steve Koerner wrote:
> > On Tuesday, September 4, 2018 at 12:49:36 PM UTC-7, Andy Blackburn wrote:
> > > On Tuesday, September 4, 2018 at 10:59:26 AM UTC-7, Steve Koerner wrote:
> > > > On Tuesday, September 4, 2018 at 9:07:09 AM UTC-7, George Haeh wrote:
> > > > > Lift from horizontal gusts can be filtered out with rates of dynamic pressure and attitude, perhaps with application of polar.
> > > > >
> > > > > Lots of fun with math.
> > > >
> > > > More holistically, you run a Kalman filter using every sensor you have and then some. You treat the system as having three disturbances: two horizontal wind components plus vertical flow. You continuously calculate a solution yielding least square error for the six DOF system with those disturbances being of primary interest.
> > >
> > > Making a trip in the wayback machine to my control theory and aerodynamics classes - apologies if I mess up the details...
> > >
> > > If you have a dynamic model for the glider (a Kalman filter would typically require this) you may also be able to use the difference between activating the short period and phugoid dynamic pitch modes with respect to pitch rate. This difference is why a strong thermal has that seat of the pants surge that pitches the nose down instead of up - as you'd get with a gust under normal circumstances.
> > >
> > > For all of this you'd get a better result if you also knew the control positions and Cm vs control position - primarily for the elevator. Also, we don't really have dynamic models for gliders though my guess is it would not be that difficult to measure with a reasonably instrumented glider and a couple of test flights. You might be able to get decent results with a generic model for a reasonably current generation racing glider (for instance), though model-specific parameters would of course be better. You're really just trying to filter out the gusts so you may not need anything all that precise to get an improvement, just Cm vs alpha and Cm vs V. Knowing the c.g. and weight will matter as well, but you might be able to calculate these effects.
> > >
> > > I wonder if it's easier or harder to use machine learning to do this than a more deterministic least squares model...or if all of the above is overkill.
> > >
> > > Andy Blackburn
> > > 9B
> >
> > I agree Andy; to do a Kalman filter you'd want gyros, accelerometers and control position sensors. Position sensors are not hard though and their mapping might be learned for each installation with a smooth air test flight. The problem with Neural network AI is that you have to begin the process with a comprehensive training set. Probably Mike Borgelt has a simpler and better way to get to just the goods that we care about without a plane load of sensors. I'll be looking forward to hearing more about this.
>
> What I know is I don't have a Kalman filter going in my head: but I do have a butt which feels vertical acceleration. If it doesn't tell me I am going up, I discount the screaming vario.
>
> Tom

Actually what you have going on in your head is a pretty good stab at a Kalman filter. You are weighting the vario reading vs your backside and other cues to arrive at what you think is happening. It is workload intensive and all too often fails.

Those talking about about the effects of gusts should read my horizontal gust article on the website.
Very small horizontal velocity gradients cause large signals on a normal TE variometer. I give some examples there. The effect depends on the square of the True Air Speed so in South Africa, Australia and the western US where you may be at high altitude and cruising at 100KIAS + your TAS can be in the 120 to 140 KTAS range.
It is just as well gliders don't cruise at 200KTAS because the normal TE vario would be uselessly and apparently randomly moving between the stops.

When a glider enters a thermal the air coming from below changes the direction of the relative wind which increases the angle of attack which increases the lift and the glider starts going up. On entering strong thermals pitch stability of the glider will tend to maintain the trimmed AoA, hence the glider will tend to pitch nose down. The effect is short lived as the time constant of the response to vertical air changes is short. It depends on airspeed, wing loading and the slope of the lift curve of the wing. With modern gliders it is around 0.4 to 0.5 seconds at low speeds and around 0.2 to 0.25 seconds at high speeds.
I had to derive this and I later found the derivation in a book called "Airplane Response to Atmospheric Turbulence" by John C. Houbolt. Yep, that guy - the one who pushed the Lunar Orbit Rendevous for Apollo.
Now the tendency of a airplane to pitch nose down on entering rising air (which can momentarily stall the airplane if the lift is strong enough) can be a really GREAT way to kill yourself because as nearly everyone has been taught to fly attitude your first reaction is to pull the stick back to maintain the attitude. If the wing was stalled or nearly so you are now stalling or pulling deeper in to the stall. Do this while turning final with what looks like adequate airspeed and you could find yourself on the ground short of the runway wondering what just happened if you live through it. The same of course applies to thermalling at low altitude. Remember the stick controls angle of attack and in very short term vertical velocity changes in the atmosphere also change AoA. Anything else it apparently does is a consequence of the angle of attack change.

Mike Borgelt

Borgelt Instruments

Mike,

I understand that the short period response to a step function in vertical air motion would damp out after less than a second, but normally thermal entry would have a positive gradient in vertical air motion as the glider traverses from zero vertical motion to maximum vertical motion towards the center of the thermal. This ought to create a more prolonged nose-down pitch attitude in addition to upward acceleration, both of which ought to be detectable to accelerometers and gyros in a modern vario. This would be quite distinct from an ever-so-slow negative acceleration and nose up pitch rate from a horizontal gust on the nose. I expect having a sense for the distribution of strength and duration for horizontal gusts would also help a bit.

That’s what I tend to sense in moderate to strong thermals versus gusts. Is that that a correct interpretation?

Andy

On Friday, 7 September 2018 09:23:31 UTC+10, Andy Blackburn wrote:
> Mike,
>
> I understand that the short period response to a step function in vertical air motion would damp out after less than a second, but normally thermal entry would have a positive gradient in vertical air motion as the glider traverses from zero vertical motion to maximum vertical motion towards the center of the thermal. This ought to create a more prolonged nose-down pitch attitude in addition to upward acceleration, both of which ought to be detectable to accelerometers and gyros in a modern vario. This would be quite distinct from an ever-so-slow negative acceleration and nose up pitch rate from a horizontal gust on the nose. I expect having a sense for the distribution of strength and duration for horizontal gusts would also help a bit.
>
> That’s what I tend to sense in moderate to strong thermals versus gusts. Is that that a correct interpretation?
>
> Andy

Andy, that's basically right. The horizontal gust is usually so small though that I've never detected any nose up effect from the horizontal gusts. i.e. a one knot airspeed increase over one second at 100 KTAS will show 5 knots up on the TE vario. My experience has been that a lot of the time the vertical air motion is fairly sharp edged but some times you fly straight in to a strong core over a few seconds and it feels like the tail is being lifted. What is happening is the glider trying to line up with the new relative wind direction and during this time you have increased AoA happening. Trying to hold a constant nose attitude will increase the AoA further.

To digress from the vario topic slightly:
Which is why I said that flying attitude can kill you. I think this is what happened to an ASG-29 pilot at Waikerie about 2 and a half years ago, turning final with what seemed to be plenty of airspeed, into a strong thermal encounter and the next thing he was in the grapevines. Fortunately the wires and vines cushioned the stop enough and the spin wasn't fully established, that he survived. Encounter a fairly sharp 10 knot core at 60 KIAS and the AoA increases by 10 degrees. The AoA may be around 7 degrees before the encounter. What AoA do thin subsonic wings stall at?
This, I believe is one answer to the unexplained spin ins that occur from time to time.
Attitude is fine in equilibrium or very close to equilibrium situations. Doesn't work very well in other situations. How many have died in the winch launch failure scenario where you bury the nose well below the horizon, then roll and pull and the thing flicks in to a spin? Unfortunately all too many merely in practice.
A guy who was Chief Test Pilot for the Royal Australian Air Force during the 1950s and 1960s once told me if the aircraft is wanting to go a certain way and you are trying to force it to go another, just go with the aircraft as it is departing from controlled flight. Good advice IMO.

....and to paraphrase what it says in Stick and Rudder - if *anything* surprising happens in a turn then immediately unload the wing.

This has turned into a very interesting thread. It looks like we may be using some newer much better varios in the near future.
Another interesting aspect is Mike Borgelt describing the AOA change and the possible cause of low level, low speed [ in the pattern] accidents.
When were up high cruising at 80-100 knots we fly into 10 knots up all the time and pull hard to slow down and get ready to circle. Up high at speed this is no problem. Down low and slow at say 60 knots that 10 knot thermal you just hit may cause a major problem. I think we may be flying way to slow in the pattern. Looking at the stall/spin rates, in all parts of the arrival pattern, I might be right.
I like using the Knauff idea of having a longer higher final leg, and as my max flap extension speed in my LS3a is 86 knots, I try to keep it over 70 knots the whole way to the deck, works for me. This may sound fast and it is. I don't want to stall close to the ground by some rouge air or a booming thermal.
This fast in the pattern stuff was taught to me by Bob Faris CFIG
So far so good!

On Friday, September 7, 2018 at 9:08:28 AM UTC-4, Nick Kennedy wrote:
> This has turned into a very interesting thread. It looks like we may be using some newer much better varios in the near future.


There are freaking astoundingly good varios available right now. Mike may have made a break through, good for all of us if true. I have an arm's length association with ClearNav and I can tell you that a) we're not out of good ideas and b) nothing I'd like better to have than a fire lit under the development team to get some of these ideas brought to fruition.

Caveat: installation is everything. Bad pneumatic sources, leaks, shared sources with mechanical instruments can/will degrade performance.

best,
Evan Ludeman

Me, too!Â* The maximum speed with the gear down in the Stemme is 76
knots.Â* I keep the speed very close to that number throughout the
pattern, slowing on final as the target point is made.Â* I also have very
effective dive brakes and so I keep the pattern in close.Â* I cringe when
I see a glider fly a half mile final at 50 kts or less. Sure, he's got
the glide ratio to make the runway easily, until that unexpected gust
comes along...

On 9/7/2018 7:08 AM, Nick Kennedy wrote:
> I try to keep it over 70 knots the whole way to the deck, works for me.

--
Dan, 5J

On 9/6/2018 7:21 PM, Mike Borgelt wrote:
> if the aircraft is wanting to go a certain way and you are trying to force it to go another, just go with the aircraft as it is departing from controlled flight. Good advice IMO.
Exactly!Â* I had an incident two years ago while attempting to establish
in the wave in the lee of a mountain at about 2,500' AGL. The glider
suddenly rolled to the right and pitched down though I was well above
stall speed (and I understand AoA).Â* My response was to immediately
center the ailerons and add plenty of forward stick until the glider
flew out of the departure.Â* Of course I missed the wave that day...
--
Dan, 5J

On Thursday, September 6, 2018 at 7:23:31 PM UTC-4, Andy Blackburn wrote:
> Mike,
>
> I understand that the short period response to a step function in vertical air motion would damp out after less than a second, but normally thermal entry would have a positive gradient in vertical air motion as the glider traverses from zero vertical motion to maximum vertical motion towards the center of the thermal. This ought to create a more prolonged nose-down pitch attitude in addition to upward acceleration, both of which ought to be detectable to accelerometers and gyros in a modern vario. This would be quite distinct from an ever-so-slow negative acceleration and nose up pitch rate from a horizontal gust on the nose. I expect having a sense for the distribution of strength and duration for horizontal gusts would also help a bit.
>
> That’s what I tend to sense in moderate to strong thermals versus gusts. Is that that a correct interpretation?
>
> Andy

I recently took a "refresher"course of four days with a truly outstanding professional mountain soaring pilot. Interestingly, he does not detect and select thermals by using the vario. He states that the vario gives old information that has long past. Intead, he trusts his "butt" and for a visual reference notices the nose of the glider pitching upwards. We seldom missed a true thermal. When a glider enters sink )as when leaving a strong thermal), the nose pitches upwards initially.

On Thursday, September 6, 2018 at 8:21:39 PM UTC-5, Mike Borgelt wrote:

> To digress from the vario topic slightly:
> Which is why I said that flying attitude can kill you. I think this is what happened to an ASG-29 pilot at Waikerie about 2 and a half years ago, turning final with what seemed to be plenty of airspeed, into a strong thermal encounter and the next thing he was in the grapevines. Fortunately the wires and vines cushioned the stop enough and the spin wasn't fully established, that he survived. Encounter a fairly sharp 10 knot core at 60 KIAS and the AoA increases by 10 degrees. The AoA may be around 7 degrees before the encounter. What AoA do thin subsonic wings stall at?
> This, I believe is one answer to the unexplained spin ins that occur from time to time.
> Attitude is fine in equilibrium or very close to equilibrium situations. Doesn't work very well in other situations. How many have died in the winch launch failure scenario where you bury the nose well below the horizon, then roll and pull and the thing flicks in to a spin? Unfortunately all too many merely in practice.
> A guy who was Chief Test Pilot for the Royal Australian Air Force during the 1950s and 1960s once told me if the aircraft is wanting to go a certain way and you are trying to force it to go another, just go with the aircraft as it is departing from controlled flight. Good advice IMO.

To continue this excellent digression from the original thread: This whole "pitchdown in the pattern due to a thermal" is the reason we should be using AOA in the pattern instead of Airspeed. An AOA gauge would immediately indicate the AOA changing due to a gust or thermal - before the ASI shows any change in airspeed. Couple the AOA system with a visual (or even better, an aural) indication, and you can fly the pattern safely without ever looking in the cockpit.

Caution, war story: The F-4 had a really nice AOA system with both visual (cockpit gauge and coaming AOA lights) and aural cues, that worked much like a vario audio, with different tones from fast down to on-speed and down to slow and dangerously slow. Very distinct tones which made it easy to fly the pattern at a nice safe speed (regardless of gross weight or bank angle) until on final, then slowing down to final on-speed for touch down - never looking at the airspeed indicator other than to cross check AOA vs airspeed at the start of the approach. Flying approaches from the back seat, you couldn't even see the airspeed indicator (due to having to lean way over and look around the pilot's seat - a crosswind or a bit of rudder helped ;^) so you relied entirely on the AOA tones to fly the approach - and it was the easiest, most natural thing to do, keeping the touchdown point in view the whole time.

Here is an idea for you smart guys: come up with a simple AOA sensor system consisting of small low drag bluetooth-enabled "pods" attached about mid-span on both wing leading edges, transmitting to the AOA system in the cockpit. When the gear is down (and/or spoilers open for fixed gear ships) the vario audio would be turned off and replaced by the AOA audio (which would be distinctive enough not to be confused with a vario), backed up with a set of FAST/ONSPEED/SLOW indexer lights on the top of the panel. To use, in the pattern drop gear or crack the spoilers, verify the AOA tone matches your approach speed on downwind (to check for stuck or failing AOA system), then fly the audio to touchdown, looking for a fast or slightly fast tone until short final when you slow to on-speed tone. If you hit a gust or thermal that bumps up your AOA dangerously, you would get an immediate SLOW or DANGEROUSLY SLOW tone and could react accordingly. Same if you have a PTT down low full of ballast and have to turn back to the field - the AOA tones would still be correct for your increased bank angle and wingloading.

Kirk
66

Mike Borgelt wrote on 9/5/2018 10:11 PM:
> I had to derive this and I later found the derivation in a book called
> "Airplane Response to Atmospheric Turbulence" by John C. Houbolt. Yep, that guy
> - the one who pushed the Lunar Orbit Rendevous for Apollo.

Thank you for that reference. I had never heard of the struggle between three
methods of making it to the moon - and back. Fascinating!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

On Saturday, September 8, 2018 at 1:13:39 PM UTC-7, Eric Greenwell wrote:
> Mike Borgelt wrote on 9/5/2018 10:11 PM:
> > I had to derive this and I later found the derivation in a book called
> > "Airplane Response to Atmospheric Turbulence" by John C. Houbolt. Yep, that guy
> > - the one who pushed the Lunar Orbit Rendevous for Apollo.
>
> Thank you for that reference. I had never heard of the struggle between three
> methods of making it to the moon - and back. Fascinating!
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> - "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm
>
> http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

Watch "From the Earth to the Moon".

AOA devices are becoming very common in the experimental/homebuilt airplane world. A recent publication from the FAA (!) recommended that pilots consider getting a AOA sensor installed in their airplane. The newer completed aircraft in the famous Vans Aircraft RV series are almost all equipped with a AOA device.

I have been investigating a AOA system to install in gliders for several years but keep running into challenges due to flaps and spoilers and their effect on the system. The whole device is very easy if the airflow and overall AOA doesn't change much with configuration changes.

One fix is to set the system primarily for landing and disable it for other flight regimes. Unfortunately that means you can't use the best L/D AOA, or other selected angles to correct for weight changes.

I also have a Raspberry Pi and considered just starting to log the data for my glider. This winter I'm doing a refinish; maybe that a good time to install the pressure sensors and start logging.

Mike

Here is one that was published years ago, but it is NOT a AOA device but rather a pitch angle measurement. Close but not quite:

http://www.akaflieg.tugraz.at/wp-content/uploads/2013/04/simple-diy-aoa-sensor_v1.pdf

Here is a good discussion on the devices being used in the airplane world:

https://www.flyingmag.com/how-it-works-angle-attack-indicator

Another discussion particularly directed at gliders:

https://www.dg-flugzeugbau.de/en/library/side-string
This one shows some of the chanllenges for the glider version of an AOA indicator. The string method shown is still not a true AOA for the wing, and requires the pilot to be looking to the side to "read" the string.

Finally a former thread on RAS, this particular statement by Ian describes the challenges well:

https://groups.google.com/forum/#!msg/rec.aviation.soaring/v_FVcLjkBuE/14QLGAt2_9UJ

Mike

On Saturday, September 8, 2018 at 7:14:46 PM UTC-5, SoaringXCellence wrote:
> AOA devices are becoming very common in the experimental/homebuilt airplane world. A recent publication from the FAA (!) recommended that pilots consider getting a AOA sensor installed in their airplane. The newer completed aircraft in the famous Vans Aircraft RV series are almost all equipped with a AOA device.
>
> I have been investigating a AOA system to install in gliders for several years but keep running into challenges due to flaps and spoilers and their effect on the system. The whole device is very easy if the airflow and overall AOA doesn't change much with configuration changes.
>
> One fix is to set the system primarily for landing and disable it for other flight regimes. Unfortunately that means you can't use the best L/D AOA, or other selected angles to correct for weight changes.
>
> I also have a Raspberry Pi and considered just starting to log the data for my glider. This winter I'm doing a refinish; maybe that a good time to install the pressure sensors and start logging.
>
> Mike

In the SZD55-1 Flight manual,

http://org.ntnu.no/nthf/dokument/flight_manuals/LN-GAZ.pdf

p. 12a, it says that "For airworthiness the JAR-22 require the sailplane to be equipped at least with: airspeed indicator, altimeter and STALL WARNING DEVICE." I can remember there was some kind of a buzzer on the SZD-55 I used to own for a short time, but I never heard it sound nor don't know how it was supposed to work.


Any other SZD-55 owners/pilots here?

Sounds like a great idea.Â* Maybe you could use a micro switch in the
landing flap position to change the mode of your AoA device.

On 9/8/2018 6:14 PM, SoaringXCellence wrote:
> AOA devices are becoming very common in the experimental/homebuilt airplane world. A recent publication from the FAA (!) recommended that pilots consider getting a AOA sensor installed in their airplane. The newer completed aircraft in the famous Vans Aircraft RV series are almost all equipped with a AOA device.
>
> I have been investigating a AOA system to install in gliders for several years but keep running into challenges due to flaps and spoilers and their effect on the system. The whole device is very easy if the airflow and overall AOA doesn't change much with configuration changes.
>
> One fix is to set the system primarily for landing and disable it for other flight regimes. Unfortunately that means you can't use the best L/D AOA, or other selected angles to correct for weight changes.
>
> I also have a Raspberry Pi and considered just starting to log the data for my glider. This winter I'm doing a refinish; maybe that a good time to install the pressure sensors and start logging.
>
> Mike

--
Dan, 5J

Pretty sure all recent DGs come with stall warning built in.
DG's web site explains the background to their thinking.
The system in the DG808C I used to own was pretty good; you
got a verbal warning, hard to misinterpret "Stall, stall".
Dave Walsh

On Saturday, September 8, 2018 at 9:19:29 PM UTC-4, Tom BravoMike wrote:
> On Saturday, September 8, 2018 at 7:14:46 PM UTC-5, SoaringXCellence wrote:
> > AOA devices are becoming very common in the experimental/homebuilt airplane world. A recent publication from the FAA (!) recommended that pilots consider getting a AOA sensor installed in their airplane. The newer completed aircraft in the famous Vans Aircraft RV series are almost all equipped with a AOA device.
> >
> > I have been investigating a AOA system to install in gliders for several years but keep running into challenges due to flaps and spoilers and their effect on the system. The whole device is very easy if the airflow and overall AOA doesn't change much with configuration changes.
> >
> > One fix is to set the system primarily for landing and disable it for other flight regimes. Unfortunately that means you can't use the best L/D AOA, or other selected angles to correct for weight changes.
> >
> > I also have a Raspberry Pi and considered just starting to log the data for my glider. This winter I'm doing a refinish; maybe that a good time to install the pressure sensors and start logging.
> >
> > Mike
>
> In the SZD55-1 Flight manual,
>
> http://org.ntnu.no/nthf/dokument/flight_manuals/LN-GAZ.pdf
>
> p. 12a, it says that "For airworthiness the JAR-22 require the sailplane to be equipped at least with: airspeed indicator, altimeter and STALL WARNING DEVICE." I can remember there was some kind of a buzzer on the SZD-55 I used to own for a short time, but I never heard it sound nor don't know how it was supposed to work.
>
>
> Any other SZD-55 owners/pilots here?

http://www.olk.com.pl/indexen.php?bo=prod&prx=products&lpx=26 is the SZD-55 system. Works well but is a bit startling in the flare the first couple of flights.

Hi all,

I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

More info at my homepage: http://niklaslofgren.net/gliding/variometer/variometer.html

/Niklas

On Monday, September 10, 2018 at 2:30:43 PM UTC-7, wrote:
> Hi all,
>
> I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas
>
> I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas
>
> More info at my homepage: http://niklaslofgren.net/gliding/variometer/variometer.html
>
> /Niklas

Your YouTube links did not have videos.

Oh, sorry, here are the correct links.
Respons test: https://youtu.be/UfeGWYwVdas
vw1020 respons test: https://youtu.be/Irun92_0JWQ?t=11m16s

On Tuesday, 11 September 2018 07:30:43 UTC+10, wrote:
> Hi all,
>
> I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas
>
> I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas
>
> More info at my homepage: http://niklaslofgren.net/gliding/variometer/variometer.html
>
> /Niklas

Yup, I had a club who got a new DG505. Complained the B500 and B400 varios worked OK when settled in thermal but not otherwise especially in cruise. After about 9 months they got around to doing a leak check and the TE system would not hold pressure. They did not know they had a triple probe fitting in the fin and only a TE probe plugged in. The other two lines we open in the cockpit, hence no TE. Nobody managed to figure out this was the problem. This was the same outfit that years before had a problem in their Twin Astir with a B50 installation. A voltage check at the instrument revealed 8 volts or so which wasn't enough. They rewired the glider and 3 weeks later called to say all was OK and even the radio now worked properly which it hadn't for about 18 months since the electrical fire in the back of the glider! No names to protect the guilty.

I looked at your videos. A better test of the vario response is the time taken to return to 63% of the zero from the peak. This is the time constant. When connected as a TE vario this will optimally be around 2 to 3 seconds. Any faster the vario will move around a lot and you will spend time averaging by eye or ear which is workload intensive and effectively slower. Alternatively the 10% to 90% response time is another better measure.
Other comments:
1. The advantage of electronic varios isn't just the various kinds of averagers (running, total) but audio and all the other (netto, relative,speed command) signal processing.
2. I disagree about electrical pitot static compensation. The low drag argument goes away if you have a TE probe anyway for the mechanical or other TE probe compensated vario. The effect of sideslip on a static port on the nose of a glider is usually greater than on a good design TE probe. Then we have the problem of getting two large signals to arrive at the vario at the same time. We subtract these from each other to get the TE vario and any phase errors can cause large spurious transient response on that. Been there, done that, don't need the support calls. Then there is the problem when the static ports do not have constant percentage errors over the speed range.. If you use the Prandtl pitot static on the fin you may as well use the TE probe there. There are errors due to changing G loads and rotation of the glider
3. Time constants in the plumbing. I measured these. Without any vario capacities but including the probe, its holes and the mount in the fin the TE line has a time constant of around 90 to 100 milliseconds. I put an inflated balloon around the probe, hooked the pressure transducer connected in the cockpit to a DSO and popped the balloon. If a typical mechanical vario 450 ml flask is in the cockpit but no vario it went to about 270 to 300 milliseconds.
The time constant of the glider at thermal speeds is about 0.5 seconds on entering lift, as mentioned in an earlier post. If you have a vario connected to static that further slows the vario. If connected to TE that time constant disappears. George Moffat mentioned that a vario is "livelier" when connected to TE in the early 1970s but not the reason why.
Just yesterday Carol and I flew in to South East Queensland gliding club in our BD-4 and ran into a guy from Czech Republic. When he found out who we were, we had a nice discussion on variometers. I was pleased that he had flown extensively with Borgelt varios and he found that they confirmed what his other senses were telling him which he said was unlike most of the others, which confirms your observations about some modern varios.
I've also heard from a German customer that his club bought one of the LCD display devices and he considered it more of a "glider entertainment system" than a vario.

Mike

On Friday, September 7, 2018 at 9:08:28 AM UTC-4, Nick Kennedy wrote:
> This has turned into a very interesting thread. It looks like we may be using some newer much better varios in the near future.
> Another interesting aspect is Mike Borgelt describing the AOA change and the possible cause of low level, low speed [ in the pattern] accidents.
> When were up high cruising at 80-100 knots we fly into 10 knots up all the time and pull hard to slow down and get ready to circle. Up high at speed this is no problem. Down low and slow at say 60 knots that 10 knot thermal you just hit may cause a major problem. I think we may be flying way to slow in the pattern. Looking at the stall/spin rates, in all parts of the arrival pattern, I might be right.
> I like using the Knauff idea of having a longer higher final leg, and as my max flap extension speed in my LS3a is 86 knots, I try to keep it over 70 knots the whole way to the deck, works for me. This may sound fast and it is. I don't want to stall close to the ground by some rouge air or a booming thermal.
> This fast in the pattern stuff was taught to me by Bob Faris CFIG
> So far so good!

Regarding air speeds in the pattern, in a prior sequence the subject came up about the correct speed to fly 2-32s in the pattern. Some of the folks responded that 70 knots was way too fast. Yet this was the airspeed most of us using them in our commercial operations flew them at in New England starting in the late 60s. Despite the fact that the 2-32 had a reputation for spinning in, I don't remember any base to final turn spin ins in New England which suggests that the FBOs who came before me like Jim Doyle and John MaCone were doing something right.

What I do remember was a triple fatality involving a 2-32 in which the glider pilot did not properly lock the canopy prior to take off and stopped flying the glider instead of pulling the release on the ground roll the moment the canopy started flopping. He continued to attempt to close the canopy until the glider reached 100 feet at which point the tow pilot was forced to release the glider. A similar accident also occurred in New England in an ASK-21 that killed the passenger sitting in the front seat along with another 2-32 accident in which the glider pilot had a canopy locking failure on take off on Oahu that killed the pilot only. I suspect there were others I never heard about, after we switched hobby businesses. However we were not immune to a 2-32 spin, that can occur in many different situations. We had a low altitude 2-32 spin in at Plymouth MA, when a tow pilot who obviously was not awake early in the day attempted to tow a 2-32 at its stall speed of 50 mph after landing with the flaps down and neglecting to raise them for the next tow. The 2-32 pilot, unable to keep up with the tow plane, decided to do a 180 return instead of landing straight ahead causing the 2-32 to enter a spin low and hit a cross taxiway right wing down which collapsed and absorbed most of the impact energy injuring the ankles of the passenger only who was sitting in the front seat. The spin in discussions possibly caused by sharp edged vertical gusts are corroborate in YOs discussion in Soaring of the 1986 Regional at Sugarbush in which five gliders were damaged, one fatal, two of which occurred when folks attempted high speed finishes flying too slowly pulled up to go around and instead of gaining altitude spun in. The probable cause was a rotor that frequently forms right over the airport and which on a good wave day when John MaCone operated Sugarbush, broke most of his tow ropes forcing John to go out and purchase a spool of 1/4 inch Nylon rope.

While these comments are not 100% on topic, they highlight what I consider to be a significant problem in our society: disseminating safety information in a manner that does not draw attention to critical safety problems that frequently repeat. In addition, when you can go on the web and watch a video that shows a 1-34 pilot demonstrating precisely what not to do when a canopy flies open on the ground roll or just after lifting off, in which he demonstrates how to fly the glider using one hand to hold the canopy while the other flies the glider, we have a big time problem. Not only are we not reiterating safety issues that were discovered years ago along with their solutions (Schweitzer in response showed that all of their gliders could fly with the canopy flopping), but we are not making a fuss when someone comes along and demonstrates precisely what not to do! As YO also points out, in other countries, folks don't learn to do high speed passes on their own, which is what he claims was the cause of the two rotor induced spin ins at the Bush that did surprisingly did not injure either pilot.

On Thursday, September 13, 2018 at 12:57:15 AM UTC-7, wrote:
> On Friday, September 7, 2018 at 9:08:28 AM UTC-4, Nick Kennedy wrote:
> > This has turned into a very interesting thread. It looks like we may be using some newer much better varios in the near future.
> > Another interesting aspect is Mike Borgelt describing the AOA change and the possible cause of low level, low speed [ in the pattern] accidents.
> > When were up high cruising at 80-100 knots we fly into 10 knots up all the time and pull hard to slow down and get ready to circle. Up high at speed this is no problem. Down low and slow at say 60 knots that 10 knot thermal you just hit may cause a major problem. I think we may be flying way to slow in the pattern. Looking at the stall/spin rates, in all parts of the arrival pattern, I might be right.
> > I like using the Knauff idea of having a longer higher final leg, and as my max flap extension speed in my LS3a is 86 knots, I try to keep it over 70 knots the whole way to the deck, works for me. This may sound fast and it is. I don't want to stall close to the ground by some rouge air or a booming thermal.
> > This fast in the pattern stuff was taught to me by Bob Faris CFIG
> > So far so good!
>
> Regarding air speeds in the pattern, in a prior sequence the subject came up about the correct speed to fly 2-32s in the pattern. Some of the folks responded that 70 knots was way too fast. Yet this was the airspeed most of us using them in our commercial operations flew them at in New England starting in the late 60s. Despite the fact that the 2-32 had a reputation for spinning in, I don't remember any base to final turn spin ins in New England which suggests that the FBOs who came before me like Jim Doyle and John MaCone were doing something right.
>
> What I do remember was a triple fatality involving a 2-32 in which the glider pilot did not properly lock the canopy prior to take off and stopped flying the glider instead of pulling the release on the ground roll the moment the canopy started flopping. He continued to attempt to close the canopy until the glider reached 100 feet at which point the tow pilot was forced to release the glider. A similar accident also occurred in New England in an ASK-21 that killed the passenger sitting in the front seat along with another 2-32 accident in which the glider pilot had a canopy locking failure on take off on Oahu that killed the pilot only. I suspect there were others I never heard about, after we switched hobby businesses. However we were not immune to a 2-32 spin, that can occur in many different situations. We had a low altitude 2-32 spin in at Plymouth MA, when a tow pilot who obviously was not awake early in the day attempted to tow a 2-32 at its stall speed of 50 mph after landing with the flaps down and neglecting to raise them for the next tow. The 2-32 pilot, unable to keep up with the tow plane, decided to do a 180 return instead of landing straight ahead causing the 2-32 to enter a spin low and hit a cross taxiway right wing down which collapsed and absorbed most of the impact energy injuring the ankles of the passenger only who was sitting in the front seat. The spin in discussions possibly caused by sharp edged vertical gusts are corroborate in YOs discussion in Soaring of the 1986 Regional at Sugarbush in which five gliders were damaged, one fatal, two of which occurred when folks attempted high speed finishes flying too slowly pulled up to go around and instead of gaining altitude spun in. The probable cause was a rotor that frequently forms right over the airport and which on a good wave day when John MaCone operated Sugarbush, broke most of his tow ropes forcing John to go out and purchase a spool of 1/4 inch Nylon rope.
>
> While these comments are not 100% on topic, they highlight what I consider to be a significant problem in our society: disseminating safety information in a manner that does not draw attention to critical safety problems that frequently repeat. In addition, when you can go on the web and watch a video that shows a 1-34 pilot demonstrating precisely what not to do when a canopy flies open on the ground roll or just after lifting off, in which he demonstrates how to fly the glider using one hand to hold the canopy while the other flies the glider, we have a big time problem. Not only are we not reiterating safety issues that were discovered years ago along with their solutions (Schweitzer in response showed that all of their gliders could fly with the canopy flopping), but we are not making a fuss when someone comes along and demonstrates precisely what not to do! As YO also points out, in other countries, folks don't learn to do high speed passes on their own, which is what he claims was the cause of the two rotor induced spin ins at the Bush that did surprisingly did not injure either pilot.

Years ago before I had a commercial ticket, my local FBO operated their 2-32's such that 70 MPH was the speed in the pattern. I was out of soaring for decade and half, when I returned to soaring, the SOP for the 2-32 had risen to 80 MPH in the pattern and you fly it onto the runway landing on main only. In the last year I have gotten about 100 hours in a 2-32 flying rides, flies like a dream. But I fly it as the owners want 80 MPH in the pattern and fly it on to a main wheel landing. Got good at kissing the main fairly slow. One of the things I love about a 2-32 is that they are an honest spinner, like a T-6, ham fist it and over you go, hope you know what you are doing.

On Thursday, September 13, 2018 at 10:50:35 AM UTC-5, Jonathan St. Cloud wrote:

One of the things I love about a 2-32 is that they are an honest spinner, like a T-6, ham fist it and over you go, hope you know what you are doing.

Totally agree - flown properly the 2-32 is a sweet glider, same as the T-6. And I found the stall/spin characteristics of both to be entertaining reminders of how planes used to fly - and a strong incentive to respect them! The "balancing on a needle" feeling of a T-6 just before the stall break is priceless!

Been awhile since I spun (intentionally) a 2-32, but still remember the serious push force needed to get that stabilizer forward to break the stall. None of this "let go of the stick and scream like a girl" spin recovery in that beast!

Yeah, I know, not PC, deal with it ;^)

Cheers,

66

On Tuesday, 28 August 2018 05:28:01 UTC-4, Mike Borgelt wrote:

>
> All pressure based instruments will suffer from much the same problems. It does not matter whether the TE compensation is by TE probe or derived from the pitot - static. TE probes are easier as pitot - static compensation introduces potential mismatches between the time the pressure signals arrive at the sensors and as you are subtracting two large signals to look at a small one it is easy to get large transient indications.



Forgive me Mr. Borgelt if I ask a stupid question. I am no expert, but doesn't my ASI subtract these two large signals (Pitot - static)? I do not observe 'large transient indications', ever, expect maybe when I inadvertently stumble in a wave rotor. What am I missing in understanding?

The difference is the slow response of the mechanical ASI damps the transients, whereas an electronic device can respond fast enough to track them.

On Friday, 14 September 2018 21:37:03 UTC-4, Charlie Quebec wrote:
> The difference is the slow response of the mechanical ASI damps the transients, whereas an electronic device can respond fast enough to track them.

OK, understood, thank you. This generates a new question from me (sorry if this is turning out to be a lesson in instrumentation design...):

Can you slow down the response of your electronic system so that it behaves similarly to your mechanical ASI, or does this bring on poorer performance elsewhere?

On Saturday, 15 September 2018 09:43:19 UTC-4, wrote:
> On Friday, 14 September 2018 21:37:03 UTC-4, Charlie Quebec wrote:
> > The difference is the slow response of the mechanical ASI damps the transients, whereas an electronic device can respond fast enough to track them.
>
> OK, understood, thank you. This generates a new question from me (sorry if this is turning out to be a lesson in instrumentation design...):
>
> Can you slow down the response of your electronic system so that it behaves similarly to your mechanical ASI, or does this bring on poorer performance elsewhere?



Please disregard my previous comments and questions. I just read Mike Borgelt's 'Horizontal Gusts' article and this article gives answers to my questions.

On Wednesday, September 12, 2018 at 8:47:09 PM UTC-7, Mike Borgelt wrote:
> On Tuesday, 11 September 2018 07:30:43 UTC+10, wrote:
> > Hi all,
> >
> > I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas
> >
> > I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas
> >
> > More info at my homepage: http://niklaslofgren.net/gliding/variometer/variometer.html
> >
> > /Niklas
>
> Yup, I had a club who got a new DG505. Complained the B500 and B400 varios worked OK when settled in thermal but not otherwise especially in cruise. After about 9 months they got around to doing a leak check and the TE system would not hold pressure. They did not know they had a triple probe fitting in the fin and only a TE probe plugged in. The other two lines we open in the cockpit, hence no TE. Nobody managed to figure out this was the problem. This was the same outfit that years before had a problem in their Twin Astir with a B50 installation. A voltage check at the instrument revealed 8 volts or so which wasn't enough. They rewired the glider and 3 weeks later called to say all was OK and even the radio now worked properly which it hadn't for about 18 months since the electrical fire in the back of the glider! No names to protect the guilty.
>
> I looked at your videos. A better test of the vario response is the time taken to return to 63% of the zero from the peak. This is the time constant.. When connected as a TE vario this will optimally be around 2 to 3 seconds.. Any faster the vario will move around a lot and you will spend time averaging by eye or ear which is workload intensive and effectively slower. Alternatively the 10% to 90% response time is another better measure.
> Other comments:
> 1. The advantage of electronic varios isn't just the various kinds of averagers (running, total) but audio and all the other (netto, relative,speed command) signal processing.
> 2. I disagree about electrical pitot static compensation. The low drag argument goes away if you have a TE probe anyway for the mechanical or other TE probe compensated vario. The effect of sideslip on a static port on the nose of a glider is usually greater than on a good design TE probe. Then we have the problem of getting two large signals to arrive at the vario at the same time. We subtract these from each other to get the TE vario and any phase errors can cause large spurious transient response on that. Been there, done that, don't need the support calls. Then there is the problem when the static ports do not have constant percentage errors over the speed range. If you use the Prandtl pitot static on the fin you may as well use the TE probe there. There are errors due to changing G loads and rotation of the glider
> 3. Time constants in the plumbing. I measured these. Without any vario capacities but including the probe, its holes and the mount in the fin the TE line has a time constant of around 90 to 100 milliseconds. I put an inflated balloon around the probe, hooked the pressure transducer connected in the cockpit to a DSO and popped the balloon. If a typical mechanical vario 450 ml flask is in the cockpit but no vario it went to about 270 to 300 milliseconds.
> The time constant of the glider at thermal speeds is about 0.5 seconds on entering lift, as mentioned in an earlier post. If you have a vario connected to static that further slows the vario. If connected to TE that time constant disappears. George Moffat mentioned that a vario is "livelier" when connected to TE in the early 1970s but not the reason why.
> Just yesterday Carol and I flew in to South East Queensland gliding club in our BD-4 and ran into a guy from Czech Republic. When he found out who we were, we had a nice discussion on variometers. I was pleased that he had flown extensively with Borgelt varios and he found that they confirmed what his other senses were telling him which he said was unlike most of the others, which confirms your observations about some modern varios.
> I've also heard from a German customer that his club bought one of the LCD display devices and he considered it more of a "glider entertainment system" than a vario.
>
> Mike

I am interested in your Dynamis system, but am being frustrated by your website. I keep getting nagged about a java update (most websites have dropped java), and the one time I was able to install it, there was nothing of substance on this vario. Certainly not even pricing or availability. Yet it says it is in production. Can you elaborate?

Tom

As far as I know, the dynamis is an add on to the B800 etc, an external sensor box.
Not yet released for sale, undergoing testing.