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Feb 14, 2012, 02:58 PM
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Variometers, what kind of models are used for modeling, especially XC flying?


Maybe it looks like a simple question but there are some reasons for me I did start this thread with the question:

Variometers, what kind models are used for modeling, especially XC flying?

A background of the question is, I do design and built my "vario's" for about 35 years now and so know all models and way of functioning (I think!).

RCGroups does have a wide experienced group of glider pilots in a wide range of activities, that is amazing, but I am surprized I only read about two models of vario's ,

Normal and Normal with "TE" compensation, or read "variometer" and "TE variometer".

As far as I know Picolario, WSTech etc. are (still) part of these groups! Who knows?

To give all models I am familiar with.

1 Normal variometer, so without TE (tube)
2 Normal variometer with TE compensation, called TE variometer for example (about 4 princliples) and the model normally used for modeling by using a TE tube
3 Netto variometer or air mass vario
4 Relative netto variometer
5 Variometer with Mc Cready "Speed to fly" calculation
6 Final glide computers

All methods are used by me to design my own variometer systems.
Point is in the Netherlands we do not fly XC, but 3, 4, 5 and 6 would be very useful for that way of gliding.

So the question to fullfill my curiosity, who knows of examples of variometers and especially models 3 4 5 and 6 worldwide used for modeling and for example in XC?.

Be aware the names/descriptions of models can be slightly different than used by me, but we can figure that out when we read a description of working.

It is also possible to find descriptions on the WWW about the different principles.

Last edited by Taurus Flyer; Mar 07, 2014 at 05:08 PM. Reason: Subject changed for second phase
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Feb 14, 2012, 04:56 PM
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Our team's experience has been with using either a Telario or Picolario.

Many years ago I was working on using a telemetry system that used the SoarPilot S/W.

You can find the Wiki here:

That would cover your types 5 and 6.

- Bob -
Feb 14, 2012, 05:50 PM
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danstrider's Avatar
I tried once to compile all the variometer models I could find for RC use:

From participating at Montague and Cal Valley a couple of years, most folks are using a compensated vario with a few folks still preferring an uncompensated. I don't know if I've actually seen a compensated vario that uses both static and total pressures directly (for the RC market). This style of compensation would be necessary to get to your #5 and #6, owing to the need for separate airspeed and altitude. There could be some reasonable guesses of the sink polar to turn a compensated vario into a netto digitally, just as folks tailor the geometry of their the total energy probe to over- or under-compensate slightly. However, I believe we're back to requiring separate airspeed and altitude to do a netto vario justice (e.g. A speed to fly vario is perhaps overkill for the RC market without a way to effectively hold airspeed constant and a way to tell the pilot to adjust speed up/down.

Does this answer the question? ... hoping I contributed something useful to the discussion.
Feb 14, 2012, 06:40 PM
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Taurus Flyer's Avatar
Bob and Dan,

I was interested so did take a look on the laptop. It is midnight in the Netherlands so I'll make a short post and respond later after studiing the information you show.

Interesting Dan? Of course, All you write is correct, and after collecting the information we can summerize a kind of "basic design" of which is interesting.

When I read XC I think this is the modeling that can have most profit of showing know-how. I also would not be surprized we discover a gab in development of varios especially for XC!!!! Keep in mind I am not experienced in XC, so look at a different way and other background, "completely blanco". I was 1:1 glider pilot myself in the very past, KA8!

Bob, I did take a short look at the SoarPilot S/W system. You write experiences many years ago. Is seems to be too complicated to use for modeling? Is that correct, this would be interesting to know. What were the main disadvantages in using the system (if you still know?). Not needed to respond in details, We do not have to analyse the system, if it isn't used anymore.
The other brands Telario and Picolario I will study and respond about their developments.

Thanks both,

Last edited by Taurus Flyer; Feb 14, 2012 at 06:52 PM.
Feb 15, 2012, 07:29 AM
Registered User
To Dan :

I've read your PDF with a lot of interrests. I'am building this telemetry suit :
my RCgroup blog and I have questions.
My sensor board is fitted with 3 ported pressure sensors ; Vario, IAS, Altitude.
I'd like to compute L/D on the fly on the smartphone but also buid a Sink Polar Curve. So here come the 2nd order equation and my issue (I'am very rusty when it comes to math) : how to obtain those equation constants a, b and c. Is it possible to have a quasi run time Sink Polar equation maintained with the incomming telemetry data ?
Feb 15, 2012, 08:51 AM
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Taurus Flyer's Avatar
Bob, Dan but also Zenoid,

I did the first added literature research and show some first comments to gain some interaction.

(Nearly) no TE compensation with other systems than the TE tube (TEK düse) even there are more methods, this results in limitation of development!

No use of netto, and relative netto (TE) variometers as far as I can find until now, or we have to look at complicated systems as Soar S/W used for parasailing and real gliders, or Piccolo Autopilot for all kind of UAV as I conclude (correct?).

Also I find a lot of useless written communication as result of lack of know-how about variometers and needed accuracy of measurements.
Not a problem at all of course, I was blanco, and it is my conclusion. W'll see in the near future when I show some examples!

We wait for some more information while I study the information I already have and I also see the post of Zenoid and his blog,
It looks like Zenoid can use some assistance.
Zenoid, do you write about the pdf document of Dan Edwards?
I think it is another Dan than our Danstrider, is that correct.

Feb 15, 2012, 09:07 AM
Registered User
Yes I was referencing DanStrider link :
a few post ago. Sorry I mixed some Dan up for another one.
Feb 15, 2012, 09:10 AM
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I did want to have it clear because I wasn't impressed about the pdf document!

Feb 15, 2012, 10:15 AM
Registered User

it was about 8 years ago when I was working on it. At that time, our main problem was poor transmitting/receiving components, which caused many connection problems. We would simply loose signal for sometimes 10-20 seconds and it became very frustraiting; to the point of stopping any further development.

With the advent of Digi's XBee modules the issue should be better.

H/W wise, it was a pretty simple setup. In the plane, a GPS module driving a transceiver. On the ground, a transceiver driving the Palm. This would be the same kind of equipment used today in the scale GPS triangle racing.

In those days we were flying with a team of four: pilot, co-pilot, driver, and tactician. The tactician could easily man the Palm PDA to look at and analyze the information and pass it out.

Now we are down to just three persons, and no one to look at the data.

SoarPilot could very easily be used today and there would be some advantages I see to use it. At most of the XC contests here on the West Coast, teams consist of three (even two I seen). At a tech session last year at Montague, where we discuss what teams would like to see in a next generation telemetry system, most if not all teams wanted the data to be presented in an audio format where the pilot/co-pilot could hear rather than having an extra person on the team. Converting some of the data to audio format is possible. It would be very difficult to get all the necessary data outputting in an audio format.

- Bob -
Last edited by HLGNut; Feb 15, 2012 at 10:26 AM.
Feb 15, 2012, 11:21 AM
Registered User
To HLGNut :
Converting some of the data to audio format is possible. It would be very difficult to get all the necessary data outputting in an audio format.
On my smartphone or PDA application, essential data are in audio too. I have the vario tone, VNE and stall alarms, a wind/air speed continuous modulated sound. I also have speech for altitude, current turnpoint distance and it's relative clock orientation, and then differential altitude to turnpoints.
What is difficult is to fly solo and have enough time to give attention to every speech. When racing on a slope with multiple turnpoints, it's easier with a copilot.
Feb 15, 2012, 12:27 PM
Registered User
Zenoid, I was just on your blog and website.

Very impressive!!!!!

You've done much more than I was planning on doing, especially w/ audio.

- Bob -
Feb 15, 2012, 01:12 PM
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Taurus Flyer's Avatar
Originally Posted by HLGNut View Post
Zenoid, I was just on your blog and website.

Very impressive!!!!!

You've done much more than I was planning on doing, especially w/ audio.

- Bob -

Bob, I quoted the post on the moment I did want to download my own post!

Here we see the shortcut!!!!


Interesting to read your project of 8 years ago, but you write in that post 9 last phrase .....

It would be very difficult to get all the necessary data outputting in an audio format.

does trigger me to write this post and show a picture of one of my instruments,

For XC, of course information stream is needed about location, circumstances etc but , it's not clear to me what that basicly has to do with the variometer. Not to start a debat, of course not, but only to wake up people to hear if I can be right? Keep in mind my most important argument, the variometer is the most important instrument in the glider and for the pilot, not only in thermals but also outside!!

Design an instrument is basicly formulating the basic design requirements and I can complete a variometer design for general requirements.

The variometer in that case of course will be designed with features like (and/or) TE, netto, relative netto, Mc Cready etc. but as I did write in post i, I distinguish about 6 different steps and do find back (until now) only one or two of basic models in reality!

A picture of one of my instruments of the past, with dutch certification for 1:1 gliders of the pré GPS period! To show my way of thinking related to XC.
This instrument has acoustic communication features for vario and speed and has nothing to do with navigation or GPS but even all functions are needed to fly XC !!

Last edited by Taurus Flyer; Feb 15, 2012 at 01:19 PM.
Feb 15, 2012, 01:15 PM
Registered User
Many thanks HLGNut.

Point is in the Netherlands we do not fly XC, but 3, 4, 5 and 6 would be very useful for that way of gliding.
So Cees if I understand correctly, what is needed to achieve those points is to be able to somehow calibrate the sailplane and its sink polar curve in still air. Then you have the material to give real time netto or speed to fly or final glide.
I've found some stuff on the www and wrote some code this afternoon that extract the famous polynomial equation from pairs of air / vertical speed. I get LD, speed to fly and all the constants of the equation. Got the experimental polar equation.
But what is of any use when you are a rc pilot ?
I'am not sure all those netto, SPDF, final glide are of any use in Europe as racing is very local. It's different in the US. Other valuable stuff :
Being able to qualify the glider after you have build it ?
Do some aerodynamic research ? May be I'll add a kind of "lab" tab in my application. Interesting thread.
Feb 15, 2012, 01:42 PM
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Taurus Flyer's Avatar

Main goal to start the thread is education. Knowing what is going on world wide related to variometer systems.
No the Netherlands are small, each final glide will result in a landing outside the country (LOL, not true of course) and I read the stories about the USA and Australia!!Jealous? Yes I am!!

Why I built my systems even in these circumstances?

It seems most systems are from German brand and these are our neigbours so the spirit is here.

Are you intersted in my comments on your system?
It's not a separate variometer system I understand, more a complete communication system?

Feb 15, 2012, 02:03 PM
Registered User
each final glide will result in a landing outside the country
like this one !

Are you intersted in my comments on your system?
Of course I 'am. It's a complete system :
- Sensor board (pressure and GPS) and many other stuff
- Plug the sensor board to a FrSky receiver on the data port
- plug a bluetooth module on the FrSky tx
- Bind the bluetooth on my android application and fly a race.
- I can also use any radio modem instead of FrSky, I've made one in the 2.4GHz band also. Using FrSky is better as you have a lightweight glider installation.

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