TE variometer numbers

[jp]

We know that a variometer with a TE probe fitted indicates total energy of the glider and not necessarily whether the glider is ascending or descending.

Good enough, although I still find myself treating the vario as if it is telling me about lift and sink.

BUT, if we are clear of mind to see the TE variometer as indicating total energy what then do the numbers on the vario face indicate?

[Hank Nixon]

We don't know what you stated. It does tell you lift and sink. TE is intended to take out the change in displayed lift or sink caused by a change in speed.
Maybe easier to think of it as a speed compensated vario.
UH

[jp]

Thank you Hank. As far as I understand the TE stuff (which is clearly not very far) the TE connected vario would only be indicating potential energy (i.e. up or down I guess) if the airspeed ( kinetic energy ) is held constant. If both the kinetic energy and potential energy are varying, which I confess if often what is happening when I am flying, the TE connected vario will indicate the algebraic sum of the kinetic and the potential energy.

I was just curious. Most of the time I pretend the TE connected vario is just indicating the up or down of the glider regardless of the airspeed or altitude changes.

[R]

What do you mean by ‘TE Connected’? What do you understand to be happening?

R

[R]

And since you are thinking in terms of lift…if only one of two was working …accurately…which would you pick?
You vario or your audio? Both require tuning to get maximum performance.

R

[Chip Bearden]

A TE vario does tell you whether you're going up or down. As UH noted, it just removes the temporary swings caused by exchanging speed for altitude or, said another way, exchanging kinetic energy for potential energy). The total energy of the glider is always declining as we glide down--until we find lift.

What you might be looking for is a netto vario, which tells you how fast the air is rising or sinking, regardless of what the glider is doing (assuming everything works properly which, as has been said, requires tuning). I flew with a netto vario for many years before the advent of the newer computerized varios (Cambridge Mk II, for you old timers) and loved it. More recently, another flavor usually called relative netto subtracts out the glider's sinking speed in thermaling flight from the netto reading to tell you how fast you would be going up or down if you stop to circle. I had that, too; I just put a mark on vario dial at about 1.5 kts. If the needle went above that, I could climb if I stopped to circle.

Others might have a more elegant explanation but that's how I think of it.

Chip Bearden
ASW 24 "JB"

[Hank Nixon]

What you are "pretending" is just what the TE compensated variometer is supposed to do. If you want to get into fancy descriptions it is showing the rate of change of potential energy. That said there is no reason to out think it. It's purpose is to tell you how fast you are going up or down without speed changes messing up the information.
UH

[jp]

Thank you all for helping me understand this stuff. By the way, it would be nice if I had an audio vario but I don't.

I will stop over-thinking this stuff. It confused me that the TE-connected vario ( by which I mean a vario connected to a TE probe rather than just to the "ordinary" static ports ) shows what looks like ascent when I am being pulled along the runway - clearly not ascending. From that experience I concluded that the vario was not indicating, at least not directly indicating, the glider is rising. I'm not at all sure that I can do anything with that knowledge anyway.

I think it would be best for me to just forget about all the TE-vario I read about and just fly the silly glider.

But thank you all for your helpful responses.

[BobW]

Expanding on "what Chip said," my main vario/compensation system for decades
was a Sage vario with netto compensation (both by the late Wil Schuemann).
Loved it! Conceptually netto (to me) "can't be improved upon." If you know
what the air is doing, you know what your glider can do.

Once off tow, independent of glider speed or stick inputs, it simply displayed
airmass movement...which was all I ever wanted to know, since I knew (from
polar/experience/etc.) the glider's thermaling-condition sink rate, and thus
potential climb rate for any displayed, rising, airmass movement. I didn't
bother with putting a mark on the netto dial, preferring simply to subtract
(in round numbers) 2 knots from the needle's reading as "projected climb
rate"...and then verifying by measuring altimeter-reported gain every 60
seconds. Verification was a "trust-but-verify" 2nd nature thing for me.

On tow, it displayed "funky information" which - upon reflection - I concluded
was due to the added energy imparted to the glider from the towplane (which
sorely confused the situationally-ignorant netto system). Perhaps proving you
can rationalize anything if you try hard enough, I rationalized it improved my
lift-sensing butt sensors prior to release!

YMMV.
Bob W.

[Chip Bearden]

Bob, I actually had two of the Cambridge Mk II varios. One was fed by (you said it!) a Schuemann box, a wonderful device that comprised a capacity bottle, a stainless steel diaphragm TE compensator, a gust filter, and a netto capillary. I had done my senior research paper on netto varios back in 1972 so I decided I could build my own. I connected the second Cambridge to a TE tube and tee'd in an early Cambridge gust filter. Wil Schuemann groaned when he saw it because, among other things, it was a polyethelene bottle with flexible sides. But it seemed to work. For the netto, I spent an evening snipping the end off a bunch of hypodermic syringes, then inserted them into short pieces of 1/4" metal tubing and pouring epoxy in to seal them. On a good day, I connected everything up--including t'ing the netto into the capacity line, and then experimented (this all being in my lap) adding and subtracting segments of syringe needles until the vario read about zero at all speeds. Unlike today, of course, my calibration was only good for one wing loading (and one altitude, until I upgraded to the Schuemann "B" box), but it worked pretty well.

Raouf Ismail at Cambridge wired up a switch that allowed me to drive my Cambridge audio with whichever vario I was using. So with separate batteries, I had two completely independent netto varios. It was a great day when I could pull and push fairly aggressively and both varios read almost the same.

In those days, another great thing about a netto vario is that you could simply fly whatever speed the vario was pointing at on the speed ring, rather than chasing the speed and iterating. If you don't know what a speed ring is, don't worry. Trust me when I say this combo gave me great info about what the air was doing and how fast I should be theoretically flying. I still couldn't fly like George Moffat or A.J. Smith but at least I was working with good data.

End of history lesson. :) If you made it this far, thanks for humoring me.

[R]

As jp never clearly answered one of my question above, I believe he believed having a ‘TE Probe’ was all that was needed to get good vario information. Hopefully he will read, comprehend, and seek additional information such as what was provided above.
And save his nickels for an audio.

R

[Martin Gregorie]

On Fri, 10 Feb 2023 15:43:38 -0800 (PST), jp wrote:

> Thank you all for helping me understand this stuff. By the way, it
> would be nice if I had an audio vario but I don't.
>

You could do a lot worse than to fit one it doesn't need to be shiny new
and expensive: its main benefit is that it keeps your eyes outside
because, your ears can continuously monitor what you currently have to
keep looking inside to check. Look around for a decent used audio vario
and fit that: I carry two, both quite old: an 80mm SDI C4 and a Borgelt B.
40. Both make well modulated noise so don't need to get looked at much.

The C4 has a lot of capability: if connected to an GPS feed it can keep
track of your arrival height at your next turnpoint and, as one of the
first varios to use a (monochrome) solid state display, its fairly
indestructable and is very easy to read under all lighting conditions.

I use the B.40 as a backup because a 9v PP3 battery can run a B.40 for at
least a day, but its also an excellent vario that I'd be happy to use as
my primary if I didn't have the C4.

Both these varios are over 20 years old, so you should be able to find at
least one of them at a reasonable price.

Then all you need as backup for your Mk 1 eyeball is a FLARM: because its
something else that you don't need to look at until you hear it beep.

And, while you're at it, if fitting an audio vario requires an panel
rearrangement, consider moving your ASI to top centre in the panel: once
you've got an audio vario and FLARM its probably the instrument you'll
look at most and I've found that just below your sight-line is a good
place for it.


--

Martin | martin at
Gregorie | gregorie dot org

[Nicholas Kennedy]

The August 1975 of soaring has a good article by Gren Seibels
on his experience of installing and flying with the magic "SCHUEMANN'S BOX"

Little bit of history for those interested in that kind of stuff.

Having a well-compensated Netto function is worthwhile if you fly fast IMHO.
Paul Remde has a CAI 302 for sale, on this forum; what a great instrument at a great price.
Nick
T

[BobW]

On 2/10/2023 9:09 PM, Chip Bearden wrote:
> Bob,

<Insightful/interesting history lesson snipped...>

>
> End of history lesson. :) If you made it this far, thanks for humoring me.

I thank you *for* the stroll down memory lane! I infer you may've been in the
set of humanity for whom "Better is the enemy of good enough," while I was
definitely a "Good enough!" sort, in terms of cockpit displays.

There were a few times when my "netto-display-enhanced, on-tow lift-sensors"
worked in my favor when bugs or water blocked a pneumatic line resulting in
flights 100% dependent on "feel and altimeter" to remain aloft (and even go
XC), absent functioning-vario info. Irksome/aggravating/fun....if undoubtedly
slower achieved XC speed. (Too cheap/impatient-to-be-aloft-n-soaring to
land/fix/re-tow...)

WRT your pointing out "the MacCready-ring advantage" of netto displays...indeed!

This entire "vario/display topic" has long been a fascinating - to me, anyway
(dry chuckle) - glimpse into the remarkably different ways brains perceive the
world around us. I expect your informal count of fellow glider pilots with
whom you've interacted over the years whenever the topic of your varios'
display arose, who "got hung up on" the idea that..."But if my vario doesn't
display my actual climb rate in a thermal, I'm gonna die!!!" is large (as is
mine). I eventually gave up trying to convert people to "seeing the airmass
world correctly," as distinct from their glider-centric,
instantaneously-vario-displayed, lens.

Better not open up discussing such things as "Yebbut in those Jurassic days,
your netto woulda displayed-erroneous-info while carrying water. Take *that*
you weirdo!!!" Nothing like - for the average weekend warrior anyway, if
arguably not those seeking serious records or even national contest victories
- "shiny mental objects" (apparently) obscuring fundamental understanding!

Bob W.

[jfitch]

To be completely accurate, the TE connected vario is telling you the *rate of change* of potential energy. Not potential energy. These are somewhat different things. The rate of change is the velocity up or down in the gravitational field, added to the rate of change of air speed. At any fixed airspeed, a TE connected and non TE connected vario will show the same number. Potential energy itself is shown by the altimeter and airspeed indicator.

[Dan Marotta]

Which means that the glider's total energy is increasing, at this
specific time it is increasing in kinetic energy only. When you take
off your potential energy starts increasing and will add to the reading
on the vario. Once off tow, the TE needle tells you the same thing
except that changes in air mass movement, drag, and airspeed are the
what cause changes in total energy.

Dan
5J

[jp]

Thank you all again. And I'm sorry R that I have not answered your question. I'm a low-time glider pilot and I do not own a glider. I am happy to rent gliders and sometimes, rarely but sometimes, I get a glider that has an audio vario but usually the glider just has a mechanical vario - no audio.

There are several things about gliding and especially about soaring that can twist my head around. I have to try hard to remember that low altitude is higher pressure and high altitude is lower pressure, etc.. I try hard to remember than the altimeter just indicates the distance ( at an assumed 1000'/inch HG ) between what is set in the Kollsman window and the ambient air pressure where the glider is - and how the altimeter indication can be effected by colder or warmer than standard air temp and how the altimeter indication can be altered by unaccounted for ambient pressure changes, and on and on and on.

I think I do a fair job of controlling the glider but the varying descriptions of many of these weather / altimeter / variometer things just ties my brain in a knot.

I have read a lot about TE variometers and still get easily confused. Some sources say the TE variometer does not indicate lift and sink but rather change rate of total energy. I understand that but don't know how to make use of total energy changes in seeking lift. I am not yet persuaded that an increase in Total Energy always means lift and what the TE variometer indicates in an airspeed-increasing DESCENT is a complete mystery to me. I do know that the goodness of the TE variometer is in reducing the effect of "stick thermals" on the indication of lift but, at least when I fly a glider it's going both up and down - mostly down.

Anyway, I can live just fine with all this confusion. I just fly the glider and enjoy the view.

Thank you again.

[Hank Nixon]

When flying forget about total energy and just use the variometer to guide you about climbing or sinking. no other brain effort is required.
Assuming it is working right, up is up(good- happy) down is down(not so happy).
End
UH

[jp]

Thank you Hank. I will do just that. I really like your reccomendation.

[Roy B.]

Hank has it right (as usual). If you really want to wade deeper into this stuff, G Dale's book, The Soaring Engine, Volume 4
explains most of what you would want to learn about variometry.
ROY

[john firth]

Confusion over the TE compensated vario may be caused by a horizontal gust
producing a transient lift reading; it does indicate the energy available from
the extra airspeed, but this is hard to use .( except in the case of climbing into positive wind
shear just after take off).

I believe some of the latest varios will remove the gust transient from the vario reading.
In normal inter-thermal flight this is useful and I plane to modify my trusty Winter vario
to do this pneumatically.

John Firth
old , no longer bold , out of date pilot.

PS I used to make the gust filters for Cambridge; the plastic 1/2l bottle
was fine unless mounted somewhere a G transient could squash it.

[jp]

Hi Roy,

I have read all four of G Dale's books and I think they are very helpful. If I see a quick, sharp vario needle jump I presume it's a gust and
not a thermal. As G Dale says, the TE variometer is extremely sensitive to gusts. The vario needle jumps up but should not be assumed
to be indicating lift, at least not thermal lift.

[Chip Bearden]

> John Firth
> old , no longer bold , out of date pilot.
>
> PS I used to make the gust filters for Cambridge; the plastic 1/2l bottle
> was fine unless mounted somewhere a G transient could squash it.

That gust filter always worked great for me. It was protected from squashing but the end was occasionally exposed to sunlight so I suppose that could have caused problems. In any case, it worked.

John, I've seen your name numerous times on this forum. Given your comment about being old and no longer bold, I wonder if you were the pilot who electrified the crowd at the Elmira Nationals in 1968 by exploding out of the ground as you approached from the SE. I was 17 and visiting with my family for a few days and was watching another glider on final glide when (if I am correct) your HP-11 came climbing steeply from below the Hill, then finished. Still one of the most dramatic arrivals I've seen. Or perhaps that was a different John Firth.

[Roy B.]

>
> John, I've seen your name numerous times on this forum. Given your comment about being old and no longer bold, I wonder if you were the pilot who electrified the crowd at the Elmira Nationals in 1968 by exploding out of the ground as you approached from the SE. I was 17 and visiting with my family for a few days and was watching another glider on final glide when (if I am correct) your HP-11 came climbing steeply from below the Hill, then finished. Still one of the most dramatic arrivals I've seen. Or perhaps that was a different John Firth.
> Chip Bearden
> ASW 24 "JB"

Chip:
I do not know of the story you mention, but John Firth - whom I am privileged to call my friend - flew the very first FAI 750 km triangle flight done in North America. I have written the story here before and it is worth reading again:

The very first North American 750 km triangle was done by John Firth in a Kestrel in Ontario.
It was one of the most remarkable and simply audacious flights ever done in a glider. In 1977 John conceived of a 750 km attempt on what was then the "new" FAI record triangle distance. Even with the remarkable flights being done out of Texas in the late 60s and 70s and Streidick's record setting Appalachian ridge flights, nobody (much less some silly bloke in eastern Ontario Canada) had ever attempted the 750km FAI triangle. I once asked John how he came to even think of it and he said, "well I was getting rather bored and it seemed sort of interesting at the time . . ." Nobody else in his club was even flying cross country!

John declared the flight several times before succeeding. It was done in July of 1977 in his 19m Kestrel over a course that took him from near to Ottawa, southwest to Bethany, up to South River and then across 50 miles of the completely unlandable Algonquin Provincial Park and then back on toward his start. Thermal strength was only in the 4-5 kt range. The last leg of the flight was in the blue. His time on course was over 9 hours. He started at 10:00 am with all the ballast he could get into the Kestrel and landed after 7:00 pm. No computer, no moving map, no GPS - just an electric vario and 2 turnpoint cameras to prove the turns. To put it all into perspective, today, after 46 years and with infinitely better equipment and hugely better weather support, nobody has yet done an FAI 750 km triangle in New England.

Today, at an age that I don't dare ask, John still flies a PIK 20E motorglider out of a little airport in Ontario. I want to be like him when I grow up.

John posts here once in a while and his flight is worth remembering.

ROY

[John Foster]

The TE-connected vario is supposed to indicate lift while you are accelerating down the runway even though you are still on the ground--BECAUSE due to your acceleration, you are gaining energy--kinetic energy, even though you are not climbing (potential energy. Your TOTAL energy (KE + PE) is increasing because while the PE (altitude) remains the same, the KE (speed) is increasing. Thus the vario indicates "lift". This is how it's supposed to work.

[jp]

Hi John,

Thank you for your comment.

Yes, I do understand why it is the vario is indicating "up" as the glider gathers speed along the runway. It is a good example of how a TE vario presents rate of change of energy. What left me uncertain is just how I might make use of rate-of-change of energy when I am looking for lift. I understand now from all the helpful comments I've received here that, at least some of the time, I can just see the up-needle on the TE vario as an indication of lift. I can live with that.