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Old Feb 13, 2012, 03:55 PM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
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Quote:
Originally Posted by Daemon View Post
So you cannot answer the simple question I posed above?
What does a TE compensated vario do if you do nothing but increase forward airspeed
via external means (either powered aircraft accelerating, or crossing a wind shear) without changing attitude?

ian
Ian,

I'll answer this one for ya.

A TE compensated vario will register an airspeed increase at constant altitude as "lift". An uncompensated vario is just measuring changes in altitude. IOW, dh/dt. A TE compensated vario measures dE/dt.

A simple vario provides a signal as a function of rate of change of altitude
dh/dt
A TE compensated vario provides a signal as a function of rate of change of energy
dE/dt = (V/g)*dV/dt + dh/dt

(TE = V^2/(2*g) + h)

Note that the TE vario adds the change of airspeed term, so a change in airspeed at constant altitude shows up in the TE vario.
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Old Feb 13, 2012, 03:59 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
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ian I read a very long post of you with netto vario in several locations
http://www.rcgroups.com/forums/showp...9&postcount=28

Let me put is this way. Surely somewhere there is a self powered sailplane with
a Netto Vario. If it is cruising along in dead air with vario indicating zero,
and fires up the motor and accelerates forward *on the same glide slope* that
it was flying before (normally you'd pull up to level flight, but I'm saying, let's
say that does not happen) then will the Netto vario indicate positive lift?


and now you tell it only contents one simple question about the TE compensated vario?

Quote:
Originally Posted by Daemon View Post
So you cannot answer the simple question I posed above?
What does a TE compensated vario do if you do nothing but increase forward airspeed
via external means (either powered aircraft accelerating, or crossing a wind shear) without changing attitude?

ian
You do not understand the difference between the Netto (TE) variometer and the TE variometer!!

See the picture, Alfred Albatross with his Sagitta 900 with MH32 airfoil, and Netto TE variometer.
What would happen when he switches on the engine?

Let's start a thread about this subject because there will be dozens of questions to answer!

Cees
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Last edited by Taurus Flyer; Feb 13, 2012 at 04:30 PM.
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Old Feb 13, 2012, 04:47 PM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
Joined Dec 2004
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Quote:
Originally Posted by Daemon View Post
Joe says he found it useful working the shear far away but I know from experience
that working the shear 400 yards downwind, you're usually flying a more vertical circuit
than horizontal, so any vario would detect changes in altitude, and the Netto vario's
normal TE compensation would be thrown off by the shear crossings, effectively
making it uncompensated and thus indicating lift.
Joe, what did the vario on the same plane indicate in normal near horizontal shear crossings?


ian
Ian,

Sorry, missed this question.

Yes, a TE compensated vario captures pure airspeed changes. I think that the Sandia paper showed some TE plots. The DS Beast was what I put the TE vario on for experimental purposes. On that day, the shear was very high and quite clean. I was DS'ing well downwind of the ridge, and well above the ridge in a relatively horizontal orbit. In an orbit the TE vario gave a rather sharp indication of "lift" when crossing the shear, followed by an indication of more generalized "sink" until the next shear crossing. The portion of the orbit upwind of the shear had a smoother tone (less turbulence) and the downwind portion had a bit of variability, sometimes considerable variability due to the turbulence. The only "gotcha" in the TE vario is that you need to make sure that the -pitot time constant is relatively short.
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Old Feb 13, 2012, 04:51 PM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
Joined Dec 2004
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The interestion part about applying a "Netto" to compensation to a TE vario in DS, is sorting out the adjustments from the usual Netto assumption of ~1g flight. This is not a trivial adjustment to make. For the purposes of DS usage, a TE compensated vario provides about all that one needs, having a Netto vario doesn't add much benefit at all.
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Old Feb 13, 2012, 05:09 PM
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Lakewood, Colorado
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Thanks for the confirmation Joe. And ya, I figured the 1G assumption was not useful
which is why I went back to using TE compensation terminology.

Cees the reason, this is relevant to *this* thread and no other, is that here we're talking about
dynamic soaring in less structured environments than the typical elliptical orbit over a sharp
ridge line. Simply looking for energy and exploiting it wherever it occurs. One such
environment is where the Albatross operates, between the slower moving air close to the waves
and the faster moving air above them. Joe described the one he was playing with,
which is several hundred yards downwind of the normal DS groove. We sometimes like
to "walk" the DS orbit way way back behind the ridge line often in pretty tight circles,
and we listen for the sound of the shear crossings to adjust the orbit position. The problem is,
a few hundred yards away, the delay in sound is great enough that you lose track of
where the shear really is, thus being able to detect it instantly with a vario that is reporting
rapid airspeed changes would certainly help.
The environment I'm interested in is the ratty air we often see around big inland mountain
slopes, where there may be more mountains upwind throwing off big rotors creating massive
shears out in the open sky. If I could detect each shear crossing no matter where they
occurred, energy could be extracted from them by executing DS-style turns. I've done it
plenty of times by feel and other times by accident. I see the plane shudder from a gust, so
I immediately pull hard to accelerate out of it in a new direction with more kinetic energy
than it started with.

ian
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Old Feb 13, 2012, 05:15 PM
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Joe, ian.

Flying around in circles!!

This thread is about the Albatross!!
So have attention for the flight paths he is flying and in which part the Netto is needed or has it's profits!!
Read about switchin on and off the Netto.
End of my input in this thread


Cees
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Old Feb 13, 2012, 05:17 PM
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We don't always fly around in circles. What we're talking about here is how to
make a DS plane more capable of doing what an Albatross does, which
is unstructured, or even cross country dynamic soaring.

ian
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Old Feb 13, 2012, 05:41 PM
I bail out, anywhere, anytime
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Flying around in circles was figuratively.
The Abatross uses several different maneuvers and observing these, all known types of variometers do have profits in different flight paths just as we switch over of modes in 1:1 gliders. There are more types as we were talking about until now!!
For modeling normally only the TE vario is used/available.
There was a period I also did read about a kind of netto vario but never did hear or read of people about using it, so maybe I am the only one.
Writing about all these types will be much to complicated in this thread and isn't related anymore to the Albatross, so I bail out.

Cees
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Old Feb 13, 2012, 09:26 PM
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Ok, I am gonna slap a TE vario on an Albatross and see if it helps the poor animal

On a more serious note, if Cees is convinced his Netto variometer is the cat's meow then he should try to video the plane DS'ing with it to help explain for the very lay people such as myself. I think the potential is there based on the arguments above, but lets see some real testing and results.
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Old Feb 14, 2012, 08:17 AM
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Quote:
Originally Posted by Aerogance View Post
Ok, I am gonna slap a TE vario on an Albatross and see if it helps the poor animal

On a more serious note, if Cees is convinced his Netto variometer is the cat's meow then he should try to video the plane DS'ing with it to help explain for the very lay people such as myself. I think the potential is there based on the arguments above, but lets see some real testing and results.
Aerogance,

To make a video myelf of course is interesting and a goal for me in the future but I already do write my explanation related to the Albatros.
I only have to ask your attention for the first half of the video of post 1

"Wandering Albatross"

Read:The Albatross is simple wander, not wonder!

FIRST take a look at the video again . the first part and have attention for the horizontal tracks!


All nearly horizontal flights paths a few inches above the waves, the output of Netto TE vario (principle) is the only that can be interesting.

Alfred is in a kind of "final glide" (where does that term coming from!!) accurate steering to realize the longest distance This is of high importancy for him when travelling.

But, what is the environmental air doing?

This air is following the surface of the waves, so small vertical displacements, up and down, have to be signalled to Alfred so he can fly on lowest altitude without touching the waves. This is a job for hours and he may not fail!!

His own sink is very accurate calculated by the "Netto", so signalling is "around 0" and a small span (high sensitivity) of the vario can be selected by Alfred.

When the speed is reduced in a track, as result of drag a nice female voice
(Alfrida) says : "Alarm Alfred, Wake Up, Low Speed!!!"

Alfred has some work to do, he has to climb and "pick up some energy" before his dynamic E tank is empty, so he switches off the "Netto" and pulls the elevator for climbing.

A view tenths of seconds later the accelerating of air is detected, tuut-tuut-tuut..... Alfred reduces the elevator input to prevent he spontaneous makes a loop and controlls the angle of climbing. tuut ..........tuut........................... tuut.....

Tank Full Alfred (Alfrida!)





Aerogance, this is no "out-of-the-box" thinking, I only did make a nice reading story of it.
I nature it is reality and the trick only works with a perfect system, so no "boy toy" but calibrated with highest accuracy for measurement of altitude (changes) and airspeed.

Evoluation of the system was a matter of millions of years and not decades!

I have to do some "out-of-the-e-mal-box" correspondence and depending of that result, maybe more to come!!


Cees
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