TE probe installation

[Jim Lewis[_2_]]

I have been trying to understand just how a TE probe functions.

Is a TE probe plumbed as the only static source for a variometer or is it plumbed together with the static ports that are usually placed on the sides of a glider?

Thank you.

[[email protected]]

On Thursday, December 4, 2014 2:02:55 PM UTC-5, Jim Lewis wrote:
> I have been trying to understand just how a TE probe functions.
>
> Is a TE probe plumbed as the only static source for a variometer or is it plumbed together with the static ports that are usually placed on the sides of a glider?
>
> Thank you.

Probe replaces static and provides a source to the variometer that is of the same magnitude as pitot pressure, but the opposite sign.
UH

[Nick Kennedy]

http://www.nadler.com/sn10/Brozel_TE_Compensation_20020510.pdf

Here is some help
Nick

[Jim Lewis[_2_]]

On Thursday, December 4, 2014 12:13:40 PM UTC-8, Nick Kennedy wrote:
> http://www.nadler.com/sn10/Brozel_TE_Compensation_20020510.pdf
>
> Here is some help
> Nick

Thank you Nick, and thank you UH.

I have also read in several references, including Reichmann, that the TE venturi pressure must be -1. I do not understand what this means. Can you explain this without heavy math?

Thank you

[JP Stewart]

On Thursday, December 4, 2014 7:47:08 PM UTC-5, Jim Lewis wrote:
> On Thursday, December 4, 2014 12:13:40 PM UTC-8, Nick Kennedy wrote:
> > http://www.nadler.com/sn10/Brozel_TE_Compensation_20020510.pdf
> >
> > Here is some help
> > Nick
>
> Thank you Nick, and thank you UH.
>
> I have also read in several references, including Reichmann, that the TE venturi pressure must be -1. I do not understand what this means. Can you explain this without heavy math?
>
> Thank you

This may help clarify things some (this doc is in early draft and may still have bugs) https://dl.dropboxusercontent.com/u/19269531/TEdesignExplainedV2.pdf
The -1 is based on what is experimentally measured for the flow around a cylinder.
JP

[[email protected]]

I am replacing my Cirrus fuselage probe with a new rail mounted probe. From my research it appears ILEC wants it turned up with the head in the same horizontal plane as the horizontal stabilizer. This will be the all moving stabilator on my Cirrus. Do you guys agree with this placement?

Lane
XF

[[email protected]]

On Friday, December 5, 2014 7:42:13 AM UTC-5, wrote:
> I am replacing my Cirrus fuselage probe with a new rail mounted probe. From my research it appears ILEC wants it turned up with the head in the same horizontal plane as the horizontal stabilizer. This will be the all moving stabilator on my Cirrus. Do you guys agree with this placement?
>
> Lane
> XF

Sensing quality, assuming fin mounting is generally improved by being as high as possible above the wing root wake and well forward of the pressure field from the tail surfaces. "Well forward", from my experience, is at least 24 inches. I have found no improvement when going more than 36 inches forward and the improvement is fairly small above 24 inches.
UH

[Jim Lewis[_2_]]

Thank you JP. I'll dig into the info today.

Forgive me for this simple-minded question. What pressure (static, dynamic, total) is provided to the variometer by the TE probe? I have read that a TE probe must create a pressure inverse but equal in maginitude to the dynamic pressure at the pitot. This confuses me. I thought the pitot 'receives' total pressure not just dynamic pressure.

I do understand that a variometer is a flow meter that responds to the flow of air between a capacity and the pressure sensed by the static ports. Does the TE probe provide this static pressure (offset by changes in dynamic pressure created by the glider varying airspeeds) or is the TE probe providing dynamic pressure to its side of the variometer?

I am trying to understand the TE process without being able to actually measure the pressures involved.

Thank you.

[Dan Marotta]

Without getting into the math (mainly because I don't remember any of
it), the TE probe delivers static pressure reduced by the suction effect
caused by the air flowing around the probe. Remember that the holes in
the TE probe are near the back and, according to Bernoulli (I think it
was), when the velocity increases around the probe the pressure is
reduced and vice versa.

On 12/5/2014 9:26 AM, Jim Lewis wrote:
> Thank you JP. I'll dig into the info today.
>
> Forgive me for this simple-minded question. What pressure (static, dynamic, total) is provided to the variometer by the TE probe? I have read that a TE probe must create a pressure inverse but equal in maginitude to the dynamic pressure at the pitot. This confuses me. I thought the pitot 'receives' total pressure not just dynamic pressure.
>
> I do understand that a variometer is a flow meter that responds to the flow of air between a capacity and the pressure sensed by the static ports. Does the TE probe provide this static pressure (offset by changes in dynamic pressure created by the glider varying airspeeds) or is the TE probe providing dynamic pressure to its side of the variometer?
>
> I am trying to understand the TE process without being able to actually measure the pressures involved.
>
> Thank you.
>

--
---
Dan Marotta

[Jim Lewis[_2_]]

Thank you Dan. That helps a lot.

[[email protected]]

On Friday, December 5, 2014 11:26:06 AM UTC-5, Jim Lewis wrote:
> Thank you JP. I'll dig into the info today.
>
> Forgive me for this simple-minded question. What pressure (static, dynamic, total) is provided to the variometer by the TE probe? I have read that a TE probe must create a pressure inverse but equal in maginitude to the dynamic pressure at the pitot. This confuses me. I thought the pitot 'receives' total pressure not just dynamic pressure.
>
> I do understand that a variometer is a flow meter that responds to the flow of air between a capacity and the pressure sensed by the static ports. Does the TE probe provide this static pressure (offset by changes in dynamic pressure created by the glider varying airspeeds) or is the TE probe providing dynamic pressure to its side of the variometer?
>
> I am trying to understand the TE process without being able to actually measure the pressures involved.
>
> Thank you.

The pitot does indeed have an absolute pressure equal to local static pressure plus dynamic pressure. An airspeed indicator compares this to static, so far all intents and purposes, static pressure is meaningless.
A FLOW type variometer uses TE pressure(Pitot x -1) to compensate the variometer for velocity change. Static is not a factor.
In transducer type varios, there is no flow. These devices use pitot compared to static, and TE compared to static to get a similar result. Some others do not use TE pressure and derive required input by inverting pitot signal electronically.
For most folks it is good enough top take this stuff on "faith". It does work.
UH

[Jim Lewis[_2_]]

Thank you again UH. I do take this on faith since I understand the purpose of the total energy compensation and I can see its effects. Unfortunately, students sometimes ask 'how'. I feel I must avoid talking nonsense when they ask. So far I have just replied that I do not know 'how' but I do know 'what'. After several such experiences my own curiosity has led me to try to understand 'how'. I guess I can't help myself!

[[email protected]]

On Friday, December 5, 2014 5:20:55 PM UTC, Jim Lewis wrote:
> Thank you again UH. I do take this on faith since I understand the purpose of the total energy compensation and I can see its effects. Unfortunately, students sometimes ask 'how'. I feel I must avoid talking nonsense when they ask. So far I have just replied that I do not know 'how' but I do know 'what'. After several such experiences my own curiosity has led me to try to understand 'how'. I guess I can't help myself!

For another excellent reference about pneumatic tubing and TE compensation see Part 1 of this paper by Dave Ellis (now of ClearNav and previously the designer of the Cambridge 302)

http://www.clearnav.net/Technical/Variometer%20pneumatics.pdf

John Galloway

[Jim Lewis[_2_]]

Thank you John. It's an excellent article.

[[email protected]]

On Friday, December 5, 2014 9:00:22 AM UTC-8, wrote:
> A FLOW type variometer uses TE pressure(Pitot x -1) to compensate the variometer for velocity change. Static is not a factor.
> In transducer type varios, there is no flow. These devices use pitot compared to static, and TE compared to static to get a similar result. Some others do not use TE pressure and derive required input by inverting pitot signal electronically.

Having built a couple of transducer variometers, when using TE probe compensation, I simply differentiate the absolute TE pressure, static is not used in that case...

Marc

[Dickie Feakes[_2_]]

Another simpler explanation can be found on this link:

http://bas.uk.net/variofaq.html

Dickie

On 04/12/2014 19:02, Jim Lewis wrote:
> I have been trying to understand just how a TE probe functions.
>
> Is a TE probe plumbed as the only static source for a variometer or is it plumbed together with the static ports that are usually placed on the sides of a glider?
>
> Thank you.

[Jim Lewis[_2_]]

On Friday, December 5, 2014 1:19:59 PM UTC-8, Dickie Feakes wrote:
> Another simpler explanation can be found on this link:
>
> http://bas.uk.net/variofaq.html
>
> Dickie
>
Thank you Dickie. That's a very helpful explanation.

[krasw]

Most important thing in understanding how TE probe works is to understand that variometer does not care about the absolute pressure. It measures only pressure change over time. If you dive your glider, the static pressure rises. This is compensated by increasing negative pitot pressure (negative, because holes are at the wake of TE tube). These pressure components should be more or less equal and cancel each out, leaving only pressure change from aircraft polar sink and airmass movement.

[Jim Lewis[_2_]]

Good point! I'm sad to say that it has taken me several days to remember that the variometer, unlike the altimeter, is not concerned with absolute pressure, only with the relative pressure on both sides of the variometer.

[Jim Lewis[_2_]]

Thank you to all who have helped me sort out my understandings of how TE probes work.

My understanding has been blocked by my confusion over how a TE probe senses environmental static pressure. I know, dumb. This confusion led me down a dead end path of wondering just what pressure (total, dynamic, static) a TE probe presents to the static side of a variometer.

I read several souces on the subject and was further stumped by repeated statements that a TE probe must produce a pressure equal in magnitude but opposide in sign to the dynamic pressure sensed by the pitot probe. This just fed my confusion.

The veil has been lifted from my eyes - I hope. I understand now that the TE probe (and the pitot probe, for that matter) cannot help but sense static pressure - in addition to dynamic pressure. Static pressure, in a sense, is everywhere. It is, in a sense, the background pressure. The TE probe does sense static pressure; it cannot help but do so. But it also senses dynamic pressure (the inverse of it, actually). The TE probe 'adds' the inverse of dynamic pressure to the static pressure to moderate the static pressure changes that may accompany dynamic pressure changes. If the dynamic pressure is not changing the TE probe presents to the variometer the pressure it does sense - the unmodified static pressure, and so functions as a simple static probe. Again, in a sense, the TE probe, in the absence of dynamic pressure changes, 'adds' zero to the static pressure.

I hope I finally have this sorted out. If not, just shoot me.

[Dave Nadler]

On Saturday, December 6, 2014 12:27:42 AM UTC-5, krasw wrote:
> ... variometer does not care about the absolute pressure.

Really? What happens at 10,000 feet vs. sea level?
Discuss amongst yourselves...

[Jim Lewis[_2_]]

On Saturday, December 6, 2014 2:59:38 PM UTC-8, Dave Nadler wrote:
> On Saturday, December 6, 2014 12:27:42 AM UTC-5, krasw wrote:
> > ... variometer does not care about the absolute pressure.
>
> Really? What happens at 10,000 feet vs. sea level?
> Discuss amongst yourselves...

Well, let's see. The air is less dense at 10,000 MSL than it is at sea level. One formula for force is F = ma. This suggests the air flow through the variometer would produce less force at 10,000MSL than
it would at sea level. If the variometer is a vane-type variometer perhaps the variometer vane would not be moved as much at 10,000 MSL than it would be at sea level. So... the variometer would read less lift/drag at 10,000 MSL than it would at sea level? Just a guess. I really have no idea.

[Don Johnstone[_4_]]

At 22:59 06 December 2014, Dave Nadler wrote:
>On Saturday, December 6, 2014 12:27:42 AM UTC-5, krasw wrote:
>> ... variometer does not care about the absolute pressure.
>
>Really? What happens at 10,000 feet vs. sea level?
>Discuss amongst yourselves...
>
In it's most simplistic for a vario measures differences in pressure over
time. Again in the most simplistic form the instrument measures the rate of
flow of air from a sealed flask trying to equalise the pressure within it
to the outside air (static). It converts the rate of flow to give an
indication of the rate of climb/descent. In that respect it does not care
about the absolute pressure. Whether the reduced air density in the flow
will cause any detectable change in the indication is debatable, I can't
see why it should.

Modern electronic instruments calculate a rate by comparing minute
differences in pressure directly. If the instrument is measuring changes in
pressure then it relies on the absolute pressure value entirely. In this
type of instrument the altitude will make no difference.

[Dave Nadler]

On Saturday, December 6, 2014 12:55:05 PM UTC-5, Jim Lewis wrote:
> I understand now that the TE probe (and the pitot probe,
> for that matter) cannot help but sense static pressure -
> in addition to dynamic pressure.

Right! This is easy to understand by considering the pressure
sensed by TE or pitot probes with glider on the ground.

[Dan Marotta]

Seems to me that if the vario measures a volume rate of flow, then at
higher altitudes, for a given change in altitude, the change of pressure
would be less (recall that pressure change is non linear with altitude),
hence a lower volume flow, hence a lower rate of change reading (lift or
sink).

So, if I'm climbing at 10 kts at sea level and my vario reads 10 due to
some finite number of moles or molecules of gas exiting the flask, past
a sensor, to the atmosphere, I'd think that, at 18,000' MSL where the
static pressure is roughly half what it is at sea level, then the volume
of air leaving the flask and passing the sensor would be roughly half of
what it was at sea level, then an absolute climb rate of 10 kts would be
displayed at something more like 5 kts. It probably doesn't make a damn
bit of difference anyway.

Flash update! I passed this by my wife (who's a current student glider
pilot) and she opened the topic of indicated vs. true speed. I think
that's the answer. We'll be reading an indicated 10kts regardless of
altitude but our true rate of climb will depend upon altitude. I think
that supports what I said above but I'd still like a mathematical
explanation.

Would somebody with an actual education in the subject please explain it
for the rest of us?

On 12/7/2014 7:39 AM, Dave Nadler wrote:
> On Saturday, December 6, 2014 12:55:05 PM UTC-5, Jim Lewis wrote:
>> I understand now that the TE probe (and the pitot probe,
>> for that matter) cannot help but sense static pressure -
>> in addition to dynamic pressure.
>
> Right! This is easy to understand by considering the pressure
> sensed by TE or pitot probes with glider on the ground.
>

--
---
Dan Marotta

[[email protected]]

On Sunday, December 7, 2014 11:46:38 AM UTC-5, Dan Marotta wrote:
> Seems to me that if the vario measures a volume rate of flow, then at
> higher altitudes, for a given change in altitude, the change of pressure
> would be less (recall that pressure change is non linear with altitude),
> hence a lower volume flow, hence a lower rate of change reading (lift or
> sink).
>
> So, if I'm climbing at 10 kts at sea level and my vario reads 10 due to
> some finite number of moles or molecules of gas exiting the flask, past
> a sensor, to the atmosphere, I'd think that, at 18,000' MSL where the
> static pressure is roughly half what it is at sea level, then the volume
> of air leaving the flask and passing the sensor would be roughly half of
> what it was at sea level, then an absolute climb rate of 10 kts would be
> displayed at something more like 5 kts. It probably doesn't make a damn
> bit of difference anyway.
>
> Flash update! I passed this by my wife (who's a current student glider
> pilot) and she opened the topic of indicated vs. true speed. I think
> that's the answer. We'll be reading an indicated 10kts regardless of
> altitude but our true rate of climb will depend upon altitude. I think
> that supports what I said above but I'd still like a mathematical
> explanation.
>
> Would somebody with an actual education in the subject please explain it
> for the rest of us?
>
> On 12/7/2014 7:39 AM, Dave Nadler wrote:
> > On Saturday, December 6, 2014 12:55:05 PM UTC-5, Jim Lewis wrote:
> >> I understand now that the TE probe (and the pitot probe,
> >> for that matter) cannot help but sense static pressure -
> >> in addition to dynamic pressure.
> >
> > Right! This is easy to understand by considering the pressure
> > sensed by TE or pitot probes with glider on the ground.
> >
>
> --
> ---
> Dan Marotta

What you have described is generally correct for FLOW type variometers such as mechanical instruments and early electric instruments. Almost all modern electric varios use pressure transducers and do not have the change in flow volume to consider.
UH

[Dave Nadler]

On Sunday, December 7, 2014 12:55:57 PM UTC-5, wrote:
> What you have described is generally correct for FLOW
> type variometers such as mechanical instruments and early
> electric instruments.

How you sense the pressure is unimportant.

The pressure change between 0 and 1 feet MSL is much larger
than the pressure difference between 10,000 and 10,001 feet MSL.

Discuss amongst yourselves...

[[email protected]]

On Sunday, December 7, 2014 10:16:45 AM UTC-8, Dave Nadler wrote:
> How you sense the pressure is unimportant.
>
> The pressure change between 0 and 1 feet MSL is much larger
> than the pressure difference between 10,000 and 10,001 feet MSL.
>
> Discuss amongst yourselves...

Looking at my decade old code for a transducer based variometer, I see that I went to a bit of trouble to convert pressure to ISA altitude before differentiating to get rate of climb. For even more amusement, consider the relationships between "altitude corrected" rate of climb, IAS, TAS, calculated total energy compensation, and speed to fly...

Marc

[Dave Nadler]

On Sunday, December 7, 2014 1:56:25 PM UTC-5, wrote:
> Looking at my decade old code for a transducer based variometer,
> I see that I went to a bit of trouble to convert pressure to ISA
> altitude before differentiating to get rate of climb.

Good, but its much easier just to correct by one_over_sigma ;-)

> For even more amusement, consider the relationships between
> "altitude corrected" rate of climb, IAS, TAS, calculated total
> energy compensation, and speed to fly...

Right, proper instruments consider MC as a 'true' input as
well as correcting vario, IAS->TAS, and of course polar.

Discuss amongst yourselves ;-)

[Dan Marotta]

....And it's not even officially winter yet...

OK, I understand about correcting the transducer based altitude,
corrected for ISA, so I guess you're using your static and OAT inputs to
calculate altitude before calculating and displaying the rate of change.

So am I to understand, then, that my mechanical vario is displaying
*indicated* rate of lift/sink while my electronic vario is displaying
*true* rate of lift/sink? I guess I'll take a close look on my next
wave flight.

On 12/7/2014 12:03 PM, Dave Nadler wrote:
> On Sunday, December 7, 2014 1:56:25 PM UTC-5, wrote:
>> Looking at my decade old code for a transducer based variometer,
>> I see that I went to a bit of trouble to convert pressure to ISA
>> altitude before differentiating to get rate of climb.
>
> Good, but its much easier just to correct by one_over_sigma ;-)
>
>> For even more amusement, consider the relationships between
>> "altitude corrected" rate of climb, IAS, TAS, calculated total
>> energy compensation, and speed to fly...
>
> Right, proper instruments consider MC as a 'true' input as
> well as correcting vario, IAS->TAS, and of course polar.
>
> Discuss amongst yourselves ;-)
>

--
---
Dan Marotta

[Don Johnstone[_4_]]

At 19:03 07 December 2014, Dave Nadler wrote:
>On Sunday, December 7, 2014 1:56:25 PM UTC-5, wrote:
>> Looking at my decade old code for a transducer based variometer,
>> I see that I went to a bit of trouble to convert pressure to ISA
>> altitude before differentiating to get rate of climb.
>
>Good, but its much easier just to correct by one_over_sigma ;-)
>
>> For even more amusement, consider the relationships between
>> "altitude corrected" rate of climb, IAS, TAS, calculated total
>> energy compensation, and speed to fly...
>
>Right, proper instruments consider MC as a 'true' input as
>well as correcting vario, IAS->TAS, and of course polar.
>
>Discuss amongst yourselves ;-)

Seems to me that this discussion is about a complete non problem. When we
"read" a vario we are not really interested in the arbitrary figure it
displays but more in the fact of whether the value is higher or lower than
the previous value.
In other words if 4kts is really 2kts at 10,000 ft it does not matter a jot
to us. What does matter is that 4kts will always be greater than 2kts. We
search for better lift not some arbitrary figure.

[[email protected]]

On Sunday, December 7, 2014 12:00:08 PM UTC-8, Dan Marotta wrote:
> ...And it's not even officially winter yet...

Well, it's raining here in northern California, I can't even work on our winch 8^(

> OK, I understand about correcting the transducer based altitude,
> corrected for ISA, so I guess you're using your static and OAT inputs to
> calculate altitude before calculating and displaying the rate of change.

Actually, OAT isn't used to convert pressure to ISA altitude, as what matters is the mean temperature of the column of air between your altitude and sea level, not OAT at that altitude. So, one would need to drop periodic sounding probes to correct for "true" altitude, but just applying a basic mapping from pressure to ISA altitude (or one_over_sigma as Dave indicated) is "good enough" for our purposes (if one wants to know the actual altitude, as such, applying a QNH or QFF setting gets you closer, yet). Likewise, for a transducer variometer hooked to a TE probe, static pressure is typically not used, instead one ends up with effectively "total energy altitude" (where you would end up if you could convert all (?) of your airspeed to altitude), which is again "good enough".

>
> So am I to understand, then, that my mechanical vario is displaying
> *indicated* rate of lift/sink while my electronic vario is displaying
> *true* rate of lift/sink? I guess I'll take a close look on my next
> wave flight.

I think it may be a bit more complicated than that, but I've never really thought about what a mechanical flow-based variometer actually measures...

Marc

[Dave Nadler]

On Sunday, December 7, 2014 3:30:05 PM UTC-5, Don Johnstone wrote:
> Seems to me that this discussion is about a complete non problem. When we
> "read" a vario we are not really interested in the arbitrary figure it
> displays but more in the fact of whether the value is higher or lower than
> the previous value.
> In other words if 4kts is really 2kts at 10,000 ft it does not matter a jot
> to us. What does matter is that 4kts will always be greater than 2kts. We
> search for better lift not some arbitrary figure.

No, it is important to know climb strength to accurately set
speed-to-fly, MC or otherwise derived, for both inter-thermal
cruise and final glide.

All this is well-covered in Reichmann...

[Dan Marotta]

What I meant to say concerning OAT is that it's used in computing TAS
(horizontal or vertical).

I also agree with Don in that I'm really only concerned with "more"
rather than "how much".

Still, just for jollies, I'm going to compare my mechanical vs
electronic varios just to see if the difference between the two
increases with altitude.

On 12/7/2014 1:25 PM, wrote:
> On Sunday, December 7, 2014 12:00:08 PM UTC-8, Dan Marotta wrote:
>> ...And it's not even officially winter yet...
>
> Well, it's raining here in northern California, I can't even work on our winch 8^(
>
>> OK, I understand about correcting the transducer based altitude,
>> corrected for ISA, so I guess you're using your static and OAT inputs to
>> calculate altitude before calculating and displaying the rate of change.
>
> Actually, OAT isn't used to convert pressure to ISA altitude, as what matters is the mean temperature of the column of air between your altitude and sea level, not OAT at that altitude. So, one would need to drop periodic sounding probes to correct for "true" altitude, but just applying a basic mapping from pressure to ISA altitude (or one_over_sigma as Dave indicated) is "good enough" for our purposes (if one wants to know the actual altitude, as such, applying a QNH or QFF setting gets you closer, yet). Likewise, for a transducer variometer hooked to a TE probe, static pressure is typically not used, instead one ends up with effectively "total energy altitude" (where you would end up if you could convert all (?) of your airspeed to altitude), which is again "good enough".
>
>>
>> So am I to understand, then, that my mechanical vario is displaying
>> *indicated* rate of lift/sink while my electronic vario is displaying
>> *true* rate of lift/sink? I guess I'll take a close look on my next
>> wave flight.
>
> I think it may be a bit more complicated than that, but I've never really thought about what a mechanical flow-based variometer actually measures...
>
> Marc
>

--
---
Dan Marotta

[krasw]

On Sunday, 7 December 2014 00:59:38 UTC+2, Dave Nadler wrote:
> On Saturday, December 6, 2014 12:27:42 AM UTC-5, krasw wrote:
> > ... variometer does not care about the absolute pressure.
>
> Really? What happens at 10,000 feet vs. sea level?

Since the variometer flask contains same 10000 feet air, the speed of airflow trough variometer would be exactly same, in that sence it does not care. Depending on vario design, the force turning variometer vane could be less.. All of this (incl. temperature) is easily compensated in electric vario.

> Discuss amongst yourselves...

Seems to me that you are participating this a lot, after all.

[Dave Nadler]

On Monday, December 8, 2014 5:01:59 AM UTC-5, krasw wrote:
> On Sunday, 7 December 2014 00:59:38 UTC+2, Dave Nadler wrote:
> > On Saturday, December 6, 2014 12:27:42 AM UTC-5, krasw wrote:
> > > ... variometer does not care about the absolute pressure.
> >
> > Really? What happens at 10,000 feet vs. sea level?
>
> Since the variometer flask contains same 10000 feet air...

Really? Isn't the air less dense at 10,000 feet than at sea level??

Discuss amongst yourselves...

[krasw]

maanantai, 8. joulukuuta 2014 15.04.33 UTC+2 Dave Nadler kirjoitti:
> On Monday, December 8, 2014 5:01:59 AM UTC-5, krasw wrote:
> > On Sunday, 7 December 2014 00:59:38 UTC+2, Dave Nadler wrote:
> > > On Saturday, December 6, 2014 12:27:42 AM UTC-5, krasw wrote:
> > > > ... variometer does not care about the absolute pressure.
> > >
> > > Really? What happens at 10,000 feet vs. sea level?
> >
> > Since the variometer flask contains same 10000 feet air...
>
> Really? Isn't the air less dense at 10,000 feet than at sea level??
>
> Discuss amongst yourselves...

Are you aware that you are clinging on a detail that is quite irrevelant when talking about the very basics of TE probe? What's next, shall we go trough air density vs. humidity relation? Isn't it annoying that every sentence I write is a question?

[Dave Nadler]

On Thursday, December 4, 2014 2:02:55 PM UTC-5, Jim Lewis wrote:
> I have been trying to understand just how a TE probe functions.

Hi Jim - I hope the RAS nonsense has not discouraged your quest
for knowledge! Get yourself a copy of Helmut Reichmann's "Cross-
Country Soaring". Instrumentation functions are covered in a
practical and readable fashion, including of course TE probes.
The book is also a fabulous overview of XC soaring basics.
Enjoy!
Best Regards, Dave

PS: Beware answers you get on RAS! Way too many people happy
to provide incomplete and/or incorrect answers with a solemn
tone of authority...

PPS: If you want to dig into the math, beware that early editions
of Reichmann's book have the terms for some of the equations
translated incorrectly (equations are correct but explanations
of the terms are not).

[[email protected]]

On Wednesday, December 10, 2014 10:57:08 AM UTC-5, Dave Nadler wrote:
> On Thursday, December 4, 2014 2:02:55 PM UTC-5, Jim Lewis wrote:
> > I have been trying to understand just how a TE probe functions.
>
> Hi Jim - I hope the RAS nonsense has not discouraged your quest
> for knowledge! Get yourself a copy of Helmut Reichmann's "Cross-
> Country Soaring". Instrumentation functions are covered in a
> practical and readable fashion, including of course TE probes.
> The book is also a fabulous overview of XC soaring basics.
> Enjoy!
> Best Regards, Dave
>
> PS: Beware answers you get on RAS! Way too many people happy
> to provide incomplete and/or incorrect answers with a solemn
> tone of authority...
>
> PPS: If you want to dig into the math, beware that early editions
> of Reichmann's book have the terms for some of the equations
> translated incorrectly (equations are correct but explanations
> of the terms are not).

Now you warn me! Today I replaced the venturi style TE probe with an ILEC fin mounted probe in fashionable blue anodized color. I measured thrice and cut once based on this thread's info. You guys better be right!

Lane
XF

[Jim Lewis[_2_]]

Hi Dave,

I'm not at all discouraged! I've learned a lot and I think I now actually understand the TE system.
I have Reichmann's books and many others too. Sometimes I'm too thick to understand what is being discussed but I keep trying. Thank you for your help.

Jim