Motorgliders and TE Probes

[Paul Remde]

Hi,

I have a question for motorglider owners. I sell variometers and TE probes
but I'm still learning. A customer is building a Europa motorglider and he
is wondering if he can mount a TE probe on the fin and connect it to the
variometer, or will the propwash cause problems. Is it necessary to use
some sort of pneumatic switch to switch between TE and static input for the
variometer?

His pitot and static ports are on a boom that is mounted to the wing.

Thank you,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com

[Stefan]

Paul Remde wrote:

> is wondering if he can mount a TE probe on the fin and connect it to the
> variometer, or will the propwash cause problems.

The vario will not be too accurate in the propwash, but who needs an
accurate vario when the prop is turning?

> Is it necessary to use
> some sort of pneumatic switch to switch between TE and static input for the
> variometer?

Not necessary, but recommended.

Stefan

[Paul Remde]

Hi,

I received a few very nice e-mails from reputable sources recommending the
use of a pneumatic switch to switch between TE and Static input for a
motorglider. That is good information. This newsgroup is fantastic!

It was suggested that the switch could be made to be automatic. That sounds
great. It is my understanding that even very small leaks can cause large
inaccuracies in TE functionality - so we must be careful about that of
course. Does anyone have any recommendations for manual or automatic
pneumatic switches? It would be great to get feedback from someone who has
done this already.

Thank you,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com

"Paul Remde" > wrote in message
news:NwKod.141170$R05.69144@attbi_s53...
> Hi,
>
> I have a question for motorglider owners. I sell variometers and TE
probes
> but I'm still learning. A customer is building a Europa motorglider and
he
> is wondering if he can mount a TE probe on the fin and connect it to the
> variometer, or will the propwash cause problems. Is it necessary to use
> some sort of pneumatic switch to switch between TE and static input for
the
> variometer?
>
> His pitot and static ports are on a boom that is mounted to the wing.
>
> Thank you,
>
> Paul Remde
> Cumulus Soaring, Inc.
> http://www.cumulus-soaring.com
>
>

[Steve Hill]

I think most of the newer variometer systems can electronically calculate
total energy, without the need for any TE probe...I have tried this and
while I haven't met with great success in comparison to using an actual TE
probe on my DG-400, I would speculate that the Europa is not going to be
high enough performing to know the difference in the very minor differences
between a probe and what the vario system will electronically compensate. I
will say that when I tried the electronic setup in my DG, there was a gust
filter the previous owner had installed, which I didn't know about until
later...after removing that filter, my TE probe was much more accurate, but
my guess is that electronically I could have compensated the system fairly
accurately.

Steve.

[Raphael Warshaw]

Paul:

I got a nice manual pneumatic switch for use in my oxygen system from
Mountain High a few years ago. You might check with them.

Ray Warshaw

"Paul Remde" > wrote in message
news:f%Lod.141383$R05.121337@attbi_s53...
> Hi,
>
> I received a few very nice e-mails from reputable sources recommending the
> use of a pneumatic switch to switch between TE and Static input for a
> motorglider. That is good information. This newsgroup is fantastic!
>
> It was suggested that the switch could be made to be automatic. That
> sounds
> great. It is my understanding that even very small leaks can cause large
> inaccuracies in TE functionality - so we must be careful about that of
> course. Does anyone have any recommendations for manual or automatic
> pneumatic switches? It would be great to get feedback from someone who
> has
> done this already.
>
> Thank you,
>
> Paul Remde
> Cumulus Soaring, Inc.
> http://www.cumulus-soaring.com
>
> "Paul Remde" > wrote in message
> news:NwKod.141170$R05.69144@attbi_s53...
>> Hi,
>>
>> I have a question for motorglider owners. I sell variometers and TE
> probes
>> but I'm still learning. A customer is building a Europa motorglider and
> he
>> is wondering if he can mount a TE probe on the fin and connect it to the
>> variometer, or will the propwash cause problems. Is it necessary to use
>> some sort of pneumatic switch to switch between TE and static input for
> the
>> variometer?
>>
>> His pitot and static ports are on a boom that is mounted to the wing.
>>
>> Thank you,
>>
>> Paul Remde
>> Cumulus Soaring, Inc.
>> http://www.cumulus-soaring.com
>>
>>
>
>

[Eric Greenwell]

Paul Remde wrote:
> Hi,
>
> I have a question for motorglider owners. I sell variometers and TE probes
> but I'm still learning. A customer is building a Europa motorglider and he
> is wondering if he can mount a TE probe on the fin and connect it to the
> variometer, or will the propwash cause problems.

The reading will bounce around, but usable except when trying to center
weak lift while under power.

Is it necessary to use
> some sort of pneumatic switch to switch between TE and static input for the
> variometer?

It would likely help.

>
> His pitot and static ports are on a boom that is mounted to the wing.

Since he is building it, I suggest he consider a TE tube on the wing,
clear of the prop wash. That should be easy, since he is already doing
that with the pitot and static. Or, use a vario with electronic TE and
just use the pitot/static.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Gary Evans]

Miniature toggle routing valves are also available
through MSC Industrial Supply Co. mail order.

This is page 3950 of their on-line PDF catalog. Note
the routing valve at mid-page.

http://tinyurl.com/5hv9o

This is their web site.

http://tinyurl.com/629x5




At 20:30 23 November 2004, Tim Mara wrote:
>Clippard Industries in Cincinnati Ohio makes several
>types of Pneumatic
>switches.....
>these were commonly used years ago back when sailplane
>pilots used to have
>to make their own and a few variometer manufacturers
>like Richard Ball made
>alternative Pneumatic inputs for Netto's and Speed
>to Fly variometers from
>normal TE variometers
>tim
>
>'Paul Remde' wrote in message
>news:f%Lod.141383$R05.121337@attbi_s53...
>> Hi,
>>
>> I received a few very nice e-mails from reputable
>>sources recommending the
>> use of a pneumatic switch to switch between TE and
>>Static input for a
>> motorglider. That is good information. This newsgroup
>>is fantastic!
>>
>> It was suggested that the switch could be made to
>>be automatic. That
>> sounds
>> great. It is my understanding that even very small
>>leaks can cause large
>> inaccuracies in TE functionality - so we must be careful
>>about that of
>> course. Does anyone have any recommendations for
>>manual or automatic
>> pneumatic switches? It would be great to get feedback
>>from someone who
>> has
>> done this already.
>>
>> Thank you,
>>
>> Paul Remde
>> Cumulus Soaring, Inc.
>> http://www.cumulus-soaring.com
>>
>> 'Paul Remde' wrote in message
>> news:NwKod.141170$R05.69144@attbi_s53...
>>> Hi,
>>>
>>> I have a question for motorglider owners. I sell
>>>variometers and TE
>> probes
>>> but I'm still learning. A customer is building a
>>>Europa motorglider and
>> he
>>> is wondering if he can mount a TE probe on the fin
>>>and connect it to the
>>> variometer, or will the propwash cause problems.
>>>Is it necessary to use
>>> some sort of pneumatic switch to switch between TE
>>>and static input for
>> the
>>> variometer?
>>>
>>> His pitot and static ports are on a boom that is mounted
>>>to the wing.
>>>
>>> Thank you,
>>>
>>> Paul Remde
>>> Cumulus Soaring, Inc.
>>> http://www.cumulus-soaring.com
>>>
>>>
>>
>>
>
>
>
>

[Brian Case]

My Guess on the Europa is that with the front mounted Propeller and
the rather High Vertical Tail, He could just mount it has High as
possible on the Vertical fin and have little problem with the TE Prob.
I suspect that most of the prop wash would miss the TE prob anyway.

Brian

[John Giddy]

On Tue, 23 Nov 2004 14:49:21 -0800, Tim Mara wrote:

> Clippard Industries in Cincinnati Ohio makes several types of Pneumatic
> switches.....
> these were commonly used years ago back when sailplane pilots used to have
> to make their own and a few variometer manufacturers like Richard Ball made
> alternative Pneumatic inputs for Netto's and Speed to Fly variometers from
> normal TE variometers
> tim
>
> "Paul Remde" > wrote in message
> news:f%Lod.141383$R05.121337@attbi_s53...
>> Hi,
>>
>> I received a few very nice e-mails from reputable sources recommending the
>> use of a pneumatic switch to switch between TE and Static input for a
>> motorglider. That is good information. This newsgroup is fantastic!
>>
>> It was suggested that the switch could be made to be automatic. That
>> sounds
>> great. It is my understanding that even very small leaks can cause large
>> inaccuracies in TE functionality - so we must be careful about that of
>> course. Does anyone have any recommendations for manual or automatic
>> pneumatic switches? It would be great to get feedback from someone who
>> has
>> done this already.
>>
>> Thank you,
>>
>> Paul Remde
>> Cumulus Soaring, Inc.
>> http://www.cumulus-soaring.com
>>
>> "Paul Remde" > wrote in message
>> news:NwKod.141170$R05.69144@attbi_s53...
>>> Hi,
>>>
>>> I have a question for motorglider owners. I sell variometers and TE
>> probes
>>> but I'm still learning. A customer is building a Europa motorglider and
>> he
>>> is wondering if he can mount a TE probe on the fin and connect it to the
>>> variometer, or will the propwash cause problems. Is it necessary to use
>>> some sort of pneumatic switch to switch between TE and static input for
>> the
>>> variometer?
>>>
>>> His pitot and static ports are on a boom that is mounted to the wing.
>>>
>>> Thank you,
>>>
>>> Paul Remde
>>> Cumulus Soaring, Inc.
>>> http://www.cumulus-soaring.com
>>>
>>>
>>
>>

I mounted a vertical TE Probe on the top of the fin on our SF25C FALKE
motorglider, connected to a dedicated vario (Borgelt B40). The
aircraft already had a Winter vario connected directly to the static
ports which acts more like a VSI.
The TE probe seems to work very well. The sensing holes near the tip
of the probe would be (from memory) about 10 inces above the top of
the fin.
Regarding switches to change from static to TE, many GA aircraft use
such switches to give an alternative static source for the instruments
in case the primary static ports become blocked. Maybe one of the
aircraft supply houses would have them.
Cheers, John G.

[Tim Mara]

Clippard Industries in Cincinnati Ohio makes several types of Pneumatic
switches.....
these were commonly used years ago back when sailplane pilots used to have
to make their own and a few variometer manufacturers like Richard Ball made
alternative Pneumatic inputs for Netto's and Speed to Fly variometers from
normal TE variometers
tim

"Paul Remde" > wrote in message
news:f%Lod.141383$R05.121337@attbi_s53...
> Hi,
>
> I received a few very nice e-mails from reputable sources recommending the
> use of a pneumatic switch to switch between TE and Static input for a
> motorglider. That is good information. This newsgroup is fantastic!
>
> It was suggested that the switch could be made to be automatic. That
> sounds
> great. It is my understanding that even very small leaks can cause large
> inaccuracies in TE functionality - so we must be careful about that of
> course. Does anyone have any recommendations for manual or automatic
> pneumatic switches? It would be great to get feedback from someone who
> has
> done this already.
>
> Thank you,
>
> Paul Remde
> Cumulus Soaring, Inc.
> http://www.cumulus-soaring.com
>
> "Paul Remde" > wrote in message
> news:NwKod.141170$R05.69144@attbi_s53...
>> Hi,
>>
>> I have a question for motorglider owners. I sell variometers and TE
> probes
>> but I'm still learning. A customer is building a Europa motorglider and
> he
>> is wondering if he can mount a TE probe on the fin and connect it to the
>> variometer, or will the propwash cause problems. Is it necessary to use
>> some sort of pneumatic switch to switch between TE and static input for
> the
>> variometer?
>>
>> His pitot and static ports are on a boom that is mounted to the wing.
>>
>> Thank you,
>>
>> Paul Remde
>> Cumulus Soaring, Inc.
>> http://www.cumulus-soaring.com
>>
>>
>
>

[Doug Easton]

Paul,

Yes you need a pneumatic switch, basically it turns your TE vario into a
VSI. I had both my LNAV and Sage behind the pneumatic switch and found that
the changeover between static pressure and TE pressure wrecks the sage (not
nice watching it spin round and round). I moved the sage in front of the
switch so it gets TE pressure all the time, it's uselesss when the engine is
running (the LNAV indicates vertical speed just fine) but at least it's a
little kinder to the instrument.

Doug


"Paul Remde" > wrote in message
news:NwKod.141170$R05.69144@attbi_s53...
> Hi,
>
> I have a question for motorglider owners. I sell variometers and TE
> probes
> but I'm still learning. A customer is building a Europa motorglider and
> he
> is wondering if he can mount a TE probe on the fin and connect it to the
> variometer, or will the propwash cause problems. Is it necessary to use
> some sort of pneumatic switch to switch between TE and static input for
> the
> variometer?
>
> His pitot and static ports are on a boom that is mounted to the wing.
>
> Thank you,
>
> Paul Remde
> Cumulus Soaring, Inc.
> http://www.cumulus-soaring.com
>
>

[Bert Willing]

A TE probe on a wing would certainly be a very bad idea as the pressure
field near the wing will not show linear variations with angle of attack...

--
Bert Willing

ASW20 "TW"


"Eric Greenwell" > a écrit dans le message de news:
...
> Paul Remde wrote:
>> Hi,
>>
>> I have a question for motorglider owners. I sell variometers and TE
>> probes
>> but I'm still learning. A customer is building a Europa motorglider and
>> he
>> is wondering if he can mount a TE probe on the fin and connect it to the
>> variometer, or will the propwash cause problems.
>
> The reading will bounce around, but usable except when trying to center
> weak lift while under power.
>
> Is it necessary to use
>> some sort of pneumatic switch to switch between TE and static input for
>> the
>> variometer?
>
> It would likely help.
>
>>
>> His pitot and static ports are on a boom that is mounted to the wing.
>
> Since he is building it, I suggest he consider a TE tube on the wing,
> clear of the prop wash. That should be easy, since he is already doing
> that with the pitot and static. Or, use a vario with electronic TE and
> just use the pitot/static.
>
> --
> Change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA
>

[Paul Remde]

Hi,

Is angle of attack a big part of TE compensation? I thought it was mainly
pressure changes due to airspeed changes. I'll have to do some reading on
this. I think New Soaring Pilot by Welch and Irving has some good
information.

Thanks,

Paul Remde

"Bert Willing" > wrote in
message ...
> A TE probe on a wing would certainly be a very bad idea as the pressure
> field near the wing will not show linear variations with angle of
attack...
>
> --
> Bert Willing
>
> ASW20 "TW"
>
>
> "Eric Greenwell" > a écrit dans le message de
news:
> ...
> > Paul Remde wrote:
> >> Hi,
> >>
> >> I have a question for motorglider owners. I sell variometers and TE
> >> probes
> >> but I'm still learning. A customer is building a Europa motorglider
and
> >> he
> >> is wondering if he can mount a TE probe on the fin and connect it to
the
> >> variometer, or will the propwash cause problems.
> >
> > The reading will bounce around, but usable except when trying to center
> > weak lift while under power.
> >
> > Is it necessary to use
> >> some sort of pneumatic switch to switch between TE and static input for
> >> the
> >> variometer?
> >
> > It would likely help.
> >
> >>
> >> His pitot and static ports are on a boom that is mounted to the wing.
> >
> > Since he is building it, I suggest he consider a TE tube on the wing,
> > clear of the prop wash. That should be easy, since he is already doing
> > that with the pitot and static. Or, use a vario with electronic TE and
> > just use the pitot/static.
> >
> > --
> > Change "netto" to "net" to email me directly
> >
> > Eric Greenwell
> > Washington State
> > USA
> >
>
>

[Bert Willing]

Sorry if I gave reasons to misinterprete.
TE is based on pressure changes due to changes in speed (which in turn are
caused by changes of angle of attack). But you can expect the pressure
change to be significantly different in the vicinity of the wing, than in a
free flow section, so the TE would not read correctly for the whole range of
airspeed.

That's the reason why TE's are mounted either above the middle of the tail
boom, or something like half a meter in front of the wing.

--
Bert Willing

ASW20 "TW"


"Paul Remde" > a écrit dans le message de news:
pT0pd.79775$V41.37553@attbi_s52...
> Hi,
>
> Is angle of attack a big part of TE compensation? I thought it was mainly
> pressure changes due to airspeed changes. I'll have to do some reading on
> this. I think New Soaring Pilot by Welch and Irving has some good
> information.
>
> Thanks,
>
> Paul Remde
>
> "Bert Willing" > wrote in
> message ...
>> A TE probe on a wing would certainly be a very bad idea as the pressure
>> field near the wing will not show linear variations with angle of
> attack...
>>
>> --
>> Bert Willing
>>
>> ASW20 "TW"
>>
>>
>> "Eric Greenwell" > a écrit dans le message de
> news:
>> ...
>> > Paul Remde wrote:
>> >> Hi,
>> >>
>> >> I have a question for motorglider owners. I sell variometers and TE
>> >> probes
>> >> but I'm still learning. A customer is building a Europa motorglider
> and
>> >> he
>> >> is wondering if he can mount a TE probe on the fin and connect it to
> the
>> >> variometer, or will the propwash cause problems.
>> >
>> > The reading will bounce around, but usable except when trying to center
>> > weak lift while under power.
>> >
>> > Is it necessary to use
>> >> some sort of pneumatic switch to switch between TE and static input
>> >> for
>> >> the
>> >> variometer?
>> >
>> > It would likely help.
>> >
>> >>
>> >> His pitot and static ports are on a boom that is mounted to the wing.
>> >
>> > Since he is building it, I suggest he consider a TE tube on the wing,
>> > clear of the prop wash. That should be easy, since he is already doing
>> > that with the pitot and static. Or, use a vario with electronic TE and
>> > just use the pitot/static.
>> >
>> > --
>> > Change "netto" to "net" to email me directly
>> >
>> > Eric Greenwell
>> > Washington State
>> > USA
>> >
>>
>>
>
>

[Bob Gibbons]

I use a Clippard MJTV-5 pneumatic valve to switch out the TE probe on
my Ventus cT. This is a 5 port, 4 way valve. My notes from the install
indicate you connect the input to port 1, and the ouput is toggled
between ports 2 and 4, depending on the lever position. The exhaust
ports vent the non-operational port to ambient (or whatever you
connect to these ports). Cost is approx. $15 US.

For details, see,
http://www.clippard.com/store/display_details.asp?sku=MJTV-5

For additonal info on pneumatic valves, see,
http://www.clippard.com/downloads/general/PDF_Documents/Intro_to_Pneumatics.pdf

Bob


On Tue, 23 Nov 2004 19:15:23 GMT, "Paul Remde" > wrote:

>Hi,
>
>I received a few very nice e-mails from reputable sources recommending the
>use of a pneumatic switch to switch between TE and Static input for a
>motorglider. That is good information. This newsgroup is fantastic!
>
>It was suggested that the switch could be made to be automatic. That sounds
>great. It is my understanding that even very small leaks can cause large
>inaccuracies in TE functionality - so we must be careful about that of
>course. Does anyone have any recommendations for manual or automatic
>pneumatic switches? It would be great to get feedback from someone who has
>done this already.
>
>Thank you,
>
>Paul Remde
>Cumulus Soaring, Inc.
>http://www.cumulus-soaring.com
>
>"Paul Remde" > wrote in message
>news:NwKod.141170$R05.69144@attbi_s53...
>> Hi,
>>
>> I have a question for motorglider owners. I sell variometers and TE
>probes
>> but I'm still learning. A customer is building a Europa motorglider and
>he
>> is wondering if he can mount a TE probe on the fin and connect it to the
>> variometer, or will the propwash cause problems. Is it necessary to use
>> some sort of pneumatic switch to switch between TE and static input for
>the
>> variometer?
>>
>> His pitot and static ports are on a boom that is mounted to the wing.
>>
>> Thank you,
>>
>> Paul Remde
>> Cumulus Soaring, Inc.
>> http://www.cumulus-soaring.com
>>
>>
>
>

[Ian Cant]

If the TE probe is mounted at half-span or more, will
any application of bank not cause a correctly-compensated
TE to read climb or descent [because the mounting point
is moving up or down as bank is applied] ? Is this
significant ?

Ian




At 15:31 24 November 2004, Bert Willing wrote:
>Sorry if I gave reasons to misinterprete.
>TE is based on pressure changes due to changes in speed
>(which in turn are
>caused by changes of angle of attack). But you can
>expect the pressure
>change to be significantly different in the vicinity
>of the wing, than in a
>free flow section, so the TE would not read correctly
>for the whole range of
>airspeed.
>
>That's the reason why TE's are mounted either above
>the middle of the tail
>boom, or something like half a meter in front of the
>wing.
>
>--
>Bert Willing
>
>ASW20 'TW'
>
>
>'Paul Remde' a écrit dans le message de news:
>pT0pd.79775$V41.37553@attbi_s52...
>> Hi,
>>
>> Is angle of attack a big part of TE compensation?
>> I thought it was mainly
>> pressure changes due to airspeed changes. I'll have
>>to do some reading on
>> this. I think New Soaring Pilot by Welch and Irving
>>has some good
>> information.
>>
>> Thanks,
>>
>> Paul Remde
>>
>> 'Bert Willing' wrote in
>> message ...
>>> A TE probe on a wing would certainly be a very bad
>>>idea as the pressure
>>> field near the wing will not show linear variations
>>>with angle of
>> attack...
>>>
>>> --
>>> Bert Willing
>>>
>>> ASW20 'TW'
>>>
>>>
>>> 'Eric Greenwell' a écrit dans le message de
>> news:
>>> ...
>>> > Paul Remde wrote:
>>> >> Hi,
>>> >>
>>> >> I have a question for motorglider owners. I sell
>>>>>variometers and TE
>>> >> probes
>>> >> but I'm still learning. A customer is building a
>>>>>Europa motorglider
>> and
>>> >> he
>>> >> is wondering if he can mount a TE probe on the fin
>>>>>and connect it to
>> the
>>> >> variometer, or will the propwash cause problems.
>>> >
>>> > The reading will bounce around, but usable except
>>>>when trying to center
>>> > weak lift while under power.
>>> >
>>> > Is it necessary to use
>>> >> some sort of pneumatic switch to switch between TE
>>>>>and static input
>>> >> for
>>> >> the
>>> >> variometer?
>>> >
>>> > It would likely help.
>>> >
>>> >>
>>> >> His pitot and static ports are on a boom that is
>>>>>mounted to the wing.
>>> >
>>> > Since he is building it, I suggest he consider a
>>>>TE tube on the wing,
>>> > clear of the prop wash. That should be easy, since
>>>>he is already doing
>>> > that with the pitot and static. Or, use a vario with
>>>>electronic TE and
>>> > just use the pitot/static.
>>> >
>>> > --
>>> > Change 'netto' to 'net' to email me directly
>>> >
>>> > Eric Greenwell
>>> > Washington State
>>> > USA
>>> >
>>>
>>>
>>
>>
>
>
>

[John Galloway]

I think it would cause significant errors because there
are unavoidable but detectable errors in fin mounted
TE probes from the relative but small downwards motion
of the tail end of the glider as you pull up (in addition
to the g effects). The relative motion would be much
greater between the fuselage and mid span in rolling
than between the fin and centre of rotation in pitching.

The best place for a TE probe that is not on the fin
would be far in front of the nose. In that position
the vertical movement effects would counteract the
g effects.

John Galloway


At 22:30 25 November 2004, Ian Cant wrote:
>If the TE probe is mounted at half-span or more, will
>any application of bank not cause a correctly-compensated
>TE to read climb or descent [because the mounting point
>is moving up or down as bank is applied] ? Is this
>significant ?
>
>Ian
>
>
>
>At 15:31 24 November 2004, Bert Willing wrote:
>>Sorry if I gave reasons to misinterprete.
>>TE is based on pressure changes due to changes in speed
>>(which in turn are
>>caused by changes of angle of attack). But you can
>>expect the pressure
>>change to be significantly different in the vicinity
>>of the wing, than in a
>>free flow section, so the TE would not read correctly
>>for the whole range of
>>airspeed.
>>
>>That's the reason why TE's are mounted either above
>>the middle of the tail
>>boom, or something like half a meter in front of the
>>wing.
>>
>>--
>>Bert Willing
>>
>>ASW20 'TW'
>>
>>
>>'Paul Remde' a écrit dans le message de news:
>>pT0pd.79775$V41.37553@attbi_s52...
>>> Hi,
>>>
>>> Is angle of attack a big part of TE compensation?
>>> I thought it was mainly
>>> pressure changes due to airspeed changes. I'll have
>>>to do some reading on
>>> this. I think New Soaring Pilot by Welch and Irving
>>>has some good
>>> information.
>>>
>>> Thanks,
>>>
>>> Paul Remde
>>>
>>> 'Bert Willing' wrote in
>>> message ...
>>>> A TE probe on a wing would certainly be a very bad
>>>>idea as the pressure
>>>> field near the wing will not show linear variations
>>>>with angle of
>>> attack...
>>>>
>>>> --
>>>> Bert Willing
>>>>
>>>> ASW20 'TW'
>>>>
>>>>
>>>> 'Eric Greenwell' a écrit dans le message de
>>> news:
>>>> ...
>>>> > Paul Remde wrote:
>>>> >> Hi,
>>>> >>
>>>> >> I have a question for motorglider owners. I
>>>>>>sell
>>>>>>variometers and TE
>>>> >> probes
>>>> >> but I'm still learning. A customer is building
>>>>>>a
>>>>>>Europa motorglider
>>> and
>>>> >> he
>>>> >> is wondering if he can mount a TE probe on the
>>>>>>fin
>>>>>>and connect it to
>>> the
>>>> >> variometer, or will the propwash cause problems.
>>>> >
>>>> > The reading will bounce around, but usable except
>>>>>when trying to center
>>>> > weak lift while under power.
>>>> >
>>>> > Is it necessary to use
>>>> >> some sort of pneumatic switch to switch between
>>>>>>TE
>>>>>>and static input
>>>> >> for
>>>> >> the
>>>> >> variometer?
>>>> >
>>>> > It would likely help.
>>>> >
>>>> >>
>>>> >> His pitot and static ports are on a boom that
>>>>>>is
>>>>>>mounted to the wing.
>>>> >
>>>> > Since he is building it, I suggest he consider a
>>>>>TE tube on the wing,
>>>> > clear of the prop wash. That should be easy, since
>>>>>he is already doing
>>>> > that with the pitot and static. Or, use a vario with
>>>>>electronic TE and
>>>> > just use the pitot/static.
>>>> >
>>>> > --
>>>> > Change 'netto' to 'net' to email me directly
>>>> >
>>>> > Eric Greenwell
>>>> > Washington State
>>>> > USA
>>>> >
>>>>
>>>>
>>>
>>>
>>
>>
>>
>
>
>
>

[Eric Greenwell]

Bert Willing wrote:
> Sorry if I gave reasons to misinterprete.
> TE is based on pressure changes due to changes in speed (which in turn are
> caused by changes of angle of attack). But you can expect the pressure
> change to be significantly different in the vicinity of the wing, than in a
> free flow section, so the TE would not read correctly for the whole range of
> airspeed.
>
> That's the reason why TE's are mounted either above the middle of the tail
> boom, or something like half a meter in front of the wing.

I didn't think about this effect when I made the suggestion; however, I
think the builder should install one in the tail and one on the wing, as
it won't cost very much. The tail TE probe will surely work for gliding,
and might be OK under power; the wing TE probe might work all the time,
or at least, it might be better than the statics if the tail TE probe
isn't good under power. The speed range of the Europa while gliding is
likely small enough that a superb TE system is not required.


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[PSUSOAR]

Yes, it is necessary to have a switch that toggles between TE (free flight) &
Static (engine runs). If the TE is used during an engine start the vario
needle pegs up very hard and could cause damage. I use a panel mounted Clippard
Mini-Matic with a toggle switch (previously in a Ventus BT) and currently in my
Nimbus 3T. Clippard has a great web-site and their dealer list is also
provided. After finding the correct size, just call a dealer and they will UPS
one to you.

Steve (PSU)