Motorgliders and TE Probes

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

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

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

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

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/displa...asp?sku=MJTV-5

For additonal info on pneumatic valves, see,
http://www.clippard.com/downloads/ge...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

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

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

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

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)