Motorgliders and TE Probes

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

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