Yaw-Free TEK Probes

Below is the response I got from Dr Smolik about his
intriguing new yaw free probes, which are surprisingly
a good bit cheaper than Esa probes. The advantages
of a probe free of yawing errors is obvious, especially
if you use the 'Holighous way' for thermalling (mildly
slipping your circles) as described by Johnson in the
Oct 04 issue of Soaring. Here is a link to the pdf
I was sent:
http://www.eaglebrandproducts.com/TE...rices_2006.pdf
and a link to the Youtube video I just posted showing
the swiveling action that is key to the probes yaw-free
performance: http://youtube.com/watch?v=OpN9sYHF_yc
I am awaiting the performance plots, and will post
them when I get them.

Paul Hanson


Dear Mr. Hanson,

many thanks for your mail which reached me here in
Europe across New Zealand.

ItŽs very pleasant for me to serve you some information
on my project.
The probes are manufactured in Germany in a more or
less individual manner according to the pilots wishes.

The major step forward is the yaw-free pressure measurement
of all three important pressures at same place and
time. Time to time there are discussions on web or
in articles in magazines about the yaw dependence of
the so called TE-pressure, which is normally taken
as a velocity dependent under pressure due to the
vorticity behind an particular object like e.g. a small
tube.
But such discussion is just a half truth ! ItŽs obvious
that beside the TE-under pressure the static and total
pressure are very sensitive for �yawing�
too. The new probe improves the measurement by rotating
around the yaw axis significantly.
If you are interested on results, I can provide plots.

But the tenor is: if a standard TEK-probe has an spread
in the probe coefficient of 10 or 20% due to yaw angel
or air turbulences, for the new probe such spread is
0%.

It is hard to make meaningful photographs of the probes
because they all are black and look boringJ) Therefore
I send you a short video where the functionality and
the free rotatability around the yaw axis is demonstrated.
The two prongs of the �Y� shape are
the tubes for the TE-measurement and the orifices
for total and static pressure are mounted in the small
antennas in the forward direction.

Of course , the probes fit to all standard adapters
or if desired to a new type of 3 way adapter, where
all the sealing o-rings are mounted and accessible
on probe itself.

One word to the results, in principle itŽs difficult
to compare probes really meaningful simply using a
flume. Normally the flume does not simulate either
real air conditions nor the glider influences and last
not least the individual pilots behaviour.
For this reason only a measurement on the same place
and at the same time on one glider with a same type
of electronics can provide the best and direct comparison..
For this purpose I made a probe with 2 x 3 independent
orifices. 3 orifices build a standard probe the other
3 orifices are build like the yaw-free probe. Feeding
the data to two independent vario circuits and logging
the results one obtain a flight �seen�
from two different probes. This experiment is still
in preparation and is foreseen for next spring.

I hope this short overview gives some helpful information


Best Regards

Ludek Smolik