Marske Flying Wings wrote:

I did a modest cross country in the Pioneer IId yesterday but what is most
interesting was that I am exploring all of the flight envelope and yesterday
was stalls. When I pulled the stick all the way back slowly I suddenly found
that my airspeed had fallen to zero where I held it for quite some time and
my sink rate was 100 down. And I have it on video! I did this many times
although there was tendency to turn to the left since we have a left turn in
the glider.

The airspeed system was calibrated recently, both the airspeed instrument
and the installation, however I did not do the calibration for zero
airspeed... so it could be off slightly.

I have posted a picture on the web site showing the airspeed near zero and
will post a video shortly.

http://www.continuo.com/marske/pione...%20pioneer.htm

This is rather a long address so if this does not work go to our web site
and find "Marske Pioneer IId"

-mat

I have been recording all of this on video to give some credibillity to my
claims.
--
Marske Flying Wings
http://www.continuo.com/marske

A zero speed indication is not surprising in these conditions, and doesn't
mean the speed (or even its horizontal component) is zero, but rather that
the pitot tube used by the ASI for total pressure is no more at the stagnation
point in these conditions and so you don't get the true total pressure. I guess
that the pitot is in the nose and when near stall angle the stagnation point
is well below, with a nice round nose like on the Pioneer IId, the pitot may even
be at a point where the airflow is accelerated at a speed higher than the freestream
speed, so the pressure is lower than the static pressure and the ASI should show
a negative speed if it could. Isn't that the reason for what modern gliders with
a nose pitot have a sharp nose (ASW20, Pegases) and many other ones have a pitot
in the fin?