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<DIV><FONT face=Arial size=2>Some of the slower full scale experimental craft
use a venturi arrangement to measure airspeed. The ram air pressure get pretty
small. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The nice part about this kind of experiment is that
you can hang it all out a car window...</FONT></DIV>
<DIV> </DIV>
<DIV>John Ferrell <BR><A
href="http://DixieNC.US">http://DixieNC.US</A><BR></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=bob@toprudder.com href="mailto:bob@toprudder.com">Bob Richards</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, January 14, 2005 10:30
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Pattern Help</DIV>
<DIV><BR></DIV>
<DIV>Earl,</DIV>
<DIV> </DIV>
<DIV>The 3/8" distance may not be enough. I suspect that in a stall/snap
situation that there is enough air "spilling" around the LE to disrupt the
operation of the pitot tube. (That's an over simplification, maybe) I
would try sticking it out maybe 2" or more just to try it out. Also, have you
tried snapping in both directions to see if you get the same readings?</DIV>
<DIV> </DIV>
<DIV>On most aircraft the pitot tube is fixed, but on
some test/experimental aircraft the pitot is mounted on a vane so it
always points directly into the airflow.</DIV>
<DIV> </DIV>
<DIV>I'm very interested in this. Keep us posted!!</DIV>
<DIV> </DIV>
<DIV>Bob R.</DIV>
<DIV><BR><BR><B><I>Earl Haury <ehaury@houston.rr.com></I></B>
wrote:</DIV>
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<DIV><FONT face=Arial size=2>Bob</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Correct on instrument methodology. You may be
correct regarding observed readings also. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>However, very high roll rates seem not to
generate the same speed reading effect. The pitot extends about 3/8" forward
the center of the wing LE in my installation. I've not seen any difference
in normal speed data with it varied 1/4" or so from that
position.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Pressure anomalies will definitely affect the
altitude sensor, however I don't see the same "signature" on downline snaps.
I've not been specifically looking at snaps to this point, the data were
generated flying the P-05 sequence. I plan to look at this further in a
different (more expendable) airplane with a G sensor also. Possibly that
sensor can be oriented to provide pitch load and thrust (longitudinal) accel
/ decel info. (Should receive sensor in the next couple of days.) BTW, data
rate is 10x/sec.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>Earl</FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>