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<DIV><FONT face=Arial size=2>Bob, Ken, Jim</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Appreciate your comments and agree with the items
mentioned regarding pitot placement and function. Static pressure to the sensor
can / has been a problem, more with some fuselage designs - less with others.
(The older unit I had provided a connection to allow placement of the static
input source - new one doesn't.) </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Airspeed accuracy is an unknown with these units
for the reasons that you mention - but time through a measured distance suggests
that they're reasonably close in level flight. Of course, for pattern flight /
equipment comparisons, the true speed isn't very important as long as the
data are repeatable and reproducible - and they seem to be, the information is
in the deltas. The Eagle Tree graphing software appears to drop outliers
and smooth the data some. Smoothing algorithms are necessary to
render the data useful to look at maneuver information in Excel as
well. Overall, pretty useful info regarding how one flew the
pattern.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It's when one begins to look closely at the raw
data that the "noise" anomaly is noticeably consistent during the
snaps. I agree with everyone's assessment regarding the pitot and shortcomings.
However observed airspeed measurements before and after provide a reasonable
delta across the snap - so measurement through the snap isn't of much interest.
What I'm interested in understanding is whether or not the drop in signal can be
used to ascertain the snap stall. I appreciate the thoughts regarding angular
flow to the pitot and pressure changes within / around the fuse, both
require a look. I do know that very high roll rates, and high pitch rates
without stall, don't produce the same signature. Ah well - more
to do.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Earl</FONT></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 9:30
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>