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<DIV><FONT face=Arial size=2>Jim</FONT></DIV>
<DIV><FONT face=Arial size=2>I believe someone answered this - the arrow
attitude will be straight down regardless of wind velocity. With wind,to an
observer on the ground, the track will not be vertical. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Just like the airplane, the arrow does not know the
wind is blowing.
Nat</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=joddino@socal.rr.com href="mailto:joddino@socal.rr.com">James
Oddino</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, October 10, 2007 6:20
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] Weather
Vane</DIV>
<DIV><BR></DIV>Nat,
<DIV><BR class=khtml-block-placeholder></DIV>
<DIV>If you hold an arrow (or a bomb) horizontal and drop it, what happens to
it's attitude on the way down and why? Then drop it with a crosswind of
32 ft/sec. What happens to its attitude?</DIV>
<DIV>Seems pretty obvious to me.</DIV>
<DIV><BR class=khtml-block-placeholder></DIV>
<DIV>Jim</DIV>
<DIV><BR class=khtml-block-placeholder></DIV>
<DIV><BR>
<DIV>
<DIV>On Oct 10, 2007, at 2:21 PM, Nat Penton wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV><FONT face=Arial size=2>Ron</FONT></DIV>
<DIV><FONT face=Arial size=2>You are correct - an airplane does not
weathervane or weathercock - it fliies straight into the freestream
unless given rudder. BUT, as Kennie says, he hopes to be here next year
to reargue the point
!!
Nat</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=ronlock@comcast.net
href="mailto:ronlock@comcast.net">ronlock@comcast.net</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> ; <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, October 10, 2007
11:07 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion]
Weather Vane</DIV>
<DIV><BR></DIV>
<DIV>
<DIV style="MARGIN: 0in 0in 0pt">I thought I'd throw in my 2 cents worth,
but maybe it turned into too much. Ya been warned
<G>.</DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<DIV style="MARGIN: 0in 0in 0pt">There is a strong, almost overwhelming,
visual perception that airplanes weathervane into the wind as seen by an
observer on the ground.<SPAN style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-spacerun: yes"> </SPAN></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">If the airplane is partly connected to
the ground (as in takeoff or landing roll) it will likely weathervane into
the wind. <SPAN style="mso-spacerun: yes"> </SPAN>(Like a real
weathervane on the barn).<SPAN style="mso-spacerun: yes">
</SPAN>Putting more side area behind the CG probably increases the
weathervane effect.</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">But once airborne, an airplane no longer
feels wind on side of the airplane and does not weathervane in the sense
that the weathervane on the barn does.<SPAN
style="mso-spacerun: yes"> </SPAN>Nor does the hot air balloon
mentioned in an earlier post.</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">Just after take off, we likely see the
nose is pointed some amount into the wind.<SPAN
style="mso-spacerun: yes"> </SPAN>This visual perception is true.
But is it proof of weathervaning?<SPAN style="mso-spacerun: yes">
</SPAN>It probably weathervaned into the wind during take off roll. Once
airborne the weathervane is now what we call a crab angle into the
wind.</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">We all know stall turns are easier to do
"into the wind". <SPAN style="mso-spacerun: yes"> </SPAN>Is it
because they weathervane?<SPAN
style="mso-spacerun: yes"> </SPAN>On the upline to a
stall turn in a cross wind, does the pilot wind correct the airplanes
track?<SPAN style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-spacerun: yes"> </SPAN>Most of us do, consciously or
not.<SPAN style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-spacerun: yes"> </SPAN>If we are having any success
at all with the wind correction, the fuselage is "leaning" into the wind a
bit <SPAN style="mso-spacerun: yes"> </SPAN>It's certainly
easier to get a stall turn by continuing into the established lean, than
it is to go against the lean to the downwind direction.<SPAN
style="mso-spacerun: yes"> </SPAN></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">Pilots try to make heading adjustments to
hold track, or hold distance in lines and maneuvers. <SPAN
style="mso-spacerun: yes"> </SPAN>Those adjustments (crab angles) can
appear to be a result of weathervaning, but are often pilot inputs,
consciously or not.</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">Related things to consider-<SPAN
style="mso-spacerun: yes"> </SPAN></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">Airplanes do get "hit" in the side, top
and bottom when in turbulent wind, and wind shear situations.<SPAN
style="mso-spacerun: yes"> </SPAN>We fly low, and are often in
turbulence.<SPAN style="mso-spacerun: yes"> </SPAN>There may be
short, nearly random, turbulent air effects that result in a weather vane
type effect.</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">A free flight glider does not weather
vane into the wind.<SPAN style="mso-spacerun: yes"> </SPAN>The
glider may fly in circles, but it will drift downwind at the overall
average of the wind speed.<SPAN style="mso-spacerun: yes">
</SPAN><SPAN style="mso-spacerun: yes"> </SPAN>No matter how much
side area is put behind the CG, it will not find and maintain a heading
into the wind.</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">Given flight in no wind situation, a
string tied on nose of an airplane blows exactly backwards and parallel to
the fuselage.<SPAN style="mso-spacerun: yes"> </SPAN>(unless the
airplane is out of rig, or has control surface inputs). <SPAN
style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-spacerun: yes"> </SPAN>If flown in a cross wind direction,
the airplanes track across the ground changes, but the string stays
straight. <SPAN style="mso-spacerun: yes"> </SPAN>(not counting
any effect of propeller induced spiral airflow)</DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="mso-spacerun: yes"></SPAN> </P>
<DIV style="MARGIN: 0in 0in 0pt">The old full scale stories about loosing
airspeed and stalling while doing a "downwind turn" fit into this
discussion to a degree. <SPAN style="mso-spacerun: yes"> </SPAN>Does
wind hit the tail of an airplane as it turns downwind thereby reducing
airspeed?<SPAN style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-spacerun: yes"> </SPAN>In the "old" days, pilots often
flew low and partly judged airplane speed by visual observation of ground
speed. <SPAN style="mso-spacerun: yes"> </SPAN>(similiar to our
situation of observing from the ground)<SPAN
style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-spacerun: yes"> </SPAN>This could lead to the perception
of plenty of ground speed being plenty</DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">Sorting out the visual perception of the
"obvious" weather vane effect is tough.<SPAN
style="mso-spacerun: yes"> </SPAN>Lots of things complicate the
observation - pilot inputs, turbulence, paralax, and more.<SPAN
style="mso-spacerun: yes"> </SPAN></DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="mso-spacerun: yes"></SPAN> </P>
<DIV style="MARGIN: 0in 0in 0pt"><SPAN style="mso-spacerun: yes">IMHO,
bottom line, it's not wind hitting side of airplane, no matter how much
side area is behind the CG.</SPAN></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P>Later, Ron</O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt"><O:P></O:P></DIV>
<DIV style="MARGIN: 0in 0in 0pt">In summary, I agree that as observers on
the ground, we "see" effects that appear to be weathervaning.<SPAN
style="mso-spacerun: yes"> </SPAN>But the "real" cause</DIV></DIV>
<DIV><BR class=khtml-block-placeholder></DIV>
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