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<DIV><FONT face=Arial color=#0000ff size=2>Hi Jim.</FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> </FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff size=2> Thanks for
taking the time to post your reply. Wonder how many will agree with your
clarification. Some people are amazed with magic also.. <tic>
</FONT></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> </FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> Del</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2>----- Original Message ----- </FONT>
<DIV><FONT face=Arial color=#0000ff size=2>From: "Jim Alberico" <</FONT><A
href="mailto:alberji@charter.net"><FONT face=Arial
size=2>alberji@charter.net</FONT></A><FONT face=Arial color=#0000ff
size=2>></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2>To: "'NSRCA Mailing List'"
<</FONT><A href="mailto:nsrca-discussion@lists.nsrca.org"><FONT face=Arial
size=2>nsrca-discussion@lists.nsrca.org</FONT></A><FONT face=Arial color=#0000ff
size=2>></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2>Sent: Thursday, October 11, 2007
11:19 PM</FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2>Subject: Re: [NSRCA-discussion]
Weather Vane</FONT></DIV></DIV>
<DIV><FONT face=Arial><BR><FONT color=#0000ff size=2></FONT></FONT></DIV><FONT
face=Arial color=#0000ff size=2>> Jim Oddino said:<BR>>
<BR>>>>>> ====<BR>> Wish we had a real aero guy jump in here.
...<BR>> <BR>> Best Regards, Jim<BR>> ==== >>>><BR>>
<BR>> OK, Mr. Oddino, I'll take the bait.<BR>> <BR>> I qualify as a
real aero guy much more than as a pattern pilot. ;-)<BR>> <BR>> This
whole thread started with the dynamics of a stall turn in a crosswind<BR>> (I
think).<BR>> <BR>> Point 1:<BR>> Initial Conditions <BR>> -- steady
wind from the right (constant velocity and direction).<BR>> -- constant
aircraft velocity (or vertical rate of the cg)<BR>> <BR>> To track a
vertical line, the fuse must be pointed to the right. Under<BR>> these
conditions, the thrust line counters gravity as well as the components<BR>>
of drag in the vertical and horizontal directions.<BR>> <BR>> This is
similar to the familiar "crabbing" in horizontal flight to maintain<BR>>
direction. However in the vertical geometric plane, gravity
complicates<BR>> things a bit. ...enough about that.<BR>> <BR>> Note
that in crosswind, rudder trim is required to maintain the horizontal<BR>>
line, as well as the vertical line. This is important. Any
"weathervane"<BR>> effect under these conditions is through control
inputs. It doesn't come<BR>> for free.<BR>> <BR>> Point
2:<BR>> Dynamics Near Stall (dynamics are always more
complicated)<BR>> -- wind still steady from right<BR>> -- aircraft is
decelerating to zero, then accelerating again.<BR>> <BR>> As the vertical
speed (and overall velocity) decreases, the fuse must be<BR>> pointed more
and more to the right to maintain a vertical track. Here is<BR>> where it is
very hard to generalize. So much depends on the details of the<BR>>
aircraft shape, mass properties, control inputs (including throttle),
the<BR>> wind speed, and etc. At zero speed, for example, the ONLY
force countering<BR>> the wind will be thrust. Sideslip forces
certainly enter the picture on the<BR>> final path up and the initial path
down. <BR>> <BR>> Note also that the fuse must point leftward during the
downward phase to<BR>> maintain the line (hence turning into the wind
requires less than 180 deg<BR>> rotation). Again, pilot provides the
rudder trim to maintain the line.<BR>> Here fuselage side force plays greater
role, as thrust is significantly<BR>> reduced. <BR>> <BR>>
...<BR>> <BR>> Regarding weathervane, the phenomenon is certainly present,
but only in<BR>> dynamic situations. <BR>> <BR>> ... But again,
depends on what you mean by weathervane ... In 3D, is a<BR>> steady angled
hover in a steady wind considered weathervaning?<BR>> <BR>> I think not,
but I also do not even think a weathervane "weathervanes"<BR>> after
steady state is established...<BR>> <BR>> I understand the physics fairly
well...I just haven't learned to harness it<BR>> nearly as well as just about
everyone here. ;-)<BR>> <BR>> The graceful way you guys fly is
amazing.<BR>> <BR>> Thanks for reading. Be sure to catch the movie
version someday.<BR>> <BR>> Best regards,<BR>> <BR>> Jim A<BR>>
(ultra-newbie pattern flyer)<BR>> <BR>> <BR>> <BR>> <BR>>
<BR>> <BR>> <BR>> <BR>> <BR>> <BR>> <BR>> <BR>>
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