<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.6000.16544" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV><FONT face=Arial color=#0000ff size=2>Hi Jim..</FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> Back when I
entered competition, I used to freeze on the dumb thumb (left) and not do
anything. I can't recall a time it didn't flop like a wounded duck.. Don't
recall if the nose/tail angle changed any.. Admits to having sometimers.
</FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> </FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> Del</FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2> </FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2>----- Original Message ----- </FONT>
<DIV><FONT face=Arial color=#0000ff size=2>From: "James Oddino" <</FONT><A
href="mailto:joddino@socal.rr.com"><FONT face=Arial
size=2>joddino@socal.rr.com</FONT></A><FONT face=Arial color=#0000ff
size=2>></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2>To: <</FONT><A
href="mailto:alberji@charter.net"><FONT face=Arial
size=2>alberji@charter.net</FONT></A><FONT face=Arial color=#0000ff size=2>>;
"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: Friday, October 12, 2007 8:14
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>> Hi Jim A,<BR>> <BR>> Thanks for your
input. Now you are going to have to answer all our <BR>>
questions. Welcome to the club.<BR>> <BR>> Your description of the
vertical portion of a stall turn sounds good <BR>> to me . I
never did find the beginning of the thread and only jumped <BR>> in
because it sounded like some folks didn't believe that air <BR>>
vehicles weathervane in flight.<BR>> <BR>> My experience is with antitank
missiles that are launched at <BR>> relatively low velocity from a tube
pointed roughly at the target. <BR>> The low velocity is a result
of a short launch motor burn time, <BR>> completed within the tube so
the gunner doesn't get a blast in the <BR>> face. A flight motor
ignites when the missile is a safe distance in <BR>> front of the
gunner.<BR>> <BR>> If we launch this missile with locked controls, we'd
expect it to yaw <BR>> slightly into any crosswind (and drift downwind
off the line of <BR>> sight) as it exits the tube. Sound
right?<BR>> <BR>> Back to the vertical portion of the stall turn with a
pattern plane, <BR>> only this time with locked rudder. We all
agree it will drift off <BR>> the track as it slows to a stop.
The question is, will it yaw into <BR>> the wind on its own as it slows
to a stop? If it does, this is my <BR>> definition of
weathervaning.<BR>> <BR>> I'm recovering from an emergency appendectomy so
I'm depending on all <BR>> you other guys to go try a cross wind stall
turn with no rudder <BR>> command tomorrow and report on your
results.<BR>> <BR>> Best Regards, Jim O<BR>> <BR>> <BR>> On Oct
11, 2007, at 8:19 PM, Jim Alberico wrote:<BR>> <BR>>> 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 <BR>>>
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. <BR>>> Under<BR>>> these
conditions, the thrust line counters gravity as well as the <BR>>>
components<BR>>> of drag in the vertical and horizontal
directions.<BR>>><BR>>> This is similar to the familiar "crabbing"
in horizontal flight to <BR>>> maintain<BR>>> direction.
However in the vertical geometric plane, gravity <BR>>>
complicates<BR>>> things a bit. ...enough about
that.<BR>>><BR>>> Note that in crosswind, rudder trim is required to
maintain the <BR>>> horizontal<BR>>> line, as well as the
vertical line. This is important. Any <BR>>>
"weathervane"<BR>>> effect under these conditions is through control
inputs. It <BR>>> 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 <BR>>> must be<BR>>> pointed more and more
to the right to maintain a vertical track. <BR>>> Here
is<BR>>> where it is very hard to generalize. So much depends on
the <BR>>> details of the<BR>>> aircraft shape, mass
properties, control inputs (including <BR>>> throttle),
the<BR>>> wind speed, and etc. At zero speed, for example, the ONLY
force <BR>>> countering<BR>>> the wind will be thrust.
Sideslip forces certainly enter the <BR>>> 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
<BR>>> phase to<BR>>> maintain the line (hence turning into the wind
requires less than <BR>>> 180 deg<BR>>> rotation).
Again, pilot provides the rudder trim to maintain the <BR>>>
line.<BR>>> Here fuselage side force plays greater role, as thrust
is <BR>>> significantly<BR>>> reduced.<BR>>><BR>>>
...<BR>>><BR>>> Regarding weathervane, the phenomenon is certainly
present, but <BR>>> 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 <BR>>> "weathervanes"<BR>>>
after steady state is established...<BR>>><BR>>> I understand the
physics fairly well...I just haven't learned to <BR>>> 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>>>
_______________________________________________<BR>>> NSRCA-discussion
mailing list<BR>>> </FONT><A
href="mailto:NSRCA-discussion@lists.nsrca.org"><FONT face=Arial
size=2>NSRCA-discussion@lists.nsrca.org</FONT></A><BR><FONT face=Arial
color=#0000ff size=2>>> </FONT><A
href="http://lists.nsrca.org/mailman/listinfo/nsrca-discussion"><FONT face=Arial
size=2>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</FONT></A><BR><FONT
face=Arial color=#0000ff size=2>> <BR>>
_______________________________________________<BR>> NSRCA-discussion mailing
list<BR>> </FONT><A href="mailto:NSRCA-discussion@lists.nsrca.org"><FONT
face=Arial size=2>NSRCA-discussion@lists.nsrca.org</FONT></A><BR><FONT
face=Arial color=#0000ff size=2>> </FONT><A
href="http://lists.nsrca.org/mailman/listinfo/nsrca-discussion"><FONT face=Arial
size=2>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</FONT></A><BR><FONT
face=Arial color=#0000ff size=2>></FONT></BODY></HTML>