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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>You’re right Ron, that was more like
5 cents worth </span></font><font size=2 color=navy face=Wingdings><span
style='font-size:10.0pt;font-family:Wingdings;color:navy'>J</span></font><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I do not think the crab or weather-vaning
that I am seeing in a cross wind is my inputs. Heck most of the time my
rudder inputs are wrong anyway </span></font><font size=2 color=navy
face=Wingdings><span style='font-size:10.0pt;font-family:Wingdings;color:navy'>J</span></font><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'> Obviously we don’t know how faithful wind effects are
in simulators but I just played with a strong crosswind in Aerofly and the
after establishing a straight vertical the plane would crab into the
wind. Left going one way and right going the other. I think this is
duplicating what I see when flying the real toys. I guess we will all
have to experiment with the next windy day.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Stu<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>ronlock@comcast.net<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, October 10, 2007
12:08 PM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">NSRCA
Mailing List</st1:PersonName>; <st1:PersonName w:st="on">NSRCA Mailing List</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion]
Weather Vane</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I thought I'd throw in my 2 cents worth, but maybe it turned
into too much. Ya been warned <G>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>There is a strong, almost overwhelming, visual perception that
airplanes weathervane into the wind as seen by an observer on the
ground. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>If the airplane is partly connected to the ground (as in takeoff or
landing roll) it will likely weathervane into the wind. (Like a
real weathervane on the barn). Putting more side area behind the CG
probably increases the weathervane effect.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>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. Nor does the hot air balloon mentioned in an earlier post.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Just after take off, we likely see the nose is pointed some amount into
the wind. This visual perception is true. But is it proof of
weathervaning? 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.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>We all know stall turns are easier to do "into the
wind". Is it because they weathervane? On the
upline to a stall turn in a cross wind, does the pilot wind correct the
airplanes track? Most of us do, consciously or
not. If we are having any success at all with the wind
correction, the fuselage is "leaning" into the wind a bit
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. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Pilots try to make heading adjustments to hold track, or hold distance
in lines and maneuvers. Those adjustments (crab angles) can appear to be
a result of weathervaning, but are often pilot inputs, consciously or not.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Related things to consider- <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Airplanes do get "hit" in the side, top and bottom when in
turbulent wind, and wind shear situations. We fly low, and are often in
turbulence. There may be short, nearly random, turbulent air effects that
result in a weather vane type effect.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>A free flight glider does not weather vane into the wind. The
glider may fly in circles, but it will drift downwind at the overall average of
the wind speed. No matter how much side area is put behind the CG,
it will not find and maintain a heading into the wind.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Given flight in no wind situation, a string tied on nose of an airplane
blows exactly backwards and parallel to the fuselage. (unless the airplane
is out of rig, or has control surface inputs). If flown in a cross
wind direction, the airplanes track across the ground changes, but the string
stays straight. (not counting any effect of propeller induced
spiral airflow)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The old full scale stories about loosing airspeed and stalling while
doing a "downwind turn" fit into this discussion to a degree.
Does wind hit the tail of an airplane as it turns downwind thereby reducing
airspeed? In the "old" days, pilots often flew low and
partly judged airplane speed by visual observation of ground speed.
(similiar to our situation of observing from the ground) This could
lead to the perception of plenty of ground speed being plenty<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Sorting out the visual perception of the "obvious" weather
vane effect is tough. Lots of things complicate the observation - pilot
inputs, turbulence, paralax, and more. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>IMHO, bottom line, it's not wind hitting side of airplane, no matter
how much side area is behind the CG.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Later, Ron<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>In summary, I agree that as observers on the ground, we "see"
effects that appear to be weathervaning. But the "real" cause<o:p></o:p></span></font></p>
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