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<DIV><FONT face=Arial size=2>It is possible to ruin an otherwise good design
with the geometry of the thrustline/wing/stab placement as well as control
surface geometry and hinging. Top ranked pilots usually can make most anything
look good though.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It is not unusual for full
scale airplanes to display the same airspeed for two different angles of
attack. The AOA that requires the least power for a given airspeed is generally
referred to as being "on the step". If a pattern airplane is configured in
a manner that these two operating points are close together the return to level
flight presents an increased workload. I believe the current trend of high
volume fuselages makes it difficult to achieve an "on the step"
condition.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Just my opinions of course...</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>John Ferrell W8CCW<BR>"Life is easier if you learn to
plow <BR> around the stumps"<BR><A
href="http://DixieNC.US">http://DixieNC.US</A><BR></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=chris@ssd.fsi.com href="mailto:chris@ssd.fsi.com">White, Chris</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 03, 2007 8:47
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] Airplane
angle of attack</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Understanding that a
lot of misinterpretation can happen in reading or talking about things without
actually being directed in person on the subject article, I dismissed the
following story. Now after this post it has me curious again and I would be
interested to hear comments from people who may have been told the same.
<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">The story comes as a
result of a couple of local pilots who were working on a well-known $2K arf
from 2005-6 era that had no reference lines on the fuse, nor measurements in
the plans referring to Thrustline or any clue as to where to start on fuselage
angle to engine-wing-stab setups. Communication with the designer
resulted in the customer being told that it should be done by appearance.
(eg: the way you wish to see your fuse angle in level flight
cruise.)<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">That seems very
subject to interpretation and I would think if a person were a few degrees off
it would make a significant difference on aerodynamic behavior during
maneuvering. (mixing etc)<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">There’s probably a
post on this somewhere, but Bob’s comment led me to think of that setup
dilemma. I’ve never seen or heard of an airplane kit/arf without
some reference to thrust line, until I heard my local friends told me about
this one.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Is this scenario
familiar to anyone out there? <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">(Gee, do I push send
or not…….ok I’ll send it.)<o:p></o:p></SPAN></FONT></P>
<DIV>
<P class=MsoAutoSig><FONT face=Palatino color=navy size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: navy; FONT-FAMILY: Palatino">Chris
White<o:p></o:p></SPAN></FONT></P></DIV>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; 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>Bob Richards<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Wednesday, October 03, 2007 7:13
AM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> <st1:PersonName
w:st="on">NSRCA Mailing List</st1:PersonName><BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: [NSRCA-discussion] Airplane
angle of attack</SPAN></FONT><o:p></o:p></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">I never meant to draw any conclusion about the knife
edge performance of airliners or bombers in my original post. I was merely
stating that the reason we PATTERN FLIERS adjust the incidences of the wing
and stab (ON OUR PATTERN PLANES) has to do with aerobatic performance. As far
as I know, the reason the designers of airliners, bombers, and most full-scale
airplanes pick a incidence value has to do mainly with efficiency in
cruise.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">Bob R.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><BR><BR><B><I><SPAN
style="FONT-WEIGHT: bold; FONT-STYLE: italic">rcmaster199@aol.com</SPAN></I></B>
wrote:<o:p></o:p></SPAN></FONT></P></DIV>
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<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">I remember watching a clip of a full size multi
engine bomber type in test flight. The test pilot banked hard to knife edge
near the ground (maybe 500 ft) for some unknown reason and swiftly proceeded
to put it in. Don't remember the plane's or test pilot's names.
<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">Full scale fuselages are designed to minimize drag
as much as possible (for max range) so they tend to be pencil thin
comparatively speaking. Pencil thin fuses do not fly knife flight well nor
are they intended to do so. And the higher the weight the worse the problem.
At risk of being glib, that test pilot found the outside of the
envelope.<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">MattK<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<P class=MsoNormal style="MARGIN-BOTTOM: 12pt"><FONT face="Times New Roman"
size=3><SPAN style="FONT-SIZE: 12pt">-----Original Message-----<BR>From:
chris moon <cjm767driver@hotmail.com><BR>To:
nsrca-discussion@lists.nsrca.org<BR>Sent: Tue, Oct 2 4:28 PM<BR>Subject: Re:
[NSRCA-discussion] Airplane angle of attack<o:p></o:p></SPAN></FONT></P>
<DIV id=AOLMsgPart_3_b6d597c8-f6a1-47c8-a976-7e61ea56aa74>
<P class=MsoNormal style="MARGIN-BOTTOM: 12pt"><FONT face="Times New Roman"
size=3><SPAN style="FONT-SIZE: 12pt">The optimum AOA on airliners is a
function of wing design. It's the <BR>operator's job to try and stay near
the optimum AOA for maximum <BR>efficiency. Lighter gross weights require
either higher altitudes or <BR>lower true airspeed to be most efficient.
Likewise, heavier weights will <BR>have you faster and or lower. I guess
what I'm saying is that the <BR>optimum AOA is essentially dictated by wing
design and we juggle the <BR>other variables in order operate the wing as
efficiently as possible. <BR><BR>I have rolled the 737, 757, 767 and A320 in
the simulator and they make <BR>poor pattern planes. I'm sure there is a
significant downgrade for a <BR>single roll that loses 5000+ feet of
altitude. Don't even ask about <BR>knife edge performance. <BR><BR>Chris
<BR><BR>Bob Richards wrote: <BR>> That makes sense to me. The AOA depends
on the load. In an extreme <BR>> case, very lightly loaded, I don't think
you would want to fly with <BR>> the fuselage in a nose down attitude,
that would probably be <BR>> inefficient. Better to have it slightly nose
up in cruise with a full <BR>> load. JMHO. <BR>> Of course, the reason
WE would trim wing incidence would have more to <BR>> do with overall
flight characteristics during aerobatics, particularly <BR>> with pitch
coupling in knife edge flight. <BR>> Bob R. <BR>> <BR>> <BR>>
*/chris moon /* wrote: <BR>> <BR>> Tried to post this before but it
did not go through. <BR>> <BR>> The optimum cruise angle of attack for
jetliners is somewhere between <BR>> 2.5 and 5 degrees nose up. Usually
closer to 2.5 or 3 degrees for an <BR>> econ cruise. As fuel burns off
and the gross weight goes down, the <BR>> airplane will need a lower
angle of attack to maintain flight which <BR>> will take us away from our
optimum angle (lower). So, we will either <BR>> climb to where the air is
"thinner" and require a higher aoa <BR>> (angle of <BR>> attack) to
get us back to the 2.5 or 3 degrees or, slow down and <BR>> maintain the
lower altitude thus requiring us to increase the aoa <BR>> back <BR>>
to optimum. The answer to your question is yes, a jetliner flies at a
<BR>> nose high aoa in cruise. Lift from the fuselage would probably be
<BR>> negligible other than "impact" lift - the force of the relative
wind <BR>> against the raised fuselage bottom. <BR>> <BR>> Chris
<BR>> <BR>> <BR>>
------------------------------------------------------------------------
<BR>> <BR>> _______________________________________________ <BR>>
NSRCA-discussion mailing list <BR>> <A
href="mailto:NSRCA-discussion@lists.nsrca.org">NSRCA-discussion@lists.nsrca.org</A>
<BR>> <A href="http://lists.nsrca.org/mailman/listinfo/nsrca-discussion"
target=_blank>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</A>
<BR><BR><o:p></o:p></SPAN></FONT></P>
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<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">Climb to the top of the charts! Play Star
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<DIV id=AOLMsgPart_4_b6d597c8-f6a1-47c8-a976-7e61ea56aa74><PRE style="BACKGROUND: white"><TT><FONT face="Courier New" color=black size=2><SPAN style="FONT-SIZE: 10pt; COLOR: black">_______________________________________________ NSRCA-discussion mailing list <A href="mailto:NSRCA-discussion@lists.nsrca.org">NSRCA-discussion@lists.nsrca.org</A> <A href="http://lists.nsrca.org/mailman/listinfo/nsrca-discussion" target=_blank>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</A> </SPAN></FONT></TT><FONT color=black size=1><SPAN style="FONT-SIZE: 9pt; COLOR: black"><o:p></o:p></SPAN></FONT></PRE></DIV>
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