<!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 6.00.6000.16525" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT face=Arial size=2>I don't work with Airliners but with Corporate
Business Jets. My opinion is that this cylindrical shaped fuselages are not
designed to create lift but payload capacity. If you have a positive angle
on anything to a certain extent it will create lift. There are some Acft
fuselage designed to be part of the lift component of the Acft like
the Short, Caza and a couple of others. This are classified as STOL
(Short Take-Off & Landing). While in the cabin of an big jet it feels
that you might be walking up hill from the back to the front but AOA is directly
changed by speed and CG. I don't think intentionally they make it this way. More
drag means longer flight time, less fuel efficient shorter range. Just my
opinion.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Ken</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=edvwhite@sbcglobal.net href="mailto:edvwhite@sbcglobal.net">Ed
White</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> Sunday, September 30, 2007 1:33
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] Airplane
angle of attack</DIV>
<DIV><BR></DIV>I work for Boeing, although in structures technology, not
aerodynamics. But I work with the aero folks enough to know the answer
they will give. Which will be, "Its not that simple." I know this
because that's the answer I get to every such question I ask.<BR><BR>There are
a lot of factors that will come into play in setting wing incidence.
Where is the cg? What pitch moment effect does the fuselage lift
have? Both these affect how much tail down force is needed to maintain
trim conditions (which affects longitudinal stability but also generates
drag). Then there is the wing-body interface. A knowledgeable aero
person once described the flow at the wing-body interface as "problematic"
(code for we don't know for sure until we try it). Then the fuselage is
not a pure cylinder, the nose is not axi-symmetric (because apparently pilots
want windows to see out of). The area at the wing-body interface has
bump outs for wing carry through structure and other things, and the tail is
usually not placed on the centerline of the fuselage and the tail cone is also
not axi-symmetric to avoid tail strike on take-off.<BR><BR>All of this and a
whole lot of other factors go into fuselage lift and drag.<BR><BR>The simple
design objective is to maximize the lift to drag ratio for the entire aircraft
at cruise conditions. The angle of attack of the fuselage will be
designed to meet that goal as best as possible and may not be 0, and is likely
different for different airplanes.<BR><BR>So now you are all aerodynamics
experts. All you need to know is the easy to learn phrase, "Its not that
simple." Of course I can find you folks at Boeing who will claim that
when I am asked questions about my real expertise, structural dynamics, I tend
to use the same phrase. But don't believe
them.<BR><BR>Ed<BR><BR><B><I>Jeff Hill <jh102649@speakeasy.net></I></B>
wrote:
<BLOCKQUOTE class=replbq
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(16,16,255) 2px solid">This
is a question about full size airplanes that has some <BR>applicability to
model design. We're talking about airliners that <BR>have an essentially
cylindrical fuse.<BR><BR>I'm having a debate with a friend at work about
whether or not full <BR>scale airliners fly slightly nose up. I claim they
do he claims they <BR>don't.<BR><BR>I claim they do because the airflow
would be more stable about a <BR>cylindrical body that was at a slight angle
of attack, and that if <BR>you make it nose up you also gain a little
lift.<BR><BR>He claims that airliners fly with no AOA in the fuse because
the last <BR>thing a designer wants is lift from the fuse because lift
generates <BR>drag, the fuse is not a good shape for generating lift, and
<BR>consequently it isn't worth paying the drag penalty.<BR><BR>What do you
all think?<BR><BR>Jeff
Hill<BR>_______________________________________________<BR>NSRCA-discussion
mailing
list<BR>NSRCA-discussion@lists.nsrca.org<BR>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion<BR></BLOCKQUOTE><BR>
<P>
<HR>
<P></P>_______________________________________________<BR>NSRCA-discussion
mailing
list<BR>NSRCA-discussion@lists.nsrca.org<BR>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</BLOCKQUOTE></BODY></HTML>