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<DIV><FONT face=Arial size=2>The primary reason for airliner pencil fuselages is
that it is the lightest structure to handle repeated pressurizations.
For streamline bodies form drag is 80 to 90% skin drag, therefore I suspect drag
and lift changes, for up to plus or minus 3 ? degrees AOA, would
be exceedingly small.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It is interesting that airfoils from 9 to18%
can have the same drag coefficent. The determinant is primarily leading edge
radius.
Nat</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=bob@toprudder.com href="mailto:bob@toprudder.com">Bob Richards</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 7:12
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] Airplane
angle of attack</DIV>
<DIV><BR></DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>Bob R.</DIV>
<DIV><BR><BR><B><I>rcmaster199@aol.com</I></B> wrote:</DIV>
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<DIV><SPAN contentEditable=false style="DISPLAY: inline-block"></SPAN>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. </DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>MattK</DIV>
<DIV><BR></DIV>
<DIV><BR></DIV>-----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<BR><BR>
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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>>
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