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Date: Sun, 09 Feb 2014 16:29:54 -0500
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From: Charles Brown <browncc1@verizon.net>
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Subject: [LML] Re: Angle of attack
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I vote with Chris.  I've been an aerodynamicist at Boeing and at General =
Dynamics (now Lockheed Martin).  For a whole airplane (not just an =
airfoil section), to simplify all the complexity of wing root incidence, =
twist/washout and spanwise airfoil variations, normally the angle of =
attack that produces approximately zero lift on the whole airframe+wing =
is arbitrarily chosen as "zero".  And by the way, usually airplanes are =
designed with the wing tipped up slightly with respect to the fuselage =
(angle of incidence), so that at cruise conditions the fuselage deck =
angle (waterline) is approximately zero (level) while the wing is tipped =
up just enough to produce 1g lift (lift=3Dweight).

I'm curious though, what does it matter for an AOA indicator?  Cruise =
angles of attack are absolutely uninteresting.  Stall warning at some =
angle of attack that's just a little shy of max lift coefficient is the =
only angle that you have to dial in properly, right?

Charley Brown


Posted for Chris Zavatson <chris_zavatson@yahoo.com>:
 =20
 Angle of attack can have a few different definitions.  If tied to =
airframe=20
or airfoil geometry then zero degrees can produce positive lift.  To =
keep the=20
math simple, the zero lift line is used.  By definition, when it is at =
zero=20
angle there is zero lift.  Any positive angle produces positive lift.  =
This=20
removes all the variables of the physical geometry such as washout and=20=

incidence angles, etc.
 Down low and fast the 360 needs a lift coefficient of about 0.19 or =
about=20
1.9 degrees - referenced to the zero lift line.

 Chris Zavatson
 N91CZ
 360std
 http://www.n91cz.net/


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<html><head></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
"><div>I vote with Chris. &nbsp;I've been an aerodynamicist at Boeing =
and at General Dynamics (now Lockheed Martin). &nbsp;For a whole =
airplane (not just an airfoil section), to simplify all the complexity =
of wing root incidence, twist/washout and spanwise airfoil variations, =
normally the angle of attack that produces approximately zero lift on =
the whole airframe+wing is arbitrarily chosen as "zero". &nbsp;And by =
the way, usually airplanes are designed with the wing tipped up slightly =
with respect to the fuselage (angle of incidence), so that at cruise =
conditions the fuselage deck angle (waterline) is approximately zero =
(level) while the wing is tipped up just enough to produce 1g lift =
(lift=3Dweight).</div><div><br></div><div>I'm curious though, what does =
it matter for an AOA indicator? &nbsp;Cruise angles of attack are =
absolutely uninteresting. &nbsp;Stall warning at some angle of attack =
that's just a little shy of max lift coefficient is the only angle that =
you have to dial in properly, right?<br><div =
id=3D"_htmlarea_default_style_" style=3D"font:10pt =
arial,helvetica,sans-serif"><br>Charley Brown<br><br><br></div><div =
id=3D"_htmlarea_default_style_" style=3D"font:10pt =
arial,helvetica,sans-serif">Posted for Chris Zavatson
&lt;<a =
href=3D"mailto:chris_zavatson@yahoo.com">chris_zavatson@yahoo.com</a>&gt;:=
<br>&nbsp;&nbsp;<br>&nbsp;Angle of attack can have a few different =
definitions.&nbsp; If tied to airframe <br>or
airfoil geometry then zero degrees can produce positive lift.&nbsp; To =
keep the <br>math simple, the zero lift line is used.&nbsp; By =
definition, when
it is at zero <br>angle there is zero lift.&nbsp; Any positive angle =
produces positive lift.&nbsp; This <br>removes all the variables of the =
physical
geometry such as washout and <br>incidence angles, etc.<br>&nbsp;Down =
low and fast the 360 needs a lift coefficient of about 0.19 or about =
<br>1.9
degrees - referenced to the zero lift line.<br><br>&nbsp;Chris =
Zavatson<br>&nbsp;N91CZ<br>&nbsp;360std<br>&nbsp;<a =
href=3D"http://www.n91cz.net/">http://www.n91cz.net/</a><br><br><br></div>=
</div></body></html>=

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