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Date: Tue, 17 Jul 2012 15:30:40 -0400
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From: cwfmd@yahoo.com
Subject: Flutter/VNE
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This might be beating a dead horse, but flutter analysis, even in mil spec =
or FAA certified,=A0is a bit of a black art. There's lots on non-linear, ha=
rd-to-model structural, aerodynamic, and math mysteries. A huge amount of j=
udgment and experience applies here.
=A0=A0In certified airplanes, we=A0suspect they sample random structures of=
f the line, over time, to verify the original flight test model. Or maybe e=
ven go back to flight test, if mishaps or other reports suggest flutter. If=
 you are Chuck Yeager, you get to fly a notorious driven mass device, that =
drives the oscillation at resonance=A0 (evil smile)
=A0(=A0 2nd order systems are usually junior or senior level E school cours=
es, after 2nd yr Calculus and Diff-E. Even those who survived it, forgot th=
e technique, if not applied regularly... State-space? Anyone? Anyone?=A0=A0=
 )
=A0How would we do, either testing(not) or sampling,=A0when all the builder=
s have varying experience, and=A0factories are at separate locations?
Published VNE only applies to Lance's original build and his test on one ar=
ticle. I'm sure we signed a waiver to that effect in this process!
=A0 It would be fairly cheap to mount an Accelerometer out on the wing, and=
 hook it up to an analog input on the EFIS. Certain frequencies and amplitu=
des could trigger a warning. This is the only way to be certain, of VNE,=A0=
to the level indicated above, for Mil and FAA standards.
Y'all be careful out there
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<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;"><DIV>This might be beating a dead horse, but =
flutter analysis, even in mil spec or FAA certified,&nbsp;is a bit of a bla=
ck art. There's lots on non-linear, hard-to-model structural, aerodynamic, =
and math mysteries. A huge amount of judgment and experience applies here.<=
/DIV>
<DIV>&nbsp;&nbsp;In certified airplanes, we&nbsp;suspect they sample random=
 structures off the line, over time, to verify the original flight test mod=
el. Or maybe even go back to flight test, if mishaps or other reports sugge=
st flutter. If you <SPAN>are</SPAN> Chuck Yeager, you get to fly a notoriou=
s driven mass device, that drives the oscillation at resonance&nbsp; (evil =
smile)</DIV>
<DIV>&nbsp;(<EM>&nbsp; 2nd order systems are usually junior or senior level=
 E school courses, after 2nd yr Calculus and Diff-E. Even those who survive=
d it, forgot the technique, if not applied regularly... State-space? Anyone=
? Anyone?</EM>&nbsp;&nbsp; )</DIV>
<DIV>&nbsp;How would we do, either testing(not) or sampling,&nbsp;when all =
the builders have varying experience, and&nbsp;factories are at separate lo=
cations?</DIV>
<DIV>Published VNE only applies to Lance's original build and his test on o=
ne article. I'm sure we signed a waiver to that effect in this process!</DI=
V>
<DIV>&nbsp; It would be fairly cheap to mount an Accelerometer out on the w=
ing, and hook it up to an analog input on the EFIS. Certain frequencies and=
 amplitudes could trigger a warning. This is the only way to be certain, of=
 VNE,&nbsp;to the level indicated above, for Mil and FAA standards.</DIV>
<DIV>Y'all be careful out there</DIV></td></tr></table>
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