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Article #141

Landing gear vibrations: some questions

#141
From: Lorenzo Scaldaferro
Date: Sat, 23 Feb 2002 14:38
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Hello,
i'm an italian mechanical engineer student and i'm writing a thesis
about "landing gear vibration problems".
I'm gonna finish it but i still have some doubts and i hope you can help
me to clarify.

1. I know how shimmy dampers work but i don't know if they are always
used on planes or if they are not, and
      i'd like to understand what makes deciding that use, after
simulations, or always with planes with a certain
      weight or operational speed.
2. I found a publication about "landing gear dynamics" called: Landing
gear integration in aircraft conceptual
      design, by Sonny T. Chai and William H. Mason, it's described how to
proceed to design gear and choose wheels,
      dampers, etc. but nothing is written about considering vibrations
during design, so i'd like to know why.
3. I saw there is an intense use of F.E.A. for shimmy, brakes vibrations
and gear vibrations in general, but i
      also think i understood that the problem is not fully understand. So
what kind of future considerations can we
      do? Are modern airplanes problem free? What are the new technologies
to resolve the problem? Because from what
      i found the way to proceed is use Moreland and Pacejka theories,
made simulations and FEA, test the gear (just
      in two words) but from what i understand is in use that you can
really discover if the plane has shimmy or so
      and sometimes we prefer to maintain a light shimmy if we discover it
after production and there's not an easy
      way to resolve.

I know my questions could result stupid but every discussion, document,
link or else would be very appreciate.

Thanks a lot, Lorenzo
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