From: CHRISTOPHER_ZAVATSON@udlp.com
Date: Mon, 24 May 1999 08:27:47 -0500
Message-ID: <00329345.C21254@udlp.com>
Subject: Aileron Vibration
To: Lancair.list@olsusa.com
Mime-Version: 1.0

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Rick,

I have also witnessed what I assume to be the same aileron vibration on both
left and right sides.  My observations over the last 250 hours have led me to
believe that it has nothing to with flutter (although that was my very first
thought).  What is the cause of the vibration:  A big engine bolted to a light
airframe.  Torsional pulses sent through the fuselage translate into vertical
movement at the wing tips.  I have extended wing tanks.  When the tanks are
full, the ailerons are still.  As the tanks empty over time, vibration
increases.   This makes sense in that the greater the inertia of the wing, the
less movement will be seen.  Throttle and rpm setting will affect this vibration
since you are changing the magnitude and frequency of the input.  Aerodynamic
loads such as running the trim to one extreme and correcting with stick pressure
can eliminate the aileron motions by forcing the it against the hinge with a
greater force than that induced by the acceleration being passed through the
structure by the engine. 
If you see rotational movement about the hinge axis, that is a different
animal-flutter.  If the entire aileron is moving up and down with no
rotation-the mass balancing is doing its job.  This vertical vibration with an
unbalanced surface could easily lead to flutter as it would lead to rotation
about the hinge and aerodynamic coupling.
As the hinges have worn over time, vertical movement has increased.  Constantly
being beaten by the vibrating mass of the aileron is not helping the life
expectancy of the hinges.  The hinges are the sloppiest components in the entire
system in terms of play.  I would love to find a replacement that eliminates all
the play of conventional hinges.  Lancair was looking into this a while back.  I
am curious if they found a replacement.

Chris Zavatson
N91CZ
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