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Date: Mon, 19 Sep 2005 17:21:00 -0400
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From: "Dan Schaefer" <dfs155@adelphia.net>
Subject: Ailerons and flutter phenomena.
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Gary, your post regarding the subject of flutter was an interesting and
valuable dissertation but unfortunately, of mostly academic value unless one
is designing one's own airplane. None the less, we all benefit by knowing as
much as we can about the subject.

That said, we who build from kits (any kits actually, but I'm referring to
those with proven track records like our Lancairs) are hardly in the
position to do the required (and potentially, destructive) testing to
determine the structural parameters affecting flutter, among other critical
airframe considerations. Basically, the old saw: "You pays your money and
you takes your chances" is in play here, big time. Other than carefully
following the building instructions published by the kit manufacturer (which
includes resisting the urge to make any structural modifications), there is
little the builder can, or should, do regarding those parameters. The urge
to beef up something that "just looks like it needs it" often merely
transfers loads to something else that wasn't meant to handle it, causing a
failure. The eyes, like "gut feelings", are not very good structural testing
devices.

With that as a given, it still makes sense that we should pay close
attention to those things that can contribute to flutter that we CAN control
with maintenance, such as loose elements in control circuit linkages, e.g.,
worn rod-end bearings and/or pulleys (if your airplane uses such things) and
loose control and trim surface hinges. (That's not intended to be a complete
list of contributary items but merely to show where I'm coming from).

Regarding flutter and keeping the airspeed below Vne; this is a given that
any competent pilot should heed if he/she values their (and their
passenger's) hide because of the chance that destructive flutter is lurking
near or just beyond the red-line! I tested my LNC2 at different weights and
CG's to 10% above Vne (incrementally) to be absolutely sure that it wasn't
hiding anything from me if I ever needed to go TO red-line. And I only did
this after making sure that my IAS and CAS were close enough that the
difference wasn't an issue. Even with that, I approached this testing with
the hair on my neck standing straight up and as alert as the proverbial cat
in a room full of rocking chairs, knowing as I said in my earlier post, how
quickly destructive flutter can ruin your whole day!

Cheers,

Dan Schaefer