Message-Id: <9901189166.AA916670199@inet001.cardell.com>
Date: Mon, 18 Jan 99 09:29:43 -0500
From: <dechaze@cardell.com>
To: <lancair.list@olsusa.com>
Subject: Re:Flutter 
Mime-Version: 1.0

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To those of you wrestling with how to add the anti-flutter bid schedule allow me
to cast some doubt into your decision.  I spoke with Martin about a year ago to
discuss his findings (just published at the time) about the 360 tail flutter. 
His analysis consisted of two activities, an FEA and subsequent ground test of
the structure and an aerodynamic analysis that was not validated in flight.  The
FEA tells us what the natural frequencies of the structure are which are
irrelevant absent the excitation frequencies to be furnished by the aerodynamic
model.  So far, so good.

The achilles heel of Martin's analysis in my view is that the aerodynamic model
was not (and could not be reasonably) validated.  His published results
predicted a very low flutter speed of around 150 ktas (I'm going from memory so
you should read his report).  Since we have not lost an airplane (and were his
speed predictions correct we would have, right?) I conclude that his aerodynamic
model is not representative of our airplane.  I invite anyone to challenge this
logic, I am not an aeronautical engineer.  

For this reason, I believe that adding bid tapes is fixing a problem that
doesn't exist in the flight regimes we're using.  They add weight and might
cause unwanted side effects.  Lance's analysis may or may not be flawed but it
the results it gives approximates actual events better.  

Regards,
Ed de Chazal