Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Sun, 19 Jan 2003 10:08:29 -0500
Message-ID: <redirect-1992586@logan.com>
From: RWolf99@aol.com
Subject: LNC2 Tail Flutter
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I understand that there's a difference of opinion between Martin Hollman and 
the Lancair folks.  Hollman's analysis shows a flutter mode well below Vne 
and Lancair's doesn't.  Who knows who is right?  I certainly don't.

However...

I believe that when there is a conflict between test data and analysis 
results, the hardware probably isn't lying.  So the flutter mode that Hollman 
MEASURED by a ground vibration test on Dave Morss airplane suggests that 
maybe Martin is on to something.

Having said that, the flight history (no known flutter in a gazillion flight 
hours and no unexplained bits of Lancairs falling out of the sky) tells us 
that if the flutter mode is real, it must take some amazing stimulus to make 
it happen.  And it must piss off Lancair enormously to have this cloud of 
suspicion promulgated when there's no evidence of in-flight problems related 
to this.

But I'm a very cautious person -- sometimes too much.  And I know just enough 
engineering to be concerned about this, and without access to the analyses or 
expertise in flutter, what was I to do?

I implemented a variation of Martin's recommendation.  I condensed the three 
fairly wide bids that Hollman suggested into a three-inch wide strip of 
something like 14 bid, and put it inside the tailcone in the channels formed 
where the right-left halves glue together.  Top and bottom.  Thought it was a 
small price to pay to not have to worry about it anymore.  I asked Martin 
about this and he said something like "That's interesting.  It should work, 
but I can't give you a formal recommendation unless I analyze that, and that 
will cost you $xxx" where $xxx was something I couldn't possibly afford.  

If you haven't done one of the modifications (mine or his), I wouldn't lose 
any sleep until you hear of the first LNC2 Mk II that either flutters below 
Vne or falls out of the sky for unexplained reasons.  Hasn't happened yet and 
probably won't.

That's what I did.  If you don't do it to *your*  360 Mk II, I will not 
hesitate to fly in it.  In fact, if anyone wants to offer a ride in an 
unmodified large tail 360, you know where to find me!

- Rob Wolf
LNC2 Mk II 51%