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Posted for "Aircraft Designs, Inc." <aircraftdesigns@cwix.com>:
Dear Marv,
Would you please post the following rebutal to Mr. X's letter.
Dear Aviator,
This is a continuation of my reply to the posting on LML from Mr. X. Mr. X
is Dr. Dennis Olcott who worked on the certification for the Columbia at
Pacific Aviation Composites (a company founded by Lancair). I (Martin
Hollmann) never recall having worked or spoke with Olcott since I only
worked on the Lancair kit aircraft and not the certified Columbia. However,
I did hear that he claimed that my finite element analysis (fea) models did
not use the correct properties. I replied to Lancair that I used certain
"tricks" such as increasing the material density and material stiffness so
that the fea model would represent the actual structure. In this manner
such details as the affect of flanges, fuel sealer, and paint are accounted
for. I also use "tricks" such as using "coupled nodal displacements" to
model hinges for control surfaces. I explain these methods in my books on
flutter and in my classes.
Olcott claims that I stated that Norbert did not know how to do fea because
he made the claim of using a "few tricks." It was I that said you had to
use a "few tricks" to perform fea so that the results match the actual
structure. Olcott is mixed up with what I said and Norbert said. Norbert,
by-the-way, is the flutter expert who Lance went to for a third opinion. I
never stated that Norbert did not know fea or how to perform a flutter
analysis.
Furthermore, Olcott states that "it is actually quite simple to excite the
fuselage bending and aft torsion modes in an airplane using your hand, let
alone an electromagnetic shaker." Does this mean that Norbert did not use a
shaker to excite the mode shapes? Did he use his hands? (remember from my
last rebutal that I have never seen the flutter reports performed by other
on the Lancair's.) If he did, he may very likely not have excited the
fuselage bending mode since shakers that can generate up to 100 lbs of
force or pyrotechnic devices are often recommended to excite fuselage
bending modes. It was the fuselage bending mode that caused a problem on
the Lancair 360 with the large tail. Sandy Friesner performed the gvt on
Dave Morss's Lancair 360 with the big tail to find the fuselage bending
frequency. Sandy is one of the world's leading gvt experts. The fuselage
bending mode was determined by my fea and the gvt was performed to validate
this mode. Needless to say, Dave made the change to his Lancair 360.
I should also add that it was the fuselage bending mode coupling with
another mode that caused the first BD-10 to crash. The fea had shown this
mode and a subsequent gvt did not. However, I found the fuselage bending
mode using fea and in a very early gvt performed on the BD-10. And "Bingo",
I was able to identify and fix the problem.
Olcott worked for Pacific Aviation Composites for a short time and went to
work for Burt Rutan at Scaled Composites. For the past 2 years he has been
working for Scale Technology Works in Montrose, CO. This compay was
founded by Scaled Composites and it is in direct compition with High Tech
Composites with whom I work very closely. High Tech Composites built all
the original parts for all the Lancair kit aircraft and most of the other
aircraft that I have worked on. As such Olcott's statement "Since I no
longer work at Lancair, and since I did not work on the design of the 360,
I feel that my opinions should be somewhat unbiased . . ." is ridiculous.
He and the company that he works for are in direct competion with me and
the company I work with. It is to his personal gain and the company he
works for to bad mouth me and the efforts I have made in helping to make
the Lancair series of aircraft fun and safe.
I have given technical support to all of the Lancair builders for the past
15 years. I have always been available to answer technical and builder's
questions to the many Lancair builders and I hope to be able to continue my
efforts in the years to come. If you are interested in some of the new
developments in the Lancair IV or want to know more about my efforts see my
web site at www.aircraftdesigns.com or give me a call at 831-649-6212. The
Lancair series of kit aircraft are one of the best aircraft kits in the
world today. But be safe and do not be afraid listen to the "expert."
Martin Hollmann
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