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To:  lml
Date: Wed, 02 Dec 2009 09:39:12 -0500
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 receiver=logan.com; client-ip=64.12.206.42; envelope-from=RWolf99@aol.com
Subject: Re: Vne is NOT a meaningless number
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Well, I certainly ignited a firestorm!  Good.  Getting people talking is=
 a good thing.

Randy is right in one respect -- as builders of an airplane we are entitle=
d to set whatever limits we want, as we are legally the manufacturer.  I'm=
 also pleased that his loyal passenger paints a picture of an otherwise ve=
ry cautious pilot.  I still won't fly with him, but then, it's hardly like=
ly that an invitation would be forthcoming, eh?

However, as I tried to say before, there many factors which influence the=
 selection of a never exceed speed.  Sometimes it is flutter (that's a for=
-real, don't-screw-with-this limit, but does not appear to be the limiting=
 factor on the 320/360 airframe), sometimes it is loading imposed by an FA=
A-specified gust (that's a somewhat artificial limit because there is no=
 guarantee that you'll see that gust -- you might get more or you might ge=
t less), sometimes it is loading imposed by a fully deflected aileron at=
 Vne (if that's the case then you might go faster safely if the controls=
 are not fully deflected), sometimes it's a stability or controllability=
 issue caused by Mach-induced center-of-pressure shift (not gonna happen=
 on an LNC2, but it might on an LNC4).  And those are just the more common=
 reasons why a particular Vne speed might be chosen.

Certified airplane manufaturers have to prove to the FAA that the vehicle=
 is safe in all respects up to Vne.  Experimental aircraft are not subject=
 to these constraints -- we can pull numbers from wherever we choose in or=
der to set our placard limits.  Myself, I have simply assumed that Lance=
 and company used a methodology similar to that used by certified airplane=
 manufacturers in establishing their placard limits.  I suspect that they=
 actually used the identical methods, but were not obligated to prove it=
 with FAA-approved and DER-witnessed analyses and tests.  No, I don't know=
 that for sure.  In that respect, no, I have not done any research to conv=
ince myself that the Lancair factory limits are safe, either.  But Lancair=
s have not been breaking up in flight with any regularity (except in thund=
erstoms) so the established limits, which most pilots observe, are probabl=
y okay.

I think it is interesting that Randy and his loyal passenger have assumed=
 that I don't know what I'm talking about simply because my Lancair is not=
 yet flying.  In fact, it is not complete because I was way too busy for=
 several years as a professional aircraft designer, serving as Chief Engin=
eer on an aircraft that was to be certified under FAR Part 23, and later=
 teaching a class on designing aircraft so that they may become certified.=
  And yes, conducting structural loading tests on wings, fuselages, and ve=
rtical tails.  Aircraft engineering is what I do for a living -- building=
 them in my garage is what I do for a hobby.  But this is not a "mine is=
 bigger than yours" contest, so I'll stop there. =20

Jeff Edwards has suggested that I prepare a posting fully explaining how=
 Vne is determined.  He said, and I agree, that many people reading this=
 list would enjoy an educational posting of this nature.  Someday I may do=
 that, but it's not a short subject and I don't have time right now.  Cons=
ider that a cop-out if you must.

Fly safe.

- Rob Wolf


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<font color=3D'black' size=3D'2' face=3D'arial'>
<div>Well, I certainly ignited a firestorm!&nbsp; Good.&nbsp; Getting peop=
le talking is a good thing.</div>


<div>&nbsp;</div>


<div>Randy is right in one respect&nbsp;-- as builders of an airplane we=
 are entitled to set whatever limits we want, as we are legally the manufa=
cturer.&nbsp; I'm also pleased that his loyal passenger paints a picture=
 of an otherwise very cautious pilot.&nbsp; I still won't fly with him, bu=
t then, it's hardly likely that an invitation would be forthcoming, eh?</d=
iv>


<div>&nbsp;</div>


<div>However, as I tried to say before, there many factors which influence=
 the selection of a never exceed speed.&nbsp; Sometimes it is flutter (tha=
t's a for-real, don't-screw-with-this limit, but does not appear to be the=
 limiting factor on the 320/360 airframe), sometimes it is loading imposed=
 by an FAA-specified gust (that's a somewhat artificial limit because ther=
e is no guarantee that you'll see that gust -- you might get more or you=
 might get less), sometimes it is loading imposed by a fully deflected ail=
eron at Vne (if that's the case then you might go faster safely if the con=
trols are not fully deflected), sometimes it's a stability or controllabil=
ity issue caused by Mach-induced center-of-pressure shift (not gonna happe=
n on an LNC2, but it might on an LNC4).&nbsp; And those are just the more=
 common reasons why a particular Vne speed might be chosen.</div>


<div>&nbsp;</div>


<div>Certified airplane manufaturers have to prove to the FAA that the veh=
icle is safe in <EM><U>all</U></EM> respects up to Vne.&nbsp; Experimental=
 aircraft are not subject to these constraints -- we can pull numbers from=
 wherever we choose in order to set our placard limits.&nbsp; Myself, I ha=
ve simply assumed that Lance and company used a methodology similar to tha=
t used by certified airplane manufacturers in establishing their placard=
 limits.&nbsp; I suspect that they actually used the identical methods, bu=
t were not obligated to prove it with FAA-approved and DER-witnessed analy=
ses and tests.&nbsp; No, I don't know that for sure.&nbsp; In that respect=
, no, I have not done any research to convince myself that the Lancair fac=
tory limits are safe, either.&nbsp; But Lancairs have not been breaking up=
 in flight with any regularity (except in thunderstoms) so the established=
 limits, which most pilots observe,&nbsp;are probably okay.</div>


<div>&nbsp;</div>


<div>I think it is interesting that Randy and his loyal passenger have ass=
umed that I don't know what I'm talking about simply because my Lancair is=
 not yet flying.&nbsp; In fact, it is not complete because I was way too=
 busy for several years as a professional aircraft designer, serving as Ch=
ief Engineer on an aircraft that was to be certified under FAR Part 23, an=
d later teaching a class on designing aircraft so that they may become&nbs=
p;certified.&nbsp; And yes, conducting structural loading tests on wings,=
 fuselages, and vertical tails.&nbsp;&nbsp;Aircraft engineering is&nbsp;wh=
at&nbsp;I do for a living -- building them in my garage is what I do for=
 a hobby.&nbsp; But this is not a "mine is bigger than yours" contest, so=
 I'll stop there.&nbsp; </div>


<div>&nbsp;</div>


<div>Jeff Edwards has suggested that I prepare a posting fully explaining=
 how Vne is determined.&nbsp; He said, and I agree, that many people readi=
ng this list would enjoy an educational posting of this nature.&nbsp; Some=
day I may do that, but it's not a short subject and I don't have time righ=
t now.&nbsp; Consider that a cop-out if you must.</div>


<div>&nbsp;</div>


<div>Fly safe.</div>


<div>&nbsp;</div>


<div>- Rob Wolf</div>


<div>&nbsp;</div>


<div>&nbsp;</div>
</font>

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