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I think this is an
unanswerable question. There is no doubt that Lance and his designers did all
the calculations on every plane he kitted but what did he make those
calculations on?? The kits are not shipped built so a portion of the
calculations Lancair would have to consider is the builders ability and
materials used. With that in mind there could be a big difference in the high
numbers to the low numbers. Since the Lancair's seem to be pretty stout,
for the most part, Lancair must have put a large margin in his calculations to
consider the worst case. If that's the case, it makes me wonder what his numbers
REALLY where, not what he prints in the POH.
A certified, "factory built"
aircraft would have set numbers on set calculations since the building process
and materials would be pretty consistent. Then add the safety margin. There are
so many variables on a kit aircraft I don't know how you could have any set
numbers on a specific Lancair, only set numbers on the parts themselves.
I'm sure someone out there in
Lancair land knows how these were derived and what ALL the numbers were. It
would be interesting to see the real numbers.
Randy
Stuart
LNC-2
----- Original Message -----
Sent: Tuesday, December 15, 2009 5:41
AM
Subject: [LML] Re: Vne discussion
If you really want to know the answer, you should ask Lance or the
engineer(s) responsible for the analysis. Unless one is privy to the
calculations and testing done on the airframe, there is no way of providing
you with a credible answer to your question.
As has been stated already, there are numerous potential reasons for
failure as speed is increased. One that I haven´t seen mentioned
is aerodynamic heating and this is a speed limit on at least one miltary
jet as the canopy melts above this speed. Another is wing wake inteference
with the horizontal stabilizer, which was an issue with the P38. This is
typically a mach related issue. The list is quite extensive, and while many of
the possible limiting factors may be unrealistic for the 300 or Legacy there
are still many that may be applicable. Without being familliar with the
analysis of these planes, it is impossible to know what the critical limiting
factor was in the assigning Vne.
While it may be pleasing to know the
answer for accademic reasons, what else would you do with the information?
Alter the structure to increase Vne? Can you analize the modification to
determine its effect(s) upon the other parameters than the one you are trying
to improve? In other words, will your fix actually reduce Vne? This can get
very deep very fast.
Don´t feed the worms,
Rob
-----Original
Message----- From: Wolfgang <Wolfgang@MiCom.net> To:
lml@lancaironline.net Sent: Mon, Dec 14, 2009 7:18 pm Subject: [LML] Re:
Vne discussion
I'm having difficulty understanding why no one can give direct
answers.
I'm only looking for the various factors that are used to determine
Vne.
Flutter, canopy being sucked off, skin surface excess vibration . . ? ?
?
. . . not the explecit calculations.
Let's narow it down, what factors for the 300 series and Legacy ?
Wolfgang
Wolfgang,
As has been stated a number of times on this forum,
the determination of Vne is a very complex and multi-discipline task. Not to
repeat what’s been said many times, the several aero engineers that
participate in this forum have suggested that this subject is probably beyond
a basic aero engineering degree. You’re unlikely to find one of these people
willing to offer a “back of the hand” quick solution. LOTS of information on
the internet about this subject, and some serious reading available. a couple
of courses on aeronautical design and finite element analysis will give you
some idea of what you are looking for. Definitely beyond a simple posting on
the LML, IMHO.
Bob
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Yes, there was extensive information published here about the Vne
determination.
Scott Krueger |
So . . . am I to conclude that there's nobody on
the list that can identify how Vne is determined ?
With all the experience of posters on this list,
I'm surprised to say the least.
Is this black magic art or is there some real
formula/procedure ?
All I've seen here so far is "is that meadured in
IAS, TAS OR Mach ?" or "what is the speed for xxx airframe
?".
. . . but nothing about how the number comes to
be.
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