george wrote in
ps.com:

On Oct 6, 8:26 pm, Bertie the Bunyip wrote:
Le Chaud Lapin wrote
oups.com:



On Oct 5, 6:32 pm, wrote:
It's familiar because there are many out there who don't
understand or don't agree with the textbooks. Even among experts
there's disagreement. Every so often one of them makes an issue of
it. It's quite normal, especially if they don't use the Google
Groups Search function first to see what the previous arguments
have been on the subject on a particular newsgroup.

I'd like to first note something since I am newly exposed to this
field:

In electrical engineering, we have our own set of fundamental
principles. The "terminal" set of primitives governing electronics
(electrostatics and electrodynamics) is Maxwells Equations
http://en.wikipedia.org/wiki/Maxwell_equation. [Ironically, during
his lifetime, Maxwell was also someone who was a leading expert on
aerodynamics. The notions of gradients, the Laplacian, and scalar
potentials have strong parallels in both fields.] In EE, we have
out own myths, like power lines causing brain cancer, but when they
arise, the experts work hard to show indisputable evidence,
verifiable, rigorous evidence to the contrary, to nip the non-sense
in the bud. We do still have areas of disputes, like what causes
shot noise in circuits [http://en.wikipedia.org/wiki/Shot_noise],
but on the bread- and-butter basics, you won't find a college-leve
textbook speaking untruth. So naturally I am extremely surprised to
see this happening in aerodynamics. You are, after all, the rocket
scientists.

It annoys some of us because the same arguments are put
forth
repeatedly and we can't figure out why some don't get it. But it's
no different than my classroom, in which every new batch of
students brings the same misunderstandings and doubts and
arguments. We were young once, too, and didn't believe much of
what our teachers were trying to tell us.

Oh, I certainly don't believe what I wrote in the Jeppensen book.
I don't believe what the 3 CFI's told me recently. I don't believe
what my friends friend, the pilot, told me three years ago. And
though I would be highly honored if I could meet him, I don't
believe what Rod Machado, whom I think we would all agree is not
exactly dumb nor a bad teacher, nor ignorant in the field, wrote.
I don't believe it for two reasons:

1. It's obviously wrong if you read and interpret correctly what
Bernoulli wrote.
2. NASA says it's wrong. From Jim Logajan:
http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html

Bernoulli said that moving air has a lower pressure than
static air. The air over the top of the wing is moving
considerably faster than that underneath, so it has lower
pressure.

People are going to yell and boo me for saying this, but after
taking a nice long ride tonight on my motorcyle tonight, I thought
the venturi/Bernoulli thing through, and I am 95% certain that that
is not the reason the pressure is lower. In fact, I could probably
provide an experiment showing you a situation where air is moving
considerably faster on top than it is on the bottom, with much
higher presure on the top. What is ironic is that Bernoulli would
still be right, but the interpretation of Bernoulli would fall
apart.

It's not
rarefaction; it's the increase in dynamic pressure (velocity) that
subtracts from static pressure, the same phenomenon that makes a
turbine engine work so well.

Not to nit-pick, but dynamic pressure is p(t), where t is time, and
velocity is d/dt R(t), where R is position vector, two totally
different things.

Newton said that for every action there's an equal and
opposite reaction. If you look at the diagrams of airflow
here,http://www.av8n.com/how/htm/airfoils.htmlscrolling down to
Figure 3.2, you'll see that there's upwash ahead of the wing as
well as downwash behind it. the upwash is generated by the
approaching low pressure area above the wing. As the wing passes,
the upwash is converted to downwash; if this isn't Newton at work,
I don't know what is. Newton would be just another dead guy.

Newton did say that. And I looked at that diagram very carefully.
[Thanks for link] The upwash is not casued by an approaching low
pressure. The upwash is caused by a gradient in pressure, going
from high pressure at the leading ede, to low pressure, right above
and slightly-back of the wing, due to rarefication of the wing in
motion. The area above the rarefication is normal atmosphere that
has a propensity to move toward the lower-pressure, rarefied air.
The combination of that normal atmosphere air, combine with the
high velocity of the molecules from the leading edge of the wing,
results in the flow paths (streams) that you see. I haven't looked
yet, but I imagine that there are aerodynamicists, all over the
world, who, if not for appreciation of the hypothesis I am
proposing here, have at least figured this out empircally, and are
fretting day and night trying to find the optimal shape of the
leading edge of the wing. They have two conflicting objectives:

1. Make the shape in such a way so as to minimize drag.
2. Make the shape in such a way so as to increase pressure to
impart high velocity to air molecules moving up/backwards.

I'll be the first to admit that i don't have the capacity to do so
at this moment, but imagine that that one shape of the leading edge
is not appropriate for all speeds of the aircraft. For a given set
of context variables like density, temperature, pressure, angle-of-
attack, airspeed, what-the-plane-was-doing-20-milliseconds-ago,
turbulences...wind, etc...there is an optimal shape for that
leading edge, depending on what you are trying to do. It would be
quite wild if someone were to design a wing that could morph,
dynamically by control of a computer, into an instaneously-optimal
shape.

For the average PPL or CPL this should be sufficient. It's
true
enough, even if it doesn't give the detail that the physicist
would like. As I said, most pilots have other careers and
interests and they find that Newton and Bernoulli jibe with what
they experience in the air, so they're satisfied. Making textbooks
thicker or filling them with competing theories does nothing but
confuse these people.

I believe it should be possible to explain a venturi tube,
Bernoulli's principle, and a decent part of why a wing has lift, in
about 2-3 pages of written text, with pictures, using no formulas,
not even grade-school mathematics.

If a student wants to argue that the physics as presented
are
all wrong he should do extensive research and publish a book on
the subject, not argue with pilots who have been trusting their
soft pink bodies to Bernoulli and Newton for decades.

I definitely agree a paper should be written, and there should be
an element of rigor, obviously lacking in my posts.

However, I honestly think pilot's have been trusting neither
Bernoulli nor Newton. They are dead. But they each left a legacy,
which, according to the NASA links, have been misinterpreted and
abused by countless theoritsts and educators in this field. So one
could say that the pilots have been trusting these theorists and
educators, but perhaps not even that is the case. I think what Ron
hinted at is most- likely the case, that there is a phenomenon that
would allow even a Neanderthal to achieve technical advancement:

The Neanderthal starts with a contraption that works, and through
much trial-and-error, finds better and better rendentions of that
same contraption. Eventually, he will have something that works so
well, that the question of "Why" would hardly need be asked.
Naturally, theorists will tag along and try to explain with
rigorous scientific principles what he has accomplished with only
raw will of spirit, but the theory does not necessarily have to be
right or complete get the thing in the air. Of course, the Wright
Brothers were high-minded individuals, but I think you get the
point.

One might ask, "Well if that is the case, then what is the point of
nit-picking with theory?"

It is because a theory that correctly explains observed phenomenon
generally opens up an entirely new world of order and efficiency.

-Le Chaud Lapin-

Wanna make a bet about how long it takes you to get your licence?

Let's have a pool!

I got never!

90 hours to solo



A control-line model


Bertie