Backwash Causes Lift?

"We" are not in need of getting to the bottom of this. Most of us have
been there and done that.This particular writer, if she chooses to
analyse physics problems, tends to use the Newtonion approximations as
first principles. The good news is my profession doesn't demand those
skills often. I would, however, be interested, as I mentioned earlier,
how you derive conservation of mV from Newton's force/acceleration
relationship. I think you made that claim earlier in this thread.

On Oct 3, 8:38 pm, Tina wrote:
"We" are not in need of getting to the bottom of this. Most of us have
been there and done that.This particular writer, if she chooses to
analyse physics problems, tends to use the Newtonion approximations as
first principles. The good news is my profession doesn't demand those
skills often. I would, however, be interested, as I mentioned earlier,
how you derive conservation of mV from Newton's force/acceleration
relationship. I think you made that claim earlier in this thread.

Hmm...I was afraid you would say that.

A non-hand-waving explanation would too close to the quantum, and
so...it's a bit much to discuss, at least right now. I've posted more
messages in this thread in small period of time than I have ever for
any other topic, in the history of using USENET, or...as one might
say, dN/dt 0, where N is number of messages.

-Le Chaud Lapin-

Still waiting for the conservation of momentum derivation. My husband,
also trained as an engineer, casually remarked he didn't think you
could get from Newton's First Law to the that confirms my memory,
but we are both willing to have that belief rebutted.

He also pointed out that how a CFI might explain how a VOR works would
not satisfy an engineer. For that matter, the physics of flight as
explained to a student pilot would not satisfy someone who might be
interested in designing, as opposed to flying, an airplane, but I
don't think the manuals you are looking at are in error. I would point
out that each field has its own language, and you denying the
conventions used in aviation -- drag, lift and so on -- demonstrates
an unbecoming trait for a student, and even a worse one for an
employee. You may want to rething that attitude if you use it in real
life.






On Oct 3, 11:14 pm, Le Chaud Lapin wrote:
On Oct 3, 8:38 pm, Tina wrote:

"We" are not in need of getting to the bottom of this. Most of us have
been there and done that.This particular writer, if she chooses to
analyse physics problems, tends to use the Newtonion approximations as
first principles. The good news is my profession doesn't demand those
skills often. I would, however, be interested, as I mentioned earlier,
how you derive conservation of mV from Newton's force/acceleration
relationship. I think you made that claim earlier in this thread.

Hmm...I was afraid you would say that.

A non-hand-waving explanation would too close to the quantum, and
so...it's a bit much to discuss, at least right now. I've posted more
messages in this thread in small period of time than I have ever for
any other topic, in the history of using USENET, or...as one might
say, dN/dt 0, where N is number of messages.

-Le Chaud Lapin-

On Oct 4, 6:39 am, Tina wrote:
Still waiting for the conservation of momentum derivation. My husband,
also trained as an engineer, casually remarked he didn't think you
could get from Newton's First Law to the that confirms my memory,
but we are both willing to have that belief rebutted.

My apologies for broaching the subject. Frankly, I would rather save
it for the physicists.

He also pointed out that how a CFI might explain how a VOR works would
not satisfy an engineer. For that matter, the physics of flight as
explained to a student pilot would not satisfy someone who might be
interested in designing, as opposed to flying, an airplane, but I
don't think the manuals you are looking at are in error.

If the manuals are in error, then they are in error. If the manual
issues a disclaimer, saying something, like, "this is not really what
is happening, but this will suffice for us..." that would be ok.
That's not what's happening. The manual mentions things like
Bernoulli, Newtons laws of motion. It even uses vector notation for a
few of the formula's. When one gets that close to the merchandise,
they need to purchase it.

I would point
out that each field has its own language, and you denying the
conventions used in aviation -- drag, lift and so on -- demonstrates
an unbecoming trait for a student, and even a worse one for an
employee. You may want to rething that attitude if you use it in real
life.

There is a difference between convention and errononeous information.
I never discounted drag, lift, or so on...I discounted the
explanations given some of my flight education materials. If it's
wrong, it's wrong. If someone reading it gets comfort from thinking
they understand, or whatever, that's fine for that person. But the
writers of those manuals should know that their audience is broad, and
should not publish erroneous information (after they know that it is
erroneous). There is gross difference between explaining something in
simple terms and being correct, versus explaining something in
moderately-difficult terms, and being incorrect.
I could probably explain VOR to a 10-year-old, without ever mentioning
things like counters, angular frequency, anisotropic radiation,
frequency bands, sub-carriers, convolution, etc....and my explanation
would still be correct.

"When you drink from a straw, there is no suction force."

-Le Chaud Lapin-

On Oct 4, 10:47 am, Le Chaud Lapin wrote:

I could probably explain VOR to a 10-year-old, without ever mentioning
things like counters, angular frequency, anisotropic radiation,
frequency bands, sub-carriers, convolution, etc....and my explanation
would still be correct.


I doubt it. The ten-year-old, and most flight students,
have absolutely no frame of reference to understand any of this in any
depth. I teach a College course on Aircraft Systems, and I have to
keep things really simple so they can grasp a few basics. If you are
an electrical engineer, and I've had a few in my classes, we can get
more into the workings of the VOR, but we leave all the others yawning
and wondering if this is going to be on the final exam.
When we come to hydraulics, we talk about pressure, volume
and area and relate that to what we experience as kids playing with a
garden hose. The same analogy can be used to a limited extent when
explaining Ohm's Law. But now I encounter kids who grew up in
highrises and never squirted their sisters with a hose, so they have
more difficulty. Too much information, not enough relationship to
previous bases because there are none.
You have no frame of reference yet. When you start getting
into violent departure stalls, skidding-turn spins, accelerated
stalls, spirals and the like, the sounds and forces start to make the
textbook stuff real. Sure, Jeppesen isn't always right. I haven't
found a textbook yet that doesn't have some glaring errors, and the
one I use in the Systems class has at least four that I have to issue
corrections on in the syllabus. And the writers of texts have found
that they don't sell the books that go into thousands of pages of
detail; the students have neither the inclination for it nor the time.
They have careers in other fields. So the textbook authors keep it
really simple in the hope that the student will be piqued enough to
dig further on his own. Most don't.
You an argue this as long as you want, like Mx, but it's all
book-learnin' and when the ground starts to come up at you real quick
it won't matter one bit. You WILL want to understand AOA and where you
went wrong.

Dan
Flight Instructor
Aircraft Maintenance Engineer

On Oct 4, 1:51 pm, wrote:
On Oct 4, 10:47 am, Le Chaud Lapin wrote:

I could probably explain VOR to a 10-year-old, without ever mentioning
things like counters, angular frequency, anisotropic radiation,
frequency bands, sub-carriers, convolution, etc....and my explanation
would still be correct.

I doubt it. The ten-year-old, and most flight students,
have absolutely no frame of reference to understand any of this in any
depth. I teach a College course on Aircraft Systems, and I have to
keep things really simple so they can grasp a few basics. If you are
an electrical engineer, and I've had a few in my classes, we can get
more into the workings of the VOR, but we leave all the others yawning
and wondering if this is going to be on the final exam.
When we come to hydraulics, we talk about pressure, volume
and area and relate that to what we experience as kids playing with a
garden hose. The same analogy can be used to a limited extent when
explaining Ohm's Law. But now I encounter kids who grew up in
highrises and never squirted their sisters with a hose, so they have
more difficulty. Too much information, not enough relationship to
previous bases because there are none.
You have no frame of reference yet. When you start getting
into violent departure stalls, skidding-turn spins, accelerated
stalls, spirals and the like, the sounds and forces start to make the
textbook stuff real. Sure, Jeppesen isn't always right. I haven't
found a textbook yet that doesn't have some glaring errors, and the
one I use in the Systems class has at least four that I have to issue
corrections on in the syllabus. And the writers of texts have found
that they don't sell the books that go into thousands of pages of
detail; the students have neither the inclination for it nor the time.
They have careers in other fields. So the textbook authors keep it
really simple in the hope that the student will be piqued enough to
dig further on his own. Most don't.
You an argue this as long as you want, like Mx, but it's all
book-learnin' and when the ground starts to come up at you real quick
it won't matter one bit. You WILL want to understand AOA and where you
went wrong.

I agree with everything you wrote except this last part and the part
about the 10-year-old. I have teaching experience myself in
electrical engineering, and mathematics, computer science, ...all, non-
trivial. I have found that very many complex things can be taught to
people while still remaining honest. Certainly there might not be
utlization of Maxwell's equations or partial-differential equations,
or red-black trees, but insight can be instilled that will give the
student an understanding that is both intutive and accurate. As the
student matures, the depth of understanding might increase, but it can
at least remain true. Schools try hard to do this, but since there
are so many students in class at once, each with different proclivity
to learn, the curriculum, by necessity, quickly suffers from rote
drill, as you hinted at. I remember being introduced to notion of
sqare-root of negative number in elementrary school. Then middle
school. Then again in high school. I never really understod them in
middle school because the teachers would not allow that. All the
students were in monkey mode. I also remember when I first did long
division, I and wanted to move on to what was next, and the teachers
would not allow it. I was forced to do hundreds of long-division
problems, one after the other, like a pencil monkey, even though it
was quite apparent what was going on. It was their way of keeping me
occupied.

This was OK for square-root of -1.

I do not think it is OK for flying. I want theory and the practice,
because with flying, I think it is more relevant. I don't want to be
in the cockpit flying around my friends and their children harboring
the secret that regarded the KT as an impediment to me having some fun
yankin' and bankin'. It's irresponsible. And if there is a crash due
to pilot error because of shallow understanding...

....that's simply unacceptable in my book, especially when I have
passengers.

-Le Chaud Lapin-

Le Chaud Lapin wrote in
ups.com:

On Oct 4, 1:51 pm, wrote:
On Oct 4, 10:47 am, Le Chaud Lapin wrote:

I could probably explain VOR to a 10-year-old, without ever
mentioning
things like counters, angular frequency, anisotropic radiation,
frequency bands, sub-carriers, convolution, etc....and my
explanation
would still be correct.

I doubt it. The ten-year-old, and most flight students,
have absolutely no frame of reference to understand any of this in
any
depth. I teach a College course on Aircraft Systems, and I have to
keep things really simple so they can grasp a few basics. If you are
an electrical engineer, and I've had a few in my classes, we can get
more into the workings of the VOR, but we leave all the others
yawning
and wondering if this is going to be on the final exam.
When we come to hydraulics, we talk about pressure, volume
and area and relate that to what we experience as kids playing with a
garden hose. The same analogy can be used to a limited extent when
explaining Ohm's Law. But now I encounter kids who grew up in
highrises and never squirted their sisters with a hose, so they have
more difficulty. Too much information, not enough relationship to
previous bases because there are none.
You have no frame of reference yet. When you start
getting
into violent departure stalls, skidding-turn spins, accelerated
stalls, spirals and the like, the sounds and forces start to make the
textbook stuff real. Sure, Jeppesen isn't always right. I haven't
found a textbook yet that doesn't have some glaring errors, and the
one I use in the Systems class has at least four that I have to issue
corrections on in the syllabus. And the writers of texts have found
that they don't sell the books that go into thousands of pages of
detail; the students have neither the inclination for it nor the
time.
They have careers in other fields. So the textbook authors keep it
really simple in the hope that the student will be piqued enough to
dig further on his own. Most don't.
You an argue this as long as you want, like Mx, but it's
all
book-learnin' and when the ground starts to come up at you real quick
it won't matter one bit. You WILL want to understand AOA and where
you
went wrong.

I agree with everything you wrote except this last part and the part
about the 10-year-old. I have teaching experience myself in
electrical engineering, and mathematics, computer science, ...all,
non-
trivial.



Yeah, show all that to yor win, dip****.



rash due
to pilot error because of shallow understanding...

...that's simply unacceptable in my book, especially when I have
passengers.



Never going to happen, Anthony


Bertie

Tina wrote:
Still waiting for the conservation of momentum derivation. My husband,
also trained as an engineer, casually remarked he didn't think you
could get from Newton's First Law to the that confirms my memory,
but we are both willing to have that belief rebutted.

You can't get conservation of momentum from F = m*a (or vice versa) since
the latter is not a statement about anything being conserved. But you can
get "For every force there is an equal opposite force" from conservation
of momentum, and vice versa, with a small number of assumptions. You can
use derivatives to derive one way and integration to derive the other.
Here are several conservation laws that share a common derivation,
starting with:

Center of Mass is Conserved
---------------------------
Center of mass of a closed system of particles of mass m1, m2, m3, ... mn
must remain fixed for all time, which with a suitable selection of
coordinate origins may be stated mathematically as:

(a) m1*x1 + m2*x2 + m3*x3 + ... = 0
m1*y1 + m2*y2 + m3*y3 + ... = 0
m1*z1 + m2*z2 + m3*z3 + ... = 0

Note that this doesn't say that, for example, x1 can't vary with time. It
only says that if it does then m1, m2, m3, x2 or x3 or other masses or
positions must somehow change so the left hand side still remains zero.

Momentum is Conserved
---------------------
If position with respect to time is continuous (no discontinuities; e.g.
no jumps) then we can take the time derivative of the above, yielding:

(b) m1*dx1/dt + m2*dx2/dt + m3*dx3/dt + ... = 0
(And so on for the other coordinate axis.)

This is of course just the conservation of momentum equations because
dx1/dt = Vx1, a velocity. Note that d(m1*x1)/dt would have been more
appropriate if the mass of particles varies with time.

Force is Conserved
------------------
Given the continuity assumption above, then we can keep taking time
derivatives of the above, yielding the next conservation statement:

(c) m1*d^2(x1)/dt^2 + m2*d^2(x2)/dt^2 + m3*d^2(x3)/dt^2 + ... = 0
(And so on for the other coordinate axis.)

This is of course just the old equal and opposite action statement in
mathematical form because d^2(x1)/dt^2 = ax1, an acceleration.

So if one claims any _one_ of the above conservation laws exists then the
other two appear to follow with only a small set of (presumably
reasonable) assumptions.

Of course, but the specific statement I wanted made clear had to do
with getting conservation of momentum from Newton's relationship
between force, mass, and acceleration. The OP claimed to be an
engineer, he was suggesting something I thought was unlikely and you
demonstrated that nicely.

Tina wrote:
Of course, but the specific statement I wanted made clear had to do
with getting conservation of momentum from Newton's relationship
between force, mass, and acceleration. The OP claimed to be an
engineer, he was suggesting something I thought was unlikely and you
demonstrated that nicely.

Didn't he say he was an electronics engineer? Unless he's doing work on
electromechanical devices I can see how one can get rusty on dynamics.

I'm not sure questions regarding lift belong in a piloting group anyway.
Fluid dynamics is a particularly difficult subject because it is easy to
overlook things, such as: if a wing accelerates air downward, then
according to conservation of momentum some other mass must be accelerated
upward.