The earth pulls down on the plane...

In article ,
Beryl wrote:

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
...and the plane pulls up on the earth.

The air pushes up on the plane and the plane pushes down on the air;
essentially transferring the earth's continuous flow of downward
momentum acting on the plane to a much greater mass of air.

That air keeps that downward momentum, diffusing it through more and
more volume...

...until it eventually transfers it back to the Earth; countering the
aircraft's upward pull on it.

I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
to name and post the answer back here.

Anyone game?
Send that to Scott Eberhardt.

http://home.comcast.net/~clipper-108/Professional.html
To email me:
Copy/Paste Send


Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage. You'll notice his email address at the top of that paper, the
same as on the webpage.

As the paper says, the amount of air below that is pushed is negligible.
See "the wrong-Newtonian description of lift" on page 3.

See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
the plane. The plane must, in turn, be pulled up. You imagined a plane
at the top of an air column, pushing down. It's more like a plane at the
bottom of a suction bubble, pulling down. Oh, you like differential
pressure, you don't like air to pull? Too bad, he talks about air
pulling on page 5.

Nothing is said about downwash continuing to the surface. The paper does
say that if a plane flies over a large scale, the weight of the airplane
would be measured. Excited?
Well, an acoustically levitated scale would register its own weight too.
Or turn that upside down, and the scale sees the earth's weight
acoustically levitated above the scale. Same thing, and no upwash or
downwash in sight, just a standing pressure wave with a scale caught at
a node between positive and negative.
Almost sort of like a wing between a strong little suction bubble and a
big weak pressure bubble. Is the wing almost sort of caught in a
standing wave? I don't know.
Oh, you should check out what he says in his book:

"The wing develops lift by transferring momentum to the air. Momentum is
mass times velocity. In straight and level flight, the momentum is
transferred toward the earth. This momentum eventually strikes the
earth."

http://books.google.com/books?id=wmu...ntcover&dq=und
erstanding+flight+anderson&cd=1#v=onepage&q=downwa sh&f=false

Page 11.
Er, right. His book "which targets the general public", rather than the
more technical paper "which targets physics students and teachers."

You think he rights things into his book which aren't true? You think
that simply because he makes the language more plain he's included
falsehoods?

Really?

I think so.

Even you don't believe that.


He never says *once* in his "more technical paper" that "The plane must,
in turn, be pulled up." That is you.

Correct. He never said the next sentence "You imagined a plane at the
top of an air column, pushing down" either.


I'm not responsible for what you imagine I'm thinking.


He does say in his "more technical paper":

"Lift requires power

When a plane passes overhead the formally still air gains a downward
velocity."

Read that over and over until you get it:

"When a plane passes overhead the formally still air gains a downward
velocity."

He actually says that? Still air always seems very casual to me.

Yes: that is the actually quote. Obviously an uncaught typo for the word
"formerly".

http://home.comcast.net/~clipper-108/Flightrevisited.pdf


He also says right at the top of this "more techical paper":

"This material can be found in more detail in Understanding Flight 1st
and 2nd editions by David Anderson and Scott Eberhardt, McGraw-Hill,
2001, and 2009"

Not on the pdf I downloaded.
http://home.comcast.net/~clipper-108/Lift_AAPT.pdf
Maybe you're looking at something else.

I was. This:

http://home.comcast.net/~clipper-108/Flightrevisited.pdf

In the one you looked at, he says this:

"It should not be surprising that wings also produce lift by
accelerating air in the downward direction."

And it also says this:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground. If the airplane were to fly over a large
scale the weight of the airplane would be measured. The earth does not
get lighter when the airplane takes off."

It also says this:

"One might ask how large m& is for a typical airplane. Take for example
the Cessna 172 that weighs about 2300 lb (1045 kg). Traveling at a
speed of 140 mph (220 km/h), and assuming an effective angle of attack
of 5 degrees, we get a vertical velocity for the air of about 11.5 mph
(18 km/h) right at the wing. If we assume that the average vertical
velocity of the air diverted is half that value then we calculate m& to
be on the order of 5 ton/s."

Please note if there is an average velocity downward, then the updrafts
in the tip vortices cannot possibly be cancelling out all the downward
motion.


IOW, the author of the "more technical paper" declares the book the more
detailed explanation.

I don't see any such notion on his webpage either.

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Alan Baker wrote:

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

In article ,
Beryl wrote:

Alan Baker wrote:

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

There was more than one PDF listed at the bottom of the page and neither
the one you cited nor the one I cited says that the air pulls the plane
up.

The one you cited does say:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground."

I can't help but notice that you snipped that along with a lot of other
text to which you obviously could not find an adequate reply...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

On Dec 11, 11:23*pm, Alan Baker wrote:
In article ,

*Beryl wrote:
Alan Baker wrote:

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

There was more than one PDF listed at the bottom of the page and neither
the one you cited nor the one I cited says that the air pulls the plane
up.

The one you cited does say:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground."

I can't help but notice that you snipped that along with a lot of other
text to which you obviously could not find an adequate reply...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Arguments like this could go on forever but solve little or nothing.
Along with the flamers who try to elevate themselves by dissing
everyone else, these scraps are the sort of thing that have ruined the
rec.aviation groups as a whole and have driven most of us to moderated
groups where this isn't tolerated. There are so few individuals
following this thread anymore that it's sad. Nothing is being solved,
and won't be.

Adherents to either Newton or Bernoulli have argued the sources of
lift at least since the Wright brothers did their thing, and probably
before that. It still hasn't been settled. There is downwash, for
sure, and that supports Newton, but Bernoulli's pressure differential
also causes that downwash as the air, accelerated over the top of the
wing, follows its curvature and leaves it at a descending angle.
Downwash. Big deal. Air has enormous damping properties and downwash
seldom reaches the surface, even from an airliner 100 feet up on final
approach. I regularly drive under the approach path of a large
airport, where the runway threshold is a few feet from the road, and I
never notice litter or dust blowing around after an airliner has
skimmed over and landed. Air resists movement and stops moving soon
after it has been agitated. That's not to say that downwash isn't
involved in lift; it very likely is, and since the air is supported by
the earth's surface, the airliner's flight does not reduce the earth's
gross weight while it's off the ground. And that would be true even if
Newton wasn't involved and only Bernoulli was.

Orchardists have used light aircraft, flying VERY low and slow with
considerable flap, over their fields on frosty nights to drive warmer
air from a few feet up down into the trees to try to prevent the
fruit's freezing. It's debatable as to the overall effectiveness of
the method. Cropsprayers also fly with the wheels practically in the
crop so that the downwash drives the spray into the plants. In both
cases, the flight is extremely low, so low that it's dangerous.
Spraying from 20 feet up is far less effective. The downwash is
already dissipated.

The Clark Y airfoil generates lift at angles of attack as low as minus
4 degrees. At that angle there is no reason to expect downwash of any
sort, yet lift is generated. The bottom of the airfoil is angled
upward at about seven degrees in such flight.

So the argument could go on and on with neither side convinced, like
it has on and off for the last ten years I've followed these groups,
and the net result will be a handful of angry posters and and
otherwise empty forum. Is that what we want?

Dan

In article
,
wrote:

On Dec 11, 11:23*pm, Alan Baker wrote:
In article ,

*Beryl wrote:
Alan Baker wrote:

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

There was more than one PDF listed at the bottom of the page and neither
the one you cited nor the one I cited says that the air pulls the plane
up.

The one you cited does say:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground."

I can't help but notice that you snipped that along with a lot of other
text to which you obviously could not find an adequate reply...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Arguments like this could go on forever but solve little or nothing.
Along with the flamers who try to elevate themselves by dissing
everyone else, these scraps are the sort of thing that have ruined the
rec.aviation groups as a whole and have driven most of us to moderated
groups where this isn't tolerated. There are so few individuals
following this thread anymore that it's sad. Nothing is being solved,
and won't be.

Adherents to either Newton or Bernoulli have argued the sources of
lift at least since the Wright brothers did their thing, and probably
before that. It still hasn't been settled. There is downwash, for
sure, and that supports Newton, but Bernoulli's pressure differential
also causes that downwash as the air, accelerated over the top of the
wing, follows its curvature and leaves it at a descending angle.
Downwash. Big deal. Air has enormous damping properties and downwash
seldom reaches the surface, even from an airliner 100 feet up on final
approach. I regularly drive under the approach path of a large
airport, where the runway threshold is a few feet from the road, and I
never notice litter or dust blowing around after an airliner has
skimmed over and landed. Air resists movement and stops moving soon
after it has been agitated. That's not to say that downwash isn't
involved in lift; it very likely is, and since the air is supported by
the earth's surface, the airliner's flight does not reduce the earth's
gross weight while it's off the ground. And that would be true even if
Newton wasn't involved and only Bernoulli was.

Orchardists have used light aircraft, flying VERY low and slow with
considerable flap, over their fields on frosty nights to drive warmer
air from a few feet up down into the trees to try to prevent the
fruit's freezing. It's debatable as to the overall effectiveness of
the method. Cropsprayers also fly with the wheels practically in the
crop so that the downwash drives the spray into the plants. In both
cases, the flight is extremely low, so low that it's dangerous.
Spraying from 20 feet up is far less effective. The downwash is
already dissipated.

The Clark Y airfoil generates lift at angles of attack as low as minus
4 degrees. At that angle there is no reason to expect downwash of any
sort, yet lift is generated. The bottom of the airfoil is angled
upward at about seven degrees in such flight.

So the argument could go on and on with neither side convinced, like
it has on and off for the last ten years I've followed these groups,
and the net result will be a handful of angry posters and and
otherwise empty forum. Is that what we want?

Dan

Dan, I appreciate your efforts, but the existence of lift absolutely
demands that there is downwash.

Lift is a force up on the plane. Where's it come from? The air.

Therefore there is a force down on the air from the plane.

Force *is* change of momentum with respect to time, so a force down on
the air means a change in the airs momentum downward.

Period. End. Full stop.

The fact that the downwash quickly spreads itself among more and more
air doesn't make that momentum go away. The law of conservation of
momentum tells it can't. It has literally never once been found to have
been violated. So while more air may now share the momentum, that only
means that the average speed of the air is reduced in inverse proportion
to the amount of air that is then moving.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

On 12/12/2009 2:01 PM, Alan Baker wrote:
In article
,
wrote:

On Dec 11, 11:23 pm, Alan wrote:
In astnet,

wrote:
Alan Baker wrote:

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

There was more than one PDF listed at the bottom of the page and neither
the one you cited nor the one I cited says that the air pulls the plane
up.

The one you cited does say:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground."

I can't help but notice that you snipped that along with a lot of other
text to which you obviously could not find an adequate reply...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Arguments like this could go on forever but solve little or nothing.
Along with the flamers who try to elevate themselves by dissing
everyone else, these scraps are the sort of thing that have ruined the
rec.aviation groups as a whole and have driven most of us to moderated
groups where this isn't tolerated. There are so few individuals
following this thread anymore that it's sad. Nothing is being solved,
and won't be.

Adherents to either Newton or Bernoulli have argued the sources of
lift at least since the Wright brothers did their thing, and probably
before that. It still hasn't been settled. There is downwash, for
sure, and that supports Newton, but Bernoulli's pressure differential
also causes that downwash as the air, accelerated over the top of the
wing, follows its curvature and leaves it at a descending angle.
Downwash. Big deal. Air has enormous damping properties and downwash
seldom reaches the surface, even from an airliner 100 feet up on final
approach. I regularly drive under the approach path of a large
airport, where the runway threshold is a few feet from the road, and I
never notice litter or dust blowing around after an airliner has
skimmed over and landed. Air resists movement and stops moving soon
after it has been agitated. That's not to say that downwash isn't
involved in lift; it very likely is, and since the air is supported by
the earth's surface, the airliner's flight does not reduce the earth's
gross weight while it's off the ground. And that would be true even if
Newton wasn't involved and only Bernoulli was.

Orchardists have used light aircraft, flying VERY low and slow with
considerable flap, over their fields on frosty nights to drive warmer
air from a few feet up down into the trees to try to prevent the
fruit's freezing. It's debatable as to the overall effectiveness of
the method. Cropsprayers also fly with the wheels practically in the
crop so that the downwash drives the spray into the plants. In both
cases, the flight is extremely low, so low that it's dangerous.
Spraying from 20 feet up is far less effective. The downwash is
already dissipated.

The Clark Y airfoil generates lift at angles of attack as low as minus
4 degrees. At that angle there is no reason to expect downwash of any
sort, yet lift is generated. The bottom of the airfoil is angled
upward at about seven degrees in such flight.

So the argument could go on and on with neither side convinced, like
it has on and off for the last ten years I've followed these groups,
and the net result will be a handful of angry posters and and
otherwise empty forum. Is that what we want?

Dan

Dan, I appreciate your efforts, but the existence of lift absolutely
demands that there is downwash.

Lift is a force up on the plane. Where's it come from? The air.

Therefore there is a force down on the air from the plane.

Force *is* change of momentum with respect to time, so a force down on
the air means a change in the airs momentum downward.

Period. End. Full stop.

The fact that the downwash quickly spreads itself among more and more
air doesn't make that momentum go away. The law of conservation of
momentum tells it can't. It has literally never once been found to have
been violated. So while more air may now share the momentum, that only
means that the average speed of the air is reduced in inverse proportion
to the amount of air that is then moving.


the horse has been dead for quite a while

In article ,
Ray Adair wrote:

On 12/12/2009 2:01 PM, Alan Baker wrote:
In article
,
wrote:

On Dec 11, 11:23 pm, Alan wrote:
In astnet,

wrote:
Alan Baker wrote:

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

There was more than one PDF listed at the bottom of the page and neither
the one you cited nor the one I cited says that the air pulls the plane
up.

The one you cited does say:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground."

I can't help but notice that you snipped that along with a lot of other
text to which you obviously could not find an adequate reply...

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Arguments like this could go on forever but solve little or nothing.
Along with the flamers who try to elevate themselves by dissing
everyone else, these scraps are the sort of thing that have ruined the
rec.aviation groups as a whole and have driven most of us to moderated
groups where this isn't tolerated. There are so few individuals
following this thread anymore that it's sad. Nothing is being solved,
and won't be.

Adherents to either Newton or Bernoulli have argued the sources of
lift at least since the Wright brothers did their thing, and probably
before that. It still hasn't been settled. There is downwash, for
sure, and that supports Newton, but Bernoulli's pressure differential
also causes that downwash as the air, accelerated over the top of the
wing, follows its curvature and leaves it at a descending angle.
Downwash. Big deal. Air has enormous damping properties and downwash
seldom reaches the surface, even from an airliner 100 feet up on final
approach. I regularly drive under the approach path of a large
airport, where the runway threshold is a few feet from the road, and I
never notice litter or dust blowing around after an airliner has
skimmed over and landed. Air resists movement and stops moving soon
after it has been agitated. That's not to say that downwash isn't
involved in lift; it very likely is, and since the air is supported by
the earth's surface, the airliner's flight does not reduce the earth's
gross weight while it's off the ground. And that would be true even if
Newton wasn't involved and only Bernoulli was.

Orchardists have used light aircraft, flying VERY low and slow with
considerable flap, over their fields on frosty nights to drive warmer
air from a few feet up down into the trees to try to prevent the
fruit's freezing. It's debatable as to the overall effectiveness of
the method. Cropsprayers also fly with the wheels practically in the
crop so that the downwash drives the spray into the plants. In both
cases, the flight is extremely low, so low that it's dangerous.
Spraying from 20 feet up is far less effective. The downwash is
already dissipated.

The Clark Y airfoil generates lift at angles of attack as low as minus
4 degrees. At that angle there is no reason to expect downwash of any
sort, yet lift is generated. The bottom of the airfoil is angled
upward at about seven degrees in such flight.

So the argument could go on and on with neither side convinced, like
it has on and off for the last ten years I've followed these groups,
and the net result will be a handful of angry posters and and
otherwise empty forum. Is that what we want?

Dan

Dan, I appreciate your efforts, but the existence of lift absolutely
demands that there is downwash.

Lift is a force up on the plane. Where's it come from? The air.

Therefore there is a force down on the air from the plane.

Force *is* change of momentum with respect to time, so a force down on
the air means a change in the airs momentum downward.

Period. End. Full stop.

The fact that the downwash quickly spreads itself among more and more
air doesn't make that momentum go away. The law of conservation of
momentum tells it can't. It has literally never once been found to have
been violated. So while more air may now share the momentum, that only
means that the average speed of the air is reduced in inverse proportion
to the amount of air that is then moving.


the horse has been dead for quite a while

The facts are the facts.

There is no upward force without a downward force.

An unbalanced for always accelerates that which it acts upon.

Momentum is always conserved.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

Alan Baker wrote:

So while more air may now share the momentum, that only
means that the average speed of the air is reduced in inverse proportion
to the amount of air that is then moving.

'Traveling at a speed of 140 mph, and assuming an effective angle of
attack of 5 degrees, we get a vertical velocity for the air of about
11.5 mph right at the wing.'
Eberhardt then assumes the average vertical velocity is half that. I'll
assume that *miles* away from the wing it's nothing.

In article ,
Beryl wrote:

Alan Baker wrote:

So while more air may now share the momentum, that only
means that the average speed of the air is reduced in inverse proportion
to the amount of air that is then moving.

'Traveling at a speed of 140 mph, and assuming an effective angle of
attack of 5 degrees, we get a vertical velocity for the air of about
11.5 mph right at the wing.'
Eberhardt then assumes the average vertical velocity is half that. I'll
assume that *miles* away from the wing it's nothing.

You can assume all you want...

....if you want to be wrong.

Fact: momentum is always conserved.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

On Dec 12, 2:27 pm, Alan Baker wrote:
In article ,
Eberhardt then assumes the average vertical velocity is half that. I'll
assume that *miles* away from the wing it's nothing.

You can assume all you want...

...if you want to be wrong.

Fact: momentum is always conserved.


See what I mean? Endless, endless back-and-forth. Miles away from the
wing it's nothing. Even a couple hundred yards away it's pretty much
undetectable apart from the sound. The air dampens all movement,
turning it into heat (due to friction between agitated molecules) and
nothing more. Newton is right, OK? For every action there is an equal
and opposite reaction. In our case, the air dissipates the action
(downwash) to such an extent that you are wasting time looking for it
anywhere but near the wing. You'd be better informed to look for a
temperature rise in the wake of the wing.

Dan