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