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Backwash Causes Lift?



 
 
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  #21  
Old October 3rd 07, 12:06 PM posted to rec.aviation.piloting
gpaleo
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Posts: 34
Default Backwash Causes Lift?


Ο "Le Chaud Lapin" έγραψε στο μήνυμα
ups.com...

Hi,

Student pilot here, self-teaching using the Jeppensen Private Pilot
Kit after taking ground school.

..................................................
there is more to it than the way it is being described in context of

flying.]

-Le Chaud Lapin-



Hot Bunny ??????????????
ROTFLMAO

  #22  
Old October 3rd 07, 01:27 PM posted to rec.aviation.piloting
BDS[_2_]
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Posts: 149
Default Backwash Causes Lift?

"Mxsmanic" wrote
Le Chaud Lapin writes:

What is the definition of a stall anyway?


An abrupt loss of lift.


Son, for someone who continually chastises the pilots here for their lack of
knowledge, you sure can come up with some doozies yourself!

BDS


  #23  
Old October 3rd 07, 02:15 PM posted to rec.aviation.piloting
Dudley Henriques[_2_]
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Posts: 2,546
Default Backwash Causes Lift?

Bertie the Bunyip wrote:
Dudley Henriques wrote in newsaednT-q-
:

Le Chaud Lapin wrote:
Hi,

Student pilot here, self-teaching using the Jeppensen Private Pilot
Kit after taking ground school.

I read in the book that combustion "creates" energy, which is
technically not true, but I decided to ignore it since the pictures
are sooo pretty.

Now, in Chapter 3, section about airfoils, it actually says:

"In addition to the lowered pressure, a downward-backward flow of air
also is generated from the top surface of the wing. The reaction to
this downwash results in an upward force on the wing which

demnstrates
Newtons' third law of motion. This action/reaction principle also is
apparent as the airstream strikes the lwoer surface of the wing when
inclinded at a small angle (the angle of attack) to its direction of
motion. The air is forced downward and therefore causes an upward
reaction resulting in positive lift."

IMHO, the latter part of this paragraph is correct, but the former
part is wrong.

Obviously, any air above the wing can only result in a force downward
on top of the wing. The only force causing the plane to want to move
upward comes from beneath the wing. The effect of any air above the
wing is to cause rarefication above the wing, resulting in lower
pressure, thereby giving the 14.7lbs/in^2 (plus) to do its work. That
"reaction" coming from downward movement of air seems just plain

silly
to me.

I am also inclined to take issue with the explanations of

Bernouilli's
Principle which I see often in the literature, but that's a different
subject. [Note, I don't doubt Bernouilli's Principle, I just think
there is more to it than the way it is being described in context of
flying.]

-Le Chaud Lapin-

Please don't take this the wrong way but I'm sure you would have

passed
me up as a potential flight instructor.
:-))))



I nominate Anthony!

Bertie


Nah.....Anthony has offered many times to teach me about aerodynamics
and flying but so far at least I've cleverly managed to avoid that
enlightening experience.
:-))

--
Dudley Henriques
  #24  
Old October 3rd 07, 02:25 PM posted to rec.aviation.piloting
Tina
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Posts: 500
Default Backwash Causes Lift?

Then there's the Mx medical advice column, physics advice -- I'm
waiting for a unified field theory, or maybe a proposed standard of
care for depression.

I had a thought for what would be the longest thread ever in this
newsgroup -- "The collected corrections of Mx statements". Bertie
could be its editor, he has a deft and gentle way of pointing out
errors.


  #25  
Old October 3rd 07, 02:39 PM posted to rec.aviation.piloting
Tina
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Posts: 500
Default Backwash Causes Lift?

You wrote

On Oct 2, 9:57 pm, Le Chaud Lapin wrote:
Hi,

Student pilot here, self-teaching using the Jeppensen Private Pilot
Kit after taking ground school.

I read in the book that combustion "creates" energy, which is
technically not true, but I decided to ignore it since the pictures
are sooo pretty.

Now, in Chapter 3, section about airfoils, it actually says:

"In addition to the lowered pressure, a downward-backward flow of air
also is generated from the top surface of the wing. The reaction to
this downwash results in an upward force on the wing which demnstrates
Newtons' third law of motion. This action/reaction principle also is
apparent as the airstream strikes the lwoer surface of the wing when
inclinded at a small angle (the angle of attack) to its direction of
motion. The air is forced downward and therefore causes an upward
reaction resulting in positive lift."

IMHO, the latter part of this paragraph is correct, but the former
part is wrong.

Obviously, any air above the wing can only result in a force downward
on top of the wing. The only force causing the plane to want to move
upward comes from beneath the wing. The effect of any air above the
wing is to cause rarefication above the wing, resulting in lower
pressure, thereby giving the 14.7lbs/in^2 (plus) to do its work. That
"reaction" coming from downward movement of air seems just plain silly
to me.



You would do well to think in terms of differential pressure. If one
can by some means cause the pressure on the upper surface of the wing
to be 1 psi less than the pressure on the lower surface, there would
be an upward force on the wing of the order of 144 pounds per square
foot (my physics training, a million years ago, was in english units).

You might also want to think carefully about airfoil shapes, since
wings can provide lift when flying inverted. Any theory that does not
support inverted flight is obviously flawed.

But the neat thing to do is to hold your hand out of a moving car's
window, and feel the impact pressure on its surfaces as you tilt it in
the airstream. It's not that the hand is being "sucked" up, you don't
feel suction on the top surface, you feel push on the bottom one. Any
theory you develop had better be consistant with those observations.
Someone with more time than I have might like to start with the fact
that air weighs about .08 pounds per square foot near sea level, and
crack some numbers to show how that deflecting that mass can result in
lift even if the lifting surface has some funny shapes.




  #26  
Old October 3rd 07, 03:15 PM posted to rec.aviation.piloting
Le Chaud Lapin
external usenet poster
 
Posts: 291
Default Backwash Causes Lift?

On Oct 3, 8:39 am, Tina wrote:
You might also want to think carefully about airfoil shapes, since
wings can provide lift when flying inverted. Any theory that does not
support inverted flight is obviously flawed.


Actually I did because every book I read about flying skimped on the
subject. I'm going to hop over to MIT's OpenCourseWare later this
week and download their most basic course on aero/astro. Benoulli's
principle is toss around as if it were facecloth, but I'm getting the
feeling that no one is really doing the physics.

But the neat thing to do is to hold your hand out of a moving car's
window, and feel the impact pressure on its surfaces as you tilt it in
the airstream. It's not that the hand is being "sucked" up, you don't
feel suction on the top surface, you feel push on the bottom one. Any
theory you develop had better be consistant with those observations.
Someone with more time than I have might like to start with the fact
that air weighs about .08 pounds per square foot near sea level, and
crack some numbers to show how that deflecting that mass can result in
lift even if the lifting surface has some funny shapes.- Hide quoted text -


Yes it is. In fact, I was having this discussion with someone who
claimed that it *was* Benoulli's principle only. I made the following
diagram to try to illustrate my point. View in fixed width


| inverted |
| table |
|--------------------|

|--------------------|
| upright |
| table |

The Bernoulli people often describe air flowing above the a table
being faster than air below a table, and therefore, pressure is
reduced. Hmmm... what happens if the horizontal velocities above and
below a table are both essentially 0?

If you place an inverted table on top of an upright table so that the
table tops are mated, then have a machine, with a tremendous amount of
force, on the order of 14.4lbs/in^2 of force, yank the inverted table
upward, in one quick jerk, I contend that the lower table will be
strongly inclined to follow by jumping updward, obviously due to
pressure beneath it. So any type of rarefication on one side of a
doubly-pressurized surface that is free to move in direction that is
perpendicular to the surface, will, indeed, move, if pressure is
reduced.

And this is why, I am pretty sure, that if I were to search the web,
one would find people who are fanatical about the leading edges of
wings, in the most minute detail, because it is not simply the length
of the top of the wing that matters, but the amount of pinching, and
the distribution of air as it flows backward from the pressure point.
IMO, that pinching results in displacement of the air above to make it
effective go backwares, causing rarefication.

-Le Chaud Lapin-







  #27  
Old October 3rd 07, 03:27 PM posted to rec.aviation.piloting
Dudley Henriques[_2_]
external usenet poster
 
Posts: 2,546
Default Backwash Causes Lift?

Tina wrote:
Then there's the Mx medical advice column, physics advice -- I'm
waiting for a unified field theory, or maybe a proposed standard of
care for depression.

I had a thought for what would be the longest thread ever in this
newsgroup -- "The collected corrections of Mx statements". Bertie
could be its editor, he has a deft and gentle way of pointing out
errors.



I love Bertie's personal rendition of Occam's Razor to Anthony's long
extended posts where he "explains" everything in intimate and minute detail.

"Nope"!


--
Dudley Henriques
  #28  
Old October 3rd 07, 04:34 PM posted to rec.aviation.piloting
[email protected]
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Posts: 1,130
Default Backwash Causes Lift?

On Oct 3, 8:15 am, Le Chaud Lapin wrote:

Actually I did because every book I read about flying skimped on the
subject. I'm going to hop over to MIT's OpenCourseWare later this
week and download their most basic course on aero/astro. Benoulli's
principle is toss around as if it were facecloth, but I'm getting the
feeling that no one is really doing the physics.


Lemme see: People have been building flying machines since the late
1800's, about 125 years now, and none of them have been interested
enough in the phenomenon of lift to do the physics? How old are you,
anyway? Many of the contributors here have been flying much longer
than you have likely been alive and have studied this in detail, and
some of them might even have doctorates in the subject. The subject of
lift has been beaten to death on this forum and if you Googled it
you'd find some good information.
Both Newton and Bernoulli are correct. Even inside a pipe the
static pressure drops as velocity increases. That's why your bottom
table jumps as you yank off the top one: you accelerated an airflow.
And in generating lift there's a displacement of air. Can't escape
that at all.
The stagnation point on a leading edge isn't right at the front.
It's slightly below the wing, and as AOA increases it moves back
underneath quite a bit. It's not all intuitive, you see, and that
intuitive understanding of some of this stuff is where people get all
messed up and think they have the answers that have escaped all the
other experts all these years. We run into this attitude rather
frequently in the flight training industry. It tends to make the
student unteachable.

Dan



  #29  
Old October 3rd 07, 04:37 PM posted to rec.aviation.piloting
Bertie the Bunyip[_19_]
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Posts: 3,851
Default Backwash Causes Lift?

Dudley Henriques wrote in
:

Bertie the Bunyip wrote:
Dudley Henriques wrote in newsaednT-q-
:

Le Chaud Lapin wrote:
Hi,

Student pilot here, self-teaching using the Jeppensen Private Pilot
Kit after taking ground school.

I read in the book that combustion "creates" energy, which is
technically not true, but I decided to ignore it since the pictures
are sooo pretty.

Now, in Chapter 3, section about airfoils, it actually says:

"In addition to the lowered pressure, a downward-backward flow of

air
also is generated from the top surface of the wing. The reaction to
this downwash results in an upward force on the wing which

demnstrates
Newtons' third law of motion. This action/reaction principle also

is
apparent as the airstream strikes the lwoer surface of the wing

when
inclinded at a small angle (the angle of attack) to its direction

of
motion. The air is forced downward and therefore causes an upward
reaction resulting in positive lift."

IMHO, the latter part of this paragraph is correct, but the former
part is wrong.

Obviously, any air above the wing can only result in a force

downward
on top of the wing. The only force causing the plane to want to

move
upward comes from beneath the wing. The effect of any air above

the
wing is to cause rarefication above the wing, resulting in lower
pressure, thereby giving the 14.7lbs/in^2 (plus) to do its work.

That
"reaction" coming from downward movement of air seems just plain

silly
to me.

I am also inclined to take issue with the explanations of

Bernouilli's
Principle which I see often in the literature, but that's a

different
subject. [Note, I don't doubt Bernouilli's Principle, I just think
there is more to it than the way it is being described in context

of
flying.]

-Le Chaud Lapin-

Please don't take this the wrong way but I'm sure you would have

passed
me up as a potential flight instructor.
:-))))



I nominate Anthony!

Bertie


Nah.....Anthony has offered many times to teach me about aerodynamics
and flying but so far at least I've cleverly managed to avoid that
enlightening experience.
:-))


Be a bit like letting a jackhammer operator do your teeth, that.

Bertie
  #30  
Old October 3rd 07, 04:38 PM posted to rec.aviation.piloting
Bertie the Bunyip[_19_]
external usenet poster
 
Posts: 3,851
Default Backwash Causes Lift?

Tina wrote in news:1191417912.483823.271490
@g4g2000hsf.googlegroups.com:

Then there's the Mx medical advice column, physics advice -- I'm
waiting for a unified field theory, or maybe a proposed standard of
care for depression.

I had a thought for what would be the longest thread ever in this
newsgroup -- "The collected corrections of Mx statements". Bertie
could be its editor, he has a deft and gentle way of pointing out
errors.




He's an idiot, what else does one need to know?


Bertie
 




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