Backwash Causes Lift?

Dan Luke writes:

Then why does the wing stall and cease lifting when flow separates from the
upper surface?

Because it is no longer accelerating air efficiently downward.

On 3 Oct, 05:54, Mxsmanic wrote:
Dan Luke writes:
Then why does the wing stall and cease lifting when flow separates from the
upper surface?

Because it is no longer accelerating air efficiently downward.

Wrong again, fjukktard.


Bertei

Dan Luke wrote:
"Le Chaud Lapin" wrote:

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.


Then why does the wing stall and cease lifting when flow separates from the
upper surface?



It doesn't cease lifting. It doesn't lift as hard, and not hard enough
to support the airplane, but the force doesn't magically go away.

Matt

"Dan Luke" wrote in
:


"Le Chaud Lapin" wrote:

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.


Then why does the wing stall and cease lifting when flow separates
from the upper surface?



Actually, that's not the definition of the stall, seperation occurs just
after the stall with most airfoil/planform combinations and in most
flight situations, ordinarily. Some wings will have seperation at the
stall, but I've never flown one.
The defintion is an abrupt loss of lift when the critical angle is
reached. Seperation usually occurs immidiatly after (*but not always,
for instance, deltas will continue to have smooth flow way below he
point they will actually keep flying) This is not to be confused with
the back siide of the drag curve, BTW.
Having said all hat, there are some reputable design texts that define
stall as the point at which the bubble breaks down and buffet occurs and
as far as I know, this doesn't disturb engineers (of which I am not one,
BTW, so take this all with a large grain of salt) any more than a "po-
tay-to, po-tah-to" argument would.
Bottom line is you're interested in keeping your airplane from going
down and the point at which the wing ceases to do what you would like it
to do is the point at which you're most interested.

Make sense? If it does I must not have explained it well.



Bertie

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.
:-))))


--
Dudley Henriques

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

On Oct 2, 10:24 pm, Bertie the Bunyip wrote:
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!

Heh.

I knew going into ground school that the focus would be flying, not
aero/astro, so I was not disappointed with the course. By rushing us,
the instructor gave us a broad overview of what we should know. This
has been hugely beneficial for my learning.

Makes going through it again, slowly, with physics book nearby very
pleasurable.

-Le Chaud Lapin-

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

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.

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