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

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

On Oct 3, 1:57 pm, Le Chaud Lapin wrote:

"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."


I blame the lift pixies myself

On Oct 2, 10:33 pm, george wrote:
On Oct 3, 1:57 pm, Le Chaud Lapin wrote:

"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."

I blame the lift pixies myself

LOL.

This flying business is a bit too fascinating. I'm having trouble
concentrating on my day job. In no other hobby has the opportunity
arisen to apply essentially everything technical I have ever learned.
Physics, chemistry, mathematics, electronics, computation...it's all
there.

-Le Chaud Lapin-

On Tue, 02 Oct 2007 20:33:46 -0700, george wrote:

On Oct 3, 1:57 pm, Le Chaud Lapin wrote:

"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."


I blame the lift pixies myself

I thought it was how the airflow goes through the splaps?

Le Chaud Lapin writes:

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.

Lift is a reaction to the force required to push air downward behind the wing
(downwash). How the air gets pushed downward is not very important. The wing
twists air into a downwash as it passes through it, leaving a swath of air
moving gently downward behind it. The force required to do this engenders an
equal and opposite force that is lift. Lift accelerates the wing upward,
counteracting gravity. The wing accelerates a large mass of air downward.

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.]

There are a lot of different ways to examine and describe the aerodynamics of
lift. It boils down to accelerating one mass (a mass of air) downward, which
engenders another acceleration of another mass (the wing, and anything to
which it is attached) upward. Any flat surface moving relative to the air
with a positive angle of attack below the stall angle will generate lift.

Mxsmanic wrote in
:

Le Chaud Lapin writes:

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.

Lift is a reaction to the force required to push air downward behind
the wing (downwash). How the air gets pushed downward is not very
important. The wing twists air into a downwash as it passes through
it, leaving a swath of air moving gently downward behind it. The
force required to do this engenders an equal and opposite force that
is lift. Lift accelerates the wing upward, counteracting gravity.
The wing accelerates a large mass of air downward.

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.]

There are a lot of different ways to examine and describe the
aerodynamics of lift. It boils down to accelerating one mass (a mass
of air) downward, which engenders another acceleration of another mass
(the wing, and anything to which it is attached) upward. Any flat
surface moving relative to the air with a positive angle of attack
below the stall angle will generate lift.


Nope.


Bertie

It is clearly time to revisit airplanes taking off on tredmills.

Tina wrote in news:1191401433.827965.190080
@o80g2000hse.googlegroups.com:

It is clearly time to revisit airplanes taking off on tredmills.




Do tell. Must have been before my time here.

Bertie

It is clearly time to revisit airplanes taking off on tredmills.

I have to agree. ANYTHING would be better than hearing the resident idiot
troll's blithering.

It goes something like this.

An airplane is about to takeoff on a runway, that is really a treadmill; a
very expensive treadmill.

The treadmill senses the airplane's speed, and matches the aircraft's speed,
with speed increases of its own.

Can the airplane takeoff? Why or why not?
--
Jim in NC