Backwash Causes Lift?

Dudley Henriques wrote:
Crash Lander wrote:
I'd like to see what his thoughts are on String Theory.
LOL.

I'm sure he'd most likely say that twine was better :-))


What, and discount the obvious implications that Duct Tape has on modern
thinking?

TheSmokingGnu

"Bertie the Bunyip" wrote

It´s the main reason I´m here.

Remind me again. What is the main reason you're here?

Why do you feel the need to answer his posts?
--
Jim in NC

Le Chaud Lapin wrote:
You can have lift of an object with no Bernoulli. It's simple vector
addition.

1. You are talking about nature's abhorrence of a vacuum.
2. Vacuum abhorrence is not lift.
3. Airplanes do not generate lift as a result of vacuum abhorrence.
----------
Conclusion: you are not talking about how aircraft generate lift.

QED.

TheSmokingGnu

TheSmokingGnu wrote:
Dudley Henriques wrote:
Crash Lander wrote:
I'd like to see what his thoughts are on String Theory.
LOL.

I'm sure he'd most likely say that twine was better :-))


What, and discount the obvious implications that Duct Tape has on modern
thinking?

TheSmokingGnu

Ah, duct tape!! Where would aviation be without it ?

--
Dudley Henriques

On Oct 3, 8:29 pm, wrote:
After all the years of reading this stuff and seeing wind-
tunnel demos and graphs and all such, I know there's an awful lot of
information out there on the generation of lift. Most of it is
available on the 'net. The strangest thing is the newbie who starts to
argue with his textbooks, very publicly (as on a newsgroup) without
Googling it for himself first. He knows better, he's sure.

What's strange is CFI'S (two of them) who did not know how to explain
VOR to an electrial engineer (me), who, after reading the discription
of how it works, could probably make after reading the technical
specs.

What's strange is one of the recognized leaders in flight training
materials using words like "energy" when they mean "power". I might
be a newbie to flying, but I'm not a newbie to physics.

-Le Chaud Lapin-

On Oct 3, 9:26 pm, TheSmokingGnu
wrote:
Le Chaud Lapin wrote:
You can have lift of an object with no Bernoulli. It's simple vector
addition.

1. You are talking about nature's abhorrence of a vacuum.
2. Vacuum abhorrence is not lift.
3. Airplanes do not generate lift as a result of vacuum abhorrence.
----------
Conclusion: you are not talking about how aircraft generate lift.

Yes, I am. It's a combination of many things taking place at once.
Vacuum generation by the forward motion of the wing is one of them.

QED.

-LCL-

On Oct 3, 8:38 pm, Tina wrote:
"We" are not in need of getting to the bottom of this. Most of us have
been there and done that.This particular writer, if she chooses to
analyse physics problems, tends to use the Newtonion approximations as
first principles. The good news is my profession doesn't demand those
skills often. I would, however, be interested, as I mentioned earlier,
how you derive conservation of mV from Newton's force/acceleration
relationship. I think you made that claim earlier in this thread.

Hmm...I was afraid you would say that.

A non-hand-waving explanation would too close to the quantum, and
so...it's a bit much to discuss, at least right now. I've posted more
messages in this thread in small period of time than I have ever for
any other topic, in the history of using USENET, or...as one might
say, dN/dt 0, where N is number of messages.

-Le Chaud Lapin-

Le Chaud Lapin wrote:
Yes, I am. It's a combination of many things taking place at once.
Vacuum generation by the forward motion of the wing is one of them.

Then why do wings generate lift at negative AOA? Surely the immense
vacuum pressures generated would immediately pull any flying craft
desperately into the Earth the moment the wing crossed that threshold
(say, in a descent).

My goodness, it's a good thing you got on here to tell us all this;
imagine all those airliners going overhead that have been doing it wrong
all this time, actually descending to a destination. They ought very
well to know that they could never do such a thing because the vacuum
pressures won't allow it!

TheSmokingGnu

On Oct 3, 9:26 pm, TheSmokingGnu
wrote:
Le Chaud Lapin wrote:
Yes, I am. It's a combination of many things taking place at once.
Vacuum generation by the forward motion of the wing is one of them.

And the other is the displacement of air downward.


Then why do wings generate lift at negative AOA? Surely the immense
vacuum pressures generated would immediately pull any flying craft
desperately into the Earth the moment the wing crossed that threshold
(say, in a descent).

Must be careful not to mix attitude up with angle of attack. The
path of the wing's chord line through the air determines AOA. If the
airplane is pointed downward a bit so that the chord line is down 2°
with respect to the horizon, and the descent path of the airplane is
3°, the AOA is still 1°. An airplane in a steep climb, with its nose
up 20°, does not have a 20° AOA. Its flight path is upward at maybe
10° so that its AOA is only 10°.

Some wings (thick, heavily cambered wings) will generate lift
at up to -4° AOA. The bottom surface of the wing is not the chord
line; that's the line between the leading and trailing edges. The
bottom surface might be angled downward even more in level flight. the
old Champ was a good example: the bottom surface was angled quite
visibly down in level cruise flight, but the chord line was still at a
positive degree or two.

Admittedly there are instructors who don't understand this
stuff well at all and think they know more than they do. I'm still
learning 34 years after starting to fly. I'm old enough now to realize
how little I knew when I thought I knew it all, and to know that I'll
now never have a good handle on it all. Too little time and too many
other responsibilities. But private pilots need to have the basics,
because that's all they have time for and because they'll kill
themselves without them. I'm appalled when I see a pilot do a low-and-
over and yank back hard for the vertical zoom. They have no idea how
close they come to an accelerated stall doing that. Those that manage
to get the stall don't live to avoid the same mistake again, and the
accident report gives a bland, uninteresting and uninformative "pilot
lost control in the climb after the low pass." They don't give the
real reason: the pilot did not understand AOA, never did, and thought
he was safe because the airplane's speed was well above the stall
speed.


Dan

It's curious. Nobody who's ever stood in the sllipstream of a
rotating propeller on a stationary plane says that a propeller merely
sucks an airplane through the sky. But people get into a tizzy if one
mentions Newton's third law wrt a wing. Bernoulli and Newton are not
alternatives; they are both universally and simultaneously the same
thing.

It's like those ladder-against-the- wall problems in Statics. The
forces don't change, but depending on what you're calculating,
sometimes you choose one reference point for your moments, sometimes
another.

Conservation of Energy: it's not just a good idea, it's the Law.

Don