Backwash Causes Lift?

Morgans wrote:
"Morgans" wrote

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?

I forgot one important qualifier of the treadmill's operation.

It goes in the opposite direction of the intended direction of travel for
the airplane.

Oh god,. imagine having been hios spiritual teacher when he was
young.

Do dogs get into heaven, et al...







Bertie

Le Chaud Lapin wrote:
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.

Doesn#t matter how it works.

It does work, and lasts a long time. That#s all pilots need to know,
fjukkwit.





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.

And my guess is you´ßre going to be a permanent newbie to flying.



Bertie

Mxsmanic wrote:
Le Chaud Lapin writes:

I am not an expert either, but I know enough to know that the
explanations I am reading in books are, at best, misleading.

That's an open secret in aviation. The mechanism of lift has been widely
explained incorrectly for years.

Really_ i´ve nly seen you trying to explain it for a few months now.

Take up the baton from someone else, did you_

Bertie

Jim, I guess it depends on the institution and the intellegence of the
student. My husband graduated even longer ago than I did with degrees
in electronics, but he was well trained in mechanics as well. It may
be the newer schools don't offer as broad a base in classical
mechanics and physics.

What is especially interesting is that theories are offered that do
not predict observations very well. I skydived a few times, and my
sensation was that my arched body (the negative of a classic airfoil)
was being supported by a pillow of air, not being drawn up into a
partial vacuum. In fact if memory serves I don't remember the jump
suits of others bellowing in the back either.

And if one holds one's hand out of a car window, the psudo lift
provided by air deflecting from the surface facing the wind does not
seem to come from something at the trailing edge -- in fact one can
put one's wrist in the trailing position and still feel the same
impact -- delta momentum - forces.

For a theory to be accepted it has to predict observations. Trailing
edge downwash and some other things written here don't seem to do
that. But it is fun. Shall we talk about flying a kind of roll with
having the pilot experience exactly 1 G into the seat during the
sequence? That is about as much fun as talking about an airplane take
off from a belt sander, or taking off into a 70 KT headwind, turning
downwind and not falling out of the sky.




On Oct 4, 7:48 pm, Jim Logajan wrote:
Tina wrote:
Of course, but the specific statement I wanted made clear had to do
with getting conservation of momentum from Newton's relationship
between force, mass, and acceleration. The OP claimed to be an
engineer, he was suggesting something I thought was unlikely and you
demonstrated that nicely.

Didn't he say he was an electronics engineer? Unless he's doing work on
electromechanical devices I can see how one can get rusty on dynamics.

I'm not sure questions regarding lift belong in a piloting group anyway.
Fluid dynamics is a particularly difficult subject because it is easy to
overlook things, such as: if a wing accelerates air downward, then
according to conservation of momentum some other mass must be accelerated
upward.

Dudley Henriques wrote:
Tina wrote:
I thought it was called 100 kt tape, but if it walks like a duct and
talks like a . . . .


I'll have another glass of wine now..


Ouch!!! Could it be that Shakespeare was right?


"A duct by any other name would be just as sticky..."



TheSmokingGnu

On Oct 4, 6:58 pm, Bertie the Bunyip
wrote:
Le Chaud Lapin wrote:
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.

Doesn#t matter how it works.
It does work, and lasts a long time. That#s all pilots need to know,
fjukkwit.

Sounds like you've been using Viagra.

And my guess is you´ßre going to be a permanent newbie to flying.

Ess-Tsett and # symbols. Hmmm...

Either you're German, drunk, or both.

-Le Chaud Lapin-

Mxsmanic wrote:
Tina writes:

Interested readers might enjoy looking at alphatrainers.com for a
discussion of lift. Mx's assertion that lift is mostly the result of
downwash flies (pardon the pun) in the face of 'center of lift'
analysis which in effect is that point on the wing where if for
balance considerations the integrated upward forces were concentrated
they could be considered to be operating at a point. If downwash, the
center of action of which is somewhat aft of the following edge of the
wing, was the major contributer of lift, one would expect the center
of lift to be in that area -- aft of the wing. It's not.

I don't understand how you reached this conclusion. It's a bit like saying
that all of the planet Earth must be massless except for a dimensionless point
at its center, since that is where the center of gravity is.

But what do I know, I'm just a psychologist -- with a minor in
physics.

Knowledge is more important than credentials.

Ability is more important than either, fjukkwit#




Bertie

"Paul Riley" wrote

Hey, don't knock duct tape( we called it speed tape G). Kept water out
of my wing tank in Vietnam (Bird Dog) years ago. .50 cal rounds do a nasty
job, even on self sealing tanks. :-)))))

What the hey, even with one tank, for 2 hours, I still could fly the
thing. And did, for about 2 weeks.
:-)))))))))

I used to call it 200 MPH tape, because that's about how fast they go in
NASCAR. Then I got to know a Master Chief that was serving on carriers,
working on Hornets.

Then he tells me they were using it in the first Gulf War, and on F-18's, at
that! Now I have to call it 1,500 MPH tape!

No doubt that they are still using it now, for much the same purposes, I'll
bet.

1,500 MPH tape just doesn't have the same ring. It doesn't roll off the
tongue as smoothly. g

Wonderful stuff, huh?
--
Jim in NC

That is why we called it "speed tape"--fit all situations!!!! :-))))))

Paul
"Morgans" wrote in message
...

"Paul Riley" wrote

Hey, don't knock duct tape( we called it speed tape G). Kept water out
of my wing tank in Vietnam (Bird Dog) years ago. .50 cal rounds do a
nasty job, even on self sealing tanks. :-)))))

What the hey, even with one tank, for 2 hours, I still could fly the
thing. And did, for about 2 weeks.
:-)))))))))

I used to call it 200 MPH tape, because that's about how fast they go in
NASCAR. Then I got to know a Master Chief that was serving on carriers,
working on Hornets.

Then he tells me they were using it in the first Gulf War, and on F-18's,
at that! Now I have to call it 1,500 MPH tape!

No doubt that they are still using it now, for much the same purposes,
I'll bet.

1,500 MPH tape just doesn't have the same ring. It doesn't roll off the
tongue as smoothly. g

Wonderful stuff, huh?
--
Jim in NC

Morgans wrote:
"Paul Riley" wrote
Hey, don't knock duct tape( we called it speed tape G). Kept water out
of my wing tank in Vietnam (Bird Dog) years ago. .50 cal rounds do a nasty
job, even on self sealing tanks. :-)))))

What the hey, even with one tank, for 2 hours, I still could fly the
thing. And did, for about 2 weeks.
:-)))))))))

I used to call it 200 MPH tape, because that's about how fast they go in
NASCAR. Then I got to know a Master Chief that was serving on carriers,
working on Hornets.

Then he tells me they were using it in the first Gulf War, and on F-18's, at
that! Now I have to call it 1,500 MPH tape!

No doubt that they are still using it now, for much the same purposes, I'll
bet.

1,500 MPH tape just doesn't have the same ring. It doesn't roll off the
tongue as smoothly. g

That is because it isn't 1,500 MPH tape but rather Mach 2 tape!

Matt