In article ,
Beryl wrote:

snip

No downwash, no lift. No go learn something.
Let's learn here. From you. Is that 90 degree turn *exactly* the same as
a 180 degree turn that directs incoming air back in the opposite
direction?

Read this:

"To determine [the angle represented by a greek letter in the original
text], we observe that no downwash is generated when the wing generates
no lift."

I'm not disagreeing with that. I'll rephrase it, and say no circulation
is generated. It is not even relevant.

http://www.aoe.vt.edu/~cwoolsey/Cour...al/Aerodynamic
Properties.pdf

Read it over and over again until you get it.

Get what? It's about wings and geometry. Find something about air moving
through air.

http://www.onemetre.net/Design/Downwash/Downwash.htm

"The theory of downwash starts by noting that you only get downwash when
you have lift.* No lift, no downwash."

http://amasci.com/wing/airfoil.html

' The "Newton" explanation is wrong because downwash occurs BEHIND the
wing, where it can have no effects? Downwash can't generate a lifting
force? INCORRECT.

Wrong, and silly as well! The above statement caught fire on the
sci.physics newsgroup. Think for a moment: the exhaust from a rocket
or a jet engine occurs BEHIND the engine. Does this mean that
action/reaction does not apply to jets and rockets? Of course not.
It's true that the exhaust stream doesn't directly push on the inner
surface of a rocket engine. The lifting force in rockets is caused
by acceleration of mass, and within the exhaust plume the mass
is no longer accelerating. In rocket engines, the lifting force
appears in the same place that the exhaust is given high velocity:
where gases interact inside the engine.

And with aircraft, the lifting force appears in the same place that
the exhaust (the downwash) is given high downwards velocity. If a
wing encounters some unmoving air, and the wing then throws the air
downwards, the velocity of the air has been changed, and the wing
will experience an upwards reaction force. At the same time, a
downwash- flow is created. To calculate the lifting force of a
rocket engine, we can look exclusively at the exhaust velocity and
mass, but this doesn't mean that the rocket exhaust creates lift.
It just means that the rocket exhaust is directly proportional to
lift (since the exhaust velocity and the lifting force have a
common origin.) The same is true with airplane wings and downwash.
To have lift at high altitudes, we MUST have downwash, and if we
double the downwash, we double the lifting force. But downwash
doesn't cause lift, instead the wing's interaction with the air
both creates a lifting force and gives the air a downwards velocity
(by F=MA, don't you know!)'

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg