Backwash Causes Lift?

flightoffancy wrote in news:MPG.2172cb3db6410d90989680
@news-server.hot.rr.com:

In article . com,
says...
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.

JC, you're confusing yourself.

Instead of focusing on "fixed" wing, think for a moment about
helicopter
blades and propellers. These are airfoils not fundamentally different
than one attached to the side of an aircraft.

Anyone who has ever seen video of a helicopter hovering or has been
near
a helicopter hovering knows that air is being pushed down by the
blades
with massive force and that is the equal and opposite force exerted by
the mass of air on the bottom of the blades that keeps the helicopter
from falling out of the sky.

A fixed wing aircraft is only different in that it pushes air under it
by moving forward, rather than in a circle.

The bottom line is simple: an airplane can only stay aloft by pushing
air down.

Yes, the angle of attack gives the greater impulse to knock the air
downward. But a curved upper surface gives even more downard force to
the air.

Nit-picking Jeppensen's watered down description, which was not
authored
for aeronautical engineers (which I note you are NOT), will not
advance
your piloting skills in any significant way.





Nope, wrong.


Bertie