Backwash Causes Lift?

On Oct 9, 8:10 am, Bertie the Bunyip wrote:
wrote oups.com:

On Oct 8, 3:58 pm, Mxsmanic wrote:
Bertie the Bunyip writes:
Fair enough, but the wing is behaving in exactly the same way.

The wings of fixed-wing aircraft behave the same way whether they are
gliders or powered.

Nope. The lift/drag vectors are different as the AOA
changes. The rest of Bernoulli/Newton still apply. For helicopter and
autogyro blades, the lift/drag vectors are similar except that in
autorotation there are propeller and autorotative regions of the
rotor.

OK, take your workd for it, but I thought Autogyros had pretty much
straight blades. Alpha is obviously going to be relative to distance to the
hub if the alpha is positive, but even so, you could look at it the same as
washout if I'm following you correctly.

Bertie

They do have straight blades, but the different velocities
found at various radii make the difference in AOA at thos points. In
forward flight it gets complicated. Here's a good link:
http://www.cartage.org.lb/en/themes/...torotation.htm
Some helicopters have washout in the blades, but there are
still the rotational/advancing/retreating/radius issues to deal with.
I find it most amazing that helicopters flew successfully not all that
long after the Wright Brothers. The Germans had a workable machine in
the late '30s.
I thought helicopters were easy-to-understand machines until I had to
study them for my AME license. I like complex machinery, and these
things fit the bill. I have a little dual in an R44 and have great
respect for the folks who fly such ornery animals. Keep ya busy in a
hover.

Dan

wrote in
oups.com:

On Oct 9, 8:10 am, Bertie the Bunyip wrote:
wrote
oups.com:

On Oct 8, 3:58 pm, Mxsmanic wrote:
Bertie the Bunyip writes:
Fair enough, but the wing is behaving in exactly the same way.

The wings of fixed-wing aircraft behave the same way whether they
are gliders or powered.

Nope. The lift/drag vectors are different as the AOA
changes. The rest of Bernoulli/Newton still apply. For helicopter
and autogyro blades, the lift/drag vectors are similar except that
in autorotation there are propeller and autorotative regions of the
rotor.

OK, take your workd for it, but I thought Autogyros had pretty much
straight blades. Alpha is obviously going to be relative to distance
to the hub if the alpha is positive, but even so, you could look at
it the same as washout if I'm following you correctly.

Bertie

They do have straight blades, but the different velocities
found at various radii make the difference in AOA at thos points.



OK, got it.


In
forward flight it gets complicated. Here's a good link:
http://www.cartage.org.lb/en/themes/...idDynamics/Fly
i
ngDynamics/Aerodynamics/Lowspeed/Helicopter/Autorotation/Autorotation.


I'll decline if you don't min! It's late and the things scare the crap
out of me anyway.

h
tm
Some helicopters have washout in the blades, but there are
still the rotational/advancing/retreating/radius issues to deal with.
I find it most amazing that helicopters flew successfully not all that
long after the Wright Brothers. The Germans had a workable machine in
the late '30s.

Well, the austrians were flying tethered contraption in WW1 and there
were som other dubious things, but I know about Achgelis and Flettner,
allright. Cool machines that are too often forgotten.

I thought helicopters were easy-to-understand machines until I had to
study them for my AME license. I like complex machinery, and these
things fit the bill. I have a little dual in an R44 and have great
respect for the folks who fly such ornery animals. Keep ya busy in a
hover.



Yes, I've tried em and also got OK with RC helis, but the cost of
keeping those going was nuts! The real thing doesn't interest me much.
Too expensive noisy and slow.


Bertie