Magnus Effect

Could well be Jim. Like I said that was what I understood.

Ian
"Jim Vincent" wrote in message
...
I understand that that is the limiting factor to helicopter forward
speed.( and why 'Airwolf' could never have worked ) At around 400 kph the
forward going blade starts to overcome the amount of control input
available

I thought is was because the forward blade is approaching supersonic.

Jim Vincent
N483SZ
illspam

Iwo Mergler wrote:

It's possible to use the effect in an but
there is no concept of an angle of attack and the
L/D ratio is quite bad at low RPM.
...

The first thing (no concept of an angle of attack) is a good
reason that no airplane may have success using this effect.
An essential condition for an heavier than air aircraft to be
controlable is that its lift coefficient (CL) increases with the
angle of attack. So that if anything disturbs it from its previous
path by an upward deviation the angle of attack is decreased, and so
the CL and the lift (because the other factor, the speed, needs time
to change due to inertia), so the weight becomes higher than the
lift and this gets the aircraft back to its initial path, similar
things in case of a downward deviation. This is why airplanes and
gliders become uncontrolable at stall angle of attack, not by
lack of lift, the CL is then at its maximum, but due to the impossibility
of increasing it further by increasing the angle of attack.

"Jim Vincent" wrote in message
...
I understand that that is the limiting factor to helicopter forward
speed.( and why 'Airwolf' could never have worked ) At around 400 kph the
forward going blade starts to overcome the amount of control input
available

I thought it was because the forward blade is approaching supersonic.

A one-off special version of the Westland Lynx has the record for
world's fastest conventional helicopter; it did 249 mph (401 kph),
albeit with special experimental rotor blades. Supersonic flow on the
advancing blade is a problem.

However a compound helicopter like the Lockheed Cheyenne AH-56
(stub wings and pusher prop in addition to main rotor blade)
or the XH-51A (pusher jet engine) could unload the main rotor and
do 250-300 mph.

I think the fictional Airwolf helicopter used pusher jets in
"supersonic" flight. IOW it was a compound helicopter, although
this wasn't clearly stated in the TV show. The Bell 222 it was modeled
on had stub wings for landing gear.

I don't know what the theoretical speed limit is for a compound
helicopter, but it's clearly faster than 400 kph.

But considering the difficulty of getting a winged plane to efficiently fly
supersonic, even if a supersonic compound helicopter was theoretically
possible, it's unlikely to be practical. There are better approaches, such
as tiltrotor up to about 350 mph (570 kph), and beyond that V/STOL
winged aircraft.

-- Joe D.

Both the advancing rotor blade and the retreating blade on a helicopter
cause problems limiting maximum airspeed.

In many case, it is the retreating blade that limits first. Retreating
blade stall is announced by rotor roughness and vibration. In fully
articulated rotor blades, the retreating blade flaps down to the limit.
Then, because of precession, the nose will pitch up and the helicopter will
roll over.

At about the same time, the advancing blade will be moving at close to the
speed of sound. A sharp rise in drag produces shock waves which can cause
structural damage.

A number of years ago, in England, a pilot and crew were testing a
helicopter. At 11,000 feet and an IAS of 46 knots, the helicopter was
deeply in the retreating blade stall. It did two barrel rolls so large that
at the end of the second roll the aircraft collided with the ground.
Miraculously, the pilot and crew member survived. (This information comes
from "Principles of Helicopter Flight" in the Retreating Blade Stall
section.)

I have heard there is a jet powered gyrocopter that can fly at 350 knots or
so. Gyrocopters eliminate a lot of problems facing helicopters, but they
are still not very good at soaring.

Colin N12HS


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Ian... you are not hitting the ball "square on" but in a slice (across) the
desired flight path of the ball.. hence the hook or slice path of the ball..
instead of imparting an "over the top" spin, the ball is spinning off at an
angle, as in the earths axis is tilted..

roger on the dimples... mind froze up that late at night..

BT

"tango4" wrote in message
...
Speak for your own balls! Golf balls that is. Mine don't climb
progressively in a straight line ahead but they do swing impressivelly
left or right!

:-)

The divots are called dimples by the way!

Ian


"BTIZ" wrote in message
news:MKldd.32193$bk1.30147@fed1read05...
Have not seen such an aircraft.. but the principle of the "magnus effect"
can be seen in the flight path of a golf ball... ever watch a golf ball
when first hit.. start out low and then increase the climb rate before
arcing over ?.. I'm not talking about a golf ball hit with a pitching
wedge... but hit with the driver.. the spin imparted is the same as the
rotating cylinder described.. creating "lift" over the top of the ball...
and yes.. all those little divots in the ball (I forget what they are
called) adds to the lifting effect.

BT

"COLIN LAMB" wrote in message
nk.net...
If a wing is replaced by a rotating cylinder, with the forward surface
rotating upward, lift will be produced. The local air velocity is high
on
top and low on the bottom. This upward force is known as magnus effect.

The information above comes from my helicopter handbook. The theory is
used
to explain some helicopter principles, but caused me to wonder more
about
it. Has anyone every produced an airplane using the magnus effect? If
the
cylinder is rotating faster, I would expect that lift would be
increased.
Does anyone know if there have been any writings and/or test aircraft?
Not
much use with a glider, for obvious reasons - but the answer would make
me a
bit smarter. I was not able to find much on the internet.

Thanks, Colin N12HS


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"COLIN LAMB" wrote:
If a wing is replaced by a rotating cylinder, with the forward surface
rotating upward, lift will be produced. The local air velocity is high on
top and low on the bottom. This upward force is known as magnus effect.

Has anyone every produced an airplane using the magnus effect? If the
cylinder is rotating faster, I would expect that lift would be increased.
Does anyone know if there have been any writings and/or test aircraft? Not
much use with a glider, for obvious reasons - but the answer would make me a
bit smarter. I was not able to find much on the internet.

Thanks, Colin N12HS

Well, not so much "produced" as "used". No writings about it (until
now), but it will easily fly across the living room.

Take the thin walled cardboard tube from inside a roll of gift
wrapping paper. Hold it so it is sticking straight out from your
body, with your right hand below the tube, and your left hand above
the tube, palms to the tube. I know this sounds a bit perverted, but
stick with me. Now spin the tube by pulling your hands away from each
other and give the tube a toss away from you and to the right.
Careful ot to crush the tube! It may take some time to get a good
launch technique, but the tube will fly.

Gyroscopic effects and an unbalanced tube can make the flight path a
bit erratic. Tried end plates, as the basic tube has no directional
or lateral stability. That was a disaster! And it made launching
much more difficult. Good for minutes of fun. Terrorize the dog or
cat. Great for removing ornaments from Christmas Trees. Paper towel
rolls and toilet paper rolls don't work so well. Not enough aspect
ratio.

Tried to get Wham-O to package and sell them as a 21st Century
Frisbee. Eventually put the whole idea in the same place as the Slim
Whittman wrist watches that yodel every hour. ;-)

Steve Leonard

"Steve" wrote in message
om...

Take the thin walled cardboard tube from inside a roll of gift
wrapping paper..... Tried to get Wham-O to package and sell
them as a 21st Century Frisbee....

About 20 yrs ago, something similar was marketed as
a flying tube. It was essentially a 1/2 height aluminum soda can,
open on both ends. The lip on one end was slightly weighted.
You threw it like a football, overhand with a side spin. The
tube's open axis was the flight path. It flew very well,
would go 200 feet. It was amazing to see such a low mass object
cut through the air so far. Don't remember the name.

-- Joe D.

On Wed, 20 Oct 2004 03:16:14 UTC, "COLIN LAMB"
wrote:

: If a wing is replaced by a rotating cylinder, with the forward surface
: rotating upward, lift will be produced. The local air velocity is high on
: top and low on the bottom. This upward force is known as magnus effect.

It's a simple illustration of the idea that vorticity/rotation
produces lift. Instead of inducing the rotation by the shape of the
section, you spin the cylinder and drag the air round with it.

: The information above comes from my helicopter handbook. The theory is used
: to explain some helicopter principles, but caused me to wonder more about
: it. Has anyone every produced an airplane using the magnus effect?

There's a shop in Covent Garden which sells magnus effect rotor-kites.
And you might like to look up the Flettner Rotor Ship, "Baden Baden"
(http://college.hmco.com/history/read...sh_009400_bade
nbaden.htm for example).

Ian

COLIN LAMB a écrit :
If a wing is replaced by a rotating cylinder, with the forward surface
rotating upward, lift will be produced. The local air velocity is high on
top and low on the bottom. This upward force is known as magnus effect.

The information above comes from my helicopter handbook. The theory is used
to explain some helicopter principles, but caused me to wonder more about
it. Has anyone every produced an airplane using the magnus effect? If the
cylinder is rotating faster, I would expect that lift would be increased.
Does anyone know if there have been any writings and/or test aircraft? Not
much use with a glider, for obvious reasons - but the answer would make me a
bit smarter. I was not able to find much on the internet.

No sailplanes, but a sailboat did navigate using rotary masts.

A similar effect is used on an helicopter instead of tail rotor (the
tail is not rotating but side lift is created from main rotor flow by
blowing air through on side or another )

A similar effect is used on an helicopter instead of tail rotor (the
tail is not rotating but side lift is created from main rotor flow by
blowing air through on side or another )


Callrd NOTAR

Jim Vincent
N483SZ
illspam