Fast helicopters

I am sorry, but there is no video of this model. Nearly each helicopter
company has made trials with adding wings to their machines and all dropped
them again. During the hoverig the additional wing acts as a balast only and
reduces the hover efficiency of the machine. The heavy disk is able to store
a lot of kinetic energy, which allows vertical landing in autorotation.

George
wrote in message
...

I still seriously doubt that such a craft would be practical or even
possible. Is there video of this model flying on the net somewhere?

In any case, simply adding wings to the side of a helicopter will
increase its maximum forward speed significantly without the nead for
a heavy disk and complex control systems.

Dennis.

"George Vranek" wrote:

When flying forward, the Diskrotor Helicopter disk plane has a positive
pitch angle relative to the ground. The thrust necessary for forward
flight
is provided by the jet stream and not by the rotor as a conventional
helicopter does. A model acc.to your proposal has flown stright and
level 5
years ago. The disk airfoil has similar abilities as a conventional
airfoil
with a partially open split flap, which are surprisingly good. See Ira
H.
Abbot: Theory of Wing Sections or similar.

George

wrote in message
...
"George Vranek" wrote:

helicopters. Please have a look at www.vranek.ch/diskrotor.htm and
publish

The diskrotor/diskCopter has been discussed here before. The
conclusion was that it was impractical and probably impossible. When
flying forward, the normal helicopter disk plane has a negative pitch
angle relative to the ground. Putting a huge round airfoil up there
with a negative pitch angle would make you crash and not fly faster.
Not only that, but the disk "airfoil" would not really be a very good
airfoil with the same shape on both ends would it. If you disagree, I
suggest you build a model and fly it faster than 100 mph and see what
happens.

Dennis.


Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm




Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

Any extra weight, including wings, will act as ballast. The thing is
that if you want a fast helicopter, you have to pay for it somehow.
That big disk on top of your diskcopter is a heck of a huge ballast
too.

The simplest way to make a helicopter go faster is to simply increase
the rotor rpm. That way, the differential of lift as the helicopter
goes faster and faster is less significant than a slower turning
rotor. That is, at 400 mph tip speed and at 100 mph forward velocity,
you have a 200 mph differential or 50% of the tip speed. At 1000 mph
tip speed, you still have a 200 mph differential speed but its only
20% of the tip speed.

So in this example, a helicopter with a 1000 mph tip speed could go
forward at 250 mph before hitting 50% differential.

I'm not sure what the actual tip speed is, but I know that a lot of
modern fully articulated systems run at tip speeds just under the
speed of sound in order to significantly reduce the chances of ground
resonance.

Dennis.

"George Vranek" wrote:

I am sorry, but there is no video of this model. Nearly each helicopter
company has made trials with adding wings to their machines and all dropped
them again. During the hoverig the additional wing acts as a balast only and
reduces the hover efficiency of the machine. The heavy disk is able to store
a lot of kinetic energy, which allows vertical landing in autorotation.

Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

wrote in
:

I'm not sure what the actual tip speed is, but I know that a lot of
modern fully articulated systems run at tip speeds just under the
speed of sound in order to significantly reduce the chances of ground
resonance.

Do you mean at a hover? I don't think that's the case. If the tip speed
is just below supersonic at a hover, then at a very low forward airspeed
they'd go supersonic, & all kinds of bad things would happen, not the least
being huge amounts of noise, which is already the bane of helicopters.
Rotors have to be far below supersonic at a hover so the leading blade
doesn't go supersonic in fast cruise. Even the UH1 blades can approach
supersonic near Vne, and the tailrotor blades are close all the time.

--
Regards,

Stan

wrote in message
...

The simplest way to make a helicopter go faster is to simply increase
the rotor rpm. That way, the differential of lift as the helicopter
goes faster and faster is less significant than a slower turning
rotor. That is, at 400 mph tip speed and at 100 mph forward velocity,
you have a 200 mph differential or 50% of the tip speed. At 1000 mph
tip speed, you still have a 200 mph differential speed but its only
20% of the tip speed.

So in this example, a helicopter with a 1000 mph tip speed could go
forward at 250 mph before hitting 50% differential.

I'm not sure what the actual tip speed is, but I know that a lot of
modern fully articulated systems run at tip speeds just under the
speed of sound in order to significantly reduce the chances of ground
resonance.

Dennis.

Real helicopters use a tip speed on the order of 700-800 ft/sec (475-545
mph), well below the speed of sound. This has nothing to do with ground
resonance. It is driven by blade loads, vibration & stability, and noise at
high speeds.

The fully articulated hub design is susceptable to ground resonance
when landing. By increasing the rotor speed to just under the speed
of sound, that is, so nothing goes faster than the speed of sound even
at max forward velocity, the risk of ground resonance when landing is
significantly reduced. There are other advantages to speeding up a
fully articulated hub, but not flying apart when you land is a big
one.

Dennis.


"mm" wrote:

Real helicopters use a tip speed on the order of 700-800 ft/sec (475-545
mph), well below the speed of sound. This has nothing to do with ground
resonance. It is driven by blade loads, vibration & stability, and noise at
high speeds.



Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

wrote in message
...

The fully articulated hub design is susceptable to ground resonance
when landing. By increasing the rotor speed to just under the speed
of sound, that is, so nothing goes faster than the speed of sound even
at max forward velocity, the risk of ground resonance when landing is
significantly reduced. There are other advantages to speeding up a
fully articulated hub, but not flying apart when you land is a big
one.

Dennis.
You clearly don't know anything about ground resonance. It has little or
nothing to do with the blade tip Mach number.

"mm" wrote:

You clearly don't know anything about ground resonance. It has little or
nothing to do with the blade tip Mach number.

I don't pretend to be a fully articulated hub expert, but this is not
something I made up. It comes from an FAA inspector who makes his
living flying all sorts of helicopters. He IS an expert. Are YOU an
FAA inspector? Are you qualified to say that he is mistaken?

Think about the word "resonance". Do resonance and frequency go hand
in hand? By increasing the rotor RPM, do you increase the frequency
of rotation? Of course you do, its the same thing. If you sing a
perfect pitch into a tuning fork, does it also vibrate at resonance?
Yes. If you sing at a non-resonant frequency, does it still vibrate?
No. Are marching soldiers told to break step when crossing a bridge?
Yes. Why? Resonance. Think about this and what ground resonance
actually is.

Before you say this guy doesn't know anything about what he does for a
living, I suggest that you think about it a little while.

Dennis.



Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

"A RECESSION is when you know somebody who is out of work.
A DEPRESSION is when YOU are out of work.
A RECOVERY is when all the H-1B's are out of work."
To find out what an H-1B is and how they are putting
Americans out of work, visit the following web site
and click on the "Exporting America" CNN news video:
http://zazona.com/ShameH1B/MediaClips.htm

wrote in message
...
"mm" wrote:

You clearly don't know anything about ground resonance. It has little
or
nothing to do with the blade tip Mach number.

I don't pretend to be a fully articulated hub expert, but this is not
something I made up. It comes from an FAA inspector who makes his
living flying all sorts of helicopters. He IS an expert. Are YOU an
FAA inspector? Are you qualified to say that he is mistaken?

Think about the word "resonance". Do resonance and frequency go hand
in hand? By increasing the rotor RPM, do you increase the frequency
of rotation? Of course you do, its the same thing. If you sing a
perfect pitch into a tuning fork, does it also vibrate at resonance?
Yes. If you sing at a non-resonant frequency, does it still vibrate?
No. Are marching soldiers told to break step when crossing a bridge?
Yes. Why? Resonance. Think about this and what ground resonance
actually is.

Before you say this guy doesn't know anything about what he does for a
living, I suggest that you think about it a little while.

Dennis.

Yes, as a matter of fact I am qualified to say he is mistaken. I can
guarantee you that I know MUCH more about ground resonance than you or your
source. I challenge you to find a single reputable reference (text book,
technical paper, certification documentation, FAA training material, etc.)
that relates ground resonance directly to tip Mach number. Your source may
be the worlds ultimate helicopter pilot, but I don't think that this is much
of credential with respect to rotor aeromechanics and structural dynamics.

The original analysis of helicopter ground resonance was by Coleman and
Fiengold, NACA TN 3844. Read it, and will not find any mention of tip Mach
number.

Your tuning fork and marching soldiers examples are essentially meaningless
in this context.