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Why do gyros use tilt head rather than swashplate



 
 
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  #1  
Old July 21st 03, 09:21 AM
Phillip
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Default Why do gyros use tilt head rather than swashplate

Would a gyro with a swashplate ( just for pitch control) fly any different
(better,worse) than using a tilt type rotor head? Just more complex?

Also, I've seen some photos of early kit helicopters that appear to have
just a tilting head (no way to auto-rotate ?). Isn't this a bit of a death
wish? Does a helicopter need to have collective pitch for anything other
than auto-rotaion?

Silly questions, but it's a late night.


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  #2  
Old July 22nd 03, 12:52 AM
Phillip
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Default


"Rhodesst" wrote in message
...
Power adjustments. Wally


Power adjustments? I don't see the difference a swashplate over a tilt

head
for cyclic control would make to a gyros rotor system. Care to explain
further?

OTOH, I think that sport gyros today use the tilt rotor hub because it's a

very
simple design, and it works very well. No swashplate and associated

linkages,
not to mention the fact that there's no need for individual feathering

hinges
on the rotor blades themselves. Much less to go wrong and/or maintain.

JMO,
Fly Safe,
Steve R.


The K.I.S.S. formula at it's best.

So why not on a helicopter? (Like those old kits I mentioned). I'm assuming
because you'd lose auto-rotation?


  #3  
Old July 22nd 03, 01:43 AM
Phil Miller
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On Mon, 21 Jul 2003 01:21:13 -0700, "Phillip" wrote:

Would a gyro with a swashplate ( just for pitch control) fly any different
(better,worse) than using a tilt type rotor head? Just more complex?


Just more complex. The net effect would be the same. Increase the angle
of attack 90 degrees before desired disc upward movement, decrease AoA
90 degrees before. Gyroscopic precession then makes the desire movement
happen.

Also, I've seen some photos of early kit helicopters that appear to have
just a tilting head (no way to auto-rotate ?). Isn't this a bit of a death
wish? Does a helicopter need to have collective pitch for anything other
than auto-rotaion?


Helicopter collective increase/decreases pitch angle of all blades
collectively and thereby increases/decreases lift. Pull collective up,
go up. lower collective, go down. It's a bit more complex than that, but
I'll leave that to the experts here.

Silly questions, but it's a late night.



Phil
--
Definitions of a pilot - No. 1

The average pilot, despite the sometimes swaggering exterior,
is very much capable of such feelings as love, affection,
intimacy and caring.
These feelings just don't involve anybody else.
US Navy Times
  #4  
Old July 22nd 03, 02:08 AM
Stan Gosnell
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"Phillip" wrote in
:

Also, I've seen some photos of early kit helicopters that
appear to have just a tilting head (no way to auto-rotate
?). Isn't this a bit of a death wish? Does a helicopter
need to have collective pitch for anything other than
auto-rotaion?


Helicopters depend on collective pitch for control of power -
they have no other way to fly. Without collective pitch, you
can't get off the ground, or change power, or get back on the
ground in one piece.

--
Regards,

Stan
  #5  
Old July 22nd 03, 03:02 AM
Guy Alcala
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Stan Gosnell wrote:

"Phillip" wrote in
:

Also, I've seen some photos of early kit helicopters that
appear to have just a tilting head (no way to auto-rotate
?). Isn't this a bit of a death wish? Does a helicopter
need to have collective pitch for anything other than
auto-rotaion?


Helicopters depend on collective pitch for control of power -
they have no other way to fly. Without collective pitch, you
can't get off the ground, or change power, or get back on the
ground in one piece.


IIRC, at least the first Piasecki helo and maybe the first Hiller
lacked collective pitch. Lift was controlled by the throttle
(which controlled the engine and thus rotor rpm), and they seemed
to have flown just fine. There are clearly advantages to the
collective system as later models all included it, but it's not
as if a helo has to have one to fly.

Guy

  #6  
Old July 22nd 03, 03:55 AM
Phillip
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Default


"Guy Alcala" wrote in message
. ..
Stan Gosnell wrote:

"Phillip" wrote in
:

Also, I've seen some photos of early kit helicopters that
appear to have just a tilting head (no way to auto-rotate
?). Isn't this a bit of a death wish? Does a helicopter
need to have collective pitch for anything other than
auto-rotaion?


Helicopters depend on collective pitch for control of power -
they have no other way to fly. Without collective pitch, you
can't get off the ground, or change power, or get back on the
ground in one piece.


IIRC, at least the first Piasecki helo and maybe the first Hiller
lacked collective pitch. Lift was controlled by the throttle
(which controlled the engine and thus rotor rpm), and they seemed
to have flown just fine. There are clearly advantages to the
collective system as later models all included it, but it's not
as if a helo has to have one to fly.

Guy


I guess what I wondered was , other than a need to auto-rotate, a tilt
system would work on a helicopter the same as a gyro? Yes I know
auto-rotation is needed...I'm just wounding if the concept is the same.

That's what these kits mentioned (it's been a long time), you added power
to go up, remove power to come down...seems simple enough. Don't think I'd
like the idea of no collective control for auto-rotation.


  #7  
Old July 22nd 03, 04:09 AM
Phil Miller
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Default

On Tue, 22 Jul 2003 10:43:27 +1000, Phil Miller
wrote:

On Mon, 21 Jul 2003 01:21:13 -0700, "Phillip" wrote:

Would a gyro with a swashplate ( just for pitch control) fly any different
(better,worse) than using a tilt type rotor head? Just more complex?


Just more complex. The net effect would be the same. Increase the angle
of attack 90 degrees before desired disc upward movement, decrease AoA
90 degrees before. Gyroscopic precession then makes the desire movement

^^^^^^
happen.


Woops. After.

Also, I've seen some photos of early kit helicopters that appear to have
just a tilting head (no way to auto-rotate ?). Isn't this a bit of a death
wish? Does a helicopter need to have collective pitch for anything other
than auto-rotaion?


Helicopter collective increase/decreases pitch angle of all blades
collectively and thereby increases/decreases lift. Pull collective up,
go up. lower collective, go down. It's a bit more complex than that, but
I'll leave that to the experts here.

Silly questions, but it's a late night.



Phil



Phil
--
"Me fail english? That's unpossible!"
Ralph Wiggum
  #8  
Old July 22nd 03, 11:07 PM
Paul Baechler
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Default

In article ,
"Phillip" wrote:

"Rhodesst" wrote in message
...
Power adjustments. Wally


Power adjustments? I don't see the difference a swashplate over a tilt

head
for cyclic control would make to a gyros rotor system. Care to explain
further?

OTOH, I think that sport gyros today use the tilt rotor hub because it's a

very
simple design, and it works very well. No swashplate and associated

linkages,
not to mention the fact that there's no need for individual feathering

hinges
on the rotor blades themselves. Much less to go wrong and/or maintain.

JMO,
Fly Safe,
Steve R.


The K.I.S.S. formula at it's best.

So why not on a helicopter? (Like those old kits I mentioned). I'm assuming
because you'd lose auto-rotation?


The basic principle of autogyro flight is auto-rotation. What you'd lose
is a simple, practical way of controlling powered flight.

--
Paul Baechler


  #9  
Old July 23rd 03, 07:41 AM
Phillip
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Posts: n/a
Default


"Bart" wrote in message
...
Phillip wrote:


I guess what I wondered was , other than a need to auto-rotate, a tilt
system would work on a helicopter the same as a gyro? Yes I know
auto-rotation is needed...I'm just wounding if the concept is the same.



That's what these kits mentioned (it's been a long time), you added

power
to go up, remove power to come down...seems simple enough. Don't think

I'd
like the idea of no collective control for auto-rotation.


No, a helicopter can not operate without a swashplate. Without the

swashplate
you'd just be able to go up and down. I'll probably draw some heat here

for
this,
but autogyros have more in common with airplanes than they do helicopters.
The aerodynamics are really different.

In horizontal flight, a helicopter is constantly changing the pitch of
each main rotor blade independently as it travels around in the circuit.
The advancing blade has negative relative pitch, and the retreating blade
has hugely positive relative pitch. Horizontal thrust is not derived by
tilting the mast.

The swashplate is controlled by the cyclic and collective together. The

two
flight controls are "mixed together" to move the swashplate. The

collective
moves the pitch of all blades equally, the cyclic tilts the swashplate to
cause the pitch changes to be become "cyclical".


Bart


I see those brothers (Nolan ?? ) built a coaxial with no swash plate....but
also no auto-rotation. twin engine though. How do they get away with it? I
guess the twin rotors would cancel all those bad things out.

This is one of the kits I saw.

http://www.airscooter.com

No swashplates, no collective, NO AUTOROTATION (scary) two engines I think.






  #10  
Old July 25th 03, 01:22 PM
Phil Miller
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Default

On Fri, 25 Jul 2003 11:57:53 GMT, Terry Spragg
wrote:

For the simplest possible reason:

An auto gyro is always flown in autorotation, with fixed plade
pitch set for 'gliding'. If you apply torque to an auto rotor,
you do not get lift, you get propelled groundward.


G'day Terry,

Are you saying that autogyro's have negative pitch on their rotor
blades? If so, you are wrong.

If that's not what your saying, I apologise. I have misunderstood your
meaning. Could you please explain this statement?

Cheers,


Phil
--
Pfft...english! Who needs that? I'm never going to England.
Homer J. Simpson
 




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