Optimization of Autogyro for Preliminary Development of Personal Flying Vehicle

Jean Claude

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About 500 h (FW + ultra light)
The many errors take away all credibility from this author. Few examples:


Many mistakes also concerning the RAF 2000 autogire
In Table 2 he writes:
Gross Weight 1540 lbs
Minimum Speed 10-12 MPH
Maximum Speed 140 MPH
Rate of Climb 1750 ft per minute
 

eddie

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They also have the 0-360 at 131 hp ,should be 180 hp.
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
Yes Eddie.
Here, a true curve of C[SUB]L[/SUB]
Sans titre.png
 

Vance

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It reads like a snake oil salesman wrote it.
 

twistair

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"Let them alone; they are blind guides"(c) Mattew
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
Sorry, Better readable now:

Sans titre.png
 

HiFlite

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I'm not convinced that modern gyros are slower than comparable helicopters given comparable power. Here's a comparison between the two-seat R-22 and Schweizer 300. Both use Lycoming -360 engines of nominally 180 hp. While the R-22 install is de-rated to 135 hp, if it's like other de-rated engine installs, that means it can run at 135 hp all the time. 75% of 180 hp is 135 hp, so the cruise speeds are from the same power output: 110 mph for the R-22 and 90 mph for the Schweizer, at *10* GALLONS PER HOUR. Eurogyros are right there with them in speed but using a much lower horsepower and fuel burn. While the maximum speed for helicopters in general are far greater than present gyroplanes, going back (or forward) with articulating blades instead of simple teeter systems would reduce or eliminate that gap.
 

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Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
Why do you think that articulated blades like a helicopter would reduce the gap?
 

HiFlite

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Perhaps my newbie-ness is showing and I'm using the wrong words, but reducing the pitch of the advancing blade and increasing the pitch of the retreating one helps negate the rolling tendency with higher airspeed. AFAIK, teetering alone only works with 2-blade rotors which is one reason the 4-blade ur-gyro came with a full-Monte system in the 1920's. Yes, of course, it would make gyros more expensive, but faster and (potentially) more efficient as well. A limited-range cyclic should also allow tuning the rotor rpm in flight, allowing one to run in a smooth operating range and partially compensate for high density altitude operations without swapping blades for longer ones. But, I'm far from being an expert on RW dynamics, so YMMV.
 

Vance

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In my opinion it is not the rotor system that is limiting the top speed of gyroplanes.

The VNE of a AH-1G Huey Cobra is 190 knots (218 miles per hour) and the maximum speed in level flight is 149 knots (171 miles per hour). It has a two blade teeter rotor.

I suspect the words you were looking for Tim are limited “collective” to adjust rotor speed. It is hard for me to imagine a situation where this would be worth the extra complexity.
 

kolibri282

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but reducing the pitch of the advancing blade and increasing the pitch of the retreating one helps negate the rolling tendency with higher airspeed
As with every articulated rotor a teetering system takes care of roll by the fact that no moment is transmitted to the mast due to the teetering bolt, the blades simply flap freely up and down either side the way they feel best for them. The feathering action (reducing blade pitch for the advancing blade and increasing it for the retreating one) is necessary to produce the required forward tilt of the disc that allows you to have a force component of the rotor that balances the drag of the aircraft. Remember that a rotor is a second order system in resonance, where the maximum of the action (blade pitch) must be applied a quarter of a revolution before the desired effect (for and aft blade flapping) is achieved.
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
HiFlite;n1135468 said:
A limited-range cyclic should also allow tuning the rotor rpm in flight, allowing one to run in a smooth operating range and partially compensate for high density altitude operations without swapping blades for longer ones.
As the altitude increases, the Rrpm increases as well as the forward speed (*), and so the angles of attack exactly remain the same as those at the sea level.
Thus, density altitude has no reason to be compensated by a different collective pitch.
(*) Unlike the tachometer, the speedometer does not show the increasing because of its operating principle
 
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XXavier

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kolibri282;n1135599 said:
As with every articulated rotor a teetering system takes care of roll by the fact that no moment is transmitted to the mast due to the teetering bolt, the blades simply flap freely up and down either side the way they feel best for them. The feathering action (reducing blade pitch for the advancing blade and increasing it for the retreating one) is necessary to produce the required forward tilt of the disc that allows you to have a force component of the rotor that balances the drag of the aircraft. Remember that a rotor is a second order system in resonance, where the maximum of the action (blade pitch) must be applied a quarter of a revolution before the desired effect (for and aft blade flapping) is achieved.
Perhaps 'backward tilt of the disk that allows you to have the drag component of the rotor balancing the thrust of the aircraft propeller'... It's a gyro, after all, and not a chopper...
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
Total Flight Time
About 500 h (FW + ultra light)
A sketch may be simpler:

Sans titre.png
 

C. Beaty

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Here’s what Prof. JAJ Bennett says about cyclic pitch and the 90 degree phase shift:

The tilting hub and reflex methods of control are fundamentally Identical because whenever the control lever is moved in any given direction the cyclic variation of the blade incidence is the same in both.
Inertia prevents a sudden displacement of the tip-path plane, so that when hub is tilted the periodic displacement about the flapping hinges gives the same variation of blade angle with respect to the tip-path plane as is obtained about feathering control hinges in the reflex method.
It is wrong to imagine that to tilt the hub the pilot must impose a load on the control column sufficient to displace the blades against their own inertia.
The control mechanism is a relay, in which the moments are relatively small and when the pilot operates this relay he only causes the blades to feather cyclically.
The result is a cyclic variation of lift in phase with the cyclic variation of blade incidence. The cyclic variation of lift displaces blades from their normal path, but owing to the natural frequency of motion about the flapping hinge being equal to the rotor’s angular speed, the displacement of the blade from its normal path occurs 90 deg. later in azimuth, thus effecting the required tilt of the tip-path plane, and therefore the lift vector which is normal to this plane.

Prof. Bennett was chief engineer of the Cierva Company and later, designer of the Fairey Rotordyne. The term "reflex" means cyclic pitch via feathering bearings.
 

kolibri282

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XXavier said:
Perhaps 'backward tilt of the disk that allows you to have the drag component of the rotor balancing the thrust of the aircraft propeller'... It's a gyro, after all, and not a chopper
Perhaps I have centered a bit too much on the comparison with light helicopters
Here's a comparison between the two-seat R-22 and Schweizer 300.
Thanks for your input Xavier, it was great to meet you!
J'ai de si grands memmoires du Bois de la Pierre...;-)
 

kolibri282

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but owing to the natural frequency of motion about the flapping hinge being equal to the rotor’s angular speed
This phrase is equivalent to Prouty's statement that a rotor is a second order system in resonance and it is the reason for the 90° phase shift between input and response. The picture shows the control linkage from cyclic to swash plate. In this case the cyclic stick actually moves the swash plate for and aft but the pitch horns go one quarter around the mast so that the blade feathering takes place when the blade is at right angles with the aircraft, which ultimately causes the for and aft disk tilt.
(from here: https://www.researchgate.net/figure/Schematic-of-collective-and-cyclic-control-system-of-helicopter_fig3_322887374) Schematic-of-collective-and-cyclic-control-system-of-helicopter.ppm.png





A good description can be found on page 7-4 here:

http://navybmr.com/study%20material/...14008A_ch7.pdf


As an engineer I found I hard to live with the sloppy drawing above, so I tried to improve it a bit:


Collective-and-Cyclic-Control-System-of-Helicopter.png
 
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C. Beaty

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Pitch/flap coupling, wherein an upflapping blade is depitched, in effect imposes an aerodynamic spring that resists flapping and raises the flap resonant frequency.
The R-22 has a small amount, reducing the phase shift to ~80º.
The A&S-18A has considerably more, being the means whereby collective pitch is automatically reduced following a jump which reduces the phase angle to ~70º.
 
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