Papin & Rouilly's "Gyropters" (and other monocopters)

From the Postwar topic: http://www.secretprojects.co.uk/forum/index.php/topic,2693.msg21687.html#msg21687

Jemiba said:

They are Gyropteres, not helicopters, as explicitly is said, although I think, this designation was used for several different types of rotary wing aircraft.
As inventors Louis Breguet, Marcel Vullierme (working from 1927 to 1967 for Breguet) and Maurice Chartier are mentioned.

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Ah, but what about Papin & Rouilly's improbable 1914 machine?
In your post, the term "gyroptère" (gyropter, I suppose, in English) sounds more like a marketing ploy here than the depiction of a distinct technology.
But when Messrs. Papin & Rouilly designed and built their first gyropter, the "Chrysalide", it was... something else!

Check these pics which I gathered from an excellent article published in Air Magazine 30 (a publication which I warmly recommend):

Post-WWI developments were even considered, some more of the helicopter kind... The last of these was the 1933 Model D for observation.

Thanks for those pictures, especially for the patent drawings. What I still didn't get, is the way
the pilots tub should have been decoupled from the turning machine. That vain shown, to my opinion
could only be helpful during forward flight and probably would have needed considerable speed over
ground, I think. Ther are a kind of rollers shown in the drawings, perhaps they were used to couner
rotate the cockpit ?

For more technical details (in English), check the Wikipedia page:
http://en.wikipedia.org/wiki/Monocopter

and the U.S. patent for the machine:
http://www.google.com/patents?id=Ba5mAAAAEBAJ&dq=1,133,660

A while back, I did my best to do a write up on the Papin-Rouilly Gyroptere. As near as I can tell, the four rollers were spaced evenly around the pilot's nacelle. The only thing I can think they would be for was to help center and stabilize the nacelle. It is not quite the configuration from the patent, but the machine was fairly different overall.

Here is my attempt:
http://oldmachinepress.wordpress.com/2012/09/06/papin-rouilly-gyroptere-gyropter/

And I always get a chuckle out of this collage. That is a brave "pilot."

Fantastic page and documents, William. Can't believe this one escaped me before!

Are you the person behind the Old Machine Press site, or just a contributor?

Anyway, thank you so much for this great contribution.

Thanks for the link, Bill !
Interesting inside into this project and my question is answered, too !
Would be interesting to know, if the Gyropter would have fown with the
originally envisaged 100 hp engine. But as it is said to have been out of
balance, it certainly would have needed modification. And trying to take off
from the water probably didn't help, I think. A flat and hard surface may have
been better.

Being no engineer, my opinion may be completely inappropriate, but I'm under the impression that the centrifugal force generated by such a large blade rotating would unbalance the machine unless it rested upon a much wider structure.

Also, if the inspiration was the sycamore or maple leaves, dropping it from an aircraft while in flight might have been a solution (along with a good ejection system for the pilot I guess!!).

A question to close: could the Gyropter be considered, in a way, as a long-distant ancestor to the ill-fated Sikorsky XV-2?

Stargazer2006 said:

A question to close: could the Gyropter be considered, in a way, as a long-distant ancestor to the ill-fated Sikorsky XV-2?

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It probably was the first attempt to realise a single blade rotor craft, so I would say "yes"
If carefully balanced, such an aircraft should be possible, I think. For me it's just hard to see
the reason, why the pilot was seated inside that machine and not just under it. More ground clearance
and a much simpler layout, I think.

Hello Stargazer and Jemiba,

Yes, I am Old Machine Press and thank you for the kind words.

I don't mean to take anything away from the efforts of Papin or Rouilly, but I agree that it is doubtful the craft would have flown even with 100 hp. I see a challenge to get it in the air and then a greater challenge to make it controllable with the intended pilot position and controls.

Thanks,

WJPearce said:

I don't mean to take anything away from the efforts of Papin or Rouilly, but I agree that it is doubtful the craft would have flown even with 100 hp. I see a challenge to get it in the air and then a greater challenge to make it controllable with the intended pilot position and controls.

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Heck, yeah, but aren't we so glad and grateful to all these wacky fellas for so much as trying? Sure am!

To make a single bladed rotor work principall should be no problem, I think. With its tip jet drive, for
decoupling the pilots seat from the dynamic structure that vane, containing a kind of puffer jet may have
been enough to overcome friction in the bearings. But how control in flight could be achieved, I cannot see,
too. Probably just by adding a thrust component in the wanted direction via the vane.

Nowadays. it's [relatively] simple to get a monocopter to be stable controllable. One needs an FCS that knows things like desired heading, rate of rotation and location of the blade around its disk etc.

The FCS controlls both the main lift motor and a trim tab driven by a VERY fast acting actuator. This trim tab would be typically located on the trailing edge of the blade. Remember though, control inputs are out of phase with rotation and the response time of the system must also be factored in.

The point that still isn't clear to me is why go to so much pains to create a monocopter when a helicopter is easier to develop, build and fly? When retractoplanes were all the rage, a single blade had its value... but these concepts came and went in the 1960s. The weight factor may have been important, but with the progress in carbon construction, you can have very lightweight blades that sort of kill the interest of the single-blade. Or am I missing something here?

Maybe we're venturing a little 'off-topic' here but the question has been asked so...

Monocopters are a bit of a niche area. In my opinion they only have relevance to the UAS field (and then it's debatable...) because it's possible to build a physically VERY simple airframe (couple of mouldings, motor and actuator) that's capable of CONOPS like 'perch and stare'. Drawbacks include having to tie the frame rate of the camera to the rotation of the platform (UAS like the 'Samurai' prototype platform don't have a non rotating centre pod in the manner of the originally posted 'Gyropter').

Here are several man carrying monocopters from a book on Russian experimental helicopters: http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?num=1311180699/all

A video about the development of sophisticated monocopters:


http://www.youtube.com/watch?v=sbuGCgc-JCM

Scratchbuilt model: http://modelbox.free.fr/analyses/MS2002_10P/SCRH_Papin/index.html

Those bracing wires tell us that the inventor did not understand how centrifugal force stiffens rotor blades.

Dear Stragazer,
If helicopters are so simply to build, why did production helicopters have to wait until the final days of World War 2? … 40 years after the Wright Brothers proved that manned, powered flight was possible.
Granted they needed to learn how to build strong engines and light-weight airframes.

Helicopter rotor dynamics and aerodynamics are an extremely complex subject with dozens of overlapping variables.

Mono-copters are an attempt to reduce the number of variables. The fewer the number of variables, the simpler the development process. Mon-copters have only a single vibration per rotation, but that single vibration has a massive amplitude! With proper balance, most of that huge amplitude is limited to the vertical axis (Z axis on a 3D printer). The simplest way to balance a mono-copter is to hang a counter-weight (e.g. engine) opposite the single blade. If the cockpit is directly on the vertical axis, the pilot experiences the least vibration.

If helicopters are so easy to build, then why do so many only have 2 main rotor blades: Bell, Hiller, Robinson, etc.?
Let me answer my own question: 2 blades are the least expensive way to build helicopters (semi-articulated). Two-bladed rotors do not need lead-lag hinges because when the advancing blade is trying to lift and lag, the retreating blade is trying to lose lift and accelerate to compensate. By compensate, I mean equal lift on both sides of the rotor disc. They only need a single bearing for flapping. Two-bladed rotors have twice as many vibrations per rotation, but the amplitude is halved. That is why smaller Bell helicopters make such a distinctive wop-wop-wop sound.

When you start building with 3 or more blades, you need to add lead-lag hinges (fully articulated). Three-bladed rotors make 3 vibrations per rotation, but each vibration has a smaller amplitude. Granted that gives a smoother ride and smaller amplitude vibrations means that parts fatigue at slower rates.
Larger helicopters add more blades to improve rotor disc density to improve lift without needing to increase diameter. The latest version of Sikorsky's CH-53 Sea Stallion has something like 9 main rotor blades!
The Sikorsky Ch-124A Sea King helicopters that I worked on had 5 main rotor blades and 5 tail rotor blades. Each blade had 4 distinct hinges per blade: pitch, lead-lag, flap and fold to stuff inside a small hangar onboard our ship (HMCS Athabaskan or HMCS Iroquois). That quickly added up to 24 ball bearings per main rotor … before you consider swash-plates or control linkages! More blades require more moving parts and more maintenance. It seemed like I was elbow-deep in grease every day! When I was not greasing or cleaning or inspecting blades, there was always some other component to inspect.

Another write-up of the Papin & Rouilly Gyroptère and (some?) subsequent projects:
Jean-Christope Carbonel; "Messieurs Papin & Rouilly's Astonishing Whirling Leaf", The Aviation Historian, No. 27, April 2019, pp. 62-72. It carries some interesting notes about the use of a steering jet and the pilot's experience while running the machine up on water.

It notes another intriguing reference:
"Will this 'Whirling Leaf' Flying Machine Solve Greatest Problem in Aviation?", Popular Science Monthly, September 1922.

Although cold tipjets have been successfully used since (on a French production design whose name shamefully escapes my memory), I have to express my doubts about the monocopter as a practical design. The flight dynamics do not seem to have been thought through.

The most obvious issue is that the centre of lift does not align with the centre of gravity. For reasons of mechanical balance, the rotor will spin about its centre of gravity and the gondola is located at that position. But the centre of lift is fairly well outboard and will rotate with the blade, cutting a circular path (or, in forward motion, a cycloid path). Centrifugal force on the rotor can only partially compensate for this. The axis of rotation will not stay vertical but will tip at an angle which follows the blade round. The only way to avoid a gyrating gondola would be to mount it freely on a universal joint or similar, and give it pendulum stability by hanging it below the rotor bearing; but there is then the problem of connecting up effective controls.

Another problem is that of varying angle of attack through rotation speed or variable-pitch control. On a normal helicopter, the accompanying aerodynamic force changes cancel out. But on the monocopter they do not. Any change in angle of attack must be accompanied by a reaction twisting the engine and gondola mounting the other way. It will also create a resultant force on the rotor axis, at right angles to that induced by off-centre lift. This force will also spin round with the blade. The only palliative would again be pendulum stability, but this time independent of that provided for the gondola.

More subtle is the matter of force distribution under varying flight conditions. Some forces acting on the rotor are linear with span and velocity, others obey a square law for one or the other, while lift and induced drag obey a fourth-power law with speed. The moments generated, about the central axis of the gondola, will exactly balance only in a very specific range of flight conditions. At all other times there will be some imbalance and the axis of rotation will move away from that of the gondola, which will therefore gyrate off-axis. The only palliative would be some kind of variable-centre bearing or pivot, a complex piece of engineering at best.

There are therefore real dangers of the thing tipping beyond recovery in a sudden manoeuvre, or of gyrating itself to bits.

Also, any gyrating or tipping circular motions which get through to the gondola (probably all of them, to simplify the engineering), will be felt by the pilot as a repetitive wavelike effect at around 1 or 2 cycles per second, with such motions variable but unrelenting throughout most of the flight. Airsickness must be a constant risk. Paranoia? Well, the British Army's observation balloons used during the Boer War could not be deployed in winds much over 10-15 mph, as their wind-blown motions rendered the observer too airsick for duty. On the other hand, most sailors get used to such semi-regular motions of their ships and boats. The gondola motions of the monocopter must be kept strictly limited, and even so it must be for the harder-stomached airman only. An airsick pilot would have to put down immediately to avoid losing their ability to control the machine.

Rough-weather flying would almost certainly be unsafe, for reasons of both stability and airsickness.

All of which which would rather limit its usefulness, even if it did stay the right way up.

Modern digital systems and some clever engineering could probably fix these problems. And it is true that there is theoretically a marginal efficiency gain, in flying a single blade free from the wake of a second blade. But, given the inherent extra-large rotor disc and the weight and cost of the extra engineering, that would hardly seem to compensate. Something like a quadcopter employing mono-blade rotors would avoid many of the problems (at the expense of increased structural loads), but almost certainly the compactness of a multi-blade design would win the day.

Dear Skyraider3D,
Beautiful model!
Has anyone offered a scale model kit?

Dear steel pillow,
We wonder how much cold tip jets suffer from internal drag through the long duct. How much thrust is lost in internal skin friction?

I vaguely remember a photo of a Sikorsky R-4 fitted with a single-blade main rotor. It was an attempt by Igor Sikorsky to understand blade dynamics. I doubt if it got beyond ground runs.

riggerrob said:

Dear steel pillow,
We wonder how much cold tip jets suffer from internal drag through the long duct. How much thrust is lost in internal skin friction?

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It depends on the duct of course, but probably somewhere between 20-30% will be lost. On the other hand if the engine drives the rotor shaft through a gearbox, that and the added tail rotor will incur roughly similar losses. So the Sud-Ouest Djinn (I remember it now!) was not significantly less efficient.

steelpillow said:

" ... Also, any gyrating or tipping circular motions which get through to the gondola (probably all of them, to simplify the engineering), will be felt by the pilot as a repetitive wavelike effect at around 1 or 2 cycles per second, with such motions variable but unrelenting throughout most of the flight. Airsickness must be a constant risk. Paranoia? Well, the British Army's observation balloons used during the Boer War could not be deployed in winds much over 10-15 mph, as their wind-blown motions rendered the observer too airsick for duty. ..."

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We now understand why spherical balloons are so unstable in any wind. Basically, one side of the balloon starts to develop lift, until its angle of attack gets too steep, then it stalls and the other side starts to lift. Rinse and repeat.
During World War 1, WALLIES solved that problem with tear-drop shaped Percival balloons, while Germany adopted sausage-shaped Draken observation balloons. Both types had suspension lines that held them permanently at a positive angle of attack, adding lift.

Drag chutes and drogues have also taught us about stability of circular canopies.
The ballutes add stabilizing vents to ensure that the canopy stalls uniformly around its equator. During a seminar at a Parachute Industry Association Symposium, designer Bill Gargano said: "... and then we added a thin vent all around the equator." With airflow stalled equally around the equator, it quit oscillating.
I suspect that ballutes were developed in Nazi Germany or it may have been in the USSR during the Cold War. Soviets certainly used plenty of drogues in their ejection seats and an overly-complex static-line parachute system.
Fast forward to the 1980s when Bill Booth and Ted Strong developed tandem jumping for civilian skydiving students. Both suffered too many torn main canopies because they were deploying at 180 or 200 miles per hour, considerably faster than the 120 mph. common to solo skydivers. At the same time, Strong Enterprises was sewing Russian-pattern drogues for Alaska smoke-jumpers, so Ted Strong added a drogue to his tandem system to slow deployment speed to 100 or 120 mph. Suddenly the number of torn main parachutes reduced dramatically. Bill Booth added drogues to his Vector tandem system a few months later. All other tandem manufacturers soon added drogues to their tandems.
Drogues may double the number of handles, but they do help with freefall stability and dramatically reduce opening shock. A side effect is that they slowed tandem pairs to speeds that solo outside video-graphers could follow. Suddenly, selling photos to first tandem students became a new source of revenue and the skydiving business boomed during the 1990s.

I have done a handful of drogue-less tandems and was impressed by the speed and hard openings. Since then I have done more than 4,000 tandem jumps with drogues. I have also patched dozens of tandem drogues.

Given a mono-copter's dynamics, could you describe motion as 'Sicamore' ??

( Sorry, been a strange day... )

riggerrob said:

I vaguely remember a photo of a Sikorsky R-4 fitted with a single-blade main rotor. It was an attempt by Igor Sikorsky to understand blade dynamics. I doubt if it got beyond ground runs.

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It hovered, at least (go to 10m16s):
View: https://youtu.be/5VOttDBZDWI?si=JHMfwXewolv__urK&t=616