A Case for an Electric Gyroplane Seaplane

[Hodag]

A two blade rotor has great advantages at a floating dock, or pulling alongside a boat.

 

[WaspAir]

Would you say that the fuel burn rate of a helicopter is more, less or the same as a gyroplane after 45 minutes of flight, including one takeoff and landing? An Autogyro Calidus seems more aerodynamic than a side by side... anything.

The drag from a gyro fuselage is actually a very small component of total drag when compared to the drag from the rotor system, so the side-by-side vs. tandem comparison isn't meaningful unless you're comparing one gyro to another. Even then, my side-by-side J-2 was faster on the same horsepower than my tandem A&S18A.

I know from direct experience that a (comparable) helicopter will fly faster for the same fuel burn when compared to a gyro. The inefficiency in using an air coupling with high losses to turn the rotor when compared to direct drive through a metal shaft is enough to account for that difference regardless of fuselage shape, and also enough to overcome power consumed by the tail rotor (it's actually not too bad in cruise flight, when you can get some fin effectiveness with forward airspeed and don't need much anti-torque power).

I also feel that tandem seating- not generally found in civilian helicopters but is not out of the question, I suppose- is not only better for visibilty- allowing both occupants to see on both sides at all times, but better hydrodynamically for a seaplane- and the same would hold true for two-place tandems over single-place gyroplanes, although anything is scalable.

Having spent plenty of time instructing from the back seat of tandem aircraft, I disagree on the visibility question. The fellow in front will restrict vision in a direction that is very important. Side-by-side with a big bubble works very, very well for both occupants.

 

[WaspAir]

If we take "truly comparable" to mean equal payload and cruise speed and design the gyro to have a tip speed as low as the old tractors (150 rrpm) with the best profile we can muster (perhaps an ONERA OA212) and a very large tractor propeller for the job would that still be true? (just asking without even a back of the envelope calculation..;-)

My intuition, without the time to do careful computation, says yes, because fluid coupling through unconstrained air is woefully inefficient. We also need to be clear about "equal speed"; I think you'll get more speed out of the same power, but I suppose it could be looked at as lower burn rate at the same speed, so long as that speed is achievable by both.

 

[Jean Claude]

My head creates tremendous drag and lifts my CG horribly, but sometimes it is useful.

I do not want to be insulting, Hodag. My comparison with the drag of the pilot head is true.

 

[Jean Claude]

The drag from a gyro fuselage is actually a very small component of total drag when compared to the drag from the rotor system.

Yes, at 47 mph, rotor drag of the Magni M16 is 5 times that of its fuselage.
But when forward speed increases, then rotor drag decreases while fuselage drag increases.
So, at cruise 80 mph, the fuselage drag is equal to the rotor.

 

[Hodag]

WaspAir,
Thanks for the response.
Speed would not actually be very high on my priority list. Operating costs and noise would be. Does a Kompress have lower operating costs than a Cavalon? It's probably too soon to know. To add drive shafts and gears would add noise and I would lose the wonderful benefits of the low-RPM system. Tail rotors are dangerous, and I don't think Boeing would let me borrow the NOTAR system. Gyroplanes can water taxi using less energy if they only have to move 100 feet. I assumed the back seat would mostly be staring at the FLIR monitor, but I retract my statement about visibility. There are many other reasons for me to choose tandem seating in a gyroplane though, as I mentioned.

Jean-Claude,
No offense taken, I just have a large head.
That is interesting data on the M-16, thank you. Does it feel like it wants to climb until it hits 80 MPH?

 

[Hodag]

At what airspeed does a rotor start to turn without prerotation?

Could someone discuss flapping during taxiing, especially over rough terrain?

 

[kolibri282]

Jean-Claude's result seems to be consistent with my calculations. Comparison is between a UH-1 and a gyro having the same gross weight and flat plate area both flying at 100 knots. At an rrpm of 147 the power to drive the gyro is 457hp, for the helicopter it is 944. Both use profile data for a naca0012. I have attached the input and output files so you can check what I did if you are interested.
It turns out my engine model is fairly susceptible to prop diameter. Previous results were calculated using an 8ft prop (think of a Westland Wapiti) with a 6ft prop power is 946hp. I am using a slightly modified version of the late Martin Hollman's engine model, which I use out of the box, without any verification so far

 

[kolibri282]

At what airspeed does a rotor start to turn without prerotation?

Never, unless your sink speed is high enough and your collective is right (see below)
(Ok, nobody has tested it at mach 3 so far)

https://dspace.mit.edu/handle/1721.1/32456

 

[Hodag]

kolibri282,
Thanks for the data, but it is beyond me. What is the significance of 147 rrpm?
My questions were pertaining to gyroplanes on take-off, I should have been explicit.

 

[kolibri282]

My questions were pertaining to gyroplanes on take-off

My answer was pertaining to gyroplanes on take-off, it's the "never" part.

rrpm means "rotor revolutions per minute"

From what I have learned about the development of rotary wing aircraft I am convinced that you might copy existing designs if you are a blessed mechanic (see the story of Robert Stierlin) but if you want to create something new you need a very thorough engineering background which the likes of Cierva, Young or Bensen had. So the first step to creating something new, in my opinion, would be to become an aerospace engineer.

 

[Jean Claude]

At what airspeed does a rotor start to turn without prerotation?

Theoretically, just air speed not faster than 0.35 time the speed of blades to tip, because the retreating blade stalls
So, launch at 60 rpm do not allow never more than 17 knots of airspeed
And 0 rpm, never more than 0 kt

Could someone discuss flapping during taxiing, especially over rough terrain.

Rough terrain makes jump the blades and much disturb the angles of attack to low rpm. If too, then the autorotation torque can disappear.

 

[kolibri282]

Theoretically, just air speed not faster than 0.35 time the speed of blades to tip, because the retreating blade stalls
So, launch at 60 rpm do not allow never more than 17 knots of airspeed
And 0 rpm, never more than 0 kt

The answer is pretty garbled, could you please post the french version?
(La réponse est un peu incomprehensible)
Also my answer was based on the fact that you have friction in your system.

 

[Vance]

At what airspeed does a rotor start to turn without prerotation?

Could someone discuss flapping during taxiing, especially over rough terrain?

It is my observation that depending on the airfoil many gyroplane rotors will hand start, probably at less than ten rotor rpm and continue to spin with very little wind. The gyroplane I fly will fly level at 20kts indicated air speed and the rotor continues to spin at zero forward speed.


People seem to have a lot of different definitions for blade flap.

One is what allows the rotor blades to compensate for dissymmetry of lift by adjusting their angle of attack with a teeter hinge.

Another is when the airfoil of the rotor blade exceeds the critical angle of attack and stalls.

If I taxi too fast with the rotor spinning too slowly and the disk tilted too far back it is possible to exceed the critical angle of attack. Because the other blade may still be flying the rotor blade has a tendency to diverge from its intended path and strike things in a destructive way.

More rotor rpm, less taxi speed or a flatter disk will prevent these issues.

In my opinion the immediate response to blade flap should be the get the cyclic forward where the angle of attack of the blades is reduced and there is less to hit. It begins with a tapping in the cyclic and soon becomes somewhat violent as it exceeds the available angle of the teeter hinge.

In my experience taxiing over rough ground makes the blades come up to speed more slowly and aggravates any tendency to flap as the bumps are another disturbance to a smooth tip path.

 

[Jean Claude]

The answer is pretty garbled, could you please post the french version?
(La réponse est un peu incomprehensible)
Also my answer was based on the fact that you have friction in your system.

Théoriquement, le régime du rotor peut toujours s'établir à sa valeur stabilisée finale à condition que la vitesse relative à l'air ne dépasse jamais plus que 0,35 fois la vitesse du bout des pales, à cause du décrochage de la pale reculante.
Ainsi, lancé à 60 t/mn, le régime final ne pourra jamais s'établir si la vitesse relative à l'air excède 17 noeuds.
Et pour 0 t/mn, la vitesse relative à l'air ne devra jamais excéder...0 noeud.

Rouler sur un terrain bosselé fait tressauter les pales et perturbe beaucoup les angles d'attaque des profils quand la vitesse de rotation est lente. Si les perturbations sont trop grandes, le couple auto-rotatif peut disparaitre.

PS: Je suppose négligeable la friction des roulements à billes

Merci pour votre traduction

 

[Hodag]

kolibri282,
Having some communication difficulties, sorry if I am not an engineer,
Before the days of the prerotation, gyroplanes had the ability to take off. They could take off as gliders before they used engines. I was just trying to get an idea of how much energy could be recaptured from the rotor while taxiing without the desire to take off, and also, would that even be desirable, since flapping could be destructive below 100 rrpm? Maybe I am answering myself.

I understand rrpm. Why 147 of them in your analysis?

 

[Hodag]

Vance,

Thanks! That was my biggest concern with this concept

 

[Vance]

There are people flying gyroplanes on floats now David and there don’t appear to be any particular rotor issues.

There is at least one on this forum out of Florida and he loves it.

There is another down in Mexico but I don’t think he is on the Rotary Wing Forum.

 

[kolibri282]

Before the days of the prerotation, gyroplanes had the ability to take off

That was presumably before the Big Bang, any gyro afterwards took off with the blades spinning, early pioneers like Bensen, Brock or Wallis used plain brawn for it.

 

[Hodag]

Vance,

Thanks for the reply,
I know Sweden certified the Full Lotus floats in some way as well.

I think it might be safer though to go with a flying V-mono boat hull with hydrofoils to smooth out the ride. Here is an example of a hydrofoil that "takes off" at 4 to 6 kts, reducing water drag 75%, and max speed of about 22 kts on an outboard with 3.7 kw max power. (https://www.youtube.com/watch?v=ooAAnZIgj8o) Obviously the foil shape would be completely different on a different vehicle. 7 m turning radius, 10 cm draft with foils up, 1 m down until takeoff speed reached, 260 kg empty weight. Slovenia again, like Pipistrel.