A Breakthrough Rotorcraft Technology

wicked graphics...

I would have at least some secondary stabilizers on it... While rotor inertial differential control is necessary, I think it is not as precise as you are hoping. Also without some tail wing to lift the tail, the vehicle will not fly truly horizontal.. in my somewhat limited understanding of the forces involved.

but generally... it gets a 8/10 from me... would be awesome to watch take off and land for real, at the airport... even more exciting than choppers.

Chris

I don't mind your skepticism. One can easily ask why, if this simple concept is practical, it hasn't been implemented before.

I didn't mention in my original post that, like a helicopter, the blades in each rotor are controlled in cyclic and collective pitch. A collective pitch increase, of course, simply increases the pitch angles of all the blades in a rotor together. Cyclic pitch is able to increase the pitch of rotor blades in part of their rotation. For example, if cyclic pitch increased the pitch of the rotor blades only when they were in the rear of the craft, the craft would pitch forward.

Well,

I just don't see the utility. And controlling the rotors with servo-motors scares leaves me skeptical. As does sucking in the tips of the rotors at speed. The slightest imbalance and you have catastrophic failure of the aircraft. How would auto-rotation work?

The claim of 400 knots is.............................optomistic? If not the stuff of dreams.

Where is the basket and hoist stowed in flight for "over water" rescues, and where do the extra passengers sit after the rescue?

This is a solution in search of a non-existent problem.

Yes, I have thought about how super-reliable the controls and actuators for the rotor blade pitch angles have to be. If the bearings, the actuators, and the rotor blades are well-designed the craft should be reliable. I think that it is well know now days how to design mechanisms for high reliability.

Sucking in the rotor blade tips would be done to obtain a slight edge in cruising performance. I agree that this must be done, if it is done, in a very precise way to avoid vibration while they are being pulled in.

Lyn,

400 Knots is very possible, but power requirements increase rapidly with speed even in a clean design like this. A speed of 300 Knots would require a lot less power and probably still be very useful.

I am not sold on the necessity of pulling in the rotor blade tips. There is and advantage but it is small. Pulling the rotor blades in at speed reduces the drag a bit.

For a large rescue craft the two pilots would be forward of the forward rotor and the six people being picked up would ride in the center part. The hubs of the rotors would have large annular open spaces inside them. Fixed tubes with ladders in the sides of the tubes would be provided between sections to allow the pilots and passengers to climb up and down. A rope ladder would be let down to the ground.

oh, I thought it was a commuter concept.. (I didnt' read the material.. just watched the video)

What about the turbulence of the air off the fore blades as it strikes the aft blades?

Was that Convair, Corvair, or Cornvair? (Font sometimes matters.)

I have thought about the turbulence seen by the rear rotor blades which is caused by the forward rotor blade.

It seems best to me to have a fast servo-motor control the pitch angle of each rotor blade. This, of course, differs from the wobble plate mechanism used in helicopters. With this approach and a "smart" control system the system can "learn" what disturbance to expect from the wake of each front rotor blade and compensate for it so that each of the rear rotor blades will produce fairly uniform lift and propulsion forces.

CONVAIR (Consolidated Vultee) Model 5 . The upright 'fighter' was named the POGO. "Intended to investigate the potential of a small single set tail sitting VTOL fighter for operation from and to small platforms on a variety of ships. Its development was abandoned as a result of major flight control problems and the realisation of the type of problems the tail sitter aircraft would encounter in carrier operations." Its contemporary the Lockheed - XFY1, was only tested using a temporary 'conventional' undercarriage. Both date from 1954.

Total absence of any stabilising feature other than the 'canceling' between the two rotors doesn't give me much confidence. Not so at hovering time, a bigger and bit slower top rotor can solve that, but when moving at a few Knots. The only lifting force will be the vertical components of thrust and to be there for you they must be absolutely controlled in both intensity and orientation, and having the CG between rotors, at an accuracy level and response speed unheard of. And this along the rotors' torque canceling for the cabin not to spin, plus taking care of external, or top rotor generated air distutbances. Why not prototype as R/C and test? Good luck. S.M.

First, about directional stability. It can be shown that a traditional airplane is directionally stable and that a helicopter is directionally unstable. In the same way it can be shown that a tiltplane has a neutral directional stability characteristic. But in a sense those are historic considerations; modern control systems together with angular rate sensors can easily make almost any controllable craft directionally stable, or at least manageable.

I have wondered to myself if the center of gravity has to be exactly between the two rotors. When cruising, if the CG is slightly aft of the midpoint between the two rotors, then more torque will be needed to drive the rear rotor than the forward rotor. How can the forward rotor then match the torque of the rear rotor without producing unwanted lift or thrust? Its rotor blades can do this by producing counteracting torque at the top and bottom of the rotors rotation.

I am recently retired and without a budget big enough to undertake big projects. But a professor at a major technical university is planning to seek government funds to do wind tunnel testing. As a result of that funding I expect that I will be building the test models.

For the CG position not to be that critical i.e be able to control each rotor's thrust, while torques balance, I imagine the rotors should not be totaly synchronized. Except their pitch scheme on a revolution, you must be able to vary their speed ratio too, or to be able to move at least one rotor's blades radially (to a bigger or smaller cycle). S.M.

I have not run any numbers on this, but I believe that the weight balance will be able to have some range. I hope that it will turn out that the percentage of the total weight carried by the two rotors in horizontal flight can range at least from 40-60 to 60-40.

It would be good if the rotors can be run at a constant speed. This is largely because I expect that larger craft will be gas-turbine-powered and gas-turbines have a very limited full load speed range.

It should be possible to match the torques delivered by the two rotors even if the weights carried by the two rotors are different. The rotor blades on the rotor needing to produce more torque can apply that torque to the airstream when the rotor blades are near vertical; this would not affect the rotor's load carrying ability.

I'm still struggling with the apparent lack of lift. I see rearward thrust, but where's the lift? _{Not to be confused with "where's the beef".}

Consider a bullet fired from a gun. It begins to fall the instant it leaves the barrel even though it may be traveling at 4,000FPS.

It looks like the thing will be flying tail down, always.

It's supposed to always travel at an angle if I understand the concept.. Never totally horizontal. S.M.

If the rotor blades had fixed pitch, then I agree that the craft would need to fly nose high in order to get lift from the rotor blades. But the rotor blades are independently controlled. When the craft is flying horizontally the controls are able to adjust the pitch angle of each rotor blade so it gives the desired amount of lift throughout its rotation.

For example, when flying horizontally the down-going rotor blades in each rotor will need to bite off more air (have a higher local angle of attack) than the up-going rotor blades in order to propel the craft forward. This is because there is a forward-leaning lift component from rotor blades that are moving down and an aft-leaning lift component from the rotor blades that are coming up.

So the pitch angles of the rotor blades can be adjusted during a rotor's rotation so that the craft does not have to fly nose-high to get lift from the rotor blades.

Sorry, I lost you on last post. Say top rotor CW bottom rotor CCW. Top right side and bottom left will give lift? At what pitch? 90 deg and then return to rational pitch for the other 3/4 rev? S.M.

I see thrust, but no lift.

If there is lift, one side, only, will be providing it, fore and aft? If only down-going blades supply lift, how else can it be?

Is there not also some gyroscopic effect with counter rotating bodies that would make this thing spin like a top?

This is giving me a headache.

I think that the main problem here is that one generally thinks of propellers as producing thrust and wings as producing lift. But the tiltplane concept combines the two functions; in level flight the rotors produce both lift and net forward thrust.

Here is a thought experiment that may help. Imagine that the craft has two 4-bladed rotors and that both rotors are stopped with the 8 rotor blades either vertical or horizontal and aligned with the flow. If the craft were to fly with the nose up say 5 degrees, lift would be produced on the horizontal rotor blades, right? Well, the craft can change the pitch angles of individual blades arbitrarily, so the craft can also fly level and give the horizontal rotor blades 5 degrees of up pitch producing lift, right?

Next imagine that the rotors turn slowly. When they are horizontal they can still produce lift on both sides of the craft, right? All one has to do to get forward thrust is to set the angles of attack on the down-going rotor blades to slightly higher values because their lift vectors lean forward. OK?

I noted another comment that mirrors mine. I see lift in the VTOL mode. I see no significant lift in horizontal flight mode.

The Convair design, mentioned in another comment, used a lot of very similar ideas. It also was highly effective at converting power into noise. Landing it was it's ultimate doom. It was next to impossible for the pilot to back the craft down under power to a controlled landing due to visibility issues.

While automation that was not possible at the time of the Convair effort could make it doable, it would be very difficult to convince certifying authorities.

Finally, the engine-out performance would be quite exciting.

I will grant that it is an intriguing concept though.

if the props are driven from a common shaft (and flywheel), with a differential drive for each prop, there is no reason why this is not functional with one engine or two.

I do think there would be a dynamic difference between the convair and this one, due to the separation of the rotors, which would have different effects at the different airspeeds. with the convair design, there would be much more interference of the rotor wash from one rotor to the other, but at high speeds, this one will be similar.

take it slow, be prepared to redesign as the test data shows the way.

chris

Canadair built a VTOL UAV a number of years ago that had a similar arrangement of counter-rotating fans. It hovered nicely and by tilting a bit could also provide some horizontal motion. If I remember correctly, its fuselage was a peanut-shaped thing and it used ducted fans.

The tiltplane -as shown - still lacks a mean of producing significant lift for the horizontal flight mode. VTOL mode is okay, but once it tilts for horizontal flight, the force vectors give a resultant downward force very near that of gravity.

In horizontal flight the rotor blades in the counter-rotating rotors produce both propulsion and lift. I once had a "CEILING WALKER" as shown below. When the rubber-band motor was wound up the craft would fly very fast for about 30 feet until the rubber-band motor had wound down. It flew more or less in a straight line. I say more or less because there were small course changes in flight most likely caused by air currents in the air through which it was flying. In the literature this flight behavior is called neutral directional stability.

Note that if a tiltplane had 8 rotor blades and, for argument purposes, they were imagined as having no twist and being aligned with the craft's axis, then the craft could glide with a 19:1 down slope. That is pretty good performance. If the rotors are given their normal blade shapes, then under power the craft can fly in level flight with good efficiency. A 19:1 Lift/Drag ratio is typical of may "normal" aircraft.

Please see my website: www.tiltplane.com.

I do remember seeing the peanut-shaped craft. You can see a picture of it in Figure 3 of may paper which is at www.tiltplane.com. The craft is the Bombardier CL-327 Guardian. But it did not use ducted fans; it had two counter-rotating rotors much as my craft does, except they are near the center of the craft whereas my rotors are nearer the ends of the craft.

In a tiltplane the rotor blades can change in their pitch angles over a wide range. When the craft is taking off the rotor blades will have very shallow pitch angles, but when it is cruising they will have very steep pitch angles. If one imagined for the sake of illustration that the pitch angles were so large that the rotor blades were aligned with the craft's axis, then they would be like wings. Then it would be obvious that they can produce lift. Of course, they can also produce lift in all the flight modes.

I don't mean to rain on the parade, but tailsitters aren't exactly new to aviation as lyn pictured, and as osborne83 noted the designs abandoned due to the discomfort involved in vertically landing the craft while the pilot was staring at the sky.

http://en.wikipedia.org/wiki/Tailsitter

One issue yet to be discussed would be what kind of autorotation maneuverability the craft would have given an engine failure? I know the V-22 kind of sidesteps this by having dual engines and some glide ability, but that's definitely an issue with single engine rotor craft, i.e. aerodynamic ability to return to earth safely in the event of power loss.

http://en.wikipedia.org/wiki/Autorotation

I believe that a tailsitter in which the CG is between the rotors is new.

If there is a failure and the craft has some altitude or speed, then it can autorotate to a landing.

In even normal landings there are lots of variables to handle, so I expect that automated systems would handle all landings, both normal ones and emergency landings.

The main reason for the existence and implementation of this craft is that it offers both a VTOL capability and an efficient high-speed cruise capability. Helicopters have lift-drag ratios ranging from 7:1 to 9:1. This craft had a lift drag ratio of 19:1 in a case I evaluated and I was not trying to maximize that ratio. Helicopters have top speeds of around 150 knots, this craft can easily have a top speed of 300 knots.

I proposed earlier that small tiltplanes could be used to drop emergency supplies to people stranded at sea and larger ones could be used to rescue people at sea. In these cases their high speed would be very beneficial.

Small automated tiltplanes could be used for crop dusting.

Small automated tiltplanes can also be used for package delivery in cities from a central location to the tops of buildings. Larger packages would continue to be delivered by truck, but the vast majority of packages shipped are small.

In areas where high speed rail does not exist and where the distances do not justify normal airline services tiltplanes could be used. This would typically be carrying passengers distances of 100 to 300 miles. This would not be a mass-transit solution but a service which could be offered between selected metropolitan hubs where the cost per ride could be justified. The cost would not be low because two pilots would be needed per craft and each craft might carry only 20 to 30 people.

So far, you have morphed this thing into about 5 different types of aircraft, each different enough to require its own type rating and manufacturing methods.

You are beginning to sound like a solution looking for a problem, any problem. _{Can I plagiarise myself?}

And worse, you are starting to sound like joe e fordham and others, who believe so strongly that they are right that they discard logic and clear thinking for their cause.

I look at your craft and see no utility, only novelty. I also see that bullet heading straight for the ground, even at 300MPH.

Good luck. I'll happily admit that I'm wrong when it flies straight and level at 300 MPH.

I am confident that this is a breakthrough rotorcraft technology. Tiltplanes can take off vertically and cruise very efficiently at speeds much higher than helicopters can fly at.

Yes, the concept was born first and no "killer" applications have yet been found for it, but I think that is OK, first the concept then the applications.

Curiously, I am not uncomfortable with this situation; I guess that I love potentially useful new ideas for their own sake.

Good Luck.

I hope that you dreams become reality and you become rich and famous.

I'll be waiting for my serving of crow.

also an interesting design you may not have seen, that could have a similar flight profile, is the is "Duranopter" by Chorete

Wow! The Duranopter is certainly different from anything I have ever seen before! From what I see it seems to consist of a conventional propeller in the rear and a body which is also a propeller or a propulsion means up front. The body also houses what I presume to be a group of rubber bands which are wound up to power the craft.

It certainly does look impressive flying!

John

I that it bordered on your design, because I think that it is essentially a dual rotor craft, with both rotors turning in the same direction, and other internal mass turning in the opposite direction. so it could be something for you to think about, regarding turbulence between the rotors. (remember those old ww1 rotary aircraft engines, so you can have an engine provide the counterrotate)

I realize that your lateral motion is provided by the cyclic pitch of the counter rotating blades, but that wouldn't go away completely with co-rotating rotors, it just wouldn't be as balanced, and the tradeoff would be improved axial lift/thrust. (and there are other ways to provide lateral thrust)

I think that for an individual designer, you set the bar high for innovation. I'm still amazed by your video.. best I've ever seen for engineering. Do you have any airflow diagrams that illustrate the lateral motions (or others)?

Chris

Hi Chris,

Thanks for your kind words.

As you can see on my website, the excellent graphics work was done by:

http://phantom-mouse.com

Their prices were also very reasonable, I felt.

I do not have any airflow diagrams, but a highly respected helicopter engineering expert, Ray Prouty, wrote programs for hover, transition, and cruise in Visual BASIC that I use to model the craft's performance. These programs take virtually everything about the craft into account. Of course, I have to make guesses about a host of variables - to essentially do a preliminary design - in order to run his programs

My design has the two rotors turning in opposite directions. I think that this will work very well, but in a real craft it would be much easier if only one rotor had to be driven, but I see no way around this, and recently I have looked very hard for a way around it.

John

"but I see no way around this, and recently I have looked very hard for a way around it."

I think the same way a Notar does it.. turboshaft jet engine driving the motor, and providing airthrust to counter the forces at play. The trick is to balance and control those forces accurately.

in your case, it might be easier to keep the counter-rotating rotors, but skip the cyclic lateral control, and go directly to thruster-clusters of various flows. (top and bottom) like a lunar lander. large flow thrusters for gross 'directional' movements, and small compressed air thrusters for small fast acting adjustments in attitude, balance, etc.

While I agree with you that the torque and cyclic controls are possible, I'm not sure they will give as much precision as you are hoping for, especially in conditions such as landing in wind on a ship in high seas... you need very fast acting controls.

I think it might be simpler to engineer a solution for torque balancing of the rotors alone, without complicating that with the cyclic lateral stuff...

If you have a turbine capable of producing large volumes of thrust air, you can use that in any event for axial thrust (vectorable tail pipe) as well as being able to divert to larger lateral thrusters top and bottom..

one last 'crazy' idea.. is to use larger 'grasshopper' legs, with compressed air cylinders, that can help the whole vehicle spring into the air, and overcome that burdensome initial takeoff vertical inertia. This would lengthen the lifetime of the rotors by reducing peak loads at that time. (it can also make softer landings on uneven terrain)

I hope you don't mind me throwing ideas in the hat... _{^{(small compulsion I have)}}

I look forward to hearing more about it as the design and testing progresses.

"While I agree with you that the torque and cyclic controls are possible, I'm not sure they will give as much precision as you are hoping for, especially in conditions such as landing in wind on a ship in high seas... you need very fast acting controls."

Yes, I agree. Fast acting controls are absolutely necessary, but this application should not be a particularly difficult one from a controls point of view. If a helicopter is trying to hold station and it is blown away from the position it is trying to hold, it must first roll in the direction it wishes to go, accelerate laterally, roll in the opposite direction, accelerate laterally to slow the craft, and then roll back to upright. Because a tiltplane's rotors are above and below its center of gravity, it can simultaneously command lateral forces from both rotors to move sideways, and then command lateral forces in the opposite direction to stop the motion.

Probably the first tiltplane applications will be using small tiltplanes for automated package delivery. How that might be worked out might be another discussion.

However, because tiltplanes offer both a VTOL capability and good high-speed cruise efficiency, it seems that they ought to also be good for carrying people for distances of, say, 50 to 300 miles where they should compete extremely well with conventional aircraft, rail travel, bus travel, and car travel in terms of point-to-point travel times. The reason I think that they would be able to compete well with conventional aircraft in this regard is that a tiltplane transportation system could be designed to avoid the complex boarding process and taxiing to and from the runway which is needed by airliners. I am thinking that tiltplanes designed for moving people like this might have only one pilot, might carry about 25 people, and would have automated backup systems to land the tiltplane at the intended destination even if the pilot somehow could not.

What do you think? (Please see www.tiltplane.com for more info about tiltplanes.)

In case someone is waiting for more activity on this topic, please note that I started another conversation called "A New & Efficient High-Speed Rotorcraft" and there has been a fair amount of activity there.

jlawren3