A New & Efficient High-Speed Rotorcraft

34point5,

The first three difficulties which you point out are pretty clear:

"...the structural and mechanical difficulties of having a rotor at each end."

"...landing gear is a problem in more than a tiny VTOL model"

"... the large 'hollow drive' on the rear rotor severely limits the cargo through to people carrying applications"

But I am not sure what you have in mind "For the wing question".

Looking at the three difficulties that you point out, one might ask why anyone would ever want to pursue this proposed tiltplane technology.

The main reasons are: it is (1) a VTOL aircraft (2) offering a high speed cruise capability together with (3) a very good flight efficiency. As I said before, in one design I was working on the lift/drag ratio came out to be 19:1 at around 195 Knots and I was not trying to maximize that ratio. The 19:1 value is similar to the lift/drag ratio of airliners - whereas I understand that helicopters have lift/drag ratios ranging from only 7:1 to 9:1.

I can see this technology being applied to small VTOL craft to quickly move packages from one building to another in a large city. But someone has pointed out that it is not easy when a new concept is introduced to guess how it will eventually be used. I agree.

jlawren3

Your answer to Masu:-

masu wrote: " the rotors are going to need to be a darn side bigger than the ones shown in your animation and it's not going to be easy". The rotors are narrow because they operate at relatively high air speeds. (Lift increases with the square of the airspeed.)

Is an answer to another question that he did not ask.

You are slipping away from reality fast.

ANSWER THE QUESTION POSTED!!

He was talking about when the rotor was stopped.........

You said:-

Now about the lift/drag ratio. If the rotor blades were stopped with four of them vertical and four horizontal and the weight of the craft were evenly distributed between the rotors then why wouldn't conventional aircraft principles apply?

Masu said:-

Ok, what you are saying is that you would lock the rotors so that two of the forward rotors were horizontal and two of the rear the same. These would then be pitched to supply lift as the craft moved forward.

GOT IT? No motor power at that time.

Politicians answer questions like that, usually with a "I'm glad you asked me that question!"

Anonymous Poster #1,

When I spoke of the rotors being stopped, I was only using that as a step in trying to explain something. I fully expect that the rotors would always be turning, well, at least as long as the craft is flying!

jlawren3

The question is still open that in the event of an engine failure, what happens to the fuselage (assuming the other engine is still viable)?

Many have asked you here, none of your answers "hold water" (in spite of the fact that you may/claim you have gone to a Naval College)....

I will tell you again, as soon as one engine stops, the torque of the other prop will spin the fuselage at high speed, maybe as high as half the engine revs!! The people inside will lose all their blood and other bodily fluids, within a few seconds. But it won't worry them because they will be dead just as fast.

That is simple physics.....

If to try and prevent this, the motors are "linked" in any way shape or form (as they HAVE to be!), the only way to avoid this is to stop the other motor JUST as quickly.....whether it be a mechanical or electrical or electronic link......now you are in a tube left with no propulsion.......it will probably still spin for a second or two, unless you actually only have one motor driving both props, which means a heavy gearbox and a drive shaft (I think hydraulics will be far too heavy!), assuming that the props themselves can still be controlled.....Control-Alternate-Delete may not be quick enough!!!

This is at least one of the major very basic flaws (certainly not the only one!) of the design that will probably never be properly fixed, which is probably the main reason that this type of design appears not to have been tried!).......as you will not only have the problem of engines stopping, but also electronics failing, for example the control of a prop failing.......all of which will possibly kill the occupants......which is why the object will never get a Certificate of Airworthiness from anyone......

You obviously know about some of these flaws we ask about as you either don't answer back when the questions are posed, or you give an answer that has nothing or little to do with the question in hand.......each and every time.

NO DIRECT "ONE ON ONE" ANSWERS!!!! Implies something to hide.....

Remember, there are very few suckers (if any) on CR4 as we have all seen "Get rich" schemes by the dozen here......

So it's time to leave CR4 and go hunting for suckers somewhere else buddy!!!

The question is still open that in the event of an engine failure, what happens to the fuselage (assuming the other engine is still viable)?

- Any craft carrying people would not have an engine driving each rotor, but the engine or engines would together drive the rotors with suitable gearing and shafting.

Many have asked you here, none of your answers "hold water" (in spite of the fact that you may/claim you have gone to a Naval College)....

- If my answers do not appear to "hold water" that is probably from a communication failure on my side.

I will tell you again, as soon as one engine stops, the torque of the other prop will spin the fuselage at high speed, maybe as high as half the engine revs!! The people inside will lose all their blood and other bodily fluids, within a few seconds. But it won't worry them because they will be dead just as fast.

That is simple physics.....

- You are making the assumption that separate engines would be used to drive each rotor. If a tiltplane were carrying people then a single engine in the center would be used to drive each rotor through drive shafts. But small unmanned craft could easily use an electric motor per rotor.

If to try and prevent this, the motors are "linked" in any way shape or form (as they HAVE to be!), the only way to avoid this is to stop the other motor JUST as quickly.....whether it be a mechanical or electrical or electronic link......now you are in a tube left with no propulsion.......it will probably still spin for a second or two, unless you actually only have one motor driving both props, which means a heavy gearbox and a drive shaft (I think hydraulics will be far too heavy!), assuming that the props themselves can still be controlled.....Control-Alternate-Delete may not be quick enough!!!

- Drive shafts and gearing are the cost of doing business with helicopters. Tiltplanes don't get a free pass in this respect; the rotation of the rotors must be coupled mechanically.

This is at least one of the major very basic flaws (certainly not the only one!) of the design that will probably never be properly fixed, which is probably the main reason that this type of design appears not to have been tried!).......as you will not only have the problem of engines stopping, but also electronics failing, for example the control of a prop failing.......all of which will possibly kill the occupants......which is why the object will never get a Certificate of Airworthiness from anyone......

You obviously know about some of these flaws we ask about as you either don't answer back when the questions are posed, or you give an answer that has nothing or little to do with the question in hand.......each and every time.

NO DIRECT "ONE ON ONE" ANSWERS!!!! Implies something to hide.....

Remember, there are very few suckers (if any) on CR4 as we have all seen "Get rich" schemes by the dozen here......

So it's time to leave CR4 and go hunting for suckers somewhere else buddy!!!

- I am sorry that you feel that way. The tiltplane concept is a solid one. It is an extension of the two-propeller toy which I have mentioned before. It certainly can be designed to carry passengers, an example of which is shown on my website tiltplane.com, but I fully expect that early applications will be unmanned.

Help

My apologies my previous post number #88 was in response to jlawren3's post number #81 not post number #35 as indicated in the heading as I entered it in the wrong place in the discussion.

Hi masu,

There is a two-propeller toy shown in Figure 4 in the paper on the tiltplane.com website. The aircraft I propose is basically an extension of that concept. I am increasing the number of rotor blades per rotor from 2 to 4 and substituting a fuselage with motors to drive the rotors for the stick and the wound-up rubber band. Also, I am adding a pitch angle control for each rotor blade.

It is not clear to me how you can look at a picture of this two-propeller toy and ask:

"If the downward going rotor blade is producing more forward thrust than the upward going rotor blade then wouldn't your aircraft be going backward nor forwards?"

Both the down-going and the up-going rotor blades produce lift when the craft is moving through the air. In a snapshot in time the lift vector from the down-going rotor blade will be leaning in the direction of flight but the lift vector from the up-going rotor blade will be leaning backwards or away from the direction of flight. Well, the down-going rotor blade can be given a steeper angle relative to the air it sees. This will result in it producing more lift and a corresponding larger forward forward thrust component than before. At the same time the up-going rotor blade can be given a reduced angle relative to the air it sees so that the sum of the lift from the two rotor blades will not be increased. The result will be that there will be a net forward thrust component from that rotor.

The aft rotor would be given similar commands so that it also produces a net forward thrust.

There is a turning moment produced by the forward rotor which acts to turn the vehicle, but there is a similar moment in the opposite direction produced in the rear rotor which will cancel out the turning moment from the forward rotor.

jlawren3

There are three points I would like to raise here:

First off in horizontal flight you are not considering the movement of the rotor and consequent relative movement through the air due to the rotation of the rotor. If you add both the forward movement vector to the rotational vector, which at around Mach 0.8 at the tip way will be considerably more than the forward movement vector, the angle of attack of your aerofoils is going to be something like 64° at the wing tip which is way, way, way past the stall angle of any symmetric aerofoil. The fundamental mistake you are making is to no allow properly for the rotational vector for your aerofoils because when you do you will see that they will stall about 10% to 15% of the way out and therefore not create any lift/thrust past this point.

Secondly you stated that there was no new technology in your aircraft then you start talking about rotor blades that can telescope. Now I've see a lot of aircraft in my days and flown both powered aircraft and gliders but I have never ever seen a propeller, wing or aerofoil of any kind that can retract the outer portion by telescoping it into the inner portion. The closest I have seen would be swing wing aircraft and they have now gone out of fashion due to the complexity of the system and cost of maintaining it. I believe that the only swing wing aircraft still in service is the B1-B Lancer and it's Russian copy.

Now I'm not saying that this is impossible to build a telescoping aerofoil, but it certainly new and going to take a hell of a lot of engineering to get just to calculate if it's technically possible let alone practical. By the way, my gut feeling is that with the current technology and materials that are available that it will be neither possible nor practical, but please do the engineering and prove me wrong.

Finally my third point is that there are several designs for small VTOL aircraft specifically designed for the rapid deployment of goods already out there and far more advanced than yours. A couple of them have been shelved due to practicality problems and lack of interest by investors but there is one that is likely to be your nemesis. It's called the Puffin and looks like this.

Now here you're competing with NASA and they have already built a 1/3 scale model for testing the concept. I don't know of the current status but they are a long way ahead of you and I doubt you will have a snowballs chance in hell of getting enough investment to catch up with them. Then again, they may have decided like the previous attempts at tailsiting aircraft, that it just wasn't practical and have ditched the concept.

they do have a cool video for that too... I like that one too. (and the 1/3 scale hover)

Great videos. Many thanks for finding and posting them.

The V22chap on YouTube has made VTOL model aircraft and shows that it can be done at home with very little money and demonstrates that it can work. He is not so young either I see!!!

The OP should start building I feel and then he will have something to show just how good his design is......

Go here anyone and look at all V22chap's videos, though they are another VTOL principle, not Rotocraft:-

http://www.youtube.com/watch?v=fOoPpBKOk5Q&feature=BFa&list=ULwdXvmj1MmJU&lf=mfu_in_order

Andy,

I saw the video and I am really amazed, not so much that the V-22 model can fly, but that a person of presumably ordinary means could build a V-22 model. (The complexity of a V-22 is greater than the complexity in my tiltplane concept.) Each of a V-22's rotors has cyclic and collective pitch control. I think that at least fore-aft cyclic pitch had to have been implemented in this model's rotors, otherwise how else might fore-aft pitch control have been obtained?

I think that, in effect, the person building and flying that model has put together something equal in complexity to two helicopter main rotors plus a drive to tilt the wing. Amazing!

jlawren3

I've been doing some reading on the V-22 Osprey and it indeed utilizes a standard type swashplate on each of the proprotors, however, that doesn't explain how it manages to achieve yaw control when in hover mode.

I did find a video of one carrying out a yaw manoeuvre while hovering and the flapavons on the wings seem to be working overtime. This leads me to guess that the yaw control is achieved in hover mode by use of the flapavons, but as I said this is a guess and somebody else may know more about how the Osprey's controls work.

You guess correctly - yaw is an aileron like lift vectoring when the wing is 'vertical'.

Of interest the rotors/engines are connected via a shaft (and transmission) - should one fail - so it A. doesn't instantly 'turn turtle', B. so it can keep airborne on one.

Without considering such 'small technicalities' a 'concept' never becomes a 'design'.

For instance, just think how critical 'weight and balance' (so attitude) become 'hanging on two rotor shafts' - and you see why large 'flapavons' have their work cut out.

That aside; I still don't see how the OP's design is going to fly anywhere near 'horizontal' with out some 'body-lift' geometry, or other lift surfaces to 'pivot forces around'.

Not having a force couple, is a bit like one handed clapping

Accurate & funny"!!

I realize that the text below is a long explanation. An overview is that the rotor blades produce both lift and a net forward thrust. If you wish to understand how this can be done, please read on.

Assuming four blades per rotor and that that the airflow direction is along the length of the craft, then if each of the rotors were stopped with two rotor blades horizontal and two vertical and if the rotor blades on both rotors were aligned with the flow, then there would be no rotor lift. Now if each of the four horizontal rotor blades were given a small angle of attack, then lift would be produced by the four horizontal rotor blades. Suppose that each horizontal rotor blade, from that small angle of attack, produced an amount of lift equal to ¼ of the weight of the craft. Then the craft would be self-supporting, but the rotor blades would not be producing any thrust to overcome aerodynamic drag.

The next step is to imagine that the rotor blades are turning with each rotor blade aligned with the flow when it is vertical and given a small angle of attack when it is horizontal, producing lift equal to ¼ of the weight of the craft. (As a rotor turns the angles of attack of the rotor blades would need to be adjusted continuously so that the total lift from each rotor was ½ of the weight of the craft.) Also note that the lift produced by the down-going blades would have a forward component and the lift produced by the up-going rotor blades would have an aft component.

So the craft would continue to be self-supporting, but drag would be produced by the airflow over the rotor blades and the fuselage. What is needed is for the pitch angles of the down-going rotor blades to be increased so that their lift will be increased and for the pitch angles of the up-going rotor blades to be reduced so that their lift will be decreased. These pitch angle changes can be made so that the total lift from each rotor is the same.

There is no free lunch. Because more lift is being produced by the down-going rotor blades and less lift is being produced by the up-going rotor blades, a torque must be applied to the rotor to keep it turning in the direction it is going. This is expected. The power needed to turn the rotor can be calculated from this torque and the rotor's RPM.

As we have discussed, when a tiltplane is cruising the rotor blades would be making long slow spirals through the air. Suppose that the airspeed of the craft is 300 mph (440 ft/sec) and suppose that the rotational speed of the rotors gives the rotor tips a tangential speed relative to the craft of 45 MPH (66 ft/sec). Consider the case where a rotor blade tip is descending. Such a rotor blade tip would see the approaching air due to the speed of the craft at 440 ft/sec combined with the rotation of the rotor at 66 ft/sec giving a net airspeed over the rotor tips of 444.9 ft/sec. (The square root of the sum of the squares). If the rotor blades were not turning one could say that the air would be approaching the rotor blades at zero degrees. In the case we are considering, the angle of the air approaching the rotor blades would be an angle whose tangent is 45/300 or 8.53 degrees. So the rotor blades would be making long shallow spirals through the air.

This long explanation is given so that it will be clear that, when the craft is flying horizontally, the speed of the air over the rotors is really not much higher than the basic speed of the craft through the air. It is true that, in the example above, the 45 MPH tip speed of the rotors was "picked out of the air", but that speed is representative of what is expected

- jlawren3

"So the rotor blades would be making long shallow spirals through the air."

I don't believe that your rotor blades would be making long slow spirals through the air as I believe that you have grossly underestimated the rotational speed of the rotors. However, it is possible to calculate the speed of the rotors but you will have to supply the following data:

• Profile of the rotor blades
• Dimensions of the rotor blades
• Total mass of the aircraft as a whole including the rotors, airframe, engines, transmission, fuel, payload etcetera.

Now if you can't supply all of these then there is no way that you can possibly know if you craft will be able to fly or not. So if you do not have the required information then I suggest you get it and then come back to this discussion when you do.

masu,

OK. I hope to fully respond to your request on this forum later today.

There is an issue about whether a gear shift should be used for the rotor speeds or not. One set of data I will report will be for a craft with a gear shift for the rotors; one rotor RPM will be chosen to minimize the transition power and the other will be a lower RPM chosen to minimize the cruising power at 300 Knots. The other craft will have a single rotor RPM chosen a bit lower than the optimum transition RPM which minimized the transition power; I will arbitrarily choose that RPM so that the transition power is increased by about 10% over the minimum transition power above. Then it will be interesting to see how much the cruising power required at 300 Knots will be increased by using that higher cruising RPM compared with the craft which used an RPM optimized for cruising at 300 Knots.

By the way, the estimates for the fuselage drag which I will be using will be based on using a clean fuselage without the bubble cockpit canopy which I show in the drawings.

Also, there is an issue about the twist in the rotor blades. Unlike a helicopter, for a good cruising efficiency there must be twist built into the rotor blades. I have been using a twist in the rotor blades all along, but it is very unlikely that it will be the optimum twist for the different flight modes of the two designs that I will be reporting on. Later I might report on what effect optimizing the rotor blade twist for each of these two designs will have on their performance.

Also, there are issues about the craft's size, weight, and proportions. Lately I have been assuming that the rotor diameters will be five times the fuselage diameter so I will go with that. The hover and transition power will be greatly affected by the craft's weight. Ideally I would give you one craft size with three different craft weights so it would be quite clear how the weight affects the performance, but for this exercise I will choose one weight. Also, the cruising performance can be improved by retracting the outer proportion of the rotor blades. That will not be done in these estimates; people have questioned the wisdom of doing that anyway because it is introducing a fair amount of complexity to reduce the overall skin friction drag by a fairly small percentage.

Also, I will be working with the standard air density found at an altitude of 6000 ft. This is a conservative assumption; I think that most real-world landing and takeoff situations will be in denser air at lower altitudes which will make it easier to obtain the needed lift.

Comments?

jlawren3

• "Also, there is an issue about the twist in the rotor blades. Unlike a helicopter, for a good cruising efficiency there must be twist built into the rotor blades. I have been using a twist in the rotor blades all along, but it is very unlikely that it will be the optimum twist for the different flight modes of the two designs that I will be reporting on. Later I might report on what effect optimizing the rotor blade twist for each of these two designs will have on their performance."

You will not be able to put any sort of twist on the blades if you want the thing to work the way you described it. This is because you will have to reverse the direction of lift on one side of the craft so the blades must not only be symmetrical aerofoils (have identical top and bottom profiles) but have no twist on them, otherwise you will not be able to get lift out of the blade on both sides of the craft as it's moving forward.

• "Also, I will be working with the standard air density found at an altitude of 6000 ft."

Aeronautical engineers and pilots for that matter do all their initial calculations using what's called the International Standard Atmosphere or ISA for short. After you have done the calculations using this you then apply correcting factors to allow for humidity, temperature, altitude, atmospheric pressure etcetera. However, you always start out with the ISA and calculate all the crafts performance using this.

masu,

Unlike in helicopters, there is never a reverse direction of air flow over the rotor blades in tiltplanes.

I am assuming that a symmetrical airfoil will be used. In hover the lift is on the top side of the rotor blades but in cruise the lift is on the top side of the down-going rotor blades and on the bottom side of the up-going rotor blades.

Now about air density. I am using programs written by Ray Prouty who is a well known and highly respected aeronautical engineering consultant. The relevant line in the program about this is:

RHO = .001988 'air density at 6000 ft. altitude; slugs/ft^3

For sea level work, in the program I could have enabled this line:

RHO = 0.002378 'SEA LEVEL

Do these values look OK to you?

For this preliminary work I believe that it is not necessary to specify the air temperature and humidity. The above values for RHO undoubtedly reflect some assumptions about the air temperature and humidity, but I do not know what they are.

jlawren3

If air density is your biggest problem, then you are okay.

I believe you still have bigger fish to fry.

LOL!

Always Where Under Where?????

NEAT NEAT NEAT!!!!

I never said it out loud........just thought my Latin was completely off!!!

What I am learning here is great. Not that I need or want to know it's just the way you present it that makes me want to pick it up and store it for whatever is around the next corner.

Good work masu, I appreciate it. Not to forget the other contributors here .

Fly slow is the go, Kigh

Vot German?

Nobody Menschen ze war

The NFO ^{not flying object} is too ugly to fly. Horse power to overcome uglyness?

I'll leave it to you guys. I go more by instinct.

LOL!!

I'll get back to everybody within about 10 hours from now. I welcome the discussion.

jlawren3

So are you saying, in horizontal flight;

The greater induced drag of the down-going-blade equals gravity?

Meaning the body is effectively held up by moments induced outboard on diagonal corners.

And/or;

The pitch change across the rotor disc is providing 'leverage' to cantilever the body?

If so; a blade goes, upward at min drag = zero thrust quadrant. Then coarse = large thrust/drag for a 'leverage' quadrant. Then 'coarser' for 'anti-gravity' quadrant. Then negative = large drag for a minus leverage quadrant.

That 'flip' 'coarse positive to coarse negative' seems quite a challenge to achieve in rpm and cyclic real-time without massive blade stress/fatigue challenges.

3 quadrants of high drag (per blade, per rotor) seems a lot of power going to drag compared to a wing.

34point5,

I don't follow the problems you are describing.

Here is a step-wise explanation that I have used before:

1) Suppose that there are four blades per rotor and that they are momentarily stopped with four blades vertical and four horizontal and with the rotor blades aligned with the flow. (To keep things simple let's ignore built-in rotor blade twist at this point.) Let's say that the craft is moving through the air at 300 knots. There will be no lift; only axial drag forces will be present.

2) Now let's imagine that the pitch of each horizontal rotor blade is increased an amount necessary for each of the four horizontal rotor blades to pick up 1/4 of the weight of the craft. You could say that the craft would then be flying, but it would not be propelling itself forward to overcome the drag forces which will be present.

3) Now imagine that the rotor blades begin to turn at a relatively low rate so that the rotor blade tips are making long slow spirals through the air. Also imagine that when each of the four rotor blades is horizontal it is given an angle of attack so that the total lift from each rotor is equal to half the weight of the craft. It will not be hard to also imagine that when the four rotor blades in each rotor are at 45 degree angles relative to the horizon that the pitches of the rotor blades can be adjusted so that each rotor still lifts half of the weight of the craft.

4) In the above case the pitch of the down-going rotor blades can be increased and the pitch of the up-going rotor blades can be reduced, but these changes would be made in such a way as to keep the lift produced by each rotor the same.

It can be shown that when the down-going rotor blades are producing more lift, this lift can be broken down into two components with one component acting vertically, lifting the craft, and one component acting in the forward direction. The up-going rotor blade lift will also have two components, one lifting the craft and one acting in the rearward direction. The net effect will be that there will be a net forward thrust produced by each rotor because the lift of the down-going rotor blades was made larger than the lift produced by the up-going rotor blades. Parameters can be chosen so that the net forward thrust produced by the two rotors equals the overall drag of the craft. This means that the craft will be flying in a self-sustaining way, but in doing so, of course, power is required.

This is the way I think about the process. I wasn't able to follow your explanation. Are you able to follow mine?

jlawren3

Yes, more or less the same thing, except I'm factoring in 'pitch ~ lift ~ drag', and so looking at the 'big pitch' required to create the downward force in the 'drag = weight' quadrant, minus the 'upward drag' which must be 'zero pitch ~ lift ~ drag', (which equals 'zero thrust) so as to not add to 'weight'.

What the above means is a highly asymmetric axial force (leverage) on the rotor disc.

(and a twist and velocity conundrum for the rear rotor disc required asymmetry to match)

And; 'drag ↓ - drag ↑ = weight', being the case; as you add payload (over that of a stick and an elastic band), it means some other form of lift will probably be far more 'drag' efficient ^{_{(and far kinder to your blades and rotor head)}}.

If the craft moved through the air at 300 MPH and if the rotors were stopped with two blades on each rotor horizontal, and if those four rotor blades were set to an angle of attach so that they each lifted 1/4 the weight of the craft, then the craft would be self-supporting, though not self-propelling. The efficiency of this craft would be dependent on a number of factors, but it is not hard to imagine that a craft like this could have a glide ratio of, say, 24:1. The efficiency would not be diminished significantly if the rotor blades were made to rotate, making slow spirals through the air. I am assuming that they would take on suitable pitch angles as they rotated to keep the net lift on the craft constant. I think that the lift/drag ratio would remain close to 24:1 as the rotors turn. Of course, propulsive power could then be added. But I do not see any reason why the overall efficiency would be significantly reduced.

You can't have your 'lift cake' and eat it.

Stop the rotor and set both horizontal blades at say +5⁰ to the body axis, then glide from altitude.

Fine - typical rotor blades 'cantilevered' so - will snap off

Try setting both blades instantaneously to +5⁰ to body axis, when rotating - and they will snap off.

I haven't "been through the numbers" yet on the rotor blade design, but I would be very surprised if the whole tiltplane concept would become impractical because of rotor blade bending stresses. For one thing, since the rotor blades will always be turning, centrifugal forces can be used to an advantage to help reduce the rotor blade bending stresses. Also, I plan to use carbon fibers, with their very high strength-to-weight ratio, to provide the needed bending strength in the rotor blades.

You're going to be pushing it to get 24:1 L/D factors out of symmetrical aerofoils. You'e talking about glider type performance and glider wings are extremely complex asymmetrical aerofoils with things like concave lower surfaces and turbulator tabs to ensure laminar flow.

As I have said before, I have programs written by Ray Prouty, a respected helicopter consultant and, when I substitute appropriate values for all the parameters needed to describe a tiltplane, I can get lift/drag ratios as high as 19:1 at about 195 MPH at 6000 ft., a L/D value which, I understand, is typical of airliners. This was using symmetrical rotor blades. Considering that in a 4-bladed rotor there may be instantaneously only two rotor blades producing lift with the others contributing to the drag, a value of 19:1 already seems like a high number. But I do believe that if narrower rotor blades are used than I have been using, even higher ratios should be possible. Of course, from a strength point of view, and the extra materials that may be needed to provide that strength, narrower rotor blades may not actually be practical. But I do plan to find out if, at least on paper, higher values can be obtained using narrower rotor blades.

I recognize your concern: how can such high L/D values even be possible in a rotorcraft? Here is a thought: fixed-wing aircraft need a large amount of wing area to become airborne, but that works against them when cruising. The rotors of tiltplanes do not operate under that constraint.

jlawren3

"Here is a thought: fixed-wing aircraft need a large amount of wing area to become airborne, but that works against them when cruising."

That's why fixed wing aircraft have things like flaps, slats, spoilers, air brakes (actually breaks is more apt), etcetera so that they can create lift at relatively low speeds yet still have highly slippery clean wings when cruising. They also don't use symmetrical aerofoils.

You're stuck with using a symmetric aerofoil the only control over which you have is its airspeed and angle of attack and that's going to severely limit your aircraft's performance. To start with you are going to have the rotors moving through the air as fast as your aircrafts cruising speed around 70% of the way along their span at take-off to generate sufficient lift to get your aircraft off the ground. This is going to give you a quiet substantial rotational speed that is going to be very difficult to reduce when you transition to horizontal flight to get the craft working the way you think it will.

What you're talking about is taking something with a rotor like a helicopter and getting it to fly with its rotor tipped on its side. I've seen this done, but not for long because the helicopter starts to fall from the sky very quickly.

Actually a helicopter on its side is very much like your aircraft with the exception that most of them only have one rotor and adding a second isn't going to help.

Anyway, without the information I have asked you for I can't work out if you craft will even be able to get off the ground let alone transition to horizontal flight and work the way you described. Personally I believe you have grossly underestimated the rotational speed that will be required for the rotors and this is going to seriously alter the way your aircraft is going to fly.

GA because everything you say makes sense, even to me who has only built model aircraft, so I can also say that understanding the problems here is not rocket science......(with your excellent explanations)....thanks.

masu,

I agree with your first and second paragraphs. I have recently concluded that tiltplanes need to operate their rotors at two different rotor speeds, a higher speed for hovering and transition and a lower speed for cruising.

Please write me on my tiltplane.com website reiterating your request for information.

-jlawren3

"Please write me on my tiltplane.com website reiterating your request for information."

Why can't you supply the information requested directly into this discussion which you created about your aircraft design.

All I'm asking for is the following:

• Anticipated all up mass of your aircraft
• Length of each of the symmetrical aerofoils
• Profile of each of the symmetrical aerofoils
• Cruising speed

Now since it's your aircraft design not knowing or being able to supply such basic information about your aircraft only suggests that you haven't really thought about your design in any detail at all and therefore neither you nor I can know if it will operate as you have described.

In reply to your completely valid requests, I doubt completely that the "dreamerdesigner" has got that far in having factual/actual data at his fingertips......let us watch and wait and see what comes back.......

I want to see at least a fully fling model before I will be convinced....

masu,

You said, "Actually a helicopter on its side is very much like your aircraft..." That is true, but with this major caveat: the center of gravity of tiltplanes is between the two rotors. I do not know of another rotorcraft like mine, except the toy that consists of a stick with propellers mounted at each end. To fly this toy one winds up the rubber band which is connected to the two propellers and then releases it; it then flies more or less in the direction that it was pointed. That toy is shown in Figure 4 in the conference paper which is on my tiltplane website.

Because a helicopter does not have separated rotors and and does not tilt its axis 90 degrees to cruise, as my craft does, it is very limited in its top speed compared to tiltplanes.

-jlawren3

"Because a helicopter does not have separated rotors and and does not tilt its axis 90 degrees to cruise, as my craft does, it is very limited in its top speed compared to tiltplanes"

http://en.wikipedia.org/wiki/Sikorsky_X2

Maximum speed: 260 knots^[20] (299 mph, 481 km/h)

Powerplant: 1 × LHTEC T800-LHT-801 turboshaft, 1300-1800 shp (1000-1340 kW)

power/mass (derived) 277 - 372 W/kg

-------------

V-22 Osprey

(variable body tilt plane)

• Maximum speed: 250 knots (463 km/h, 288 mph) at sea level / 305 kn (565 km/h; 351 mph) at 15,000 ft (4,600 m)
• Power/mass: 427 W/kg

------------------------

6 Specifications (King Air B200)

Maximum speed: 294 knots (339 mph, 545 km/h) at 25,000 ft (7,600m)

Powerplant: 2 × Pratt & Whitney Canada PT6A-42 turboprops, 850 shp (635kW) each

Power/mass: 220 W/kg

--------------------------

Meaning, tilting rotors does not mean they are efficient propellers

Besides, operating over 250 knots has other complications

link

34point5,

I wrote, "Because a helicopter does not have separated rotors and and does not tilt its axis 90 degrees to cruise, as my craft does, it is very limited in its top speed compared to tiltplanes".

I guess I should have said "a conventional helicopter" instead of just "a helicopter".

I think that you mentioned three different aircraft with high cruising speeds in order to show that my statement above is incorrect:(1) The Sikorsky X2, (2) the V-22 Osprey, and (3) a twin-engine light plane.

Here are my comments:

(1) The Sikorsky X2 is, in my opinion, a very intelligent concept. With the two counter-rotating rotors it is not plagued by a retreating-blade-stall problem. Well, the retreating blades do stall, but it is not a problem because, with two counter-rotating rotors, the craft has a rotor with advancing rotor blades on each side of the craft. Also, because of its pusher propeller, the craft does not need to tilt to large nose-down angles to achieve high forward speeds. If the Sikorsky X2 were to be compared with a tiltplane of similar fuselage size, then most people would probably agree that the tiltplane is aerodynamically cleaner when cruising than the Sikorsky X2 is. I do not have enough information to compare the cruise efficiency of the two craft, but I expect that, for craft of similar fuselage sizes and overall weights, the cruise efficiency will be better for tiltplanes. For one thing the rotor blades in tiltplanes play a dual role; they supply both lift for the craft and also provide propulsion. Also, tiltplanes do not have an exposed column supporting the rotors - which is bound to contribute a lot of drag.

(2) The V-22 Osprey, of course, tilts its rotors as it goes from hovering to conventional horizontal flight - which I think is also a very reasonable concept. It actually illustrates the converse of what I wrote above: it is a craft with separated rotors which do tilt 90 degrees in order to cruise, giving it the potential of having a high top speed. But, compared to the tiltplane concept, the V-22 Osprey is more complex. The rotors, I understand, have cyclic pitch and variable pitch which compare with the cyclic pitch and variable pitch which would be implemented in a tiltplane's rotors. But the V-22 also has the added complexity of being able to tilt its rotors. I also expect that if the cruising efficiencies of both craft were compared at, say, 250 Knots, then the cruising efficiency of tiltplanes would be higher because the surface area of the eight rotor blades in tiltplanes will be a lot less than the surface area of all the parts of a V-22 which are outside of its fuselage.

(3) The twin engine light plane you mentioned does not really belong in this list because it is not a VTOL aircraft, but I do have some comments relative to fixed-wing aircraft. I remember that, for one tiltplane configuration which I analyzed, at 195 Knots the lift/drag ratio was 19:1. I wonder if the light plane you mentioned has a lift/drag ratio which is that good and at what speed its best lift/drag ratio is realized. I can almost guarantee that its best lift/drag ratio will be at a lower speed than 195 Knots because it appears to have much more wing area and control surface areas than tiltplanes have rotor areas. If this is true, then, unless the craft's lift/drag ratio is a lot higher than 19:1, this means that, at a speed of 250 Knots, a typical airplane will have a poorer lift/drag ratio than the tiltplane which I mentioned above will have at 250 Knots.

Some people have suggested that my tiltplane VTOL concept is too complicated to be useful. But, I believe that, if you compare it with the Sikorsky X2 and the V-22 Osprey, two other VTOL aircraft with high top speeds, you will agree that it is less complicated than either of these other aircraft.

jlawren3

I don't think anyone doubts your tilt-plane can be made to take off vertically.

(though landing may be an adventure in a piloted version)

The main 'exploration' is the means and power requirement for tilt-plane 'horizontal flight'.

It may well be that flying with a 45⁰ attitude is the solution. Then the 'body lift' drag should stop it sliding off the rotor discs like a nose down helicopter.

Will you then reach 250 knots? Given enough power, why not.

The fixed wing example is in there for comparison of power to weight. With all it's terrible 'wing drag' and tiny propellers, it's faster for around half the power per kg.

This does not speak of a higher lift/drag ratio - quite the opposite.

34point5,

I think that I have somehow not successfully conveyed the basic horizontal flight concept of the tiltplane. I expect that some readers are following my reasoning, but I have to assume that many others, like you, are not following it.

Imagine two hypothetical flight models. Imagine that both have similar fuselage and rotor sizes and shapes. Imagine both moving horizontally through the air at good air speeds. Let us agree that, for this immediate discussion, we will ignore issues about rotor blade twist. Real craft will need to have twist in their rotor blades, but it is more straightforward to not think about that for this discussion.

Now let's imagine that the first craft holds its 8 rotor blades fixed with two blades on each rotor vertical and two horizontal. And lets go a step further and say that all 8 rotor blades on this craft are aligned with the flow so that there are no lift forces present on any of the rotor blades - only drag forces due to the drag of the air moving over the rotor blades. Now let's imagine giving each of the horizontal rotor blades a small up pitch angle - a value just large enough with the current air speed to produce a lift force on each of the four horizontal rotor blades which, when all four lift forces are added together, is equal to the weight of the craft. Well, the craft would be then be self-supporting but it would not be propelling itself forward. In fact, air drag would be present so that a small forward force would need to be supplied by a sting that would be provided to support the craft.

Now let's talk about the second craft. First let's imagine that it is subjected to the same velocity of airflow along its axis as the first craft but lets imagine that its rotors are free to turn and are, in fact, turning, each in opposite directions. But let us not imagine that they are whirling at a high speed, but rather that each rotor blade tip is making long slow spirals through the air. The tip of each rotor blade might be moving through the air with only a 10 degree slope relative to the air approaching the rotor. The axial drag on the whole craft would be very similar to what is was on the other craft in the earlier case where the rotor blades were not rotating and had no lift. In the present case though, the axial drag would be a slightly higher because the rotor blades are approaching the air with a small speed of rotation so that the speed of the air over the rotor blades is slightly higher that the speed of the air over the rotors in the non-rotating case.

Now let's go a step further with the these two rotors which are rotating freely in the airflow. Let's imagine that, when the rotor blades are at any angle except vertical, they are given a small angle of attack which results in enough lift, when all the lift forces are added together, to support the weight of the craft. Now we have to say that the rotor blades would no longer be turning freely, but would need to be driven at a constant speed. The down-going rotor blades would produce lift forces which also have a forward component; the up-going rotor blades would produce lift forces which also have an aft-directed component. Thus far the craft would not be propelling itself because the fore and aft forces produced would roughly cancel each other. Please note the total axial drag is not too different from the total axial drag present in the previous non-rotating case. The drag is only slightly higher because the rotor blades are moving through the air on a 10 degree slope and are not approaching the air without turning as was the case above.

And finally imagine that the pitch of the down-going rotor blades is increased as they turn so that they produce more lift that the up-going rotor blades. So that the total lift applied to the craft will be constant, imagine that the pitch of the up-going rotor blades will be reduced. The net result will be that, because of the greater lift generated by the down-going rotor blades than the up-going rotor blades, there will be a greater forward thrust component from the down-going rotor blades than the aft-thrust component from the up-going rotor blades. This difference will result in the craft being propelled forward.

I hope that this adequately explains how both lift and propulsion would be produced by the rotor blades. Additional wings are not needed to support the weight of the craft when it is flying horizontally.

While the above is just words, programs have been written in BASIC by the well-known rotorcraft consultant Ray Prouty which embody this understanding of rotor blade pitch angles, lift, drag and rotational speeds. These programs seems to give very consistent and believable results.

Questions?

jlawren3

No questions. Got that day 1. Hence "drag↓ - drag↑ = weight"

Might have been quicker to say: It's the paddle version of a Harrier with 2 diagonal nozzles choked and inverted.

Has Ray got a hp for 'weight' number?

I have questions.

"The down-going rotor blades would produce lift forces which also have a forward component; the up-going rotor blades would produce lift forces which also have an aft-directed component"

I can see the ↓ blades producing a very small amount of lift at AOA under 15°, but I think that the ↑ blades will actually be removing an equivalent amount of lift, resulting in zero lift. If there is lift in the ↓ blades, it is of the kinetic type, not the aerodynamic type, and therefore, the same kinetic push is being applied in the opposite direction by the ↑ blades...

The only lift I see when horizontal is the body itself. Otherwise it is a purely ballistic object when horizontal, in my current view.

Can you please provide more detail about how the lift is achieved on each blade, when the craft is horizontal, because I can't see it at the moment.

Chris

"Anything is possible. You can be told that you have a 90-percent chance or a 50-percent chance or a 1-percent chance, but you have to believe, and you have to fight." -- Lance Armstrong, 21st century cyclist and 6 time Tour de France winner

Actually you're not being totally fair with the V-22 Osprey as it's designed to be able to fly with one engine out therefore it's operational power to mass ratio is more like 214 Wkg^-1, although it would not be able to fly in cruse mode as fast it can still perform a vertical landing with one engine down.

The main advantage that the Osprey has over conventional helicopters is its operational range. The chart below from Wikipedia compares the operational radius of the V-22 Osprey with the CH-46E. Not only can the V-22 carry a larger payload and has a much greater operational radius but it can cruse 100 knots faster.

Masu, that diagram you kindly posted demonstrates very clearly for anyone with the slightest modicum of understanding just how useful wings can be!!!!! It proves once and for all that the positive effects FAR outweigh any negative drag effects.

(the fact that a large percentage of modern aircraft still use wings for lift, control and stabilization is a simple fact. Forgetting for the moment the extra safety that wings provide when engine failures occur..)

I personally feel that most of us here already knew this, but its good for the rest to have it shown in a manner that leaves no possible argument open for discussion.

Simply put, aircraft without any form of wing or shape to allow "flying" (helicopters are generally so made), or any form of stabilization (only the Tiltplane as far as I aware, even helicopters need to stabilize themselves against torque effects in some way), are probably never going to fly safely, if at all......

....this results in a "win - Win" situation for the V22.....I think that once all the "foibles" of the computer control are ironed out, that will be a world beater.

The OP should stop talking and start "doing", building say a 1/4 scale model for full flight demonstration under remote control, as the time for discussion is way past.

Either it will work or it will not, his protests and arguments will not help it further, in fact they make the apparent situation worse and worse (he fails to comprehend this completely). Only a real proper working and flying version can improve the name of this concept......it does not matter what size it is to start with, model or final version. It simply must be built and tested.

I am not a betting man, but I do understand that this idea has a far less than 10% possibility of ever being built, let alone to fly properly. Anyone with any knowledge of the way any aircraft work will be able to see that....

So Mr Tiltplane designer, "PUT UP OR SHUT UP!!"

I wasn't going for any other point past power per kg aloft in horizontal flight [in the OP's stated performance envelope] for the 3 existing methodologies.

That the presence of a wing on the V-22 also allows it not to glide like a brick, I thought would 'over complicate'.

Perhaps the 'unfair' part is I couldn't find a common base of; mass, 'cruse speed', at one altitude for the 3, so just had to go with MTO and max rated power.

Which says little in reality without factoring in rate of climb and the host of 'performance envelope' variables and safety allowances, like the difference in MTO and MLW, to which you also clandestinely allude.

The alternate approach is to nominate a mass ourselves - say 2000 kg and look at a blade trying to provide half of that by 'drag' several meters outboard of the fuselage, in terms of 'leverage', so required speed and torque - so hp. [and see if there is anything left for payload, should said paddle not snap off]

But meanwhile, no slur on the V-22 intended.

"The alternate approach is to nominate a mass ourselves - say 2000 kg and look at a blade trying to provide half of that by 'drag' several meters outboard of the fuselage, in terms of 'leverage', so required speed and torque - so hp."

Another way to look at is that if you have a given mass that is being suspended and have a known rotor diameter then you can calculate how much air has to be passed through the blade's arc to produce an upwards acceleration of 9.81 ms^-2.

However, in the case of the tiltplane you have the problem of two coaxial rotors and much of the air passing through the upper rotor will also pass through the lower rotor so you can't just say that the effective area that the rotors can accelerate air through is twice the rotor diameter.

In this situation it's going to be a case of working how fast the aerofoils must travel through the air to produce the required lift. Considering lift is a function of the square of the airspeed then you can calculate the rotational speed of the rotors by assuming that the required speed is achieved at approximately 0.707 (the inverse of the square root of 2) of the way along the rotor blade.

masu and all,

This evening I will post characteristics of some example "tiltplanes" with details including craft diameter, rotor diameter, rotor dimensions, RPM, craft weight, etc. I will give max transition power, hover power and cruise power at 300 Knots.

What size tiltplanes would people like to see data on? Is a 300 Knot top speed appropriate in your opinion? Would one model designed for 400 Knots be interesting?

I have programs in BASIC written by Ray Prouty, so these estimates should be pretty solid.

jlawren3

• "What size tiltplanes would people like to see data on? Is a 300 Knot top speed appropriate in your opinion?"

How about we work on a 2 seat tiltplane like the one shown in the video.

• "Would one model designed for 400 Knots be interesting?"

Let's just work on a single design for the moment and see if the craft will be capable of first of getting off the ground.

Most modern aircraft are designed to still fly with some amounts of engine failures or power losses, but I still fail to understand from the OP how he anticipates to handle this.

He needs to answer in a logical and understandable way for all of us here, as to how he will handle power loss of one or both engines. If it is to remain a secret, then he must get on with a flying version as quickly as possible....

To me this also means that each rotor (where you are particularly concerned at this moment) must be TWICE as effective to give the craft some semblance of positive lift when say a motor/rotor fails, as losing 50% of your lifting/flying power must result in a dramatic loss of height and quickly (forgetting the awful torque effects as I have brought up several times!).

The question has been asked before, but only completely unsatisfactory or no answer has resulted. This is obviously another aspect of the design that has not been addressed in any proper manner......one of many I feel.....

Also none of the answers given to questions, "Dovetail" in with any of the other answers given either, as they have and MUST do for an aircraft to fly and fly safely.....for example an answer today may refute completely an answer of yesterday.......

The safety airbag idea from the OP is also useless as dropping out of the air at probably several hundreds of MPH and expecting such a bag to gently enough slow up the human body within the few meters of its thickness is simply another demonstration of the OPs TOTAL lack of knowledge of any basic engineering principles.

The bag (I do not think that this idea has ANY REAL validity) may need to have a diameter of at least (guessing!) at least 50 meters (25 meters to the center/radius, therefore 25 meters to go from say 200mph to 0 mph, and the humans would still be needed to be cocooned in an "all over" body suit to stop their heads being pulled off by the possible resulting deceleration streses.......This must be considered if say you were flying at say 50 meters high and then you crossed the grand canyon for example...........

Seriously, having been watching this blog for some weeks now, I am of the opinion that either the OP is an out and out scammer looking for a $500,000 grant from somebody (according to one of his websites) or he has severe personality disorders that preclude him understanding reality and engineering principles.....I guess I will have to wait and see which it is....

At least he is keeping us all off the streets!!!

My comment/s are in the horizontal flight context, where [according to the OP] gravity is resisted by the drag of the two down-going blades [and enhanced by the drag of the two up-going blades]

But, yes, one could regard the center of drag as at 0.707r. So as I'd guess 2000 kg MTO would require around a 6 m rotor Ø [pair]. So this point is at about 2.1m r and exerting say 1.2 times 1000 kg [drag↓ - drag↑]

As only about 30⁰ of arc is effective; in a 4 blade design, there is a dwell of 30⁰ until the next enters the effective zone, so say, being generous, we only need twice 1200 kg to meet average lift.

Thing is, this is a substantially stalled, or fully stalled aerofoil, or basically 'flat' to the air-stream. This presents an interesting moment of inertia and torsional stiffness problem for the blade designer. Rather like a non-tapered wing with all the lift outboard, suffering a high-speed stall.

I suppose the 'plus' is the rotor is going to be going like the clappers to generate 2400 kg of drag out of the last third of about a 300 mm wide 'paddle' - so some tension will be present.

Not too sure how that helps with the massive shedding turbulence however.

"My comment/s are in the horizontal flight context, where [according to the OP] gravity is resisted by the drag of the two down-going blades [and enhanced by the drag of the two up-going blades]"

That's not the way I read his description. I think the way he sees it working is that the blades will be angled so that the forward motion of the craft is sufficient for the four horizontal blades to supply enough lift the keep the craft airborne. He's then adjusting the pitch on the rotors to allow for the rotational vector which he believes will be relatively small or about 10% of the forward airspeed so that the aerofoils see the correct angle of attack to the relative motion of the air. He's also using this adjusted angle of attack to produce the thrust needed to move the craft forward.

However, I believe he has made to fundamental mistakes:

• Firstly he has grossly underestimated the rotational speed of the rotors and therefore the angle required for them to see a workable relative angle of attack. This would then substantially change the angle of the lift created by the blades and require an unrealistic angle of attack to support the craft's weight.
• Secondly you can only adjust the pitch of the rotor to achieve the correct angle of attack at one particular radius on the rotor. This is because further out the rotational speed component will be greater and close in lower.

· #189 "Re: A New & Efficient High-Speed Rotor craft" by masu on 11/14/2011 8:28 AM

• "What size tiltplanes would people like to see data on? Is a 300 Knot top speed appropriate in your opinion?"

How about we work on a 2 seat tiltplane like the one shown in the video.

• "Would one model designed for 400 Knots be interesting?"

Let's just work on a single design for the moment and see if the craft will be capable of first of getting off the ground.

jlawren3: fine

· #190 "Re: A New & Efficient High-Speed Rotor craft" by Andy Germany on 11/14/2011 8:33 AM

11/14/2011 8:33 AM

Most modern aircraft are designed to still fly with some amounts of engine failures or power losses, but I still fail to understand from the OP how he anticipates to handle this.

He needs to answer in a logical and understandable way for all of us here, as to how he will handle power loss of one or both engines. If it is to remain a secret, then he must get on with a flying version as quickly as possible....

jlawren3: I expect both rotors to be mechanically coupled together. If there are multiple engines, then there would need to be a way of decoupling a failing one.

To me this also means that each rotor (where you are particularly concerned at this moment) must be TWICE as effective to give the craft some semblance of positive lift when say a motor/rotor fails, as losing 50% of your lifting/flying power must result in a dramatic loss of height and quickly (forgetting the awful torque effects as I have brought up several times!).

jlawren3: If one rotor were allowed to become free-wheeling, then the torque from the working rotor would spin the fuselage. No, both rotors must always be driven.

The question has been asked before, but only completely unsatisfactory or no answer has resulted. This is obviously another aspect of the design that has not been addressed in any proper manner......one of many I feel.....

jlawren3: I have often not been able to provide prompt responses… Sorry!

Also none of the answers given to questions, "Dovetail" in with any of the other answers given either, as they have and MUST do for an aircraft to fly and fly safely.....for example an answer today may refute completely an answer of yesterday.......

The safety airbag idea from the OP is also useless as dropping out of the air at probably several hundreds of MPH and expecting such a bag to gently enough slow up the human body within the few meters of its thickness is simply another demonstration of the OPs TOTAL lack of knowledge of any basic engineering principles.

jlawren3: Hey! Watch what you are saying. I may be listening!

The bag (I do not think that this idea has ANY REAL validity) may need to have a diameter of at least (guessing!) at least 50 meters (25 meters to the center/radius, therefore 25 meters to go from say 200mph to 0 mph, and the humans would still be needed to be cocooned in an "all over" body suit to stop their heads being pulled off by the possible resulting deceleration streses.......This must be considered if say you were flying at say 50 meters high and then you crossed the grand canyon for example...........

jlawren3: I think that I was suggesting the surrounding air bag idea for small craft such as might shuttle mail from a post office to the top of tall buildings in a large city.

Seriously, having been watching this blog for some weeks now, I am of the opinion that either the OP is an out and out scammer looking for a $500,000 grant from somebody (according to one of his websites) or he has severe personality disorders that preclude him understanding reality and engineering principles.....I guess I will have to wait and see which it is....

At least he is keeping us all off the streets!!!

jlawren3: And I am hoping that people's responses might show up some things that I have not thought about. By the way, that $500,000 grant looks further off now than when I wrote that.

· #193 "Re: A New & Efficient High-Speed Rotor craft" by 34point5 on 11/14/2011 10:58 AM

11/14/2011 10:58 AM

My comment/s are in the horizontal flight context, where [according to the OP] gravity is resisted by the drag of the two down-going blades [and enhanced by the drag of the two up-going blades]

But, yes, one could regard the center of drag as at 0.707r. So as I'd guess 2000 kg MTO would require around a 6 m rotor Ø [pair]. So this point is at about 2.1m r and exerting say 1.2 times 1000 kg [drag↓ - drag↑]

As only about 30⁰ of arc is effective; in a 4 blade design, there is a dwell of 30⁰ until the next enters the effective zone, so say, being generous, we only need twice 1200 kg to meet average lift.

jlawren3: I hope that with four blades per rotor a fairly uniform lift can be obtained. When the rotor blades on a given rotor are at 45 degree angles, then each rotor blade needs to produce only half the lift it did when it was horizontal. That should not be too hard. Its effective length is 70.7% of what it was when it was horizontal.

Thing is, this is a substantially stalled, or fully stalled aerofoil, or basically 'flat' to the air-stream. This presents an interesting moment of inertia and torsional stiffness problem for the blade designer. Rather like a non-tapered wing with all the lift outboard, suffering a high-speed stall.

jlawren3: I certainly hope that in normal operation the rotor blades will not be operating in a stalled state.

I suppose the 'plus' is the rotor is going to be going like the clappers to generate 2400 kg of drag out of the last third of about a 300 mm wide 'paddle' - so some tension will be present.

Not too sure how that helps with the massive shedding turbulence however.

#202 masu 11/14/2011

"My comment/s are in the horizontal flight context, where [according to the OP] gravity is resisted by the drag of the two down-going blades [and enhanced by the drag of the two up-going blades]"

That's not the way I read his description. I think the way he sees it working is that the blades will be angled so that the forward motion of the craft is sufficient for the four horizontal blades to supply enough lift the keep the craft airborne. He's then adjusting the pitch on the rotors to allow for the rotational vector which he believes will be relatively small or about 10% of the forward airspeed so that the aerofoils see the correct angle of attack to the relative motion of the air. He's also using this adjusted angle of attack to produce the thrust needed to move the craft forward.

jlawren3: This sounds OK to me.

However, I believe he has made to fundamental mistakes:

• Firstly he has grossly underestimated the rotational speed of the rotors and therefore the angle required for them to see a workable relative angle of attack. This would then substantially change the angle of the lift created by the blades and require an unrealistic angle of attack to support the craft's weight.
• Secondly you can only adjust the pitch of the rotor to achieve the correct angle of attack at one particular radius on the rotor. This is because further out the rotational speed component will be greater and close in lower.

jlawren3: No I don't think that I have grossly underestimated the rotational speed of the rotors. I may have said this elsewhere, but I am using programs in BASIC written by Ray Prouty who does good work. Of course, I get to choose the values that go into these programs. Of late I have been thinking that a gear shift is needed to permit a higher rotor speed for transition and a lower rotor speed for cruise.

You're still not answering the critical questions that I've posted twice now so I'll post them yet again.

Please I need to know the following

• Anticipated all up mass of your aircraft
• Length of each of the symmetrical aerofoils
• Profile of each of the symmetrical aerofoils
• Cruising speed

Without this critical and basic information that is absolutely no way of knowing whether your aircraft will be able to get off the ground let alone fly horizontally.

I explored that 'read' fairly early, but he seemed to insist on the 'downward blade drag' providing the lift when 'horizontal.

I'm open to the idea that there will be some 'body lift', but given a helicopter only uses a few degrees of 'nose down' disc vector to produce its ~100 knots forward speed, [most power being for lift]. Too much tilt is known as a dive.

So, I really can't see that 'collective approach' as transitioning past maybe 30⁰ from disc axis vertical

Perhaps 'massive power' is the answer, but I don't think he realizes a rotor disc has bugger-all lateral resistance.

But so far, all other lift [and stability] solutions have been firmly rejected.

Maybe he needs rotors with big 'winglets'?

I think this is the way that jlawren3 believes his TiltPlane will work. To explain it I have drawn up the following diagram that represents the front rotor in horizontal flight in three positions BLUE, RED and GREEN with the direction of rotation shown by the PURPLE arrow.

Now when the rotors are in the BLUE position he plans to pitch the blades so that when the forward motion and rotary motion of the blades are added together the resultant lift will be in the direction of the BLEUE arrowheads on the Front View while on the side view the thrust will be in the direction of the BLUE arrowheads. The vertical blades are feathered and create no lift or thrust

When the rotors are in the GREEN position the same thing happens, the blades are pitched so that the resultant lift is shown by the GREEN arrowheads on the forward view while the thrust is shown by the GREEN arrowheads on the side view.

Finally we have the RED position and the same thing, the RED arrowheads on the forward view show the lift and the RED arrowheads on the side view show the thrust.

Now the question becomes:

Is it possible to pitch the rotor blades so that the required lift and thrust will not only be in the right direction but will be produce enough lift to keep the aircraft airborne and enough thrust to keep it moving forward fast enough to keep it airborne.

masu,

You've got it! I think that the left illustration is a very good one!

One rotor turns one way and the other turns the other. In both cases the lift vectors would be as you have shown in your axial view diagram on the left. (It is not clear to me exactly what you are showing in your three side-view diagrams.)

I want to say this in another, but supporting way. For the cruising condition note that if the rotor blades had fixed pitches and were turning in opposite directions and if they were all making long slow spirals through the air and if their pitch angles and blade twist functions were right, then they could all be knifing through the air with no lift. If the craft were then given a small nose-up pitch angle, the lift on the rotor blades of both rotors would be as you have shown in your left diagram. Of course, I do not plan to require the craft to fly with its nose pitched up at a small angle. Exactly the same effect can be obtained with the craft's axis remaining level by giving the rotor blades suitable angles of attack as they turn.

Will you give me your permission to use your diagram on the left in my write-ups and presentations?

jlawren3

• "It is not clear to me exactly what you are showing in your three side-view diagrams."

The side views show the thrust component of the force generated by each of the aerofoils at the three positions shown on the front view.

• "Will you give me your permission to use your diagram on the left in my write-ups and presentations?"

Certainly you can use them. However, if you use this link to Send me a Personal Message with your eMail address I will send you a higher resolution copy of the diagram directly. I can also send it to you in DWG, DXF and DXB format as well. However, DO NOT post your eMail address in this discussion as it's frowned upon by the administrators and will result in the post being deleted.

"The vertical blades are feathered and create no lift or thrust"

Wait a minute, are you saying the blades are feathered while the rotor is spinning? In other words, blade pairs are suddenly feathered as they reach "vertical", then pitched back as they leave the vertical?? Surely I must be reading that incorrectly.

I may have been incorrect to use the word "feathered"; I am not sure that it is an accurate word to use in this case. What I meant is only that when the rotor blades are vertical they are set so that they are aligned with the flow and produce no forces except, of course, the small drag forces caused by the flow over them.

If the rotor blades did not need to produce lift during their entire rotation they could remain at the pitch angles they were at when they were vertical. Then either the craft would have to operate with a small nose-up angle or, if the craft axis needed to remain level, the rotor blades would need to be given suitable pitch angles when they are level.

The pitch angle of a lifting wing does not need to change very much for the lift to go from no-lift to a reasonable amount of lift. Either a wobble-plate mechanism as is used in helicopters can be used to implement this cyclic lift or the rotor blade pitch angles can be driven by fast servo motors.

That's been my reading of it from the start - continuously variable pitch blades....

I assumed some sort of cam mechanism so the transitions are smooth and in proportion to the angle of rotation (of the rotor). I'm not sure if this is

• cheaper to produce than lifting "features"
• can be made to fail safe
• meets FAA/CAA requirements

I wonder how long the bearing face would last, service intervals, inspection timings and methods...

I think that I have mentioned this before. A toy was made that consisted of a stick with propellers at each end and a rubber band between the two propellers. One would hold one propeller and wind up the rubber band using the other propeller and then "launch" the craft by tossing it in the direction it wanted to go. It would fly fast, but not very long because the rubber band would become unwound. These simple "flying machines" were prototypes of my craft. I have added cyclic and collective pitch to the rotors and an enclosed fuselage, but these elements remain: two propellers, one at each end of the craft, turn in opposite directions and propel the craft in the direction of the axis of the craft.

English Rose,

Your points are well taken. I expect that early implementations will not be passenger-carrying for reasons you mention as well as others. I suggest that the first implementations will most likely be small unmanned craft. In case such a craft failed in flight I have suggested that it would explode airbags which would engulf the fuselage and the rotors and the craft would then float slowly to the ground.

But, after years of experience with such small craft, someone might begin to build tiltplanes in passenger-carrying sizes. But I wouldn't hold my breath until that happens!

So how are you going to vary the pitch of the rotors?

Have you read the comments on why airbags will not cause the aircraft to "float to the ground"?

I'd be very grateful if you would stop copying and pasting chunks of already posted material, and instead answer the points that have been raised.

masu has posted 4, I'm posting 2 here....so, a half dozen answers tomorrow?

Helicopters use a swash plate (also called a wobble plate) to vary rotor blade collective pitch and cyclic pitch. (Collective pitch is the average pitch of the blades in a rotor and cyclic pitch permits fore-and-aft pitch changes as well as left-and-right pitch changes as a rotor turns.) Each rotor of a tiltplane would also be designed to also implement collective pitch and cyclic pitch. I expect that you can look up "helicopter swash plate" and find explanations about how this works.

Alternatively, each rotor blade's pitch angle could be independently controlled by its own servo motor drive. In that case computing would need to be implemented for each rotor blade to determine the ideal value for the pitch angle for that rotor blade; this computing would take into account where each rotor blade was in the rotor's rotation and its commanded values of cyclic and collective pitch. Each rotor blade would be positioned continuously to the computed angle by its own servo motor drive.

If anyone has sent in a question and I did not answer it, then please send it in again. I have answered all the questions that I am aware of, but it is very likely that I have missed some.

from post #177

"Has Ray got a hp for 'weight' number?"

Masu may have asked this earlier, but certainly has asked about weight several times since, along with other numbers - none of which have been provided.

I think what you need to do is read all of all the posts, not just the bits and pieces you think support your current patent embodyment.

Perhaps this would help you realize there people here who can help you, if you equip them to do so.

"If anyone has sent in a question and I did not answer it, then please send it in again. I have answered all the questions that I am aware of, but it is very likely that I have missed some."

I've asked for the following information several times now and you haven't been forthcoming yet. Please, this information is critical into calculating whether your craft will even get off the ground and it's information you should have prior to even thinking about filing patents etcetera.

So I ask again, can you please supply us with the following information.

• Anticipated all up mass of your aircraft
• Length of each of the symmetrical aerofoils
• Profile of each of the symmetrical aerofoils
• Cruising speed in horizontal flight

I believe (not certain!) the technical term is "swash plate", a helicopter uses this feature to allow it to select the direction of flight.

The blades on one side are driven at a different angle to the other.....

Ta! Aeros not my field, so it's nice to know I got the principle, if not the embodiment! I had a feeling that it wouldn't be that simple!

An overview of a helicopter embodiment.

Obviously, for a very large hub (or large 'hollow shaft' entry/exit and ejecting payload) one would need to rethink a number of aspects; like avoiding bearing weight and rpm limits.

It's the sort of thing that is easy to say, but actually engineering it can be a bit tricky.

Yes, I have wondered about the bearings for the rotors. Obviously they need to be as light as possible. Here are some preliminary figures if anybody wants to think about this problem.

Fuselage dia = 4.919 ft. Rotor dia = 18 ft. Rotor speed = 450 RPM

Craft weight = 2300 lbs.

Equal and opposite driving torques would be applied to the two rotors, of course. I think that as much as 545 HP may be needed to propel the craft at 300 Knots at 6000 ft. altitude, so rotor torques can be worked out from that number.

The rotor hub diameters are slightly less than 4.919 ft. because the fuselage is tear-drop shaped. (The rotors are positioned along the fuselage at about 1/4 and 3/4s of the fuselage length.)

The rotor hubs need to have open centers. Let's say that the rotor hubs would turn about cylindrical stationary centers which are 3.0 ft. in diameter and 1.5 ft. long.

The rotor hubs will be loaded radially when the craft is flying horizontally and axially when the craft is hovering, and with some mixture during transition. The craft's weight would generally be shared equally between the two rotors.

The bearings for the rotor hubs will need to accommodate the aerodynamic loads on the rotors as well as the reaction forces from the gear drives to the two rotors, but I have only thought about that in a very preliminary way. I would guess that there might be a 10:1 gear reduction between a pinion gear driving each rotor and a large gear mounted on each rotor hub.

I expect that there will be four rotor blades per rotor and that, for preliminary calculations, the rotor blades can be assumed to be applying constant lift forces and moments to their hubs. The resultant forces will be passed on to the 3.0 ft. diameter stationary rotor centers.

A significant part of the craft's weight of 2300 pounds will probably be used up by the rotor hubs, bearings, and gears which are needed to support the rotor blades and to drive the two rotors.

I hope that this explanation is clear enough to work on this problem.

jlawren3

You still haven't supplied us with the aerofoil profiles which is critical to calculating the airspeed needed to create the required lift.

I suppose I could have a guess at the aerofoil profile but that's what it would be a guess.

Anyway, I have run out of time for the moment as I have to go into hospital tomorrow and won't have my computer with me for the first couple of days. After that I see if I can work out how big the aerofoils are going to need to be to lift the craft.

Catch you all in a few days,

masu

Stay healthy, see you soon.

Thanks mate, I'll catch you all in a couple of days or so.

masu,

My wife and I will pray daily for your healing and for the resolution of whatever problem you are experiencing.

jlawren3