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Thread: A New VTOL Aircraft Concept

  1. #1
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    Smile A New VTOL Aircraft Concept

    Hi All,

    I have a new VTOL aircraft concept that offers vertical takeoff with a similar rotor disc loading to helicopters but a high speed cruise to about 400 MPH, if enough power is installed to reach that speed. Please see Welcome to Tiltplane.com | New VTOL Concept.

    In the hover mode the speed of the rotors relative to the air will be a lot higher than the takeoff speed of most fixed-wing aircraft, so the area of the rotor blades can easily be a lot less than the area of the wings and control surfaces of fixed-wing airplanes, which means, in turn, that the cruise efficiency should be very good. In one design I was looking at I was getting an L/D ratio of 19:1 at about 200 MPH. The L/D ratio for helicopters is much lower, ranging from 7:1 to 9:1 and high top speeds are very difficult to achieve.

    There are a couple of important issues about the tiltplane approach:
    (1) The axis of the craft tilts from vertical when the craft is hovering to horizontal when the craft is flying. If it carries people, they would probably be carried in a compartment which somehow remains upright - which will require significant structure to implement.
    (2) The craft has two powered, counter-rotating rotors turning about the axis of the craft with one rotor located at about 1/4 of the length of the fuselage from the nose and the other at about 3/4s of the length of the fuselage from the nose. It is mechanically awkward that two powered rotors are needed and that they are separated by so large a distance.

    But there should be many unmanned applications for tiltplanes where (1) and (2) above are not significant obstacles and where the high cruise efficiency and high top speed are very valuable.

    Questions or comments?

    John Lawrence

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    Registered User deskpilot's Avatar
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    Re: A New VTOL Aircraft Concept

    Fanciful, but I like it. God help the passenger's if one rotor stops. Great video presentation though.
    Fly safe.

    Cheers, Doug

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    Re: A New VTOL Aircraft Concept

    Pondering the ramifications of whirl mode resonance and this layout makes my brain hurt.
    Conventional wisdom and practices yield conventional results. If that is good enough for you:
    Problem solved.

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    Re: A New VTOL Aircraft Concept

    I"d be interested in learning more about how you deal with failure modes.

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    Re: A New VTOL Aircraft Concept

    Hot Wings,

    Please fill me in on "whirl mode resonance". The only issue I see is that individual aft rotor blades will run through the disturbances in the air created by the forward rotor blades. I think that a "smart" control system should be able to learn to compensate for this and obtain fairly constant lift and thrust from the aft rotor.

    deskpilot,

    Yes, the craft is fully dependent on all the blades on both rotors fully working all the time. But this is true of helicopters also. I guess I do agree with your concern though. That is one reason that I tend to think that early applications will probably be unmanned ones. Another reason is that it is complicated to keep the passengers upright when the craft tilts.

    jhausch,

    As noted above it will probably not be possible for the craft to survive without the rotor drives working and the rotor blade angle drives working. I see no way around that. But brushless electric drives are very reliable, so I don't see a serious reliability issue with the rotor and blade drives.


    jlawren3

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    Super Moderator orion's Avatar
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    Re: A New VTOL Aircraft Concept

    The Convair Pogo, although functional, never became operational due to the inherent operational limitations. This configuration in a manned version would most likely suffer from the same issues. It is also unlikely that any airport or public facility would allow this to operate within its boundary (manned or unmanned) due to liability issues (the low blades could potentially prove to be a hazard to ground personnel).

    A similar UAV configuration (Bombardier Guardian) was selected for extended Navy trials but eventually failed due to continuing system failures. Not sure however whether those were due to the drive system or electronics.
    "To live is to learn; to learn is to live" (author unknown)

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    Re: A New VTOL Aircraft Concept

    Quote Originally Posted by jlawren3 View Post
    Hot Wings,

    Please fill me in on "whirl mode resonance".
    I'm afraid I'm not qualified to do so, thus the "brain hurt" part. I've seen it a few times and understand the basics of how it's created but I do not have enough understanding to explain it, other than to say it's a resonance mode that appears at 90 degrees to the force due to gyroscopic precision.

    A quick Google should turn up some better explanations and examples.

    Once you see it you will likely recognize it right away, and never forget it. Visualize a child's top as it spins down and starts to wobble.
    Conventional wisdom and practices yield conventional results. If that is good enough for you:
    Problem solved.

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    Re: A New VTOL Aircraft Concept

    Orion,

    The Pogo was a tail-sitter with large counter-rotating props up front and fairly conventional delta wings. It did take off vertically and fly horizontally, like my craft, but that seems to me to be the extent of the similarities. My concept has no conventional wings or control surfaces.

    Now the Bombardier Guardian is very similar to my concept but my rotors are axially spaced apart where the Guardian's rotors are axially close together. Also the Guardian was not designed to tilt over and fly with its axis horizontal. It is amazing to me that the designers of the Guardian did not go to the next step and make their craft tilt over and fly horizontally. I am glad, of course, that they didn't.

    I'll admit that there is a pretty high level of complexity involved with tiltplanes. But the level of complexity should not be much different from the level of complexity in a dual rotor helicopter. I am assuming in this statement that both rotors in a dual rotor helicopter can implement both cyclic and collective pitch.

    Hot Wings,

    I will be on the lookout for "whirl mode resonance". This is the kind of thing that makes new development work hard - the possibility of serious and totally unexpected problems. Thanks.

    jlawren3

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    Registered User D Hillberg's Avatar
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    Re: A New VTOL Aircraft Concept

    As the prop/rotors hit transonic flow and the howling starts,the pilot will barf,long before the funky landing profile and that engine failure, or the pylon whirl, or the crud blown around with a high disk loading that will negate all posability of autorotation let alone a take off with those little spindly bug legs. Look into history before reinventing the wheel.
    Manticore likes this.

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    Re: A New VTOL Aircraft Concept

    Dr Hillberg, reinventing the wheel would be stupid wouldn't it? because we already have it! If you know history so well show it then, instead of giving this comment!
    Sometimes the "invention" is in the details, and this one might be slightly different from what we have seen before. SHOW IT!
    Sacha

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    Registered User D Hillberg's Avatar
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    Re: A New VTOL Aircraft Concept

    I have seen the meny variations of a personal vehicle that has high disk loadings and a poor pilot that must endure transition from normal attitudes to God knows what,Its like the Mollar skycar ,Puffin & others with that "Next big breakthrough" B.S. Designers now use "Computer control" to make up for junk engineering. Ryan, Mcdonnal,MBB, and other designs with multi million dollar research have been there done that, And no matter how the machine is designed the pilot & people that have to live with the designers dreams are just that people. It bad enough with failure modes in machines today.Let alone certification with the local FSDO.

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    Re: A New VTOL Aircraft Concept

    eom
    Last edited by ClippedCub; April 16th, 2012 at 09:45 AM.

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    Registered User Dan Thomas's Avatar
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    Re: A New VTOL Aircraft Concept

    Such machines require enormous power-to-weight ratios. Small rotors are really inefficient, for one thing, and in forward flight their tips have to be kept well below the speed of sound or the noise and drag both become unacceptable. The tip speed might be OK in the hover, but at 400 MPH they'll be much higher.

    Moller's, like all the other attempts, suffer the multiple drawbacks of high power and fuel consumption, noise, mechanical complexity, control and stability issues, and really appalling failure scenarios. This "new" idea would not be amenable to a BRS 'chute or anything like it, with props at both ends. And it sure isn't going to autorotate. It will, however, eat lots of money from gullible folks, perhaps stimulating the economy.

    Dan

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    Re: A New VTOL Aircraft Concept

    Hi Dan,

    Tiltplanes won't need to have unusually high power-to-weight ratios or unusually high rotor disc loadings; they will be similar to helicopters in these two respects.

    Yes, there are lots of poor ideas out there, but I don't think that the tiltplane concept is one of them. Here are two significant advantages of tiltplanes:

    1) They combine VTOL capability with high cruise efficiency. One design I worked through using programs in BASIC written for me by Ray Prouty had a LIFT/DRAG ratio of 19:1 at a speed of 200 MPH. Helicopters have LIFT/DRAG ratios ranging for 7:1 to 9:1.

    2) Unlike helicopters, when tiltplanes will be inherently highly maneuverable in all their flight modes. For example, a tiltplane when hovering can immediately command forces and moments in all six degrees of freedom whereas a conventional helicopter with a single main rotor must first tilt its main rotor before it can generate any horizontal forces.

    Hi ClippedCub,

    You are right, flying tiltplanes without fully automatic controls would be very difficult. I expect that the pilot would mainly tell the craft where to go, how fast, and what peak altitude to reach while automatic systems would carry out his commands while also avoiding other aircraft.

    Hi D Hillberg,

    Well, given past history, what should one's attitude be? I maintain that this idea is new and very promising. Even if there have been 100 bad VTOL aircraft ideas proposed in the past that does not mean that there cannot still be at least one good new idea which has not yet been explored.

    jlawren3

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    Re: A New VTOL Aircraft Concept

    One thing I'm missing in the discussion is the Coanda effect. Use it as a "force multiplier" to get a large lift force with a relatively small prop/rotor area. Works surprisingly well
    Kennis vermenigvuldig je door het te delen.
    (You multiply knowledge by dividing it)

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