Prize Money

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by jedi, Jan 27, 2018.

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  1. Feb 27, 2018 #101

    BJC

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  2. Feb 27, 2018 #102

    mcrae0104

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    I would be careful thinking of this as analogous to wearing a set of wings and a jet. The props will have a destabilizing effect. Airplanes in flight overcome this by putting a lot of surface area aft. I'm not sure that the pilot's body (even if he wears a wing suit) will provide nearly enough of a stabilizing "tail" to provide directional stability.

    I salute your work on the engine and the general idea, but control will be every bit as important as the powerplant. You are in Wright brothers territory in terms of the type of problems that need to be overcome. Working out stability and control will prove to be a bigger challenge than designing an engine from scratch.
     
  3. Feb 27, 2018 #103

    oriol

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    The Gen H 4 (BJC´s post 101) is along the lines of the Boeing rules but still could not meet the noise level and the maximum 2,5 meters diameter since its rotors are 4 meters.

    If you reduce the rotor diameter and increase the horsepower of the GEN H 4 you can probably lift the aircraft but not the batteries, to fulfill the noise and range requirements.

    To me the GEN H 4 and Manolis tailess concepts seem unsafe at speed and prone to tumbling, particularly if adhering to the strict Boeing size rules.



    Oriol
     
    Last edited: Feb 27, 2018
  4. Feb 27, 2018 #104

    Victor Bravo

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    Guys, take a minute and think about something.

    If Boeing sponsored a prize like this, and someone actually made something that flew, and then someone got hurt... what would the result be? That's right folks, the largest lawsuit imaginable.

    But the PR people at Boeing can really make use of this competition, to make themselves look like they're supporting innovation.

    And then the legal department walks into the boardroom, foaming at the mouth, telling the publicity people that it can never happen.

    Some clever little corporate rodent says that maybe they can have the competition, but rig it so that nobody can actually create anything that will fly high enough to cause any harm.

    So they tell the engineers to come up with a set of rules that makes it 99.999% unlikely that anyone can do it.

    I'm not saying that it is totally impossible to achieve a flying machine that will meet all these parameters, but I am reminding everyone that James Doohan (Mr. Scott) has passed away.
     
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  5. Feb 27, 2018 #105

    manolis

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    Hello Mcrae0104.

    You write:
    “I would be careful thinking of this as analogous to wearing a set of wings and a jet. The props will have a destabilizing effect. Airplanes in flight overcome this by putting a lot of surface area aft. I'm not sure that the pilot's body (even if he wears a wing suit) will provide nearly enough of a stabilizing "tail" to provide directional stability.”


    The arrangement of the propellers of the Portable Flyer is absolutely symmetrical, giving an overall neutral propulsion unit; as neutral as the set of the jet-turbines of Yves Rossy’s delta wing.

    And the Delta Wing of Yves Rossy appears in the videos quite stable and controllable at high speeds.
    As Rossy says : "I am the fuselage, and the steering controls are my hands, head and legs"


    The question is whether the Portable Flyer can be similarly stable at take off and hovering.


    At take-off and hovering the stability of the Portable Flyer has reasons to be better than the stability of the GEN-H-4 of the link in the post#101 of BJC (thanks BJC)

    [​IMG]

    The GEN-H-4 has only two constant pitch contra-rotating propellers (note: the lower rotor runs at substantially different conditions than the top rotor).

    The Portable Flyer has two pairs of counter-rotating propellers, the one pair above the engines, the other pair below the engines.
    The two left propellers (upper and lower) can either contra-rotate, or rotate at the same direction; both arrangements work.
    Each pair of counter-rotating intermeshing propellers is perfectly symmetrical.
    On this reasoning, the Portabla Flyer looks totally neutral.


    Quote from http://thefutureofthings.com/5869-gen-h-4-personal-helicopter/ :

    The pilot (of the GEN-H-4) controls the helicopter’s rise and descent by pushing the throttle lever. One can choose to fly in a certain direction by simply pulling or moving the control bar in the opposite direction. In order to turn to the right or to the left, one has to push the yaw-control-switch.

    The yaw control of the GEN-H-4 () needs a differential gear within the transmission, driven by an electric motor.

    End of Quote


    For the GEN-H-4 wikipedia writes:

    “Steering is accomplished by pivoting the rotor head on a gimbal using a control handle, in a similar manner to a weight shift hang glider.

    The same is true for the Portable Flyer wherein the gimbal of the GEN-H-4 is replaced by the waist of the pilot: moving the legs, hands and head the pilot controls the flight in a similar manner to a weight shift hang glider.


    For the yaw control of the GEN-H-4 wikipedia writes:

    “Yawing motion is produced and controlled by electronic gyroscopically-controlled differential electric braking of the main rotors.”

    At hovering, the yaw control of the Portable Flyer is way simpler: the pilot being in the downstream of the propellers can use his legs / feet / hands / palms as flaps to turn about his long axis controllably.


    Thanks
    Manolis Pattakos
     
  6. Feb 27, 2018 #106

    BoKu

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    Demonstrably false. A propeller or rotor has about the same effect as the equivalent projected area perpendicular to the longitudinal axis. If it's ahead of the neutral point, it is destabilizing; if it's behind the neutral point it is stabilizing.

    This is why Unlimited air racers often need enlarged vertical stabilizers after power upgrades. The greater horsepower allows operation at coarser propeller pitch settings, which results in greater projected area of the propeller, which results in reduced pitch and yaw stability.

    --Bob K.
     
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  7. Feb 28, 2018 #107

    manolis

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    Hello BoKu

    You write:
    “A propeller or rotor has about the same effect as the equivalent projected area perpendicular to the longitudinal axis. If it's ahead of the neutral point, it is destabilizing; if it's behind the neutral point it is stabilizing.”


    The stability of the Portable Flyer at take-off and hovering is dynamic; it appears quite similar to the “dynamic” stability during walking, wherein the brain “feels” (mainly by the otoliths and the eyes) and responds by commanding the various muscles to expand or contract.

    At take-off / hovering (and during horizontal flight) the brain of the Portable Flyer pilot “feels” (otoliths, eyes, ears and skin) and responds by continuously / dynamically re-vectoring the thrust (by moving his torso – back – shoulders (whereon the engines / propellers are secured) relative to his rest body).


    With only an altimeter and timer, Rossy uses his skin and ears as airspeed indicators.
    "You feel very well, you feel the pressure," Rossy says, "you just have to wake up these senses. Inside an airplane we delegate that to instruments. So we are not awake with our body."

    As Rossy says : "I am the fuselage, and the steering controls are my hands, head and legs"



    Without zero gyroscopic rigidity, it would not be possible.


    Here is a GEN-H-4 video:



    demonstrating its stability at take-off and hovering.

    It has two constant pitch contra-rotating rotors.

    The only control is the displacement of the center of gravity of the mass under the gimbal joint relative to the above the gimbal joint structure (which comprises the four engines, the transmission and the two contra-rotating rotors).


    By combining two GEN-H-4:

    [​IMG]

    (“counter-rotating”, “intermeshing”, side by side), you get a Portable Flyer which reasonably is more stable than the single GEN-H-4.

    Do I miss something out?

    Thanks
    Manolis Pattakos
     
    Last edited by a moderator: Mar 20, 2019
  8. Feb 28, 2018 #108

    mcrae0104

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    Yes. You are missing the concept of directional stability in horizontal flight. Your proposal is not the same as Yves Rossy's method of flying. He does not fly behind a destabilizing propeller. He also has a wing, which is a very convenient way of adjusting the relative position of the CG and the aerodynamic center of a flying object. Keeping the CG in front of the aerodynamic center is the key to stability.
     
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  9. Feb 28, 2018 #109

    manolis

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    Hello Mcrae0104

    You write:
    “Keeping the CG in front of the aerodynamic center is the key to stability.”


    If you mean this:

    [​IMG]

    (more at http://www.boldmethod.com/learn-to-fly/performance/how-does-cg-affect-aircraft-performance/ )

    it concerns the longitudinal stability of fixed wing airplanes.

    With the Center of Lift (CL) aft of the Center of Gravity (CG), the airplane can recover from a stall because it starts falling nose-down gathering speed and enabling the pilot to take back the control of the flight again.


    But the Portable Flyer has nothing to do with a “fixed wing” flying device.

    The pilot by extending / retracting / re-orienting his hands, legs, palms, feet and head, is a living wing.

    At a stall, the pilot can easily go nose-down (start at the second 41 of the following video and enjoy what an “unpowered” human body is capable of; spot on the “yaw control”; see how easily the skydivers control their fall):



    Actually it is not at all an “unpowered” flight.

    With a falling speed of, say, 360Km/h (100m/sec), and an 80Kg total mass (800N weight of skydiver and parachute), the skydiver is powered by 100m/sec * 800N = 80kW (~110bhp).

    During his fall, the skydiver consumes his dynamic energy.

    The bad thing is that the skydiver soon consumes his dynamic energy and has to land with his parachute.

    With a completely neutral power unit (like the OPRE Tilting with the counter-rotating propellers) the flight of the skydiver can last for a few hours.

    Thanks
    Manolis Pattakos
     
    Last edited by a moderator: Mar 20, 2019
  10. Feb 28, 2018 #110

    mcrae0104

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    No, that is not what I mean.

    Consider an arrow or missile in flight. Its CG is ahead of its aerodynamic center because it has tail fins. If its nose rotates slightly off course (up, down or sideways), it tends to return to its original orientation because its aerodynamic center is behind its CG.

    If you were to shoot an arrow backwards, with the fins in front (AC ahead of the CG), you would find that it flies maybe a few feet before it tumbles off in some direction. When the nose gets slightly out of line with the direction of travel, the mass wants to keep going straight, making the problem worse. It does not have directional stability.

    Now imagine we could replace the arrow's fins with a small disc, maybe 2", at the rear. It would still fly generally straight although maybe not as far. Now turn the "disc arrow" around. It would not make it more than a coule of arrow lengths before it tumbled.

    A propeller is aerodynamically like that disc. When your machine is in horizontal flight, it is like an arrow with the disc at the front. Sometime, as a basic concept model, put together a balsa stck airplane with a rubber band and plastic propeller. Leave off the wings and tail. Wind it up and launch it and see what happens.

    Now you will object that you have a human in the loop to make real time adjustments. That is true, but it will not overcome directional instability. In theory, an unstable conventional airplane could still be flown because there is a pilot to guide it. However, humans are not quick enough to react. This is why computers are required to fly unstable platforms like an F-16.

    The reason why Mr. Rossy is able to lean and nudge his "airplane" in the direction he wants to fly is that it is a directionally-stable platform to begin with.

    I am not suggesting that you have a bad idea or that it will not fly--only that there is an unaddressed problem to solve. I hope you do solve it because if it works I think it would be quite an experience to fly.
     
  11. Feb 28, 2018 #111

    oriol

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    Manolis you are very talented and committed builder but regarding flying you do not seem to have much practical experience(?).


    Helicopters have a tail for a reason that includes the Kamov family as well.

    Sky divers or base jumpers stability cannot be compared to helicopter or powered aircraft stability.
    Tailess and weight shift aircrafts might be prone to tumbling which is extremely dangerous.

    You cannot base your asumptions about your concept flying qualities on videos of the GEN H 4 hovering and little else. The Boeing competition is a pylon racing circuit and many things can go bad flying at high speed and performing tight turns close to the ground.

    Manolis excuse me if I sound harsh I am just talking about safety not offense intended.


    Victor Bravo, the Boeing Prize allows the use of dummies with the equivalent weight of an average pilot during the competition.


    Oriol
     
    Last edited: Feb 28, 2018
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  12. Feb 28, 2018 #112

    manolis

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    Hello Mcrae0104

    Yyou write:
    “Consider an arrow or missile in flight. Its CG is ahead of its aerodynamic center because it has tail fins. If its nose rotates slightly off course (up, down or sideways), it tends to return to its original orientation because its aerodynamic center is behind its CG.”


    An arrow has not powered propellers at its nose.


    Thinking with arrows, let me put it differently:

    Consider that the nose of the arrow is the power unit (the two OPRE Tilting engines with the counter-rotating / contra-rotating propellers), while the pilot is the tail fins of the arrow.

    The power unit pulls the front end of the structure forwards, the aerodynamic drag pushes the rear end of the structure backwards. And this is stable.



    See also the following video:



    Power unit at front with good stability and controllability.


    You also write:
    “Now imagine we could replace the arrow's fins with a small disc, maybe 2", at the rear. It would still fly generally straight although maybe not as far. Now turn the "disc arrow" around. It would not make it more than a coule of arrow lengths before it tumbled.“


    To consider the propellers as solid disks?

    Why?

    A solid disk cannot provide thrust.

    Thanks
    Manolis Pattakos
     
    Last edited by a moderator: Mar 20, 2019
  13. Feb 28, 2018 #113

    manolis

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    Hello Oriol.

    You write:
    “Victor Bravo, the Boeing Prize allows the use of dummies with the equivalent weight of an average pilot during the competition.”

    Thanks.

    However the basic constituent of the Portable Flyer is the pilot.
    The propulsion unit (some 20Kg for 100Kg total) is a necessity.

    [​IMG]

    If you replace the pilot by a dummy of similar weight, you have nothing.

    Similarly in the jet-powered Delta Wing of Yves Rossy: Rossy is the fuselage, Rosy is the ECU, Rossy is the sensors and Rosy is the servomechanisms.


    And I think this is what GoFly / Boeing mean by their:

    Quote from https://www.herox.com/GoFly

    Today we look to the sky and say “that plane is flying.” We challenge you to create a device where we look to the sky and say, “that person is flying.
    . . .
    Our goal is the same as Da Vinci’s and children of wonder throughout the ages: Make people fly – safely and effortlessly."

    End of Quote.

    Thanks
    Manolis Pattakos
     
  14. Feb 28, 2018 #114

    pictsidhe

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    I think that some of the more amateur designers would do well to notice the fact that those with plenty of aero books on their shelves are shaking their heads at gofly.
    Dummies will be crashing, some may well be live ones.
     
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  15. Feb 28, 2018 #115

    Victor Bravo

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    If it is not necessary to have an "airframe", and if it truly is sufficient to have a pilot suspended by nothing more than a powerplant/propeller unit, then why did they need wings, tails, and control surfaces on BOTH of these aircraft ???

    300px-Lockheed_XFV-1_on_ground_bw.jpg

    avpogo_01.jpg

    Many of the best and most highly educated engineers in the world worked on these projects at TWO of the world's leading aerospace companies. Their decision to build large wings, tails and control surfaces was not an amateur oversight or miscalculation.

    If the basic principle of the Portable Flyer is valid, and if your repeated arguments and defense about the this basic operating pronciple are valid, then why did a group of highly trained engineers see a need for all the "flying surfaces" ?

    Even considering the fact that both of these aircraft were designed for eventual military purposes, they would certainly have created a smaller man-sized prototype just to demonstrate the validity of the principle.

    What did you discover or validate that the professional designers at Lockheed and Convair (now General Dynamics) were not smart enough to see?
     
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  16. Feb 28, 2018 #116

    Tiger Tim

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    From my admittedly half-assed read through the gofly rules, it seems to me the point is to explore outside the established norms. Maybe someone will come up with a scheme nobody's thought of, or maybe they'll continued to hold these things over and over with the rules relaxing little by little until something viable emerges.
     
  17. Feb 28, 2018 #117

    manolis

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    Hello Victor Bravo.

    You write:
    "Many of the best and most highly educated engineers in the world worked on these projects at TWO of the world's leading aerospace companies. Their decision to build large wings, tails and control surfaces was not an amateur oversight or miscalculation.

    If the basic principle of the Portable Flyer is valid, and if your repeated arguments and defense about the this basic operating pronciple are valid, then why did a group of highly trained engineers see a need for all the "flying surfaces" ?

    . . .

    What did you discover or validate that the professional designers at Lockheed and Convair (now General Dynamics) were not smart enough to see?"



    What the Portable Flyer claims is that:

    with less than 20Kg equipment (engines and propellers),
    and with a 20lb (9Kg) bottle of gasoline,
    a man can take off vertically,
    and hover,
    and fly horizontally at ~100kts,
    and go 200 miles away,
    and land vertically and safely.


    [​IMG]

    Thanks
    Manolis Pattakos
     
  18. Feb 28, 2018 #118

    pictsidhe

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  19. Feb 28, 2018 #119

    pictsidhe

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    Manolis. I had a gofly idea. I did two sets of calculations to check its viability. (I find that doing the maths twice reduces the overall project time by catching errors sooner).
    They gave wildly different answers. After failing to work out which was wrong, I built a cardboard test experiment. Pessimism won that day...
    I suggest that you get a doll, some rc propulsion, get the cg where you think it will be and try to get it to fly straight, and prove us sceptics wrong. This could save you a ton of work and maybe your neck too.
     
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  20. Feb 28, 2018 #120

    Victor Bravo

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    I have not called into question, or agreed/disagreed with any of the things that you have listed above.

    My question was NOT about any of those claims, my question was specific and clear, and I'll ask it again: How do you explain the fact that a large group of very highly trained engineers looked at this problem (propeller thrust-operated VTOL within a small size restriction), and clearly saw the need for flying surfaces, wings, tails, control surfaces, etc. ?
     

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