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  • Manned Quad-Copters

    I feel a new topic for general coverage of full sized manned multi-rotor aircraft is more appropriate than placing them under the banner of "DFC Rotor Heads".
    I also acknowledge many readers and members have devoted much time and effort in the pursuit of electric powered multi-copters and drones however at this time their uses are limited through power and scaling up problems which are of little consequence in the smaller versions.
    Many are only interesting novelties at this point of time and IN MY OPINION serve little or no practicality in aviation today apart from perhaps ongoing research/hobby.
    Manned quad-copters have been around since the early days of controlled manned flight with varying degrees of success and in particular one such machine stands above the rest so for those interested/inspired rotor heads I have included the following link.

    https://maquettes-missiles.blogspot....quadrotor.html

    Looks like French to me however Google translate gives good results

  • #2
    I don't know about y'all, but I have about all I can do dealing with one swash plate, with one underslung, coned two bladed rotor. Multiply that by some integer probably bigger than 2 with the vibrations associated with each rotor, the controls needed to get all of them to agree on the direction of flight, Hell!! just balance and track all of them.
    To get interested in a multi rotor ship it would have to a craft that looked goo, and would fly 200mph on 5gph and carry twice its weight.

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    • #3
      This Translated version may help!
      This is an incomplete section of the full report and the Google translation requires a bit of guesswork!
      Attached Files
      Last edited by Rotorcycle; 11-13-2017, 11:33 PM.

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      • #4
        Around the time I first joined PRA in 1969, there was a story in the magazine about the Aerotechnik. It was a prototype of a German quad-copter using a BMW motorcycle engine. There were no pictures of it in free flight and no followup.

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        • #5
          I saw a number of photographs of the Aerotechnik and some brief info but no photo's of it in any form of flight. It apparently used rotating booms for directional control.
          Both it and the convertawing had the CG well below the rotor tip path planes which would produce a dynamically stable aircraft and not the optimum for maneuvers.
          It appears the CG should not be lower than the disk path plane and if possible it should be slightly above the tip path planes. Check the CG of jet powered "Fly-board" or the Williams Wasp. Sure no rotors but similar effect.
          Last edited by Rotorcycle; 11-16-2017, 08:52 PM.

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          • #6
            Hmm. A human standing on his/her two feet is a statically unstable* system, with a CG 2-3 feet above the point of support. We all would fall over if we did not continually make small corrections through our legs and feet. This becomes a reflex at the time we first learn to stand, and we usually think nothing of it for most of the rest of our lives. In old age, the correction mechanism tends to break down, and falls become likely for many. Even for healthy people, standing up involves a considerable workload. It's a lot more restful to lie down (to move our personal CG down near the point of support).

            Flying-platform aircraft are feasible, even though they are statically unstable with a high CG, because they employ our everyday human balance system -- a system that actively stabilizes an otherwise unstable system.

            The Aerotechnik, de Bothezat quad-copter and similar purely mechanical multi-rotor helos did not use any stability augmentation system (SAS). Therefore, CG below the rotors was pretty necessary to create even a reasonably stable machine.

            An alternative, I suppose, is to build an unstable machine and train the pilot exhaustively to act as a continuous, human SAS. Humans are remarkably trainable critters; even a kid's bicycle is statically unstable, but we learn to stabilize it continually, using small steering inputs, only a few years after learning to stand up. (This fact is the real basis of the endless argument that unstable gyros are OK with enough training.)

            Another alternative, and a frequent one in "edgy" designs, is electronic SAS on a statically unstable platform. Some of us "pre-millenials" don't take much comfort in such things, at least for civilian and personal use. God forbid a nearby lightning strike.
            ___________________________
            * "Static" and "dynamic" instability are often confused. A statically-unstable system is one that will diverge continuously in one direction (such as by falling over) when disturbed. A dynamically-unstable system is one that is statically STABLE, but lacks damping. As a result, a dynamically unstable system is one that will diverge in ever-increasing oscillations when disturbed.

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            • #7
              The subject of stability is long and complex especially when you consider human responses to effects of forces. If I close my eyes and turn deaf for a few moments and the pilot in command places the aircraft in a steep climbing attitude do I feel the pressure of the seat increasing against my back as an indication of the aircraft climbing or the aircraft accelerating in a powered steep descent?
              Instruments are necessary when flying on a dark night with no reference to the ground. The human sense's without the combination of sight are totally unreliable and also, the aircraft is still being controlled manually through what the pilot sees on his panel. Sight is disconnected from the other senses.
              It appears a normal person can be "trained" within the space of a very short time to control a Quad-Copter to perform how the pilot wants and not how the machine wants, within reason of cause.
              A multi rotor is unlike a single rotor Heli/Gyro and does not necessarily emulate a ball on a string acting as a pendulum .
              Take for example a Hughes 500 V Robinson R44 and the associated mast heights. The 500 rotor head is barely above the fuselage top where the R44 has a very tall mast.
              I, like others prefer flying the nimble Hughes anytime compared to the R44.
              The extra power and control input to overcome "stability" also comes to mind.
              Check the YouTube clip of the "Convertawing" performing a quick-stop, very wobbly and "unstable".
              For every action there is an equal and opposite reaction.
              I'm also one of those "per-millennial's"!

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