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  • Granted, the pitch dynamics will work with moving the mass around, there are still two concerns for this kind of aircraft. First of all you are still going to have issues with a fixed coupling between the yaw and roll axis control authority. If you speed of one rotor and slow the other rotor to yaw the aircraft, this will create a rolling moment. In order to counter this, you can rotate both rotors independently, but you will greatly complicate the servo mechanisms. While this may be fine for small versions, you will run into issues with scaling this design. The only other way to do this is to have collective control, but this also complicates the design.

    Secondly the whole moving the mass concept will work (by the way, they have been using this concept for unmanned underwater vehicles for years), but you will eat up a lot of fuselage space that could be used for carrying payloads. Also I think you will use less energy and more control authority using additional rotors for roll authority (like quad planes) than to constantly have to accelerate a fixed mass, but this will vary by case.

    In short I definitely think its a cool design, but I don't think this is the "best all around design" for VTOL applications, especially for carrying payloads (Designing Aerospace vehicles in general is always a compromise, thus there is never going to be a ideal universal design, period). Just my two cents...

  • Sam Worthington said:

    I'm a little puzzled by your weight vector during transition? Why does it point backwards?


    This is the force results from m x  g and the horizontal component m x a. Apologies  for not using the proper newtonean terms in that sketch. Although the point I think is still clear. 

  • I'm a little puzzled by your weight vector during transition? Why does it point backwards?


  • As this - admittedly aggressive - approach obviously raises passions and strong views - to say the least let me share how I solved some of the problems associated with "conventional" VTOL aircraft.

    Rest assured that "sketch" is NOT ALL I have - I also did the maths... ;-)

    I identified the true issues that come with dualcopters as follows:


    The problem is the pitch axis...


    While Yaw-/Roll-axes have very good control authority due to the fact that they can be influenced directly via effectively changing vector directions and/or values. Pitch-axis authority varied a lot with available mass/arm but proved insufficient in many (attitude control-) cases as it only tilted the rotor disks relative to a given CG. The interaction of rotor disk inertia with a given control input is what caused many less than elegant outcomes.


    While these difficulties can (more ore less) be contained by the use of a well tuned PID-controller there is the remaining problem of pitch stability during a transition state when both rotor disks are tilted forward to accelerate longitudinally, causing the CG to veer away from the axis of thrust causing  pitch momentum.

    With this system the CG can counteract all pitch axis momentums - or create desired ones - through all flight phases never loosing the ability to place precise and highly dynamic control inputs on the pitch axis. In other words: NO MORE DISCRETE STATES!!!3702315104?profile=original

     Instead of heading down the road of cyclic pitch I decided to introduce an additional control dimension – Dynamic Mass actuation (longitudinally) in combination with a unique Flap system allowing smooth transitions.


    This system works in 3 ways:

    1.   Static momentum free state can be maintained (if desired)
    2.   Dynamic impulse helps to stabilise immediately (reaction force caused by acceleration of the mass)
    3.   Increase of moment of inertia as mass moves away from instantaneous centre of rotation


    Additionally the rotor disc actuators which are no longer involved in maintaining stability around the transversal axis have a greatly reduced workload and right from the beginning the entire system appeared less critical during my tests:

  • surface controls will be strong at root, week at wing joint.  Dynamic moving mass, this means you are using a change of center of gravity to maneuver the aircraft, which means you need mass to do so.  This is counter to lighter the aircraft the longer it flies.  You have enormous moving parts.  The weakness in this is hidden because you are using computer graphics to make the concept, but in real life moving those parts is a real problems.  It will become more difficult when you scale up the aircraft as well.  The motors being inside the wing might work partly, but you will loose lift from the wings due to the "cut out" section that this concept must have in order to fit the props through. 

    Are you sure you can move that mass FAST enough to effect a control over the aircraft similar if not better than a conventionally control aircraft?

    Where are you going to put the fuel at?  If in the wings can you fit enough in them to be effective?  If in the body how are you going to wire the power (if electric) to he motors, or if it is fuel, how are you going to pipe the fuel from the fuselage to the engines when the body slides in and out?

    The concept of a mass driven control system was born right down the street from where I live (University of Texas at Arlington) or at least, that's the only place I have heard of this.  It won some award.  Bottom line is that unless the mass being used is USEFUL for something OTHER THAN flight control then it has the title of "dead weight" because conventional methods can be a flight control surface AND be part of the wing that provides lift.

    It's a neat idea that I imagine will have only limited success.  On the other hand, try making a spaceship that can use this idea given that it does not take fuel to use (crazy idea too).

    good luck!

  • How can you make any claims to capability , or number of parts?  All you have is a sketch.  And a pretty implausible one at that.  How will you control pitch?  

  • ...compared to what? - A Rock, or perhaps a V-22 Osprey!?

    No offence, but in order to compare properly I would appreciate a more consistent line of arguments!

    For example, this aircraft compares to a V-22 on the basis of it's capability - and I'm pretty sure it has considerably fewer moving parts...

  • So many more moving parts that can fail...
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