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Passive attitude control (PAC)
passive attitude adjustment capability
Folder and studies in PAC in honor of Wayne German's vision*.  

  • Undamped pendulum
  • Damped pendulum
  • Slanting the base axis of a rotating set of wings to the desired attitude.
  • Bungy incorporation into extensible tethers for wind spilling.
  • Helicopter swashplate
  • Liquid slosh
  • Small loading of springs in cycles that get triggered upon slosh or pendulum or other built-up tension or compression
  • Flow logic over surfaces
  • Stack 'em up and what do you have?
    • Yes, stacking is one avenue to attain passive attitude control. Other methods are invited.

      Pausing on the stacking realm:
      Invited are studies of passive attitude control of stacks of wing elements
      1. for stable-positioning farm-tower marking even while having those marker towers working rope drives for production of useful energy.
      2. for dynamic crosswinding
      3. for self-limiting strain during facing winds beyond design limits
The pendulum topic is not your strongest contribution (I like Antarctic Ice-Pack Blow-Molded Wings).

Rather than being overlooked, pendulum stability is almost universal in aircraft design. Obviously all helicopters, autogyros, trikes, paragliders, and hang gliders have inherent pendulum stability designed in. Most small aircraft are high winged, with decided pendulum stability. Ordinary single line kites require only a bit of pendulum-based yaw stability; kite pitch and roll are effectively constrained by just split bridling (triple bridle). Even low-wing aircraft are actually pendulum-mass stabilized, the dihedral angle selects whichever is the lower wing to act as a pendulum rod. Only extreme aerobatic designs deliberately avoid pendulum stability.

That is, until now: Our latest kite energy arrays, "staked-out" crosswind, simply have no need for any pendulum mass/moment for attitude control. Each kite sail in a dense array is constrained stably by the lattice. The pure "rag and string" school has triumphed over ordinary instability and especially pendulum uncertainty and mass requirement. No more chaotic flying pendulums run amok. Its really a revolution over the dependence existing aviation has on pendulum stability.

Consider how simply anchoring across the wind is the most inherently stable basis for "crosswind power" harvesting,

Subject: Re: Pendulums or Gondolas as pendulums for Passive Attitude Control
Dave and friends,
What I wrote was really a simplicity to say the heart of the matter without disclosing all details. Actually, pendulums were suggested early on in aeronautics but they were rejected when it became evident that aircraft were making accelerations of their own that swamped out the accelerations due to gravity. Even so, I am told that one aircraft successfully flew by using a pendulum for attitude control. That is because it was designed to always fly on a steady course and not generate accelerations of its own. But the point you make Dave is right, pendulums can benefit from damping and I should have pointed out that such damping can easily be achieved in this design simply by making the shaft that connects the wings with the pendulum/gondola as long as designed -- increasing the length of the shaft increases the amount of damping -- at the cost of some extra wind drag. If the shaft is too long then the craft would act like it is in "leg irons" in that it would too greatly resist intended changes in direction -- unless the angle of the shaft/pendulum/gondola with respect to the wings is what would determine the pitch and roll over-all of this tethered craft -- hopefully tethered to a submerged hydrofoil for the fastest sailing possible.

Actually Dave, I had no thought of who might "own" the concept of using a pendulum to achieve such simple Passive Attitude Control. I never thought of claiming it as my own idea though looking back I can see where you might have thought that I was claiming it as my own. But now that you mention it, I know, as I mentioned that pendulums were suggested early on for aircraft in general -- and shortly abandoned in general. But I did not know of anyone else suggesting them as perhaps the one simple device that would enable kites in general to attain much more of the stability of airplanes in general -- and therefore able to due useful and reliable work as a result of it. Also, at Chico I presented one model of this pendulum kite to you and the other to Dave Culp. I do not think that Dave ever realized what it was that I gave him. I think that is the method that he could use to obtain the stability that would make his ship propulsion kites possible in the simplest way.

But again, if you thought that I was claiming the most fundamental uses of pendulums myself in aeronautics then I apologize and should be more cognizant of what I intend to say, but also what other people might reasonably hear as well. But the question really is Dave (and friends): if it is true that pendulums could so easily and simply stabilize kites shouldn't our fraternity consider them as a normal and expected part of tethered craft unless a more sophisticated method of attitude control is used instead? Frankly, I think this point, that I made at Chico also, is that pendulums may provide a simple and direct method of stabilizing kites that most everyone has overlooked in our fraternity. I would appreciate kind discussion by all of you regarding this matter and I am inviting Dave Lang, as "Mr. Tether" to comment also -- as he knows much about tethered systems.
    -- Wayne German

While you are right to count on pendulum-stability as a useful principle, keep in mind that it is an old standard concept in aeronautical engineering (eg. high-hat wing). It does not seem possible your FRI friends did not know this. Also remember that pendulums are unstable, and "pendulum stability" is mocked by common turbulence, in any chaotic aeroelastic inertial kite event where the kite starts by swaying wildly like a swing (pendulum), then orbiting as a stable (falling) flywheel. If you will make some simple kites with a pendulum attached (just as Hargrove over a century ago), you will find just how weak dependence on (undamped) before our time seem to cover virtually every concept we think of. Name any kite idea you have ever thought totally original to you, and some close prior art can likely be shown by Joe or me. We should be glad to be humbled by such amazing predecessors.

So keep up the great real work. I think there must be a way to make a kite fly just like the falling seed heli, where the mass helps maintain rotation, thanks for that sort of insightful clue,


PS Thanks for the kind words. Culp was the name you wanted to remember.

Here is the concept 3d drawing I made in Rhino and gave to the Drachen Foundation and gave to Dr. Breidenthal from the University of Washington. Then I made models of the concept and passed them out to Dave S. and Dave ??? (I forgot his last name. He made the spinnaker that won the America's cup that year).

Suppose the first couple of feet of the tether from the kite was actually rigid. Then it would stabilize the pitch and yah of the kite. And the pendulum or gondola (which is way too big and bulky here) would stabilize the pitch and roll of the kite. So between the tether and the pendulum or gondola the kite should be stabilized in pitch, yah, and roll -- the three directions necessary to fix the attitude. Please see the picture that is attached.

-- Wayne

Dave,  I welcome your opinions as I do Joe and others. I think a free and lively interchange of ideas helps us all because we all see some things that others don't so together we can progress further than any of us could individually. And the reason I sat down to write again was to tell you that you were apparently the first who realized the potential of a "maple seed" rotating kite to maintain rotational momentum and thus lift during variable winds.

But I do not understand your comment about kites as arrays generating power cross-wind. Isn't that the whole nature of the "vertical blinds" that I discussed with you? Don't they form an array of wings that are vertically oriented -- like a stack of kites that lift sideways rather than up to spin one or more generators on the ground?

And in the event that the winds should die down the bottom of the vertical blind array could be let out faster than the top of the vertical blind array and each of the vertical blind wings that would have symmetrical cross section could be inclined somewhat to not only provide traction to make the ground based generator(s) spin but also to provide lift for the vertical blind arrays so they could fly dynamically by some of the power that they themselves would generate.

But in the event that most or all of the winds should die the generators could really be generator/motors acting as motors and some power could be used to keep the entire array aloft dynamically by pulling it back and forth across the Great Plains using power from the grid.

In all these situations the altitude that the vertical blind arrays would fly at would be a function of how fast they were lifted to the side either by the winds blowing cross wind or the power from the grid.

But Dave, it sounds like you are saying that kites for generating electrical power across great expanses should necessarily eliminate all needs and desires for simple kites to generate wind power with. How about for generating power over single farms all across Amercia!!! Surely, the large massive array power generators do not meet all needs. How about for on-board power for ships and freighters -- particularly at anchor?

But what I was really trying to say is that I am beginning to think that all kites could benefit from the Passive Attitude Control that pendulums would provide. After all, isn't that the main problem that faces all kites -- that they eventually lose control over their attitude and crash? The point is that I do not often see even your basic ordinary toy kite come down just for lack of sufficient wind. Almost always, it seems to me, that the kites get into an attitude that they cannot get out of and the kites streak to the ground and crash -- rather than just go limp and sag to the ground.

On the other hand, if you have been pursuing these objectives or promoting these objectives without including me in your discussions it leads me to believe that I have been freely including you in discussing my ideas but you are not reciprocating. If you would rather pursue tethered flight projects as competitors that's fine. But if that is so, I would ask that you not use my ideas as your own then. But if you can show that your ideas are significantly different that's fine. All I ask is that you be fair and reciprocate as much or as little as you want and let me know how you would have each of us interact. I am happy discussing tethered flight issues with you or Joe or anybody -- providing they are willing to reciprocate -- and providing they do not take my ideas as their own and share them with just anyone who choose not to reciprocate either. I honestly think Joe and I have had a great relationship as of late, but I do not remember when you have volunteered to give me any information either technically or regarding the politics in our fraternity Dave. If your intention is to give me the brush off Dave I would appreciate it if you would be up front about it rather than acting like a one way gate for knowledge and input.
-- Wayne

PS:  Aren't you talking about the idea of using "vertical blinds" that are arrayed like stacks of kites sideways to generate power cross-wind -- such as places like the Great Plains where in the low level jets that form there generate maximum power at a thousand feet above ground and therefore these "vertical blinds" at a thousand feet in the peak of the low level jet that is present there the stack of "vertical blinds" pulling sideways as an array could sweep power all across   -- Wayne

*Foundation of this folder of files:
There is one other device that I would like to see young minds consider: just a simple round stick that has another stick on top so together they form a "T" -- with each side of the "T" having an aerodynamic shape. Glued together the two sticks become one, but by rubbing the bottom of the "T" with your hands you can get helicopter action. And the bottom part of the stick is more affected by gravity than by the accelerations of this spinning "T" so it causes this device that has no moving parts relative to itself to hover in position. If it starts to dip off to one side then the weight of the bottom stick automatically and yet passively corrects the attitude of this spinning flying "T". So having no moving parts it not only flies until friction causes it to slow down too much, it also passively and automatically corrects for its own attitude to enable hovering. Years after I first marveled at this toy I was told that it was just such a toy that originally inspired Orville and Wilbur into thinking that powered flight was possible.

It's also interesting that my friends at the Flight Research Institute would not believe my claims that a pendulum could passively control the attitude of aircraft. In fact, I knew I was right and they knew they were right so we eventually parted company because they thought that I would not learn from them since they were the foremost authorities on aerodynamics. But it happens that both of us were right . Jet aircraft make too many accelerations to use a pendulum to passively control attitude, but kites need not make too many accelerations to make the accelerations due to gravity unusable. Therefore, I expect real inroads will be made when people can first make kites that passively control their attitude in these ways or other ways. I suggested at the Kracken Foundation that we challenge young people worldwide to become the first to develop this technology ever. But an aeronautical engineer from the University of Washington got the money that the Kracken Foundation gave to see this happen. But Bob Bridenthal, the professor from the University of Washington did not monitor the graduate student who took the ball but did not pursue the goal as I had suggested. Bob apologized, but the opportunity and the finances to pursue it technically were lost for a time then. Joe, hopefully you will not let others lose track of the goal of making a kite with passive attitude adjustment capability. With that we could make anything from kayaks to freighters tack into the wind or with the wind -- and even eventually perhaps -- fly without fuel by totally passive means to monitor and control attitude. "Passive attitude control" should be among our most earnestly sought goals.   ~ Wayne German