On Mon, 26 Apr 2004 09:54:43 +0200, Mathias wrote in message 

> On Montag, 26. April 2004 00:13, Arnt Karlsen wrote:


> > ..a wee virtual demo on tire side wall flex:  Take a parked, say
> > Cessna 172, out at the leading edge of the very wing tip, and push
> > it straight aft, then release, and repeat.
> >
> > ..once you get your repeat pushes close to the system resonance
> > frequency, you will find wee pushes generates quite a yaw
> > oscillation, and that it will swing around a point somewhere near
> > the nose wheel. System here, is, tire side wall flexibility (some
> > people prefer doing calculus on its inverse, "tire sidewall
> > stiffness"), against _parts_ of the wings + tail + nose etc masses.
> What you describe here will most likely not happen with someting only
> velocity dependent.

..no?  ;-)  No velocity, plane is parked.  Wee pushes, to exite the
resonance.  IME, the wee pushes straight aft gets the the plane 
dancing quite a bit, try it.  ;-)

> Keep it in your head and try to move your aircraft around its nose

..not around the nose, around the nose wheel, usually around a point
somewhere between the nose wheel and the mains.

> with that method when we have a better tire model. It you don't get it
> turned, we can look if this is doable :-)

..it even works on wet ice in RL. 
Also for turning the plane around.  ;-)


> > ..15 feet forward, then back to those marks, will do fine.
> > Note how far down the tires crept.  Tire creep.  ;-)
> This is what I expect to show up with the Pacejka model. Let's see
> when this is done ...

.. :-)

..med vennlig hilsen = with Kind Regards from Arnt... ;-)
...with a number of polar bear hunters in his ancestry...
  Scenarios always come in sets of three: 
  best case, worst case, and just in case.

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