On Mon, 26 Apr 2004 12:14:49 +0200, Mathias wrote in message <[EMAIL PROTECTED]>:
> On Montag, 26. April 2004 11:49, Arnt Karlsen wrote: > > > 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. ;-) > Sorry, I do not have an aircraft ... > :( > But I can well imagine. > > > > 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. > > Sorry, this is what I meant. > By doing what you explained the vehicle will twist around its > longitudinal axis. ..the wee pushes are ideally in paralell to the logitudinal axis, but "takes advantage" of the moment arm of the wing to make up torque pulses around a vertical axis, which sets up a yaw oscillation around possibly the same vertical axis. > This will mostly not change the weight force on the nose wheel. ..correct. However it sees sidewall flexing forces. > So this one will stay fixed. What changes is the weight force on the > other two wheels which will loose static friction for a short time. ..wrong, except when you move the plane around on wet ice. This oscillation is driven by torque pulses, the resonance frequency is a function of the mass distribution and the tire sidewall flexibility, and the tires are held by the plane's weight and static friction. > And when you apply a little side force during this time the aircraft > will move. The nose wheel is fixed by static friction, thus the ac > moves around the nosewheel ... ..depends on how you push, it is possible to get the plane dancing around a point forward of the nose wheel, flexing the sidewalls the same way, swinging around the nosewheel, "not" flexing the nose wheel sidewalls, and around a point between the wheels, flexing the nose wheel sidewalls and mains sidewalls, the oposite ways. > The more I think about that, the more I can imagine that even that is > in the Pacejka formula. Not with the real physical reason, but I can > well imagine that it will just behave like that ... > I am not shure how big the influence of the gear strut dynamics is in > this case... > > Let's see ... > I have to push this stuff I have now to Jon first ... ..amen!. ;-) -- ..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. _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
