> It's a misfeature in the gear modelling.  YASim has pretty much the
> same behavior.  Both FDMs model gear force as a function of "skidding
> velocity", which is fine for dynamic solutions.  But a gear that is
> planted on the ground is capable of "holding" an aircraft at zero
> velocity, which doesn't work with the current FDMs -- zero velocity
> produces zero force.
It sounds as if we were to tell the weather system to model a significantly 
strong hurricane that we would see the parked aircraft swept away.

What I'm leading up to is that if this effect is happening whilst stationary, 
it's probably making the a/c more difficult to control on takeoff than it 
really is.  That is if it still happens when the a/c is rolling.

Just thinking about it...
When the a/c is stationary the force on the wheels is the aircraft weight less 
the lift due to airflow over the lifting surfaces (a function of wind).  As 
the a/c progresses on takeoff the above effect should change as the a/c gains 

If it's having an effect straight away does it not need offsetting until a 
certain airspeed is reached (due to the weather system or a/c movement)?

> What's needed is code that, at low speeds, uses a spring model for
> gear force based on the distance in position from where the gear is
> "stopped".  Which sounds easy, but in practice is awfully hard.  I've
> gotten started on this several times, and never produced useful
> code.
So you're suggesting that the a/c mass, a friction coefficient dependent on 
weather condition and landing surface and tyre contact area are combined to 
provide a more realistic static case?

If I've interpreted you correctly... what was the problem encountered?


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