- Static friction would be the force you would need to get the wheels to roll
- Dynamic friction is for movement with locked brakes
- Rolling friction would be the force you would have to apply to keep the wheels rolling at a constant speed
It could very well be that I have that I static and dynamic friction are the other way around, as the JSBSim manual states that in general static is greater than dynamic that is greater than rolling friction.
From pp. 39-40 of the JSBSim reference manual:
The ground tangential reaction is thus obtained by the formula
Ft = u * Fn
where u is the friction coefficient and Fn is the normal force described above. JSBSim uses a
different value for u depending on the state of the contact point. Three properties describe these
different values: <static_friction>, <dynamic_friction> and <rolling_friction>. The static coefficient
is used when the contact point is at rest, while the dynamic coefficient is used when the contact
point is sliding. The last coefficient, <rolling_friction> is only relevant for the BOGEY contact type;
it models the resistance of the wheel to its rolling. Experience shows that, in the general case, the
static friction coefficient is higher than the dynamic coefficient which, in its turn, is much higher
than the rolling coefficient, which typically has a value of about 0.02.