In last time flight with side wind, the plane gound control of FG at last drove me to very limit of my patience.
No, really, guys, FG plane behaviour on ground is fenomenal:
- plane speen is less 5 km/h (human walk speed), i move rudder to the left to value about 1 degrees and the plane begin pwerful rotation to the left;
that is absolutely incorrect behaviour.
I beleive the wind (aver pressure P) to rudder (aver square S) rotated (to angle A) gives roation force Fr ~ P*S*Sin(A);
and the wind (pressure P) depends on air flow relative plane (IAS V) and additional air flow due to propeller (coeff Cp(RPM,IAS)), and since for any V,F m*V^2/2=F+L, Fr and P ~ V^2, that means P ~ V^2*Cp;
it results to Fr ~ V^2*Cp*S*Sin(A) and in the case of V=5km/h and Sin(3.14/180rad) is very near to zero, the Fr is very very low also.
All depends on plane, but i suppose we need IAS 60 km/h and more to feel air rudder light influence to movement trajectory in high angle rotated rudder on my probe plane.
It is curiouse to me, am i only person in the world for all the time who try to drive on FG plane on ground? Or what?
As i know, in the plane as YAK-52/53, that are without active nose or tail gear wheel, there is "brake force reduction (differentiation)" depends on rudder rotation angle, in other words, the more rudder is rotated to left, the more pressure to the brake of left gear wheel is applied in comparison with right gear wheel.
And i need move rudder to left in large angle and press lever of "main brake with reduction mechanism" by value before reduction between [0.0-1.0] to valuable rotate left plane with the low speed on the ground (or use separated wheel brakes if it exist in the plane).
So, in FG should be
- noticable changes in rudder influence to flight direction depended on non-linear IAS^2 and Cp(RPM,IAS);
- correct plane turns on ground.
Who is familiar with FG internals and can explain me how the behaviour could be expressed in FG with JSB?
I've taken a first look in FG source and found something like this:
JSBSim.cxx
FCS->SetDrCmd( -globals->get_controls()->get_rudder() );
To avoid digging the whole code, we need to
- know how the plane rotaion evaluated with "DrCmd";
- in which place;
- and how to turn the evaluation in right order.
Your advices.
2.
And also, how to adjust wheel brake system of FG plane to ensure brakes are applied with right forces and brake/unbrake time is specified correctly.
I am not sure, but by my feelings, no one plane in the world, as FG planes do, gives you so many energy to the high and even accelerated rotation around single brakeed side gear in slowing down light (2500kg) plane with low speed, othewise we need only airplanes instead of power stations.