[bouncing replies to flightgear-devel] David Megginson wrote: > I don't know if we're modelling this or not, but with full power you > often need a lot of rudder to keep a plane straight during the > takeoff roll even when there is no crosswind. During the landing > roll, with no power, it is a lot easier.
YASim is definitely not doing this right. This is because in a real plane the wheel casters a little, which has the effect of twisting the nosewheel away from the wind. On planes with a direct linkage between the nosewheel and the rudder, this is essentially the same as applying a control force. YASim doesn't model this kind of "castering torque" on the nosewheel. I know Curt was complaining to me once about an aircraft that would yaw violently in crosswinds once the nose came up -- I think this was the reason. When the nosewheel is on the ground, it isn't trying to "steer into the wind" like a real plane would be; so on rotation the pilot hasn't applied the right amount of correcting rudder. Modelling this would involve some complicated per-airplane configuration, I think. I guess we could start by defining a "castering distance" (distance from the wheel contact point to the rotation axis) and interpolate the force as linear across the full rudder travel to get a effecting "rudder trim" setting. Other planes (I know the 152, probably other Cessnas) have a spring connecting the nosewheel to the rudder cables, so they will see a similar but smaller effect. Then again, some planes have fully castering nosewheels with no rudder linkage and steer with braking. These get modelled correctly as-is. Andy _______________________________________________ Flightgear-users mailing list [email protected] http://mail.flightgear.org/mailman/listinfo/flightgear-users 2f585eeea02e2c79d7b1d8c4963bae2d
