On Monday 10 Jan 2005 23:42, Andy Ross wrote: > [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
Getting the whole ground-handling sorted out would be nice. Other things like aircraft weather-cocking while stationary in light winds and odd ground handling etc. Just my 2p worth. (IANAP) ;-) Dave Martin _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
