Anders GIDENSTAM: fix slip skid ball (merge from JSBSim/cvs)

JSB: "Fixed a problem with turn coordinator bounding while at rest on the runway"

diff --git a/src/FDM/JSBSim/models/FGAuxiliary.cpp b/src/FDM/JSBSim/models/FGAuxiliary.cpp
index bb637c9d02871effe70cad899c3b4d5f61747dc5..86d1cbdc53f7e6323e760eb2c49d56ac59d2bb59 100755 (executable)
--- a/src/FDM/JSBSim/models/FGAuxiliary.cpp
+++ b/src/FDM/JSBSim/models/FGAuxiliary.cpp
@@ -225,7 +225,13 @@ bool FGAuxiliary::Run()
      vPilotAccel += Propagate->GetPQRdot() * vToEyePt;
      vPilotAccel += vPQR * (vPQR * vToEyePt);
   } else {
-     vPilotAccel = Propagate->GetTl2b() * FGColumnVector3( 0.0, 0.0, Inertial->gravity() );
+     // The line below handles low velocity (and on-ground) cases, basically
+     // representing the opposite of the force that the landing gear would
+     // exert on the ground (which is just the total weight). This eliminates
+     // any jitter that could be introduced by the landing gear. Theoretically,
+     // this branch could be eliminated, with a penalty of having a short
+     // transient at startup (lasting only a fraction of a second).
+     vPilotAccel = Propagate->GetTl2b() * FGColumnVector3( 0.0, 0.0, -Inertial->gravity() );
   }
 
   vPilotAccelN = vPilotAccel/Inertial->gravity();