Sync'ed with JSBSim v1.1.5

- Lower the allowable minimum propeller inertia from 1e-3 to 1e-6
- Account for the vehicle angular rates in the computation of propellers local velocities.
- Apply the engine torque to the vehicle (The aerodynamic torque was applied until now but it is the engine generated torque that the aircraft is actually submitted to)
- Prevent FGPiston from sending negative powers to thrusters
- Fixed FGMagnetometer : no need to update the magnetic field every time step.
- FGMassBalance: remove a direct reference to FGGroundReactions

src/FDM/JSBSim/FGFDMExec.cpp

@@ -483,6 +483,7 @@ void FGFDMExec::LoadInputs(unsigned int idx)
     MassBalance->in.TanksWeight = Propulsion->GetTanksWeight();
     MassBalance->in.TanksMoment = Propulsion->GetTanksMoment();
     MassBalance->in.TankInertia = Propulsion->CalculateTankInertias();
+    MassBalance->in.WOW         = GroundReactions->GetWOW();
     break;
   case eAircraft:
     Aircraft->in.AeroForce     = Aerodynamics->GetForces();

src/FDM/JSBSim/models/FGMassBalance.cpp

@@ -42,7 +42,6 @@ INCLUDES
 
 #include "FGMassBalance.h"
 #include "FGFDMExec.h"
-#include "FGGroundReactions.h"
 #include "input_output/FGXMLElement.h"
 
 using namespace std;
@@ -55,7 +54,7 @@ CLASS IMPLEMENTATION
 
 
 FGMassBalance::FGMassBalance(FGFDMExec* fdmex)
-  : FGModel(fdmex), GroundReactions(nullptr)
+  : FGModel(fdmex)
 {
   Name = "FGMassBalance";
   Weight = EmptyWeight = Mass = 0.0;
@@ -90,7 +89,6 @@ bool FGMassBalance::InitModel(void)
 {
   if (!FGModel::InitModel()) return false;
 
-  GroundReactions = FDMExec->GetGroundReactions();
   vLastXYZcg.InitMatrix();
   vDeltaXYZcg.InitMatrix();
 
@@ -211,7 +209,7 @@ bool FGMassBalance::Run(bool Holding)
 
   // Compensate displacements of the structural frame when the mass distribution
   // is modified while the aircraft is in contact with the ground.
-  if (FDMExec->GetHoldDown() || GroundReactions->GetWOW())
+  if (FDMExec->GetHoldDown() || in.WOW)
     Propagate->NudgeBodyLocation(vDeltaXYZcgBody);
 
 // Calculate new total moments of inertia

src/FDM/JSBSim/models/FGMassBalance.h

@@ -188,11 +188,11 @@ public:
     FGMatrix33 GasInertia;
     FGColumnVector3 TanksMoment;
     FGMatrix33 TankInertia;
+    bool WOW;
   } in;
 
 private:
   FGPropagate* Propagate;
-  FGGroundReactions* GroundReactions;
   double Weight;
   double EmptyWeight;
   double Mass;

src/FDM/JSBSim/models/atmosphere/FGStandardAtmosphere.h

@@ -101,7 +101,7 @@ public:
   FGStandardAtmosphere(FGFDMExec*);
 
   /// Destructor
-  ~FGStandardAtmosphere() override;
+  virtual ~FGStandardAtmosphere();
 
   bool InitModel(void) override;
 

src/FDM/JSBSim/models/flight_control/FGMagnetometer.cpp

@@ -100,12 +100,19 @@ FGMagnetometer::~FGMagnetometer()
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+void FGMagnetometer::ResetPastStates(void)
+{
+  FGSensor::ResetPastStates();
+  counter = 0;
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 void FGMagnetometer::updateInertialMag(void)
 {
   if (counter++ % INERTIAL_UPDATE_RATE == 0)//dont need to update every iteration
   {
-    counter = 0;
-
     usedLat = (Propagate->GetGeodLatitudeRad());//radians, N and E lat and long are positive, S and W negative
     usedLon = (Propagate->GetLongitude());//radians
     usedAlt = (Propagate->GetGeodeticAltitude()*fttom*0.001);//km

src/FDM/JSBSim/models/flight_control/FGMagnetometer.h

@@ -123,6 +123,7 @@ public:
   ~FGMagnetometer();
 
   bool Run (void) override;
+  void ResetPastStates(void) override;
 
 private:
   FGPropagate* Propagate;

src/FDM/JSBSim/models/propulsion/FGForce.cpp

@@ -50,9 +50,8 @@ namespace JSBSim {
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-FGForce::FGForce(FGFDMExec *FDMExec) :
-                 fdmex(FDMExec),
-                 ttype(tNone)
+FGForce::FGForce(FGFDMExec *FDMExec)
+  : fdmex(FDMExec), MassBalance(fdmex->GetMassBalance()), ttype(tNone)
 {
   vFn.InitMatrix();
   vMn.InitMatrix();
@@ -87,7 +86,7 @@ const FGColumnVector3& FGForce::GetBodyForces(void)
   // needs to be done like this to convert from structural to body coords.
   // CG and RP values are in inches
 
-  FGColumnVector3 vDXYZ = fdmex->GetMassBalance()->StructuralToBody(vActingXYZn);
+  FGColumnVector3 vDXYZ = MassBalance->StructuralToBody(vActingXYZn);
 
   vM = vMn + vDXYZ*vFb;
 

src/FDM/JSBSim/models/propulsion/FGForce.h

@@ -67,6 +67,7 @@ FORWARD DECLARATIONS
 namespace JSBSim {
 
 class FGFDMExec;
+class FGMassBalance;
 
 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 CLASS DOCUMENTATION
@@ -305,6 +306,7 @@ public:
 
 protected:
   FGFDMExec *fdmex;
+  FGMassBalance* MassBalance;
   FGColumnVector3 vFn;
   FGColumnVector3 vMn;
   FGColumnVector3 vOrient;

src/FDM/JSBSim/models/propulsion/FGPiston.cpp

@@ -518,7 +518,10 @@ void FGPiston::Calculate(void)
   }
 
   LoadThrusterInputs();
-  Thruster->Calculate(HP * hptoftlbssec);
+  // Filters out negative powers.
+  // TODO: static_friction_HP should not be taken into account while the engine
+  // is not started.
+  Thruster->Calculate(max(HP * hptoftlbssec, 0.));
 
   RunPostFunctions();
 }

src/FDM/JSBSim/models/propulsion/FGPropeller.cpp

@@ -41,6 +41,7 @@ INCLUDES
 #include "FGFDMExec.h"
 #include "FGPropeller.h"
 #include "input_output/FGXMLElement.h"
+#include "models/FGMassBalance.h"
 
 using namespace std;
 
@@ -50,11 +51,6 @@ namespace JSBSim {
 CLASS IMPLEMENTATION
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
-// This class currently makes certain assumptions when calculating torque and
-// p-factor. That is, that the axis of rotation is the X axis of the aircraft -
-// not just the X-axis of the engine/propeller. This may or may not work for a
-// helicopter.
-
 FGPropeller::FGPropeller(FGFDMExec* exec, Element* prop_element, int num)
                        : FGThruster(exec, prop_element, num)
 {
@@ -75,7 +71,7 @@ FGPropeller::FGPropeller(FGFDMExec* exec, Element* prop_element, int num)
   Vinduced = 0.0;
 
   if (prop_element->FindElement("ixx"))
-    Ixx = max(prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2"), 0.001);
+    Ixx = max(prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2"), 1e-06);
 
   Sense_multiplier = 1.0;
   if (prop_element->HasAttribute("version")
@@ -205,7 +201,13 @@ void FGPropeller::ResetToIC(void)
 
 double FGPropeller::Calculate(double EnginePower)
 {
-  FGColumnVector3 localAeroVel = Transform().Transposed() * in.AeroUVW;
+  FGColumnVector3 vDXYZ = MassBalance->StructuralToBody(vActingXYZn);
+  const FGMatrix33& mT = Transform();
+  // Local air velocity is obtained from Stevens & Lewis' "Aircraft Control and
+  // Simualtion (3rd edition)" eqn 8.2-1
+  // Variables in.AeroUVW and in.AeroPQR include the wind and turbulence effects
+  // as computed by FGAuxiliary.
+  FGColumnVector3 localAeroVel = mT.Transposed() * (in.AeroUVW + in.AeroPQR*vDXYZ);
   double omega, PowerAvailable;
 
   double Vel = localAeroVel(eU);
@@ -268,6 +270,7 @@ double FGPropeller::Calculate(double EnginePower)
   omega = RPS*2.0*M_PI;
 
   vFn(eX) = Thrust;
+  vTorque(eX) = -Sense*EnginePower / max(0.01, omega);
 
   // The Ixx value and rotation speed given below are for rotation about the
   // natural axis of the engine. The transform takes place in the base class
@@ -284,7 +287,7 @@ double FGPropeller::Calculate(double EnginePower)
 
   // Transform Torque and momentum first, as PQR is used in this
   // equation and cannot be transformed itself.
-  vMn = in.PQRi*(Transform()*vH) + Transform()*vTorque;
+  vMn = in.PQRi*(mT*vH) + mT*vTorque;
 
   return Thrust; // return thrust in pounds
 }
@@ -354,7 +357,6 @@ double FGPropeller::GetPowerRequired(void)
   double local_RPS = RPS < 0.01 ? 0.01 : RPS; 
 
   PowerRequired = cPReq*local_RPS*local_RPS*local_RPS*D5*in.Density;
-  vTorque(eX) = -Sense*PowerRequired / (local_RPS*2.0*M_PI);
 
   return PowerRequired;
 }