Jim Wilson:

> > Here's a patch to add manual-pitch control to the propeller in YASim.  A new
> > control axis "PROPPITCH" is added.  Requires "manual-pitch" boolean property
> > in the "propeller" tag.
> >
> > Tags and Properties to add in order to enable:
> >
> > manual-pitch="true"
> >
> > <control-input axis="/controls/engines/engine[0]/propeller-pitch"
> > control="PROPPITCH" src0="0" src1="1" dst0="0.40" dst1="0.80"/>
> >
> > Note that for the time being, excessively low RPM or excessively high RPM is
> > brought undercontrol by a scaling range defined in the control-input tag
> > (see "dst0" and "dst1" properties).

src/FDM/YASim/ControlMap.cpp

@@ -5,6 +5,7 @@
 #include "Gear.hpp"
 #include "Wing.hpp"
 #include "Math.hpp"
+#include "Propeller.hpp"
 
 #include "ControlMap.hpp"
 namespace yasim {
@@ -187,6 +188,7 @@ void ControlMap::applyControls(float dt)
 	case STARTER:  ((Thruster*)obj)->setStarter(lval != 0.0);  break;
 	case MAGNETOS: ((PropEngine*)obj)->setMagnetos((int)lval); break;
 	case ADVANCE:  ((PropEngine*)obj)->setAdvance(lval);       break;
+        case PROPPITCH: ((PropEngine*)obj)->setPropPitch(lval); break;
 	case REHEAT:   ((Jet*)obj)->setReheat(lval);               break;
 	case VECTOR:   ((Jet*)obj)->setRotation(lval);             break;
 	case BRAKE:    ((Gear*)obj)->setBrake(lval);               break;

src/FDM/YASim/ControlMap.hpp

@@ -13,7 +13,7 @@ public:
 		      ADVANCE, REHEAT, PROP,
 		      BRAKE, STEER, EXTEND,
 		      INCIDENCE, FLAP0, FLAP1, SLAT, SPOILER, VECTOR,
-                      BOOST, CASTERING };
+                      BOOST, CASTERING, PROPPITCH };
 
     enum { OPT_SPLIT  = 0x01,
            OPT_INVERT = 0x02,

src/FDM/YASim/FGFDM.cpp

@@ -475,6 +475,10 @@ void FGFDM::parsePropeller(XMLAttributes* a)
 	thruster->setVariableProp(min, max);
     }
 
+    if(a->hasAttribute("manual-pitch")) {
+	prop->setManualPitch();
+    }
+
     char buf[64];
     sprintf(buf, "/engines/engine[%d]", _nextEngine++);
     EngRec* er = new EngRec();
@@ -525,6 +529,7 @@ int FGFDM::parseOutput(const char* name)
     if(eq(name, "SLAT"))      return ControlMap::SLAT;
     if(eq(name, "SPOILER"))   return ControlMap::SPOILER;
     if(eq(name, "CASTERING")) return ControlMap::CASTERING;
+    if(eq(name, "PROPPITCH")) return ControlMap::PROPPITCH;
     SG_LOG(SG_FLIGHT,SG_ALERT,"Unrecognized control type '"
            << name << "' in YASim aircraft description.");
     exit(1);

src/FDM/YASim/PropEngine.cpp

@@ -34,6 +34,12 @@ void PropEngine::setAdvance(float advance)
     _advance = Math::clamp(advance, 0, 1);
 }
 
+void PropEngine::setPropPitch(float proppitch)
+{
+    // update Propeller property
+    _prop->setPropPitch(proppitch);
+}
+
 void PropEngine::setVariableProp(float min, float max)
 {
     _variable = true;

src/FDM/YASim/PropEngine.hpp

@@ -15,6 +15,7 @@ public:
 
     void setMagnetos(int magnetos);
     void setAdvance(float advance);
+    void setPropPitch(float proppitch);
     void setVariableProp(float min, float max);
 
     virtual PropEngine* getPropEngine() { return this; }

src/FDM/YASim/Propeller.cpp

@@ -22,6 +22,8 @@ Propeller::Propeller(float radius, float v, float omega,
     _f0 = 2*_etaC*power/(rho*v*V2);
 
     _matchTakeoff = false;
+    _manual = false;
+    _proppitch = 0;
 }
 
 void Propeller::setTakeoff(float omega0, float power0)
@@ -42,10 +44,26 @@ void Propeller::modPitch(float mod)
     if(_j0 > 4*_baseJ0)     _j0 = 4*_baseJ0;
 }
 
+void Propeller::setManualPitch()
+{
+    _manual = true;
+}
+
+void Propeller::setPropPitch(float proppitch)
+{
+    // makes only positive range of axis effective.
+    _proppitch = Math::clamp(proppitch, 0, 1);
+}
 
 void Propeller::calc(float density, float v, float omega,
 		     float* thrustOut, float* torqueOut)
 {
+    if (_manual) {
+        float pps = _proppitch * 0.9999f; // avoid singularity
+        pps = 1 + ( Math::pow(pps,-1/(pps-1)) - Math::pow(pps,-pps/(pps-1)) );
+        _j0 = (4*_baseJ0) -  (  ((4*_baseJ0) - (0.26f*_baseJ0)) * pps );
+    }
+
     float tipspd = _r*omega;
     float V2 = v*v + tipspd*tipspd;
 

src/FDM/YASim/Propeller.hpp

@@ -20,6 +20,10 @@ public:
 
     void modPitch(float mod);
 
+    void setPropPitch(float proppitch);
+
+    void setManualPitch();
+
     void calc(float density, float v, float omega,
 	      float* thrustOut, float* torqueOut);
 
@@ -33,6 +37,8 @@ private:
     float _beta;        // constant, ~1.48058;
     float _tc0;         // thrust "coefficient" at takeoff
     bool  _matchTakeoff; // Does _tc0 mean anything?
+    bool  _manual;   // manual pitch mode
+    float _proppitch; // prop pitch control setting (0 ~ 1.0)
 };
 
 }; // namespace yasim