Basically complete support for piston engine startup, including power loss

due to single-magneto operation.  Seems to work.

src/FDM/YASim/ControlMap.cpp

@@ -77,6 +77,8 @@ void ControlMap::addMapping(int input, int type, void* object, int options)
     map->src0 = map->dst0 = 0;
     if(type==FLAP0 || type==FLAP1 || type==STEER)
 	map->src0 = map->dst0 = -1;
+    if(type==MAGNETOS)
+	map->src1 = map->dst1 = 3;
 
     // And add it to the approproate vectors.
     Vector* maps = (Vector*)_inputs.get(input);
@@ -141,8 +143,8 @@ void ControlMap::applyControls()
 	switch(o->type) {
 	case THROTTLE: ((Thruster*)obj)->setThrottle(lval);        break;
 	case MIXTURE:  ((Thruster*)obj)->setMixture(lval);         break;
-	case STARTER:  ((Thruster*)obj)->setStarter(bool(lval));   break;
+	case STARTER:  ((Thruster*)obj)->setStarter((bool)lval);   break;
-	case MAGNETOS: ((PropEngine*)obj)->setMagnetos(int(lval)); break;
+	case MAGNETOS: ((PropEngine*)obj)->setMagnetos((int)lval); break;
 	case ADVANCE:  ((PropEngine*)obj)->setAdvance(lval);       break;
 	case REHEAT:   ((Jet*)obj)->setReheat(lval);               break;
 	case VECTOR:   ((Jet*)obj)->setRotation(lval);             break;

src/FDM/YASim/PistonEngine.cpp

@@ -5,6 +5,7 @@ namespace yasim {
 
 const static float HP2W = 745.7;
 const static float CIN2CM = 1.6387064e-5;
+const static float RPM2RADPS = 0.1047198;
 
 PistonEngine::PistonEngine(float power, float speed)
 {
@@ -71,9 +72,14 @@ void PistonEngine::setThrottle(float t)
     _throttle = t;
 }
 
+void PistonEngine::setRunning(bool r)
+{
+    _running = r;
+}
+
 void PistonEngine::setStarter(bool s)
 {
-    _starter = s;
+    _cranking = s;
 }
 
 void PistonEngine::setMagnetos(int m)
@@ -123,19 +129,10 @@ float PistonEngine::getEGT()
 
 void PistonEngine::calc(float pressure, float temp, float speed)
 {
-    if (_magnetos == 0) {
+    if(_magnetos == 0 || speed < 200*RPM2RADPS)
-      _running = false;
+	_running = false;
-      _mp = pressure;
+    else
-      _torque = 0;
+	_running = true;
-      _fuelFlow = 0;
-      _egt = 80;		// FIXME: totally made-up
-      return;
-    }
-
-    _running = true;
-    _cranking = false;
-
-    // TODO: degrade performance on single magneto
 
     // Calculate manifold pressure as ambient pressure modified for
     // turbocharging and reduced by the throttle setting.  According
@@ -178,11 +175,30 @@ void PistonEngine::calc(float pressure, float temp, float speed)
     else
         burned = _fuelFlow + (burnable-_fuelFlow)*(r-.625)*(4.0/3.0);
 
+    // Correct for engine control state
+    if(!_running)
+	burned = 0;
+    if(_magnetos < 3)
+	burned *= 0.9;
+
     // And finally the power is just the reference power scaled by the
     // amount of fuel burned, and torque is that divided by RPM.
     float power = _power0 * burned/_f0;
     _torque = power/speed;
 
+    // Figure that the starter motor produces 20% of the engine's
+    // cruise torque.
+    if(_cranking && !_running)
+	_torque += 0.20 * _power0/_omega0;
+
+    // Also, add a negative torque of 10% of cruise, to represent
+    // internal friction.  Propeller aerodynamic friction is too low
+    // at low RPMs to provide a good deceleration.  Interpolate it
+    // away as we approach cruise RPMs, though, to prevent interaction
+    // with the power computations.  Ugly.
+    if(speed > 0 && speed < _omega0)
+	_torque -= 0.05 * (_power0/_omega0) * (1 - speed/_omega0);
+
     // Now EGT.  This one gets a little goofy.  We can calculate the
     // work done by an isentropically expanding exhaust gas as the
     // mass of the gas times the specific heat times the change in
@@ -204,6 +220,7 @@ void PistonEngine::calc(float pressure, float temp, float speed)
     float specHeat = 1300;
     float corr = 1.0/(Math::pow(_compression, 0.4) - 1);
     _egt = corr * (power * 1.1) / (massFlow * specHeat);
+    if(_egt < temp) _egt = temp;
 }
 
 }; // namespace yasim

src/FDM/YASim/PistonEngine.hpp

@@ -17,6 +17,9 @@ public:
     void setMixture(float mixture);
     void setBoost(float boost); // fraction of turbo-mul used
 
+    // For solver use
+    void setRunning(bool r);
+
     float getMaxPower(); // max sea-level power
 
     void calc(float pressure, float temp, float speed);

src/FDM/YASim/PropEngine.cpp

@@ -82,10 +82,11 @@ void PropEngine::stabilize()
 {
     float speed = -Math::dot3(_wind, _dir);
     _eng->setThrottle(_throttle);
-    _eng->setStarter(_starter);
-    _eng->setMagnetos(true);	// FIXME: otherwise, an infinite loop
     _eng->setMixture(_mixture);
 
+    _eng->setMagnetos(3);
+    _eng->setRunning(true);
+
     if(_variable) {
 	_omega = _minOmega + _advance * (_maxOmega - _minOmega);
 	_prop->modPitch(1e6); // Start at maximum pitch and move down
@@ -117,6 +118,9 @@ void PropEngine::stabilize()
 	    else            _prop->modPitch(1-(step*0.005));
 	}
     }
+
+    // ...and back off
+    _eng->setRunning(false);
 }
 
 void PropEngine::integrate(float dt)
@@ -143,10 +147,6 @@ void PropEngine::integrate(float dt)
     float rotacc = (engTorque-propTorque)/Math::abs(_moment);
     _omega += dt * rotacc;
 
-    // Clamp to a 500 rpm idle.  This should probably be settable, and
-    // needs to go away when the startup code gets written.
-//     if(_omega < 52.3) _omega = 52.3;
-
     // Store the total angular momentum into _gyro
     Math::mul3(_omega*_moment, _dir, _gyro);