Brendan Black:

when active does not touch the way the YASim jet calculates fuel flow, but separates out the afterburning component of thrust, calculates the TSFC of that component and uses the same method of fuel flow calculation for the afterburning component then adds it to the existing fuel flow

When inactive (atsfc doesn't exist or is zero) it just behaves exactly as before

I finally got around to testing this small patch thoroughly, and I'm satisfied that it doesn't affect anything else & works across many different versions (i've been testing it with current as it has changed over the last 7 months)

diff --git a/src/FDM/YASim/FGFDM.cpp b/src/FDM/YASim/FGFDM.cpp
index 907166171a29dc8801562ee2d27809934d2b639c..36eec1534609c54b4397ca634720f8ba86a621c5 100644 (file)
--- a/src/FDM/YASim/FGFDM.cpp
+++ b/src/FDM/YASim/FGFDM.cpp
@@ -306,6 +306,7 @@ void FGFDM::startElement(const char* name, const XMLAttributes &atts)
        j->setRPMs(n1min, n1max, n2min, n2max);
 
        j->setTSFC(attrf(a, "tsfc", 0.8));
+       j->setATSFC(attrf(a, "atsfc", 0.0));
        if(a->hasAttribute("egt"))  j->setEGT(attrf(a, "egt"));
        if(a->hasAttribute("epr"))  j->setEPR(attrf(a, "epr"));
        if(a->hasAttribute("exhaust-speed"))

diff --git a/src/FDM/YASim/Jet.cpp b/src/FDM/YASim/Jet.cpp
index f80cac543daee572160a6247eee53b9733672b67..ca69b88a59bd14968e1a7b7110093ce9c7bba139 100644 (file)
--- a/src/FDM/YASim/Jet.cpp
+++ b/src/FDM/YASim/Jet.cpp
@@ -6,6 +6,7 @@ namespace yasim {
 Jet::Jet()
 {
     _maxThrust = 0;
+    _abThrust = 0;
     _abFactor = 1;
     _reheat = 0;
     _rotControl = 0;
@@ -18,6 +19,8 @@ Jet::Jet()
     _vMax = 800;
     _epr0 = 3.0;
     _tsfc = 0.8f;
+    _atsfc = 0.0f;
+    _abFuelFactor = 3.5f; //previously was constant in code below
     _egt0 = 1050;
     _n1Min = 55;
     _n1Max = 102;
@@ -51,7 +54,9 @@ void Jet::setMaxThrust(float thrust, float afterburner)
 {
     _maxThrust = thrust;
     if(afterburner == 0) _abFactor = 1;
-    else                 _abFactor = afterburner/thrust;
+    else {                _abFactor = afterburner/thrust;
+                          _abThrust = afterburner - thrust;
+    }
 }
 
 void Jet::setVMax(float spd)
@@ -64,6 +69,11 @@ void Jet::setTSFC(float tsfc)
     _tsfc = tsfc;
 }
 
+void Jet::setATSFC(float atsfc)
+{
+    _atsfc = atsfc;
+}
+
 void Jet::setRPMs(float idleN1, float maxN1, float idleN2, float maxN2)
 {
     _n1Min = idleN1;
@@ -190,9 +200,14 @@ void Jet::integrate(float dt)
     _epr = beta + 1;
     float ff0 = _maxThrust*_tsfc*(1/(3600.0f*9.8f)); // takeoff fuel flow, kg/s
     _fuelFlow = ff0 * beta*ibeta0;
-    _fuelFlow *= 1 + (3.5f * _reheat * _abFactor); // Afterburners take
+    //Calc afterburner only tsfc if atsfc is set
+    if(_atsfc > 0) _abFuelFactor = ((_maxThrust*_abFactor*_atsfc)-(_maxThrust*_tsfc))/_abThrust;
+    if(_atsfc == 0 ) _fuelFlow *= 1 + (_abFuelFactor * _reheat * _abFactor); // Afterburners take
                                                  // 3.5 times as much
                                                  // fuel per thrust unit
+    else _fuelFlow += _abThrust*_abFuelFactor*(1/(3600.0f*9.8f))*beta*ibeta0*_reheat; 
+    // add afterburning only component of fuel flow
+
     _egt = T0 + beta*ibeta0 * (_egt0 - T0);
 
     // Thrust reverse handling:

diff --git a/src/FDM/YASim/Jet.hpp b/src/FDM/YASim/Jet.hpp
index 9bfe6512e15ba90a1801ee49669468177789e2de..2274072230647ed749aecbec4dce1d0b87be5d3e 100644 (file)
--- a/src/FDM/YASim/Jet.hpp
+++ b/src/FDM/YASim/Jet.hpp
@@ -14,6 +14,7 @@ public:
     void setMaxThrust(float thrust, float afterburner=0);
     void setVMax(float spd);
     void setTSFC(float tsfc);
+    void setATSFC(float atsfc);
     void setRPMs(float idleN1, float maxN1, float idleN2, float maxN2);
     void setEGT(float takeoffEGT);
     void setEPR(float takeoffEPR);
@@ -57,6 +58,7 @@ private:
     bool _reverseThrust;
 
     float _maxThrust; // Max dry thrust at sea level
+    float _abThrust; // Max ab component of thrust at sea level
     float _abFactor;  // Afterburner thrust multiplier
 
     float _maxRot;
@@ -66,6 +68,8 @@ private:
     float _vMax;   // speed at which thrust is zero
     float _epr0;   // EPR at takeoff thrust
     float _tsfc;   // TSFC ((lb/hr)/lb) at takeoff thrust and zero airspeed
+    float _atsfc;   // Afterburning TSFC ((lb/hr)/lb) at takeoff thrust and zero airspeed (total TSFC)
+    float _abFuelFactor;   // Afterburner Only Fuel Factor at takeoff thrust and zero airspeed
     float _egt0;   // EGT at takeoff thrust
     float _n1Min;  // N1 at ground idle
     float _n1Max;  // N1 at takeoff thrust