Added a "twist" attribute for wings to allow for washout (or washin,

if desired) in the stall.  This allows for fairly docile stalls when
desired, as on trainers (you also need to limit the elevator lift).

diff --git a/src/FDM/YASim/FGFDM.cpp b/src/FDM/YASim/FGFDM.cpp
index 81b50bfb6a9ea95bcb6bc065e9ba5ef330ddf6f2..e959df3c781f55e393fe0feb34fe193a18c13cbc 100644 (file)
--- a/src/FDM/YASim/FGFDM.cpp
+++ b/src/FDM/YASim/FGFDM.cpp
@@ -415,6 +415,7 @@ Wing* FGFDM::parseWing(XMLAttributes* a, const char* type)
     w->setDihedral(attrf(a, "dihedral", defDihed) * DEG2RAD);
     w->setCamber(attrf(a, "camber", 0));
     w->setIncidence(attrf(a, "incidence", 0) * DEG2RAD);
+    w->setTwist(attrf(a, "twist", 0) * DEG2RAD);
 
     // The 70% is a magic number that sorta kinda seems to match known
     // throttle settings to approach speed.

diff --git a/src/FDM/YASim/Surface.cpp b/src/FDM/YASim/Surface.cpp
index e03fb047cff987a6fa1b58efd18b8359c9db58af..3ac62b524c105a17baf0317ad7695f3d513c578f 100644 (file)
--- a/src/FDM/YASim/Surface.cpp
+++ b/src/FDM/YASim/Surface.cpp
@@ -20,6 +20,7 @@ Surface::Surface()
     
     _chord = 0;
     _incidence = 0;
+    _twist = 0;
     _slatPos = _spoilerPos = _flapPos = 0;
     _slatDrag = _spoilerDrag = _flapDrag = 1;
 
@@ -103,6 +104,11 @@ void Surface::setIncidence(float angle)
     _incidence = angle;
 }
 
+void Surface::setTwist(float angle)
+{
+    _twist = angle;
+}
+
 void Surface::setSlatParams(float stallDelta, float dragPenalty)
 {
     _slatAlpha = stallDelta;
@@ -160,7 +166,8 @@ void Surface::calcForce(float* v, float rho, float* out, float* torque)
     // "Rotate" by the incidence angle.  Assume small angles, so we
     // need to diddle only the Z component, X is relatively unchanged
     // by small rotations.
-    out[2] += _incidence * out[0]; // z' = z + incidence * x
+    float incidence = _incidence + _twist;
+    out[2] += incidence * out[0]; // z' = z + incidence * x
 
     // Hold onto the local wind vector so we can multiply the induced
     // drag at the end.
@@ -201,7 +208,7 @@ void Surface::calcForce(float* v, float rho, float* out, float* torque)
 
     // Reverse the incidence rotation to get back to surface
     // coordinates.
-    out[2] -= _incidence * out[0];
+    out[2] -= incidence * out[0];
 
     // Convert back to external coordinates
     Math::tmul33(_orient, out, out);

diff --git a/src/FDM/YASim/Surface.hpp b/src/FDM/YASim/Surface.hpp
index cbbbdf61912066f9508e25329495b7b9c76ba380..1b55e3c45813ead38c237e37e7f33634ca773459 100644 (file)
--- a/src/FDM/YASim/Surface.hpp
+++ b/src/FDM/YASim/Surface.hpp
@@ -42,6 +42,9 @@ public:
     // positive is "up" (i.e. "positive AoA")
     void setIncidence(float angle);
 
+    // The offset from base incidence for this surface.
+    void setTwist(float angle);
+
     void setTotalDrag(float c0);
     float getTotalDrag();
 
@@ -92,6 +95,7 @@ private:
     float _flapPos;
     float _spoilerPos;
     float _incidence;
+    float _twist;
     float _inducedDrag;
 };
 

diff --git a/src/FDM/YASim/Wing.cpp b/src/FDM/YASim/Wing.cpp
index 42cbb3cfdfb3aa383bc90ef0721fc9549ba994e8..9899df8be6d395e0fc449869c53d0c294589f52f 100644 (file)
--- a/src/FDM/YASim/Wing.cpp
+++ b/src/FDM/YASim/Wing.cpp
@@ -15,6 +15,7 @@ Wing::Wing()
     _stall = 0;
     _stallWidth = 0;
     _stallPeak = 0;
+    _twist = 0;
     _camber = 0;
     _incidence = 0;
     _inducedDrag = 1;
@@ -114,6 +115,11 @@ void Wing::setStallPeak(float fraction)
     _stallPeak = fraction;
 }
 
+void Wing::setTwist(float angle)
+{
+    _twist = angle;
+}
+
 void Wing::setCamber(float camber)
 {
     _camber = camber;
@@ -324,6 +330,8 @@ void Wing::compile()
         // and flap1 are set.  Right now flap1 overrides.
 
         int nSegs = (int)Math::ceil((end-start)/segLen);
+        if (_twist != 0 && nSegs < 16) // more segments if twisted
+            nSegs = 16;
         float segWid = _length * (end - start)/nSegs;
 
         int j;
@@ -341,6 +349,7 @@ void Wing::compile()
             sr->surface = s;
             sr->weight = chord * segWid;
             s->setTotalDrag(sr->weight);
+            s->setTwist(_twist * Math::sqrt(1-frac));
             _surfs.add(sr);
 
             if(_mirror) {
@@ -351,6 +360,7 @@ void Wing::compile()
                 sr->surface = s;
                 sr->weight = chord * segWid;
                 s->setTotalDrag(sr->weight);
+                s->setTwist(_twist * Math::sqrt(frac));
                 _surfs.add(sr);
             }
         }

diff --git a/src/FDM/YASim/Wing.hpp b/src/FDM/YASim/Wing.hpp
index 28eabf826a27537716edbdb794a3c35da9550928..5052d7a26b4b1bf7ec393375af984ec3598c4f69 100644 (file)
--- a/src/FDM/YASim/Wing.hpp
+++ b/src/FDM/YASim/Wing.hpp
@@ -27,6 +27,7 @@ public:
     void setStall(float aoa);
     void setStallWidth(float angle);
     void setStallPeak(float fraction);
+    void setTwist(float angle);
     void setCamber(float camber);
     void setIncidence(float incidence);
     void setInducedDrag(float drag) { _inducedDrag = drag; }
@@ -92,6 +93,7 @@ private:
     float _stall;
     float _stallWidth;
     float _stallPeak;
+    float _twist;
     float _camber;
     float _incidence;
     float _inducedDrag;