From dbf21b1ca80f1505d916df9fb8bcd380128e4f3d Mon Sep 17 00:00:00 2001
From: Henning Stahlke <github@henningstahlke.de>
Date: Sat, 11 Mar 2017 22:41:57 +0100
Subject: [PATCH] YASim calculate max CG range (on x-axis) from gear positions,
 to implement checks later (a better guesstimate will follow).

---
 src/FDM/YASim/Airplane.cpp | 21 +++++++++++++++++++++
 src/FDM/YASim/Airplane.hpp |  9 ++++++++-
 src/FDM/YASim/FGFDM.cpp    |  5 +++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/FDM/YASim/Airplane.cpp b/src/FDM/YASim/Airplane.cpp
index 767e07cec..e5e4e1845 100644
--- a/src/FDM/YASim/Airplane.cpp
+++ b/src/FDM/YASim/Airplane.cpp
@@ -57,6 +57,8 @@ Airplane::Airplane()
 
     _failureMsg = 0;
     _wingsN = 0;
+    _cgMaxX = -1e6;
+    _cgMinX = 1e6;
 }
 
 Airplane::~Airplane()
@@ -238,6 +240,10 @@ void Airplane::addGear(Gear* gear)
     g->gear = gear;
     g->surf = 0;
     _gears.add(g);
+    float pos[3];
+    g->gear->getPosition(pos);
+    if (pos[0] > _cgMaxX) _cgMaxX = pos[0];
+    if (pos[0] < _cgMinX) _cgMinX = pos[0];
 }
 
 void Airplane::addThruster(Thruster* thruster, float mass, float* cg)
@@ -320,6 +326,14 @@ void Airplane::setupState(const float aoa, const float speed, const float gla, S
     s->pos[2] = 1;
 }
 
+/**
+ * @brief add contact point for crash detection 
+ * used to add wingtips and fuselage nose and tail
+ * 
+ * @param pos ...
+ * @return void
+ */
+
 void Airplane::addContactPoint(float* pos)
 {
     ContactRec* c = new ContactRec;
@@ -522,6 +536,13 @@ void Airplane::compileGear(GearRec* gr)
     _surfs.add(s);
 }
 
+/**
+ * @brief add "fake gear" per contact point
+ * 
+ * 
+ * @return void
+ */
+
 void Airplane::compileContactPoints()
 {
     // Figure it will compress by 20cm
diff --git a/src/FDM/YASim/Airplane.hpp b/src/FDM/YASim/Airplane.hpp
index 3d98c2358..43e570778 100644
--- a/src/FDM/YASim/Airplane.hpp
+++ b/src/FDM/YASim/Airplane.hpp
@@ -102,7 +102,10 @@ public:
     static void setupState(const float aoa, const float speed, const float gla, yasim::State* s); // utility
     void loadApproachControls();
     void loadCruiseControls();
-
+    
+    float getCGMinX() { return _cgMinX; }
+    float getCGMaxX() { return _cgMaxX; }
+    
 private:
     struct Tank { float pos[3]; float cap; float fill;
 	          float density; int handle; };
@@ -182,6 +185,10 @@ private:
     float _tailIncidence;
     Control _approachElevator;
     const char* _failureMsg;
+
+    // hard limits for cg from gear positions
+    float _cgMaxX;
+    float _cgMinX;
 };
 
 }; // namespace yasim
diff --git a/src/FDM/YASim/FGFDM.cpp b/src/FDM/YASim/FGFDM.cpp
index 28942e81e..5f21f67e1 100644
--- a/src/FDM/YASim/FGFDM.cpp
+++ b/src/FDM/YASim/FGFDM.cpp
@@ -130,7 +130,12 @@ void FGFDM::init()
     // alias to older name
     fgGetNode("/yasim/gross-weight-lbs", true)->alias(_gross_weight_lbs);
 
+    // write some compile time information to property tree
     _yasimN->getNode("config-version",true)->setIntValue(_airplane.getVersion());
+    _yasimN->getNode("model/cg-x-min",true)->setFloatValue(_airplane.getCGMinX());
+    _yasimN->getNode("model/cg-x-max",true)->setFloatValue(_airplane.getCGMaxX());
+    
+    // prepare nodes for write at runtime
     _cg_x = _yasimN->getNode("cg-x-m", true);
     _cg_y = _yasimN->getNode("cg-y-m", true);
     _cg_z = _yasimN->getNode("cg-z-m", true);