Intercept errors in the matrix inversion routine and report the faulty aircraft in the log.

src/FDM/AIWake/AIWakeGroup.cxx

@@ -47,7 +47,8 @@ void AIWakeGroup::AddAI(FGAIAircraft* ai)
     if (_aiWakeData.find(id) == _aiWakeData.end()) {
         double span = perfData->wingSpan();
         double chord = perfData->wingChord();
-        _aiWakeData[id] = AIWakeData(new WakeMesh(span, chord));
+        _aiWakeData[id] = AIWakeData(new WakeMesh(span, chord,
+                                     std::string("AI:") + ai->_getName()));
 
         SG_LOG(SG_FLIGHT, SG_DEV_ALERT,
                "Created mesh for " << ai->_getName() << " ID: #" << id);

src/FDM/AIWake/AircraftMesh.cxx

@@ -37,8 +37,8 @@ extern "C" {
 #include "../LaRCsim/ls_matrix.h"
 }
 
-AircraftMesh::AircraftMesh(double _span, double _chord)
+AircraftMesh::AircraftMesh(double _span, double _chord, const std::string& name)
-    : WakeMesh(_span, _chord)
+    : WakeMesh(_span, _chord, name)
 {
     collPt.resize(nelm, SGVec3d::zeros());
     midPt.resize(nelm, SGVec3d::zeros());

src/FDM/AIWake/AircraftMesh.hxx

@@ -32,7 +32,7 @@ class AIWakeGroup;
 
 class AircraftMesh : public WakeMesh {
 public:
-    AircraftMesh(double _span, double _chord);
+    AircraftMesh(double _span, double _chord, const std::string& name);
     void setPosition(const SGVec3d& pos, const SGQuatd& orient);
     SGVec3d GetForce(const AIWakeGroup& wg, const SGVec3d& vel, double rho);
     const SGVec3d& GetMoment(void) const { return moment; };

src/FDM/AIWake/WakeMesh.cxx

@@ -25,13 +25,14 @@
 
 #include <simgear/structure/SGSharedPtr.hxx>
 #include <simgear/math/SGVec3.hxx>
+#include <simgear/debug/logstream.hxx>
 
 #include "WakeMesh.hxx"
 extern "C" {
 #include "../LaRCsim/ls_matrix.h"
 }
 
-WakeMesh::WakeMesh(double _span, double _chord)
+WakeMesh::WakeMesh(double _span, double _chord, const std::string& aircraft_name)
     : nelm(10), span(_span), chord(_chord)
 {
     double y1 = -0.5*span;
@@ -59,7 +60,20 @@ WakeMesh::WakeMesh(double _span, double _chord)
     }
 
     // Compute the inverse matrix with the Gauss-Jordan algorithm
-    nr_gaussj(influenceMtx, nelm, 0, 0);
+    int ret = nr_gaussj(influenceMtx, nelm, nullptr, 0);
+    if (ret) {
+        // Something went wrong with the matrix inversion.
+
+        // 1. Nullify the influence matrix to disable the current aircraft wake.
+        for (int i=0; i < nelm; ++i) {
+            for (int j=0; j < nelm; ++j)
+                influenceMtx[i+1][j+1] = 0.0;
+        }
+        // 2. Report the issue in the log.
+        SG_LOG(SG_FLIGHT, SG_WARN,
+                "Failed to build wake mesh. " << aircraft_name << " ( span:"
+                << _span << ", chord:" << _chord << ") wake will be ignored.");
+    }
 }
 
 WakeMesh::~WakeMesh()

src/FDM/AIWake/WakeMesh.hxx

@@ -30,7 +30,7 @@ namespace FGTestApi { namespace PrivateAccessor { namespace FDM { class Accessor
 
 class WakeMesh : public SGReferenced {
 public:
-    WakeMesh(double _span, double _chord);
+    WakeMesh(double _span, double _chord, const std::string& aircraft_name);
     virtual ~WakeMesh();
     double computeAoA(double vel, double rho, double weight);
     SGVec3d getInducedVelocityAt(const SGVec3d& at) const;

src/FDM/JSBSim/JSBSim.cxx

@@ -367,7 +367,8 @@ FGJSBsim::FGJSBsim( double dt )
     crashed = false;
 
     mesh = new AircraftMesh(fgGetDouble("/fdm/jsbsim/metrics/bw-ft"),
-                            fgGetDouble("/fdm/jsbsim/metrics/cbarw-ft"));
+                            fgGetDouble("/fdm/jsbsim/metrics/cbarw-ft"),
+                            fdmex->GetModelName());
 
     // Trim once to initialize all output parameters
     FGTrim *fgtrim = new FGTrim(fdmex,tFull);