diff --git a/src/AIModel/AICarrier.cxx b/src/AIModel/AICarrier.cxx
index 1a9a1d2b7..979e9710b 100644
--- a/src/AIModel/AICarrier.cxx
+++ b/src/AIModel/AICarrier.cxx
@@ -514,7 +514,7 @@ void FGAICarrier::UpdateWind( double dt) {
     + (rel_wind_speed_from_north_kts * rel_wind_speed_from_north_kts));
 
     //calculate the relative wind direction
-    rel_wind_from_deg = atan(rel_wind_speed_from_east_kts/rel_wind_speed_from_north_kts)
+    rel_wind_from_deg = atan2(rel_wind_speed_from_east_kts, rel_wind_speed_from_north_kts)
                             * SG_RADIANS_TO_DEGREES;
 
     // rationalise the output
diff --git a/src/Environment/fgmetar.cxx b/src/Environment/fgmetar.cxx
index a543832e7..b2b331fbf 100644
--- a/src/Environment/fgmetar.cxx
+++ b/src/Environment/fgmetar.cxx
@@ -99,6 +99,8 @@ FGMetar::FGMetar(const string& icao, const string& proxy, const string& port, co
 		_wind_range_from = _wind_range_to = _wind_dir;
 	}
 
+	if (_wind_speed == SGMetarNaN)
+		_wind_speed = 0.0;
 	if (_gust_speed == SGMetarNaN)
 		_gust_speed = 0.0;
 
diff --git a/src/FDM/YASim/PistonEngine.cpp b/src/FDM/YASim/PistonEngine.cpp
index 11b04fe7a..b032342d4 100644
--- a/src/FDM/YASim/PistonEngine.cpp
+++ b/src/FDM/YASim/PistonEngine.cpp
@@ -169,7 +169,7 @@ void PistonEngine::calc(float pressure, float temp, float speed)
     // pressure change can be assumed to be adiabatic.  Calculate a
     // temperature change, and use that to get the density.
     // Note: need to model intercoolers here...
-    float T = temp * Math::pow(_mp/pressure, 2.0/7.0);
+    float T = temp * Math::pow((_mp*_mp)/(pressure*pressure), 1.0/7.0);
     float rho = _mp / (287.1f * T);
 
     // The actual fuel flow is determined only by engine RPM and the
diff --git a/src/Main/CameraGroup.cxx b/src/Main/CameraGroup.cxx
index 2ff1bb169..c8e23c229 100644
--- a/src/Main/CameraGroup.cxx
+++ b/src/Main/CameraGroup.cxx
@@ -219,9 +219,11 @@ void CameraGroup::update(const osg::Vec3d& position,
 
 void CameraGroup::setCameraParameters(float vfov, float aspectRatio)
 {
-    _viewer->getCamera()->setProjectionMatrixAsPerspective(vfov,
-                                                           1.0f / aspectRatio,
-                                                           _zNear, _zFar);
+    if (vfov != 0.0f && aspectRatio != 0.0f)
+        _viewer->getCamera()
+            ->setProjectionMatrixAsPerspective(vfov,
+                                               1.0f / aspectRatio,
+                                               _zNear, _zFar);
 }
 }