diff --git a/src/Instrumentation/airspeed_indicator.cxx b/src/Instrumentation/airspeed_indicator.cxx
index 0196ddbae..0622f2103 100644
--- a/src/Instrumentation/airspeed_indicator.cxx
+++ b/src/Instrumentation/airspeed_indicator.cxx
@@ -10,6 +10,8 @@
 #include "airspeed_indicator.hxx"
 #include <Main/fg_props.hxx>
 #include <Main/util.hxx>
+#include <Environment/environment_mgr.hxx>
+#include <Environment/environment.hxx>
 
 
 // A higher number means more responsive.
@@ -20,8 +22,14 @@ AirspeedIndicator::AirspeedIndicator ( SGPropertyNode *node )
     _name(node->getStringValue("name", "airspeed-indicator")),
     _num(node->getIntValue("number", 0)),
     _total_pressure(node->getStringValue("total-pressure", "/systems/pitot/total-pressure-inhg")),
-    _static_pressure(node->getStringValue("static-pressure", "/systems/static/pressure-inhg"))
+    _static_pressure(node->getStringValue("static-pressure", "/systems/static/pressure-inhg")),
+    _has_overspeed(node->getBoolValue("has-overspeed-indicator",false)),
+    _pressure_alt_source(node->getStringValue("pressure-alt-source", "/instrumentation/altimeter/pressure-alt-ft")),
+    _ias_limit(node->getDoubleValue("ias-limit", 248.0)),
+    _mach_limit(node->getDoubleValue("mach-limit", 0.48)),
+    _alt_threshold(node->getDoubleValue("alt-threshold", 13200))
 {
+  _environmentManager = NULL;
 }
 
 AirspeedIndicator::~AirspeedIndicator ()
@@ -40,6 +48,32 @@ AirspeedIndicator::init ()
     _static_pressure_node = fgGetNode(_static_pressure.c_str(), true);
     _density_node = fgGetNode("/environment/density-slugft3", true);
     _speed_node = node->getChild("indicated-speed-kt", 0, true);
+    _tas_node = node->getChild("true-speed-kt", 0, true);
+    _mach_node = node->getChild("indicated-mach", 0, true);
+    
+  // overspeed-indicator properties
+    if (_has_overspeed) {
+        _ias_limit_node = node->getNode("ias-limit",0, true);
+        _mach_limit_node = node->getNode("mach-limit",0, true);
+        _alt_threshold_node = node->getNode("alt-threshold",0, true);
+        
+        if (!_ias_limit_node->hasValue()) {
+          _ias_limit_node->setDoubleValue(_ias_limit);
+        }
+
+        if (!_mach_limit_node->hasValue()) {
+          _mach_limit_node->setDoubleValue(_mach_limit);
+        }
+
+        if (!_alt_threshold_node->hasValue()) {
+          _alt_threshold_node->setDoubleValue(_alt_threshold);
+        }
+
+        _airspeed_limit = node->getChild("airspeed-limit-kt", 0, true);
+        _pressure_alt = fgGetNode(_pressure_alt_source.c_str(), true);
+    }
+    
+    _environmentManager = (FGEnvironmentMgr*) globals->get_subsystem("environment");
 }
 
 #ifndef FPSTOKTS
@@ -53,24 +87,66 @@ AirspeedIndicator::init ()
 void
 AirspeedIndicator::update (double dt)
 {
-    if (_serviceable_node->getBoolValue()) {
-        double pt = _total_pressure_node->getDoubleValue() * INHGTOPSF;
-        double p = _static_pressure_node->getDoubleValue() * INHGTOPSF;
-        double r = _density_node->getDoubleValue();
-        double q = ( pt - p );  // dynamic pressure
-
-        // Now, reverse the equation (normalize dynamic pressure to
-        // avoid "nan" results from sqrt)
-        if ( q < 0 ) { q = 0.0; }
-        double v_fps = sqrt((2 * q) / r);
-
-                                // Publish the indicated airspeed
-        double last_speed_kt = _speed_node->getDoubleValue();
-        double current_speed_kt = v_fps * FPSTOKTS;
-        _speed_node->setDoubleValue(fgGetLowPass(last_speed_kt,
-                                                 current_speed_kt,
-                                                 dt * RESPONSIVENESS));
+    if (!_serviceable_node->getBoolValue()) {
+        return;
     }
+    
+    double pt = _total_pressure_node->getDoubleValue() * INHGTOPSF;
+    double p = _static_pressure_node->getDoubleValue() * INHGTOPSF;
+    double r = _density_node->getDoubleValue();
+    double q = ( pt - p );  // dynamic pressure
+
+    // Now, reverse the equation (normalize dynamic pressure to
+    // avoid "nan" results from sqrt)
+    if ( q < 0 ) { q = 0.0; }
+    double v_fps = sqrt((2 * q) / r);
+
+                            // Publish the indicated airspeed
+    double last_speed_kt = _speed_node->getDoubleValue();
+    double current_speed_kt = v_fps * FPSTOKTS;
+    double filtered_speed = fgGetLowPass(last_speed_kt,
+                                             current_speed_kt,
+                                             dt * RESPONSIVENESS);
+    _speed_node->setDoubleValue(filtered_speed);
+    computeMach(filtered_speed);
+
+    if (!_has_overspeed) {
+        return;
+    }
+    
+    double lmt = _ias_limit_node->getDoubleValue();
+    if (_pressure_alt->getDoubleValue() > _alt_threshold_node->getDoubleValue()) {
+        double mmo = _mach_limit_node->getDoubleValue();
+        lmt = (filtered_speed/_mach_node->getDoubleValue())* mmo;
+    }
+    
+    _airspeed_limit->setDoubleValue(lmt);
+}
+
+void
+AirspeedIndicator::computeMach(double ias)
+{
+  if (!_environmentManager) {
+    return;
+  }
+  
+  FGEnvironment env(_environmentManager->getEnvironment());
+  
+  // derived from http://williams.best.vwh.net/avform.htm#Mach
+  // names here are picked to be consistent with those formulae!
+
+  double oatK = env.get_temperature_degc() + 273.15; // OAT in Kelvin
+  double CS = 38.967854 * sqrt(oatK); // speed-of-sound in knots at altitude
+  double CS_0 = 661.4786; // speed-of-sound in knots at sea-level
+  double P_0 = env.get_pressure_sea_level_inhg();
+  double P = _static_pressure_node->getDoubleValue();
+  
+  double DP = P_0 * (pow(1 + 0.2*pow(ias/CS_0, 2), 3.5) - 1);
+  double mach = pow(5 * ( pow(DP/P + 1, 2.0/7.0) -1) , 0.5);
+  
+  // publish Mach and TAS
+  _mach_node->setDoubleValue(mach);
+  _tas_node->setDoubleValue(CS * mach);
 }
 
 // end of airspeed_indicator.cxx
diff --git a/src/Instrumentation/airspeed_indicator.hxx b/src/Instrumentation/airspeed_indicator.hxx
index e4827081d..41e544c66 100644
--- a/src/Instrumentation/airspeed_indicator.hxx
+++ b/src/Instrumentation/airspeed_indicator.hxx
@@ -14,6 +14,8 @@
 #include <simgear/props/props.hxx>
 #include <simgear/structure/subsystem_mgr.hxx>
 
+// forward decls
+class FGEnvironmentMgr;
 
 /**
  * Model an airspeed indicator tied to the pitot and static ports.
@@ -41,17 +43,32 @@ public:
     virtual void update (double dt);
 
 private:
+    void computeMach(double ias);
 
     string _name;
     unsigned int _num;
     string _total_pressure;
     string _static_pressure;
+    bool _has_overspeed;
+    string _pressure_alt_source;
+    double _ias_limit;
+    double _mach_limit;
+    double _alt_threshold;
+    
+    SGPropertyNode_ptr _ias_limit_node;
+    SGPropertyNode_ptr _mach_limit_node;
+    SGPropertyNode_ptr _alt_threshold_node;
     SGPropertyNode_ptr _serviceable_node;
     SGPropertyNode_ptr _total_pressure_node;
     SGPropertyNode_ptr _static_pressure_node;
     SGPropertyNode_ptr _density_node;
     SGPropertyNode_ptr _speed_node;
+    SGPropertyNode_ptr _airspeed_limit;
+    SGPropertyNode_ptr _pressure_alt;
+    SGPropertyNode_ptr _mach_node;
+    SGPropertyNode_ptr _tas_node;
     
+    FGEnvironmentMgr* _environmentManager;
 };
 
 #endif // __INSTRUMENTS_AIRSPEED_INDICATOR_HXX
diff --git a/src/Instrumentation/dme.cxx b/src/Instrumentation/dme.cxx
index 754008bd4..925681e0a 100644
--- a/src/Instrumentation/dme.cxx
+++ b/src/Instrumentation/dme.cxx
@@ -97,6 +97,7 @@ DME::update (double delta_time_sec)
         _time_before_search_sec = 0;
         _last_frequency_mhz = frequency_mhz;
     }
+    _frequency_node->setDoubleValue(frequency_mhz);
 
                                 // Get the aircraft position
     double longitude_rad =