Syd Adams:

add ias-limit (brarber-pole) computation to airpseed-indicator
    expose selected DME frequency on the DME instrument

src/Instrumentation/airspeed_indicator.cxx

@@ -20,7 +20,8 @@ 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_barber_pole(node->getBoolValue("has-barber-pole",false))
 {
 }
 
@@ -40,6 +41,17 @@ 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);
+    
+  // barber-pole properties
+    _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);
+    _airspeed_limit = node->getChild("airspeed-limit-kt", 0, true);
+    
+    string paSource = node->getStringValue("pressure-alt-source",
+      "/instrumentation/altimeter/pressure-alt-ft");
+    _pressure_alt = fgGetNode(paSource.c_str(), true);
+    _mach = fgGetNode("/velocities/mach", true);
 }
 
 #ifndef FPSTOKTS
@@ -53,24 +65,39 @@ 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);
+
+    if (!_has_barber_pole) {
+        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->getDoubleValue())* mmo;
+    }
+    
+    _airspeed_limit->setDoubleValue(lmt);
 }
 
 // end of airspeed_indicator.cxx

src/Instrumentation/airspeed_indicator.hxx

@@ -46,12 +46,18 @@ private:
     unsigned int _num;
     string _total_pressure;
     string _static_pressure;
+    bool _has_barber_pole;
+    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;
 };
 
 #endif // __INSTRUMENTS_AIRSPEED_INDICATOR_HXX

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 =