Turn Indicator:

* revert to old default power supply path (/systems/electrical/outputs/turn-coordinator instead of .../turn-indicator) for compatibility reasons
* fix property instrumentation/turn-indicator/spin not being updated

src/Instrumentation/turn_indicator.cxx

@@ -26,6 +26,9 @@ using std::string;
 TurnIndicator::TurnIndicator ( SGPropertyNode *node) :
     _last_rate(0)
 {
+    if( !node->getBoolValue("new-default-power-path", 0) ){
+       setDefaultPowerSupplyPath("/systems/electrical/outputs/turn-coordinator");
+    }
     readConfig(node, "turn-indicator");
 }
 
@@ -42,6 +45,7 @@ TurnIndicator::init ()
     _roll_rate_node = fgGetNode("/orientation/roll-rate-degps", true);
     _yaw_rate_node = fgGetNode("/orientation/yaw-rate-degps", true);
     _rate_out_node = node->getChild("indicated-turn-rate", 0, true);
+    _spin_node = node->getChild("spin", 0, true);
 
     initServicePowerProperties(node);
 
@@ -62,6 +66,7 @@ TurnIndicator::update (double dt)
     _gyro.set_power_norm(isServiceableAndPowered());
     _gyro.update(dt);
     double spin = _gyro.get_spin_norm();
+    _spin_node->setDoubleValue( spin );
 
                                 // Calculate the indicated rate
     double factor = 1.0 - ((1.0 - spin) * (1.0 - spin) * (1.0 - spin));

src/Instrumentation/turn_indicator.hxx

@@ -32,11 +32,33 @@
  * /instrumentation/"name"/spin
  * /orientation/roll-rate-degps
  * /orientation/yaw-rate-degps
- * /systems/electrical/outputs/turn-coordinator
+ * /systems/electrical/outputs/turn-coordinator (see below)
  *
  * Output properties:
  *
  * /instrumentation/"name"/indicated-turn-rate
+ * 
+ * Configuration:
+ * 
+ *   name
+ *   number
+ *   new-default-power-path: use /systems/electrical/outputs/turn-indicator[ number ] instead of 
+ *                           /systems/electrical/outputs/turn-coordinator as the default power
+ *                           supply path (not used when power-supply is set)
+ *   power-supply
+ *   minimum-supply-volts
+ * 
+ * Notes on the power supply path:
+ *   
+ *   For backwards compatibility reasons, the default power path is 
+ *   /systems/electrical/outputs/turn-coordinator, unless new-default-power-path is set to 1,
+ *   in which case the new default path /systems/electrical/outputs/turn-indicator[ number ]
+ *   is used. As the new path is more logical and consistent with instrument naming, newly
+ *   developed and actively maintained aircraft should switch their electrical system to write
+ *   to /systems/electrical/outputs/turn-indicator[ number ] and set new-default-power-path.
+ *   The legacy default path will eventually be phased out.
+ *   The power path can always be set manually by using the power-supply config tag.
+ * 
  */
 class TurnIndicator : public AbstractInstrument
 {
@@ -45,10 +67,8 @@ public:
     virtual ~TurnIndicator ();
 
     // Subsystem API.
-    //void bind() override;
     void init() override;
     void reinit() override;
-    //void unbind() override;
     void update(double dt) override;
 
     // Subsystem identification.
@@ -61,4 +81,5 @@ private:
     SGPropertyNode_ptr _roll_rate_node;
     SGPropertyNode_ptr _yaw_rate_node;
     SGPropertyNode_ptr _rate_out_node;
+    SGPropertyNode_ptr _spin_node;
 };