########## STEP 1 .....
  First patch the source tree with the following patch set.
  Then recompile.  This should be 100% compatible with the
  existing source, data, aircraft, et cetera.  Then proceed
  to the next step.
Index: src/Instrumentation/heading_indicator_fg.cxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/Instrumentation/heading_indicator_fg.cxx,v
retrieving revision 1.2
diff -u -r1.2 heading_indicator_fg.cxx
--- src/Instrumentation/heading_indicator_fg.cxx	24 Oct 2006 16:03:44 -0000	1.2
+++ src/Instrumentation/heading_indicator_fg.cxx	1 Feb 2007 17:12:18 -0000
@@ -61,7 +61,7 @@
     _heading_out_node = node->getChild("indicated-heading-deg", 0, true);
     _last_heading_deg = (_heading_in_node->getDoubleValue() +
                          _offset_node->getDoubleValue());
-	_electrical_node = fgGetNode("/systems/electrical/outputs/DG", true);
+	_electrical_node = fgGetNode("/systems/electrical/outputs/hsi", true);
 }
 
 void
Index: src/Instrumentation/heading_indicator_dg.cxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/Instrumentation/heading_indicator_dg.cxx,v
retrieving revision 1.2
diff -u -r1.2 heading_indicator_dg.cxx
--- src/Instrumentation/heading_indicator_dg.cxx	24 Oct 2006 16:03:44 -0000	1.2
+++ src/Instrumentation/heading_indicator_dg.cxx	1 Feb 2007 17:12:19 -0000
@@ -62,7 +62,7 @@
     _heading_out_node = node->getChild("indicated-heading-deg", 0, true);
     _last_heading_deg = (_heading_in_node->getDoubleValue() +
                          _offset_node->getDoubleValue());
-    _electrical_node = fgGetNode("/systems/electrical/outputs/DG", true);
+    _electrical_node = fgGetNode("/systems/electrical/outputs/hsi", true);
 }
 
 void



########### STEP 2 .....
  After you have patched and recompiled the source tree,
  patch the data tree as follows.  This will fix things
  so that the hsi properly responds to the relevant
  serviceability flag.
Index: Aircraft/Instruments/hsi.xml
===================================================================
RCS file: /var/cvs/FlightGear-0.9/data/Aircraft/Instruments/hsi.xml,v
retrieving revision 1.13
diff -u -r1.13 hsi.xml
--- Aircraft/Instruments/hsi.xml	28 Jan 2005 15:11:56 -0000	1.13
+++ Aircraft/Instruments/hsi.xml	1 Feb 2007 17:12:20 -0000
@@ -31,7 +31,7 @@
      <transformations>
       <transformation>
       <type>rotation</type>
-      <property>/orientation/heading-magnetic-deg</property>
+      <property>/instrumentation/heading-indicator-fg/indicated-heading-deg</property>
       <min>-360.0</min>
       <max>360.0</max>
       <scale>-1.0</scale>
@@ -92,7 +92,7 @@
    <transformations>
     <transformation>
     <type>rotation</type>
-    <property>/orientation/heading-magnetic-deg</property>
+    <property>/instrumentation/heading-indicator-fg/indicated-heading-deg</property>
     <min>-360.0</min>
     <max>360.0</max>
     <scale>-1.0</scale>
@@ -157,7 +157,7 @@
     <transformations>
      <transformation>
      <type>rotation</type>
-     <property>/orientation/heading-magnetic-deg</property>
+     <property>/instrumentation/heading-indicator-fg/indicated-heading-deg</property>
      <min>-360.0</min>
      <max>360.0</max>
      <scale>-1.0</scale>
@@ -186,7 +186,7 @@
    <transformations>
     <transformation>
     <type>rotation</type>
-    <property>/orientation/heading-magnetic-deg</property>
+    <property>/instrumentation/heading-indicator-fg/indicated-heading-deg</property>
     <min>-360.0</min>
     <max>360.0</max>
     <scale>-1.0</scale>
@@ -286,7 +286,7 @@
     </transformation>
     <transformation>
      <type>rotation</type>
-     <property>/instrumentation/heading-indicator/indicated-heading-deg</property>
+     <property>/instrumentation/heading-indicator-fg/indicated-heading-deg</property>
      <min>-360.0</min>
      <max>360.0</max>
      <scale>-1.0</scale>
Index: gui/dialogs/instrument-failures.xml
===================================================================
RCS file: /var/cvs/FlightGear-0.9/data/gui/dialogs/instrument-failures.xml,v
retrieving revision 1.3
diff -u -r1.3 instrument-failures.xml
--- gui/dialogs/instrument-failures.xml	5 Nov 2005 18:42:28 -0000	1.3
+++ gui/dialogs/instrument-failures.xml	1 Feb 2007 17:12:21 -0000
@@ -134,6 +134,13 @@
     <command>dialog-apply</command>
    </binding>
    <binding>
+    <command>nasal</command>
+    <script>
+      setprop("/instrumentation/heading-indicator-fg/serviceable",
+	 getprop("/instrumentation/heading-indicator/serviceable"));
+    </script>
+   </binding>
+   <binding>
     <command>dialog-close</command>
    </binding>
   </button>
@@ -146,6 +153,13 @@
    <binding>
     <command>dialog-apply</command>
    </binding>
+   <binding>
+    <command>nasal</command>
+    <script>
+      setprop("/instrumentation/heading-indicator-fg/serviceable",
+	 getprop("/instrumentation/heading-indicator/serviceable"));
+    </script>
+   </binding>
   </button>
 
   <button>
Index: Aircraft/Generic/generic-instrumentation.xml
===================================================================
RCS file: /var/cvs/FlightGear-0.9/data/Aircraft/Generic/generic-instrumentation.xml,v
retrieving revision 1.8
diff -u -r1.8 generic-instrumentation.xml
--- Aircraft/Generic/generic-instrumentation.xml	6 Dec 2006 22:15:04 -0000	1.8
+++ Aircraft/Generic/generic-instrumentation.xml	1 Feb 2007 17:12:22 -0000
@@ -76,6 +76,12 @@
     <suction>/systems/vacuum/suction-inhg</suction>
   </heading-indicator>
 
+  <heading-indicator-fg>
+    <name>heading-indicator-fg</name>
+    <number>0</number>
+    <suction>/systems/vacuum/suction-inhg</suction>
+  </heading-indicator-fg>
+
   <KT-70>
     <name>kt-70</name>
     <number>0</number>