Fix for stop playing engine sound when scenario is going to disable

addon-menubar-items.xml

@@ -43,11 +43,6 @@
                     <property>/addons/by-id/org.flightgear.addons.Aerotow/addon-devel/ai-model</property>
                     <value type="string">Cub</value>
                 </binding>
-                <binding>
-                    <command>property-assign</command>
-                    <property>/addons/by-id/org.flightgear.addons.Aerotow/addon-devel/sound/enable</property>
-                    <value type="bool">true</value>
-                </binding>
             </item>
             <item>
                 <label>Call for Robin DR400 aircraft</label>
@@ -56,11 +51,6 @@
                     <property>/addons/by-id/org.flightgear.addons.Aerotow/addon-devel/ai-model</property>
                     <value type="string">DR400</value>
                 </binding>
-                <binding>
-                    <command>property-assign</command>
-                    <property>/addons/by-id/org.flightgear.addons.Aerotow/addon-devel/sound/enable</property>
-                    <value type="bool">true</value>
-                </binding>
             </item>
             <item>
                 <label>Call for Cessna 182 aircraft</label>
@@ -69,11 +59,6 @@
                     <property>/addons/by-id/org.flightgear.addons.Aerotow/addon-devel/ai-model</property>
                     <value type="string">c182</value>
                 </binding>
-                <binding>
-                    <command>property-assign</command>
-                    <property>/addons/by-id/org.flightgear.addons.Aerotow/addon-devel/sound/enable</property>
-                    <value type="bool">true</value>
-                </binding>
             </item>
             <item>
                 <label>Disable tow aircraft</label>
@@ -84,7 +69,14 @@
                 </binding>
                 <binding>
                     <command>nasal</command>
-                    <script><![CDATA[aerotow.stopAerotow();]]></script>
+                    <script><![CDATA[
+                        # Run stopAerotow() with a delay to ensure that the engine sound turns off
+                        var timer = maketimer(1, func () {
+                            aerotow.stopAerotow();
+                        });
+                        timer.singleShot = 1;
+                        timer.start();
+                    ]]></script>
                 </binding>
             </item>
             <item>

aerotow.nas

@@ -41,7 +41,7 @@ var g_towListeners = [];
 var init = func () {
     # Listener for ai-model property triggered when the user select a tow aircraft from add-on menu
     append(g_towListeners, setlistener(ADDON_NODE_PATH ~ "/addon-devel/ai-model", func () {
-        startAerotow();
+        restartAerotow();
     }));
 
     append(g_towListeners, setlistener("/sim/presets/longitude-deg", func () {
@@ -104,6 +104,44 @@ var uninit = func () {
     }
 }
 
+#
+# Function for restart AI scenario with delay when the sound has to stop.
+#
+# Return 1 on successful, otherwise 0.
+#
+var restartAerotow = func () {
+    messages.displayOk("Aerotow in the way");
+
+    # Stop playing engine sound
+    setprop(ADDON_NODE_PATH ~ "/addon-devel/sound/enable", 0);
+
+    # Wait a second for the engine sound to turn off
+    var timer = maketimer(1, func () {
+        unloadScenario();
+    });
+    timer.singleShot = 1;
+    timer.start();
+}
+
+#
+# Unload scenario and start a new one
+#
+var unloadScenario = func () {
+    if (g_isScenarioLoaded) {
+        var args = props.Node.new({ "name": SCENARIO_ID });
+        if (fgcommand("unload-scenario", args)) {
+            g_isScenarioLoaded = 0;
+        }
+    }
+
+    # Start aerotow with delay to avoid duplicate engine sound playing
+    var timer = maketimer(1, func () {
+        startAerotow();
+    });
+    timer.singleShot = 1;
+    timer.start();
+}
+
 #
 # Main function to prepare AI scenario and run it.
 #
@@ -111,8 +149,11 @@ var uninit = func () {
 #
 var startAerotow = func () {
     var args = props.Node.new({ "name": SCENARIO_ID });
+
     if (g_isScenarioLoaded) {
-        fgcommand("unload-scenario", args);
+        if (fgcommand("unload-scenario", args)) {
+            g_isScenarioLoaded = 0;
+        }
     }
 
     generateScenarioXml();
@@ -124,6 +165,8 @@ var startAerotow = func () {
     if (fgcommand("load-scenario", args)) {
         g_isScenarioLoaded = 1;
         messages.displayOk("Let's fly!");
+
+        setprop(ADDON_NODE_PATH ~ "/addon-devel/sound/enable", 1);
         return 1;
     }