diff --git a/Nasal/canvas/MFD_Generic.nas b/Nasal/canvas/MFD_Generic.nas
index 98791620d..218b3e374 100644
--- a/Nasal/canvas/MFD_Generic.nas
+++ b/Nasal/canvas/MFD_Generic.nas
@@ -432,6 +432,14 @@ var PFD_NavDisplay =
         {
             if (!me.nd_initialised)
                 me.nd_init();
+            #2018.2 - manage the timer so that the nav display is only updated when visibile
+            me.NDCpt.onDisplay();
+        };
+        obj.offdisplay = func
+        {
+            #2018.2 - manage the timer so that the nav display is only updated when visibile
+            if (me.nd_initialised)
+              me.NDCpt.offDisplay();
         };
         #
         # most updates performed by the canvas nav display directly.
diff --git a/Nasal/canvas/map/navdisplay.mfd b/Nasal/canvas/map/navdisplay.mfd
index 89996f4c0..fc1066e6e 100644
--- a/Nasal/canvas/map/navdisplay.mfd
+++ b/Nasal/canvas/map/navdisplay.mfd
@@ -175,7 +175,8 @@ var NavDisplay = {
 	}, # of connectAI
 
 	setTimerInterval: func(update_time=0.05) me.update_timer.restart(update_time),
-
+    onDisplay: func {me.setTimerInterval();},
+    offDisplay: func {me.update_timer.stop();},
 	# TODO: the ctor should allow customization, for different aircraft
 	# especially properties and SVG files/handles (747, 757, 777 etc)
 	new : func(prop1, switches=default_switches, style='Boeing') {