don't allow others to delete our property node

diff --git a/src/FDM/UFO.hxx b/src/FDM/UFO.hxx
index 0a16d455dc4b8c6fef905500c24e8697374a52dd..6f522dad9d7fdb5442b48aaabe0891bf6e392056 100644 (file)
--- a/src/FDM/UFO.hxx
+++ b/src/FDM/UFO.hxx
@@ -34,7 +34,7 @@ class FGUFO: public FGInterface {
     double Elevator;
     double Elevator_Trim;
     double Rudder;
-    SGPropertyNode *Speed_Max;
+    SGPropertyNode_ptr Speed_Max;
 
 public:
     FGUFO( double dt );