diff --git a/ArduCopter/config.h b/ArduCopter/config.h
index 2c1d0accad..3f1253ed22 100644
--- a/ArduCopter/config.h
+++ b/ArduCopter/config.h
@@ -670,7 +670,7 @@
 #endif
 
 #ifndef LOITER_RADIUS
-# define LOITER_RADIUS 10
+# define LOITER_RADIUS 10		// meters for circle mode
 #endif
 
 #ifndef ALT_HOLD_HOME