diff --git a/ArduCopter/ArduCopter.pde b/ArduCopter/ArduCopter.pde
index fc1e70692f..c16fb988a9 100644
--- a/ArduCopter/ArduCopter.pde
+++ b/ArduCopter/ArduCopter.pde
@@ -1460,7 +1460,7 @@ void update_roll_pitch_mode(void)
 // new radio frame is used to make sure we only call this at 50hz
 void update_simple_mode(void)
 {
-	float simple_sin_y=0, simple_cos_x=0;
+	static float simple_sin_y=0, simple_cos_x=0;
 
 	// used to manage state machine
 	// which improves speed of function