diff --git a/libraries/AC_Autorotation/AC_Autorotation.cpp b/libraries/AC_Autorotation/AC_Autorotation.cpp
index 3ff226e010c799..3539310f807e5f 100644
--- a/libraries/AC_Autorotation/AC_Autorotation.cpp
+++ b/libraries/AC_Autorotation/AC_Autorotation.cpp
@@ -723,15 +723,17 @@ void AC_Autorotation::update_est_radar_alt(void)
 }
 
 
-void AC_Autorotation::calc_avg_acc_z(void)
+void AC_Autorotation::update_avg_acc_z(void)
 {
-    if (_index < 10) {
-        _acc_z_sum -= _curr_acc_z[_index];
-        _curr_acc_z[_index] = _ahrs.get_accel_ef().z;
-        _acc_z_sum += _curr_acc_z[_index];
-        _index = _index + 1;
-    } else {
+    // Wrap index
+    if (_index >= 10) {
         _index = 0;
     }
-    _avg_acc_z = _acc_z_sum / 10.0f;
+
+    _acc_z_sum -= _curr_acc_z[_index];
+    _curr_acc_z[_index] = _ahrs.get_accel_ef().z;
+    _acc_z_sum += _curr_acc_z[_index];
+    _index = _index + 1;
+
+    _avg_acc_z = _acc_z_sum / 10.0;
 }
diff --git a/libraries/AC_Autorotation/AC_Autorotation.h b/libraries/AC_Autorotation/AC_Autorotation.h
index f08ecc985424e5..7c8e0c2e9e4df9 100644
--- a/libraries/AC_Autorotation/AC_Autorotation.h
+++ b/libraries/AC_Autorotation/AC_Autorotation.h
@@ -108,7 +108,7 @@ class AC_Autorotation
 
     void update_hover_autorotation_controller();
 
-    void calc_avg_acc_z(void);
+    void update_avg_acc_z(void);
 
     float get_flare_alt(void) const { return _flare_alt_calc; }