diff --git a/libraries/AP_Motors/AP_MotorsHeli.cpp b/libraries/AP_Motors/AP_MotorsHeli.cpp
index 7f62e63503..7ca05c7d2a 100644
--- a/libraries/AP_Motors/AP_MotorsHeli.cpp
+++ b/libraries/AP_Motors/AP_MotorsHeli.cpp
@@ -204,6 +204,7 @@ void AP_MotorsHeli::output()
     update_throttle_filter();
 
     if (_flags.armed) {
+        calculate_armed_scalars();
         if (!_flags.interlock) {
             output_armed_zero_throttle();
         } else if (_flags.stabilizing) {
diff --git a/libraries/AP_Motors/AP_MotorsHeli.h b/libraries/AP_Motors/AP_MotorsHeli.h
index 02ef8cd62f..3daba60fc5 100644
--- a/libraries/AP_Motors/AP_MotorsHeli.h
+++ b/libraries/AP_Motors/AP_MotorsHeli.h
@@ -136,6 +136,9 @@ public:
     // calculate_scalars - must be implemented by child classes
     virtual void calculate_scalars() = 0;
 
+    // calculate_armed_scalars - must be implemented by child classes
+    virtual void calculate_armed_scalars() = 0;
+    
     // var_info for holding Parameter information
     static const struct AP_Param::GroupInfo var_info[];
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Single.cpp b/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
index 8434822913..b079d89efa 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
+++ b/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
@@ -218,6 +218,18 @@ void AP_MotorsHeli_Single::set_desired_rotor_speed(int16_t desired_speed)
     _tail_rotor.set_desired_speed(_direct_drive_tailspeed);
 }
 
+// calculate_scalars - recalculates various scalers used.
+void AP_MotorsHeli_Single::calculate_armed_scalars()
+{
+    _main_rotor.set_ramp_time(_rsc_ramp_time);
+    _main_rotor.set_runup_time(_rsc_runup_time);
+    _main_rotor.set_critical_speed(_rsc_critical);
+    _main_rotor.set_idle_output(_rsc_idle_output);
+    _main_rotor.set_power_output_range(_rsc_power_low, _rsc_power_high);
+    _main_rotor.recalc_scalers();
+}
+
+
 // calculate_scalars - recalculates various scalers used.
 void AP_MotorsHeli_Single::calculate_scalars()
 {
@@ -244,13 +256,8 @@ void AP_MotorsHeli_Single::calculate_scalars()
 
     // send setpoints to main rotor controller and trigger recalculation of scalars
     _main_rotor.set_control_mode(static_cast<RotorControlMode>(_rsc_mode.get()));
-    _main_rotor.set_ramp_time(_rsc_ramp_time);
-    _main_rotor.set_runup_time(_rsc_runup_time);
-    _main_rotor.set_critical_speed(_rsc_critical);
-    _main_rotor.set_idle_output(_rsc_idle_output);
-    _main_rotor.set_power_output_range(_rsc_power_low, _rsc_power_high);
-    _main_rotor.recalc_scalers();
-
+    calculate_armed_scalars();
+    
     // send setpoints to tail rotor controller and trigger recalculation of scalars
     if (_tail_type == AP_MOTORS_HELI_SINGLE_TAILTYPE_DIRECTDRIVE_VARPITCH) {
         _tail_rotor.set_control_mode(ROTOR_CONTROL_MODE_SPEED_SETPOINT);
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Single.h b/libraries/AP_Motors/AP_MotorsHeli_Single.h
index e8cfbeadce..f4fa3cebdc 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Single.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_Single.h
@@ -95,6 +95,9 @@ public:
     // calculate_scalars - recalculates various scalars used
     void calculate_scalars();
 
+    // calculate_armed_scalars - recalculates scalars that can change while armed
+    void calculate_armed_scalars();
+    
     // get_motor_mask - returns a bitmask of which outputs are being used for motors or servos (1 means being used)
     //  this can be used to ensure other pwm outputs (i.e. for servos) do not conflict
     uint16_t get_motor_mask();