diff --git a/libraries/AP_Motors/AP_MotorsHeli.h b/libraries/AP_Motors/AP_MotorsHeli.h
index 2ac1ff3c832953..5aab005fc8274f 100644
--- a/libraries/AP_Motors/AP_MotorsHeli.h
+++ b/libraries/AP_Motors/AP_MotorsHeli.h
@@ -286,8 +286,11 @@ class AP_MotorsHeli : public AP_Motors {
     AP_Float        _cyclic_angle_max_deg;      // The blade pitch angle angle contribution in degrees of the cyclic output contribution
 
     // internal variables
+    float           _collective_zero_thrust_pct;                             // collective zero thrust parameter value converted to 0 ~ 1 range
+    float           _collective_land_min_pct;                                // collective land min parameter value converted to 0 ~ 1 range
     float           _coll_ang_deg[AP_MOTORS_HELI_MAX_INDEPENDENT_COLL];      // collective blade pitch angle contributions for each swashplate after mixing
     float           _cyclic_ang_deg[AP_MOTORS_HELI_MAX_INDEPENDENT_CYCLIC];  // cyclic blade pitch angle contributions for each swashplate after mixing
+    uint8_t         _servo_test_cycle_counter = 0;                           // number of test cycles left to run after bootup
 
     motor_frame_type _frame_type;
     motor_frame_class _frame_class;
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Dual.cpp b/libraries/AP_Motors/AP_MotorsHeli_Dual.cpp
index 96a40d7089b10f..fc12a72637368a 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Dual.cpp
+++ b/libraries/AP_Motors/AP_MotorsHeli_Dual.cpp
@@ -422,7 +422,7 @@ void AP_MotorsHeli_Dual::move_actuators(float roll_out, float pitch_out, float c
             pitch_out = _cyclic_max/4500.0f;
             limit.pitch = true;
         }
-    } else {
+    } else { // AP_MOTORS_HELI_DUAL_MODE_TANDEM
         if (roll_out < -_cyclic_max/4500.0f) {
             roll_out = -_cyclic_max/4500.0f;
             limit.roll = true;
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Single.cpp b/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
index b5769bfa631899..4e9f027a01e461 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
+++ b/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
@@ -437,7 +437,7 @@ void AP_MotorsHeli_Single::move_actuators(float roll_out, float pitch_out, float
     float collective_scalar = ((float)(_collective_max-_collective_min))*0.001f;
     float collective_out_scaled = collective_out * collective_scalar + (_collective_min - 1000)*0.001f;
 
-    // Caculate servo positions from swashplate library
+    // Calculate servo positions from swashplate library
     _swashplate.calculate(roll_out, pitch_out, collective_out_scaled);
 
     // update the yaw rate using the tail rotor/servo