diff --git a/libraries/AP_Motors/AP_MotorsHeli.h b/libraries/AP_Motors/AP_MotorsHeli.h
index ef8ca00022..061c1be995 100644
--- a/libraries/AP_Motors/AP_MotorsHeli.h
+++ b/libraries/AP_Motors/AP_MotorsHeli.h
@@ -102,9 +102,6 @@ public:
     // return true if the main rotor is up to speed
     bool rotor_runup_complete() const { return _heliflags.rotor_runup_complete; }
 
-    // rotor_speed_above_critical - return true if rotor speed is above that critical for flight
-    virtual bool rotor_speed_above_critical() const = 0;
-
     //get rotor governor output
     virtual float get_governor_output() const = 0;
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Dual.h b/libraries/AP_Motors/AP_MotorsHeli_Dual.h
index 2987d2fcd8..b7c0e5d511 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Dual.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_Dual.h
@@ -61,9 +61,6 @@ public:
     // get_desired_rotor_speed - gets target rotor speed as a number from 0 ~ 1000
     float get_desired_rotor_speed() const  override { return _main_rotor.get_rotor_speed(); }
 
-    // rotor_speed_above_critical - return true if rotor speed is above that critical for flight
-    bool rotor_speed_above_critical() const  override { return _main_rotor.get_rotor_speed() > _main_rotor.get_critical_speed(); }
-
     // get_governor_output
     float get_governor_output() const override { return _main_rotor.get_governor_output(); }
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Quad.h b/libraries/AP_Motors/AP_MotorsHeli_Quad.h
index 19dc56f638..599ad9a99a 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Quad.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_Quad.h
@@ -40,9 +40,6 @@ public:
     // get_desired_rotor_speed - gets target rotor speed as a number from 0 ~ 1000
     float get_desired_rotor_speed() const  override { return _main_rotor.get_rotor_speed(); }
 
-    // rotor_speed_above_critical - return true if rotor speed is above that critical for flight
-    bool rotor_speed_above_critical() const  override { return _main_rotor.get_rotor_speed() > _main_rotor.get_critical_speed(); }
-
     // get_governor_output
     float get_governor_output() const override { return _main_rotor.get_governor_output(); }
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_RSC.cpp b/libraries/AP_Motors/AP_MotorsHeli_RSC.cpp
index 5af82956f0..f43ba07766 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_RSC.cpp
+++ b/libraries/AP_Motors/AP_MotorsHeli_RSC.cpp
@@ -461,7 +461,7 @@ void AP_MotorsHeli_RSC::update_rotor_runup(float dt)
     }
     // if in autorotation, don't let rotor_runup_output go less than critical speed to keep
     // runup complete flag from being set to false
-    if (_autorotating && _rotor_runup_output < get_critical_speed()) {
+    if (_autorotating && !rotor_speed_above_critical()) {
         _rotor_runup_output = get_critical_speed();
     }
 
@@ -479,7 +479,7 @@ void AP_MotorsHeli_RSC::update_rotor_runup(float dt)
     }
     // if rotor speed is less than critical speed, then run-up is not complete
     // this will prevent the case where the target rotor speed is less than critical speed
-    if (_runup_complete && (get_rotor_speed() < get_critical_speed())) {
+    if (_runup_complete && !rotor_speed_above_critical()) {
         _runup_complete = false;
     }
     // if rotor estimated speed is zero, then spooldown has been completed
diff --git a/libraries/AP_Motors/AP_MotorsHeli_RSC.h b/libraries/AP_Motors/AP_MotorsHeli_RSC.h
index 6f606ca012..5d06b37b43 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_RSC.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_RSC.h
@@ -128,6 +128,9 @@ public:
     // Return mask of output channels which the RSC is outputting on
     uint32_t    get_output_mask() const;
 
+    // rotor_speed_above_critical - return true if rotor speed is above that critical for flight
+    bool        rotor_speed_above_critical(void) const { return get_rotor_speed() > get_critical_speed(); }
+
     // var_info for holding Parameter information
     static const struct AP_Param::GroupInfo var_info[];
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Single.h b/libraries/AP_Motors/AP_MotorsHeli_Single.h
index 66bfd8f6dc..3838a0770a 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Single.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_Single.h
@@ -61,9 +61,6 @@ public:
     // get_desired_rotor_speed - gets target rotor speed as a number from 0 ~ 1
     float get_desired_rotor_speed() const  override { return _main_rotor.get_desired_speed(); }
 
-    // rotor_speed_above_critical - return true if rotor speed is above that critical for flight
-    bool rotor_speed_above_critical() const  override { return _main_rotor.get_rotor_speed() > _main_rotor.get_critical_speed(); }
-
     // get_governor_output
     float get_governor_output() const override { return _main_rotor.get_governor_output(); }