diff --git a/ArduPlane/quadplane.cpp b/ArduPlane/quadplane.cpp
index dc121e07ae..febde6db11 100644
--- a/ArduPlane/quadplane.cpp
+++ b/ArduPlane/quadplane.cpp
@@ -963,6 +963,10 @@ void QuadPlane::motors_output(void)
     if (motors->armed()) {
         plane.DataFlash.Log_Write_Rate(plane.ahrs, *motors, *attitude_control, *pos_control);
         Log_Write_QControl_Tuning();
+        uint32_t now = AP_HAL::millis();
+        if (now - last_ctrl_log_ms > 100) {
+            attitude_control->control_monitor_log();
+        }
     }
 }
 
diff --git a/ArduPlane/quadplane.h b/ArduPlane/quadplane.h
index 37b33067d8..5afa3bcb42 100644
--- a/ArduPlane/quadplane.h
+++ b/ArduPlane/quadplane.h
@@ -299,6 +299,9 @@ private:
         uint8_t motor_count;          // number of motors to cycle
     } motor_test;
 
+    // time of last control log message
+    uint32_t last_ctrl_log_ms;
+    
     // tiltrotor control variables
     struct {
         AP_Int16 tilt_mask;
diff --git a/ArduPlane/tuning.cpp b/ArduPlane/tuning.cpp
index 80d8ea0f27..a53c845572 100644
--- a/ArduPlane/tuning.cpp
+++ b/ArduPlane/tuning.cpp
@@ -264,3 +264,33 @@ void AP_Tuning_Plane::reload_value(uint8_t parm)
         break;
     }
 }
+
+/*
+  return current controller error
+ */
+float AP_Tuning_Plane::controller_error(uint8_t parm)
+{
+    switch(parm) {
+    // special handling of dual-parameters
+    case TUNING_RATE_ROLL_PI:
+    case TUNING_RATE_ROLL_P:
+    case TUNING_RATE_ROLL_I:
+    case TUNING_RATE_ROLL_D:
+    case TUNING_RATE_PITCH_PI:
+    case TUNING_RATE_PITCH_P:
+    case TUNING_RATE_PITCH_I:
+    case TUNING_RATE_PITCH_D:
+    case TUNING_RATE_YAW_PI:
+    case TUNING_RATE_YAW_P:
+    case TUNING_RATE_YAW_I:
+    case TUNING_RATE_YAW_D:
+        if (!plane.quadplane.available()) {
+            return 0;
+        }
+        return plane.quadplane.attitude_control->control_monitor_rms_output();
+
+    default:
+        // no special handler
+        return 0;
+    }
+}
diff --git a/ArduPlane/tuning.h b/ArduPlane/tuning.h
index e1178550da..dd457d977a 100644
--- a/ArduPlane/tuning.h
+++ b/ArduPlane/tuning.h
@@ -83,10 +83,11 @@ private:
         TUNING_SET_AZ =                      7,
     };
 
-    AP_Float *get_param_pointer(uint8_t parm);
-    void save_value(uint8_t parm);
-    void reload_value(uint8_t parm);
-    void set_value(uint8_t parm, float value);
+    AP_Float *get_param_pointer(uint8_t parm) override;
+    void save_value(uint8_t parm) override;
+    void reload_value(uint8_t parm) override;
+    void set_value(uint8_t parm, float value) override;
+    float controller_error(uint8_t parm) override;
 
     // tuning set arrays
     static const uint8_t tuning_set_rate_roll_pitch[];