Plane: Added parameter TKOFF_THR_IDLE

ArduPlane/Parameters.cpp

@@ -158,6 +158,15 @@ const AP_Param::Info Plane::var_info[] = {
     // @User: Standard
     ASCALAR(takeoff_throttle_min,       "TKOFF_THR_MIN",    0),
 
+    // @Param: TKOFF_THR_IDLE
+    // @DisplayName: Takeoff idle throttle
+    // @Description: The idle throttle to hold after arming and before a takeoff. Applicable in TAKEOFF and AUTO modes.
+    // @Units: %
+    // @Range: 0 100
+    // @Increment: 1
+    // @User: Standard
+    ASCALAR(takeoff_throttle_idle,       "TKOFF_THR_IDLE",    0),
+
     // @Param: TKOFF_OPTIONS
     // @DisplayName: Takeoff options
     // @Description: This selects the mode of the takeoff in AUTO and TAKEOFF flight modes. 

ArduPlane/Parameters.h

@@ -359,6 +359,7 @@ public:
         k_param_autotune_options,
         k_param_takeoff_throttle_min,
         k_param_takeoff_options,
+        k_param_takeoff_throttle_idle,
 
         k_param_pullup = 270,
     };

ArduPlane/servos.cpp

@@ -619,6 +619,11 @@ void Plane::set_throttle(void)
             // throttle is suppressed (above) to zero in final flare in auto mode, but we allow instead thr_min if user prefers, eg turbines:
             SRV_Channels::set_output_scaled(SRV_Channel::k_throttle, aparm.throttle_min.get());
 
+        } else if ((flight_stage == AP_FixedWing::FlightStage::TAKEOFF)
+                    && (aparm.takeoff_throttle_idle.get() > 0)
+                  ) {
+            // we want to spin at idle throttle before the takeoff conditions are met
+            SRV_Channels::set_output_scaled(SRV_Channel::k_throttle, aparm.takeoff_throttle_idle.get());
         } else {
             // default
             SRV_Channels::set_output_scaled(SRV_Channel::k_throttle, 0.0);