TradHeli: Modify Throttle_Auto to prevent helis from pushing hard downward while running up the motor. We will set the collective pitch to stab_col_min which should result in a mild downward pressure if the user has set their parameters correctly.

ArduCopter/ArduCopter.pde

@@ -1995,8 +1995,13 @@ void update_throttle_mode(void)
             get_throttle_althold_with_slew(wp_nav.get_desired_alt(), -wp_nav.get_descent_velocity(), wp_nav.get_climb_velocity());
             set_target_alt_for_reporting(wp_nav.get_desired_alt()); // To-Do: return get_destination_alt if we are flying to a waypoint
         }else{
+#if FRAME_CONFIG == HELI_FRAME
+            // collective pitch should not be full negative to avoid harshing the mechanics. Use Stab Coll Min.
+            set_throttle_out(motors.stab_col_min*10, false);
+#else
             // pilot's throttle must be at zero so keep motors off
             set_throttle_out(0, false);
+#endif // HELI_FRAME
             // deactivate accel based throttle controller
             throttle_accel_deactivate();
             set_target_alt_for_reporting(0);