Removing rc in guided mode

I tried changing mode to circle mode using dronekit in guided with mavlink command. I had to use rc override to keep constant altitude in circle mode. Everything works fine except that when i do the same process without rc drone crashes. What is going wrong.

You will need to disable the throttle failsafe. google for arducopter throttle failsafe
There is no need to use RC override to keep the altitude constant. just guide the vehicle to the desired altitude before starting the LOITER_TURNS command.

Actually i am invoking ardupilot inbuilt circle mode and so used rc override otherwise the drone would come down.