Idle throttle setting problem when disarmed

I installed APM pro on a calmato alpha 40 with gas engine DLE 10, I calibrated the radio. So when the plane is armed the throttle works well, but when the plane is disarmed, the throttle servo is in the max position instead of min position, and I am obliged to arm to set the throttle in the idle (min) position then start the engine.
How can I set the throttle to idle position when the plane is disarmed,
I tried reverse in mission planner but it doesn’t work.