when i armed my plane , i pushed the throttle stick up and i wait 5 second then PX4 disarming itself 
is there any parameters to the solve this problem ?
or is there any settings on QGroundContol?
used Manual flight mode
note: i’m using PX4 v1.11.2 version and Qgroundversion is v4.2.4,transmiter is Radiolink AT10 (2)