Not sure it is the right place to ask but…
Mission Planner"
From the laptop the [Ctrl] [F] sub command:
quad: Arm and takeoff
Actually does arm the aircraft Pixhawk (Even if the transmitter is switched off).
Before connecting a battery and testing this magical command, I would like to see a bit of documentation. 
- What altitude and which mode would the aircraft be after executing this “sub” command?
If you have been using this command from mission planner please share your experience…
Thank you in advance.
Henri