Question about MAV_CMD_NAV_TAKEOFF point

Hello, we want to try to use automatic takeoff/landing of a plane, so the question is what should plane do in this point, try to lift off the ground on this point, try to reach selected altitude in this point (if plane cant reach it, should he go to next point) or what?

I read http://ardupilot.org/plane/docs/common-mavlink-mission-command-messages-mav_cmd.html#mav-cmd-nav-takeoff but still can not understand it.

Thanks in advance, Nikita.

The takeoff command has no coordinates.
It just tells the FC to initiate the automatic disarming sequence to start the engine at the given acceleration (TKOFF_THR_MINACC) and speed (TKOFF_THR_MINSPD) and climb with the given pitch angle until it reaches the given height. After the height is reached plane will proceed to the next waypoint