The doc of Level Horizon Calibration says:
4.Place the vehicle in its level flight orientation on a level surface:
For planes this is the position during level flight (planes tend to have their wings slightly pitched up!)
I am confusing about how to place the FW plane in its level flight orientation. Because when I place the plane on a level surface, wings slightly pitched up, and the FC is not in the level flight orientation.
Should I do the level calibration only with the FC alone ?
Yes, calibrate level at that position so the FC knows that attitude will make the plane fly level.
Thanks for your reply.
When i put the plane on a level surface, is this position the same as level fly position?
maybe it is not the position for level fly, because the wings pitched up.
Yes. I usually use an incidence tool and give it about 2 degrees pitch up then test it. Increase or decrease as you see fit when you test fly. Keep in mind, that will only work at cruise throttle setting to maintain level flight.