I can’t find much difference between these two modes, anyone has any idea about them?
Loiter is an ‘autonomous’ mode where the aircraft just circles around a given point. Fbwb is an ‘assisted’ mode, where the pilot manually sets speed, direction and altitude but the autopilot takes care of the rest.
So in FBWB, speed, direction and altitude are inputed as parameter before flight?
BTW, what does direction means?
No, fbwb requires the pilot to steer the aircraft with the rc transmitter. Please read the guide here: http://ardupilot.org/plane/docs/flight-modes.html