Q1:is it possible in the NGX to use RTA or required time of arrival?essentially what this mean is it allows the VNAV system to target arrival at a particular waypoint at a defined time. This is often useful for airport arrival slot scheduling. In this case, VNAV regulates the cruise speed or cost index to ensure the RTA is met.Q2:From the TOD, the VNAV determines a four dimensional predicted path. As the VNAV commands the throttles to idle, the aircraft begins its descent along the VNAV path. If either the predicted path is incorrect or the downpath winds different than the predictions, then the aircraft will not perfectly follow the path.During descend The aircraft varies the pitch in order to maintain the path (VNAV). Since the throttles are at idle (usually) this will modulate the speed. Normally the FMS (in real life) allows the speed to within a small band. After this, either the throttles advance (if the aircraft is below path) or the FMS requests speed brakes with a message such as “ADD DRAG” (if the aircraft is above path).is the "ADD DRAG" message simulated in NGX FMS/CDU?

I was surprised that RTA was not included in SP1. Yes, the FMC will prompt "DRAG REQUIRED".

Rta is being considered for sp2. I say considered because I don't remember if it's definite or not.