Please be kind to me guys, I know I should know the answer to this, but the NGX is still a new experience for me. I am very puzzled regarding the top speed of the NGX, which I understand is about 520kts, far in excess of what my NGX ever reaches. AP running with VNAV, LNAV and AT set. all the relevent info inputted into the FMC (I suspect this is my trouble) The plane never exceeds 320kts under the AT control. however, if I try to fly the plane manually with manual throttle, the plane cries out warnings if I try to fly beyond 320kts ??? I am very confused and would really appreciate someone to clarify this for me. Thanks fellas...

did you actually passed the overspeed? which flight level? were you heavy?

Look at your Mach number or groundspeed on the ND. At cruise, indicated airvspeed is unreliable.

Howard,First, where did you find that nugget of information? I'm curious as to what the listed airspeed was. Additionally, keep in mind that there are different airspeeds: Indicated, Calibrated and True.http://en.wikipedia.org/wiki/Indicated_airspeedhttp://en.wikipedia.org/wiki/Calibrated_airspeedhttp://en.wikipedia.org/wiki/True_airspeedI believe what you're seeing on the NGX's displays is CAS (calibrated), whereas I'm guessing that figure listed is TAS, and slightly exaggerated at that.

Hi HowardI think that Kyle is right as the speed tape shows Calibrated Air Speed (CAS). The other figure would be TAS and in fact with a tailwind you can get a ground speed ofover 600 knots.Out of interest Concorde's max CAS was of the order of 520 knots, yet it's supersonic ground cruising speed was over 1,100 knots.Lift is dependant on the mass of air flowing over the wings and CAS is the best measure of this and is therefore useful for flap deployment etc.

Cheers guys. At least I know it's not me (for a change!) Thanks for clearing it up...