Thank you 737jock. Your hours are nearly the same as mine, so I would have thought by now that you'd have learnt that what the manual says is not always what the aeroplane does. VNAV disconnects from overspeeds into the clackers are not unusual with cost indices over 50. If you have 10k on type, you must surely be familiar with that? And you must also be familiar with how VNAV will get you to the start of the approach about 30kts too fast if you programme the FMC with all the available data and have a planned continuous descent from the cruise. What the manual says is dandy, but if you are a trainer, you should be teaching what actually happens - we fly aeroplanes, not manuals.