VNAV disconnects from overspeeds into the clackers are not unusual with cost indices over 50.
Usually only when still on Mach and if not correctly or adequately taking into account actual winds at T/D or early descent, from what I've experienced.
Usually to do with the fact that the aircraft only allows for a small margin in Mach technique and when KIAS is increasing speed (as VNAV is trying to retaining a fixed Mach until a precomputed KIAS is achieved) VNAV does not always allow much room for error. This can be mitigated by slowing the Mach in descent a bit to artificially enhance a slightly greater margin, but of course you know that already.
If you have 10k on type, you must surely be familiar with that?
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.
No need for such language
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.
It seems not so when we fly CDA's from T/D to IAF without that problem daily on multiple sectors, so I'm sorry but I can't share your experience in this I'm afraid, but am willing to learn what not to do to get me in such a state of flight...
VNAV behaves by the book, BUT VNAV is only able to calculate as good as the data that goes into the FMC, so when we ensure the inputs are good we thus avoid outputs to be bad.
What the manual says is dandy, but if you are a trainer, you should be teaching what actually happens - we fly aeroplanes, not manuals.
I totally agree, but sometimes the information contained in the manuals is more then the information the trainer thinks he knows.
atpcliff: Does the 747-400 VNAV work the same as the 737?
Similar but not the same, manuals equivalent to the one quoted should be available though your appointed Boeing contact liaison in your company.
And please, no, I do nor did try offend any person in this thread.