Is there a reason sometimes why the PMDG 747 does not always follow the speed restrictions when I set them. It will descend correctly but it will not slow to the speed that I have entered. Any ideas on this issue. ThanksJackie Padilla

Sometimes speed restrictions can't be met if aircraft is too heavy or programmed trajectory is too steep.

thanks Michal for the infoJackie Padilla

There is much on the 747 VNAV descent performance in previous threads. There are those that prefer to use it all the way to the IAP but I prefer to use the MCP SPD and V/S to control the descent with VNAV providing secondary guidance and that seems to be more realistic in most cases.