First of all, I have to say that the PMDG 737 is by far the most accurate add-on there has ever been! As a trainee 737-400 first officer I found it extremely useful and practiced a LOT with it. However, the new version has a problem: When descending with VNAV engaged, it will not maintain the preselected speed (while being very accurate at the descent path profile), and it will fly 15-35 kts below the desired speed. Anyone knows why or how to fix that??!?

Please sign your name to your post.This is because of the descent mode you are in.VNAV PTH = no speed control, and the plane descends via the FMC ALT constraints. This is the active mode when a alt constraint is present in the descent path.VNAV SPD = This is the active descent mode when the plane has no descent constraints to follow. The plane maintains the speed that is selected.