Hi All after many frustrating days trying to get a VNAV PATH descent to work I discover that there is a bug in the FMC of the 737 :-( Does anyone know if this has been fixed? I see that the workaround is to cycle the VNAV button - the magenta vertical path bug still remains in my case. Is this normal? thanks JL

Hello, Would like to help you but your post is not to clear for me, could you explain what exactly you are referring to? As to your last question - the path deviation diamond will remain whether one is in VNAV or not. Best,Randy J. Smith<<>>

I understand the problem.. the 737 FMC has a known bug where crossing an altitude constraint will sometimes cause the descent to "freeze" and a magenta bug to appear on the VSI. Cycling the VNAV off/on will clear it. This is a known bug and I expect the 737NGX will have completly new code to resolve this problem. Also, the 737 FMC will not handle dual constraints (at or above & at or below). These are a few reasons why I don't use VNAV for descent (only departures).