737-800 VNAV BUG

[Guest johnlattanzio]

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

[crvm 0]

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<<>>

[downscc 1,327]

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).