Common VNAV Option B737

[mangatete]

Can anyone explain what the difference and benefits, if any, of having the common VNAV option selected when operating with 10.7 on a B737 400.

Cheers Mangatete

[FCS Explorer]

and... Can anyone explain what the "common VNAV option" is?
[yes, i know what VNAV is - but "common"...?!]

[mangatete]

I cannot find to much about it in the Boeing Vol 2, but have operated both with and without the common VNAV option selected. With the COMMON VNAV OPTION incorporated the pilot cannot select a speed descent, however the FMC will automatically change to a speed descent when descending in a path descent and the aircraft is above the path. It will automatically revert back to a path descent when on or below the descent path.