VNAV disconnect

[Guest stevesj]

Hi Can anyone tell me what the possible reasons are for a VNAV disconnect on the 737. I can find LNAV reasons in the manuals but not for VNAV. I am finding this problem if I disconect to go to V/S or LVL CHG and then wan to go back to VNAV after, if that helps ?MTIASteve

[pschlute 37]

When you try to return to VNAV are you adhering to any altitude restrictions set on the leg you are flying ?Peter

[Guest stevesj]

Hi PeterYes, as I had the same thought. Steve

[crvm 0]

If you overspeed or reach vmo/mmo it will revert to lvl ch. Under 10' I believe it is more restrictive soi watch your speed and use the speedbrakes when you get DRAG RQ................Randy J. Smith................A PROUD MEMBER OF THE PMDG BETA TEAM[h4]Evolution is a process that results in heritable changes in a population spread over many generations[/h4]

[Guest stevesj]

Thanks Randy, in this case I was far from VMO (220KIAS), this is perhaps a more complicated question than thought. When/if it happens again I will note the scenario better.CheersSteve