Sometimes vnav refuses to be activated.

[Guest Langrath]

In PMDG Boeing all versions.In some of my flightplans I can

[Guest PullUp]

Hi,Normally you will not be able to engage VNAV if for some reason it is not able to reach the altitude stipulated for the next waypoint. There can be a number of reasons for this:1. The MCP altitude is not set correctly.2. The next waypoint is close to the aircrafts current position and has an altitude restriction that the aircraft cannot reach.3. I have seen it occasionaly when the aircrafts current altitude is above the altitude for the current leg.etcThe FMSC should give you some error message which should help determine what the cause is.Check the legs page of the FMS and see that altitude constraints (either manual or calculated) are present for each entered waypoint - if not, probably some FMS setup information has been missed.Hope this helps.Peter

[Guest Langrath]

>Hi,>>Normally you will not be able to engage VNAV if for some>reason it is not able to reach the altitude stipulated for the>next waypoint. There can be a number of reasons for this:>>1. The MCP altitude is not set correctly.>2. The next waypoint is close to the aircrafts current>position and has an altitude restriction that the aircraft>cannot reach.>3. I have seen it occasionaly when the aircrafts current>altitude is above the altitude for the current leg.>>etc>>The FMSC should give you some error message which should help>determine what the cause is.>>Check the legs page of the FMS and see that altitude>constraints (either manual or calculated) are present for each>entered waypoint - if not, probably some FMS setup information>has been missed.>>Hope this helps.>>Peter*