What am I doing wrong with VNAV?

[paul.ziegler96]

Hi, I have the following issue with VNAV:
I would assume the FMS calculates VNAV Data after I set up the PERF Page. Somehow this does not work out for me.
The pictures below show what I have setup:

vnav1.JPG (58.63 KiB) Viewed 1093 times

vnav2.JPG (55.77 KiB) Viewed 1093 times

vnav3.JPG (56.03 KiB) Viewed 1093 times

vnav4.JPG (54.38 KiB) Viewed 1093 times

vnav5.JPG (52.48 KiB) Viewed 1093 times

Is there someone who can give me a quick explanation on how this should work?

[KenG]

In the LEGS there needs to be an altitude constraint.

Such as type in /F200 then put it into ABGAS [LSK 4L]

Now you can VNAV climb to ABGAS, although to be blunt, VNAV climbs is really not worth the effort unless you have a complicated SID with multiple altitudes you have to meet.

VNAV works best when ATC tells you to climb via or descend via...

If you just want to play with it some, put in some altitude constraints, try to make them realistic or the FMS will throw error messages.

[paul.ziegler96]

Thanks for the reply, if I get you correctly VNAV only calculates a path for specific problems like ALT constraints at a waypoint, there will be no automatic calculation based on the cruise altitude from the PERF page.

[SAS443]

Thanks for the reply, if I get you correctly VNAV only calculates a path for specific problems like ALT constraints at a waypoint, there will be no automatic calculation based on the cruise altitude from the PERF page.

Correct, just like the Univesal box you will find in the Q400, for example.

But back to our King Air, here are the short intro to the VNAV function
The FMS3000 VNAV feature is to comply with crossing restrictions issued by ATC or a database procedure (STAR, ILS, VOR, RNAV appr, you name it)

VNAV Altitude will be automatically set on the LEGS page if it is part of a database derived procedure. The pilot can also insert an altitude associated with any waypoint. Once this is done, the FMS will generate the associated glidepath.
Autopilot will be able to track the vertical glidepath if these conditions are met:

1]Altitude must be entered into LEGS page (again either manually or part of database proc.)
2)The VNAV mode of the FGS must be selected
3)Preselected altitude must be set at, or beyond, the VNAV altitude

Do not treat this FMS as something you would find on a modern airliner.

[paul.ziegler96]

Thanks for the clarification!