Gtn-650 - vnav unavailable upcoming flight plan leg unavailable

[Latech15]

I first started seeing this message a few flights ago. Been working perfectly for years. It typically comes up once I start getting vectored. It has always gone away and worked correctly before the faf when I need to start down, but it’s unnerving to see it in actual IMC.

Any ideas on why I’m getting this message all of a sudden?

 

[Latech15]

Just got off with garmin. It appears an expired database is the reason.

Just wanted to report here in case any other bone heads have the same issue.

 

[g3xpert]

VNAV Unavailable

Good Afternoon,

Was the message you were seeing "VNAV - Unavailable. Upcoming flight plan leg not supported"?

This can be displayed when the next leg in the lateral flight plan contains a procedure turn or vector prior to the active vertical waypoint, which prevents vertical descent path guidance.

Thanks,

Justin

 

[Latech15]

Yes. That is the message. I need to go do some testing apparently. Did something change? I’ve never seen that message until recently.

 

[uk_figs]

Just got off with garmin. It appears an expired database is the reason.

Just wanted to report here in case any other bone heads have the same issue.

For interest, can you expand on which database expiry caused the problem? I assume the 375 would not have the same issue as it does not have en route VNAV.

 

[mburch]

Sometimes phone support people have an off day. I highly doubt an expired navigation database would cause problems with VNAV.

If I had to guess, I would say that it's much more likely that while being vectored you put the aircraft into some combination of position and altitude that made it unable to continue providing vertical guidance, so it gave up.

 

[oaklandaviator]

Did you update the software?

I have a legacy G3X and a 650. Recently when I updated the software in both of them the settings for barometric vnav somehow changed. Because of this, the enroute vnav would look to the G3X instead of the 650 and the 650 would do the approach vnav. When using enroute vnav coupled to the G3X I would get this same message if I had an approach loaded in the 650 and it was the next leg. I took my plane to the avionics shop for a bunch of “help” and this was one of my complaints. The very astute tech found the inappropriate settings and changed a few things. Now the enroute vnav works on the 650 again and the option to use vnav on the G3X is no longer there if I am using the external flight plan (650).

I’d check your barometric vnav settings in the 650 or at least peruse through the settings. I’d bet you updated the software and it changed something.

 

[Walt]

Sometimes phone support people have an off day. I highly doubt an expired navigation database would cause problems with VNAV.

If I had to guess, I would say that it's much more likely that while being vectored you put the aircraft into some combination of position and altitude that made it unable to continue providing vertical guidance, so it gave up.

And don't forget VNAV only works in NAV mode, if you're getting vectored and switched to heading mode VNAV won't work any longer.

 

[g3xpert]

GTN VNAV Unavailable

Yes. That is the message. I need to go do some testing apparently. Did something change? I’ve never seen that message until recently.

Can you share the procedure you are flying, and a little bit more about when/ where you are in the procedure when you see the message?

Thanks,

Justin

 

[iamtheari]

And don't forget VNAV only works in NAV mode, if you're getting vectored and switched to heading mode VNAV won't work any longer.

Does the GTN have any awareness of the autopilot being switched from NAV to HDG, though? The message discussed here is a GTN message about VNAV not being available for an upcoming flight plan leg.

I get this message routinely on my GTN. I think that it's consistently when I have loaded a visual approach into the GTN, but I'm not sure about that. I'm watching this thread and will try to pay attention to when this comes up when I'm flying in case I notice anything helpful.

 

[Latech15]

The most recent one was the rnav 27 at KESF. I was enroute from KMLU. Still 25 mikes or so north of the field. Was given direct ILULE for the procedure turn, that’s when I got the message.

Also saw it on the rnav 35 @ Kara. Got the message while being vectored southbound, east of WOKDO. In both cases, the message went away as I got close to intercepting the final approach path.