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G3X / GTN 650 problem

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dweyant

Well Known Member
I'm guessing this is operator error, but it is frustrating me...

The last couple times I have tried to fly an RNAV approach using my GTN650 with dual screen g3x Touch setup I have not been able to get any vertical guidance.

I.e. I am not getting the VS bar on the side of my altimeter ribbon.

I am loading and activating the approach, starting at an initial fix and flying the entire approach.

Any suggestions on what I might be doing incorrectly?

Thanks,

-Dan
 
It would help to know the approach and what the HSI annunciation (i.e. LPV, LNAV+V, LNAV, etc) was at the time.
 
Dan, absent the Garmin guys' response I'll conjecture that I don't think it's operator error, could be an integrity issue, although twice does sound kind of suspicious. Did you notice whether you were getting the "LPV" annunciation on the HSI? No LPV annunciation could indicate a possible navigation integrity issue. Also, there are a couple of other things you could check but I'm sure you probably already have. Check to make sure you are in the "external navigator" mode on the G3X. Also, go to the Default Nav page on the 650 and make sure you have the correct nav source selected down at the bottom. You want to make sure you're not in SUSP mode (like it's expecting you to execute a procedure turn or enter holding). When you select your approach on the 650, make sure you select a transition and follow it. If you select the IAF as the transition, it will probably ask if you want a procedure turn. If you don't respond "NO", it might assume you are maneuvering about the IAF and place you in SUSP mode. My worst fear would be that the WAAS portion of the receiver is compromised in some way. That's all I can think of at the moment. Let us know what you find!
 
First, when you power up the 650 and it goes through it's self test, take a look at the G3X screen and make sure it is showing a vertical guidance bar on the screen. Everyone is usually in a hurry and rushes right past those tests. If it's not there, it could be a config issue. Make sure Vertical labels are configured int he 650 setup.

Vic
 
vic syracuse said:
First, when you power up the 650 and it goes through it's self test, take a look at the G3X screen and make sure it is showing a vertical guidance bar on the screen. Everyone is usually in a hurry and rushes right past those tests. If it's not there, it could be a config issue. Make sure Vertical labels are configured int he 650 setup.

Vic
Click to expand...

Hmm,

I'll go check that, but it had been working and just recently stopped.

I'll go check the vertical labels as well. Thanks,

-Dan
 
Pat Hatch said:
Dan, absent the Garmin guys' response I'll conjecture that I don't think it's operator error, could be an integrity issue, although twice does sound kind of suspicious. Did you notice whether you were getting the "LPV" annunciation on the HSI? No LPV annunciation could indicate a possible navigation integrity issue. Also, there are a couple of other things you could check but I'm sure you probably already have. Check to make sure you are in the "external navigator" mode on the G3X. Also, go to the Default Nav page on the 650 and make sure you have the correct nav source selected down at the bottom. You want to make sure you're not in SUSP mode (like it's expecting you to execute a procedure turn or enter holding). When you select your approach on the 650, make sure you select a transition and follow it. If you select the IAF as the transition, it will probably ask if you want a procedure turn. If you don't respond "NO", it might assume you are maneuvering about the IAF and place you in SUSP mode. My worst fear would be that the WAAS portion of the receiver is compromised in some way. That's all I can think of at the moment. Let us know what you find!
Click to expand...

All I'm getting on the G3X (verified I'm in external mode) is the GPS and LNAV on the HSI.
 
Auburntsts said:
It would help to know the approach and what the HSI annunciation (i.e. LPV, LNAV+V, LNAV, etc) was at the time.
Click to expand...

I have tried a couple different approaches.

the RNAV into T74, and the RNAV36 into KGTU.

On both my G3X Touch is just showing GPS and LNAV with no vertical guidance showing up.

-Dan
 
If the GTN says "LNAV" then there will be no glide slope. The question is, why no LPV? Could be poor satellite geometry, or your box's WAAS circuit is not working. Next time ask ATC if anyone else is having trouble with WAAS or LPV authorization. If the answer is no then it's your box or antenna. Go to the display page showing sattelite reception, do you see any with WAAS corrections?
 
Based upon the fact that you were reviving WAAS vertical guidance in the past and are now only receiving lateral guidance seems to indicate you've got an issue with the 650. Unfortunately it probably means you'll need to get an avionics shop involved to resolve this issue.
 
BobTurner said:
If the GTN says "LNAV" then there will be no glide slope. The question is, why no LPV? Could be poor satellite geometry, or your box's WAAS circuit is not working. Next time ask ATC if anyone else is having trouble with WAAS or LPV authorization. If the answer is no then it's your box or antenna. Go to the display page showing sattelite reception, do you see any with WAAS corrections?
Click to expand...

Got it!

Thanks everyone. Bob gave me the clue. We have been going over the settings on everything on my RV-9 helping my buddy get his stuff configured, and I think somehow we inadvertently turned off the WAAS setting. Bob's comment got me to go and check everything. Just did a quick flight and everything worked fine.

-Dan
 
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