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  #21  
Old 09-15-2018, 10:56 AM
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Walt Walt is offline
 
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Originally Posted by Brantel View Post
I think what he described he did was what this note posted earlier addresses:

ďNOTE: If APPR mode is armed prior to capturing the final VNAV descent leg, the autopilot will not capture the final VNAV descent leg.Ē

I may be wrong but that is how I read it.
So just for ref how do you know when the final VNAV leg is captured?
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  #22  
Old 09-15-2018, 11:11 AM
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Quote:
Originally Posted by Walt View Post
So just for ref how do you know when the final VNAV leg is captured?
Not sure, I think when the VNAV indicator turns green. I have not flown it yet. Was going to today but the wind is howling here as the edge of the hurricane has arrived here.
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  #23  
Old 09-15-2018, 05:36 PM
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ColoRv ColoRv is offline
 
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Quote:
Originally Posted by Brantel View Post
I think what he described he did was what this note posted earlier addresses:

ďNOTE: If APPR mode is armed prior to capturing the final VNAV descent leg, the autopilot will not capture the final VNAV descent leg.Ē

I may be wrong but that is how I read it.
I believe that is what is happening as well. Levi said earlier that you can activate approach mode once the diamond starts down but I tried that twice and it failed each time. The issue is the final VNAV is only 200í and the GTN waits till the last minute to make that descent so the diamond is well down the deviation indicator before that VNAV captures. Iíll wait for it on the next flight and see if that does it, but having to time that APPR push that tight seems like something Garmin may want to address. Make the descents less aggressive and therefore further out and let VNAV hand off to APPR automatically.

Or maybe Iím just hamfisting the whole thing. :-) Iím sure we will all figure this out, and I will get them the log they requested next time Iím out there. Mostly Iím trying to figure out what the system wants me to do, so that I can do it....then see if it responds as expected. At present, Iím still a bit confused on when the APPR mode should be activated.
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  #24  
Old 09-26-2018, 07:21 AM
supik supik is offline
 
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Quote:
Originally Posted by g3xpert View Post
You are flying to Leadville....

As the VNAV deviation indication centers, the autopilot captures the vertical profile and centers the VNAV deviation through the decent. The ALTV autopilot mode is automatically armed. When the VNAV constraint altitude is reached, the aircraft levels out and maintains altitude until the next VNAV descent leg.




.....

Thanks,
Levi
I see that the autopilot will start descent even though the altitude preselect wasn't changed for lower altitude (still at 16000). Would this be an open descent with no altitude restriction?

If the preselected altitude would be 14000ft -will the aircraft level of at 14000ft or will it just follow the vertical path and ignore the preselect if VNAV is active?
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  #25  
Old 09-26-2018, 07:39 AM
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Default still not sure how this works

I've flown 3 approaches in the last week and non of them were successful using VNAV to automatically capture and descend down to IAF altitude. Am I correct to assume to this feature is to be used or can be used well before reaching the approach phase of flight? Example, 50 miles out on an airway with certain altitude restrictions, once the white diamond shows up, I can start using VNAV, correct?
I'm feeling a little dumb trying to get this to work but I see I'm not the only one having issues. Maybe Garmin can hold a short training class or do a 15 minute video.

Thanks
AB
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  #26  
Old 09-26-2018, 09:52 AM
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Quote:
Originally Posted by supik View Post
I see that the autopilot will start descent even though the altitude preselect wasn't changed for lower altitude (still at 16000). Would this be an open descent with no altitude restriction?

If the preselected altitude would be 14000ft -will the aircraft level of at 14000ft or will it just follow the vertical path and ignore the preselect if VNAV is active?
When VNAV mode is selected, the FD/AP follows the VNAV descent profile indicated by the magenta arrow on the vertical deviation indicator on the PFD. The target VNAV altitude is the indicated in magenta above the altimeter and the preselected altitude indicator.

The preselected altitude has nothing to do with VNAV mode.

EDIT: But it does determine which mode is armed for altitude capture during the descent. Either ALTV (VNAV target altitude) or ALTS (Preselected Altitude). Whichever one would be intercepted first on the descent is which one gets armed when VNAV mode is selected.
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Last edited by Brantel : 09-27-2018 at 10:26 AM.
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  #27  
Old 09-26-2018, 10:10 AM
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Originally Posted by BCP Boys View Post
I've flown 3 approaches in the last week and non of them were successful using VNAV to automatically capture and descend down to IAF altitude. Am I correct to assume to this feature is to be used or can be used well before reaching the approach phase of flight? Example, 50 miles out on an airway with certain altitude restrictions, once the white diamond shows up, I can start using VNAV, correct?
I'm feeling a little dumb trying to get this to work but I see I'm not the only one having issues. Maybe Garmin can hold a short training class or do a 15 minute video.

Thanks
AB
Did your GTN's flight plan have altitude values listed beside the flight plan waypoints prior to the IAF? As far as I can tell, only the approach waypoint altitudes are pre-populated when an approach is loaded and activated. If there are no altitudes tied to the waypoints prior to the IAF, the GTN has no idea how to calculate the VNAV profiles. It is my understanding that the pilot can add and manipulate waypoint altitudes manually if they wish.

Assuming an approach has been loaded and is active...When approaching the TOD point just prior to the IAF, you must have VNAV armed or it will not capture it when the magenta arrow starts down the VDI. The magenta arrow is the VNAV indicator. The white (Garmin calls it Grey) diamond is the GP indicator before GP capture. If you fly thru the VNAV calculated profile, it is too late and you have lost the opportunity to use VNAV to get down.

To capture the GP, you must arm APR mode before you fly thru the GP. Once captured, the Grey diamond will turn Magenta and the AP mode annunciator will switch the GP mode from armed (Grey) to active (Green).

If you wait till the the Grey GP indicator is coming down, you have lost the opportunity to use VNAV and should just go straight to arming APR mode. If you fly thru the GP, it is too late to capture it...

I have flown several practice approaches with these new features and so far they seem to work as described by Levi. I have not tried using VNAV prior to the IAF long before the approach starts.
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Last edited by Brantel : 09-26-2018 at 10:26 AM.
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  #28  
Old 09-26-2018, 10:22 AM
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Quote:
Originally Posted by ColoRv View Post
SNIP>>>>Make the descents less aggressive and therefore further out <<<<SNIP
You can adjust the angle that the GTN uses to calculate the decent profile. I think the default is 3° which in this case seems to be about the same as the GP on the approach you were shooting which is likely why you had issues with it. You could adjust this variable to better suit the way you normally fly descents by hand.

There is a supplement to the manual for the GTN ver 6.50 here:

http://static.garmin.com/pumac/190-01004-19_A.pdf
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---------------------------------------------------------------------
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Last edited by Brantel : 09-26-2018 at 10:37 AM.
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  #29  
Old 09-27-2018, 02:23 AM
supik supik is offline
 
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Quote:
Originally Posted by Brantel View Post
When VNAV mode is selected, the FD/AP follows the VNAV descent profile indicated by the magenta arrow ....

The preselected altitude has nothing to do with VNAV mode.
If the preselect altitude has no influence on the ap/fd when flying in VNAV -no altitude capture would happen if a lower altitude is preselected (lets say 15000ft in this case)

-is this correct?

-what do you do if ATC tells you to stop descent and level off at 15000? Would you have to change to another vertical mode?
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  #30  
Old 09-27-2018, 07:35 AM
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Quote:
Originally Posted by supik View Post
If the preselect altitude has no influence on the ap/fd when flying in VNAV -no altitude capture would happen if a lower altitude is preselected (lets say 15000ft in this case)

-is this correct?

-what do you do if ATC tells you to stop descent and level off at 15000? Would you have to change to another vertical mode?
If you are in VNAV mode and ALTV is armed you will level off at 1400 in this case above.

EDIT: Levi added some clarification below see his post for how it really works.

Bottom line, if "ALTV" is armed, it will level off at the "VNAV Target Altitude". If "ALTS" is armed, it will level off at the "Preselected Altitude". In VNAV mode if the pilot moves the "Preselected Altitude" to a value between the current altitude and the "VNAV Target Altitude", the system will automatically switch the armed mode from "ALTV" to "ALTS" and level off at the "Preselected Altitude".
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---------------------------------------------------------------------
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Last edited by Brantel : 09-27-2018 at 02:12 PM.
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