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Yellow VLOC

Printed From: Avidyne
Category: Avidyne General
Forum Name: IFD 5 Series & IFD 4 Series Touch Screen GPS/NAV/COM
Forum Description: Topics on Avidyne's IFD 5 Series and IFD 4 Series Touch Screen GPS/NAV/COM
Printed Date: 25 Feb 2020 at 5:09pm
Software Version: Web Wiz Forums 12.01 -

Topic: Yellow VLOC
Posted By: vcollazo
Subject: Yellow VLOC
Date Posted: 24 Oct 2019 at 2:02pm
Was doing an ILS approach to a runway with GP OTS notam. When I manually switched from GPS to VLOC it came up yellow. Could find no reference in the manual. Can I assume that even though ID and all other parameters were OK, this was caused by the lack of the glideslope signa?


Posted By: dmtidler
Date Posted: 24 Oct 2019 at 3:45pm
FYI - from page 6-6 of the IFD540 Pilot's Guide (Rev 07):

VLOC is the active state (green), and all external deviation data being transmitted by the IFD is in reference to the active VHF-based leg (e.g. Inbound VOR course, localizer deviation, etc). Note that if no VHF data is being received (e.g. out of range, improperly tuned nav radio, etc), the nav mode will be displayed in yellow. It will also stay yellow until the nav channel is fully decoded as an indication to manually tune-identify-monitor.

Posted By: RedBirdPilot
Date Posted: 12 Jan 2020 at 1:43pm
Hi, I have a ILS glideslope question to piggy-back here...I've had my IFD550 for several months now and having trouble getting the glideslope indicator to activate during approches.  The glideslope needle remains hidden from view on the Gl106B...the localizer needle works fine.   I think the VLOC always stays yellow on the IFD550 when manually switching from GPS to VLOC, but the localizer freq. is green. 
The GL106B and SIN vision glideslope works fine on GPS approches
Also, the glideslope works just fine on the #2 KX155 with it's own indicator.

dmtidler, are you saying in the previous post that one needs to manually tune-identify-monitor to get the VLOC to turn green before the indicator needle will come on-line?
Did my installer forget to set something up correctly?


Posted By: mfb
Date Posted: 12 Jan 2020 at 2:36pm
Originally posted by RedBirdPilot RedBirdPilot wrote:

Are you saying in the previous post that one needs to manually tune-identify-monitor to get the VLOC to turn green before the indicator needle will come on-line?

No, the IFD itself listens to the identifier Morse code and deciphers it. When it decides that the code is correct, the VLOC indicator turns green. 

You can always punch up the the audio yourself to identify the station. But I don't know of any way that you can tell the IFD that you have manually identified it. VLOC will stay yellow until the IFD figures it out for itself.


Posted By: dmtidler
Date Posted: 12 Jan 2020 at 3:23pm
If Auto-VLOC Tuning is set to On and GPS to VLOC Capture is set to Auto in the user settings, there generally shouldn’t be a need to manually tune-identify-monitor. You should be able to tell if the VHF NAV station is tuned and identified by the presence of the decoded navaid identifier immediately below the green active nav frequency on your IFD. This active nav frequency decoding occurs based on reception of the active nav frequency tuned no matter the active nav mode (i.e. GPS, VLOC, LNAV, LPV) and may take a few moments after switching to a new active nav frequency that is in range and operating properly.

I’m curious if you are getting the decoded navaid identifier or not in your IFD’s active nav frequency box for both in range VOR’s and localizers? If either are not decoding, but seem to be properly displaying in VLOC, can you manually identify them by the listening to the broadcast Morse Code through your IFD? BTW - displaying the Decoded VLOC IDENT data block might also be useful information in determining what your IFD is receiving. This information will be helpful if you have to talk with Avidyne tech support and/or your installer.

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