GPS->VLOC Capture questions |
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Speedbird1
Groupie Joined: 16 Mar 2020 Location: New Braunfels Status: Offline Points: 66 |
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Posted: 21 Apr 2021 at 10:27pm |
Looking for a little help, please.
Last 3 VOR/DME A approaches I've flown haven't switched from GPS to VLOC. I'm not sure if this is because the criteria hasn't been met or if I had a setting/mis config. In order to test it I was planning on going out and flying the VOR/DME A into KBAZ. assuming that the tuned freq. matches the navaid and morse code is ID correctly then is it fair to say that if I fly the approach starting at YERRI to FAUST then at FAUST I should see it switch to VLOC automatic (assuming I have Auto-VLOC tuning [on] and GPS-<VLOC capture [auto]) Thanks |
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Gring
Senior Member Joined: 30 Dec 2011 Location: Kingston, NY Status: Offline Points: 734 |
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there is a set of criteria that must be met for auto switching and you can find it in the Pilots Guide.
The next leg or the active leg terminates at the FAF The aircraft is on the front side of the approach The aircraft course is within 15 degrees of the final approach course Cross track deviation is less than half a dot The correct station is tuned and identified |
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dmtidler
Senior Member Joined: 12 Feb 2016 Location: USA Status: Online Points: 617 |
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The auto VLOC capture criteria in the latest IFD540 manual revision 7 are slightly different than listed above (primarily concerning the active leg): To trigger the transition from armed VLOC to active VLOC, all of the following capture criteria must be met: The tuned frequency in the nav radio matches that of the approach navaid The Morse code decoded by the tuned nav radio matches the identifier of the approach navaid The aircraft track is within 15° of the final approach course The course to the active waypoint is within 45° of the final approach course The radio deviations are at most 50% of full scale for 5 consecutive seconds The active leg is part of the approach up to and including the final approach fix Based on this, if the aircraft is within the above capture criteria crossing YERRI, the IFD should auto switch to VLOC. For testing purposes, if you select this approach as a VTF approach and FAUST is the IFD active waypoint, then once the above capture criteria are all met, the IFD should auto switch to VLOC no matter how far outside of FAUST the aircraft is. You may want to double check your User and User settings to verify that Auto-VLOC Tuning is On and GPS->VLOC Capture is set to Auto.
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Speedbird1
Groupie Joined: 16 Mar 2020 Location: New Braunfels Status: Offline Points: 66 |
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Thank you.
I did actually read all of these in the manual prior to posting; however, points 3-6 are obscure (to me at least), that's why I'm asking if I cross YERRI (IAF) on a track of 252 heading to FAUST (FAF), assuming the VOR is on the right Freq and morse is ID'd then crossing FAUST I should see it switch automatically? |
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dmtidler
Senior Member Joined: 12 Feb 2016 Location: USA Status: Online Points: 617 |
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It is my understanding that since YERRI and FAUST are both on the final approach course and provided the aircraft is flying along the center of that course capture criteria points 3 through 5 would be satisfied. Assuming the IFD has tuned and correctly decoded the VOR identifier (capture criteria points 1 and 2 satisfied), then upon crossing YERRI, the last outstanding capture criteria point 6 (active leg is part of the approach up to and including the FAF) will be satisfied and the IFD should automatically switch to VLOC at that point. In this described scenario, the IFD automatic switch to VLOC should happen long before FAUST.
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Speedbird1
Groupie Joined: 16 Mar 2020 Location: New Braunfels Status: Offline Points: 66 |
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Thanks. The one that got me is 'The course to the active waypoint is within 45° of the final approach course'. Seems that doesn't make sense in light of the other criteria.
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dmtidler
Senior Member Joined: 12 Feb 2016 Location: USA Status: Online Points: 617 |
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I think that may be the IFD’s specific methodology in determining that the aircraft is on the front side of the approach per the older VLOC capture criteria list.
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Speedbird1
Groupie Joined: 16 Mar 2020 Location: New Braunfels Status: Offline Points: 66 |
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Thanks so much for taking the time to respond. I believe it has not been capturing because ATC keep vectoring me onto the approach right AT the FAF.
I've read somewhere that ATC are supposed to have you established at the gate, which is 2-3 miles before the FAF. Is there any truth to this?
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