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Old 3rd Sep 2017, 20:31   #1 (permalink)
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A320 VOR approach

So you are flying a fully managed VOR approach and the cleaner at the airport unplugs the VOR transmitter (or you pull the VOR1/2 CBs for some reason).

What will happen?

Will the a/c continue with its programmed "overlay approach"

Thank you in advance
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Old 3rd Sep 2017, 20:54   #2 (permalink)
 
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I guess as soon as you see FINAL APP, you have the NAV and VNAV solution in the box....
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Old 4th Sep 2017, 05:01   #3 (permalink)
 
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It will continue like nothing happened, because the NAV mode as no connection, at all, to the VOR receivers.
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Old 4th Sep 2017, 12:35   #4 (permalink)
 
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Under FAA rules you cannot continue the final segment without the VOR raw data.
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Old 4th Sep 2017, 22:36   #5 (permalink)
 
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The question should really be what should the crew be doing? If the VOR is no longer working then the ident on the ND won't be displayed. You no longer have raw data and you should be going around.
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Old 6th Sep 2017, 10:31   #6 (permalink)
 
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Which is correct but somewhat anachronistic considering the reliability and accuracy of GNSS navigation, which is what the aeroplane is using to navigate and follow the overlay (assuming GPS installed of course).
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Old 6th Sep 2017, 15:11   #7 (permalink)
 
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When VOR approaches were also "...or GPS" the final approach sensitivity, accuracy, and alerting went to approach mode (RNP 0.30). Without overlay LNAV remains in terminal mode, which is insufficient for the final approach segment.
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Old 6th Sep 2017, 16:34   #8 (permalink)
 
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Now that, aterpster, is an interstinf fact I'd never been told. At one time the schoolhouse taught fly the FMS as an overlay, don't be concerned with the VOR raw data. Then, RC changed the FMS LNAV database on VOR and NDB approaches to note "for reference approach only" meaning raw data required. Now, I know why.
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Old 7th Sep 2017, 09:56   #9 (permalink)
 
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You continue because the approach is not being flown wrt the VOR beacon, it is merely the nav system following the VOR track as shown on the plate and kept accurate by GPS. You have no monitoring but neither can you monitor a GNSS approach except by the system maintaining the correct RNP. Its in the FCOM.
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Old 7th Sep 2017, 13:32   #10 (permalink)
 
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I can only speak to FAA policy. The final segment of a VOR approach must use VOR raw data. In terminal sensitivity LNAV is not VOR raw data.

Having said that, if any given commercial operator can get ops specs approval to use LNAV in terminal mode (RNP 1.0) in lieu of VOR raw data, then an exception has been granted, right or wrong.

We all know that LNAV in the terminal mode will likely do a better job of flying the final approach segment than tracking raw VOR, but the integrity and alerting will be lacking. And, that will probably never matter.

How many VOR approaches are flown these days anyway?
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Old 7th Sep 2017, 20:12   #11 (permalink)
 
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Dunno about others, but on our A320s the VOR approaches are coded in RNP 0.3 and the aircraft automatically switches to that, was the same on the 737 as well. As VOR is often one of the back up approaches for an ILS here they are certainly flown on a semi-regular basis.
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Old 8th Sep 2017, 07:03   #12 (permalink)
 
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Quote:
How many VOR approaches are flown these days anyway?
Quite a few in some parts of the world. The question I have to ask is that if flying a fully managed approach and the navaid in question did stop transmitting, how many pilots would notice?
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Old 8th Sep 2017, 07:23   #13 (permalink)
 
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Those who do their job...
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Old 8th Sep 2017, 13:24   #14 (permalink)
 
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Quote:
Originally Posted by Denti View Post
Dunno about others, but on our A320s the VOR approaches are coded in RNP 0.3 and the aircraft automatically switches to that, was the same on the 737 as well. As VOR is often one of the back up approaches for an ILS here they are certainly flown on a semi-regular basis.
Is your database supplier Jeppesen or LIDO? Jeppesen doesn't code VOR approaches for LNAV RNP 0.30 for their public database. (unless they are overlay; i.e., "...or GPS.) Perhaps they do for a tailored airline database.
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Old 8th Sep 2017, 16:32   #15 (permalink)
 
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As far as i know LIDO, well, we do use their flight planning system, charts, engine out procedures and i guess their FMC databases as well. However, with Jepp they did code it the same way for us. Might be tailored, or just a difference between europe and the US. Heck, even in the old non-gps classics it was coded in 0.3, same as any other NPA. But back then we certainly bought tailored stuff from Jeppesen, their airport booklets (one small book with all charts in the correct order per airport) were great, much better than those chart binders our colleagues at other airlines used.
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Old 8th Sep 2017, 23:09   #16 (permalink)
 
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I flew the early 767 1984 through mid 1986. The pre-GPS FMS was like a Radio Shack toy computer. When we had to fly a VOR approach the approach was in the database. The PF used the database approach because tracking was smooth whereas the VOR was awful. The company required the PNF to monitor raw data, which was easy in the 767. We didn't know what RNP 0.30 was in those days.
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Old 9th Sep 2017, 14:08   #17 (permalink)
 
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If you read your FCOM, you will see that the Crew should continue.

"VOR, VOR/DME, NDB or NDB/DME approach procedures may be performed, in NAV, or NAV and FINAL APP mode, provided AP or FD is used, and:
‐ GPS PRIMARY is available. In this case, the reference NAVAID may be unserviceable, or the airborne radio equipment may be inoperative, or not installed, provided operational approval is obtained."

Straight out of FCOM Limitations - Auto Flight.

For the people who want to argue and say, What if you don't have GPS Primary.
The next line says, if you don't have GPS Primary, then you need the NAVAID for Raw Data.
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Old 9th Sep 2017, 16:06   #18 (permalink)
 
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That's the aircraft limitation. The relevant authority may have a different view.
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Old 10th Sep 2017, 00:46   #19 (permalink)
 
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Quote:
Originally Posted by IBE8720 View Post

For the people who want to argue and say, What if you don't have GPS Primary.
The next line says, if you don't have GPS Primary, then you need the NAVAID for Raw Data.
Well, they have it half right.
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Old 13th Sep 2017, 05:07   #20 (permalink)
 
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Originally Posted by akindofmagic View Post
That's the aircraft limitation. The relevant authority may have a different view.
That is why it says in the LIMITATIONS-: 'provided operational approval is obtained'.
eg: My airline does not require the VOR to be operative for the EDDF VOR RWY07C. We have operational approval.
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