'TUNE LRA/AYT' - Airbus going into Antalya

[Smooth Airperator]

Flying into Antalya now for almost 10 years, I see this appear on the MCDU scratch pad a lot of the time. Has anybody made sense of it yet?

[wiedehopf]

It reminds you to tune both the VOR located at the airport:
Lara VOR-DME (LRA) @ OurAirports (http://ourairports.com/navaids/LRA/Lara_VOR-DME_TR/#lat=36.906905318390336,lon=30.798316955566396,zoom=12,type= Satellite)

[Smooth Airperator]

But we do. Depending on the procedure we might put LRA into VOR1 and AYT into VOR2. It then complains again, wanting AYT into VOR1. We do that then it wants LRA in VOR1 again! I will try it again just to be sure next time.

[FlightDetent]

I've seen it happen many times too, not very frequently but repeatedly - yes. It is not a bug, it's feature.

The technical reason is that FMS logic suggests a certain NAVAID based on the procedure activated in the system. If you keep the RADNAV pg empty, or erase (*) whatever you have there when the message comes up, you would be able to observe what the FMS believes is the appropriate tuning.

It cannot be scrutinized from over here, as we have no way of knowing what procedure, leg sequence and active waypoint you had going on at the moment. Even if we did, we would need to see the definition of the legs (**) from the database dump, which may or may not include a "reference navaid" - that's where the FMS gets ideas from.


* = SOP, common sense, and airmanship requirements permitting
** = the FM DB coding does actually not consist of connected waypoints (as we may percieve), but track-to-WPT segments which are mostly made invisible to the pilot.
http://galileo.cs.telespazio.it/medusa/PANS%20OPS%208168%20Advanced%20Class%20Rabat%2016-27%20March%202015/Training%20material%20&%20exam/Path%20Terminator_1.0.pdf

[Fursty Ferret]

Just leave it to auto - tune and you'll get relevant guidance.

[applecrumble]

Somebody mentioned to me that it was to do with the limited number of VOR heads available for position updating. So it is asking you to release the tuned VOR so it can use it for position updating in areas where there are limited DME's to fix the position. Could be wrong though.