PPRuNe Forums - NAV AIDS ident in glass cockpit aircraft

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lion-g

28th Dec 2017 10:29

NAV AIDS ident in glass cockpit aircraft

Hi guys,

I am curious on how the MMR and FMGS ident a nav aid (VOR/NDB) in a glass cockpit aircraft.

My Guess is that it is via the Morse code transmitted and with a built in decoder coupled with BITE test.

Can someone help to confirm the above?

Below the glide

28th Dec 2017 20:51

It works the same way you listen to an ident. Listen, decode and announce.

MMR works similarly the same way. It has a matched database, listens, matches and displays.

ZeBedie

28th Dec 2017 20:54

I'm not sure the database bit is relevant - it'll display the ident based on the morse and nothing else - if the morse is wrong, then that's what is displayed, which is what you'd want, isn't it.

lion-g

29th Dec 2017 00:38

Hi guys,

Thanks for the replies.

I am sure everybody has encountered a tuned NAVAID with the same frequency but wrong ident.

From what I have gathered, FMGS uses the database to compare and “display” the ident based on the “nearest” navaid in the database.

I am curious on finding out how the MMR TIT the navaid “correctly”. Sometimes, only the tunes frequency is displayed on the PFD and we will revert to voice ident.

Was wondering how MMR does the TIT on our behalf.

Cheers

Fursty Ferret

29th Dec 2017 16:13

Don't know but it definitely does it by identifying the Morse as I've occasionally seen it indenting test.

Intruder

29th Dec 2017 18:54

From the 744 FCOM:

Quote:

The Morse code identifier of a tuned VOR, ILS, or ADF can be converted to alpha characters. The decoded identifier displays on the PFD and ND. Monitoring this identifier ensures correct navigation radio reception. The identifier name is not compared with the FMC data base.

Due to the large variation in ground station identifier quality, the decode feature may incorrectly convert the intended identifier name. Examples: the Hong Kong localizer “KL” may show as “KAI”, or the Boeing Field ILS may show as “QBFI” or “TTTT” instead of “IBFI.”

lion-g

31st Dec 2017 00:24

Hey,

I am so wrong !
Thank you for the reference and have a great new year to all !

Cheers

Uplinker

1st Jan 2018 14:04

The FMGS (Airbus) will auto tune the next VOR/NAVAIDs it thinks will be useful, and it gets the frequency from its database.

Then, as others have said, it idents the navaid by listening to the Morse code, and displays the result. If reception is poor, the NAVAID ident might be incorrect - for example BNM instead of BNN.

We usually know which VOR(s) will be auto-tuned next and therefore notice the correct frequency appearing, but the ident is sometimes wrong. When we listen ourselves to check, this is usually due to distortion or low level of audio signal.

RVF750

1st Jan 2018 15:18

.. -- -. --- - ...- --- - .... . .-. ..- ...- . -.-. .. -.-. .- -. ..- --- .. - -- -.-- ... .-.. ..-.!

Sorry, some old git like me had to say it. I often find I can just push the button and get a good ident before the automatics do it. So I do. Happy New Year everyone. Especially those that actually touch the controls and keep their skills up once in a while!

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