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Mode S-ES, Selected altitude, and GTN vertical profile

Ibra wrote:

naybe they (or radar system) does not care where the blue or magenta bugs sits as long as it’s bugged outside en-route airspace

Could be !

EGTF, LFTF

Ibra wrote:

Yes all aircraft installation is Garmin, if there is something fishy with install it would be from STEC3100 which is not made by Garmin but denopa mentioned it follows the blue bug, so AP/FD knows which one to fly and ATC should get “MCP selected altitude” on their screen…

Yes, but the transponder doesn’t know which one the AP follows… And it is the transponder that radiates the information.

ELLX

@lionel, well spotted, I bet denopa should send you a cheque very soon

Last Edited by Ibra at 20 Sep 15:07
Paris/Essex, France/UK, United Kingdom

lionel wrote:

Yes, but the transponder doesn’t know which one the AP follows… And it is the transponder that radiates the information.

AFAIU the documentation, if the transponder doesn’t know it should transmit that fact and in that case the ATC radar system should use pilot selected altitude.

ESKC (Uppsala/Sundbro), Sweden

I have seen the same behavior in our Cessna 172S when flying in Germany, I never change the altitude select nowadays before I’m cleared to the new altitude/FL.

How is the altitude preselect fed to the transponder?

This implies Enhanced Mode S is enabled and the connection exists for the data. Elementary Mode S does not radiate this stuff.

Funny; we did this here.

Administrator
Shoreham EGKA, United Kingdom

martin-esmi wrote:

I have seen the same behavior in our Cessna 172S when flying in Germany, I never change the altitude select nowadays before I’m cleared to the new altitude/FL.

What behaviour? That both the altitude preselect and the VNAV target are transmitted? Does your 172S have the KAP140 or the GFC700 A/P? I’ve also got queries from ATC regarding the altitude preselect when flying a 172S, but not about the VNAV target.

ESKC (Uppsala/Sundbro), Sweden

Airborne_Again wrote:

What behaviour? That both the altitude preselect and the VNAV target are transmitted? Does your 172S have the KAP140 or the GFC700 A/P? I’ve also got queries from ATC regarding the altitude preselect when flying a 172S, but not about the VNAV target.

I meant that the altitude pre-select is transmitted (I believe it was). We have the GFC700 A/P.

martin-esmi wrote:

I meant that the altitude pre-select is transmitted (I believe it was).

Oddly enough there’s no explicit mention of this in the C172S AFM(S). There is one supplement that lists the various standards and TSOs that the installation meets and it does mention “enhanced surveillance”, but that’s all.

ESKC (Uppsala/Sundbro), Sweden
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