New Mode S transponder does not show on flight tracking sites.

My installer tells me it is illegal for him to to enable that function

I am really surprised there is such a function in any Mode S transponder! Maybe @GarryIAE will guess what config your installer may be referring to; I know only my GTX330. Whether you are visible on the tracking sites is not configurable in the transponder; it is a function of your altitude, the proximity of their receivers, the squawk, and some other factors.

This might be worth a read.

There are multiple tracking sites e.g. this one which shows a long history for mine (with some unreliable data – example). You can’t stop this other than by flying “below the radar”. Anybody can set up a Mode S or ADS-B receiver… IMHO few people care what you are doing, and plane spotters have been pretty “diligent” for many years. The real privacy issue arises if somebody can see what you file on your GAR form.

I imagine that the tracking site is looking for ADS-B and your transponder has not been enabled for ADS-B? If it is just looking for Mode S and it is a Mode S Transponder you have installed then I cannot see why it shouldn’t see you.

If it is only monitoring ADS-B traffic, then it is probably that the interface you have between the GPS and Transponder has not been certified for your aircraft type and that is why your installer could not enable it?

Yes; good point. The NATS tracking app shows only ADS-B, and to radiate that you need a WAAS GPS connected to the transponder, AIUI.

But FR24 shows both Mode S and ADS-B.

I have the same question. My club’s whole fleet has been upgraded to Trig transponders. I never saw any on FR24 which should locate them via MLAT. They are not even in the Fr24 register.
If this fonction can be disabled, it would explain this.

I think it’s just a matter of time.

Our aircraft with a new Trig Mode-S transponder was only showing up in FR24 when it was flying, but it was not searchable and there was no history about it.

However, after a few weeks it was possible to track it historically and search for it.

I think FR24 takes some time before it adds a new aircraft to it’s search history.

Has the flight ID been programmed into the mode S transponder? AFAIU that is the only thing you need for MLAT to identify and track you.

Maybe that is what the installer did not want to do?

My club’s whole fleet has been upgraded to Trig transponders. I never saw any on FR24 which should locate them via MLAT. They are not even in the Fr24 register.

How exactly FR24 works, nobody quite knows. The main thread on FR24 is here.

It tends to exclude 7000 squawks, tends to not work at low levels (which means the bulk of a given country’s GA may not show, flying at say 2000ft or lower, and this is evident on my FR24 tracks which start and end quite a few nm from the airport(s)), possibly intentionally ignores low level traffic…

On a Mode S transponder you can switch off Mode C (i.e. the altitude readout) but you cannot switch off the Mode S (i.e. the transmission of your aircraft reg). This is why people who want to stay invisible do not install Mode S, and remain either non-TXP (which is severely limiting, except UK OCAS, French OCAS VFR, and some others) or remain with a Mode C unit (which is somewhat less limiting) but which cannot be replaced if it fails except with a Mode C unit of the exact same type.

Personally I don’t agree with invisibility (specifically non-TXP or Mode A) because one day one of these might hit me and then there will likely be two sets of funerals, with the obvious questions being asked, all too late. My TAS/TCAS has saved me from very close encounters several times just this year because the other aircraft was being operated responsibly and was radiating Mode C or Mode S. I believe the main “privacy” thread is here.

And bear in mind anybody can set up one of the receivers and see traffic over a huge radius.

Maybe that is what the installer did not want to do?

Without that, the installation isn’t legal

Dimme wrote:

I think it’s just a matter of time.

Our aircraft with a new Trig Mode-S transponder was only showing up in FR24 when it was flying, but it was not searchable and there was no history about it.

However, after a few weeks it was possible to track it historically and search for it.

I think FR24 takes some time before it adds a new aircraft to it’s search history.

Our 172s (8 of them) where all equipped in 2017 and none of them still appear in the FR24 database.
The flight ID is filled with the registration AFAI can tell from the screen.
I’m puzzled …