Mode S Code Privacy Policy

Mode S (or is it ES or ADS-B?) literally also radiates the callsign, which for GA is the registration.

lionel wrote:

Mode S (or is it ES or ADS-B?) literally also radiates the callsign, which for GA is the registration.

Mode S does. (And of course ES and ADS-B as well.)

I am not aware of any European country which publishes a Mode S 24 bit code → tail number database, but there are ways you can get it indirectly. For example the UK CAA G-INFO database shows the 24 bit code in the database, so this could be scraped easily enough (about 20k planes I think). However, I just looked up mine which went G-reg to N-reg in 2005 and it no longer shows the 24 bit code, but G-OMAO which is a current one does show it

There are probably other countries with similar databases which could also be scraped.

I am sure publishing the data would fall foul of GDPR in a lot of places – just about everything in Europe has some GDPR angle – even if a lot of it is only somebody’s imagination / wishful thinking The UK CAA’s database, which in most cases shows your home address, seems to operate under a “legitimate interest” GDPR exemption (there is also a UK law mandating the publication of the data).

With N-reg there is as you say an algorithmic relationship between the 24 bit code and the tail number, which enables e.g. old Avidyne MFDs to display tail numbers of TAS6xx-detected targets, but only N-regs. I have flown in such an aircraft; @cobalt may remember. Nice feature. But for non-N-regs the MFD would need to contain a database of 10s or 100s of thousands of planes.

Very little “GA” has ES (Enhanced Mode S). It was/is mandatory, IIRC, for stuff like TBM, PC12 and above (250kt TAS + etc). The immediate issue is that you need avionics that can emit the various parameters like autopilot mode, in ARINC429 or perhaps RS232, although a GTX330 will happily radiate all that you feed it with. At one stage EASA banned the radiation of this extra data. @wigglyamp will remember this well; his company published an article saying they had to remove the GNSxxx-GTX330 RS232 connection in some large number of installations after EASA came up with that “idea” Later Garmin came up with new GTX330 firmware which had a config option to not radiate the “illegal” data. N-regs were never affected by this.

The tail number radiated by ADS-B can be freely configured AFAIK – same as the tail number in say a GTX330 (which has a config for both the tail number and the 24 bit ID). Maybe some ADS-B OUT systems pick the tail number off the Mode S radiation; in Europe you cannot have certified ADS-B OUT without also having a Mode S TXP.

In Sweden mode S codes are assigned based on the aircraft registration.
The mapping is described in this document
https://www.transportstyrelsen.se/TSFS/LFS%202007_31.pdf [Swedish]
LFS_2007_31_pdf

AIUI in France when you install a mode S especially a Garmin 330 with ES you sign on with an agency DSAC or OSAC or it could be one of the many other acronyms. Your aircraft registration or however you want to be called ( call sign) . ATC/ATS then calls you by that.
I think you.have to update the information every so often at a transponder check.
I can’t be clearer as our maintenance facility just handles it.
Whether this information is published, openly, I doubt. Who would be interested and why?

is there a means of the public being able to determine the aircraft registration by receiving the Mode S code or do some countries not provide this information to the public because of privacy or other policy?

In UK, you have G-reg & HEX in G-INFO website (which is like N-tail search), if you are using some approved ADSB emitters without ModeS m you can even input your own code (had one traffic following me once which turns up to be myself due to double target setup and my fat fingers)

In France, you can request acess to the register but it does not have HEX code, anyone can still request that information from “regional NAA” by email but I doubt there is a one to one mapping as for N-tails

I gather it’s easy for observers and spotters to easily build on on the fly from HEX/REG radiated for aircraft equipped by ModeS? you can even set alerts when one of the two show up on tracking websites: you can’t fly in darkness these days like Escobar, even spotters are getting into catching anything fishy versus normal, showing up on radio or radar with SkyWalker call sign will get you lot of StarWars fans on tarmac

NCYankee wrote:

Are you saying that using an ICAO 3 letter call sign in lieu of the registration is not allowed? In the US, companies such as ForeFlight are permitted to provide private owners with a third party call sign that can be used in a flight plan, telephony, and replaces the FAA N number in the transponder.

Sure it is allowed, some ATOs have their own operator call signs. But there is no third party call sign feature like ForeFlight offers.

The swiss aircraft registry shows the aircraft address when you typed in the HB-registration.
With advanced search, one can also search the other way: https://app02.bazl.admin.ch/web/bazl/en/#/lfr/search
E.g. 4b28d9 is currently flying, according to globe.adsbexchange.com and it shows the callsign and operator, etc.

Switzerland is weird in privacy anyway. You can do the same for license plates unless people opt out. I have no idea if the aircraft registry also allows opting out.