What I find puzzling is why the TCAS in that Cessna 400 was showing only N-reg tail numbers, when G-reg tail numbers have to be emitted on Mode S also.
There seems to be some confusion between Mode S Flight ID and Aircraft Address. The aircraft address is the unique 24bit address assigned to the airframe (which in N-reg land can be easily mapped to the N number). The Flight ID is the callsign of the flight - which may or may not be the same as the registration.
For situational awareness you would ideally display the Flight ID/callsign on the ACAS map.
Mode S elementary surveillance (what most of us have) publishes a number of fields:
... and probably a few more things
I'm pretty sure the only reason the Avidyne/Garmin ACAS devices don't display the Flight ID is that the specs say the necessary interrogation messages shall only be generated by ground based systems. The Aircraft address is published in every Mode S response, so it's easy to get hold of.
OK; that makes sense. Thanks.
The Mode S transponder has the registration number stored in it as configuration data, In the case of the Garmin transponders, if the registration is US, it has the N number determined from the aircraft address or visa versa by the algorithm, whichever value is entered first, the other is calculated. If the aircraft is used commercially, a configuration is set to permit the pilot to enter a flight ID on a per flight basis instead of the registration number. The flight ID field is 8 alpha characters and is either set to the stored registration number or the value entered by the pilot if it is configured to be entered and is entered.
HB reg tail numbers can also be algorithmically determined from the transponder address and vice versa.
Tail numbers in the form HB-XYZ (where X, Y and Z are letters) result in the following address: 0x4b0000+(X-'A') * 26 * 26+(Y-'A') * 26+(Z-'A').
Tail numbers in the form HB-n (where n is a decimal number, usually 3 or 4 digits long) (these are used for gliders and motor gliders) result in the address: 0x4b0000+26 * 26 * 26-1+n
Flightradar24.com reports call sign, registration, mode S ID, heading, altitude, speed, transponder code, position.....along with departure airport, destination, planned track (from their flight plan I assume).....where do they get their real-time data from? (Real-time for all except aircraft in US airspace where it is delayed by 15mins I think)
Flightradar24.com reports call sign, registration, mode S ID, heading, altitude, speed, transponder code, position.....along with departure airport, destination, planned track (from their flight plan I assume).....where do they get their real-time data from? (Real-time for all except aircraft in US airspace where it is delayed by 15mins I think)
I think this is a merge of a number of different data sources -
For some (many?) registries the mapping is a simple algorithm. For others it has to be looked up. Does anyone know of a centralised database for these lookups (other than the spotter sites)?
AnthonyQ - the FlightRadar24 source is hundreds of ground-based (probably close on 100% home-based) ADS-B receivers like the SBS or AirNav RadarBox.
FlightRadar24 have a page on how to contribute to the data feed.
And to chip in on earlier discussion of aircraft flight ID - my understanding (my a/c only has Mode C, but I have owned an SBS since 2008) is that all Mode S transponders have the ability for pilot setting of the flight ID.
This allows operators with an AOC/issued callsign to enter the flight number into the transponder for each flight. For non-AOC/issued callsign operators, the aircraft registration, with no spaces or punctuation, should be entered as the Flight ID. In some jurisdictions the installer is supposed to set the a/c registration and then inhibit pilot selection of any other flight ID.
Some transponders, including the Garmin GTX330, can be set to automatically provide an N-reg tail number from the 24-bit/hex code. This only works for N-reg - the reasons for this have already been discussed in this thread. That alone probably explains why N-reg aircraft are better at providing their correct registration to other Mode S observers.
jwoolard: do you know any other country than N and HB which have an algorithmic mapping from registration to mode S address?
jwoolard: do you know any other country than N and HB which have an algorithmic mapping from registration to mode S address?
No - those are my 'some'. I would guess that many countries implemented it this way - it makes the assignment process much easier.
Turkey /(TC) apparently; five bits encode each letter of the suffix, 1 means A, 26 = 0x1a means Z. Their allocation (0x4b8000) has 15 bits, so this just fits.
