Aircraft Identification

[FLTID]

Hi All,
could anyone out there tell me more about how the Mode S aircraft identification gets entered into the aircraft systems and subsequently downlinked in a Mode S return?
rgds FLTID.

[Radarspod]

Depends on the avionic fit of the aircraft as to how you enter into the transponder - this is my understanding, but not an expert on how data gets into the transponder:

a) If smaller GA type transponder, can be entered via the controls on the front panel. This should be the aircraft registration (e.g. G-ABCD) unless an ICAO callsign has been allocated, in which case that should be entered.

b) larger commercial aircraft normally have a control panel for either the FMS or the transponder, allowing the pilot to enter the ICAO callsign at the beginning of the flight prior to pushback. It may be that it can be automatically transferred to the transpodner via the FMS.

However it is done, the Aircraft ID (either registration or ICAO callsign) populates Comm-B register BDS 2,0 using IA-6 encoding as per Annex 10 Volume 4. It is a European requirement for all Mode S transponders to be able to supply this register containig the Aircraft ID.

The ground Mode S interrogator will request the BDS 2,0 register automatically during first detection into radar cover. Once received, the ground interrogator will not ask for it again unless the track is lost then re-acquired, or the transponder indicates that the Aircraft ID has changed.

Hope this helps,

RS

[FLTID]

Thanks RS for the info.
If you are entering a REG it must be without the "-" i.e. GABCD.
The reason for my question is that ATC systems will couple the radar track to flight plan data and subsequently display radar label on the screen by matching the downlinked aircraft identification with the Callsign Filed ATC flight plan. If the two do not match then no radar label. So if aftrer "finger trouble" in the cockpit xxx123 is entered instead of xxx124 this could potentially cause a problem. If the aircraft identification was automatically entered in aircraft systems from the filed flight plan there would be less errors
rgds FLTID.

[HEATHROW DIRECTOR]

What was wrong with the old-fashioned system of the ATC computer pairing a squawk with the callsign from a flight plan, which then appeared on the radar? No possibility of any errors provided the pilot selected the correct transponder code.

If you watch Mode S readouts of aircraft callsigns as entered by crews you'll understand my concern!

[Minesapint]

It goes into the FMS and is transmitted via Mode S or ADS-B equipment. At least for larger aircraft. Probasbly via the transponder for smaller types.

[FLTID]

Hi Heathrow Director,
the problem with SSR codes is there is only 4096 codes and SSR code conflicts cause incorrect correlation and increased RT due to Controllers having to change conflicting codes.

Hi Minesapint
thanks for the reply.....but how does it get into the FMS, manually typed by the Pilot or automatically from the flight plan?

rgds FLTID

[Casper48]

Hi Director,

Are pilots flying on Heatrow not abble to write their own name?:ugh:

[callum91]

I have a Mode S transponder on my C150 - does this provide ATC with more information (e.g. Registration) than the normal mode C transponders or is this yet to be implemented on the ATC side?

[Defruiter]

Yes, we can get your registration (in Terminal Control) with mode S. Helps with those pesky infringers :}