MLAT for ADS-B Aircraft

[sitko]

I have noticed that here in NW Germany a lot of aircrafts who send full ADS-B position data (says my sbs basestation) are tracked by MLAT (T-MLAT1). I always thought MLAt was for AC that do not send position data (mode-s only). Why are ADS-B AC tracked with MLAT? Thank You!

[Anmer]

Can you provide examples - mode-s hex code/registrations?

[sitko]

Sure: This evening

B-2005
D-ATCE
N-428UP
EI-GDB

All ADS-B AC and T-MLAT1 tracking

Rgds

[Anmer]

Thank you.

I replayed EI-GDB, Ryanair B738, operating Dublin-Munich on 17th Sept 2018 as FR8896 and the return flight as FR8897. I assume these are flights you tracked on BaseStation.

FR8896 left Dublin being tracked by ADS-B F and T radars, changing to T-MLAT1 over North Wales then back to ADS-B radars until Norwich when it switched back to T-MLAT1 until it reached the Stuttgart area. Descending to Munich it was tracked by ADS-B T and then F radars.

The return flight, FR8897, was mostly showing ADS-B radars but there were some stages of the flight where it showed T-MLAT1.

Assuming your BaseStation was tracking the flight's position at the same time as FR24 was attributing the T-MLAT1 radar source, it looks like an FR24 issue. Especially if you tracked other positional flights on BaseStation that FR24 showed as MLAT.

I won't speculate the cause as there could be a number of possibilities.

Thanks for picking this up. Maybe FR24 will appreciate it too.

[sitko]

Thanks Anmer for the confirmation! Yes, it is an ongoing issue - radar switching from MLAT to ADS-B and back. I was also surprised to learn that one of the Top 20 feeders comes right from my area but I have not seen his radar ID on der FR24 screen yet - go figure!

Rgds sitko