On 23 September, Brussels Airlines flight SN2901 from Brussels to Vienna, operated by Airbus A319-111 OO-SSL had to turn back in the morning to Brussels due to a transponder problem, reports La Libre Belgique.
The newspaper reports that the aircraft took off from Brussels Airport at 07:03 local time. The Maastricht UAC (+24,500ft) controller noticed that the position signals appeared on the screen, but not the altitude. Call sign, speed, altitude and vertical speed have always to be displayed.
Flightradar24 playback shows clearly with ADS-B data that the aircraft had a problem to transmit data.
The captain decided to go back to Brussels, where he landed at 07:47 local time.
Both transponders had technical problems, and eventually, Brussels Airlines technicians were able to solve the issue by restarting the electric system.
After refuelling, the aircraft finally took off again to Vienna, a little bit less than one hour later.