I once had a positioning colleague enter the flight deck after landing, asking if everything was alright, because he heard the PTU barking
continuously during the whole approach.
Also heard similar comments from cabin crew on a different flight, with a different A319 aircraft.
On both occasions there were absolutely no indications of any hydraulic problems in the flight deck. So the PTU seems to be running a0t times without any indication to the pilots. I haven't seen that explained yet
