What are the "barking sounds" on an A320?
If you have ever traveled on an Airbus A320 aircraft, you must have heard a very peculiar sound before take-off or after landing, a sound that is associated with a dog barking, and which seems to announce that something is wrong with the aircraft. Well, there's no need to be scared, if you hear that noise it means that the PTU is working. But what is PTU and how does it work?