Originally Posted by
barkerlut
What you hear is the PTU. Since it started mid-flight and continued throughout most probable some lowish pressure in either the green or yellow hydraulic system developed
So the sound which you described is something else then, right?
The noise (PTU according to your expertise) started on the ground while taxiing to takeoff.
Why did the pilots take the risk and still took off without fixing the issue first on the ground?
Was that something illegal? Did they put the people in risk?
The PTU went on long before the flight started and stood on until after the landing.