Originally Posted by
pax2908
Pax here - was intrigued this morning by the PTU running continuously during taxi (OK) but also without interruption until ~30 seconds after takeoff. Easyjet, 1st flight of the day (I suppose!).
Are you certain it was the PTU and not an electric motor running? They have different sounds, but I cannot easily explain in text how they differ, except to say that an electric motor driven hydraulic pump has a clean, ‘single’ high sound, whereas the PTU has a deeper ‘multi component’ sound.
Anyway, my guess would be the electric hydraulic pump in the yellow system running. This is done when single engine taxiing, but should be selected off when the second engine has started, before take-off.
If it was the yellow pump, perhaps the crew got distracted and missed turning it off before take-off, then spotted it after getting airborne?