That is indeed the yellow system AC motor hydraulic pump whining, you hear a noise which sounds like an air tool in some parts too, just after takeoff when the gear is retracting and just after landing, that is the PTU
You often hear this sound prior to start-up. It's quite noticeable on some of the older 146s. I don't know for certain, but I think it's the AC pump, which is an electrically-driven hydraulic pump which the flight crew often set to automatic, so it starts running if the hydraulic pressure needs topping up.
That is indeed the yellow system AC motor hydraulic pump whining, you hear a noise which sounds like an air tool in some parts too, just after takeoff when the gear is retracting and just after landing, that is the PTU
grinderbroweng 2 years ago
You often hear this sound prior to start-up. It's quite noticeable on some of the older 146s. I don't know for certain, but I think it's the AC pump, which is an electrically-driven hydraulic pump which the flight crew often set to automatic, so it starts running if the hydraulic pressure needs topping up.
rog146200 2 years ago
Thx for the answer!
delta12H21 2 years ago
I Heard that sound too, with the pre flight checks and landing. I don't know what it is but it's not the only one :P
PHBradley1 2 years ago