Originally Posted by
cadetdrivr
FWIW, it's actually a PTU (power transfer unit) that you are hearing. It connects the two main hyd systems (no fluid transfer) so one side can automatically power the other when differential system pressure exists. That's why it sounds like a chainsaw as it instantly cuts in/out repeatedly when one system has slightly less pressure as a result of an engine being shut down.
And yes, it seems many Airbus operators have different procedures to deal with it during single engine taxi or parking.
Correct. If one simply turns on and leaves the electric pump on until everything is shut down (or before taxi out single engine), the dogs won't be barking on that flight. Of course, you also have to remember to turn it off.