Sawing up an A319 just after it's parked?
 

Been doing a bit of positioning up and down twixt LHR and MAN lately on BMI A319s, and I can't help noticing that shortly after they've parked it, a sound comes from underneath the floor which sounds for all the world like somebody's sawing the thing up. Wossat?

it's the hydraulic power transfer unit - PTU. Shouldn't really be operating unless the yellow system electric pump has been turned on, perhaps due to single engine taxiing.

It will also operate when the loaders activate the opening of the cargo doors to get out your luggage, irrespective of taxi practices.

Sorry, but not true. PTU-Funktion is inhibited when the Yellow electric pump is in operation to open/close the cargo doors.

IFix

Sorry, you are of course correct, the Yellow system Electrical pump powers the hydraulics to open the cargo doors. No longer fly the 'bus - how quickly one forgets detail....

Thanks to all!

Yup, usually due to the SE taxi procedure. On stand the procedure is Ylo Elec Pump OFF, Eng 1 Shutdown which finds the Ylo(Eng2) hyd system now powered via the Ptu from the running down Eng1 (Green) hyd system and is so until 5% or so N2 whereupon it all dies.

Cheers,
mcdhu

I reckon that about 50% of A320 that arrive on gate after a single engine taxi have the PTU running. Our crew have a drill to turn on the Hyd pump before shutting down Nbr 1 engine, but turning the pump off is not in the shutdown drill.

But it is in the SE Taxi Procedure at 3.4.90 which says:

"At parking :

-Y ELEC PUMP OFF

-ENG 1 SHUT DOWN"

Cheers,
mcdhu