Question for A320 pilots

[Stinkbug]

Just a quick question for those with A320 time...what is the noise you hear on the ramp while waiting for pushback...sort of sounds like a zipper being zipped. Some kind of pump I presume...just curious. Sorry for putting this in the majors board but wasn't sure where else to put it.

 

[Amish RakeFight]

Its the Power Transfer Unit (PTU) powering the hydraulics.

 

[hockeypilot44]

PTU - power transfer unit. Transfers hydraulic pressure, but not fluid from yellow system to green system and vice versa. You will hear it with one engine running unless the yellow electric pump is turned on. You will also hear it with the yellow electric pump turned on and no engines running.

I'm typing this off the top of my head. I think it is accurate. Someone feel free to correct me. I know there is more to it. I am just giving very general info.

 

[starchkr]

Waiting for pushback...was it while the cargo doors were closing after final bags were loaded? If so, it could be the yellow electric pump. You said on the ramp, are you outside then? Maybe the yellow electric pump and the fuel pumps running and creating what sounds like the noise you mention. PTU is a good possibility if the first engine is started, OR after the final engine is shut down, but not with the yellow pump operating at the gate with no engines running, unless just after shutdown of the engines. A zipper though, i can't remember hearing that noise, the PTU sounds like a slow hack saw cutting something, or a "dog barking" as many customers reference to it.

That's all i can think of...

 

[Stinkbug]

Thanks for the replies fellas. I can't think offhand if I'm hearing the sound before or after the engines have been started. It's just something I hear a lot as a passenger airlining to work and I've been asked by passengers sitting next to me what's causing it...at least now I'll have something semi-intelligent-sounding to tell them

 

[AKAAB]

It's a zipper. That's why the guy next to you asked for a blanket.

For fun, you can tell your fellow passengers that it's a German Shepard that got lost when it was a puppy and has been living on peanut crumbs and spilled bloody mary mix under the floorboards ever since.
:beer:

 

[JJET44]

It's a zipper. That's why the guy next to you asked for a blanket.
:beer:

LOL!!!!!!!