Whirring sound in Airbus aircraft whilst on the ground

[AndoniP]

Hi all,

Apologies if this has been mentioned before, I did do a search... :(

Anyway last week we were on an EZY A319 from Gatwick. Whilst on the ground (and I'm not sure at what point this sound started, maybe whilst pushing back), there was a fast intermittent whirring sound. It sounded like something was moving forwards and backwards, and continued for a good few seconds.

I assumed it was some sort of ballast / CoG device moving into position - not that I'm even sure there is such a thing on aircraft.

Can someone tell me what this is please?

Thanks

Andoni

[Irish_Avro_Driver]

Airbus A320 PTU or...the barking dog! - YouTube

[vs69]

As the video states, its the Power Transfer Unit, used to transfer hydraulic power between the Yellow and Green Hydraulic systems. On the ground you will usually hear it because the yellow electric pump is running and the green isn't. If one engine is running then a hydraulic system isn't powered so again you will hear it run. Most punters on hearing it think its a dog.

The PTU is like a 2 sided pump, the systems are hydraulically independent and it is only a transfer of motive force, not fluid. Hope that clears things up for you.

[Dan Winterland]

Actually. it goes into a test cycle for a few seconds when the second engine (usually number 1) is started.

[AndoniP]

Guys, thanks so much for the explanation!

Much appreciated

Andoni