A320 - noise on pushback - what was it?
 

I was flying on a Jetstar A320 yesterday morning when I heard a noise I've never heard on an aircraft before while pushing back.

As we were pushing back there was (intermittently) a loud noise sounding like some sort of hydraulic noise (similar to when they open the cargo doors) coming from below me (was in row 17 just aft of the wing) but in an almost "sawing" like pattern (short and regular like someone sawing wood with breaks in between). I checked the wings and there was absolutely nothing going on on either wing to explain the noise and it happened well after all the cargo doors had been closed and well on the pushback.

It ceased as soon as they let us go to start the bird up and the noise wasn't heard again. I fly a lot (admiitedly more on 737s and 767s and not much on A320s) and haven't heard something like it before. Can someone in the know clue me up?

The reason I would like to know is my wife is scared witless of flying and I get her through it by explaining every noise and movemnet that I know in calm terms ("... that's just the landing gear being deployed you can hear ..." etc) and if I heard this again and said "... no idea darl" she'd have kittens (she wasn't with me yeterday).

Please, please search for this, its been asked about a thousand times before! Tightslot - this is definitely one for FAQ's!! :ok:

One of many search results is here http://www.pprune.org/forums/showthr...ght=A320+noise

Not again!!

O.K., just this once..........

It's the P.T.U: the Power Transfer Unit. It's a device which transfers hydraulic power from one system to another, whilst remaining hydraulically de-coupled. Under certain conditions (like the engine start sequence here) it will operate automatically.
We engineers also use it to power up the main hydraulic systems (yellow and green) via a single electric pump (yellow system).

Hope this helps!

Thanks c150 - question answered. Am new to all this and hadn't searched properly. Sorry 'bout that:E.

Thanks to you too FHA:ok: