A319 noise
 

I've noticed that after landing, and whilst taxing on an Airbus 319, there is a strange noise, which could at best be described as a "sawing" noise.
This appears to be coming from under the cabin floor, somewhere around the wing root area.
I was just wondering what this is.
(and for any journo's reading, it's probably not a stowaway trying to get out of the baggage hold)

PTU in operation.

Thanks F3.

(although I must admit, I did have to look up PTU on Google). We don't have them on Helicopters!

A319
 

You'll get the same sound on start-up, after one engine has started and before the other. The system does a self-test to check operation of it.

Or it could be someone with a saw....that was the conclusion among the pax sitting around me coming onto stand in Zrh on a BA 319 last Friday. Someone was stuck in the hold and they were trying to get out. :}