Airbus A320 "sawing" noise when on the ground

[Kiltie]

What's that "sawing" noise I sometimes hear when taxiing?

Any ideas?

[Boatbuoy]

It been discussed on here a few times before. Last time it was referred to as a barking dog!

If I remember correctly, it's a hydraulic pump equalizing pressures in the various systems.

[0a]

Thankyou for asking this!

[Boatbuoy]

Found it, see here:

http://www.pistonheads.com/gassing/topic.asp?t=132...

[nessiemac]

It's the noise from a hydraulic component called a PTU (power transfer unit). Situated at the rear of the main landing gear well. Basically a hydraulic pump that is used to transfer power between 2 hydraulic systems in the event of one system dropping below a certain pressure. Sort of a back up if one system loses it's own engine or electrically operated pump. A very annoying and uncomfortable noise to say the least!!

[IroningMan]

I always assumed it was the handbrake...

[Kiltie]

Thanks for the replies folks.