Strange Noises heard on various aircraft - What are they?
 

Just flown (as SLF) A320 out and A319 back from Frankfurt.On both flights, immediately after engine shut down there was a load noise that I can only describe as a giant trying to rub a stubborn stain off the tail of the aircraft with an enormous chamois leather! It went on for quite a while gradualy getting slower as though the said giant was becoming exhausted. I fly quite a bit but this sound is something I cannot place. Explanation from those that know much appreciated.

Probably the Power Transfer Unit. See also "Barking dog noise"...
Something to do with supplying hydraulic pressure once hydraulic pressure reaches a certain level, due to an engine being shut down.

I asked an A320 type-rated AME exactly the same question about 2 weeks ago....and he said;

"PTU".

So that's 2 votes for that answer.

On the A330 / A340, if it is hot and humid, 'smoke' (actually a fog of condensed water) pours out of the air-conditioning vents immediately after take-off, accompanied by loud bangs and crashes from somewhere in the ceiling. Made my heart beat that little bit faster the first time and have seen people get really panicky. Maybe expand this thread to include 'unsettling' noises on planes?

'Maybe expand this thread to include 'unsettling' noises on planes?'
In which case, how about the sound of the 146/RJ putting in the first stage of flaps? In the cabin it gives a loud roar of descending pitch that makes me think of the gates of hell swinging open.

What about the "buzz saw" on Airbus 319/320 aircraft during takeoff and climb? This was discussed here before and I recall pilots writing, "Yeah, that is the buzz saw" but not much else. Did I see somewhere it was fuel pump noise?

accompanied by loud bangs and crashes from somewhere in the ceiling.

Sounds like pieces of ice exiting from the air con packs.

You can replicate the experience on your home a/c if you set it to a very low temp and then leave the windows open :eek: