Aircraft Noises In Cabins

[Ifield Lad]

Having flown a reasonable number of times I am aware of associated sounds/noises of gear extending/retracting, flaps extending/retracting etc.
However at the end of a recent flight on an Airbus 319, during the taxi to stand, the sound of what I first assumed to be the flaps retracting appeared to go on for some considerable time and made a different sound. The only way I can describe it is that similar to when sawing wood. Idle curiosity but what would that have been?

[perantau]

If overhead, maybe there was ice in the air conditioning ducts?

[fa2fi]

Most likely the power transfer unit, part of the hydraulic system. It transfers hydraulic power between the two main hydraulic systems when it senses a difference in the two systems. You'll often hear it during taxi in an out if a one engine taxi in or out is performed as only one engine driven pump is running this that hydraulic system is being pressurised (green). The PTU takes some of that power and pressurise the yellow system. It may be heard at other times but it is most common at taxi.

[flarepilot]

fa2fi , I think you are right

[Agaricus bisporus]

The A320 "barking dog" is, as said above, the PTU doing its job.

[spottilludrop]

Its possible it actually was real dog barking some dogs don't enjoy flying and let you know about it especially if they have been given a seat in the hold which means of course they cannot put their head out of a window which is something a lot of dogs enjoy when travelling

[Ifield Lad]

Many thanks for the responses.

[Agaricus bisporus]

Its possible it actually was real dog barking some dogs don't enjoy flying and let you know about it especially if they have been given a seat in the hold which means of course they cannot put their head out of a window which is something a lot of dogs enjoy when travelling

I'm shocked at your disrespectful attitude towards the cabin crew. Were you flying BA by any chance?

[WHBM]

I think that's A320 hydraulics noise thread No. 1000 :)

The other regular one, alas less now than previously, is the BAe146 flap extension/retraction howl. Apparently when the prototype first flew this noise was quite a surprise. It's a harmonic that develops at certain airflows between the inner flap edge and the wing root. After many comments BAe developed a modification to overcome it, but it weighed 100kg, two passengers, and as far as I know no operator took it (except maybe the Royal Flight aircraft).

I'm surprised Airbus haven't developed a mod for the hydraulic noise.

[spottilludrop]

Im not in the least surprised ,why should they ? Im sure 99 percent of paxs dont know and could not care less, its just another strange noise they may hear now and again whilst on board