OT: Sawing noise?

Old Dec 30, 14, 10:01 am
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OT: Sawing noise?

What's the noise that sounds like sawing?
Normally just before take off, or on arrival at the gate?

Comes from below the passenger deck.

Been meaning to ask for ages.
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Old Dec 30, 14, 10:03 am
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Hydraulic system on the Airbus fleet , sounds like a barking dog.
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Old Dec 30, 14, 10:05 am
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Yeh, can see(hear) the dog likeness too

Just sounds a bit noisy, wonder how it works.
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Old Dec 30, 14, 10:11 am
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It is the power transfer unit. More information thanks to Wikipedia here

http://en.m.wikipedia.org/wiki/Power_transfer_unit
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Old Dec 30, 14, 10:30 am
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i always though it was the flight engineer sawing logs for the engines.....

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Old Dec 30, 14, 10:33 am
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It generally happens on the taxi out to the runway, and therefore coincides with the Crew/Auto safety demonstration. If it's the latter, this can often be completely inaudible. On one of my recent flights as nobody could possibly have heard it, and I almost got up and said that it should be played again, but by then of course it was "Cabin Crew seats for take-off". What would you have done in a similar situation, as it rendered the mandatory safety demo completely useless?
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Old Dec 30, 14, 11:16 am
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Originally Posted by snuffi View Post
It generally happens on the taxi out to the runway, and therefore coincides with the Crew/Auto safety demonstration. If it's the latter, this can often be completely inaudible. On one of my recent flights as nobody could possibly have heard it, and I almost got up and said that it should be played again, but by then of course it was "Cabin Crew seats for take-off". What would you have done in a similar situation, as it rendered the mandatory safety demo completely useless?
I would have done absolutely nothing. You would have been barking to do anything
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Old Dec 30, 14, 11:19 am
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Originally Posted by snuffi View Post
It generally happens on the taxi out to the runway, and therefore coincides with the Crew/Auto safety demonstration. If it's the latter, this can often be completely inaudible. On one of my recent flights as nobody could possibly have heard it, and I almost got up and said that it should be played again, but by then of course it was "Cabin Crew seats for take-off". What would you have done in a similar situation, as it rendered the mandatory safety demo completely useless?
I've rarely heard on taxi but is very common when you arrive on stand.
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Old Dec 30, 14, 11:20 am
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Originally Posted by CocoPops View Post
What's the noise that sounds like sawing?
Normally just before take off, or on arrival at the gate?

Comes from below the passenger deck.

Been meaning to ask for ages.
I've also said 'oh I'll ask on FT later' about that noise, so thanks for reminding me and finding the answer for me.

Personally, I think it sounds more like stuck windscreen wipers but dog barking and sawing works for me too.
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Old Dec 30, 14, 11:24 am
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I had this conversation a while ago with a bloke sitting next to me in the exit row of an EasyBus...

He reckoned it was related to the (apparently common) practice of taxiing almost to the threshold on only one engine "to save fuel", with the noise being the fuel pump working as the 2nd engine was started.

I thought is sounded like BS at the time, but was too polite to say anything but "Oh, how interesting..."
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Old Dec 30, 14, 11:43 am
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Somebody on here once described the sound as a stuck washing machine.
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Old Dec 30, 14, 11:44 am
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Youtube has it.

https://www.youtube.com/watch?v=9ffJgk1-tCA
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Old Dec 30, 14, 11:53 am
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Originally Posted by njf63 View Post
I had this conversation a while ago with a bloke sitting next to me in the exit row of an EasyBus...

He reckoned it was related to the (apparently common) practice of taxiing almost to the threshold on only one engine "to save fuel", with the noise being the fuel pump working as the 2nd engine was started.

I thought is sounded like BS at the time, but was too polite to say anything but "Oh, how interesting..."
The noise is the PTU, not the pumps.

Whilst I don't think it's easyJet SOP to taxi out on one engine, I believe it's becoming more frequent. I've never encountered it on BA. There are potential problems with one engine taxi out- should there be a mechanical fault on the other one, it would cause various issues- taxiing back to stand would be hugely inconvenient for example, and cause delays to other aircraft. Other problems could include encountering a sharp turn in the direction to the other side (which would require increased power from the not-running engine).

Taxiing in after landing on one engine however is quite common practice, and possibly even BA SOP? One BA A320 family Captain I have spoken to said that he taxys back in on one engine regularly.

Perhaps Waterhorse will be able to shed more light.
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Old Dec 30, 14, 2:07 pm
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I've been wondering this for years but never got round to asking. I too have always heard it as sawing. Thanks, OP
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Old Dec 30, 14, 2:25 pm
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It's the sound of shorthaul on the Airbus fleet going to the dogs

Safe & Happy travels

S
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