Aquasky18
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a330 swishing/hissing noise during taxi

Sat Apr 28, 2018 5:53 am

Does anyone know what the swishing/thumping noise that can be heard when sitting over the trailing edge of the wings on the a330 during tax is caused by? It sounds similar to the clunking noise made when the brakes are applied or released on the a320, but has a unique hissing/swishing sound, similar to fluid moving through a hose, that can be heard immediately before the thump. I've flown on the a340 as well, but have never heard it on that aircraft- only the 330.

you can hear it very clearly in this video https://www.youtube.com/watch?v=-vhLxEkArtE. The best example is at 10:47, but it also happens at 4:39 and 11:32.

Any thoughts?
 
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Starlionblue
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Re: a330 swishing/hissing noise during taxi

Sat Apr 28, 2018 6:08 am

We can't hear that from the cockpit so I'll have to guess that it is something to do with a hydraulic pump turning on momentarily. Or it could be compression of the oleos with braking,
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JAGflyer
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Re: a330 swishing/hissing noise during taxi

Sun Apr 29, 2018 1:32 am

As you seem to hear it from over the wing (with the hydraulic system right below your feet) I'd say it has to do with movements of fluid, possibly different valves changing position to direct the fluid to a specific system.
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AA737-823
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Re: a330 swishing/hissing noise during taxi

Wed May 02, 2018 10:04 am

It's the brakes.
There's actually a remarkable quantity of fluid going back and forth when brakes are applied or released, especially on a big girl like the A330.
The hydraulic lines and metering valves are in the main wheel well, so you get to hear all of those things going on when seated thereabouts!
 
Lightning12
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Re: a330 swishing/hissing noise during taxi

Wed May 02, 2018 11:25 am

Aquasky18 wrote:
Does anyone know what the swishing/thumping noise that can be heard when sitting over the trailing edge of the wings on the a330 during tax is caused by? It sounds similar to the clunking noise made when the brakes are applied or released on the a320, but has a unique hissing/swishing sound, similar to fluid moving through a hose, that can be heard immediately before the thump. I've flown on the a340 as well, but have never heard it on that aircraft- only the 330.

you can hear it very clearly in this video https://www.youtube.com/watch?v=-vhLxEkArtE. The best example is at 10:47, but it also happens at 4:39 and 11:32.

Any thoughts?

Yes, I've been on many A330s before, but recently, I was on a brand new CZ A333, and I heard the noise for the first time, I thought it was maybe fuel or brake fluid or something. I find it strange because most of the time I sit in a position over the wing on an A330, but I've only actually heard it once.
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767333ER
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Re: a330 swishing/hissing noise during taxi

Wed May 02, 2018 3:23 pm

It’s the brakes being applied and it is followed by another thump when they are released much like when an A320 thumps when brakes are applied and thumps twice when they are released. I’d say the noise comes from the hydraulic system. The 767 makes a very similar noise when it’s brakes are released.
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Balerit
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Re: a330 swishing/hissing noise during taxi

Wed May 02, 2018 4:34 pm

The A300 had brake release actuators on the back of the landing gears which assisted in ensuring that the brakes were releasing, not sure if the modern A330's have them. This could explain the sound of fluid moving in the lines.
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gtae07
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Re: a330 swishing/hissing noise during taxi

Thu May 03, 2018 12:18 am

767333ER wrote:
It’s the brakes being applied and it is followed by another thump when they are released much like when an A320 thumps when brakes are applied and thumps twice when they are released. I’d say the noise comes from the hydraulic system. The 767 makes a very similar noise when it’s brakes are released.

I know of some business jets that do it too. It's most likely the shuttle valves (so yes, a hydraulic component).
 
Apprentice
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Re: a330 swishing/hissing noise during taxi

Tue May 15, 2018 9:39 am

Hi: Out of memory, No schematics with me. Some Airbus models have only two hydraulic system powered by Engine Hydraulic Pumps, that will provide pressure as soon as engine rpm are good. Or by specially dedicated electrically pumps, added for ground operations and or emergency (for instance, one engine out)
But, for the third hydraulic system (ussually the center one), they use Non-Reversing-Hydraulic -Pump. This devices, using high pressure hydraulic from a pressurized system, make turn an “hydraulic motor”, linked to an hydraulic pump that pressurize the remaining hyd system.
This pumps are noise and You will feel more on ground, during taxi when system is used for brake and steering, and initial t.o., during landing gear retractions. This pump (remember, out of memory, please be kind) is located between LH and RH Main Wheel Well, near aircraft centerline and fixed to a/c structure, so it’s noise is amplified by it.

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masi1157
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Re: a330 swishing/hissing noise during taxi

Tue May 15, 2018 1:18 pm

Apprentice wrote:
This devices, using high pressure hydraulic from a pressurized system, make turn an “hydraulic motor”, linked to an hydraulic pump that pressurize the remaining hyd system.

That sounds like you are talking about a PTU, which doesn't exist on other Airbus models than A320 family. So it can't be the reason on the A330 discussed here.


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KanaHawaii
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Re: a330 swishing/hissing noise during taxi

Tue May 15, 2018 8:47 pm

I wonder if this is the same sound that one hears when flying on Delta 757-300's when landing. Right after it slows down there is this whooshing sound like an air movement. I don't hear it on UA 757-300's but then again they might have been designed with different pump orientation based on customer (CO) designations when ordering the craft.
 
Apprentice
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Re: a330 swishing/hissing noise during taxi

Wed May 16, 2018 6:41 am

That sounds like you are talking about a PTU, which doesn't exist on other Airbus models than A320 family. So it can't be the reason on the A330 discussed here.


Gruß, masi1157[/quote]

From a “2 ‘Engine Dc-10 Schematic.......”

https://www.google.com/imgres?imgurl=ht ... mrc&uact=8
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masi1157
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Re: a330 swishing/hissing noise during taxi

Wed May 16, 2018 7:02 am

Apprentice wrote:
From a “2 ‘Engine Dc-10 Schematic.......”

As I said: That is the hydraulics architecture of the A320 family. The one of A330 is different and has no PTU.


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Apprentice
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Re: a330 swishing/hissing noise during taxi

Wed May 16, 2018 3:20 pm

Hi:
PTU, If a Boeing terminology, it is?
On Airbus System Manual they are called Electric Pumps.

(By the way, previously posted schematic, from Airbus website, had nothing to do with a 2 Engine,s Dc-10)

Rgds
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Apprentice
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Re: a330 swishing/hissing noise during taxi

Wed May 16, 2018 3:34 pm

Hi:
And “Green”, “Blue” “Yellow” denominations, when refered to hydraulic systems, are used nowadays by Airbus. Boeing uses Left, Center, Right.
In the old days, Caravelle..... but this is another history.

Rgds
“An AME, with just a Mechanic Role”, as per one of our pilots
"A NO" is a positive answer., "DON'T KNOW" is not. My Tutor (a wise man)
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masi1157
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Re: a330 swishing/hissing noise during taxi

Thu May 17, 2018 12:40 pm

Apprentice wrote:
PTU, If a Boeing terminology, it is?

The PTU is shown in the schematics that you linked, and it means Power Transfer Unit. It is not an electric pump, it is what you explained earlier, a motor in one system driving a pump in the other one and vice versa. It is so famous that I'm afraid you are one of the very very few here in the forum who doesn't know it. Simply do a search for "barking dog", you will find hundreds of posts.

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