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HAWK21M
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A320 Neo sound

Tue Dec 08, 2020 7:43 pm

The A320 Neo has a 1-2sec Grinding sound on Landing presuming on deploying the Thrust Reversers.
What exactly is causing that sound.
Sounds like Steel brakes getting applied on taxying Aircraft, only this is on Touchdown.
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AA737-823
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Re: A320 Neo sound

Wed Dec 09, 2020 6:28 am

Can you post a link to a video, so we can all hear it?
Also, are you certain that it happens on both LEAP and PW-GTF engines?
Because those Pratts make a whole new library of weird noises, from startup to shut down!
 
flybaurlax
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Re: A320 Neo sound

Wed Dec 09, 2020 5:23 pm

I'm going to venture you're talking about the GTF. You can hear the grinding/growling noise at lower power settings. In Seattle, I can hear it and know instantly it's a DL A220 joining the LOC with the engines spooling from idle.

I'm curious what it is, too. Perhaps it's the gearbox?
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434395
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Re: A320 Neo sound

Tue May 11, 2021 12:05 am

I'm curious what it is, too. Perhaps it's the gearbox?[/quote]

I believe you're referring to the howl from the PW1000 engines on some 320neo's and CSeries. These engines have what PW call a TALON combustor, I forget what it stands for but I'm sure it burns the fuel cleaner. The howl of these engines is created by the pressure changes in the combustion chamber when the engine is throttled up from idle. The PW4000 and 800 also make similar howling noises when spooling up and they all feature Pratt and Whitney's TALON combustors. Hope that helps.
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masi1157
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Re: A320 Neo sound

Thu May 13, 2021 10:58 am

speedbird717 wrote:
The howl of these engines is created by the pressure changes in the combustion chamber...

I would call those "pressure changes" a resonance within the combustion chamber. It can destroy the engine if it gets too strong. Fortunately it is not that strong and appears only in trasient phases in PW1000 engines.


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517 different segments on 101 airlines to 212 airports in 55 countries
 
DFW17L
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Re: A320 Neo sound

Wed May 19, 2021 8:57 pm

Regardless of the cause, it's still creepy.
 
CRJockey
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Re: A320 Neo sound

Thu May 20, 2021 8:19 pm

DFW17L wrote:
Regardless of the cause, it's still creepy.


This is creepy for you? A piece of machinery making a sound is creepy for you? Wow…
 
DFW17L
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Re: A320 Neo sound

Thu May 20, 2021 11:24 pm

CRJockey wrote:
DFW17L wrote:
Regardless of the cause, it's still creepy.


This is creepy for you? A piece of machinery making a sound is creepy for you? Wow…


I know, it sounds like I’m a NIMBY. I’m actually a huge plane enthusiast and I look forward to my first ride on the A220.

The dogs in my neighborhood still bark when the A220 moans overhead. And visitors sometime ask me “What was that?”
 
masi1157
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Re: A320 Neo sound

Fri May 21, 2021 8:02 am

CRJockey wrote:
This is creepy for you? A piece of machinery making a sound is creepy for you? Wow…

When you know what it is and what it could potentially do to the engine, it is in fact a bit creepy. This is not at all a piece of machinery making a normal sound.

Gruß, masi1157
517 different segments on 101 airlines to 212 airports in 55 countries
 
CRJockey
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Re: A320 Neo sound

Sat May 22, 2021 1:31 am

masi1157 wrote:
CRJockey wrote:
This is creepy for you? A piece of machinery making a sound is creepy for you? Wow…

When you know what it is and what it could potentially do to the engine, it is in fact a bit creepy. This is not at all a piece of machinery making a normal sound.

Gruß, masi1157


Now I am curious. Enlighten me.
 
masi1157
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Re: A320 Neo sound

Sat May 22, 2021 6:41 am

Simply read a few more posts than only the very last one. I said it already earlier, hope that was enough to enlighten you.


Gruß, masi1157
517 different segments on 101 airlines to 212 airports in 55 countries
 
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HAWK21M
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Re: A320 Neo sound

Mon May 24, 2021 11:58 am

Yes this occurs on the PW-GTS powerplants.
Heard it almost every time few seconds post touchdown
Cant video record it as photography on airside is restricted out here.
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fr8mech
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Re: A320 Neo sound

Mon May 24, 2021 12:06 pm

masi1157 wrote:
Simply read a few more posts than only the very last one. I said it already earlier, hope that was enough to enlighten you.


Gruß, masi1157


You say these pressure changes are actually some sort of resonance being set up, that can

masi1157 wrote:
destroy the engine if it gets too strong


Can you support/defend that with some sort of documentation?
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lightsaber
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Re: A320 Neo sound

Wed May 26, 2021 3:18 pm

fr8mech wrote:
masi1157 wrote:
Simply read a few more posts than only the very last one. I said it already earlier, hope that was enough to enlighten you.


Gruß, masi1157


You say these pressure changes are actually some sort of resonance being set up, that can

masi1157 wrote:
destroy the engine if it gets too strong


Can you support/defend that with some sort of documentation?

I used to work for Pratt's combustors augmentors and nozzles. This is Rayleigh's criterion where energy (fuel droplets) are added at near the natural frequency of the combustor.

I hypothesize that in the newer lower pressure drop TALON combustors (Technology for advanced low NOx) causes the quench jets to under-penitrate during transitions. So the length that can oscillate grows shifting the frequencies of the combustor's natural frequency. In general, one wants really short combustor lengths as matches with low frequency are more common.
On TALON.
https://prattwhitney.com/products-and-s ... /pw4000-94

I speculate this is hurting combustor durability (shakes off coatings). In my opinion the overall combustor length and the presence of the quench jets makes more dramatic outcomes unlikely.

These oscillations are far harder to control in lean combustors.

The solutions are:
1. Improve pre-diffuser to increase combustor pressure drop (requires a new casing, not retrofitable)
2. Decrease the number if quench holes to increase penitration (larger diameter jets go further). This will increase NOx production (nothing is free).
3. Shorten combustor (this is a new engine design). However, the GTFs have the shortest combustor proven in about 2012. (This is a design decision that must be made early in engine design as it effects everything such as casing, shaft length/dynamics including bearing locations, bearing placement, thrust bearing design and the overall engine optimization due to weight impacts). Everyone else wants short.
4. New fuel injectors (most likely solution) to shift natural frequency caused by fuel injection. This is never done without supporting a major PiP unless direly needed due to high test costs as emission certification is voided.

I expect a large and small PurePower engine PiP with this as part of the package.

Take this all as my opinion.

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masi1157
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Re: A320 Neo sound

Wed May 26, 2021 8:00 pm

lightsaber wrote:
I used to work for Pratt's combustors augmentors and nozzles.

I am not an expert in engines. I used to work in acoustics, but not with P&W. When this sound popped up during development we discussed it several times with P&W engine and acoustics experts. In the beginning it was much worse and we all were very concerned. Today it seems to be quite well controlled. And it occurs only during transient phases. The phenomenon itself is known as "combustor screech, howl and growl". I remember a link, but I can't find it anymore. It had photos of turbines destroyed by that effect.


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517 different segments on 101 airlines to 212 airports in 55 countries

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