bahadir
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Grinding Noise On A320 Family Aircraft

Tue Jun 24, 2003 8:20 pm

I am sure that this was asked before but there are these 6-10 short grinding noises that comes after the engines are turned off after the arrival and before engine start-up on departure.

It becomes more pronounced if you are sitting on top of the wing area..

Could anyone with A320 experience care to comment what these short sounds are?

Thanks..
Earthbound misfit I
 
gotAirbus
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RE: Grinding Noise On A320 Family Aircraft

Tue Jun 24, 2003 10:26 pm

If you want to know, this was discussed before...

When using the search utility, search for "grinding".

(gotAirbus?)
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fspilot747
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RE: Grinding Noise On A320 Family Aircraft

Wed Jun 25, 2003 1:08 am

Sounds like the baggage doors closing. It would be around that time, and it does sound like a "grinding.."



Cheers,
FSP
 
cricri
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RE: Grinding Noise On A320 Family Aircraft

Wed Jun 25, 2003 1:24 am

Flaps deploying and retracting maybe?
 
NKP S2
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RE: Grinding Noise On A320 Family Aircraft

Wed Jun 25, 2003 2:05 am

Let's make this like a treasure hunt...  Smile

So far, the most correct response was the poster who suggested a search.

Get cracking!

 
sushka
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RE: Grinding Noise On A320 Family Aircraft

Wed Jun 25, 2003 2:07 am

I heard this same noise during my flight on an A320 a couple months ago. At first I thought it was the baggage door too, but it lasted the entire flight. Very strange.
Pershoyu Spravoyu Litaki!
 
A/c train
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NKP S2

Wed Jun 25, 2003 3:05 pm

is correct,  Wink/being sarcastic

Its the yellow system Hydraulic pump. Elec, to operate the cargo doors and the PTU does an Auto function BITE on pushback, the short high pitch winding sounds are PTU's and Hyd pumps. But for a more accurate answer, do a search as NKP S2 suggested.
regards a/c
 
A320-Tech
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RE: Grinding Noise On A320 Family Aircraft

Wed Jun 25, 2003 6:19 pm

That cyclical "grinding" noise as you call it sounds like the PTU, which can be heard when you are sitting over the wing area immediately after engine shut down and just after engine start.

What is happening is that this PTU (Power Transfer Unit) is acting as a hydraulic pump for the opposite side hydraulic system. This PTU is driven hydraulically and powers the Green or Yellow Hydraulic system. This PTU is being driven hydraulically (by the Green or Yellow system) and is 'automatically' activated when one hydraulic system pressure dips below a specific value. This is the reason why you hear this 'noise' at engine shut down. The reason why this noise is cyclical is due to the fact that when it reaches the desired pressure (3000 psi) it automatically shuts off, and when the pressure dips down again the PTU kicks back in.

The constant 'whine' you hear when the cargo doors are being opened or closed is in fact the Yellow Hydraulic Electric pump.

Hope this answers your question.


Regards,
A320Tech
 
bahadir
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RE: Grinding Noise On A320 Family Aircraft

Fri Jun 27, 2003 6:52 am

Thanks for all the replies.

I wasn't talking about the constant whining, which is the cargo doors. But this noise raises a lot of pax comments before the push back or after the engine shut down. Couple of times I was asked by whomever I was traveling with , and I didn't know the answer.

People look at you funny when you tell them you are a CFI and you don't know the answer to a question about an aircraft system.  Smile

But something is not clear to me.. Is this basically due to the activation and de-activation of the hydrolic systems? Because I don't see why you would need them on the ground.
Earthbound misfit I
 
Continental
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RE: Grinding Noise On A320 Family Aircraft

Fri Jun 27, 2003 10:21 am

YES! I heard that on Saturday flying MSP-MDW. We arrived at the gate, fuel flow was cut, and then it sounded like someone was sawing something off. It lasted a while, but then it disappeared! Interesting!

co
 
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canadianpylon
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RE: Grinding Noise On A320 Family Aircraft

Tue Jul 01, 2003 5:22 am

Thanks for all the replies.

I wasn't talking about the constant whining, which is the cargo doors. But this noise raises a lot of pax comments before the push back or after the engine shut down. Couple of times I was asked by whomever I was traveling with , and I didn't know the answer.


Just tell 'em that it's the automated wing tightening system, that screws the wings into the belly.  Smile/happy/getting dizzy Tell 'em it's a good thing, cause 'You don't want the wings to fall off the airplane while flying, now do you?'  Laugh out loud

CanadianPylon
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BR715-A1-30
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RE: Grinding Noise On A320 Family Aircraft

Tue Jul 01, 2003 12:08 pm

is correct,

Its the yellow system Hydraulic pump. Elec, to operate the cargo doors and the PTU does an Auto function BITE on pushback, the short high pitch winding sounds are PTU's and Hyd pumps. But for a more accurate answer, do a search as NKP S2 suggested.
regards a/c


The 717 does this too. It does it right before pushback and engine start. It will make a long grinding sound, and then 7-8 short intervals before engine #1 starts.
Puhdiddle
 
clrd2go
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RE: Grinding Noise On A320 Family Aircraft

Wed Jul 02, 2003 3:55 am


I'm glad someone posted this question..we were on an A321 and A320 this
past week and when we heard the noise, my wife inquired as to what it
was..I recalled it being discussed in here a while back..but..couldn't recall
the answer. (I told my wife it was baggage doors/conveyors in the cargo
area)


Jim
What a long strange trip it's been
 
sushka
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RE: Grinding Noise On A320 Family Aircraft

Wed Jul 02, 2003 6:51 am

When I heard it it was lasting the entire flight. It must have been from a different source but I still don't know what it was.
btw. it was an America West A320
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USAIRWAYS321
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RE: Grinding Noise On A320 Family Aircraft

Wed Jul 02, 2003 3:41 pm

The 'whirr' that lasts the entire flight is just a quality of the CFM engines on the A320 family aircraft...I love that sound!

 Smile/happy/getting dizzy Smile/happy/getting dizzy Smile/happy/getting dizzyUSAIRWAYS321 Smile/happy/getting dizzy Smile/happy/getting dizzy Smile/happy/getting dizzy
 
sushka
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RE: Grinding Noise On A320 Family Aircraft

Wed Jul 02, 2003 10:36 pm

It actulay was a grinding noise that I could feel under neath us. Pretty strange. Both my mom and I were wondering about it. Anybody else had this?
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NKP S2
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RE: Grinding Noise On A320 Family Aircraft

Thu Jul 03, 2003 1:19 am

----"It actulay was a grinding noise that I could feel under neath us. Pretty strange. Both my mom and I were wondering about it. Anybody else had this?"---

That's because the PTU ( the source of the intermittent "grinding"...most hear it as a sort of muffled "barking dog" sound ) is located under the floor....in the aft part of the MLG w/w. Anybody in a 10-12 row "radius" of that point will be able to hear it.
 
A320-Tech
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RE: Grinding Noise On A320 Family Aircraft

Fri Jul 04, 2003 1:19 pm

The PTU is a 'back up' and is not supposed to run constantly throughout the flight unless one of the hyrdaulic pumps went T.U. or was not able to keep up pressure on one side.
 
Arrow
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RE: Grinding Noise On A320 Family Aircraft

Sat Jul 05, 2003 6:19 am

The 'whirr' that lasts the entire flight is just a quality of the CFM engines on the A320 family aircraft...I love that sound!

I hate that sound. It's worst in the front rows 1-5, and last week on a flight to Toronto on an AC 320 my wife asked me if we were on a prop-plane! I don't recall the North Star's Merlins being a whole lot louder.
Never let the facts get in the way of a good story.
 
delta-flyer
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RE: Grinding Noise On A320 Family Aircraft

Sat Jul 05, 2003 6:26 am

A320-Tech .... your answers are 100% correct. I helped design one of the PTU's (there are 2 suppliers) and we were able to make ours not start/stop so violently, in fact, ours ran relatively continuously while just making up internal leakage flow. But the customer wanted it to cycle, so they can get an idea of the hydraulic system's internal leakage by counting the frequency of the cycles.

Well, customer is always right!!!

Pete
"In God we trust, everyone else bring data"

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