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Grinding Noise On A320 Family Aircraft  
User currently offlineBahadir From United States of America, joined Oct 2001, 1772 posts, RR: 10
Posted (11 years 1 month 1 week 3 days 6 hours ago) and read 9423 times:

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
19 replies: All unread, jump to last
 
User currently offlineGotAirbus From Singapore, joined May 2001, 851 posts, RR: 1
Reply 1, posted (11 years 1 month 1 week 3 days 4 hours ago) and read 9352 times:

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

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

(gotAirbus?)



(gotAIRBUS?) - (Got Commonality?) - (Have A Nice Flight!)
User currently offlineFSPilot747 From United States of America, joined Oct 1999, 3599 posts, RR: 12
Reply 2, posted (11 years 1 month 1 week 3 days 1 hour ago) and read 9270 times:

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



Cheers,
FSP


User currently offlineCricri From France, joined Oct 1999, 581 posts, RR: 7
Reply 3, posted (11 years 1 month 1 week 3 days 1 hour ago) and read 9266 times:

Flaps deploying and retracting maybe?

User currently offlineNKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 5
Reply 4, posted (11 years 1 month 1 week 3 days ago) and read 9246 times:

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

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

Get cracking!



User currently offlineSushka From United States of America, joined Nov 1999, 4784 posts, RR: 14
Reply 5, posted (11 years 1 month 1 week 3 days ago) and read 9245 times:

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!
User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 6, posted (11 years 1 month 1 week 2 days 11 hours ago) and read 9148 times:

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


User currently offlineA320-Tech From United States of America, joined Jan 2002, 38 posts, RR: 2
Reply 7, posted (11 years 1 month 1 week 2 days 8 hours ago) and read 9128 times:

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


User currently offlineBahadir From United States of America, joined Oct 2001, 1772 posts, RR: 10
Reply 8, posted (11 years 1 month 1 week 19 hours ago) and read 8973 times:

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
User currently offlineContinental From United States of America, joined Jun 2000, 5511 posts, RR: 18
Reply 9, posted (11 years 1 month 1 week 16 hours ago) and read 8961 times:

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


User currently offlineCanadianPylon From Canada, joined May 2003, 307 posts, RR: 0
Reply 10, posted (11 years 1 month 3 days 21 hours ago) and read 8850 times:

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
"Get it? Got it? Good...."



Always looking for the longest route with the most transfers.
User currently offlineBR715-A1-30 From , joined Dec 1969, posts, RR:
Reply 11, posted (11 years 1 month 3 days 14 hours ago) and read 8812 times:

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.


User currently offlineClrd2go From United States of America, joined Feb 2003, 1000 posts, RR: 0
Reply 12, posted (11 years 1 month 2 days 22 hours ago) and read 8762 times:


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
User currently offlineSushka From United States of America, joined Nov 1999, 4784 posts, RR: 14
Reply 13, posted (11 years 1 month 2 days 19 hours ago) and read 8737 times:

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



Pershoyu Spravoyu Litaki!
User currently offlineUSAIRWAYS321 From United States of America, joined Jul 2001, 1845 posts, RR: 9
Reply 14, posted (11 years 1 month 2 days 10 hours ago) and read 8720 times:

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


User currently offlineSushka From United States of America, joined Nov 1999, 4784 posts, RR: 14
Reply 15, posted (11 years 1 month 2 days 3 hours ago) and read 8707 times:

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?


Pershoyu Spravoyu Litaki!
User currently offlineNKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 5
Reply 16, posted (11 years 1 month 2 days 1 hour ago) and read 8698 times:

----"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.


User currently offlineA320-Tech From United States of America, joined Jan 2002, 38 posts, RR: 2
Reply 17, posted (11 years 1 month 13 hours ago) and read 8618 times:

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.

User currently offlineArrow From Canada, joined Jun 2002, 2676 posts, RR: 2
Reply 18, posted (11 years 4 weeks 1 day 20 hours ago) and read 8574 times:
Support Airliners.net - become a First Class Member!

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.
User currently offlineDelta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 7
Reply 19, posted (11 years 4 weeks 1 day 20 hours ago) and read 8590 times:

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


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