QANTAS747-438
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A320/A319 "barking" After Shutdown

Thu Jul 15, 2004 3:33 pm

I was at United today at LAX, and I noticed that an odd event occurs only at United with the A320s and A319s. This sound never happens at NW, US, or AW. The aircraft pulls up to the gate with one engine running prior to installing the power umbilical. The power is connected and the #1 engine is finally shutdown. As it does, it makes a "barking" sound, as if a large dog were in the cargo hold. It does it in pairs: woof-woof......woof-woof.....woof-woof.... The sound gets lower and lower as the engine spools down. Even as the engine is finishing spooling down, the sound finally gives up in a dreadful "woof-woof... woooooof-wooooooooooof" The pace of the sound isn't fast, but exactly resembles a large dog. Also, it doesn't sound like it's coming from the engine, nor does it sound like an engine noise. It sounds like it is coming from the belly. Any ideas?
My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
 
MYT332
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RE: A320/A319 "barking" After Shutdown

Thu Jul 15, 2004 8:08 pm

Any ideas?
You should go see someone  Big grin

Man, according to this forum, we've got Dash 8's and the like farting and A320's barking.  Laugh out loud

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NKP S2
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RE: A320/A319 "barking" After Shutdown

Thu Jul 15, 2004 8:58 pm

Any ideas?

Hydraulic PTU. Do a tech/ops forum search though...............
 
UbiDenmark
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RE: A320/A319 "barking" After Shutdown

Thu Jul 15, 2004 9:34 pm

I can't offer an explanation but I hear the same thing regularly on A320s.

Might it be the mechanism which operates the hold doors ?

 
michi
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RE: A320/A319 "barking" After Shutdown

Thu Jul 15, 2004 9:40 pm

Hi there,

it is the HYD PTU (Hydraulic Power Transfer Unit). It comes on automatically when the differential pressure between the green and the yellow system is greater than 500 PSI (normal system pressure is 3000 PSI). This normally happens, when you start or shut down an engine. The PTU is working only for a few seconds or even less than that, because it stops when the pressure in the associated system is at 3000PSI again (that's the "barking" sound). And there are not to many hydraulic functions needed while shutting down an engine. So the pressure is maintained easily.

There are a few more parameters that affect PTU automatic operation. But that would lead us to far off topic.

Greeting Michael
 
Klaus
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RE: A320/A319 "barking" After Shutdown

Thu Jul 15, 2004 9:40 pm

Search function... many, many theads about it already...

(The PTU transfers hydraulic power between the separate hydraulic systems, especially when only one engine is running.)
 
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longhauler
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RE: A320/A319 "barking" After Shutdown

Sat Jul 17, 2004 6:25 am

From above:

You should go see someone

Man, according to this forum, we've got Dash 8's and the like farting and A320's barking.


This is quite funny! Big grin
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
delta-flyer
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RE: A320/A319 "barking" After Shutdown

Sun Jul 18, 2004 2:17 am

The PTU is indeed the correct answer.

I will shed a bit more light on why the pitch changes as the engine spools down.

As Michi stated above, the PTU comes on when the pressure in the other system drops. The PTU runs just long enough to repressurize the system ... a second or two, then stops. During the next few seconds, the system depressurizes slowly due to "internal leakage" in the hydraulic system. When the difference in pressure agan reaches 500 psi, the PTU cycles.

As the engine spools down, the flow from the engine driven pump available to drive the PTU is reduced, therefore the PTU speed and power transfer to the second system is also reduced. Thus, it runs slower, and takes a bit longer to repressurize the second system - this explains the lower pitch. When the engine stops, the PTU no longer receives flow from the engine pump, so it, too, "dies".

I would be glad to answer any questions on the PTU or other hydraulic components. I worked on the Vickers PTU which is used on some of the A320 series.

Pete
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NoUFO
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RE: A320/A319 "barking" After Shutdown

Sun Jul 18, 2004 6:51 am

I thought Airbus eventually replaced the "barking" PTU with another one ( that is comparatively slow but doesn't make funny noises?
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delta-flyer
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RE: A320/A319 "barking" After Shutdown

Sun Jul 18, 2004 12:45 pm

Well, that's ours! We are on most 321's and 319's. Not sure exactly which. I'll ask my colleaugues Monday.

Our PTU uses a different control scheme that results in slower accelerations; also, we have impellers on the pumps to prevent cavitation which also results in noise and high acceleration.

Pete
"In God we trust, everyone else bring data"
 
AMERICAN757
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RE: A320/A319 "barking" After Shutdown

Fri Jul 23, 2004 8:59 am

Our United A319 we were on last week was making a sound like that. It was during taxi to the runway though, and it was loud inside the plane, it kept doing it until we started take off roll
 
Boeing4ever
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RE: A320/A319 "barking" After Shutdown

Fri Jul 23, 2004 2:12 pm

Why is it that nearly every other thread on this forum is always about another strange noise coming specifically from the A32X series? Are those aircraft possessed or something? Hell, I'd be worried to if the cockpit instruments suddenly started speaking in tongues!  Laugh out loud

Seriously though, is it all just coincidental?

B4e-Forever New Frontiers
 
yokohama1970
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RE: A320/A319 "barking" After Shutdown

Thu Jul 29, 2004 7:43 pm

American757

quite common. our A319/320's usually taxi-out on engine 2. during taxi-out, they start, turn & ignite the engine 1. here @ AWA, our pilots usually turn engine 2, during pushback & engine 1 during taxi-out.

as posted above, the PTU is hydraulically controlled & required to enable engine starts. next time you are boarding any A319/320, you will also hear the outward-opening, hydraulically controlled cargo doors closing or opening after arrival @ the gate.

the A319/A320 with the IAE V2500 series engines have a very dramatic & distinct sound when starting! Once the engine igniters have been turned off, the engines have a very high-pitched whine, but yet quiet. the idle also audibly increases.

in the US: AWA, jetBlue & United use the IAE V2500 series engines. all the other carriers use the CFM-56-5 series engines.

however, the composite airframe produces that unique high to low pitched "Dolby" effect, during approach. i figured that out here in PHX, by observing all the various A318/319/320 & 321's for carriers on ILS Arrival for Runway 8. my apartment is 5 miles north of PHX & 2 miles south of the final approach pattern. so, the planes are usually @ 6000ft.

Same thing in PIT, my folk's house is on ILS Arrival for Runway 32. they are about 10 miles out. all the US A319/320/321's & UA 319/320's have the same high to low pitch as they pass overhead. i like to show off for my parents! when we are sitting on the deck outside & I announce "airbus", without even looking up.


tom
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Klaus
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Yokohama1970

Thu Jul 29, 2004 7:51 pm

Yokohama1970: however, the composite airframe produces that unique high to low pitched "Dolby" effect, during approach.

The A380 is the first Airbus with at least partial use of composites (GLARE) on the actual fuselage structure, as far as I know. All other Airbus models have aluminium fuselages with only a few external components being composite (fairings, stabilizer, ...)

So I´m rather certain that differences in sound would rather be due to different choice of engines / nacelle structures and different wing and flap design.
 
HorizonGirl
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RE: A320/A319 "barking" After Shutdown

Wed Mar 30, 2005 3:48 pm

Quoting QANTAS747-438 (Thread starter):
"barking" sound, as if a large dog were in the cargo hold. It does it in pairs: woof-woof......woof-woof.....woof-woof.... The sound gets lower and lower as the engine spools down. Even as the engine is finishing spooling down, the sound finally gives up in a dreadful "woof-woof... woooooof-wooooooooooof"

I too observed this pattern on an air Canada flight.
Maybe it always woofs in threes?
During taxiing, it did the opposite as you described.
It started with a "Wooooo-ooooof-Wooooooooo-oooooof."
It then got lower and started in with the "Woof-woof......woof's."
When we parked, it the PTU made a stange "RHOAIYUUUUA."
and continued woofing in threes.
Dose anyone know why?
Flying high on the Wings of the Great Northwest!
 
skywatch
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RE: A320/A319 "barking" After Shutdown

Wed Mar 30, 2005 11:13 pm

Quoting Yokohama1970 (Reply 12):
AWA, jetBlue & United use the IAE V2500 series engines. all the other carriers use the CFM-56-5 series engines.

I am not around Airbuses a whole lot, so I am curious: Do A319's equipped with IAE engines sound better than the CFM's? I hear Fronties's A319, and it sounds high-pitched and whiny. I was wondering if the IAE engines roar. Please note that this is about engines, not Airbus!
------Forever Watchin' The Sky------
 
SlamClick
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RE: A320/A319 "barking" After Shutdown

Thu Mar 31, 2005 12:45 am

Quoting HorizonGirl (Reply 14):
When we parked, it the PTU made a stange "RHOAIYUUUUA."

You are the first person on here who could spell that sound correctly. Are you sure you haven't been to Airbus school?
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
skywatch
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RE: A320/A319 "barking" After Shutdown

Thu Mar 31, 2005 1:28 pm

Quoting HorizonGirl (Reply 14):
When we parked, it the PTU made a stange "RHOAIYUUUUA."

Does anyone have a sound recording for that? Now I'm really curious! I myself have never heard that sound, but it sounds VERY interesting!
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BWI757
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RE: A320/A319 "barking" After Shutdown

Fri Apr 01, 2005 7:54 am

Oh great! Anyone for a sounds database in addition to the tech/ops request for a technical photo database? I could see this being useful... Smile

BWI757
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wjv04
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RE: A320/A319 "barking" After Shutdown

Fri Apr 01, 2005 6:04 pm

No this guy isnt crazy, I too have heard it several times when I worked NWA's a319s and 320s. I just assumed it was a dog in the pit.
 
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HAWK21M
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RE: A320/A319 "barking" After Shutdown

Sun Apr 03, 2005 7:54 pm

Quoting Bwi757 (Reply 18):
Oh great! Anyone for a sounds database in addition to the tech/ops request for a technical photo database? I could see this being useful

Excellent topic.Suggest it in the "site related" forum.
regds
MEL
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HorizonGirl
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RE: A320/A319 "barking" After Shutdown

Mon Apr 04, 2005 11:32 am

Quoting Skywatch (Reply 17):
Does anyone have a sound recording for that?

Read my profile?
Do you know what I'm trying to do?
It is so hard. Sometimes I don't get even any results!
I have even tried recording it myself during a taxi, but was
asked to put it away. Sad
On my return flight, I managed to hide it, but it came out
with just a strange buzz that sounded nothing like it. Darn.
Anyone have proper recording equipment? Big grin
thanks.

Devon
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HorizonGirl
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RE: A320/A319 "barking" After Shutdown

Mon Apr 04, 2005 12:15 pm

Quoting SlamClick (Reply 16):
You are the first person on here who could spell that sound correctly. Are you sure you haven't been to Airbus school?

Lol, no I haven't. Maybe there should put that word in the textbooks?
But I still don't know exactly why it barks.
I started a thread on it. As you probably know, it didn't
go to well. blush  So I'll ask here where there are more
people. I am sorry if I might be breaking a rule.

Devon
Flying high on the Wings of the Great Northwest!
 
AirWillie6475
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RE: A320/A319 "barking" After Shutdown

Wed Apr 06, 2005 3:01 pm

If you are scared of unusual aircraft sounds don't fly the airbus a320. Other than that I love the a320. Thank god it only makes strange sounds on the ground.
 
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HAWK21M
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RE: A320/A319 "barking" After Shutdown

Wed Apr 06, 2005 8:28 pm

Quoting AirWillie6475 (Reply 23):
If you are scared of unusual aircraft sounds don't fly the airbus a320. Other than that I love the a320. Thank god it only makes strange sounds on the ground.

Why only on ground,or is it that its not heard in air because its noisy  Smile
regds
MEL
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jetfixer
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RE: A320/A319 "barking" After Shutdown

Fri Apr 08, 2005 11:50 am

Quoting HAWK21M (Reply 24):
Why only on ground,or is it that its not heard in air because its noisy
regds
MEL

PTU does a self test on engine startup, the PTU will be heard in the air if an engine is shut down. Another commonly heard noise on the ground is a clunking noise when the brakes are pressed and released.
 
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HAWK21M
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RE: A320/A319 "barking" After Shutdown

Sat Apr 09, 2005 5:18 pm

Quoting Jetfixer (Reply 25):
PTU does a self test on engine startup

Interesting.
Can the PTU be driven on grd on choice.Whats the basic sequence.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
cactusTECH
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RE: A320/A319 "barking" After Shutdown

Tue Apr 12, 2005 10:07 pm

PTU operates when either Green or Yellow system is not operating. The PTU pressurizes the opposite system since green system controls normal braking and yellow controls alternate braking. When the crew or technicians shutdown an engine while other engine running, the PTU will automatically come online. This can also be done on the ground with both engines off by turning ON the Yellow ELECTRIC pump.
 
SlamClick
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RE: A320/A319 "barking" After Shutdown

Tue Apr 12, 2005 11:42 pm

Quoting HAWK21M (Reply 24):
Why only on ground,or is it that its not heard in air because its noisy
regds

As stated above, it operates when there is a difference in pressure between the yellow and green hydraulic systems. In the air, with both engines running, there should not be such a difference.

I had an engine failure last year and could not restart. We flew another ten to fifteen minutes before landing. Only one passenger knew anything was wrong, because he asked a flight attendant about the PTU running during the last few minutes of the flight. He was not a non-rev, so we just assumed that he was better informed about Airbus than most of the pax. Maybe he was an a-DOT-netter.
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MD11Engineer
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RE: A320/A319 "barking" After Shutdown

Wed Apr 13, 2005 3:52 am

Just to give the people her an idea what a PTU (Power Transfer Unit) is:

A hydraulic varialbe displacement multipiston pump can also act as a hydraulic motor and drive the input shaft if pressure is applied to it. So if you drive the shaft, it will move hydraulic fluid as a pump, but if there is hydraulic pressure availble on the pipes, it will in turn turn the shaft like a motor.

Now you´ve got two independent hydraulic systems, you want to be able to pressurise one system by using hydraulic power from the other one, but you don´t want to mix the fluids or have them interconnected (e.g. as a fail safe in case one system has a bad leak, so that you won´t loose the hydraulic fluid of the other system as well), so you install two of these pump/ motors and connect their shafts. If there is a pressure difference between the two systems, one side will act as a motor and the other side as the pump (imagine it with a generator and an electrical motor connected to the same shaft).

So, this is the last post I will write about the topic "Airbus barking), next time please use the search function.

Jan
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Bridogger6
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RE: A320/A319 "barking" After Shutdown

Fri Apr 22, 2005 1:08 am

Just for the record, it DOES happen not just on UNited, but all A-319/320 aircraft. It happens while taxiing at the beginning of trip too.. very annoying, lol.
 
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wjv04
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RE: A320/A319 "barking" After Shutdown

Mon Apr 25, 2005 3:34 pm

I found a video that captures the exact barking soundI heard when I used to work the NWA airbus's here in YYC. Listen carefully at about 1min 09 secs.

Airbus Barking Sound
 
jamesbuk
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RE: A320/A319 "barking" After Shutdown

Mon May 09, 2005 5:09 am

i heard it on the video and its more of a wuuf woof ruff woof wuuf woof ruff and then its over maybe its the change in fuel loads into the engine which causes a quick vacuum in the engine which is the extinguished with the hundreds of gallons coming through the blades
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N1120A
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RE: A320/A319 "barking" After Shutdown

Mon May 09, 2005 5:45 am

Quoting NoUFO (Reply 8):
I thought Airbus eventually replaced the "barking" PTU with another one ( that is comparatively slow but doesn't make funny noises?

Even very new ones I have flown with US (brand new A321 in 2001) still made the barking sound. Scares the hell out of some people
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KC135R
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RE: A320/A319 "barking" After Shutdown

Mon May 09, 2005 6:28 am

Quoting MD11Engineer (Reply 29):
Just to give the people her an idea what a PTU (Power Transfer Unit) is:

Wow, thanks for the info. As a hydro maintainer on a decidedly older airplane, that's quite fascinating new (at least to me) technology.
 
MIAspotter
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RE: A320/A319 "barking" After Shutdown

Wed May 11, 2005 4:14 am

Is that PTU thing the one that makes also the funny noise when the #1 engine is started? I have flown a lot in the A320 family but a couple of weeks ago I was on an Easyjet A319 from LGW to TLS and when they switched on the #1 engine that "barking" noise came in.... pretty loud, you should have seen the faces on some of the pax! also when we landed as soon as we touched down... WOOF WOOF WOOF WOOF WOOF! I thought it was the autobrakes kicking in because we didn't use any reverse thrust.

MIAspotter
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MIAspotter
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RE: A320/A319 "barking" After Shutdown

Wed May 11, 2005 4:18 am

Quoting Wjv04 (Reply 31):
I found a video that captures the exact barking soundI heard when I used to work the NWA airbus's here in YYC. Listen carefully at about 1min 09 secs.

Hmm I think the noise you hear on that video is just the gear retracting...
WOO WOO WOO WOO WOO WOO... CLUNK! Big grin hey I'm good at making funy noises!

MIAspotter
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milan320
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RE: A320/A319 "barking" After Shutdown

Thu May 12, 2005 6:03 am

Quoting American757 (Reply 10):
Our United A319 we were on last week was making a sound like that. It was during taxi to the runway though, and it was loud inside the plane, it kept doing it until we started take off roll

You were most likely taxiing on one engine. Some pilots do that, and the PTU will continue to be active during the taxiing then.
I don't know what United's SOP is but I've noticed this usually happens if the pilots are in a hurry (i.e. busy airport, don't want to miss your queue. I seem to remember this always happened when I'd be flying out of either ORD or SFO).
/milan320
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AsstChiefMark
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RE: A320/A319 "barking" After Shutdown

Thu May 12, 2005 7:07 am

You'd think they'd do something to fix that sound. It scared my parents on a trip to LAS about two years ago. My nephew mentioned it after his Airbus flight from MSP to PDX last Christmas. He was so scared that he started heading toward the exit. The flight attendant told him to sit down; she wouldn't explain it to him when he asked. He said she used a tone of voice that implied, "You dumb sh*t. Just sit down and shut up."

At least the crew could mention over the PA system soon after boarding that it was a normal sound.

The banging that's heard during an MRI (magnetic resonance imaging) is normal and the X-ray techs have the decency to explain it beforehand.

Mark
Red tail...Red tail...Red tail...Red tail...Red tail...Red tail...Red tail...Red tail...Damned MSP...Red tail...Red tail
 
bohica
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RE: A320/A319 "barking" After Shutdown

Thu May 12, 2005 1:07 pm

Quoting Yokohama1970 (Reply 12):
in the US: AWA, jetBlue & United use the IAE V2500 series engines. all the other carriers use the CFM-56-5 series engines.

Independence Air A319's have the V2500 series engines. I was on a FLYI airbus the other day and the hydraulic system started barking after the first engine was started. However I did not hear it bark after engine shutdown.

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