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A320/A319 "barking" After Shutdown  
User currently offlineQANTAS747-438 From United States of America, joined Jan 2001, 1922 posts, RR: 1
Posted (10 years 1 week 1 day 19 hours ago) and read 16609 times:

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.
39 replies: All unread, showing first 25:
 
User currently offlineMYT332 From United Kingdom, joined Sep 2003, 9112 posts, RR: 71
Reply 1, posted (10 years 1 week 1 day 14 hours ago) and read 16388 times:

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




One Life, Live it.
User currently offlineNKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 5
Reply 2, posted (10 years 1 week 1 day 13 hours ago) and read 16376 times:

Any ideas?

Hydraulic PTU. Do a tech/ops forum search though...............


User currently offlineUbiDenmark From , joined Dec 1969, posts, RR:
Reply 3, posted (10 years 1 week 1 day 13 hours ago) and read 16360 times:

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 ?



User currently offlineMichi From Germany, joined Jul 2004, 73 posts, RR: 0
Reply 4, posted (10 years 1 week 1 day 13 hours ago) and read 16369 times:

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


User currently offlineKlaus From Germany, joined Jul 2001, 21406 posts, RR: 54
Reply 5, posted (10 years 1 week 1 day 13 hours ago) and read 16353 times:

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.)


User currently offlineLongHauler From Canada, joined Mar 2004, 4906 posts, RR: 43
Reply 6, posted (10 years 1 week 4 hours ago) and read 16149 times:

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



Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
User currently offlineDelta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 7
Reply 7, posted (10 years 6 days 8 hours ago) and read 16058 times:

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


User currently offlineNoUFO From Germany, joined Apr 2001, 7943 posts, RR: 12
Reply 8, posted (10 years 6 days 3 hours ago) and read 16017 times:

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


I support the right to arm bears
User currently offlineDelta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 7
Reply 9, posted (10 years 5 days 21 hours ago) and read 15977 times:

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


User currently offlineAmerican757 From United States of America, joined Mar 2001, 475 posts, RR: 0
Reply 10, posted (10 years 1 day 1 hour ago) and read 15733 times:

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

User currently offlineBoeing4ever From , joined Dec 1969, posts, RR:
Reply 11, posted (10 years 20 hours ago) and read 15695 times:

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


User currently offlineYokohama1970 From United States of America, joined Jul 2004, 199 posts, RR: 2
Reply 12, posted (9 years 11 months 4 weeks 1 day 14 hours ago) and read 15542 times:

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



Thank You Derek! Good Luck with the LA Dodgers
User currently offlineKlaus From Germany, joined Jul 2001, 21406 posts, RR: 54
Reply 13, posted (9 years 11 months 4 weeks 1 day 14 hours ago) and read 15539 times:

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.


User currently offlineHorizonGirl From Canada, joined Mar 2005, 807 posts, RR: 16
Reply 14, posted (9 years 3 months 3 weeks 4 days 18 hours ago) and read 14617 times:

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!
User currently offlineSkywatch From United States of America, joined Mar 2005, 923 posts, RR: 5
Reply 15, posted (9 years 3 months 3 weeks 4 days 11 hours ago) and read 14560 times:

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------
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 16, posted (9 years 3 months 3 weeks 4 days 9 hours ago) and read 14540 times:

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.
User currently offlineSkywatch From United States of America, joined Mar 2005, 923 posts, RR: 5
Reply 17, posted (9 years 3 months 3 weeks 3 days 21 hours ago) and read 14407 times:

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!



------Forever Watchin' The Sky------
User currently offlineBwi757 From Israel, joined Dec 2004, 429 posts, RR: 2
Reply 18, posted (9 years 3 months 3 weeks 3 days 2 hours ago) and read 14328 times:

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



I live in the US but my heart is in Jerusalem!
User currently offlineWJV04 From Canada, joined Jun 2001, 583 posts, RR: 4
Reply 19, posted (9 years 3 months 3 weeks 2 days 16 hours ago) and read 14283 times:

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.

User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 20, posted (9 years 3 months 3 weeks 14 hours ago) and read 14195 times:

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



Think of the brighter side!
User currently offlineHorizonGirl From Canada, joined Mar 2005, 807 posts, RR: 16
Reply 21, posted (9 years 3 months 2 weeks 6 days 23 hours ago) and read 14143 times:

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



Flying high on the Wings of the Great Northwest!
User currently offlineHorizonGirl From Canada, joined Mar 2005, 807 posts, RR: 16
Reply 22, posted (9 years 3 months 2 weeks 6 days 22 hours ago) and read 14140 times:

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!
User currently offlineAirWillie6475 From United States of America, joined Jan 2005, 2448 posts, RR: 1
Reply 23, posted (9 years 3 months 2 weeks 4 days 19 hours ago) and read 14047 times:

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.

User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 24, posted (9 years 3 months 2 weeks 4 days 14 hours ago) and read 14015 times:

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



Think of the brighter side!
25 Jetfixer : 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 c
26 HAWK21M : Interesting. Can the PTU be driven on grd on choice.Whats the basic sequence. regds MEL
27 CactusTECH : PTU operates when either Green or Yellow system is not operating. The PTU pressurizes the opposite system since green system controls normal braking a
28 SlamClick : 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 run
29 MD11Engineer : 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 hydrauli
30 Bridogger6 : 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 annoy
31 Post contains links Wjv04 : 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.
32 Jamesbuk : 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 whic
33 N1120A : 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
34 KC135R : Wow, thanks for the info. As a hydro maintainer on a decidedly older airplane, that's quite fascinating new (at least to me) technology.
35 MIAspotter : 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 a
36 Post contains images MIAspotter : Hmm I think the noise you hear on that video is just the gear retracting... WOO WOO WOO WOO WOO WOO... CLUNK! hey I'm good at making funy noises! MIA
37 Milan320 : 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 Un
38 AsstChiefMark : 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
39 Bohica : 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
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