United737522
Topic Author
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AA 757 Sawing Noise

Tue Oct 25, 2005 12:32 pm

Hey everyone,

On one of my last AA 757 flights, after the first engine was shut down after landing, a sawing noise was very audible throughout the cabin. It went on for a good 5-7 minutes. I have a video of it and you can clearly hear it. If anyone know how I can post the video so you can hear, let me know.

Thanks for your responses!
'Michael Mooronism' ~Jetjack74
 
474218
Posts: 4510
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 12:54 pm

Sounds like the Hydraulic Power Transfer Units. Because one engine is shut down, the hydraulic power from the hydraulic pump on the running engine has to be transferred to the other hydraulic systems.
 
jmc1975
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 2:04 pm

Sounds like the typical sound of a Rolls-Royce engine.
.......
 
dl757md
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 2:07 pm

Quoting 474218 (Reply 1):
Sounds like the Hydraulic Power Transfer Units

It is the Hydraulic PTU however there is only one on a 57. The PTU uses right system hydraulics to pressurize the left system hydraulics without fluid transfer when the left engine shuts down. For further info search 757 PTU in the Tech/Ops forum.

DL757Md
757 Most beautiful airliner in the sky!
 
Glareskin
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 2:56 pm

Are you sure it wasn't an A320?
There's still a long way to go before all the alliances deserve a star...
 
RDUDDJI
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 3:07 pm

Quoting Glareskin (Reply 4):
Are you sure it wasn't an A320?

Yeah, no joke the A320's are loud as heck! I have never noticed said effect on a B757.

Quoting United737522 (Thread starter):
I have a video of it

Tsk, tsk, shouldn't be using electronics during taxi... (ex. cellphones)  Smile
Sometimes we don't realize the good times when we're in them
 
cdfmxtech
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 3:09 pm

AA doesn't operate A320s...so its a sure bet it was a 57!
 
dl757md
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 3:31 pm

Quoting RDUDDJI (Reply 5):
I have never noticed said effect on a B757

Then you haven't been on one when the PTU is running. You can hear it in the cockpit it's so loud. It's very annoying and somewhat unnerving for pax who don't understand what it is or that it's normal. That would be most of them.

DL757Md
757 Most beautiful airliner in the sky!
 
ETStar
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 3:38 pm

Ok I am assuming that this is the same noise as the ZZIIING ZIIIIIIIIIING ZIIIING noise that seems to come out from A320s right after pushback (and other times).

How about that other hissssssssssssssssssssss sound we hear when landing on a 757, right after the thrust reversers are activated and retracted (ok, might be wrong on actual terms, but it is after the thrust reversers). It can go on for many seconds.... hhsssssssssssssssssssss hshssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss

Can't be the breaks, can it? Only hear it on a 75.
 
dl757md
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 3:44 pm

Quoting ETStar (Reply 8):
How about that other hissssssssssssssssssssss sound we hear when landing on a 757, right after the thrust reversers are activated and retracted (ok, might be wrong on actual terms, but it is after the thrust reversers). It can go on for many seconds.... hhsssssssssssssssssssss hshssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss

Can't be the breaks, can it? Only hear it on a 75.

That's the 14th stage bleed valve relieving overpressure in the compressor section before it goes to the combustors due to the flywheel effect of the fan. N2 slows down quickly and N1 wants to keep going for a while. More info over in Tech/Ops.

DL757Md
757 Most beautiful airliner in the sky!
 
ETStar
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 3:47 pm

Quoting Dl757md (Reply 9):

That's the 14th stage bleed valve relieving overpressure in the compressor section before it goes to the combustors due to the flywheel effect of the fan. N2 slows down quickly and N1 wants to keep going for a while. More info over in Tech/Ops.

Thanks for the quickie, although it was all jiberish to me. I recall seeing ET 752s arriving early in the morning at ADD, and after thundering down the runway, they seem to slow down and the hissss would go on and on. Anyhoo, will look at it in Tech-Ops.
 
F27XXX
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:15 pm

Quoting Dl757md (Reply 9):
That's the 14th stage bleed valve relieving overpressure in the compressor section before it goes to the combustors due to the flywheel effect of the fan. N2 slows down quickly and N1 wants to keep going for a while.


OH .. OK .. silly us for asking!

Chr*st, Dorothy .. in ENGLISH this time .. Jeez!
I'M BAAAAAAAACK!
 
dl757md
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:18 pm

757 Most beautiful airliner in the sky!
 
DLKAPA
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:22 pm

Quoting Glareskin (Reply 4):
Are you sure it wasn't an A320?

Do a search on AA A320 and let us all know how it turns out.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
F27XXX
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:32 pm

Quoting ETStar (Reply 8):
hhsssssssssssssssssssss hshssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss

No, silly ... u heard Brendan, the F/A , making his arrival announcement... jeeeeezus!

tony   

[Edited 2005-10-25 09:32:56]
I'M BAAAAAAAACK!
 
dl757md
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:32 pm

Quoting F27XXX (Reply 11):
Chr*st, Dorothy .. in ENGLISH this time .. Jeez!

Nice. Flame me for answering a question. I didn't have time to get into a long drawn out explanation breaking it down into layman's terms. That's why I pointed those interested to tech ops and the other thread I linked later. Stick to furniture if you don't want to get technical.  irked 

DL757Md
757 Most beautiful airliner in the sky!
 
F27XXX
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:36 pm

Quoting Dl757md (Reply 15):
Stick to furniture if you don't want to get technical.

Hey Hey ! Decaf! LOL .... Cmon i was just kidding with ya ... i wish it did make sense to me!

Tony

PS -- I am in total agreement with you -- the 757 is the most beautiful airliner in te sky!
I'M BAAAAAAAACK!
 
dl757md
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:43 pm

Quoting F27XXX (Reply 16):
Hey Hey ! Decaf! LOL .... Cmon i was just kidding with ya ... i wish it did make sense to me!

OK OK. You got me on the decaf thing. I'm doing chocolate covered espresso beans to stay awake right now. Sorry to jump all over you. When I have time I'll try and send you some info to explain how it all works.

DL757Md
757 Most beautiful airliner in the sky!
 
F27XXX
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 4:57 pm

Thanks man - sounds great -- and u can send a cpl of those choc covered espresso beans too, come to think of it! LOL

Tony  cheeky 
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Glareskin
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 5:32 pm

Quoting CdfMxTech (Reply 6):
AA doesn't operate A320s...so its a sure bet it was a 57!



Quoting DLKAPA (Reply 13):
Do a search on AA A320 and let us all know how it turns out.

American Airlines fleet:
Airbus narrowbody
A320: 278 aircraft
A319: 130 aircraft
A318: 46 aircraft in fleet and 40 on order
There's still a long way to go before all the alliances deserve a star...
 
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HAWK21M
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 5:57 pm

Power Transfer Unit.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
dfwagt
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 9:30 pm

Quoting Glareskin (Reply 19):
American Airlines fleet:
Airbus narrowbody
A320: 278 aircraft
A319: 130 aircraft
A318: 46 aircraft in fleet and 40 on order

Well, this is new. I must have missed the memo where we replaced everything with Airbuses.
 
Glareskin
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 9:59 pm

Quoting Dfwagt (Reply 21):
I must have missed the memo where we replaced everything with Airbuses.

This fleet renewal happened at the same moment CdfMxTech and DLKAPA changed the subject of this thread from 757 noise to AA fleet.....  Wink
There's still a long way to go before all the alliances deserve a star...
 
DrDeke
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 10:31 pm

Quoting F27XXX (Reply 11):
That's the 14th stage bleed valve relieving overpressure in the compressor section before it goes to the combustors due to the flywheel effect of the fan. N2 slows down quickly and N1 wants to keep going for a while.

Alright, alright.

"14th stage bleed valve" = After 14 sets of 'blades' in the engine's compressor, there is a valve that can dump some of the compresed air overboard in case the pressure is too high at this point.

"flywheel effect of the fan" = The fan in the front of the engine is very heavy and was spinning very rapidly when the engine was being used to fly the plane. When they cut the throttle, the fan does not stop right away, and the fan blows air into the compressor, causing the pressure there to be too high after 14 stages.

"N2" = The compressor and turbine shaft.

"N1" = The fan shaft.

-DrDeke
If you don't want it known, don't say it on a phone.
 
MarBergi
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 10:40 pm

Quoting Glareskin (Reply 19):
American Airlines fleet:
Airbus narrowbody
A320: 278 aircraft
A319: 130 aircraft
A318: 46 aircraft in fleet and 40 on order

I think you need to check your sources!!!!!!

Try this one American Airlines.

The only Airbus I can see are the 300's
 
Glareskin
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RE: AA 757 Sawing Noise

Tue Oct 25, 2005 10:52 pm

Quoting MarBergi (Reply 24):
I think you need to check your sources!!!!!!

I think you need to read more carefully!!!!
There's still a long way to go before all the alliances deserve a star...
 
PiedmontINT
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RE: AA 757 Sawing Noise

Wed Oct 26, 2005 8:05 am

Quoting Glareskin (Reply 4):

I think what he is trying to say is that the said "buzz saw" sound is very common on A320s.. hence the joke of saying are you sure it wasnt an A320.

So lay off of him, im sure he realizes that AA doesnt have any A320s
 
rdwelch
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RE: AA 757 Sawing Noise

Wed Oct 26, 2005 10:38 am

The PTU on the A320 Family sounds like Paul Bunyun on a bad date.  Embarrassment
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BWIA330
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RE: AA 757 Sawing Noise

Wed Oct 26, 2005 12:34 pm

Thats like what I always hear on the Airbus A330. When on the ground, there is this loud clunk sound, im not sure if its the hydralics or brakes. Does anyone know what causes that sound?

Regards,

BWIA330
 
474218
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RE: AA 757 Sawing Noise

Wed Oct 26, 2005 12:39 pm

Quoting Rdwelch (Reply 27):
The PTU on the A320 Family sounds like Paul Bunyun on a bad date.

Sounds like a long drawn out grunt.
 
Glareskin
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RE: AA 757 Sawing Noise

Wed Oct 26, 2005 3:50 pm

Quoting PiedmontINT (Reply 26):
I think what he is trying to say is that the said "buzz saw" sound is very common on A320s.. hence the joke of saying are you sure it wasnt an A320.

Thank you!
There's still a long way to go before all the alliances deserve a star...