SJC-Alien
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Boeing 757 At SJC Vid & Question...

Wed Aug 30, 2006 2:17 pm

http://video.google.com/videoplay?do...d=-3767439211363772892&q=tom+vance

I filmed this last saturday at SJC.....when the '57 rolls out towards the exit, it was rather loud and was making a sound that sounded like a real loud hiss as it rolls by, then it goes quiet........then listen to the audio just before 1:18 on the ticker, as the jet turns right of 30L,,and then you hear the noise start up again, a very loud hiss as the wing-slats are retracted...then it goes away. What makes this noise...?

Thanks

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as739x
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RE: Boeing 757 At SJC Vid & Question...

Wed Aug 30, 2006 3:33 pm

Without watching the video I think its the APU. They are notoriously loud on the '57. I'll watch the video when I get home (can't watch from work). But its not the flaps and slats, you can't even hear that next to the plane when the engines are running.

ASLAX
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Silver1SWA
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RE: Boeing 757 At SJC Vid & Question...

Wed Aug 30, 2006 4:15 pm

I know what you are talking about. Without watching the video, I'm guessing it's either a UA or DL 757...

I have only ever heard it on P&W powered 757s so I'm assuming it deals with that specific engine type. Not really sure what the sound is though.

[Edited 2006-08-30 09:17:06]
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SJC-Alien
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RE: Boeing 757 At SJC Vid & Question...

Wed Aug 30, 2006 10:40 pm

Ok,,usually, we only get UA and DL 75's at SJC...and I have heard this noise on the UA 75's also.....but since this is the only airport I can get this close to the braking action, this is only where I have heard this,,( plus it was fairly quiet this night, (no SJC parking shuttle bus going by behind me ruining the noise as usual..) re-watching the video, right after the tower clears them to KILO and the gate, the read-back is complete, then the hiss starts again, then quits as the flaps drop, but yeah, I figured it wasn't the flaps making that noise.... Wink

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dakota123
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RE: Boeing 757 At SJC Vid & Question...

Wed Aug 30, 2006 11:21 pm

I've wondered this, too. I believe the sound is air flowing from the bleed doors which are located between the low pressure compressor and the high pressure compressor. The doors are there to help match airflow between the low and high pressure compressors at low loads.

Dakota123
 
jacobin777
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RE: Boeing 757 At SJC Vid & Question...

Thu Aug 31, 2006 12:06 am

Quoting SJC-Alien" class=quote target=_blank>SJC-Alien (Reply 3):
Ok,,usually, we only get UA and DL 75's at SJC...

don't forget we'll be getting the return of the "Nerd Bird" AA 757-200 too.. Smile


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BatonOps
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RE: Boeing 757 At SJC Vid & Question...

Thu Aug 31, 2006 12:22 am

Maybe it could from the thrust reversers closing?
 
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RE: Boeing 757 At SJC Vid & Question...

Thu Aug 31, 2006 2:24 am

Quoting Dakota123 (Reply 4):
I believe the sound is air flowing from the bleed doors which are located between the low pressure compressor and the high pressure compressor. The doors are there to help match airflow between the low and high pressure compressors at low loads.

Bleed air of some kind would be my only guess.

Quoting SJC-Alien" class=quote target=_blank>SJC-Alien (Reply 3):
Ok,,usually, we only get UA and DL 75's at SJC...and I have heard this noise on the UA 75's also.....but since this is the only airport I can get this close to the braking action, this is only where I have heard this

When I worked at SJC, AA had daily 757s, most commonly RR powered 757s. I never heard the sound from AA's 757s so I pretty much drew the conclusion that it is something only heard on P&W 757s.


Quoting SJC-Alien" class=quote target=_blank>SJC-Alien (Reply 3):
re-watching the video, right after the tower clears them to KILO and the gate, the read-back is complete, then the hiss starts again, then quits as the flaps drop, but yeah, I figured it wasn't the flaps making that noise....



Quoting BatonOps (Reply 6):
Maybe it could from the thrust reversers closing?

I hear this sound all the time when UA or DL 757s land here at SAN. Typically at SAN it is heard at the very end of the roll-out seconds after the reversers stop making their noise. I have never really payed attention to the reversers to see if they were open, closed, or closing while the sound in question in being heard. But I don't think it has anything to do with the state of the reversers. I do remember that when I was at SJC it was actually more common to hear this sound after the aircraft exited the runway and begun it's taxi back to terminal C. It was SOOOOOOOOOOO loud for us on the WN ramp since they were right in front of us moving slowly when they would make the sound. We used to jokingly say they did it on purpose just to piss us off.

I'm surprised the answer hasn't popped up yet in this thread. Maybe if it was in Tech/Ops we would see more activity in here. I have been too afraid to ask this question myself as I was certain this has probably been discussed before and a simple search (that I am too lazy to do) would lead me to the answer.
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SJC-Alien
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RE: Boeing 757 At SJC Vid & Question...

Thu Aug 31, 2006 11:11 am

...yes, thanks for all of the info.......I was 'directed' to post videos on this forum only....but it was just for fun to see of anybody knew off-hand, Dakota 123 might be the closest to the correct answer.............I feel. But thanks to all.

Alien
 
sjsu2sjcAA777
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RE: Boeing 757 At SJC Vid & Question...

Thu Aug 31, 2006 2:40 pm

hey buddy i hear this sound all the time when the 757 lands, my guess would be the thrust reversers.
 
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RE: Boeing 757 At SJC Vid & Question...

Thu Aug 31, 2006 3:18 pm

Quoting Sjsu2sjcAA777 (Reply 9):
hey buddy i hear this sound all the time when the 757 lands, my guess would be the thrust reversers.

It is not the thrust reversers. It happens after the reversers have completed their job. Please read the thread before posting.

[Edited 2006-08-31 08:19:30]
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.