QANTAS747-438
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American 757 Engines

Wed May 29, 2002 9:55 am

Today I was hanging out at LAX, and I noticed that only the AA 757-200's with the engines like in the picture below, sounded like actual propeller planes when they took off. DL 757s, UA 757s, US 757s all sounded like normal roars of engines, but AA's 757s sounded like propeller planes. Why is that?


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Photo © Chris Coduto



My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
 
sxmarbury33
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RE: American 757 Engines

Wed May 29, 2002 10:46 am

Well they are RB-211 engiens which are known some what for that sound. It may have something to do with the triple spool?
 
Duncan
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RE: American 757 Engines

Wed May 29, 2002 11:54 am

Delta and United both use the PW2037 on their 757's, though US Airways use the RB211-535E4 so that shouldn't sound any different from the AAL RB211's. A lot may have to do on where in the flight profile they are (i.e. take off, climb, descent and approach etc,....)

Duncan
 
wilcharl
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RE: American 757 Engines

Wed May 29, 2002 12:43 pm

the P&W engines have a more distinct buzz saw sound on talke off then the RB's
 
QANTAS747-438
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RE: American 757 Engines

Wed May 29, 2002 1:03 pm

I seemed to hear the opposite of what Wilcharl says... the RB's had the buzz saw sound while the PW's of United and Delta were huge roars. All of these happened upon takeoff off of 25L.

Also, what does the triple spool mean or do?
My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
 
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ATA L1011
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RE: American 757 Engines

Wed May 29, 2002 1:22 pm

Yes the RR on the 757 is a lot more buzzy than the PW, you know a RR 757 on takeoff. The PW on the 757 makes that sound that all large turbofans make at near or full power but to a lesser extent than the RR on the 757.
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wilcharl
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RE: American 757 Engines

Wed May 29, 2002 1:50 pm

hmmph i didnt get it as much on the RR powered ones but i noticed it today on a P&W powered one i was on...
 
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American 767
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RE: American 757 Engines

Thu Jun 06, 2002 8:25 am

Triple spool means that the engine is designed with three different stages of compressor blades, intake air is compressed in three successive steps before mixing with fuel in the combustion chamber. Yes, it is true that RR-RB211 engines are noisy compared to PW-2037 engines, they have a lower bypass ratio but they deliver more thrust. RR engines, in the case of the Boeing 757 which is the aircraft related to the scope of this topic, deliver 43000 lbs of thrust each, while PW engines deliver only 37000 or 38000 lbs of thrust. I have flown on both RR and PW powered 757's and I do feel there is such a difference. On RR powered 757's, during climb at full power, you almost feel like you are travelling on a rocket!

American, British Airways, Continental and US Airways operate the 757's with RR engines. Eastern had RR engines on 757's too. Delta, Northwest and United chose instead the PW engine on 757's. That doesn't surprise me because Northwest and United always had a special relationship with Pratt & Whitney. TWA's 757's had PW engines, that's why you'll see sometimes American 757's with PW engines. It's easy to spot a PW engine on a 757. The PW engine has a larger cowling surrounding the largest fan to increase the bypass ratio, the RR engine dosn't have that. The cowling on the RR engine surrounds the whole machinery, there is a nozzle but you don't see it. That's how I can tell an American 757 comes from TWA.

Ben Soriano
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mlsrar
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RE: American 757 Engines

Fri Jun 07, 2002 3:35 am

Most Charter operators have chosen the 535E4/535E4B as well for a simple matter of the power mentioned above. The wingtime reliability of the RR has proven itself, and its efficiency is spoken for by preference.

However, the PW does offer both a 2037 and a 2040 for the 757. Delta and United both have a mixed bag of 37s and 40s, UPS chose the 40 for their higher MTOWs.
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Duncan
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RE: American 757 Engines

Fri Jun 07, 2002 4:16 am

UPS also operate the 757 with R-R power, I think along with AA, they are the only operators to fly a mixed PW/RR fleet.

Duncan
 
alphazulu
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RE: American 757 Engines

Sun Jun 09, 2002 1:27 pm

WHATEVER WAY YOU PUT IT, I LOVE THE SOUND OF THE AA 757'S RB211's, IT GIVES ME A WARM FEELING INSIDE Big thumbs up
 
A330
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RE: American 757 Engines

Tue Jun 11, 2002 6:37 pm

OK, just to be exact, the RR RB211 engine actually produces LESS sound than her american concurrent, thanks to the mixed exhaust system. The exhaust of the by-pass and turbine air are mixed at the end, instead as kept seperated, which reduces the exhaust noice. The compressor noice is however bigger on the RR engine, indeed due to the somewhat lower by-pass. It is still a high by-pass engine though, and the RB211 is known as being the best develloped engine in the industry!!
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geotrash
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RE: American 757 Engines

Sun Jun 16, 2002 9:59 am

If memory serves, the distict buzz-saw sound is actually the tips of the fan blades exceeding the sound barrier.

-Geo

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