LH526
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B707 JT3C JT4A Noise Compressors

Thu Oct 15, 2009 6:06 pm

Guys, another in depth B707/B720 question:

I'm in bit of a trouble here: Below is a Boeing doc about the cowl dimensions of the Boeing 707/720 JT3C & JT4A
Big version: Width: 599 Height: 800 File size: 77kb

Apperently both cowls are different in size and length (the dimension differences are nearly unnoticeable on photos) However my question is more exhaust oriented as I would need some information on the exhaus pipes / noise compressor pipes:

The photo below shows the JT3C engine on a B720. The noise compressors clearly consists of 8 pipes in 2 rings each.

View Large View Medium
Click here for bigger photo!

Photo © Frank C. Duarte Jr.


Whereas this one below possibly is a JT4A engine with 10 noise compression pipes in the outer ring.

However, on "the other site" I came across pics of a JT3C equipped B720 with 10 noise compressor tubes.

My research revealed that earlier noise compressor design has 10, later has only 8 noise compressor tubes.

Is anybody out there able to heklp my with these questions? is there a doc or further info on the noise compression pipes??

Any help is highly appreciated!
Thanks a million!

Mario
LH526
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timz
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RE: B707 JT3C JT4A Noise Compressors

Thu Oct 15, 2009 9:21 pm



Quoting LH526 (Thread starter):
on a B720. The noise compressors clearly consists of 8 pipes in 2 rings

I forget... which engines had the daisy exhausts-- like a flower, instead of a cluster of pipes? That's what the 720 looks like to me.

Quoting LH526 (Thread starter):
Whereas this one below possibly is a JT4A engine

Looking at the wing trailing edge, I'm guessing that's a 707-120.
 
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Aaron747
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RE: B707 JT3C JT4A Noise Compressors

Thu Oct 15, 2009 10:47 pm

For added fun, there's also the 7-nozzle starburst pattern on the Rolls Royce Conway-powered -420s:

http://www.rrec.de/uploads/pics/1957_Gil_707_Rolls-Royce_Conway_01.JPG
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LH526
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RE: B707 JT3C JT4A Noise Compressors

Fri Oct 16, 2009 12:44 am



Quoting Aaron747 (Reply 2):
For added fun, there's also the 7-nozzle starburst pattern on the Rolls Royce Conway-powered -420s:

Thanks, I got the B704 (RR Conways) and the JT3D engines all covered, Im still getting confused on the JT3C and JT4A exhausts

Quoting Timz (Reply 1):
Looking at the wing trailing edge, I'm guessing that's a 707-120.

You're right, the B707 and B720 share the JT3C engine

Quoting Timz (Reply 1):
I forget... which engines had the daisy exhausts-- like a flower, instead of a cluster of pipes? That's what the 720 looks like to me.

The 'single-flower' was the RR Conway, than you have the early JT3C with three radial layers of pipes and the JT4 engine with a flower-style inner exhaust encompassed by pipes.

The point is that there are 8-pipe and 10-pipe exhausts and (from photos) i can't figure out wich engine had what noise compressor configuration.
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Aaron747
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RE: B707 JT3C JT4A Noise Compressors

Fri Oct 16, 2009 1:22 pm

Quoting Lh526 (Reply 3):

The point is that there are 8-pipe and 10-pipe exhausts and (from photos) i can't figure out wich engine had what noise compressor configuration.

I recall seeing pictures in the 1962 World Book encyclopedia (my grandparents kept them for ages) of a typical airline flight featuring Pan Am. The aircraft pictured was one of the early build 707-123s with JT3Cs. In one of the pictures, the Captain was doing an underwing walkaround and there were clearly 10 nozzles. However, in another picture, probably taken later (who knows?) there were only 8. I am now thoroughly confused.

This website may be FS-related, but a lot of the posters are old 707 hands with mountains of knowledge - I highly suggest inquiring there:

http://tonymadgehjg.proboards.com/index.cgi?

[Edited 2009-10-16 06:24:37]
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timz
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RE: B707 Silencers

Fri Oct 16, 2009 5:37 pm



Quoting Aaron747 (Reply 4):
there were clearly 10 nozzles.

I.e. 21 total?
 
LH526
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RE: B707 JT3C JT4A Noise Compressors

Sat Oct 17, 2009 2:42 am

Quoting Aaron747 (Reply 4):
However, in another picture, probably taken later (who knows?) there were only 8. I am now thoroughly confused.

Thanks Aaron747. Your're right, that's exactly my confusion as well. My guess is that the earlier design consisted of 10, wich was later improved to only 8 on the JT3C engines

Quoting Timz (Reply 5):
I.e. 21 total?

Correct! For the 10 tube version it's two 10 tube rings and the center tube adding up to 21, for the 8 tube noise canceller it's 8+"compressor flower"

[Edited 2009-10-16 20:29:36 by LH526]
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474218
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RE: B707 JT3C JT4A Noise Compressors

Sat Oct 17, 2009 3:23 am

I am a little confused about this entire thread: I think what you are calling "Noise Compressors" are really "Noise Suppressors". They were the first attempt to quite jet engines on civilian airliner.
 
LH526
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RE: B707 JT3C JT4A Noise Compressors

Sat Oct 17, 2009 3:32 am

Quoting 474218 (Reply 7):
I am a little confused about this entire thread: I think what you are calling "Noise Compressors" are really "Noise Suppressors". They were the first attempt to quite jet engines on civilian airliner.

Correct, some documents call them noise compressor, guess that's where I got the wrong term from.

Off course I'm inquiring about the noise suppressors ... hard to find any information about them whatsoever .... hence I'm moreso highly appreciating your input!

[Edited 2009-10-16 20:39:13 by LH526]
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timz
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RE: B707 JT3C JT4A Noise Compressors

Sat Oct 17, 2009 6:38 pm

My notes from Airlift/American Aviation (the magazine) say the JT3C on the 707-120 used 21 tubes, but the 720 and 707-320 both used 9 total. That must mean one centered with eight around it? Seems like we ought to be able to find a pic.
 
Viscount724
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RE: B707 JT3C JT4A Noise Compressors

Sun Oct 18, 2009 12:31 am

Quoting Timz (Reply 9):
My notes from Airlift/American Aviation (the magazine) say the JT3C on the 707-120 used 21 tubes, but the 720 and 707-320 both used 9 total. That must mean one centered with eight around it? Seems like we ought to be able to find a pic.

These photos not very clear but it does look like the -120 (left) has more tubes than the the -320 (right).


View Large View Medium
Click here for bigger photo!

Photo © Robert Sieloff
View Large View Medium
Click here for bigger photo!

Photo © Chartrain Didier



Also found following clearer 1985 photo of an ex-Pan Am -320 being used as a testbed by GE (CFM56 in #2 position).

http://www.air-and-space.com/19850509%20Mojave/85161%20707-321%20N37681%20Batch%20Air%20left%20engines%20rear%20l.jpg



And a very clear photo of an original Qantas -138 (the shorter-fuselage version of the -120 built only for QF), also showing a spare engine in a 5th pod. 21 tubes counting the one in the middle.

http://www.adastron.com/707/gallery/vh-ebg-2.jpg


[Edited 2009-10-17 17:44:46]
[Edited 2009-10-17 17:58:09]

[Edited 2009-10-17 18:00:15]
 
ex52tech
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RE: B707 JT3C JT4A Noise Compressors

Sun Nov 01, 2009 2:31 am

On another note.
Those suppressors could not have held up well. We had some cracking trouble with the tail pipes on the J-57-P-43WB on the B-52G, which had some wedges added to help suppress the noise.

These things must have had cracks everywhere, especially with water injection being used. I know that there was some thrust loss associated with them. Which made a bad situation worse I'm sure.
"Saddest thing I ever witnessed....an airplane being scrapped"

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