CRJ900
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CFM56-7 More Economical Than CFM56-5?

Mon Dec 26, 2005 10:19 pm

I have read many times about the superior economic performance of the CFM56-7 engines that power the B737NG family. The CFM56-5 powers the A320 Family and are still selling like hotcakes, so they can't be that bad either...?

Is the CFM56-7 an improved CFM56-5 OR is the -7 basically the same as the -5 with the only difference being that its physical shape is a little different in order to fit under the 737's wing?

I know there are differences in thrust...

What's the word in the hangars?

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DAYflyer
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 12:55 am

They are both very economical, and some -5 engines do power the 737.
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 1:02 am

Quoting DAYflyer (Reply 1):
some -5 engines do power the 737

No CFM56-5 has ever powered a 737, AFAIK.
 
DAYflyer
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 1:03 am

Quoting Scorpio (Reply 2):
No CFM56-5 has ever powered a 737, AFAIK.

I thought they were used on the 600?? Perhaps I am mistaken.
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BR715-A1-30
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 1:05 am

The 737-100/200 have JT8D-7s or 15s
The 737-300/400/500 have CFM56-3B1 or 3C1
The 737-600/700/800/900 have CFM56-7B engines
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gigneil
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 12:49 pm

Quoting CRJ900 (Thread starter):
Is the CFM56-7 an improved CFM56-5 OR is the -7 basically the same as the -5 with the only difference being that its physical shape is a little different in order to fit under the 737's wing?

The CFM56-7 is basically a -5B/2P with a smaller fan and thusly a lower bypass ratio.

I would think that would negatively impact both noise and economy, but the -7 does have different fan blades as well as improved computer and maybe some other minor minor revisions.

For all intents and purposes, they're very similar engines.

N
 
Molykote
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 3:34 pm

I am not sure that a -5 would fit under the wing of a 737.

I could be wrong.
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lightsaber
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 4:54 pm

A -5 has a 68.3" diameter.

The 737 is limited by under wing clearence, hence the -7's 60.5" diameter fan.

Thus the -5 will not fit in the nacelle of the 737. The -7 nacelle would not pass the required testing on the 737 due to water injestion off of the nose gear (amoung other issues).
http://www.alair.com/Commercial/cfm56-5b.html

There continue to be aerodynamic improvements in both the -5 and -7. The -5c, which only goes on the A340-200/300 continues to have the lowest TSFC at cruise in the family (.567), partially due to the 72.3" fan on this model.
Compare, -5b at .596
I do not have a good -7 link, but since its mostly a -5b with a smaller fan... Comparing a -5b with a ~35 pressure ratio (climb) versus a -7 with an ~33 pressure ratio (climb)... Says the -5b should be more efficient.

http://www.cfm56.com/engines/cfm56-7/tech.html
http://www.cfm56.com/engines/cfm56-5b/tech.html

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HAWK21M
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 6:04 pm

Quoting BR715-A1-30 (Reply 4):
The 737-100/200 have JT8D-7s or 15s

In fact the -9,9A,15,15A,17,17A,17R.

Quoting Gigneil (Reply 5):
The CFM56-7 is basically a -5B/2P with a smaller fan and thusly a lower bypass ratio.

Whats the Bypass ratio like.
regds
MEL
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mandala499
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RE: CFM56-7 More Economical Than CFM56-5?

Tue Dec 27, 2005 11:25 pm

Mel,
732s got the -7 engines too... damn noisy buggers! LOL though I can only remember one here being used in Indonesia with -7s... again... the noisiest one of the lot... But I love the extra Harrier style inlets between the intake and the fan...

Mandala499
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HAWK21M
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RE: CFM56-7 More Economical Than CFM56-5?

Wed Dec 28, 2005 2:28 pm

Quoting Mandala499 (Reply 9):
732s got the -7 engines too

Thats correct, Guess I overlooked them  Smile

Quoting Mandala499 (Reply 9):
But I love the extra Harrier style inlets between the intake and the fan...

The Secondary air inlet doors on the engine nacelles to allow extra air flow with high thrust and low speed.

regds
MEL
I may not win often, but I damn well never lose!!! ;)

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