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CFM56-7 More Economical Than CFM56-5?  
User currently offlineCRJ900 From Norway, joined Jun 2004, 2171 posts, RR: 1
Posted (8 years 7 months 2 days 6 hours ago) and read 7629 times:
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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?

Happy Festive Season, fellow nutters  Smile

Ivan


Come, fly the prevailing winds with me
10 replies: All unread, jump to last
 
User currently offlineDAYflyer From United States of America, joined Sep 2004, 3807 posts, RR: 3
Reply 1, posted (8 years 7 months 2 days 3 hours ago) and read 7534 times:

They are both very economical, and some -5 engines do power the 737.


One Nation Under God
User currently offlineScorpio From Belgium, joined Oct 2001, 5014 posts, RR: 44
Reply 2, posted (8 years 7 months 2 days 3 hours ago) and read 7524 times:

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

No CFM56-5 has ever powered a 737, AFAIK.


User currently offlineDAYflyer From United States of America, joined Sep 2004, 3807 posts, RR: 3
Reply 3, posted (8 years 7 months 2 days 3 hours ago) and read 7521 times:

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.



One Nation Under God
User currently offlineBR715-A1-30 From , joined Dec 1969, posts, RR:
Reply 4, posted (8 years 7 months 2 days 3 hours ago) and read 7514 times:

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


User currently offlineGigneil From United States of America, joined Nov 2002, 16347 posts, RR: 85
Reply 5, posted (8 years 7 months 1 day 15 hours ago) and read 7387 times:

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


User currently offlineMolykote From United States of America, joined Aug 2005, 1340 posts, RR: 29
Reply 6, posted (8 years 7 months 1 day 13 hours ago) and read 7357 times:

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

I could be wrong.



Speedtape - The asprin of aviation!
User currently offlineLightsaber From United States of America, joined Jan 2005, 12884 posts, RR: 100
Reply 7, posted (8 years 7 months 1 day 11 hours ago) and read 7350 times:
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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

Lightsaber



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 8, posted (8 years 7 months 1 day 10 hours ago) and read 7339 times:

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



Think of the brighter side!
User currently offlineMandala499 From Indonesia, joined Aug 2001, 6761 posts, RR: 76
Reply 9, posted (8 years 7 months 1 day 5 hours ago) and read 7308 times:

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



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 10, posted (8 years 7 months 14 hours ago) and read 7258 times:

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



Think of the brighter side!
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