CRJ900 From Norway, joined Jun 2004, 2148 posts, RR: 1 Posted (8 years 2 months 2 weeks 1 day 7 hours ago) and read 7269 times:
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?
Gigneil From United States of America, joined Nov 2002, 16345 posts, RR: 87
Reply 5, posted (8 years 2 months 2 weeks 17 hours ago) and read 7026 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.
Lightsaber From United States of America, joined Jan 2005, 12309 posts, RR: 100
Reply 7, posted (8 years 2 months 2 weeks 13 hours ago) and read 6989 times:
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.
Mandala499 From Indonesia, joined Aug 2001, 6499 posts, RR: 74
Reply 9, posted (8 years 2 months 2 weeks 6 hours ago) and read 6947 times:
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...
When losing situational awareness, pray Cumulus Granitus isn't nearby !