Print from Airliners.net discussion forum
http://www.airliners.net/aviation-forums/tech_ops/read.main/238160/

Topic: CFM-56 Questions
Username: JetMech
Posted 2008-09-21 05:40:14 and read 9162 times.

G'day Techies,

I found some interesting pictures of CFM56-3 and CFM56-7B engines on the database. What I found most interesting was the differing generator setups, and the changes this makes to the fan cowlings. It appears the -3 has a separate CSD / generator set-up, whilst the -7B has an IDG. Was it possible to get an IDG fitted to the -3?

View Large View Medium
Click here for bigger photo!

Photo © Martin Hodgson
View Large View Medium
Click here for bigger photo!

Photo © Irfan Caliskan - AirTeamImages



View Large View Medium
Click here for bigger photo!

Photo © A J Best
View Large View Medium
Click here for bigger photo!

Photo © Carlos F


The fan cowlings of the -3 seem to be much longer to allow for access to the generator. Is the remaining part of the inlet cowl readily separated from the rest of the engine? The -7B has an inlet cowling of the type that is more familiar to me.

The side mounted gearbox is an interesting set-up. From the looks of it, there appears to be what I assume is a shrouded shaft at the top rear of the gearbox, which itself ends up at another box like structure. Does this box contain a set of bevel gears? Does the driveshaft from the engine core come out "sideways" through one of the fan case struts?

Regards, JetMech

Topic: RE: CFM-56 Questions
Username: AA737-823
Posted 2008-09-21 05:46:02 and read 9154 times.

I can't answer your latter questions, but I think I can take a stab at the first ones.

Quoting JetMech (Thread starter):
Was it possible to get an IDG fitted to the -3?

Not to my knowledge. Boeing reverted to the older IDG design for the NexGens due to reliability issues and cost issues (cough cough, Southwest strikes again).

The remainder of the inlet cowl looks like it comes off in the customary way, on both airplanes... lots of twelve point bolts!!!
But then, I'm familiar with PRATT powered 737s, so I might be predisposed to think that.

Topic: RE: CFM-56 Questions
Username: JetMech
Posted 2008-09-21 06:04:35 and read 9151 times.



Quoting AA737-823 (Reply 1):
(cough cough, Southwest strikes again).

I guess Southwest are not a customer to be messed with given the number of 737's they buy Big grin .

Quoting AA737-823 (Reply 1):
lots of twelve point bolts!!!

Fair enough. The -3 design is interesting however, as the only time I have seen a nose cowl look like that is when the outer skin was de-riveted and removed in the sheet metal shop. The inner skin must be a fair bit thicker to maintain the required amount of stiffness  scratchchin 

Quoting AA737-823 (Reply 1):
PRATT powered 737s,

Old school 737's! I was also looking at this picture trying to discern where the engine mounts were located!

View Large View Medium
Click here for bigger photo!

Photo © 737doctor


Regards, JetMech

Topic: RE: CFM-56 Questions
Username: IFixPlanes
Posted 2008-09-21 09:48:53 and read 9090 times.



Quoting JetMech (Thread starter):
...Does the driveshaft from the engine core come out "sideways" through one of the fan case struts?

Yes.
CFM56-7:

Topic: RE: CFM-56 Questions
Username: Mender
Posted 2008-09-21 14:19:17 and read 9023 times.

It's worth mentioning that most 737 classics have the Constant Speed Drive and generator setup like in the photo's that you've posted.

However some 737 classics have Variable Speed Constant Frequency generators but these are not that common.

http://www.b737.org.uk/generators.htm

Topic: RE: CFM-56 Questions
Username: IFixPlanes
Posted 2008-09-22 10:47:11 and read 8911 times.



Quoting Mender (Reply 4):
... some 737 classics have Variable Speed Constant Frequency generators but these are not that common.

LH operate their 737CL fleet in most cases in mixed configuration. One generator is a CSD the other is a VSCF.
CSD /CSD is also OK. But LH try to avoid a VSCF / VSCF configuration.

Topic: RE: CFM-56 Questions
Username: TristarSteve
Posted 2008-09-22 12:46:55 and read 8880 times.



Quoting Mender (Reply 4):
However some 737 classics have Variable Speed Constant Frequency generators but these are not that common

All the BA B737-400s were delivered with VSCF.

But after many years of problems with them it was finally decided that it was worth removing them, and now they are no more. They really were unreliable, perhaps a bit ahead of their time. The problem was the electronics that converted the output to constant frequency were mounted on the VSCF, where I suppose they should have been fitted in the airframe.

Topic: RE: CFM-56 Questions
Username: CFMTurboFan
Posted 2008-09-22 14:40:42 and read 8848 times.



Quoting JetMech (Thread starter):

The side mounted gearbox is an interesting set-up. From the looks of it, there appears to be what I assume is a shrouded shaft at the top rear of the gearbox, which itself ends up at another box like structure. Does this box contain a set of bevel gears? Does the driveshaft from the engine core come out "sideways" through one of the fan case struts?

JetMech,

This "box" you refer to is the Transfer Gearbox (TGB), it connects to the Internal gearbox (IGB) located at the front of the N2 (HP) compressor spool. The main Accessory gearbox (AGB) is mounted on the left side of the fan frame. It was mounted here by CFMI to give extra ground clearance for the 737.

A transfer drive shaft connects the IGB and TGB which runs inside the 9 o' clock fan frame strut when viewed from the rear. There is another drive shaft (which you identified as shrouded) between the TGB and the AGB. Only the IGB & TGB have beveled gears. The the drive shaft from the TGB to the AGB is located in splines and held in place with a large nut during installation.

Only the -3 and -7 CFMs have the AGBs mounted at the 7/8 o'clock position. -5A, 5B & 5C engines have the TGB and AGB mounted at the 6 o'clock position as there is plenty of ground clearance on Airbus aircraft.

CFM Turbo Fan

Topic: RE: CFM-56 Questions
Username: JetMech
Posted 2008-09-25 15:07:26 and read 8637 times.

G'day Gents,

Thanks for all the info!

Quoting IFixPlanes (Reply 3):

Nice picture! It's good to see that there is still a place for good old fashioned mechanical components in something as sophisticated as a jet engine.

Quoting CFMTurboFan (Reply 7):
Only the -3 and -7 CFMs have the AGBs mounted at the 7/8 o'clock position. -5A, 5B & 5C engines have the TGB and AGB mounted at the 6 o'clock position as there is plenty of ground clearance on Airbus aircraft.

I see. I suppose this was more in line with the original engine design? IIRC, the 737 runs the side gearbox arrangement, which actually is the modified version.

Regards, JetMech

Topic: RE: CFM-56 Questions
Username: AA737-823
Posted 2008-09-30 02:13:16 and read 8410 times.



Quoting Mender (Reply 4):
However some 737 classics have Variable Speed Constant Frequency generators

My understanding is that the VSCF setup is total junk. Douglas and Delta learned a similar lesson with the MD-90s. For this reason, Boeing abandoned the VSCF on the -NG, IIRC.

Quoting JetMech (Reply 8):
I see. I suppose this was more in line with the original engine design? IIRC, the 737 runs the side gearbox arrangement, which actually is the modified version.

I think that's right. The DC-8s had them on the bottom.

Topic: RE: CFM-56 Questions
Username: CFMTurboFan
Posted 2008-09-30 08:28:43 and read 8379 times.

DC-8 had the CFM56-2 fitted which is the same as the USAF KC135 fleet.

Topic: RE: CFM-56 Questions
Username: JetMech
Posted 2008-10-02 13:09:05 and read 8222 times.



Quoting AA737-823 (Reply 9):
I think that's right. The DC-8s had them on the bottom.



Quoting CFMTurboFan (Reply 10):
DC-8 had the CFM56-2 fitted which is the same as the USAF KC135 fleet.

Thanks for that! I was actually trying to think of what aircraft used the original version of the CFM-56.

Regards, JetMech


The messages in this discussion express the views of the author of the message, not necessarily the views of Airliners.net or any entity associated with Airliners.net.

Copyright © Lundgren Aerospace. All rights reserved.
http://www.airliners.net/