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CFM56 Engine Series  
User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Posted (2 years 3 months 1 week 8 hours ago) and read 4756 times:

I have looked and cannot seem to find the reasoning behind the series numbering of the CFM56 engines, i.e 5,6,7b,7E

Do you numbers mean anything?

14 replies: All unread, jump to last
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 1, posted (2 years 3 months 1 week 7 hours ago) and read 4716 times:

Quoting smartt1982 (Thread starter):
I have looked and cannot seem to find the reasoning behind the series numbering of the CFM56 engines, i.e 5,6,7b,7E

Do you numbers mean anything?

The number is, I believe, the sequence they were developed. I don't know what happened to -1, but -2 was the first one in service and they seem to follow that.

The extensions to the number designate derivatives of that engine. The 7B came after the original -7, the 7BE was an improved -7B, etc.

Tom.


User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 2, posted (2 years 3 months 6 days 15 hours ago) and read 4544 times:

As Tom said, there is a logical order that follows the development sequence of the individual models.

I couldn't find anything on the -1. Possibly a development model which led to the first production models.

The -2 was the first production version, used mainly to re-engine military B707 derivatives and the DC-8. The -2A2/3 was the initial model, the -2B1 a slightly reduced thrust development, and the -2C1 a civil development for the DC-8.

The -3 was developed for the B737-300/400/500 series. Models -3B1, -3B2 and -3C1 all being similar, but having sequentially increasing thrust ratings.

The -4 was planned for the A320 series, but didn't stack up when compared to the V2500. It was abandoned in favor of the improved -5 series.

The -5A series was the initial model developed for the A319/320 series. The -5A1 was the baseline model for the A320, and the -5A3 being an increased thrust model. The -5A4 the baseline A319 engine, and the -5A5 the higher thrust model.

The -5A series gave way to the -5B series that covers the entire A318/319/320/321 line. The -5B1/2/3 is for the A321, the -5B4 for the A320, the -5B5/6/7 for the A319, and the -5B8/9 for the A318.

The -5C series was developed as a higher thrust model for the A340 line, the -5C2/3/4 all sequentially more powerful.

The -6, again, who knows. Perhaps an in-house project that never warranted production.

The -7 is the current model for the B737-600/700/800/900 series. The designations, however, are changed to reflect the thrust rating of the individual models, i.e. the -7B20 rated at 20,600 lbs, the -7B27 rated at 27,300 lbs, etc.

The -7BE series is currently under development as an improvement of the -7B series. If past models are any indication, the production version may very well be called the -7C.

While a bit confusing, the engine designations do follow a logical sequence. Hope I didn't confuse things too much.

PC



In-trail spacing is a team effort.
User currently offlineakiss20 From United States of America, joined Sep 2007, 609 posts, RR: 5
Reply 3, posted (2 years 3 months 6 days 4 hours ago) and read 4316 times:

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User currently offlineStitch From United States of America, joined Jul 2005, 30978 posts, RR: 86
Reply 4, posted (2 years 3 months 6 days 4 hours ago) and read 4312 times:
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Quoting PapaChuck (Reply 2):
The -7BE series is currently under development as an improvement of the -7B series. If past models are any indication, the production version may very well be called the -7C.

I believe the CFM56-7BE "Evolution" series of engines became standard on new 737NG deliveries starting around a year ago.


User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 5, posted (2 years 3 months 6 days 3 hours ago) and read 4293 times:

You may very well be correct. I pulled that off the CFM website, and it didn't appear to have been updated recently.

PC



In-trail spacing is a team effort.
User currently offlinermm From Australia, joined Feb 2001, 524 posts, RR: 1
Reply 6, posted (2 years 3 months 5 days 23 hours ago) and read 4201 times:

IIRC there's a -3B4 fitted to the 735, however the thrust rating bucks the sequential trend going down to 18,500.

User currently offlineTristarsteve From Sweden, joined Nov 2005, 4007 posts, RR: 34
Reply 7, posted (2 years 3 months 5 days 10 hours ago) and read 4066 times:

Quoting PapaChuck (Reply 2):
The -4 was planned for the A320 series, but didn't stack up when compared to the V2500.

When the A320 was first developed, there was no choice.
The V2500 followed years later.


User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 8, posted (2 years 3 months 5 days 9 hours ago) and read 4034 times:

No, that’s really helpful info cheers

With regards to Rated Thrust. Is that the thrust we would get from the engine if we "firewalled" the thrust levers or is it just the actual rating (i.e. 26,24,22) that we have set via the FMC?

Basically what is the max we ever get from the engine if we firewalled the thrust levers?

is it the rating that CFM said it can do during certification or is it just the rating we have been certified for or just what we have in our performance charts, with this I am thinking the CFM 7 Series we have on the 738 and the ratings we have available are 26,24 and 22K.

If I firewalled it, is the max amount of thrust I will ever be able to get from the engine a thrust of 26K? or would I be able to get whatever the engine is able to produce ( if this is more).

If I am not able to get everything the engine can give me, how do they limit this?


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 9, posted (2 years 3 months 5 days 6 hours ago) and read 3988 times:

Quoting smartt1982 (Reply 8):
With regards to Rated Thrust. Is that the thrust we would get from the engine if we "firewalled" the thrust levers

Sort of. For most engines, yes. The 737NG is an oddball in that it can go to the highest rated thrust for the model, rather than just the engine. Physically, they're all the same.

Quoting smartt1982 (Reply 8):
is it just the actual rating (i.e. 26,24,22) that we have set via the FMC?

No, that's a derate. The engine rating doesn't change when you change the FMC selection. The FMC does talk to the engine to make sure the performance tables match the engine rating.

Quoting smartt1982 (Reply 8):
Basically what is the max we ever get from the engine if we firewalled the thrust levers?

The rated thrust in almost all cases.

Quoting smartt1982 (Reply 8):
is it the rating that CFM said it can do during certification or is it just the rating we have been certified for or just what we have in our performance charts, with this I am thinking the CFM 7 Series we have on the 738 and the ratings we have available are 26,24 and 22K.

In the specific case of the -7 engine on the 737-800, it would go to 27k (the maximum for the 737-800).

Quoting smartt1982 (Reply 8):
If I firewalled it, is the max amount of thrust I will ever be able to get from the engine a thrust of 26K? or would I be able to get whatever the engine is able to produce ( if this is more).

You would never get what the engine is able to produce; that's always higher than the rating.

Quoting smartt1982 (Reply 8):
If I am not able to get everything the engine can give me, how do they limit this?

The engine maker knows how much fan speed (N1) correlates to how much thrust. When the engine was built they put it on a thrust stand and figured out the correction between N1 (fan speed) and actual thrust for that specific engine. That correction ("the trim") was loaded to some solid state memory on the engine.

When you firewall the throttle you send a command to the EEC that says "Give me everything you can." The EEC knows what rating that engine has (via the programming plug on the EEC) and what N1 that should be. It applies the trim for that engine to the "stock" N1 number then runs the fuel up until the fan is going that fast.

With RR/PW engines they use a different thrust setting parameter (EPR for PW, TPR for RR) but it's functionally equivalent to fan speed.

Tom.


User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 10, posted (2 years 3 months 4 days 9 hours ago) and read 3780 times:

Quoting tdscanuck (Reply 9):
It applies the trim for that engine to the "stock" N1 number then runs the fuel up until the fan is going that fast.

My understanding is that if I firewalled the levers all I would ever get is the RATED thrust as per the EEC limit that you described.

In regards to the EEC in ALT mode, there is lots of restrictions, what would happen if I walled the levers then, what thrust could I get? If it gives me more than the RATED, is this really a problem, surely the engine has been certified for it.

Is it not like chipping your car to be able to go faster?


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 11, posted (2 years 3 months 4 days 8 hours ago) and read 3765 times:

Quoting smartt1982 (Reply 10):
My understanding is that if I firewalled the levers all I would ever get is the RATED thrust as per the EEC limit that you described.

For almost all engines, yes. The 737NG is the slight oddball (it goes to rated thrust for the model, rather than rated thrust for that engine).

Quoting smartt1982 (Reply 10):
In regards to the EEC in ALT mode, there is lots of restrictions, what would happen if I walled the levers then, what thrust could I get?

You'll get close to the rated...it could be slightly over or slightly under depending on the exact engine condition and environment at the time.

Quoting smartt1982 (Reply 10):
If it gives me more than the RATED, is this really a problem, surely the engine has been certified for it.

The engine is certified for it (all engines are physically capable of producing more than rated thrust). Where you can get into trouble is that the *airplane* may not be certified for it. Higher than expected thrust at low weight/speed puts you in danger of dropping below Vmcg/Vmca.

Quoting smartt1982 (Reply 10):
Is it not like chipping your car to be able to go faster?

Pretty much, yes.

Tom.


User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 12, posted (2 years 3 months 3 days 20 hours ago) and read 3672 times:

Quoting tdscanuck (Reply 11):
For almost all engines, yes. The 737NG is the slight oddball (it goes to rated thrust for the model, rather than rated thrust for that engine).

On other aircraft models (not just 737NG) if you firewalled could you get the max rating for the engine as opposed to the max rating for the model ie 7B26 and firewalled all you get is 26K but on other engines you get the max rating that the engine could ever do?

On our peformance Manuals, it depicts 7B26, if the airline ever decided it wanted to change to 27K, would this simply be a change in the EEC mod? or is there a lot more to this.

So basically this CFM567B26 that we have could actually do 27K but we have limited it to 26K (rated) for our purposes but the most we would ever get out of it especally if the EEC was not correcting is 26K because that is its rated thrust? (for this model)

More changes would need to be done to get at 27K (what the engine can be rated to but on this occasion is max rated is 26K)


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6858 posts, RR: 75
Reply 13, posted (2 years 3 months 3 days 15 hours ago) and read 3619 times:

Quoting tdscanuck (Reply 9):
The 737NG is an oddball in that it can go to the highest rated thrust for the model, rather than just the engine. Physically, they're all the same.

Not the oddball... NG and 320 family (and also 340), have the same thing.
That CFM56-5B with 33K lbs thrust rating on the 321, is basically the same as the one you use on the 319 with -5B engines.



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 14, posted (2 years 3 months 3 days 11 hours ago) and read 3561 times:

Quoting smartt1982 (Reply 12):
On other aircraft models (not just 737NG) if you firewalled could you get the max rating for the engine as opposed to the max rating for the model ie 7B26 and firewalled all you get is 26K but on other engines you get the max rating that the engine could ever do?

On most other aircraft, firewalling the throttles will give you that engine's rated thrust (the rating it actually has, not the maximum that type of engine can be rated for).

Quoting smartt1982 (Reply 12):
On our peformance Manuals, it depicts 7B26, if the airline ever decided it wanted to change to 27K, would this simply be a change in the EEC mod? or is there a lot more to this.

You would change the EEC programming plug (a simple part swap), load a new FMC database (simple software load), and change out the paper manuals. It's easy to do.

Quoting smartt1982 (Reply 12):
So basically this CFM567B26 that we have could actually do 27K but we have limited it to 26K (rated) for our purposes but the most we would ever get out of it especally if the EEC was not correcting is 26K because that is its rated thrust? (for this model)

Your CFM56-7B26 is capable of 27k (more, actually, but that's all its certified for). It's rated for 26k. If you push the TO/GA switches it will go to 26k. If you physically push the throttles all the way forward it will go to 27k.

Quoting mandala499 (Reply 13):
Not the oddball... NG and 320 family (and also 340), have the same thing.
That CFM56-5B with 33K lbs thrust rating on the 321, is basically the same as the one you use on the 319 with -5B engines.

I didn't think the A319 could have the 33k rating, are you positive about that?

Tom.


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