Which CFM56-7B engines ratings are actually simulated for the NGX fleet?

 

CFM56-7B22/24/26/27? or all

 

Just curious

 

Thijmen

Not sure, however, the CFM56-7b can be had with thrust ratings ranging from 18,500 to 27,300 lbs. The 737-700's I work on sport a thrust rating of around 24,000 lbs, while the 800's in our fleet are closer to 26,000. I suspect that's probably in the ballpark of what PMDG used when modeling the NGX. Just a guess though. Regards

PMDG have modelled the most common engine types for each of 737. -800 and -900 have 26k, -700 have 24k, -600 - 22k and -900ER will have 27k.

What I see is that the most common engine type for the 737-800 SFP, at least for Gol fleet is the CFM56-7B27, which has 27,300 lbf: https://www.planespotters.net/airline/GOL-Transportes-Aereos

BTW, does anyone know what is the "bump" thrust of this CFM56-7B27 and when is the "bump thrust" used?

At American we have the CFM56-7 engines with 26K normal with derates to 24K and 22K and the bump is 27K.

At American we have the CFM56-7 engines with 26K normal with derates to 24K and 22K and the bump is 27K.

All American Airlines 737-800 I have seen in this site have CFM56-7B24E engines, which are 24k: https://www.planespotters.net/production-list/search?fleet=American-Airlines&manufacturer=Boeing&subtype=737-800&p=4

All American Airlines 737-800 I have seen in this site have CFM56-7B24E engines, which are 24k: https://www.planespotters.net/production-list/search?fleet=American-Airlines&manufacturer=Boeing&subtype=737-800&p=4

Tom's not guessing. 

Hi,

I'd like just add that the engines are basically the same all could deliver 27.300 lbs rated static thr. the difference settings are obtained by FADEC settings (less thrust=less N1%).

 

Best

 

Andrea Buono

Hi,

I'd like just add that the engines are basically the same all could deliver 27.300 lbs rated static thr. the difference settings are obtained by FADEC settings (less thrust=less N1%).

 

Best

 

Andrea Buono

So, is the "bump thrust" of the CFM56-7B27 27,300 lbf?

*

Will an assumed temperature of 50 C on take off (in the same air conditions, of course) generate the same thrust in a CFM56-7B26 and in a CFM56-7B27?

 

So, is the "bump thrust" of the CFM56-7B27 27,300 lbf?

No, 27,300 lbf is the rated thrust of the -7B27 engine. I don't think there is a bump thrust rating for the -7B27 engine.

 

Will an assumed temperature of 50 C on take off (in the same air conditions, of course) generate the same thrust in a CFM56-7B26 and in a CFM56-7B27?

 

It will generate different thrust, because the full rated thrust it is based on is different.

"Will an assumed temperature of 50 C on take off (in the same air conditions, of course) generate the same thrust in a CFM56-7B26 and in a CFM56-7B27?"

 

Hi Teo,

as Kevinh has said it'll generate a different thrust being "flat rated and de-rated" with a different takeoff static rated thrust:  you can check by yourself:

 

if you take a B737-800 (pmdg is based on a 26k engine) and set rated thrust at 15°C sea level and 1013 mbar (ISA) you got a "design point" giving : 97,9-98,0 n1% ("corrected" N1% ), EGT = about 722°C (margin between max EGT=950°C = 950-722=228°C) ;

 

If you now press the "TO BUMP" (now the engine delivers 27K) you got the "design point" for the 27K version of the engine: 100,5N1%, EGT=783°C

 

Now I can summarize what would happens at different outside temperature (15°, 30° and 50°)

 

                             26K version                                                                  27K version

 

15°C     N1=98,0 egt= 772°  ( egt margin=228°)                N1=100,5%  EGT=783° (margin=167°C)

 

30°C    N1=100,3,egt=822° (margin=128°)                      N1=102,6% EGT=830° (margin=120°)

 

50°C   N1=97,2%,egt=857 (margin=93°)                         N1=98,7% EGT=864°  (margin=86°)

So as you can see till 30° (flat rating temperature point) thrust can be mantained constant by increasing n1% (but reamin different being different the rated thrust)

By increasing the temperature thrust is being reduced because in spite off EGT increases N1 is lower (otherwise you overpass EGT limits because if outside air temp is higher you need a turbine inlet temp higher to develop the same N1% speed) but thrust remains different (97,2% n1 vs 98,7% )

Anyway at higher altitude where turbine inlet temp is not the most important limits (because total air temperature at the intake of the engine decreases) the continous thrust of different rated engines should be almot equal being based on the 104% max N1 limit (all the engines should reach a max 104% N1 but I can't remember)

 

Ciao

Andrea Buono

What I see is that the most common engine type for the 737-800 SFP, at least for Gol fleet is the CFM56-7B27, which has 27,300 lbf: https://www.planespotters.net/airline/GOL-Transportes-Aereos

BTW, does anyone know what is the "bump" thrust of this CFM56-7B27 and when is the "bump thrust" used?

Bump thrust is used to get you off short runways with a heavy load. We use it sometimes in the -800 to get us off of Maui. It is not selectable on the N1 page. The only way to get it is through our ACARS takeoff uplink.

 

Jack Colwill

Gol operates CFM56-7B27 in it's 737-800 SFP fleet. Where do I find performance tables (take off field length etc) for this type of engine? 

PMDG not simulating the different ratings (except as a derate/bump) is probably the biggest downside of the NGX from my perspective.