Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
767 RR Vs PW/GE Fuel Burn  
User currently offlineAngelairways From United Kingdom, joined Nov 1999, 502 posts, RR: 0
Posted (7 years 3 months 3 weeks 2 days 4 hours ago) and read 9830 times:

HI

I was looking at the SFC for an RB211-524H and it is around 0.58. Meanwhile the PW4060 and CF6-80C2 are in the 0.35 region.

I am perplexed at why the RB211 has a much higher SFC, and how this affects overall Aircraft fuel burn on a 767. I know SFC for an engine and Fuel Burn for an aircraft do not quite correlate directly.

Can anyone help??

7 replies: All unread, jump to last
 
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 1, posted (7 years 3 months 3 weeks 2 days 4 hours ago) and read 9813 times:

I don't know what your source is, but the last time I looked at a spec sheet comparing various engine performances, those are exactly the numbers I saw. But look closely; on mine, there's a superscript "2" next to all of RR's SFCs, and a scroll to the bottom indicates that RR's numbers reflect SFC at cruise power, where everyone else's reflects SFC at maximum power. That likely accounts for the difference, as I doubt the RB211 actaully has nearly double the SFC of its competitors.


Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineZeke From Hong Kong, joined Dec 2006, 9229 posts, RR: 76
Reply 2, posted (7 years 3 months 3 weeks 2 days 3 hours ago) and read 9807 times:

Quoting Angelairways (Thread starter):
Can anyone help??

The problem is you are comparing the cruise TSFC of one engine to the takeoff TSFC of another, most high bypass engine around at the moment have a TSFC of 0.3-0.4 at takeoff, and 0.5-0.6 in cruise.

During takeoff the thrust being produced is higher, so even with a lower TSFC than cruise, the amount of fuel being consumed is greater.

When comparing engines, you also need to take into account the mass of the engine, the speed and altitude of the aircraft as this will effect the efficiency of the engine.

RB211-524H-T - TSFC is closer to 0.56 in cruise, generating 11,813 lb thrust at 35,000 ft, M0.80
PW4060 - TSFC is closer to 0.58 in cruise, generating 12,000 lb thrust at 35,000 ft, M0.80
CF6-80C2B6 - TSFC is closer to 0.564 in cruise , generating 12,000 lb thrust at 35,000 ft, M0.80

RB211-524H-T - TSFC is closer to 0.35 at takeoff
PW4060 - TSFC is closer to 0.365 at takeoff
CF6-80C2B6 - TSFC is closer to 0.348 at takeoff

RB211-524H-T - dry weight 9,470 lb
PW4060 - dry weight 9,213 lb
CF6-80C2B6 - dry weight 9,670 lb

The RB211-524H-T (60,600 lb), PW4060 (60,000 lb), and CF6-80C2B6 (60,800 lb) are all 60 klb engines used on the 763ER.

Looking at the numbers above the CF6 and RB211 are fairly close, with PW having the to carry about an extra 900 lb for the engines alone over a CF6, and more fuel efficient.

The part of the equation that we do not know, is the purchase price and maintenance costs for the engines. With jet fuel today at 2.055 US$/US gal (todays quote from IATA) it would still be possible to put a pair of PW power plants on a 763ER and still come out with a overall lower cost of ownership over the lower fuel burning competitors.

[Edited 2007-08-31 19:14:42]


We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 3, posted (7 years 3 months 3 weeks 1 day 16 hours ago) and read 9701 times:

Quoting Angelairways (Thread starter):
I am perplexed at why the RB211 has a much higher SFC, and how this affects overall Aircraft fuel burn on a 767. I know SFC for an engine and Fuel Burn for an aircraft do not quite correlate directly.

The best thing is that you are actually perplexed and seeking an explanation for the discrepancy. A certain member that spams on A'net posts such numbers as "fact", despite the SFC's being at two completely different phases of flight.

Quoting Zeke (Reply 2):
RB211-524H-T - TSFC is closer to 0.56 in cruise, generating 11,813 lb thrust at 35,000 ft, M0.80
PW4060 - TSFC is closer to 0.58 in cruise, generating 12,000 lb thrust at 35,000 ft, M0.80
CF6-80C2B6 - TSFC is closer to 0.564 in cruise , generating 12,000 lb thrust at 35,000 ft, M0.80

RB211-524H-T - TSFC is closer to 0.35 at takeoff
PW4060 - TSFC is closer to 0.365 at takeoff
CF6-80C2B6 - TSFC is closer to 0.348 at takeoff

I always knew that the RR was much closer to the GE and P&W despite the vain efforts of a certain A'net troll!

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 4, posted (7 years 3 months 3 weeks 1 day 10 hours ago) and read 9676 times:

Quoting Zeke (Reply 2):
The problem is you are comparing the cruise TSFC of one engine to the takeoff TSFC of another, most high bypass engine around at the moment have a TSFC of 0.3-0.4 at takeoff, and 0.5-0.6 in cruise.



Quoting Zeke (Reply 2):
Looking at the numbers above the CF6 and RB211 are fairly close, with PW having the to carry about an extra 900 lb for the engines alone over a CF6, and more fuel efficient.

Great post Zeke, but is the para about weights correct? On your data, I would have thought the PW was carrying less weight rather than more?????


User currently offlineZeke From Hong Kong, joined Dec 2006, 9229 posts, RR: 76
Reply 5, posted (7 years 3 months 3 weeks 1 day 10 hours ago) and read 9668 times:

Quoting Baroque (Reply 4):
I would have thought the PW was carrying less weight rather than more?????

Just had a look at the TCDS for the PW4060, it is actually heavier than my other reference indicated it is 9,420 lb, CF6 is the same, cannot check the RB211 TCDS as RR being UK certified includes more into their empty engine mass than the FAA (the TCDS says 12,540 lb).



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4069 posts, RR: 33
Reply 6, posted (7 years 3 months 3 weeks 1 day 9 hours ago) and read 9662 times:

Quoting Zeke (Reply 5):
cannot check the RB211 TCDS as RR being UK certified includes more into their empty engine mass than the FAA (the TCDS says 12,540 lb).

Remember that the RB211-524 includes the thrust reverser in the basic engine. There are no C ducts on an RB211.


User currently offlineAngelairways From United Kingdom, joined Nov 1999, 502 posts, RR: 0
Reply 7, posted (7 years 3 months 3 weeks 1 day 3 hours ago) and read 9635 times:

Thanks everyone for the replies

I knew that there's something fishy about the figures I saw published (shock horror they were in a PW booklet  Smile) in that it wasn't an "apples with apples" comparison.

Much more clear now. Thanks again.


Top Of Page
Forum Index

Reply To This Topic 767 RR Vs PW/GE Fuel Burn
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
BAe 146/ RJ Vs 737 Classic Which Burn More Fuel? posted Tue Jan 2 2007 00:04:00 by 747400sp
767 Fuel Burn Rates posted Tue May 30 2006 17:18:59 by DAYflyer
737-700W Vs A319 Fuel Burn Differences posted Sun Feb 12 2006 18:10:22 by Rsbj
Fuel Burn Delta A340-500 Vs. 777-200LR posted Mon Feb 6 2006 16:21:33 by UAL747-600
Garrett Vs Allied Signal APU Fuel Burn posted Thu Mar 17 2005 12:52:46 by MaerskMech
SFC Vs Raw Fuel Burn posted Sat Oct 30 2004 15:03:09 by Hugh3306
RR Triple Spool Vs. PW Gearbox posted Sat Mar 27 2004 20:48:07 by Splitzer
Fuel Burn - How They Stack Up posted Sat Aug 4 2007 08:56:38 by WingedMigrator
A340-300 Vs. A330-300 Fuel Consumption posted Fri Jun 1 2007 03:33:46 by CPHGuard
Fuel Burn Statistics posted Mon Jan 8 2007 16:54:04 by Cba

Sponsor Message:
Printer friendly format