787 fuel burn, GEnx and how it relates to LEAP-1B

787 fuel burn: Aviation Week has this story about the early fuel burn results for the Boeing 787 beating expectations (which admittedly were tamped down because of the program difficulties). Some of this has been reported before. What caught our eye was the detail about the GEnx engine. Why? Because the CFM LEAP-1B derives much of its technology from the GEnx, including the higher temperatures fleetingly referenced in the AvWeek piece.

CFM is relying on high temperatures to achieve the fuel burn required by Boeing’s 737 MAX. This is hotly debated (pun intended) between CFM and Pratt & Whitney in the competition between the LEAP and the PW GTF.

CFM advocates that its hotter-running engine, equipped with advanced technology ceramics and other advanced materials, gives it the advantage over PW’s Geared Turbo Fan technology. PW argues that the hotter CFM engine will require more maintenance. Engineers that we ask generally agree that the hotter temperature approach will be a challenge for long-term maintenance but fall back on CFM’s sterling reputation of reliability as a measure of comfort. At the same time, these same engineers–who have no connection to either CFM or PW–like the GTF technology but want to see it proved in service.

Steven Udvar-Hazy said it best. It will be five to seven years after the engines are in service before the industry knows the reliability and performance of either engine’s advanced technology.

30 Comments on “787 fuel burn, GEnx and how it relates to LEAP-1B

  1. Well, GE is slightly ahead of schedule for the PIP-1 and PIP-2 versions of the GEnx-1B/-2B engines. With the Leap-1B engine sharing some of that developed technology from the GEnx engine, coupled with the reputation of CFMI, I wouldn’t be surprised if the Leap-1B engine has a lower SFC than the Leap-1A/-1C or PW-1500 series engines.

    • Well, don’t have too much hope, the technology level of the GEnx will not change dramatically with the PIP’s. What is being done is that the system is fine tuned as more is learned about the system (and its shortcomings). Actually they even moved back in tech once on the LPT as the cutting edge tech they introduced did not work as exected, so they went back to a more classic design.

      I would not expect any major (or minor) new technologies to be introduced in the PIP’s. A few things perhaps, but the overall architecture has been set for many years now (2005?) and will not change until a new derivative is made (compare GE90-94B –> -115B).

      When the LEAP’s are designed, you start with that system at a certain level (which might be higher than the GEnx’s though) and will down the line have the same system knowledge and opportunity to tweak it. Overall experience from the GEnx will of course be used for LEAP, but this won’t necessarily be dependant on PIP’s.

      I would not expect the -1B to be vastly superior per unit thrust than the -1A. If so, CFM would not sell many -1A’s on the NEO and that they cannot afford…

  2. The world is filled with great technologies that were not reliable or didn’t pan out. I really like the GTF but Turboprop gearboxes have historically had significantly shorter lives than the turbine itself. Also, the introduction of new materials and being hotter also has risks for reliability. We do need to wait 5 to 7 years to really know. Accelerated testing only provides so much of the answer.

    Sometimes there are positive surprises, I do not think anyone expected the GE-90 to reach the performance levels it has achieved.

    • So far the GTF’s reliability has been clearly established. If not proven. It is in fact so reliable that the engineers worry that it could possibly have been over-designed.

      The invention of the twin-spool engine gave P&W an early lead in commercial aircraft jet engines. But unfortunately they rested of the laurels of their glorious past (like Boeing) and they fell flat on their face.

      But life gave them a second chance with the GTF and they did not miss the opportunity (like Boeing unfortunately is about to do with the NSA).

      • You will pardon me if I wait for actual in service reliability numbers before I sing the praises of the GTF. Pratt’s last attempt was similarly praised (PW6000) right up to the point it was nearly 4 years delayed. Reduction gears are tricky things, and I prefer to wait for actual data, rather than marketing promises.

  3. Because of the unknown maintenance issues involved with new engine technology, will the engine makers provide some warranties or maintenance standards that will provide some level of protection for the purchasers . Given no track record, there must be some provisions made for representations for usage and durability.

    Do the carriers usually contract separately with the engine makers so that they look to GE or Pratt and Whitney when issues over propulsion arise or do they look to the manufacturer who in turn look to the engine maker. It seems like there are both separate issues as well as overlapping ones.

    Any clarity on the issues that surround the ongoing responsibilities and maintenance requirements would be interesting

  4. Temperatures are relative to their respective engine’s application. As such, it’s hard to make relevant comparisons between engines designed for very different end use. Per CFM, the LEAP-1A/LEAP-1B core operates with considerably lower T3 and T41 temperatures than either the GE90 or GEnx.

    • CM, on what basis do you make comparisons between various engine options that are relevant and influence one choice over another.

      Also, aren’t all these engines designed for the same end use : their role is ultimately to be affixed to the wings of a plane and to provide thrust and power to the aircraft.

      Please elaborate if your comment is misunderstood

      • NB engines run many more power cycles than those used for long distance flights attached to Widebodies.
        apropos GE90:
        didn’t the GE90 upgrades essentially trade in significant noise and pollutant emissions ( and a bit of lifetime) for the efficiency gained?

      • You are correct; at a fundamental level, all engines are designed to create thrust. UWE has noted the distinction I cryptically was referring to: It’s the high-cycle nature of the single-aisle aircraft compapred to the long cruise segments we see for a GE90 or GEnx. Engines see their highest temps at takeoff. If you tried to combine the temps of the GEnx with the cycles of a CFM56, you would need some very robust materials and clever cooling to make that work.

      • Essentially NB and WB engines should not be measured for comparative purposes. As CM just posted, the different thrust and cycle requirements place them in a different
        engine category.

        Now by comparing “apples with apples” it is easier to measure those qualities that form the basis for comparison.

  5. There is an interesting interview in the new ISTAT “Jetrader” magazine July/August 2012 issue on the 73MAX with Joe Ozimek, who transferred from Boeing Capital to 73MAX program customer marketing leader.

    Sorry, I don’t see a link, but maybe Scott can assist. You may be able to find it via http://www.istat.org.

    A lot of it is marketing hype as you would expect, but Joe is a canny old aerodynamicist and usually doesn’t wander too far from the truth.
    Two very interesting points.
    1. The LEAP 1B core is smaller than the LEAP 1A core.
    2. The 8″ nose gear extension does not sit the aircraft on its tail, in fact it “levels” the aircraft which before sat tail 16″ higher than nose.
    But what is most telling to me is the absence of any comment on the pylons. Not one word, and yet earlier reports say the pylons place the engines forward and higher relative to today. This is very delicate territory, and I have yet to see even a stetch of the proposed design.

    Also, in the same issue Stu Hatcher has an article that will perhaps answer some of the questions here about engine manufacturer guarantees and power by the hour agreements.

  6. Uwe :
    787 fuel burn numbers:
    Any opinions on Mr. Zeke’s comment/translation on a.net?

    Zeke is the textbook definition of wasted talent. He is obviously a brilliant person, but is so agenda-driven I cannot believe anything he says about either manufacturer. There is frequently great deception in his posts and this is one of those cases.

    ANA clearly stated the fuel burn comparison was done on their “international routes” compared to how a 767 would have performed on those routes. Because ANA never flew the 767 into FRA, Zeke determined the only comparison being made was the ICN and PEK routes, which are flown with very high density 787s. If this were the comparison ANA were making, as Zeke notes, then ANA would be conceding the 787 actually burns more fuel per seat than the 767-300ER. Everyone with a shred of technical understanding of airplanes knows this is not going to be the reality for the 787. Everyone with a shred of business understanding about the Japanese knows ANA would not go out publicly with data celebrating such an abject failure on their part. Obviously, the 787 burning more fuel per seat than the 767 will not be the case, even for early aircraft.

    In short, Zeke has twisted the ANA data and misrepresented their statements in order to wage his own PR campaign against the 787. Sadly, he is doing so with statements displaced so far from reality it has turned him into a a very polarizing (and in my view discredited) figure on a.net.

    • I am not familiar with Mr. Zeke. Do you know what his motives could be? Or on what agenda he is?

      • Zeke claims to be an A340 pilot for Cathay Pacific. He has amazing breadth of knowledge, including access to inside information from both manufacturers. If he is a CZ pilot, he is likely nvolved or somehow has access to CX evaluation data. He claims to have previously worked for Boeing, but has never explained in what capacity. He says he lost his respect for Boeing after working there. Today, he has overt disdain and hostility for all things Boeing and a very rosy view of all things Airbus. Famously, he argued for years on a.net that CX data showed the A340 to be more fuel efficient than the 777. He has never conceded the point, despite the world coming to a different view. He is always on point with Airbus’ latest marketing messages, which sometimes makes me wonder about his story of being a CX pilot.

    • I am less interested in the dissemination of someones character ( right or wrong )
      but in a dependable translation providing a second source.
      Contrary to your assurance the interpretation in accessible media seems to be not quite right. Allegations of agenda are a double edged thing.

  7. CM :
    Today, he has overt disdain and hostility for all things Boeing and a very rosy view of all things Airbus.

    I have seen many websites that are overtly pro Boeing/anti Airbus. But I have never seen the opposite pro Arbus/anti Boeing before. Except our own Uwe of course. 😉

    • Since the comments were closed in the other thread, let me just say that I was being facetious when I challenged you to a duel earlier, Normand, in case there was any doubt. I don’t actually want to fight someone over the reputation of an airplane company. So, sorry. :/

      • I expected some flack because I was being consciously provocative. I felt the need to make a statement about what I perceive as an insidious form of hyperbolic language that seems to come with each new project at Boeing. The Sonic Cruiser, the Dreamliner and the MAX are representative examples of that.

        But you were correct to point out that it was outrageous auxesis.

  8. From observing and critiquing, in my mind there are certain people that seem to have agendas and those who I feel have earned respect for their fairness and insight.
    For Boeing’s agenda: KC135Topboom
    For Airbus’ agenda: keesje, Uwe, zeke.
    For respected opinions: tdscanuck, ferpe, CM, stitch
    There are a few others on anet that seem to be thoughtful informed thinkers also…but also many fanboys. It is strange how the blogosphere brings out such passionate opinions that seem to exist only to feed the personality traits of the bloggers themselves!

    In any event, I would presume that as the 787 design and production is fine tuned, it will show continous improvement just as both A and B have done with every model. PIP packages and evolution of models always seem to occur over time until the program reaches the end of its life cycle (eg. 767, 340). Perhaps the MAX is the end of the line for the 737…but there does not seem to be any insurmountable obstacle for it to achieve its targets and compete effectively with the NEO.
    Although the production and industrialization of the 787 has been awful, the innate design seems to be good and I would expect it to continue to improve. Just as the 380 will continue to be improved over time. Both A and B have good engineers with clever ideas…there’s a reason it’s a duopoly!

    • Mike, not really wanting to make an infringement on Scott’s Reader Comment Rules, but if Scott would excuse me; I do believe that in this case it’s warranted to point out that “Stitch”, a blogger with an astoundingly high rate of comments over at a.net, has along with many US-based users, been quick to label “Zeke” as being “anti-Boeing”. Hence it’s worth pointing out that “Stitch”, while seemingly using his real name, was a frequent contributor on the now defunct Fleetbuzzeditorial blog and on the defunct Fleetbuzz Forums. Interestingly enough, he apparently never ever labeled the blog owner as being “anti-Airbus” nor did he ever label Doug McVitie and other notorious Airbus bashers for being “anti-Airbus”. Come to think of it, neither do I recall a blogger with the screen name “CM” ever label the above mentioned individuals as being “anti-Airbus”, but perhaps “CM” was never aware of the existence of “Fleetbuzz”, or that he never visited the site in the first place. ,-)

  9. OK, Everybody, it looks like I have to step in (again) and remind all that my Reader Comment Rules preclude getting into personalities and critiquing **people** as opposed to issues. All this stuff about pro-Airbus and pro-Boeing personalities might be vicarious fun for some but I won’t allow it. Get back to issues or I will close comments.


    • Sorry Sir ;0)
      Its sometimes hard to cut through the clutter to see the Big Picture…

      Do B and A build in a performance margin for their “brochure”/contract guarantees for their new aircraft programs? Conversely, do they build in bonuses if they surpass their guarantees?

  10. Mike :
    Perhaps the MAX is the end of the line for the 737…but there does not seem to be any insurmountable obstacle for it to achieve its targets and compete effectively with the NEO.

    Perhaps. I hope you are right. If not, it is the NG that would (or should) become the end of the road for the 737. But what a waste of time and money the MAX would become if it turns out the problems were insurmountable. But I recognize that the jury is still out.

    • Before things become insurmountable ( which they cerrtainly are not for the MAX ) they run into diminishing returns.
      I would still like to have a reference translation for that japanese diagram.

  11. Uwe, just playing with google translate, the data seems to be a comparison of total fuel burnt since EIS of 787 until end of April, measured on a gram per seat km basis. It also mentions that this is on international routes.

    If this translation is correct, then it would seem that the 787 data could be taken from the daily frequency from HND to FRA. So that would be from a 5000 nm sector. The ANA 767-300ER operates regional international destinations. The furthest it flies is Haneda Honolulu, about 3300 nm. Average sector this year is 1800 nm.

    Another possibility is that they are comparing HNDPEK, which has been operated briefly by the 787 back in January, and is operated by the 767.

    In terms of generic sizing of the aircraft, the 767-300ER is quite a bit smaller than the 787-8.

    In the ANA configurations, the 787-8 has 158 seats whilst the 767-300ER is mainly at 214 seats (35% more than the 787).

  12. To BA Investors question about engine contracts – Engines are contracted separately from airframes by the aircraft purchaser and each have their own performance guarantees.

    To add to Howard’s PW comment, Delta experienced maintenance problems on 757’s using the PW4000, which they were sold on for their better performance. Delta switched to GE engines for later orders of 757’s. And yes the cracking disks did not show up for several years…

    John Galt’s comments are right on – many times issues don’t arise until hundreds of thousands or even millions of hours have acrued on a engine (or airframe for that matter) type.

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