Boeing MAX v Airbus NEO; Fan size and optimizing the LEAP for MAX, Part 2

The war of words between Airbus and Boeing continued unabated at the Pacific Northwest Aerospace Alliance 11th Annual Conference this week in suburban Seattle.

As fully expected, Airbus said its planes are better than Boeing and Boeing said its planes are better than Airbus. No news there.

But Boeing revealed a little bit more detail on the 737 MAX vs the A320 neo that suggests their analysis gives another percentage point advantage than was originally announced last August.

When MAX was announced, Boeing claimed, “The airplane’s fuel burn is expected to be 16 percent lower than our competitor’s current offering and 4 percent lower than their future offering” and “It will have the lowest operating costs in the single-aisle segment with a 7 percent advantage over the competition.” The slide shows an additional 1% advantage for fuel burn over neo and 17% over A320CEO (Current Engine Option, as Airbus now calls it), of +5 (VS 4) and +17 (vs 16). We asked Boeing about this, and we’re told the slide reflects rounding up the numbers and not an actual increase in the previously announced economic claims.

Randy Tinseth, VP Market, showed this slide (click on the slide to enlarge), the first time we’ve seen one like it. The slide shows the improved fuel burn minus the negative impact of additional weight and drag to come up with net figures.

What is also useful is that Boeing includes in the illustration the existing and planned fan diameters for the 737-800, the A320 and their successor airplanes. The assumptions used in the analysis are also listed on the slide.

Airbus disputes the underlying Boeing analysis as well as claiming the assumptions used favor Boeing instead of real-world operating conditions. We covered the Airbus detail following ISTAT’s European Conference in Barcelona. We sought out Boeing at that time in order to include their detail in that posting; Boeing declined. Boeing held a tele-conference November 4, but it could only be characterized as a high-level look at the program. We’ve been trying for months (since last June, in fact) to follow up their briefing in advance of the Paris Air Show and Boeing has been declining all interview requests on MAX.

CFM has likewise declined interview requests (three since August, when MAX was launched). Both companies have left the marketplace in a fog. But information obtained from customers, from Boeing and from within CFM has now painted a reasonable picture of how Boeing and CFM support their claims that the 737 MAX will be more economical than neo and how the LEAP is being optimized for MAX. In addition to the Airbus position, it should also be noted that at least one airline analysis of the MAX vs neo concludes that MAX will only be around 2% better than neo, not the 7%-8% lower operating costs claimed by Boeing.

The purpose of this post is not to attempt an independent analysis, but rather to explain why Boeing and CFM make the claims they do. This report is the result of months of talking with customers and sources within Boeing and CFM; and from public appearances by Boeing and CFM.

Size matters, in more ways than one

The high-profile debate between Airbus and Boeing is that the fan diameters of the Pratt & Whitney GTF and CFM LEAP-1A on the A320neo are significantly larger than the fan diameter on the 737 MAX, and therefore the Airbus will be more economical than the MAX–or so says Airbus and PW.

The fan diameters are identified in the Boeing slide above.

CFM and Boeing say, not so fast. These companies have been very public saying fan size doesn’t matter for the LEAP-1B, although it is 10 inches smaller than the LEAP-1A and 13 inches smaller than the PW GTF. Optimizing the 1B for the 737, coupled with what Boeing and CFM say are inherent advantages of the 737 over the A320, offset the fan debate, they say.

Boeing has previously proffered the argument that the lighter 737-800 (11% lighter, according to Boeing) gives the MAX a similar advantage over the neo. Although Boeing has not revealed publicly any Empty Weight or related data, customers tell us the data they’ve seen suggests the MAX target is about 5,000-6,000 lbs more than the current NG. One customer tells us, however, that Boeing–as recently as December–may be closer to 10,000-12,000 pounds heavier than the NG.

It is important to note that at this stage of design development, we don’t consider the higher figure–if accurate–is particularly significant. Boeing doesn’t expect design freeze until next year and we believe the weight will continue to be a moving target as design freeze approaches.

Customers tell us Boeing is targeting additional range on the -8 MAX of about 360 more miles. (We neglected to clarify if this is NM or Statute miles.)

CFM tells us the 737’s lighter weight is the “secret” in this entire debate, albeit it’s hardly a state secret. Because Boeing has the lighter airplane, Boeing (and CFM) point out that lower thrust is needed.

“Fan size is correlated to thrust, ” CFM tells us. A lighter engine also contributes to the ability to proceed with a smaller fan, CFM tells us.

In a simple (and perhaps simplistic) analogy, CFM compared the lighter-weight 737 and lighter-weight, smaller engine to automobiles. A full-size car requires a larger engine than a smaller car with a smaller engine, and overall fuel mileage may be similar. (Our example: A full size Nissan Maxima, with a six cylinder engine, is about as fuel efficient as the smaller Nissan Altima with a four cylinder engine.)

Airbus adamantly believes that the addition of sharklets on the A320 family gives it the edge in the re-engine race, because Boeing already has winglets and can’t gain any more. Airbus disputes the underlying Boeing assumptions of economics of A320CEO vs 737NG, from which all other forecasts flow.

CFM made a further comparison on fan size to us, comparing the GEnx on the Boeing 787, which has a larger fan size than the GEnx version on the Boeing 747-8. While to a large degree, this may be comparing apples and oranges because the airplanes and their missions are so different, the point is GE optimized the two engines for the two airplanes and the fan sizes are different.

Optimizing the LEAP for MAX

We wrote February 8 a short piece about some of the optimizing the 1B for MAX. CFM also says that the inclusion of exotic materials, such as ceramic-coated composites, contribute to the optimization of the 1B.

But where CFM is particularly confident in its approach is that CFM tells us the 1B is essentially a down-scaled GEnx. We were shown–but were not given–a rendering of the GEnx and 1B and to the untrained layman’s eye, the architecture is indeed very similar. Potential customers are shown this drawing. CFM says the architecture is “the same.”

It is because of this identical architecture and the test results of the development of the GEnx that gives CFM, Boeing and, generally, customers confidence that CFM will deliver what it advertises. CFM points out that the GEnx is designed to produce a 15% fuel burn improvement over the comparable wide-body engines, and since the LEAP engine shares architecture, this is why CFM promises a 15% fuel burn improvement over today’s CFM56.

It has to be pointed out, then, that four sources say, including inside Boeing and from customers, that at this stage of development, the 1B is 2%-3% short of target. Last August we asked CFM about this, and the response at that time was that the engine met the MOU specifications laid out by Boeing. CFM declined more recently to address this issue.

But as with the issue concerning the weight of the airplane, we’re not sure that at this stage, this is particularly significant. The GEnx likewise was short on SFC (by 2%-3%, as it happens) during testing, a shortfall that will be corrected with PIPs. Given that the GEnx and LEAP share architecture, it would not be surprising that LEAP would have a shortfall at the moment. Given that the first flight of the MAX is not scheduled until 2016, and the COMAC LEAP 1C and neo LEAP 1-A will precede the 1B in testing and EIS (for the 1A, anyway), there is plenty of time to deal with SFC promises.

CFM is striving to make the LEAP 1B 99.9% reliable at EIS. Modifications to the GEnx-based LEAP are necessary to achieve this. CFM tells us that wide-body engines aren’t as “durable” as narrow-body engines because of the dramatically reduced number of cycles these engines have compared with narrow-bodies. The much longer turn-times also give more time for mechanics to deal with issues on wide-body engines, whereas narrow-body turn-times may be only 30 minutes or less. This means the narrow-body engines have to be more robust.

Accordingly, while the GEnx has a 23:1 compression reduction, the LEAP has a 22:1 reduction–not much, but which CFM describes as an added safety margin for the smaller engine. The LEAP will also operate at lower temperatures compared with the GEnx.

LEAP 1B has passed Toll Gate 1, a point in the program where parties approve development, and the next Toll Gate is planned for the second quarter this year.

44 comments on “Boeing MAX v Airbus NEO; Fan size and optimizing the LEAP for MAX, Part 2

  1. Thank you
    I was waiting for this one since you announced it yesterday?
    What about the LeapX1A vs PW11XXG ?

    One more point : at this stage Airbus doesn’t need any MTOW raise for the A319 and 321NEO and a mere +1t for A320 NEO (as per docs given during the 2011 EADS Wrap up) despite +1.8 t increase in MZFW that can be traced as an OEX increase

    Thanks

  2. “We asked Boeing about this, and we’re told the slide reflects rounding up the numbers and not an actual increase in the previously announced economic claims.”

    ROFL! ( Never would have thought that my darker assumptions are actually true )
    If one would do that in every computational step any wanted result can be produced.

    “CFM points out that the GEnx is designed to produce a 15% fuel burn improvement over the comparable wide-body engines, .. ”

    should be put into perspective:
    “The GEnx improves SFC by about 15 percent, compared to the CF6, an older GE engine in the same thrust class.”
    ( via http://www.aviationtoday.com/am/categories/bga/Green-Engines_21556.html )

    Friendly goalpost moving by way of changing pedigree for the LEAP to GENX ( just for the B variant or for all derivatives? ) is another squishy tidbit.

  3. Fan size is correlated to thrust, true. But for re-engine aircraft, Fan size is mainly driven by installation constrains. Look at the CSeries, a brand new design, the engine fan will be 73 inches wide for a maximum thrust of 24k i.e. much larger fan size than the Leap-1B for a lower thrust!
    But what is important is not the fan size but the bypass ratio of the engine. High bypass ratio improves propulsion efficiency and therefore lowers fuel burn.

    • Not quite right imho ( or dependent on what facet you view from ).
      For a given thrust fan diameter determines propulsion efficiency. ( a linear relationship afaik)
      BPR is determined by how much energy you can carry in core mass flow and how good you can extract that energy. ( A Turboprop being the final iteration, no thrust from the core )
      BPR is effect and not the method.

  4. “Optimizing the 1B for the 737″

    You keep talking about optimizing for the 1B. Why wouldn’t CFM optimize the 1A?

      • It is either one family LEAP A, B, C or the Leap1B does not happen and the MAX engine will actually be a GENX4NB.

        The information you present seems to indicate that Boeing and CFM/GE would like to show the MAX engine with “other family”,
        trying to put a stop to current comparisons going by scaling effect comparisons. New set of clothes for the Tsar.

      • OK
        Did i read an understand correctly : Gen2B (1F+3LPC+10HPC+2HPT+6LPT) is shrinked into a Leap1B with same stage count ?
        So what ? the Leap1A/C has the same stage count as Genx1B ?

        Thanks

      • Well, yeah, but the LEAP 1A is related to the 1B whether CFM like it or not, and every technology that can be inserted into the 1B can be into the 1A as well.

        Not saying that they will in, they might want to protect their 100% share 737… but P&W know that the PW1133G is their big chance to get back in the game big time (PW1524 is much less so, and the PW1217 even more so) and will give it all they have.

        So can CFM afford to let the 1A behind? Unless P&W screw up, I’d say no…

    • CFM/Boeing are describing the 1B variant with so much enthusiasm that you’ll soon end up asking yourself why Airbus doesn’t change their mind and drop the 1A in favour of the 1B. They’re not absolutely obliged to use their extra room free, after all. :)

  5. Poncho :
    OK
    Did i read an understand correctly : Gen2B (1F+3LPC+10HPC+2HPT+6LPT) is shrinked into a Leap1B with same stage count ?
    So what ? the Leap1A/C has the same stage count as Genx1B ?
    Thanks

    My understanding is that the LEAP 1A/C looses one lpt stage on its way to become a LEAP 1B.
    Shared GENX DNA is then invoked for the LEAP 1B ( or the complete LEAP family ?), a bit of a cuckoo child, isn’t it ?

  6. Interestingly, looking at Randy’s slide, it looks as if the Leap-1B nacelle is much less flattened than the nacelle on the CFM56-7 engine, due apparantly to the Leap-1B engine being mounted significantly further forward and higher.

    IMO, there are at least a couple of major design challenges ahead for the MAX due the new engine overhang position.

    1.) The combination of the greater engine weight and greater overhung moment means that the pylon of the LEAP-1B will be heavier than the engine mount structure for the CFM56-7 engine, because the former obviously has to support a larger weight. On the neo, on the other hand, there is no need to significantly change the engine overhang position.

    2.) The combination of greater engine weight and a further forward powerplant centre of gravity location will move the empty centre of gravity of the aircraft further forward. To compensate for this, either the wing will have to be moved forward (which is not likely); and if not, some other heavy hardware must be moved rearward in such a way as to ensure a proper balance between the aircraft centre of gravity and the wing center of lift.

    On the 737-300, Boeing added three frames aft of the centre wing box and 2 frames forward; partly in order to rebalance the aircraft

    http://www.flightglobal.com/pdfarchive/view/1982/1982%20-%200369.html

    Finally, looking at Randy’s slide once again, he’s claiming that the MAX-8 is 11 percent more efficient than the dash 800 and that the A320neo is 12 percent more efficient than the A320ceo. Now, if we inserted Airbus’ own projected fuel burn/seat figures for the A320neo into Randy’s slide, the MAX-8 would only beat the A320neo by 2 percent; or in other words; any advantage the 737-800 may have had over the A320 in the past, would be largely nullified.

    • We caution OV-099 from drawing the conclusions he cites in his last paragraph, for the published slide is but one of 50 slides. With the continuing caveat that Airbus disputes Boeing’s figures, Randy also talked about and had a slide of the Boeing-perceived advantages of a lighter-weight airplane and the impact on total operating costs. Boeing also claims an advantage in maintenance costs vs Airbus of well into the 20% range, which is a huge number (and which Airbus also disputes).

      We again point to the unidentified airline we’ve talked two that has run its own analysis of NEO and MAX and all factors that go into total cost. This airline concludes MAX will have only a 2% all-in advantage at this carrier–not the 7% all-in cost advantage Boeing claims, nor the all-in advantage Airbus claims.

      For our money, we believe the airline more than we believe Airbus or Boeing.

      • What usage profile does that airline have?
        ( or is that giving away too much ?)

        What I find interesting is that the GTF doesn’t produce any news on its own at the moment.
        No news is good news and lots of news means there is still
        need to form oppinion.
        In that context the next interesting item you provide is the move
        to “unlink” as much as possible the MAX engine from the other LEAP derivatives.

      • Scott, the idea was to use Boeing’s own projected fuel consumption savings for the MAX and Airbus’ own projected figures for the neo and not their respective projections for each other’s products.

        Hence, inserting Airbus’ fuel saving projections for the neo into Randy’s slide, we get a delta of 2 percent. Granted, it’s a crude “analysis”, but interestingly enough, it seems to square well with the rather more eloborate analysis done by the airline that you’re talking about. :-)

    • “On the 737-300, Boeing added three frames aft of the centre wing box and 2 frames forward; partly in order to rebalance the aircraft” Looks like a good recipe for the MAX 7 to me. Increased volume for various 149 passenger layouts in a light airframe.

      Aside from engines, why is one wing better than the other in any respect?

  7. Very interesting and detailed comments, especially the last line from leehmne!

    Whatever the (small) advantage the MAX, or the NEO, has over it’s competing
    model, the market is so huge that the two companies will most likely split that
    market abut 50/50 anyway, providing Boeing gets the MAX specified and signs
    up all the “committed” airlines SOON!

  8. The Neo and Max will basicly have the same core engine. Boeing is going deep to make the fan as large as reasonable feasible on the 737.

    Airbus is offering the same engine with a 10 inch bigger, not flatened fan.

    + Airbus is adding winglets, helping it a few % extra

    + installing the engines is easier/ lighter

    Well Randy, if you can’t convince them, confuse them.

    I would like to hear CFM judgement..

  9. Why maintain the bit that GEnx was 2-3% above book sfc when a GE official pointed out 2 PIPs totalling an improvement of 2,7% in an Aviation Week article? Wouldn’t it be fair to assume that the shortfall was at least 3%?
    I don’t think you can copy the 15% improvement in SFC claimed for the GEnx-1B down to the LEAP-1B with a ‘same architecture’ analogy. Doesn’t scale like that
    Engine weight will be critical for the MAX. In that respect the LEAP-1B will have to stay closer to spec than the GEnx did.
    I’d largely go with OV-999’s analysis, except that I see a 45/45 market split for Airbus and Boeing in this segment.

    “Luke – there’s another narrowbody…”

  10. The CFM-56-5B/-7B engines on the current A-32X series and B-737NG series weigh about the same, the -5B is 5250 lbs (2380 kg) and the 7B is 5216 lbs (2370 kg). It is a given the Leap-1A/-1B engines will be heavier. But the -1B engine should be significantly lighter, based on it has 1 less LPT, shorter fan blades, shorter overall lenght, and different materials (ceramics, etc.).

    Yes, the mounting of the -1B on the B-737MAX wing will be significantly heavier than the mounting of the 1A on the A320NEO wing, maybe. Isn’t Airbus trying to use a common pylon for both the Leap-1A and the GTF engines? Both Airbus and Boeing will need strenghtening in the wings and center wing box for their installations, but Airbus must strenghten the wing all the way to the wing tip to be able to accept the blended winglets, and the bending motion they create (Boeing has already completed this).

    Boeing already also has a (relitively) modern design for mounting the engines foreward of the wing in the B-757 design (which itself grew from the B-707 design, Boeing also improved the C-17 engine mating design). So doing it, and adding the required strenght is not in question. They also have a little experience in mounting engines high on the wing, in the aborted USAF AMST program, Boeing’s entry was the YC-14.

    The issue isn’t that Boeing cannot design the MAX to meet, or exceed specs. (even though some here do question it while blindly accepting that Airbus can), I believe they can. Boeing has a more modern wing to work with from the NG to the MAX than Airbus has. Boeing (and Airbus) are constantly ‘tweaking’ the designs to sqeeze every drop of fuel comsumption improvement they can. Boeing will make some aerodynamic improvement to the wing and the airplane, in addition to the tail shape improvements already announced.

    I seem to recall Boeing will begin flight testing on a new vertical tail leading edge device on a test bed B-787 this year, with an intention of incorproating the improvement into the B-787, B-747-8, and B-737MAX. Has anyone gotten any updates on that program?

  11. An interesting scenario is a MAX that ends up as far away from the paper spec as the 787 and 747-8 did. Add a GTF that turns out a few percent better than what has been advertised so far. Add a proliferation of night curfews. Add a sharklet that is better than just 3%. Time will tell…

  12. KC135TopBoom :
    You know of course, the direct opposite is just as likely to happen at this point in time, don’t you?

    No its not. The fact is that Airbus has a much lower risk strategy than Boeing. Most likely they will roughly hit targets at EIS, but the risk for the MAX is definitely much higher.

    What I do wonder is the commitments made by CFM. The LEAP engine (both 1A and 1B) is not just a shrunk GEnx otherwise it would be old technology. Basic architecture might be the same, but stuff like ceramic coated composites are a huge jump in technology. I also can not see an easy 15% improvement on the current CFM-56-7B as this engine is very good today thanks to continuous improvements, something which has also been done on the Trent engines for the A330 but not on the GE engines replaced by the GEnx. It might hit 15%, but it is definitely not easy nor low risk. They are late relative to the GTF and will struggle to get the 1A in service on-time and on spec. The 1B engine can not be a hugely improved version of the 1A either- there just is not enough time for that and test data for the 1A will probably come too late to be used as input to make design changes.

    • The use of cermaics may actually refer to the parts that came out with pretty short life limits on the GEnx-1B, e.g. the core nozzle and plug assembly. Probably related to the increase in T that is part of the effort to get SFC closer to book.

    • Your timing comment is very true, the 1A is not enough ahead that its data can be used to improve the 1B.

      What can be done, however, is to change some things in the 1A that were not ideal but could be changed had they had more time (which they have in the 1B).

      This was the exact case in the GEnx-1B and 2B developments: no test data, but some good ideas that could not be implemented into the 1B due to time could be in the 2B.

      But some things that were optimized for the 1B (the larger engine) were not redesigned for the 2B due to time, so they came out heavier than needed for the smaller 2B. Examples are castings which typically have very long lead times. Watch these on the 1B, I suspect the same could happen again. By big bet would be on the fan frame, it being the largest (and with the biggest penalty…).

  13. Foxy Randy’s and shrewd Leahy’s charts are not directly superimposable : Randy shows a 500nm picture, where Leahy shows an 800nm picture, and the topic being compared is “TRIP fuel consumption”, not (Thrust-)Specific Fuel Consumption. Why ? Because to shorter mission engine cycle fuel computations emphasize -B1 geometry whereas those for the longer mission emphasize -A1 geometry, in particular in the descent/approach phase + taxiing (pro -B1 ?) and the cruise phase (pro -A1 ?). We should ask Airbus to re-do their chart for 500nm, and Boeing to re-do theirs for 800nm. We’ll possibly find a cross-over point (in between 500nm and 800 nm ?) where (but strictly from the mission fuel viewpoint, which is the discussion here) the advantage passes from the one to the other ?

  14. An apple to apple comparison would be best.

    Probably at one point CFM will have a slip of the tongue on their 1A/1B.

    Still there would be room for discussion however obvious the outcome is.

    Simply because a certain outcome doesn’t fit a preference & is therefor is unacceptable.

    Smart formulated half truths for willing ears will not convince the airlines anyway.

  15. Boeings assumption of type operational differentials, are currently based on a current unknown quantity even within it’s own type design, tied to an assumed & as yet unknown perspective of it’s competitors assumed design.

    Whilst operators are lured into the duopolies sales team spin, the reality is the most savvy airlines reject the initial speculative figures & see the fine detail presented for what it is.

    Given the history of the two airframes involved it’s clear the EADS offering has more tweaking potential, it’s my well judged opinion EADS has more up it’s sleeve than Boeing want’s to willingly acknowlege & EADS are letting on.

    As suggested, Oh, to have visibility of a champion operators unbiased evaluation of the two types, cuurrent numbers would seem to speak for themselves, going forward the purchase decision may be more delivery based than operational cost.

    • Given the number of engineering programs EADS/Airbus (and Boeing) has going on, I think both OEMs already have the basic design of the NEO and MAX completed. The major changes I see for both the A-32X-NEO and B-737MAX will be weight reduction, and additional strenghtening based on computer modeling and wind tunnel testing.

    • Airbus pushed out the A321 NEO. I would not be surprised if the spec isn’t frozen yet and could change considerably from the current one.

        • I doubt the design work on the A-320NEO, or the B-737MAX is frozen, yet. The NEO has only been offered for a little over 1 year now. Both OEMs have a long way to go on design work and will need input from P&W for the NEO, and CFMI for both.

  16. The rules are : we’re allowed to do comparative advertising, but if we do, then the opponent will, as well, so mind your steps ! Never tell a lie, you’ll lose your Image & Prestige, your professional credibility will go down the drain, with 100 % certainty you’ll be caught the pant on your knees. Make use of the freedom you have to select the terrain of the comparative advertising to shed favorable light onto your own product. Airbus will not say to Boeing “Uh-Uh, that’s a 500nm chart ?!” because Boeing will immediately retaliate saying “Uh-Uh, yours is an 800nm chart !?” So they keep talking two different Chinese dialects, nodding to each other in perfect mutual “win-win” understanding : let the onlookers do the translation ! We’re in a “Sporty Game” context, a terrain for Gentlemen, they use to say ? But I’d rather not be in Albaugh’s shoes : http://www.hse.gov.uk/research/rrpdf/rr674.pdf

    • My guess is the infanticide of the A350Mk1 was quite the lesson for Airbus to be set up with.
      On the other hand the Dreamliner in hindsight is the perfect project to calibrate ones “Truth versus Pravda” translator. Actually by way of the “Lessons Learnt” ppt for communications from both sides.

  17. KC135TopBoom :I doubt the design work on the A-320NEO, or the B-737MAX is frozen, yet. The NEO has only been offered for a little over 1 year now. Both OEMs have a long way to go on design work and will need input from P&W for the NEO, and CFMI for both.

    Even though I still believe the vasic designs for both is completed, they still have the detail work to accomplish.

  18. I’m sceptical regarding that slide produced by R. Tinseth and the numbers shown there.
    Presuming equal engine technology, in most cases that engine with the larger diameter is the more fuel efficient one, and also the less noisy one.
    Unfortunately the wings of the 737 are attached at a very low point in respect to its fuselage. This results in quite disadvantageous constraints regarding maximum possible engine diameter.

  19. The controversy over the 1A and 1B will most likely be settled by a statement from Airbus.
    At some stage they surely must explain why they are not using the 1B.

  20. “The controversy over the 1A and 1B will most likely be settled by a statement from Airbus.
    At some stage they surely must explain why they are not using the 1B.”

    Airbus ?! They say the -1B is plan B.

    I guess a statement by CFM, American or Norwegian or independent specialist will mean more.

      • My guess is most everyone is aware that A/B/C here is not a regular ordering tag in time or evolution.
        Nonetheless the -C (first) and -A should have come out as
        very similar. ( no idea if the additional set of “coals” added late in the offering for the -A make their way over to the -C version ?).
        What tends to be generously overlooked though is that the
        current offerings ( CFM56 -5 and -7) weigh in at indistinguishable differences.
        Extrapolating towards the LEAP weight differences will be similarly negligible. Shedding one LPT stage will show up in the low single digits percentwise.

        Introducing GENX genetics is an attempt to defocus the discussion.

  21. leehamnet :
    We caution OV-099 from drawing the conclusions he cites in his last paragraph, for the published slide is but one of 50 slides. With the continuing caveat that Airbus disputes Boeing’s figures, Randy also talked about and had a slide of the Boeing-perceived advantages of a lighter-weight airplane and the impact on total operating costs. Boeing also claims an advantage in maintenance costs vs Airbus of well into the 20% range, which is a huge number (and which Airbus also disputes).
    We again point to the unidentified airline we’ve talked two that has run its own analysis of NEO and MAX and all factors that go into total cost. This airline concludes MAX will have only a 2% all-in advantage at this carrier–not the 7% all-in cost advantage Boeing claims, nor the all-in advantage Airbus claims.
    For our money, we believe the airline more than we believe Airbus or Boeing.

    Likewise I would caution against relying too much on any one airline’s analysis. Just as illustrated elsewhere in these comments that there is a difference in a 500 NM analysis and an 800 NM analysis, airlines route structures and economics vary so widely one airline’s analysis may be very different from anothers.
    That’s why appraisers had such difficulty in “value in use” methodology to deduce aircraft value; until lessors came along with more or less comparable lease rates, the airlines’ cost structure just varied too much.

    • Hi Fred,

      Thanks for commenting. What we like about Airbus using 800nm for its studies rather than 500nm as used by Boeing is that within the US, 800nm is actually closer to standard 737/A320 stage length by far than 500nm. This according to an analysis of the DOT data, as provided by AirInsight’s Addison Schonland.

  22. For now I take the .5% sfc improvement per inch extra fan cross section as a guideline, within reasonable margins.

    5% better sfc for a 10 inch bigger fan.

  23. I have been wondering a bit about the recent recourse to GENX in the information snippets released.
    For one I think it was introduced to defocus and put a stop to “scaled” comparisons.

    But why introduce more mature design “DNA” from the existing GENX into the LEAP line?
    Is this an indication that the MAX LEAP will be more conservative than expected by onlookers? ( But cloaked as value add )
    The LEAP(X) was introduced as hugging the thermal effciency frontline while the GTF scoots of in a tangent towards the propulsive side of gains.

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