70″ Fan for the 737 MAX

We picked up information that Boeing’s announcement at ISTAT in March that it had settled on a 68.4 inch fan for the 737 MAX LEAP-1B wasn’t a done deal. Now Buckingham Research comes out of Tuesday’s Boeing’s investors’ day with this notation:

A 70” fan for the 737MAX

BA noted that 737MAX development is proceeding on schedule with firm configuration expected in 2013 and first flight in 2016. Further, BA sees more upside than downside risk to the plane’s 13% efficiency improvement. BA is now looking at a slightly larger 70” fan for the LEAP-X engine vs. 68.4″ previously.  While that might reinforce investor concerns regarding the GE LEAP-X engine performance, we see the change as part of the design optimization process. A number of factors impact engine fan size, including drag (larger engine fans have more drag), bypass ratio, core size, core temperature, etc. With the 737MAX recently undergoing wind tunnel testing, we think the revised engine fan size has more to do with optimizing the engine than a means to overcome performance deficiencies. 

Note that this is not speculation on Buckingham’s part; it cites Boeing as the source.

64 Comments on “70″ Fan for the 737 MAX

  1. Well, if Boeing is still considering adding another 1.6″ to the fan section of the Leap-1B engine for the B-737MAX, then CFMI must still be on-board with several different fan sizes. The MAX is still an evolving design.

  2. I also attended this event where a Boeing representative confirmed to me that he thought it likely they might go to the 70in fan for the -1B. It does throw up a question though. Boeing shows a fuel burn bucket chart including drag, weight, noise fan size and other trade-off factors involved in the fan-size decision. The chart seems to indicate that their fuel efficiency will decrease or at least not improve if they chose a larger fan. So, either we’re not getting “the whole truth” from Boeing at the moment or, the optimisation bucket chart is flawed.

    • Perhaps it has more to do with the maintenance of the engine itself being better with lower fan speed (lower temp in the combustion chamber) Also, noise factor is also probably somewhat less

  3. Wouldn’t a 70″ fan diameter require more extensive (and more expensive) landing gear modifications? I was under the impression that 68.4″ was the maximum they could squeeze in.

    But this “looking at” a different fan diameter at this stage implies to me that Boeing is nowhere near to being able to lock in the MAX specifications at this point (and thus to be able to convert all those commitments into firm orders).

  4. Each fan diameter change requires a redesign of the whole engine. As long as there is no final concept of the engine, detailed design can not start. The chance for bringing forward EIS gets Zero.

  5. thysi :Wouldn’t a 70″ fan diameter require more extensive (and more expensive) landing gear modifications? I was under the impression that 68.4″ was the maximum they could squeeze in.
    But this “looking at” a different fan diameter at this stage implies to me that Boeing is nowhere near to being able to lock in the MAX specifications at this point (and thus to be able to convert all those commitments into firm orders).

    This may be linked with the blister on the last rendering released by Boeing

    • CBL :

      thysi :Wouldn’t a 70″ fan diameter require more extensive (and more expensive) landing gear modifications? I was under the impression that 68.4″ was the maximum they could squeeze in.
      But this “looking at” a different fan diameter at this stage implies to me that Boeing is nowhere near to being able to lock in the MAX specifications at this point (and thus to be able to convert all those commitments into firm orders).

      This may be linked with the blister on the last rendering released by Boeing

      I assume they can do 70″ without changing the main landing gear? How much extra height do they need for the nose landing gear (beyond the 8″ already planned) to handle the extra 1.6″ of fan diameter (ie 0.8″ of fan radius)?

      • An additional 1.6″ of clearance at the engine lowest point, everything else remaining equal, would translate to approximately 6″ of extension at the NLG, over and above the current 8″ that has already been factored in for the 68.4″ fan. The ratio of efficiency being roughly 4 to 1 for this particular relation.

        If our assumptions are correct this would mean that a 70″ fan would require a total of 14″ of extension of the current NLG of the 737NG.

        • No, the 1.6″ increase is in the fan section diameter, so only half that amount (0.8″) is under the engine. Boeing does not have to increase the lift on the NLG because the 68.4″ fan gave a 19″ clearence on the -8MAX and -9MAX models, and you only need an 18″ clearance.

      • You are absolutely right about the 0.8″ under the engine KC. It is easy to forget that the ground clearance is affected by the radius of the fan, not the total diameter.

        That’s why it is safer for this kind of comment to always write “If our assumptions are correct…” before saying something that could turn out to be based on a false premise.

      • beyond cost there is another limitation on gear elongation:
        The 737 would/could loose the “no slides required” for the overwing emergency exits.

        • You have a very good point Uwe. On the Embraer E-Jets, in order to keep the wing below the maximum height allowed before an over-wing emergency slide is required, Liebherr had to design a special mechanism to keep the landing gear at a predetermined length even when the outside temperature is high.

  6. I agree with everyone of you and as I commented ever since last year, there
    is NO 737MAX program or firm commitment to the program, not even from
    ASW, until Boeing provides a specification and operating-cost guarantees!
    To come out with a 70 inch fan at this late stage, in spite of comments from
    Boeing that they could not go beyond 68.4 inches WITHOUT MAJOR AND
    COSTLY STRUCTURAL CHANGES, is not only disturbing, but also alarming
    info, as far as the overall status of the program is concerned!

    • You can speculate all you want but you don’t know what is happening at Boeing in terms of design. To say that increasing the fan radius by .8 of an inch is “alarming”… is simply being alarming. It is not as though Boeing can’t “squeeze” another .8 of inch into the the nose wheel height… or .4″ into the nose wheel and .4″ from the bottom of the cowling, etc, etc.

      • Joseph :
        You can speculate all you want but you don’t know what is happening at Boeing in terms of design. To say that increasing the fan radius by .8 of an inch is “alarming”… is simply being alarming. It is not as though Boeing can’t “squeeze” another .8 of inch into the the nose wheel height… or .4″ into the nose wheel and .4″ from the bottom of the cowling, etc, etc.

        It’d be 0.8″ for the main landing gear but if you are raising the nose landing gear only it’s substantially more.

        As Rudy says, the cheap changes were already in at 68.4″, I’m sure they considered shaving from the cowling for that already.

  7. the bigger the fan the bettet. every 2inch means 1% sfc improvement. Airbus goes to 78 inch with the fan and wouldn’t do it if it was a bad idea. If Boeing could that fan on the MAX, that would be the new sweatspot 😉

    • Please don’t say that the bigger the fan the better, cause that’s not always true. If that was the case, the A380 engines on the NEO would do wonders (or Pratt could make the geared engine fan much bigger for the NEO as well). Plus, why is the next iteration of the 777 being talked about with having a smaller engines than the ones on the 777-300ER?

      • “Plus, why is the next iteration of the 777 being talked about with having a smaller engines than the ones on the 777-300ER?”

        Sorry, but where did you get that idea?

        The fan diameter for the current 77W engine (the GE90-115B) is 128 inches. The fan diameter would remain the same for GE’s proposed GE9X engine for the 777-8X/9X.

        The Rolls Royce proposed engine, the RB3035, would have a fan diameter of 132.5 inches, while the GTF engine offer from Pratt would apparently also have a larger fan diameter than that of the GE90-115B.

        Source:
        http://www.flightglobal.com/blogs/flightblogger/2012/03/rolls-royce-pratt-whitney-set.html

      • I do not know what is the optimum fan size (& bpr, propulsive efficiency) for the LEAP engine. I think the line of thought Boeings 68-70 inch is close is unrealistic and IMO opportunistic. Comac, Airbus don’t use the smaller fans for a reason. Boeing obviously is sweating to realize every extra inch.

  8. thysi :
    It’d be 0.8″ for the main landing gear but if you are raising the nose landing gear only it’s substantially more.
    As Rudy says, the cheap changes were already in at 68.4″, I’m sure they considered shaving from the cowling for that already.

    To gain another 0.8″ from a combination of nose, main, cowling, mounting strut, etc. without resorting to ” MAJOR AND COSTLY STRUCTURAL CHANGES” is alarmingly far fetched.

  9. Joseph, thysi and keesje
    Did you fellows miss the words “Boeing said that they could not go beyond
    68.4 inches WITHOUT MAJOR AND COSTLY STRUCTURAL CHANGES?”
    That was last year, so in my opinion, this late admission that the 68.4 inch
    fan is not working, IS VERY ALARMING!

    • Yes, indeed, that was LAST YEAR.

      Go ahead, express concern as to how they might have squeezed out the increase but to jump to an extreme conclusion based on last year’s comment is premature.

      To imagine that since then they haven’t been able to come up with a solution that doesn’t involve “MAJOR AND COSTLY STRUCTURAL CHANGES” to deal with the 0.8″ fan radius increase is being VERY ALARMING.

  10. It is 1 year before freezing the engineering, 5 years before the plane is to be delivered. I would think that there is time to work out the details…if it was 2 years before delivery and they were making changes, then I would be much more concerned. The Sky is not Falling…yet.

    • There is actually a year and a half before the final design and engineering is fixed. I hope they are doing as much exploration to maximize this model as possible. Much of the determination will come from the engine configuration anyway so I would not get to excited over these generalized comments and market mantras..

      • That is correct, we fail to mention that if Boeing set the final configuration for the end of 2013 is because they wanted to have time to try out as many solutions and scenarios as possible with the plane before start of parts productions. I guess that is part of the lessons learned from the 787.

    • We are not talking about details here Mike. The physical constraints impose an almost insurmountable challenge to the Boeing engineers.

      The engine guys are telling the airframe guys that they need a large fan of 70 + inches. The airframe guys reply that they would need to raise the MLG along with the NLG to meet the required target of an optimal fan diameter. But they add that in order to raise the MLG they would also need to redesign the centre wing box. That’s when the finance guys jump in and say “you can’t do that, it’s too expensive!”

      Have you ever tried to square a circle? Mathematicians have been at it for more than 2000 years. No one has found a satisfactory solution yet. I am afraid the same thing might be happening at Boeing right now.

      • Karl brings up the lessons learned from the 787 (and you could also add the 747) and there is little doubt that Boeing is playing it safe with the MAX.

        Imagine if Boeing would have had to back track on the 68.4″ fan diameter so the is little doubt that there was some design margin. Of course, it isn’t just Boeing but principally CFM that is designing the IPU so it wouldn’t be surprising if CFM had some margin built in, too.

        In the end, it is a measurement consisting of ~12 stacked nickels. With 1.5 years before final design freeze it would really stretch the imagination that between CFM and Boeing that they can’t manage to work out a solution that doesn’t involve major and costly structural changes.

  11. Almost certainly they have worked something out to get the extra 1.6″.
    It suggests they are really scratching for percentage points. 1.6″ will give around 0.8% better SFC, but less the penalty for extra weight and presumably some aerodynamic loss.
    Wonder if it has to go back to the wind tunnel?
    Bottom line may be that they are still not there in terms of performance.

    • If it’s 69″ we’re only talking about a 0.6″ increase in fan diameter. Not so much of a change, then, but it sure looks like they’re trying to squeeze every possible fraction of an inch out of the venerable 737 airframe.

  12. Andrew :
    Bottom line may be that they are still not there in terms of performance.

    That would be a nice summary of the situation. At least for the way I see it. I like the words “may be”. Because we don’t know yet. But it’s possible that the Boeing engineers already know if they are going to meet their target or not. But they remain silent for some reason. For me it is a “deafening” silence. Maybe that’s why “I can’t hear” what many posters are saying here.

    And it’s not only the Boeing engineers, but also the Snecma engineers and the GE engineers. I would love to hear what they all have to say. It would be really nice if one key player of each party involved could come on this blog and put the record straight.

  13. Gentlemen, a little fairly recent history:
    Before the PAS of 2011, Boeing was still touting an all new airplane to replace
    the 737, but when Airbus chalked up over 1200 firm orders for the A320NEO
    at the PAS, Boeing had to make a very serious decision in a great hurry, to
    prevent Airbus from conquering the lion’s share of the MR market.
    It was not until the AA Board meeting in August, when AA was about to sign
    up for 500 A320NEO’s, when Boeing Board members at the highest level,
    pleaded with AA to give them a chance to compete for there business with a
    re-engined 737 model, with a reduced-fan-diameter CFM engine, because an
    all new 737 replacement a/p would come too late to maintain parity in this
    market between Boeing and Airbus.

    AA than gave Boeing the opportunity to make them an offer for 100 units BE
    FORE THE END OF 2011 and signed a firm NEO contract for the remaining 400
    units, the A320 landing gear being tall enough to accommodate both the CFM
    and the P&W GTF engine without any restriction.

    Boeing and GE/SNECMA soon realized, however, that it would NOT be possible
    to achieve and provide the required fuel-burn guarantees with the GTX engine
    on the MAX, due to restricted ground-clearance below the engine, forcing
    Boeing to extend the NLG by 8 inches, in the believe that this would solve the
    problem.
    In the meantime the end of 2011 for AA has come and gone, the NLG was ex-
    tended by 8 inches and Boeing & CFM proudly announced early this year, that
    an 68.4 inch fan diameter would do the trick, until this week when it was made
    clear that a 70 inch fan-diameter would be required, to provide the required
    fuel-efficiencies.
    Now they are talking about another 4 inch extension on the NLG and so it con-
    tinues, WITHOUT any confirmation that the above changes will do it this time,
    and ALL THAT WITHOUT A SINGLE AIRLINE OR BOEING, WILLING OR ABLE
    TO SIGN A FIRM 737MAX CONTRACT, while Airbus continues to ad to the
    1,600 or so NEO’s, for which they have firm contracts!

    Whatever you fellows think, I am very concerned that in the end, Boeing may
    well be forced to extend the MLG by the required length, at a significant ad
    ditional cost, to be able to offer the MAX with sufficient operating advantages
    OVER THE NEO, to capture a good share of this market!

    • Quoting Rudy:

      “In the meantime the end of 2011 for AA has come and gone, the NLG was ex-
      tended by 8 inches and Boeing & CFM proudly announced early this year, that
      an 68.4 inch fan diameter would do the trick, until this week when it was made
      clear that a 70 inch fan-diameter would be required, to provide the required
      fuel-efficiencies.
      Now they are talking about another 4 inch extension on the NLG and so it con-
      tinues, WITHOUT any confirmation that the above changes will do it this time,
      and ALL THAT WITHOUT A SINGLE AIRLINE OR BOEING, WILLING OR ABLE
      TO SIGN A FIRM 737MAX CONTRACT, while Airbus continues to ad to the
      1,600 or so NEO’s, for which they have firm contracts!
      Whatever you fellows think, I am very concerned that in the end, Boeing may
      well be forced to extend the MLG by the required length, at a significant ad
      ditional cost, to be able to offer the MAX with sufficient operating advantages
      OVER THE NEO, to capture a good share of this market!”

      Where do you come up with these numbers (another 4 inch)??? There is no requirement beyond the 8″ extension for a Fan up 70″.

      From Flightglobal:

      http://www.flightglobal.com/news/articles/boeing-close-to-re-engined-737-fan-size-decision-361001/

      “A design shelved earlier this year, designated the 737RE, featured a 177cm (70in) fan, which required an 8in nose gear extension to meet the required 43cm (17in) engine nacelle ground clearance to avoid hitting taxiway lighting.

      The 737 could have accommodated up to a 170cm (67in) fan before requiring any changes to the landing gear.”

      • That came from me I believe. I computed the additional ground clearance required for a 70″ fan using the total fan diameter instead of the radius. That gave me a figure twice as large as necessary. KC has already pointed out my mistake in # 9.

        Using the radius it would be more like 2″, or less, depending if you believe or not that they are maxed out on the ground clearance. KC believes they still have some margin left. But I think not. That’s because I want to give him a hard time. It’s part of my role as the devil’s advocate. 🙂

        • It all has to do with complying with the minimum ground clearance of 18″ under the engine nacelle. I might add that Boeing could ask the FAA for a waiver to that requirement for an inch or two, but have not done that.

  14. Rudy Hillinga :
    Boeing had to make a very serious decision in a great hurry.

    This is a key element that many people failed to appreciate at the time. It is never good to take hasty decisions. It was a panic resolution that made Boeing look like if they were unprepared. But if that’s the case why then were they caught by surprise in the first place?

    Maybe they had other plans. Like designing a brand new model to be called the 797 perhaps? I agree with most of what you say Rudy. Except that I believe they still had plenty of time to bring the NSA to market before they would start loosing parity. They have a huge backlog that would keep the 737 in production for the next seven years even if they stopped gathering new orders altogether.

    It is true that the neo would come a few years before the NSA. But I think the customers would have been willing to wait a little because the NSA would have been so superior to the neo that it would probably have destroyed the business case of that aircraft.

    They had a lot more to gain with the NSA than they had to loose. With the MAX it’s the other way around. And parity might actually be already behind Boeing.

  15. leehamnet :
    69.4 to be precise; one inch increase.

    What is the fanblade tip clearance on these engines like ;-?

  16. A figure of $4 billion has been touted for a new wing(and I guess MLG).
    Over a 2000 unit production, this is only $2 million per copy plus finance cost. Probably a one year later first delivery, but hardly a show stopper?
    Are the bean counters suggesting after 787 and 748 and a few other contractual disasters there is no money available to cover this?

    • That is a lot of money to put down for an outdated design that has a limited future. A brand new design would obviously be a lot more expensive and would probably cost two to three times more than that. But at least Boeing would have a state of the art aircraft that would allow them to crush the competition. And I am not talking only of Airbus. Bombardier is coming, and so is COMAC.

      Here is my message to Boeing: Stop wasting time and money on an old clunker, and embrace the future.

      • You could say the same thing to Airbus. After all, the A-320 is no spring chicken, either.

        I might remind you the old Boeing clunker has firm sales and committments into the 2020s. It will be the first jetliner in history to hit 10,000 sales. I’d say that’s pretty good for an old clunker.

  17. KC135TopBoom :
    You could say the same thing to Airbus. After all, the A-320 is no spring chicken, either.

    If Airbus was to come out with a brand new design, which is completely unnecessary in their case, they would not only crush the competition, they would obliterate it. And that is because the 737 has limited potential left it its venerable airframe. Whereas the A320 remains one of the most advanced aircraft in the world, especially in its latest incarnation.

    The A320neo would have a very hard time to compete with the NSA, but Airbus would still be able to sell a few. They would quickly loose parity though. On the other hand the 737 MAX would not be able to survive if squeezed between the CSeries and the A500.

    The A320 replacement (which I call the A500 above) would be given a similar mission as the A350XWB. That is to hit two birds with one stone. But in the case of the A500 it would go after the 737 and 757, whereas the XWB is going after the 777 and 787.

    • The A-320 is far from “one of the most advanced aircraft in the world, in its latest incarnation”. It is a 1988 design (24 years) and is basicly still the same airplane. Its latest incarnation is to add blended winglets to a 1988 wing. The B-737NG has had blended winglets now for more than 10 years. The B-737NG got a new, more advanced wing in 1998, which is more advanced than the 1988 wing on the A-320, and the engines on the B-737NG (CFM-56-7B) are an updated version than the CFM-56-5B engines (from CFMI) on the A-32X. LH and QF both have said the A-320 and B-737 are close enough to paridy to be indistingushable in their operations (and LH doesn’t operate the B-737NG, it flies the older B-737CLASSIC series).

      Now I do agree with you that the A-320NEO would not be able to compete against the Boeing NSA, just as the B-737MAX should not be able to compete with your A-500.

      Are you sure your A-500 will be able to compete with the NSA? It won’t really have much effect on the B-737 or B-757, as Airbus is 15 + years away from an A-320 replacement. I am not so sure the A-350 will be able to compete with the B-787 or the B-777-8X/-9X. Out of the 3 models (so far) in the A-350 family, two of them are failing to attract much attention from the airlines (A-358 and A-3510). Well, I could be wrong because the A-3510 IS attracting attention, but not the type of attention Airbus wants (negaitive), and is loosing sales.

      • That would make the A320 about four years old, because it was twenty years ahead of its time when it first came out. 😉

        It took more than twenty years for Boeing to catch up with the FBW technology first introduced on the A320.

        You have a point for the wing though. If we look at the the drag reduction that the Bombardier engineers were able to extract from the CRJ1000 wing it is quite impressive. But I am not sure if the NG wing can be viewed as a modern wing when compared to the A320 wing. I don’t have the exact delta figures but it’s nowhere near the 6% of the CRJ1000.

        Are there any aerodynamicists in the room?

        Now to answer your question about the A500 versus the NSA, please note that my hypothesis, and this was just for the sake of the discussion, was for the launch of the A500 immediately. Like I said the A500 is not necessary for Airbus at this time. But for Boeing the NSA is not only necessary, it is becoming urgent.

        So, if the A500 was to be introduced in the coming years (please don’t hold your breath) it would fill the vacuum left by the 757 termination. And when I said that in my prior post I also had the NSA in mind, for it would accomplish the same thing. In other words the NSA would replace both the NG and the 757.

        In regards to the ability of the A350XWB to compete with both the 787 and 777, I am not so sure either. But I know that is what Airbus had in mind when they updated the A350 to the XWB evolution.

        • The reason why we won’t see the NSA or A-500 for years to decades is because there is no new engine technology beyond the Leap-1A/-1B/-1C and the GTF. Both OEMs need new engine technology that promises a reduction in fuel burn or 20%-25% beyond what the MAX/NEO offer. Or an engine that burns a fuel that is much cheaper than the current jet fuels, including the so called ‘bio-fuels’. This new fuel must be compatable with the exsisting fuel infastructure at airports.

          The new engine technology must also be expandable from NB airplanes to WB airplanes, which will all be replaced, too. The first engine OEM and airframe OEM to those goals wins. But it has to start with the NB market, as that is the single biggest market for the airframe OEMs.

  18. KC135TopBoom :
    The reason why we won’t see the NSA or A-500 for years to decades is because there is no new engine technology beyond the Leap-1A/-1B/-1C and the GTF.

    Yes KC, and by the time Boeing realizes that there is still no miraculous engine technology around the corner, the 737 will have become a dusty museum piece.

  19. In regards to the ability of the A350XWB to compete with both the 787 and 777, I am not so sure either. But I know that is what Airbus had in mind when they updated the A350 to the XWB evolution.

    I could see Airbus develop a larger wing for the A350-1000. It should, of course, be derived from the A350-900 wing and be given a tapered wing-box insert, comprising two additional fuselage frames (0.635m, or 25 inches) in order to increase wing area/fuel capacity. However, unlike the tapered wing box insert on the A340-500/600, the insert portion should end at the outboard intersection point between the full span single slotted flaps and the ailerons. On the A345/A346, not exceeding the Category-E 65m wingspan limit was an important design criteria, so an extra spanwise wing insert similar in concept to the following linked patent by Boeing (Fig. 6B), adjacent to the outboard engines was never an option.

    http://www.google.com.gt/patents?id=x4oTAAAAEBAJ&pg=PA5&source=gbs_selected_pages&cad=4#v=onepage&q&f=false

    IMO, If Boeing revives the original 777-200 wing-fold concept for the 777-8X/9X, Airbus could follow suit with a wing-fold mechanism for an enlarged more capable 747-sixed wing for the A350-1000, which should be derived from that of the one on the A350-900, but which in addition would comprise of both a tapered wing-box, an outboard spanwise insert and having a total wingspan exceeding 71m. Add three fuselage frames aft, and two forward, in addition to the two extra frames in the centre wing box, and you would have a new revised A350-1000 with a total length of 78.325m. The passenger capacity increase in Y class would be 5 additional rows; or 45 seats.

    I could also see Airbus re-using the A350 fuselage in an A360 family using two different wing sizes. One version could have a wing with an area similar in size to the one on the 767-400 (290 m2), while the other one would have a wing similar size to the A330 wing (360 m2). Both of these wing versions would, in all likelihood, have a similar amount of commonality as the ones on the A350; that is, if Airbus proceeds with a large wing on the A350-1000.

    Finally, IMO the A350-900 is just the first version of an all new WB family. As Airbus demonstrated with the A300, A310, A330 and A340, the original A300 fuselage configuration was ultimately used in combination with 4 different wings (A300, A310, A333/A343 and A345/A346). Why should we not expect Airbus to copy their own success in using the A300 fuselage configuration on four different platforms, and doing the same with their new “XWB” widebody fuselage as well?

  20. OV-099 :

    The A350-900 is just the first version of an all new WB family.

    That is the reason why the XWB is such an important step forward. Airbus would
    not have been able to “start a new family” with the A350Mk1. So it should thank the original A350 critiques for having thrusted Airbus into a new era at the most appropriate time in its evolution.

    • Exactly, that’s why IMO it’s relatively meaningless talking about how the A350 competes with both the 787 and the 777. For the time being, Airbus has the A330-200 at the lower end, and due to the 787 production imbroglio, Airbus hasn’t needed to do much in order to maintain a strong presence in the 250-seat WB market. In the long run, what they in all likelihood will do, is to put a 20-20 percent smaller wing (than the one on the A350-900) on the XWB body. Such a new A330/787 sized wing should incorporate at least a decade more advanced technolgy than the 787 wing and should be more than able to compete with the 787-8.

      At the end of the day, what truly matters IMO is production efficiencies. If Airbus would produce 20-25 XWB type aircraft per month a decade hence, all having different sized wings and fuselage lengths, IMO that’s significantly more efficient than having two all different different production lines with little, or no commonality, producing the same number of frames per month (i.e. 777 and 787).

  21. leehamnet :
    69.4 to be precise; one inch increase.

    So now we are talking about Boeing/CFM finding clearance for only 8 stacked nickels. Could someone explain how this will result in the “MAJOR AND COSTLY STRUCTURAL CHANGES” that is being asserted.

    • The idea here is that Boeing is doing everything it can to avoid major and costly structural changes. It is not an easy proposition. And many of us are not convinced that it is even possible.

      But the money that Boeing is trying to save on the airframe will have to be spent on the very special engine that CFMI is trying to design to prevent Boeing from spending too much money on the airframe. It is a form of circular reasoning that only demonstrates that Boeing is trying to transfer the burden on the engine supplier.

      For each 737 sold since the introduction of the Classic, at least two CFMI engines were sold in the same operation. That represents an enormous business for CFMI because it has the exclusivity. And I am sure CFMI would not be willing to spend that kind of money on the LEAP-1B without that exclusivity. That explains in part why Boeing is not making a big effort to adapt the P&W GTF engine to the old 737 airframe.

      But this represents a big gamble for CFMI. The development of the 1B will be extremely costly and take a very long time. Boeing will have to sell many 737 MAX if CFMI is to recoup its investment. But if CFMI is unable to offer a competitive SFC on the 1B it could compromise a very successful, but very risky, business association.

      The exclusivity that CFMI had with Boeing on the 737 allowed it to thrive and establish itself as a formidable force in the narrow-body business. But that same exclusivity could now undermine Boeing’s parity position in this sector.

      • You reply to my post… 5 paragraphs… but don’t answer it.

        Since you responded, why do you believe that increasing the fan radius by ONLY 8 stacked nickels could result in “MAJOR AND COSTLY STRUCTURAL CHANGES”.

        I’m not asking for a guess but something tangible that you are basing your opinion on.

  22. Joseph,

    I have never said that a small increase in fan radius on the order of 8 stacked nickels would require major and costly structural changes. And I do not recall anyone saying that, or meaning that, either.

    The original sentence was posted by Rudy Hillinga. Rudy, like myself and others, is very concerned by the present situation on the MAX. As Rudy was one of the first to notice, Boeing is late on delivering on its promises. The delay is a telltale sign that they have run into major difficulties. We think that those difficulties might actually be insurmountable, unless major and costly structural changes are undertaken by Boeing.

    But is Boeing ready to undertake major and costly structural changes in order to solve the problems we think they have encountered? I don’t really know. My impression though is that Boing has shoved the problem in CFMI’s backyard. CFMI should be willing to take the challenge as long as they retain exclusivity. But it is possibly facing insurmountable difficulties of its own. Like delivering guaranteed fuel burn performances for example.

    Because of the constraints imposed by Boeing in regards to core diameter and fan radius, the LEAP-1B might end up being a very different engine than the 1A. And because of that it might become a very costly derivative of the basic LEAP concept.

    There is no doubt in my mind that the CFMI engineers are very capable, both at GE and Snecma, but what is being asked from them is more or less equivalent to the squaring of the circle.

  23. Normand Hamel :
    Joseph,
    I have never said that a small increase in fan radius on the order of 8 stacked nickels would require major and costly structural changes. And I do not recall anyone saying that, or meaning that, either.

    Let me jog your memory…

    Rudy Hillinga :

    To come out with a 70 inch fan at this late stage, in spite of comments from
    Boeing that they could not go beyond 68.4 inches WITHOUT MAJOR AND
    COSTLY STRUCTURAL CHANGES,

    Rudy Hillinga :
    Joseph, thysi and keesje
    Did you fellows miss the words “Boeing said that they could not go beyond
    68.4 inches WITHOUT MAJOR AND COSTLY STRUCTURAL CHANGES?”
    That was last year, so in my opinion, this late admission that the 68.4 inch
    fan is not working, IS VERY ALARMING!

    • Well, either Boeing was wrong when they said that last year, or they did some “thinking outside of the box” and found another way to increase the fan size without major structual changes. So it appears they can still go with a newer 69.4″ fan size and still have more than 18″ of ground clearance under the engines, as required.

      Or, another way is they got the FAA to waive the 18″ ground clearance if the restrict the B-737MAX to taxiways no narrower than 75′

    • I was talking about the “8 stacked nickels” when I said that I cannot recall anyone “saying that or meaning that”. Those words were used by you, not me or anyone else. What we had in mind is a lot more than 8 stacked nickels.

      We don’t have the real figures and that forces us to speculate. We make assumptions to nourish the discussion. Some people are happy with what Boeing says and don’t go any further. And that’s fine, provided they let others express their viewpoint.

      What I have noticed though is that some posts are attacking other posts without bothering to explain themselves. They just negate. If it is not personal, I don’t mind someone attacking my posts. For something fruitful might come out of it. I have learned a lot from my fellow bloggers that way. And if I am not mistaken that’s is the whole purpose of this blog.

      So please Joseph, let me express my opinion even if you think it’s not worth a nickel. 😉

      • Normand Hamel :
        I was talking about the “8 stacked nickels” when I said that I cannot recall anyone “saying that or meaning that”. Those words were used by you, not me or anyone else. What we had in mind is a lot more than 8 stacked nickels.

        But you did indeed… “I have never said that a small increase in fan radius on the order of 8 stacked nickels would require major and costly structural changes. And I do not recall anyone saying that, or meaning that, either.”

        And for the record, I did not start the exchange. It was you that replied to my post about the 8 stacked nickels. So please, Normand, do not suggest that I am not letting you express your opinion or speculations. And setting the record straight is not attacking, especially when I am using what is in Leeham’s commentary about this topic.

  24. KC135TopBoom :
    Well, either Boeing was wrong when they said that last year, or they did some “thinking outside of the box” and found another way to increase the fan size without major structual changes. So it appears they can still go with a newer 69.4″ fan size and still have more than 18″ of ground clearance under the engines, as required.

    My take on the article later in the day by Leeham (More on the changes to the CFM LEAP-1B), it has been more CFMI than Boeing that did some thinking… or, in reality, continued to think with so much time before design freeze…

    The smaller core also enabled the engine to be mounted closer to the wing, which in turn means the previously announced 8 inch nose gear extension remains valid.

  25. My take would be Boeing wasn’t really sure about the maximum fan size. The ground clearance on the MAX is influenced by among others the nose gear, new engine attachments, wing stiffness and weight of all components and the engines, all under worst case operation conditions. Probably further analyses, testing, simulations and calculations revealed there was was some extra margin..

  26. KCTB: Observer quoted a Flightglobal article where they mentioned a 17″ clearance requirement yet you keep quoting 18″. Any idea why they have a different value to yours?

    This same flightglobal article also stated that a 70″ diameter fan with an 8″ nose gear extension was looked at and shelved over a year ago. Now they are back to 69.4″, which is a 0.3″ diameter difference to the 70″ plan. Sorry but I do not comprehend why some people can not accept that with such flip flops, some people doubt that Boeing and CFM have a clear plan on what they are doing.

    Would this new concept pretty well put to end Boeing’s dream to push the MAX entry date forward from 2017? Or do they believe that is still a possibility?

    • At this point in the develope of the MAX, anything is still possible. The 17″ is the height of a standard size taxiway edge light (there are different heights up to 3 feet tall). Because of this the FAA Airport Design Standard, AC 5300-13, requires an 18″ minimum ground clearance for engines hung below the wing or turning propellers.

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