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.