Technology Credibility

During the SWA web press conference about their B737MAX order, the CFM EVP Chaker Chahrour made an interesting statement. Leeham News and Comments has the quote here: "We believe we have much more credible technology than GTF."
Well, apart from that this might have been only some PR talking, I think we should shed some light on the credibility of the quote itself.
  1. What is the reason for the appearance of the LEAP-X engine on the A320neo and the B737MAX in the first place? - The reasons are pretty obvious to me:
    • The launch of the CSeries, to be powered by the PW1524G
    • The confidence in the Geared Turbo Fan technology Airbus gained after the flight test of the GTF demo engine on their A340-600 testbed.
    • Extensive lobbying from P&W to launch the A320neo with the GTF as one of the engine options
    • In essence: without the launch of the CSeries, which would not have been possible without the Geared Turbo Fan (CFM did only offer a "CFM56light" and the offer from RR did obviously also not meet Bombardier's criteria), Airbus would never have thought about the A320neo family without the threat of the CS300 meant for the A319. And without a A320neo, maybe Bombardier would meanwhile offer a CS500 as well... The GTF Demo Program gave Airbus the confidence to also pick the GTF as on of the engine options for the A320neo. This Demo Program was of course launched well before the launch of the CSeries, so the interest from Airbus in the Geared Turbo Fan technology was there well before Bombardier (and Mitsubishi)decided to put the PW1524G and PW1217G under the wings of their new aircraft.                 
  2. How credible is CFM's technology and technology roadmap?
  • CFM's plan originally was to stay with the basic HPT architecture of the CFM56 - a single stage HPT and a six stage HPC (down from nine stages today). It was only in 2008 when this was changed - due to higher and higher fuel prices fuel burn became more important in comparison to maintenance costs. The TECH56/LEAP56 program became LEAP-X and the architecture was changed to a 2 stage HPT and a 10 stage HPC, much like the GEnx core. Nevertheless the eCore1 ran with the 1 stage HPT and six stage HPC as the hardware for this core was already in work. The first test of the "real" LEAP-X with the 2 stage HPT core was only done this year.For comparison: P&W and MTU had their first HPC rig test in 2007/2008 and their first core test in 2009/2010. The first complete engine, a PW1524G,  was tested in late 2010 and the second flight test campaign of the PW1524G just started this month.
  • CFM meanwhile tested the fan and the LPT. But as the layout of the LEAP-1A was changed in the midlle of the year from a 6 stage LPT to a 7 stage LPT (to drive the larger fan), the test was not made with the production LPT.
  • The reason for the redesign was that CFM lost in the early campaigns (Indigo, ILFC and Lufthansa) against P&W and had to change the design of the engine for a better SFC. A victim of that change is the COMAC C919, which will get the same basic engine, just with different externals and an optimised nacelle. But as noone really expects the C919 to be on time for a 2016 EIS, COMAC will benefit from a better SFC.
  • The question is how the 7th stage LPT affects weight and maintenance cost (apart from additional manufacturing costs beared by CFM). Basically the question is, if the GTF concept is not better suited above a bypass ratio of, say, 9-10. Rolls Royce meanwhile agreed, when Robert Nuttal, Head of Strategic Marketing, said, that his earlier rejection of the GTF meant only that in RR's view the reenginig was no business case, but that "gears work at certain bypass ratios". The current trend to smaller core engines, higher core temperatures, larger fans and higher bypass ratios means that the LPT has to make more and more work. A faster, independent from the fans speed spinning LPT can do more work per stage than a direct drive turbo fan, where the maximum speed of the LPT is determined by the fan diameter, as the fan noise increases dramatically when the tip of the fan hits the speed of sound (everybody can hear the fan "buzz" sound in climb). So a larger fan means more LPT stages for a direct drive turbofan, associated with additional engine length, weight, manufacturing and maintenance costs.
  • If we look at the LEAP-1A as it is defined now, we see a clear similarity with the GEnx, not surprisingly. The compressor design goes back to the days of the NASA E3 ("E cube") compressor. This design was fed into the GE90, the GP7000 and the GEnx and will also find it's way into the Passport 20 engine for the Bombardier Global 7000/8000. Also, the GEnx-1B for the B787 features a 7 stage LPT (the GEnx-2B has a 6 stage LPT, driving a smaller fan and one less booster stage). The GEnx-2B is in service since October, when the first B747-F was delivered to Cargolux, the first GEnx-1B powered is just about to be delivered to JAL. The original Boeing time plan for the B787 was to deliver the first B787 to ANA in may 2008 and the first GEnx powered aircraft about six months later. It is well known that the engines which will be delivered in early 2012 do not meet the SFC objectives from 2008 and GE needs a PIP II programme to get to the target SFC level (the same is true for the competing RR Trent1000). Part of the problem was the LPT, which had too few airfoils in the original design and did not meet target efficiency levels. So GE had to put significantly more airfoils in the LPT, upping the weight of the LPT. Thus the engine might be overweight now...
In this respect the claim that CFM has more credibility on the technology side might be a little bit overoptimistic. But only time will tell us, which company has the better product - although financing may play also a role in the end and at that end CFM has a big ally with GECAS on hand. So it is not the product alone, but the whole package which will decide...

Speaking of decisions: jetblue made a decision yesterday and opted for the PW1100G-JM for their 40 A320neo.

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