Boeing’s NSA could feature game-changing technologies
- A320neo outsold 737 MAX by 9.3% at same stage
- Advanced Technology winglet reduces fuel burn by 1.8% on 3,000nm mission
- A320ceo with Sharklet narrows market value gap with 737NG
- 737 MAX still leads A320neo in COC narrowly
- DLR: Difficult to make small twin-aisle work
- Avolon: average seat count rising to 198 seats by 2032
- Open-rotor concept unlikely in mid-2020s
- Rolls-Royce’s geared UltraFan, with carbon nanotube fuselage, holds potentials
- OoA technology with 50-60/mo rate can lower costs significantly
- CNRP up to 29.4% lighter than CFRP
- OoA process reduces total cycle time by up to 75%
- 200-220 seater bodes well for Asia/Pacific growth, industry up-gauging
There is little doubt that Chicago-based plane-maker Boeing was the clear winner in the biggest-ever aircraft order All Nippon Airways (ANA) placed last month comprising 20 777-9Xs, 6 and 14 additional 777-300ERs and 787-9 Dreamliners, respectively, which account for 78.8% of the ¥1.7 trillion deal value. Beneath the surface, however, ANA picked the A320neo (new engine option) aircraft family with 23 A321neos and 7 A320neos to replace its 17 ageing 737-500s and 15 A320ceos. More significantly, it chose the Pratt & Whitney (P&W) PW1100G-JM geared turbofan (GTF) engine to power these re-engined aircraft which was a pivotal endorsement from one of the world’s most technically rigorous airlines.
At first glance, while ANA is very likely to split its future narrowbody fleet with the 737 MAX replacing its 24 737-800 NGs (Next-Generation) and 18 -700s, let alone the replacement order for 20 A320ceos at its low-cost subsidiaries Peach and Vanilla Air will eventually be up for grabs, this seems to be cementing the A320neo’s lead in the re-engined narrowbody race, with a string of defections unlocked from the Boeing 737 NG’s customer base.
American Airlines (AA) with 100 A321neos, Lion Air with 109 A320neos and 65 A321neos, Norwegian Air Shuttle (NAS) with 100 A320neos, Pegasus Airlines with 57 A320neos and 18 A321neos are just a few of such high-profile cases.
In regaining the lost ground in the narrowbody sector, not only does Boeing have to be more aggressive in securing deals such as Air Canada’s one for 33 737 MAX 8s and 28 737 MAX 9s by agreeing to purchase the Canadian flag carrier’s 20 Embraer E-190s, but also look beyond the current offings of re-engined aircraft.
In doing so, the so-called “New Small Airplane” (NSA) would usher in advances in not just engine, but also materials technologies that promise to be as game-changing as those brought about by its larger sibling, the 787 Dreamliner in its class.
Moreover, the 200-220 seater would be an ideal growth platform for Asia/Pacific carriers whose regional traffic is forecast to grow by 6.3% per annum over the next 20 years, according to Boeing’s latest current market outlook (CMO), in addition to being a 757 replacement.
Most importantly, the NSA’s strategic purpose is to more clearly differentiate Boeing’s offering in the intensely competitive single-aisle market with two similar contenders.
A320neo & 737 MAX technically similar
The acrimonious dogfight between the transatlantic arch-rivals has seen both airframers trading blows over the superiority of their products, with Airbus claiming to have a 60% market share in the re-engined narrowbody segment and that the efficiency gained by re-engining the 737 NG is being constrained by its ground clearance.
Indeed, the A320neo has garnered 2,645 firm orders at press time, or a 58% market share, versus the 1,934 garnered by the 737 MAX.
Boeing refutes such claims by saying that the 69.4-inch CFM Leap-1B engine, albeit smaller than the 78-inch Leap-1A featured on the A320neo, is optimised since the 737 MAX is lighter and hence has a lower thrust requirement, while the ground clearance of 17in with an 8in lengthened nose landing gear remains largely unchanged from the 737 NG.
The 737 MAX is being outsold, Boeing contends, primarily because the A320neo is launched in December 2010 whereas the 737 MAX is only launched 9 months later in August 2011, although the A320neo did receive 9.3% more firm orders at 30 months since launch with 2,114 examples being ordered.
Putting aside the sales leadership argument, the advantages in all-in cash operating cost (COC) that the 737 NG enjoys over the A320ceo (current engine option) today are going to be significantly narrowed on the 737 MAX versus the A320neo, which Aspire Aviation believes pertains to be a 2% advantage, a figure easily tilted in either aircraft’s favour with deep discounts that affect the capital cost portion of the equation. Simply put, the A320neo and 737 MAX are broadly similar from a technical perspective, a view destined to be contested by both sides of the Atlantic.
Airbus asserts the A320neo to be a “better optimised aircraft” whose engines boast a 11:1 bypass ratio on the 78-inch CFM Leap-1A engine and 12:1 on the 81-inch Pratt & Whitney PW1100G-JM engine with only a 1.8 tonnes increase in operating weight empty (OWE) from the A320ceo, whereas the 737 MAX 8’s Leap-1B engine only has a 9:1 bypass ratio with a 3.2 tonnes increase in OWE from the 737-800.
The A320ceo, Airbus claims, has the same OWE as the 737-800 and the A320neo is 1.4 tonnes lighter than the 737 MAX 8.
However, one should caution the different calculation methods employed by Airbus and Boeing regarding the operating weight empty (OWE) and operating empty weight (OEW), respectively. The most crucial difference involved the “at gate” weight adopted by Boeing in calculating such figures at which the airplanes are ready to load passengers and cargoes.
According to an internal slide seen by Aspire Aviation on the calculation behind a Boeing 777-200ER customer’s OEW, items excluded by Airbus’s calculation of the OWE amounted to 12.4 tonnes (27,327lbs), such as galley structure and fixed inserts that weigh 2.67t (5,884lbs), a cargo tare weight of 2.06t (4,540lbs) and catering allowance of 4.2t (9,306lbs).
On a 737 MAX-sized aircraft, the difference in OEW using these methods could amount to 2 to 4 tonnes, Aspire Aviation‘s multiple sources at Boeing said.
Furthermore, Boeing counters that a 180-seat 737 MAX 9 is 6% lighter than a 183-seat A321neo in relative OEW per seat while having a 7% lower cash operating cost (COC), whereas the 162-seat 737 MAX 8 will have a 8% lower COC than the 150-seat A320neo.
Make no mistake, while the 737 MAX family aircraft will continue to be lighter than the A320neo family aircraft, just as figures published by Turkish Airlines show today’s 737 NG to be around 1,000kg lighter than the Airbus counterparts, such a differential will become more diminished going forward, as the 737 MAX adds more weight than the A320neo. In fact, Aspire Aviation forecasts a 600kg difference between the 737 MAX 8’s and the A320neo’s operating empty weight (OEW).
Boeing upped the 737 MAX 8’s maximum zero fuel weight (MZFW) by 3.22 tonnes (7,100lbs) from 62.7t to 65.95t and 737 MAX 9’s by 3.27 tonnes (7,200lbs) from 67.7t to 71t. As MZFW = OEW + payload, Airbus’s estimated increase of 3.1 tonnes on the 737 MAX 8 implies a largely unchanged payload capability for the aircraft, whereas Aspire Aviation‘s sources at Boeing pointed to a 5,500lbs increase in the 737 MAX 8’s manufacturer’s empty weight (MEW) and OEW, thereby implying a 700-800kg increase in its payload capability.
Another sign of the diminishing difference between the A320 and 737 families is the high-density layout being pursued by Airbus, intended to increase the A320’s maximum capacity from 180 seats to 189 seats, with the SpaceFlex galley and a reduction in seat pitches for all aft seats from 29 inches to 28 inches enabling 6 seats to be added alongside 3 more seats added through a smaller aft galley.
The A320’s prospective reconfiguration is instrumental in winning Vueling’s order for 32 A320neos and the certification process with the European Aviation Safety Authority (EASA) has already started, according to an Aviation Week report. This levels the playing field with the Boeing 737-800 which is configured with 189 seats at Europe’s largest low-cost carrier (LCC) Ryanair.
As if their newfound similarities were not enough, Ascend’s aircraft value database is showing a very close trend in market value between new build sharklet-equipped A320ceo and the 737-800, with the former’s sharklet delivering a fuel burn reduction of up to 4%, albeit the 737 MAX’s Advanced Technology winglet promises to reduce the aircraft’s block fuel burn by another 1.8% versus a blended winglet-equipped one, thereby helping the 737 MAX 8 deliver a 15% lower block fuel burn on a 3,000nm (nautical miles) mission.
The Advanced Technology winglet will reduce the aircraft’s block fuel burn by 1% on a 500nm sector and 1.5% on a 1,500nm sector which exceeded Boeing’s initial expectations and contributed to the 737 MAX 8’s revised 14% fuel saving figure on a 500nm sector.
A case for NSA – difficult to make small twin-aisle concept work
In light of Airbus’s A320 reconfiguration initiative, one course of remedy for Boeing could well be revisiting the door modification concept once mulled that could add 9 seats to each variant (“Boeing to make up lost grounds on all fronts“, 27th May, 13), but that alone could not fully address the high-density 240-seat A321neo option being studied by Airbus. The 240-seat option is beyond the 236-seat one unveiled with a deactivated Door 2 and a Door 3 that is being pushed back while adding an additional over-wing exit. Subject to regulatory approval, the high-density option of A321neo is scheduled to enter into service in the second half of 2017.
This lays bare a fundamental question: How to best serve the large narrowbody market that stretches beyond 200 seats? In particular, is there a niche for a 757 replacement and is it large enough to make the investment worthwhile?
“The 737-900ER/MAX 9 covers 95% of the routes flown by a 757 – and Airbus will tell you the same. But there is that 5% that we saw with the 757 that was really game-changing. The 757 brought a unique set of capabilities. There are airlines that really like that capability across the North Atlantic, and the A321 can’t do that and nor can the MAX 9,” Boeing Commercial Airplanes (BCA) vice president (VP) of marketing Randy Tinseth told flightglobal.
More pressingly, there appears to be a trend of up-gauging across Airbus’s and Boeing’s single-aisle aircraft families, with higher capacity variants accounting for the bulk of the order backlogs. The A319neo’s backlog of 45 and the 737 MAX 7’s of 55, merely represent 2% and 3% of their respective order books. In contrast, the A320neo and the 737 MAX 8 account for 77% and 86% of their respective backlogs.
Going forward, it is reasonable to assume that the current trend of up-gauging will continue and that more airlines will choose the largest variant – A321neo and 737 MAX 9, to meet growing air travel demand and slash per-seat costs, despite they account for only 21% and 11% of these aircraft families’ backlogs as of this writing. This is also evident in recent aircraft purchases with jetBlue swapping 8 A320ceo and 10 A320neo orders into orders for 8 A321ceos and 10 A321ceos when announcing the 10,000th A320 family order and Delta Air Lines placing an order for 30 A321ceos in September 2013.
Aircraft lessor Avolon, meanwhile, forecasts the average seat count will increase by 18% to 198 seats by 2032.
Intriguingly, a September 2012 research paper by Jorg Fuchte, Bjorn Nagel and Volker Gollnick of the German Aerospace Centre (DLR), titled “Twin Aisle Aircraft for Short Range Operations – An Economically Attractive Alternative?”, sought to explore the potential of utilising twin-aisle aircraft to satisfy demand in this “transition segment” between the narrowbodies and the widebodies.
The paper studied a total of 70 different layouts in 5 different cross-sections and looked at their impacts on turnaround times, block fuel burn per seat, direct operating cost (DOC) and the specific scenario in which such a small twin-aisle might make business sense and become economically viable.
It found that a 7-abreast small twin-aisle in a 2-3-2 configuration with a slightly smaller cross-section than the Boeing 767-300ER, whose fuselage width of 5.03m is some 1.27m (4.17ft) wider than the 3.76m width of the 737NG’s “double-bubble” fuselage, yields the biggest reduction in turnaround times over a standard single-aisle such as the 201-seat Boeing 757-200, which has a 22 minutes mean turnaround time.
Specifically, a 200-220 seat 7-abreast small twin-aisle can shave around 12 minutes off the comparable turnaround time of a regular single-aisle aircraft and this advantage enlarges to around 13 minutes on a 240-seat 7-abreast small twin-aisle.
Yet it is very difficult to make the small twin-aisle concept work. Even factoring in the higher number of flights owing to the significantly reduced turnaround times, the 220-seat 7-abreast small twin-aisle will only beat the 6-abreast single-aisle, such as the 737 MAX 9 and A321neo, in direct operating costs (DOCs) on sectors under 700nm.
Using more accurate assumptions with a crude oil price of US$116.7 per barrel, an 8% interest rate and a 12-year leasing period, the 220-seat 7-abreast small twin-aisle will only beat the 737 MAX 9 and A321neo in DOC on missions under 400nm.
Admittedly, while the study ignores the incremental revenue generated by carrying more cargoes, it is somewhat difficult to imagine belly cargoes would be a key differentiator on such short missions. The only scenario that is overwhelmingly in favour of the small twin-aisle over the 737 MAX 9 and A321neo, as the study pointed out, is for it to have a design range of 1,800nm but sharing the same wing designs that enable its single-aisle counterparts to fly 2,400nm sectors which negate the lighter airframe’s weight advantages at a fuel price of US$175 per barrel.
Therefore one looks poised to be disappointed in envisioning a small twin-aisle replacement for the 757, 737 MAX 9 or A321neo, whose ranges of 3,595nm and 3,750nm, assuming 85% annual winds, provide significant flexibility for airlines, let alone the 4,100nm range the winglet-equipped 757-200 boasts.
Engine & materials technology
Nevertheless, the fact that the NSA, or the original Y1 that was shelved as the 737 MAX had been launched, is a 757-sized single-aisle airplane does not mean it cannot be more commercially successful than its ancestor of which 1,049 examples were ever sold.
On the contrary, sporting more subtle but equally game-changing features in the latest production system, material and engine technologies, the NSA could well be a revolutionary airplane positioned at the new sweet spot of 198 seats by the time it enters into service in 2025 and thereafter, a market segment the 757 was designed for which ultimately proved to be well ahead of its time, some 40 years early.
Above all, a next-generation out-of-autoclave (OoA) production system would theoretically be ready by 2025 and be capable to produce 50-60 composite-based NSAs per month whose economies of scale would lower the production cost significantly by employing vacuum-assisted resin transfer moulding (VARTM) processes.
In the process, the composite part to be moulded will be formed in a curing chamber on top of a moulding tool floating on the heat transfer fluid (HTF) which also acts as a coolant for the part, according to Quickstep of Australia.
This will bring several key benefits including an up to 10 times lower viscosity which greatly enhances its adhesion to the honeycomb structure; low void level of less than 1% which was previously only achievable by autoclaves on prepregs as well as an up to 75% reduced processing time.
Such technologies are anything but far-fetched: it is already being used to produce non-load bearing carbon nanotube reinforced polymer (CNRP) structures such as lower side skins, maintenance access panels, fuel tank covers, lower skins and in-board weapons bay doors of the Lockheed Martin F-35 Lightning II Joint Strike Fighter (JSF), on which Quickstep is a subcontractor to Northrop Grumman.
Should the OoA process be adopted on the NSA, Boeing will have to ramp up the technology maturation process aggressively over the next decade, especially on CNRP, a groundbreaking new type of composites that holds promising potentials in weight trimming over the carbon fibre reinforced polymer (CFRP) being used on the 787 Dreamliner, A350 XWB and the likes.
In particular, the 50% single-walled nanotube (SWNT) CNRP has a 59% lower density at 1,130kg/m versus the 2,780kg/m of the 2024-T3 aluminium used on the 747-400 and 29.4% less dense than the CFRP’s 1,600kg/m density.
Sceptics might point to the fact that CFRP’s weight advantages in terms of a 45% lower density are eroded by a swathe of factors, as Alcoa points out 25% of this density advantage is lost owing to the CFRP’s unidirectional strength, another 10% due to the need to create an electrical structural network (ESN) and the remaining 10% due to the CFRP’s inability to be tapered as much as aluminium could. 3rd-generation aluminium-lithium (Al-Li) such as the Al-Li 2199-T86, additionally, also has a 5% lower density than the baseline aluminium being used.
That said, while aluminium-lithium could better optimise to the specific engineering loads on each part of the airplane, such as tension on lower wing skin and compressional force on upper wing skin, CNRP could nonetheless hold an around 24% density advantage that will translate into significant weight savings on a 757-sized airplane.
Even should Boeing continue to opt for CFRP on the NSA’s fuselage with which it is familiar, utilising the CNRP on non-structural parts could yield meaningful weight savings, let alone that adopting a CNRP fuselage 10 years from now would not be unrealistic as the aerospace industry learns more of the material and gains experience.
Last but not least, advent in engine technologies has always been an integral part, if not the centrepiece and primary driver, of any new aircraft development, and the NSA is no exception.
One could argue that the renewed interest in NSA or a 757 replacement is kindled by the performance improvement package (PIP) being mulled by Pratt & Whitney (P&W) which slashes specific fuel consumption (SFC) by another 3% through improved blade profiles and component contours and the “A320neo Plus” which an Aviation Week report says features upgrades in avionics and an adoption of electro-hydraulic actuators. These upgrades could enter into service as early as 2016 and 2019, respectively.
And the decidedly different engine architectures and future growth paths are putting engine manufacturers at odds with each other, although this is hardly surprising.
CFM International and General Electric (GE) are banking on ceramic matrix composites (CMCs) that can survive temperatures as high as 1,480°C (2,700°F), 200°C to 240°C higher than conventional metals to increase its Leap engine’s thermal efficiency while reducing weights since CMC has one-third the density of the materials it is replacing.
While expensive, with the Leap’s backlog of 2,801 engines, including the Leap-1B on the 737 MAX where it is the sole engine supplier, the GE-Safran venture is confident it can benefit from economies of scale and in the future, apply the CMC on rotating parts in the hot section of the engine that cuts 1.5% of specific fuel consumption (SFC) on top of the 15% saving in SFC promised by the Leap-1A versus the CFM56-5B engine.
CFM claims that combining the CMC shroud at the first stage of the high pressure turbine (HPT), a 2nd-generation twin-annular pre-mixing swirler (TAPS II), a larger and slower fan, active tip clearance control and a debris rejection system, the Leap-1A will have a 1% lower SFC than the PW1100G-JM when new and another 1% better retained SFC over the years, or a US$4 million saving per year. The SFC advantage on the A321neo, CFM asserts, will amount to 3% over longer stage lengths.
Pratt & Whitney (P&W) rebukes that its PW1100G-JM will power around, if not more than 75% of all A321neos on order and that its reduction gearbox in the fan-drive gear system (FDGS) eliminates 7 stages or 20% of life limited parts (LLPs) while made up of only 7 moving parts, thereby offering a 20% lower maintenance cost versus the CFM56-5B engine. Its 3:1 gear ratio which enables the engine fan to rotate at a third of the speed of the low pressure turbine (LPT), thereby maximising propulsive efficiency, could be raised to 5:1 while incorporating ceramic matrix composites further down the road. The CFM Leap-1A engine has 23 compressor and turbine stages, versus 17 at the PW1100G-JM engine, excluding the gearbox.
While the jury is still out on the superiority of these engine architectures, as the CFM Leap-1A will power 32.8% or 867 A320neos and the PW1100G-JM 32.5% or 859 examples whereas 34.7% remain undecided, a late-2011 Massachusetts Institute of Technology (MIT) paper noted that the PurePower engine not only represents a “significant leap” in fuel efficiency and noise, but also of subsystem integration with a 32% increase in functional group connectivity from the PW4098 engine to the PW1524G PurePower engine. The paper concluded that it will be increasingly difficult to extract efficiencies from existing components such as the high pressure compressor (HPC) and low pressure compressor (LPC) absent a change in architecture, since they are already optimised today.
A noteworthy point is P&W’s stance is strikingly similar to that of Rolls-Royce and the future vision of the Derby, England-based and the Hartford, Conneticut-based engine-makers increasingly converges despite Rolls’s departure from the International Aero Engines (IAE) consortium.
Rolls-Royce unveiled two new engine concepts – “Advance” will be available by 2020 and have a 20% lower specific fuel consumption (SFC) than the Trent 700 or 6% better than the Trent XWB-97 engine, as well as the geared “UltraFan” that will have a 25% better SFC than Trent 700 and 10% better than the Trent XWB-97 engine. “Advance” will have a bypass ratio of more than 11:1 and overall pressure ratio (OPR) of more than 60:1 and the “UltraFan” will boast a bypass ratio of 15:1 and a OPR of 70:1. These engines will feature a composite fan blade made from 3rd-generation carbon-titanium (CTi), thus saving 1,500lbs per aircraft in addition to using ceramic matrix composite (CMC) components. A thrust-reverser system is also being eliminated.
“This [large diameter fan] gives the LP turbine a significant challenge and to mitigate that we have a reduction gearbox,” Rolls-Royce civil large engines president Eric Schulz was quoted as saying.
By the time the UltraFan enters into service in 2025 with a 5% lower specific fuel consumption (SFC) than the GE9X, it could well incorporate lessons learnt in Europe’s Clean Sky 2 programme in which Snecma is studying a counter-rotating turbofan that slashes engine SFC by 16% compared to the Leap-1A and noise by 20dB.
In pushing the boundaries with production systems, engines and materials technologies, Boeing’s new small airplane (NSA) could deliver a block fuel burn reduction of at least 20%, half of which could come from a downscaled UltraFan or Snecma’s counter-rotating turbofan engine.
For some, however, the most daunting question is not about these technologies’ readiness in 10 years’ time which are not insurmountable so long as a deep research and development (R&D) fund supports and hastens the maturation process. Rather, it is absent a small twin-aisle that clearly distinguishes the NSA from the 737 MAX family, whether the 737 MAX’s business case would be decimated and cannibalised.
Quite frankly, the NSA and the 737 MAX are complementary to each other, especially the NSA is designed and optimised to perform 4,000nm missions while occupying a class of its own at the new market “sweet spot” of 200-220 seats in a standard 2-class configuration. The existing 737 MAX 9 and A321neo could only trade range with higher passenger capacities and the 240-seat A321neo would not reach its touted 3,750nm range it is supposed to fly with 185 passengers in a standard 2-class configuration.
Below 1,500nm, where more than 90% of the world’s narrowbody flights take place, it makes little sense to carry the structure and heavier airframes designed to transport 200-220 passengers over 4,000nm sectors. Therefore there will continue to be needs for the 737 MAX and hence it is paramount for Boeing to be continuously aggressive in winning new 737 MAX deals beyond its traditional customer base from which recent deals were won, such as flyDubai, Nok Air, SunExpress, SpiceJet, South Africa’s Comair and Jet Airways.
Availability would be key and the 737 production rate is set to reach 47 airplanes a month in 2017 after ramping up to 42 a month this March. This would be enticing for Chinese carriers holding the means by which the 737 MAX could make up lost grounds, as their 5-year plans that need to be approved by the Chinese government mean many Chinese airlines are late to ordering re-engined narrowbody aircraft. Reuters reported that Boeing secured 200 737 MAX commitments from Chinese carriers and Shandong Airlines has committed to ordering 34 737 MAXs.
Though it is easier said than done as China typically splits its aircraft purchases and uses such deals as bargaining chips to achieve other goals. Already Chinese carriers are among those on the A320neo’s customer lists, including a commitment for 100 examples, with 60 for Air China, 20 for ICBC Leasing made in September 2013, 70 for China Eastern Airlines (CEA), 18 for Qingdao Airlines and 9 for Zhejiang Loong Airlines, with possibly more in the pipeline.
China also signed a 10-year extension deal this March with Airbus over the final assembly line of China (FALC) in Tianjin and unblocked orders for 27 A330s that were the casualty of a China-EU row over the controversial emissions trading scheme (ETS), let alone Airbus is also increasing the A320 production rate to 44 per month in the first quarter of 2016 and 46 per month in the second quarter which negates some of the advantages of 737 MAX’s relative availability.
All these highlight the uphill battle that, despite being a very good airplane which Southwest Airlines said will now deliver a 15% fuel saving over its 693 miles average stage length versus its predecessor, the 737 MAX is up and against in crawling back market share to reach parity, given the momentum the A320neo gathered in a head-start.
The new small airplane (NSA), sporting game-changing technologies such as the carbon nanotube reinforced polymer (CNRP) and new engines, would be an answer to such a growing call for a new product positioned at tomorrow’s market sweet spot of 198 seats.
This will ensure the new small airplane (NSA), while late, is worth the wait.
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