The 737 NG Replacement Study (RS), project name “Yellowstone 1” (Y-1), started in 2005 but was was put on hold in 2008. Boeing had been aiming for a replacement that would give a 20-25% improvement in operating costs and were hoping to use 787 technologies to achieve this. Unfortunately the expected improvements were only around 10%. A Boeing spokesman said in 2008 that “you can't just do a shrink of the 787; it's not as easy as that because of the different missions, higher cycles and shorter range. You can't shrink the 787 because of the systems. You need volume to handle the systems on the 787. With this study, we really need breakthroughs.”
Part of the delay was waiting for new technologies in engines, aerodynamics, materials and other systems to be developed. But part was also due to the 737NGs strong order book. Boeing Commercial Airplanes CEO Scott Carson insisted in 2008 that “the effort to develop a 737 replacement has not been abandoned, only pushed out to ensure that what results has a long market life.”
MAX -7, -8 and -9
In July 2011, some 8 months after Airbus announced its LEAP-X re-engined A320 NEO, Boeing followed suit with a re-engined 737NG in what looked like a hasty move to secure a large order from American Airlines, which was eventually split between the two manufacturers. The new family is named 737-7, -8 and -9 to harmonise the brand with the 787. The first aircraft is scheduled for first flight in 2016 and delivery in 2017.
Boeing will certify the Max series under an amended type certificate as part of the 737 family rather than go for a whole new type certificate.
Boeing claimed 600 commitments from 8 customers after 4 months.
New features:
- New 68in (173cm) CFM Leap-1B fan.
- New CFM Leap-1B custom core with 11-12% reduction in fuel burn and 7% reduction in operating cost.
- New engine nacelle and pylon will cause engines to project further forward than CFM56-7BE on 737NG.
- Updated EEC software, fuel and pneumatic systems.
- Nose gear extension of 15-20cm to give more engine ground clearance.
- Minor changes to nose wheel well to accomodate longer nose gear strut.
- Fly-by-wire spoiler system - to improve production flow, reduce weight and improve stopping distances.
- Hydraulic system redundancy to resemble 757.
- Reshaped tailcone to reduce drag.
- Widespread structural strengthening.
- Flightdeck, fuselage lengths and door configs all frozen from 737NG.
- Possible eco-improvements currently under consideration include:
- Mini-split flap
- Variable area fan nozzle
- adaptive trailing edges
- flight-trajectory optimisation
- Regenerative fuel cells
Following its launch in August this year, the re-engined Boeing 737 MAX aircraft programme has helped the Chicago-based aircraft manufacturer regain strong sales momentum seen by its arch-rival European plane-maker Airbus on its re-engined A320neo (new engine option) aircraft, garnering 700 commitments from nine airlines around the world, up from 496 commitments from five airlines received at programme launch.
12 Feb 2012 - 737 MAX Enters final phase of wind tunnel testing
SINGAPORE, Feb. 12, 2012 /PRNewswire/ -- Boeing (NYSE: BA) announced today that the final phase of wind tunnel testing, a major milestone in airplane development, will begin on the 737 MAX program next week.
"Wind tunnel testing is on the critical design path of the program," said Michael Teal, chief project engineer and deputy program manager, 737 MAX program. "Based on previous work in the wind tunnel, we are confident this final phase of testing will substantiate our predictions of the aerodynamic performance of the airplane."
Testing will begin at QinetiQ's test facility in Farnborough, U.K., where engineers will substantiate the forecasted low-speed performance of the 737 MAX on takeoff and landing. A FTSE250 company, QinetiQ uses its domain knowledge to provide technical advice to customers in the global aerospace, defense and security markets.
Testing also will be completed at the Boeing Transonic Wind Tunnel in Seattle to substantiate the forecast of the high-speed performance of the airplane.
The models used for Next-Generation 737 wind tunnel testing, with modifications made to the aft fuselage, struts and nacelles, in addition to the new engine, will be used for the tests. Test completion in mid-2012 is a major step toward firm configuration of the 737 MAX.
"This final phase of wind tunnel testing confirms that we are on track to complete our design goals and deliver the 737 MAX to customers beginning in 2017," said Teal.
The 737 MAX is a new engine variant of the world's best-selling airplane and builds on the strengths of today's Next-Generation 737. The 737 MAX incorporates the latest-technology CFM International LEAP-1B engines to deliver the highest efficiency, reliability and passenger appeal.
Airlines operating the 737 MAX will see a 10-12 percent fuel burn improvement over today's most fuel efficient single-aisle airplanes and a 7 percent operating cost per-seat advantage over tomorrow's competition.
To date, the 737 MAX has received more than 1,000 orders and commitments from 15 customers.
Article:
At the same time Boeing said it has chosen a 68-inch fan size for the aircraft’s CFM International Leap-1B engine, which, combined with improved aerodynamics through a revised 787-styled tail cone design, will deliver a 10%-12% fuel burn saving over the existing industry workhorse 737 NG (next-generation), as well as a 4% lower fuel burn per seat and a 7% lower operating cost versus the competing A320neo. “The 737 is a more efficient, lighter design and requires less thrust than other airplanes in this class, which is important because weight and thrust have a significant effect on fuel efficiency and operating costs. With airlines facing rising fuel costs and weight-based costs equating to nearly 30% of an airline’s operating costs, this optimised 68-inch fan design will offer a smaller, lighter and more fuel-efficient engine to ensure we maintain the current advantage we have over the competition,” Boeing 737 chief programme engineer John Hamilton said.
Boeing said the firm configuration of the 737 MAX will be finalised in 2013, followed by its first flight and first delivery in 2016 and 2017, respectively.
When designed in the 1950s, the close proximity of the Boeing 737 to the ground enabled the aircraft and its successors thereafter to shorten their turnaround times. Ironically, the very same ingenious design became a challenge for the airframer when the decision was made to launch the re-engined 737 MAX with bigger and more fuel efficient CFM Leap-1B engine. As a result of the ground clearance constraint, which stands at 83 inches (211 cm), this prompted Boeing and CFM to opt for a customised core for the 737 MAX’s engines with either a 66-inch (168 cm) engine fan size or a 68-inch (173 cm) one. Engine fan size is important for an engine as it drives the propulsive efficiency and bypass ratio which have an impact on its specific fuel consumption (SFC). Every inch increase in the fan size generally leads to a 0.5% reduction in the engine’s fuel burn. However, a bigger engine also brings more drag and carries more weight, which negatively impacts on an engine’s specific fuel consumption (SFC). Boeing contends that the 68-inch engine fan size is the “sweet spot” which balances between fuel burn saving, weight and drag of the engine. “[The] 68 [inch fan size] is really a sweet spot for us, a sweet spot in terms of fuel burn, drag on the airplane and also the additional weight added to the airplane. We did not just look at the engine, we looked at it as an integrated solution. Fan size is important, bypass ratio also drives weight and drives drag, I think we have made the right decision for us,” Boeing Commercial Airplanes (BCA) president and chief executive Jim Albaugh said at a Goldman Sachs Global Industrials Conference in New York on 3rd November.
In a teleconference with the media on the same day, Boeing 737 chief programme engineer John Hamilton explained that the weight of the airplane itself also drives the thrust requirement of the engine and therefore it plays a role in the engine fan size decision as well. “The 737-900ER is 10,000 lbs lighter than the A321. If you look at the operating weight per seat, our -900ER is nearly 50 lbs lighter per seat and so there is a much better structurally efficiency that goes into the 737 design than into the Airbus design,” Hamilton asserted. “Weight drives a lot of cost into an airline’s operation. In addition to the fuel that it takes to lift that weight off the ground and carry it to the air, it also plays a part into maintenance cost and landing cost as well as the thrust requirement for the engine. And so Airbus on an A321 has to put 32,000 or 33,000 lbs of thrust on there versus -900ER it is only 26,000 lbs or 27,000 lbs, so a lot lower thrust requirement on the 737 programme. “Today our engine is 7 inches smaller than the Airbus and yet we have a lower operating cost than the Airbus product. Again this gives back to the structural efficiency of the airplane and the higher thrust requirement and the higher maintenance cost that the Airbus engine requires. As we size up the equivalent inch on the [737 MAX], Airbus is going to have to size up to 78 [inches on the A320neo's CFM Leap engine] to provide the same sort of efficiency,” Hamilton asserted. “Both the fuel saving that comes from the engine as well as the drag associated with that engine as it flies through the airspace. And so you can think of a 78-inch engine is kind of like your meck truck driving down the road and a 68 [inch engine] is being a lot leaner and less drag on the engine and also the weight of the engine offsets the benefit as well,” Hamilton asserted. “So when you look at drag, fuel efficiency, and the weight the 68-inch fan is really the right optimum solution for the 737 airplane going forward,” Hamilton emphasised.
Airbus disputed this claim, with the spokeswoman at its North American unit Mary Anne Greczyn saying “if a smaller fan engine were to generate the appropriate level of efficiency, we could have easily incorporated that, since we are not constrained as our competitor”. “The A320neo family”, she added, “is designed to benefit from the aircraft’s inherent advantage”.
Meanwhile, Boeing has opted to lengthen the nose landing gear of the 737 MAX to allow “better optimisation” to take place, which is likely to necessitate the relocation of the narrowbody aircraft’s electronics/equipment (E/E) bay without a nose blister fairing. “We can put a 68-inch fan on the airplane without changing the nose gear but we allowed our designers to remove that constraint to see if they could further optimise the engine on the airplane and we believe there is a little better optimisation that will occur when we allow the nose gear to float up a little bit,” Boeing 737 chief programme engineer John Hamilton said. “Today the nose gear [on the Next-Generation 737] is actually slightly tilted down and so today’s jetways, today’s airstairs are not going to be affected by the change,” Hamilton explained. “We understand the nose gear design and we will be finalising that in the months ahead,” Hamilton added. According to sources Boeing is favouring an 8-inch extension in the nose landing gear, despite the ongoing evaluation on a 6 to 8 inches lengthening. “The changes we are going to do are simple, and the lengthening of the nose gear is 6-8 inches,” Boeing Commercial Airplanes (BCA) president and chief executive Jim Albaugh said.
While the main driver of the 10%-12% fuel burn saving remains the new CFM Leap-1B engines with a new strut that places the engine in a position much forward than the existing 737 NG (next-generation), there will be design changes involving aerodynamics, software, the design of the winglet and more. For instance, the most distinctive aerodynamic change featured in the artists’ renderings of the 737 MAX has been the adoption of a 787-styled tail cone, which will deliver better aerodynamics in the airflow through the empennage, thereby reducing drag of the airplane. “It is more of the aero-line change in the back and so we have learned a lot with the 777 airplane and the 787 design using computational fluid dynamics. We know we could create a little more laminar flow in the back of the airplane and so it is really changing some of the aero-line back there,” Boeing 737 chief programme engineer John Hamilton explained.
Boeing has offered a 737 MAX featuring 777-styled raked wingtips to its customers, which will improve payload/range capabilities of the airplane and a marginally better fuel burn. “Things like the winglets are in our trade space and we will continue to work with API and doing studies internally to understand where can we get a little more efficient on that,” Hamilton commented. “Just an economic of view, we went with the raked wingtip on the P-8 more because of the mission it flies, not necessarily because of its efficiency, because we had to keep certain characteristics in check,” Hamilton said. The Boeing 737-800 has a wingspan of 35.8 metres (117.5 ft) with a blended winglet by Aviation Partners Boeing Inc. which is 4-feet wide at the base, whereas the P-8A Poseidon, the US Navy’s anti-submarine and reconnaissance aircraft featuring a 777-styled raked wingtip, has a wingspan of 37.64 m (123.6 ft). Should Boeing adopt the same design of the P-8A Poseidon’s raked wingtip, the dimension of the raked wingtip would put the 737 MAX into the Airplane Design Group (ADG) 4 instead of the ADG 3 that the 737-800 is currently in, which requires gate type B instead of gate type A at airports, according to US Federal Aviation Administration’s (FAA) documents. The FAA defines Group 3 aircraft as those with a wingspan between 79 and 118 feet whereas the Group 4 aircraft as those with a wingspan between 118 and 171 feet. Nevertheless the growth in the 737 MAX’s wingspan is insignificant which is unlikely to affect its airport compatibility at most US and European regional airports.
Boeing say a laminar flow engine nacelle on the 737 MAX’s CFM Leap-1B engines, similar to the one found on the company’s revolutionary 787 Dreamliner which reduces drag and improves fuel burn, is very likely to be featured. In addition, Boeing is currently studying the variable area fan nozzles (VAFN) for the 737 MAX, which Boeing’s Continuous Lower Energy Emissions Noise (CLEEN) programme with the US FAA already includes, along with the adaptable trailing edges, could potentially deliver a fuel burn saving of up to 2%. A variable area fan nozzles (VAFN) relies on a FADEC (Full Authority Digital Engine Control) to protect the fan against fan fluttering during take-off and thrust-reversing operations in the open position and could cut 2% of engine fuel burn in the widest position during cruise in the closed position. The VAFN can also reduce noise in the intermediate position during climb. Pratt & Whitney (P&W)’s PW1524G PurePower engine, selected to power Bombardier’s CSeries aircraft, already features the VAFN system and the first production unit of the VAFN system will be delivered this month followed by flight tests in early 2012, whereas the ecoDemonstrator flight test programme on board an American Airlines (AA) Boeing 737-800 will begin in August or September 2012. However, both Boeing sources say the type of hybrid laminar flow control (HLFC) being studied is a passive and retrofittable one which only yields a 0.5%-1% reduction in drag, adding a last decision on HLFC is not expected anytime soon. The same sources say the VAFN decision remains undecided pending the outcome of the ecoDemonstrator flight test programme as well as other considerations.
On the other hand, Boeing has decided to adopt a partial fly-by-wire system on the 737 MAX’s spoilers, which Boeing hopes will save weight and improve the production system of the aircraft, in light of the strengthening of the 737 MAX’s wings and fuselage to accommodate the larger and heavier engine that adds weight to the airplane. “We are also taking a look at some minor system changes, one of them is fly-by-wire spoilers so going to fly-by-wire spoilers put some as it saves weight from the airplane and it will improve the production flow in the factory and it allows us to improve stopping performance with the airplane as well,” Boeing 737 chief programme engine John Hamilton said. “The system that we are looking at to put on the MAX is really kind of a 757-type system architecture and simplifying it down, it does not require as much redundancies as if you are going to put fly-by-wire on your primary flight controls like ailerons, elevators and so the weight impact of going to a totally fly-by-wire system is what is needed to do just for the spoilers. It is going to be a weight saving for us,” Hamilton added.
“We will strengthen the wing for that higher load from the engine, there might be some localised structuring strengthening we need to do with the fuselage, but pretty minimal there, we talked about fly-by-wire spoilers, those are going on, there are some minor system changes that associated with the engine change that we need to make, the engine computer essentially the software that drives that we are going to need to change,” Hamilton elaborated. Coupled with the 777-styled raked wingtips, the partial fly-by-wire system is going to redistribute loads inwards and could enable Boeing to increase the maximum take-off weights (MTOWs) of 737 MAX 9 to make it a closer 757 replacement. “The 737 today can fly roughly about 95% of the mission that the 757 flies today so the 737-900ER is a really good airplane for that. Now are we going to get the range that the 757 has? We are talking with our customers but we are not going to get out the 4,000 nautical miles range and the payload the 757 flies today,” said Hamilton, Boeing spokeswoman Karen Crabtree said “the MTOW for MAX 7, 8 and 9 is currently being studied to meet market requirements” while clarifying “minor system changes such as fly-by-wire spoilers offer weight savings for the airplane”. Upping the maximum take-off weight (MTOW) of the 737 MAX 9 version would bode well for Boeing to vie for the 757 replacement orders, as the 757 operators are starting to decommission the uniquely capable single-aisle airplane, with Delta Air Lines ordering 100 Boeing 737-900ERs and American Airlines (AA) retiring 11 Boeing 757 next year. A better payload/range capabilities of the 737 MAX 9 are going to match the 3,900 nautical miles (nm) range of 757-200 with winglets better when compared to the A321neo and 737-900ER whose ranges are at 3,680 nm and 3,265 nm, respectively. “The 737 MAX 9 [has] about 5% better operating economics for its seat-mile economics and its trip costs will be about 6% better [than the A321 neo]. Its operating economics are significantly better,” Boeing Commercial Airplanes (BCA) vice president (VP) in business development and strategic integration Nicole Piasecki was quoted back then.
With Boeing embarking on different concepts to reduce the drag and improve the fuel burn of the 737 MAX, one may question whether these initiatives will deliver additional fuel burn saving over the promised 10%-12% one. However, Aspire Aviation‘s multiple sources at the world’s second-largest aircraft manufacturer expect the laminar flow engine nacelle, variable area fan nozzle (VAFN) and its raked wingtips to deliver a combined less than 1% additional fuel burn saving, as they point out the existing 737-800 is already a highly-efficient design. “The 10-12% fuel efficiency improvement includes new engines and other improvements,” clarified Karen Crabtree, a Boeing spokeswoman. “We will provide additional details [on additional fuel burn savings] as we work to finalise the configuration,” Crabtree added. Complicating the fuel burn analysis is the industry speculation that the specific fuel consumption (SFC) of the CFM’s Leap engine is already falling behind by 2%-3%, which may necessitate adding additional stages in the engine’s low pressure compressor (LPC) and high pressure compressor (HPC) to recover the lost grounds, thereby increasing the development cost of the engine and possibly increasing its maintenance cost as well. While General Electric (GE) has a proven, strong track record on delivering its commitments through performance improvement packages (PIPs), the 15% fuel burn saving promised by the CFM Leap engine, whose fuel burn saving is likely to be 13%-14% on the Leap-1B’s smaller fan size, coupled with the 2%-3% fuel burn miss and around 2% of installation effect owing to the strengthening of the wings and fuselage required, this puts the 737 MAX’s fuel burn saving in the advertised 10%-12% range, after factoring in the aerodynamic improvements and other design changes. As a result, Aspire Aviation believes the 737 MAX’s fuel burn to be in line or slightly worse than the A320neo (new engine option) family aircraft. In fact, an AirInsight analysis finds the 737 MAX 8 being 4% more fuel efficient than the A320neo on a per seat basis, whereas the A319neo and A321neo have a 3% and 2% better fuel burn per seat than their Boeing counterparts, respectively. Nonetheless the fuel burn issue is subject to change as both the CFM Leap-1B engine and the 737 MAX are being defined and their designs evolve before being finalised. “We will continue to work with CFM and continue to customise the engine that is unique to the 737 and really optimised the engine so you get the right bypass ratio, the right core thrust that serves the 737 and it is customer-based as well as it comes while maintaining the remarkable maintenance advantage and reliability that the CFM engine has today,” Boeing 737 chief programme engineer John Hamilton said. “We are working closely with CFM and understanding what technologies are available today that are proven that we can use with the engines to optimise it, including the number of blades you need, the size of the core, the configuration of the core. “What is going to be available to support the entry into service and so if there are technologies there that we can take advantage of CFM and Boeing agree that make sense, we will consider that,” Hamilton added.
As the 737 MAX is still some time before its detailed configuration is finalised in 2013, Boeing and CFM will continue to evaluate different options for the airplane and choose the options that bring the most value to its customers. And there is no doubt that the 737 MAX will become popular, as airlines strive to slash costs in light of the persistently high oil prices. “We expect several hundred more commitments soon. Some customers they are waiting to hear more about what the configuration and the performance of the airplane,” Boeing 737 chief programme engineer John Hamilton said. At press time, Boeing Commercial Airplanes (BCA) president and chief executive Jim Albaugh revealed that the Chicago-based airframer has received more than 700 commitments and it expects to start converting those commitments into firm contracts by year-end or early 2012 as Boeing offers performance and contractual guarantees. “We have got commitments for over 700 aircraft so we think the customers like what we are doing and we continue to talk to additional customers,” Albaugh said. More importantly, perhaps, is that Boeing should manage the programme risks prudently while evaluating different options, including numerous design changes that promise to deliver further fuel burn and operational cost savings, but may also increase the complexity of the re-engining programme. After all, following the more than 3 years of perennial delays on its game-changing 787 Dreamliner as well as more than 1 year of delay on the 747-8 revamped jumbo jet programme, Boeing can ill-afford to execute disastrously on a brilliant vision like the bumpy ride seen on the 787. What is more, Boeing has indicated that it intends to deliver the 737 MAX at an earlier timeframe than the 2017 entry into service (EIS) target and that it is likely to launch the double-stretched 787-10X as well as an upgraded 777-8X and 777-9X by the end of the decade (“New Boeing 777X likely to be a highly efficient derivative“, 14th Sep, 11). This makes a smooth execution on the 737 MAX all the more important to prevent a moment of déjà vu of the 787 fiasco from ever happening again and draining its engineering and financial resources while causing the development costs of the 737 MAX to creep up. “We want to under-promise and over-deliver,” Boeing Commercial Airplanes (BCA) chief executive Jim Albaugh conceded. “I think we learned our lesson on the 747 and the 787: Do not make promises you cannot keep,” Albuagh commented. Indeed, Boeing learned a lot on the 787 and 747-8 programmes the hard and painful way and therefore it is paramount for Boeing to keep the programme cost of the 737 MAX in check, which analysts have put at US$1-2 billion in average. With these design changes which Aspire Aviation thinks constitute significant advancements for the 737, the programme cost could potentially top US$3-4 billion. All in all, the 737 MAX aircraft programme is the right step in maintaining the existing duopoly between Airbus and Boeing with a minimal investment while enabling Boeing to have the strategic advantages in the widebody arena in the 787-10X and 777X decisions. With an eventual replacement in the form of NSA (new small airplane) featuring composite fuselages and wings being shifted to the right on timescale to late-2020s, as the second and third-generation out-of-autoclave (OoA) composite manufacturing technologies mature and find their ways into wider aerospace applications, the 737 MAX is going to serve Boeing well and deliver satisfactory returns during this period of time.
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History & Development of the Boeing 737 - Max
