Airlines satisfied with 787 engines despite efficiency miss

By: Stephen Trimble published in flightglobal.com, Nov 17 2014

If one of today’s market fashions becomes permanent, the Boeing 787 could be the last commercial widebody aircraft that offers buyers a choice of engines from competing suppliers – in this case the GE Aviation GEnx-1B or the Rolls-Royce Trent 1000.

This increasingly rare engine competition has delivered two propulsion systems with reliability levels well above the average at the aircraft level.

At the same time, it has so far failed to produce a turbofan engine designed by either competitor that meets Boeing’s original promise of a 10% reduction in specific fuel consumption.

Additionally, competitive pressures have not provided airline customers with immunity from brief operational crises with both engines, in one case an operational restriction that still continues.

Both engines boast despatch reliability levels above 99%, the benchmark Boeing is still seeking to claim for the aircraft as a whole.

“The engines are operating flawlessly,” says Zemene Nega, vice-president of maintenance, repair and overhaul for Ethiopian Airlines, a GEnx-1B customer.

It has not always been so. In July 2012, All Nippon Airways, a Trent 1000 customer, grounded five 787-8s after Boeing informed it of a potential problem in the gearbox. Crown gears had corroded faster than expected in endurance tests on the ground, causing damage to the engine. R-R traced the problem to a manufacturing process change by gearbox supplier Hamilton Sundstrand. It was corrected within weeks.

The GEnx-1B became the focus of the next engine crisis. A decision by GE Aviation to adopt a new lead-free coating on the fan mid-shaft backfired with explosive results. The coating caused the component to corrode faster in humid climates. In late July 2012, a GEnx-1B on board a newly assembled Air India 787-8 sustained a contained failure. GE reverted to a previous lead-based coating, and the problem disappeared.

Rolls-Royce‘s next move is to deliver the Trent 1000-TEN upgrade in mid-2016

Rolls-Royce

A longer-term problem for GE Aviation is a relatively new phenomenon called ice-crystal icing. Liquid water is not present above about 22,000ft, so airframe icing is never a concern at cruise altitudes for a turbofan-powered widebody aircraft.

However, meteorologists have recently discovered the presence of ice crystals at even higher altitudes, especially in tropic latitudes. In massive storm concentrations stretching 100km (62mi) across, convection forces can carry ice crystals the size of a grain of flour to cruising altitudes above 30,000ft. The crystals bounce off an aircraft’s skin, but can be ingested into an engine. It is believed that crystals land on a warm blade and begin to melt, which attracts other crystals to stick to the blade. Eventually, enough ice develops on the blade to cause damage downstream when it sheds.

The phenomenon is particularly acute on the GEnx engine. On its predecessor, the CF6, the ice build-up would most often shed as the aircraft descended. The GEnx experiences the ice shedding problem at cruise altitude, leading to in-flight engine shutdowns. As a result, the US Federal Aviation Administration issued an airworthiness directive last year requiring airlines to steer 787s at least 50mi wide of major storm concentrations.

For some airlines, the restriction is an annoyance but not a network issue. Japan Air Lines, however, has pulled the 787 off three routes originating in Tokyo: Bangkok, Delhi and Singapore.

By contrast, the Trent 1000 engine faces no such operational restriction, says R-R project director Gary Moore. Fortuitously, the three-spool architecture of the Trent engine family happens to be less prone to ice crystal build-up inside the core. The intermediate compressor section, which is absent in the GEnx design, rotates at a higher speed, making it more difficult for dangerous quantities of ice to build up on the blades.

“We don’t have this problem,” Moore says. “It is just a very clear difference in the two engines.”

Another clear difference between the engines is the order split. So far, 787 customers have chosen the GEnx-1B over the Trent 1000 by a nearly two-to-one margin, with 17% of the order backlog still unspecified.

R-R places a couple of caveats on the GEnx-1B’s strong start. First, not all airline decisions have been the result of a competition. When given the chance to compete, the Trent 1000 has claimed nearly half of the orders, Moore says. Moreover, the Trent 1000 is starting to gain some momentum. In the last 19 engine selections, the Trent 1000 has won orders 11 times, he says.

R-R’s next move is to deliver the Trent 1000-TEN upgrade in mid-2016. GE has acknowledged that the GEnx-1B misses, by 1-2%, Boeing’s original specification for reducing specific fuel consumption. The Trent 1000-TEN – packed with technological improvements inherited from the Trent XWB – is still aimed at achieving the 787’s original fuel-burn target.

“We’re targeting the original spec that was put upon the airplane,” Moore says. “You don’t spend this level of investment to think we’re not going to get there. We’re going to get there.”

From vision to world’s most successful commercial engine: 40 years of CFM

By: MURDO MORRISON published in flightglobal.com, Sep 29 2014

It began with a casual encounter in Paris and has flourished into a 40-year marriage with a remarkably successful offspring. CFM International – the union between the USA’s General Electric and France’s Snecma – is heading towards production of its 30,000^th engine. But the joint venture’s start, back in the 1970s, was stuttering. The first years of the transatlantic relationship were fraught with cultural and language challenges, questions over the structure of the enterprise, and concerns within the US administration over transfer of sensitive military technology.

But these were nothing compared with a much more pressing concern as the decade ended. Five years after its creation, and eight years from the informal 1971 meeting at the Le Bourget show where the GE and Snecma presidents had begun their courtship, CFM International had one product in the market – a 10-tonne, 20,000lb-thrust (89kN) engine – but no production contract. The CFM56looked a gallant failure and CFM may have been headed for the divorce court. Had that happened, the commercial airliner market would have turned out very differently.

The marriage was saved by Boeing. The airframer had chosen the CFM56 to power a version of the ageing 707 (later adopting it to re-engine its military tanker sibling, the US Air Force’s KC-135. Today the air force is CFM’s single biggest customer). A re-engining effort for another venerable, four-engined type, the Douglas DC-8, bought the programme more time. But it was Seattle’s decision to commission the 18,500lb- to 23,500lb-thrust -3 version of the CFM56 for its 737-300 in the early 1980s that was the breakthrough for an engine that had all along been intended to power a new generation of twin-engined narrowbodies.

The Leap-1A is one of the three variants of the newest CFM engine

CFM

It was the start of arguably the most commercially successful pairing in aerospace. The CFM56 went on to exclusively power the next generation 737 from the 1990s and its Leap successor will be the sole engine type on the 737 Max. Of almost 27,000 CFM56 engines, some 14,000 have been fitted to 737s. CFM’s narrowbody dominance was consolidated later in the 1980s when Airbus selected the 22,000lb- to 25,500lb-thrust -5A to compete with the International Aero Engines’ V2500 on its new A320. Since then, more than 7,500 of the CFM engines have powered Airbus narrowbodies.

The engine found another application too in the early 1990s, this time on a widebody. The CFM56-powered Airbus A340 made its service debut in 1993. While sales of the quadjet did not set the world on fire, CFM had the benefit of exclusive supply, powering all 246 of the -200/300 variants delivered.

With the arrival this decade of new versions of the 737 and A320, as well as a flurry of new narrowbody and large regional contenders from Bombardier, China’s Comac, Embraer, Russia’s Irkut and Mitsubishi, the battle in the ever-growing single-aisle market has taken on a new dimension. What began as the TECH56 technology studies in the late 1990s developed into the LEAP56 (leading edge aviation propulsion) project and eventually the launch of the Leap engine for new generation narrowbodies in 2008.

While it seemed likely that Boeing would retain CFM as solus supplier on any new narrowbody, it was Comac that was first to select the Leap when it launched its clean-sheet C919 narrowbody, in November 2010. The following month, Airbus – quicker off the mark than Boeing with its decision to re-engine its top-selling product as the A320neo – also chose the new CFM engine, albeit as an option alongside Pratt & Whitney’s PW1000G PurePower geared turbofan, which emerged around the same time as the Leap and was chosen initially to power the Bombardier CSeries.

In 2011, after much speculation over its future single-aisle strategy, Boeing announced that it would be re-engining the 737 rather than launching an all-new narrowbody, and the Leap-1B would be its sole powerplant. Seattle’s loyalty came as little surprise. The airframer said it had been working with its propulsion partner of 30 years on configurations for both re-engined and possible new types. With just under 6,000 CFM56-powered 737s in service, a global maintenance, repair and overhaul network for the legacy engine, and hundreds of content airline customers, it was the low-risk choice.

Now with a backlog of more than 7,800 Leap engines – as well as some 4,500 CFM56s – the priority for the latest CFM president, Frenchman Jean-Paul Ebanga, seems less about securing new business and instead managing what he calls “one of the most complex supply chains in the world, but also one of the best prepared to cope with this challenge”. CFM boasts that it has never delayed an airliner delivery, and – despite a production ramp-up from 1,000 engines in 2000 to around 1,550 this year and 1,800 by the close of the decade – it is not a record Ebanga plans to let slip.

The Leap-1A for the Airbus A320neo family, which has been undertaking ground testing since September last year, is expected to be certificated in the first quarter of next year, ahead of the first flight of the Leap-powered A320neo. The -1C for the C919 is due to enter flight testing this autumn, although the engine is not expected to be certificated until the end of next year. The Leap-1B for the 737 Max was fired up for the first time at Snecma’s Villaroche plant in June and is expected to be handed over to Boeing as a certificated engine in mid-2016.

Ebanga’s team have to handle not only a rapid ramp-up, but a transition from the CFM56 to the Leap starting in 2016. Although the CFM56 product developed significantly between the original CFM56-2 and today’s -5B and -7B variants, the Leap represents a huge advance in technology and will require considerable new infrastructure. Most of the industrial investment is in place, he says. A new fanblade plant will open in France in a few months, ground was recently broken on an assembly plant in Indiana and a final assembly line in Villaroche is “very advanced”.

As with the CFM56, Snecma and GE manage their own supply chains for the elements of the Leap they are responsible for – Snecma the low-pressure turbine and fan, and GE the high-pressure compressor, combustor and high-pressure turbine that make up the engine’s core. Ebanga describes the global supply chain – that includes company owned factories from North Carolina to China as well as dozens of smaller suppliers – as a “beehive” with every member of the community focused on just-in-time manufacturing and quality.

“The Leap engine is result of hundreds of thousands of daily actions across the world, everyone producing parts to the right standards and at the right time, so that in the end you have an engine that is just produced by CFM,” he says. Ebanga admits that moving from a testing and certification regime to mass production of a new product in just a few months will be an “unprecedented challenge” , but says that “by the time we get to serial production we will have all the risks back to the level we want.”

Supporting the engine in service is also a challenge. The popularity of the CFM56 has created a global network of maintenance centres, run by Snecma, GE and third parties. But repairing the Leap – with its technologies such as 3D-woven, resin transfer moulding carbonfibre fan blades – is a trickier proposition for traditional shops. It led CFM in 2008 to launch its own unified service network, and seven in 10 Leap engines ordered come under this scheme. Ebanga says one of the biggest achievements of CFM has been transitioning from a programme-focused venture at a time when “the services business did not exist” to one where CFM can present “one face to the customer for everything”.

The agreement between GE and CFM has been renewed several times since 1974 and the latest contract signed in 2008 lasts to 2040, when the Leap will be a mature engine and production of CFM56 engines, even for spares, will have all but stopped. However, just as the CFM56 engine was improved on, so too will the Leap, insists CFM. “We have hundreds of developments in our pipeline,” executive vice-president Cedric Goubet said at July’s Farnborough air show. The current engine is just “the first step in a new generation of technologies” being worked on by both partners.

In an era of high fuel prices, shaving every possible kilogramme of weight while improving efficiency remains a holy grail for engine makers, and with GE and Snecma both making advances in composite technologies and additive manufacturing, this will be a key battleground. CFM vice-president Allen Paxson, also speaking at Farnborough, predicted that increasing use of ceramic matrix composites and additive manufactured processes – currently used for fuel nozzles – will become widespread in the coming years.

The question remains as to whether the big airframers will be content with iterative improvements such as these, or will look to a breakthrough technology such as open-rotor to replace their current narrowbodies. Rolls-Royce – absent from the narrowbody market since it pulled out of the IAE consortium, unhappy with partner P&W’s decision to pursue a geared turbofan design – has said it wants to re-enter the market in the 2020s. Snecma has been pursuing an open-rotor concept which it plans to flight test on an Airbus A340 in 2019.

Any realignment looks unlikely, however, until the 2030s at least. Would-be challengers to the Airbus/Boeing duopoly – Bombardier, Comac and Irkut – have all opted for a CFM or P&W engine. Until then, it will be hard for any new propulsion player to break in and the CFM agreement prevents GE or Snecma from going it alone or joining with anyone else in that segment, even if they wanted to. If anything, says Ebanga, the development of the Leap has pushed the two partners even closer together.

Improved fuel-burn allowed carriers such as Ryanair to increase fleet utilisation, says Ebanga

Boeing

Back in 1974, a French state-owned enterprise and an American corporation, both with a heritage in military engines, might have seemed unlikely candidates to alter the face of short-haul commercial aviation, a segment utterly dominated by Pratt & Whitney at the time. But CFM has been a “unique organisation”, says Ebanga. “We brought in a new level in terms of fuel burn and reliability. This enabled guys to think about higher utilisation of these assets, and instead of flying twice or three times a day, Southwest and Ryanair were able to fly six or seven times. I’m not saying the CFM56 was the only reason they did this, but it was a key enabler in this huge change in aviation over the past 30 years.”

Rolls-Royce harvests a decade of research for new engine projects

By: MURDO MORRISON published in flightglobal.com, Oct 1 2014

As Rolls-Royce prepares to build and begin testing next year its seventh member of the Trent family – the 7000 for the Airbus A330neo – it is harvesting the fruits of a decade’s worth of research and development projects into two studies that could form the basis for a new generation of widebody – and even possibly narrowbody – engines in the 2020s.

The UK propulsion specialist wants to develop technology and products that will secure a 50% share of the twin-aisle market, as well as – perhaps more ambitiously – help it break back into the growing single-aisle sector, vacated when it abandoned the International Aero Engines consortium in 2012, just when a host of new narrowbody programmes were arriving on the market.

The company earlier this year revealed its Advance and UltraFan designs. Although both are far from being formal programmes, they are based on the three-shaft structure of the successful widebody Trent family, in particular the Airbus A350’s Trent XWB. R-R says they could, in theory, be ready to enter service as production engines as early as 2020 and 2025, respectively.

R-R says Advance and UltraFan are about highlighting its progress in a range of technologies, from composite fans to lower-emissions combustion systems. The company’s timescale for bringing these to market, however, means the engine studies are more than simply “what-might-be” concepts. It has already proved, or is currently testing, many of the engines’ novel elements.

The advance’s carbon/titanium fan system has been tested on a Trent 1000 at the Stennis centre

Rolls-Royce

Advance and UltraFan are not just Trents with tweaks, stresses Alan Newby, chief engineer, future programmes and technology. Although they rely on the same three-shaft architecture, the first of the two engines, Advance, will have a new core – with a larger high-pressure compressor and smaller intermediate compressor – as well as a composite fan and casing.

Other changes include an adaptive cooling system, a lower NOx combustor, “dynamic sealing” to minimise leakage and a wider use of ceramic-matrix composites. “Advance is the next generation in three-shaft engines and brings together a lot of the technologies that we’ve been working on for the past 10 years. There are a lot of differences. The HP and IP compressors are very different,” he says.

There is a clear commercial goal too. “We are getting the technology bricks in place, and when we get the call to develop [Advance] for an aircraft programme, we will,” adds Newby. “We won’t launch a programme until we have a requirement, but we think we will have de-risked all the technologies by 2015 or 2016 and be ready with a new application from 2020 onwards.”

The test or “slave” engine for many of the new core technologies is a Trent XWB, with its core removed and replaced by the trial HP and IP system. “It’s a good platform for testing. We have quite a big project team up and running on it,” says Newby. R-R has started machining components for the engine and other elements have been ordered from the supply chain.

Although the company has no plans as yet to fly the adapted Trent XWB independently, it will undertake ground tests next year. Separately, a carbon/titanium fan system, which will be used on both Advance and UltraFan, has just completed a phase of testing – on a Trent 1000 engine – at the company’s outdoor jet engine test facility at the John C Stennis Space Center in Mississippi.

While R-R plans to test elements of its Advance engine separately, it intends to build a whole engine demonstrator for the UltraFan, with a vision of it taking to the air on a flying testbed by the end of the decade. “Given the amount of changes, we would need to verify it in flight,” says Newby. “Four or five years before entry into service is when you’d want to be maturing the technologies.”

Several engines are dedicated to research

Rolls-Royce

These technologies include a variable pitch fan, with gearbox, and a high-speed IP turbine, as well as possible adaptations to the core. “UltraFan takes the core configuration we will have developed for Advance and adds a lower-speed fan,” explains Newby. “This turns at a relatively low speed, so it makes sense to add a gearbox.”

Although UltraFan retains the Trent’s three-shaft compression system, the enhanced IP turbine drives the fan via a power gearbox, allowing the LP turbine to be eliminated. The gearbox is “critical technology”, says Newby. “We have experience through our work on the JSF [Lockheed Martin F-35 Joint Strike Fighter] and elsewhere on the military side. We are not starting from scratch.”

The engine manufacturer has already allocated more than a dozen engines to the various technology projects that have led to Advance and UltraFan. Many of these have been supported with research and development funding from the EU and R-R’s “home” governments: the UK, USA and Germany.

Its ALPS study, intended to come up with a lightweight LP system, has used three Trent 1000s. The first phase of engine testing was completed in 2013 and the second has just finished at Stennis. A third Trent 1000, fitted with the composite fan, has been shipped to Tucson, Arizona, for flight testing on a Boeing 747 by the end of the year.

A second project, EFE, running since 2010, focuses on “hot end technologies” and also uses the Trent 1000. Testing on a fourth engine has just ended at R-R’s Bristol facility. A final study, ALECSYS, is about developing a “robust lean-burn combustion system” and involves flight testing two Trent 1000s converted with a lean-burn combustor in 2015 and 2016.

R-R claims that the bundle of technologies on Advance and UltraFan could improve efficiency by 20% and 25% respectively, compared with the first Trent, the Trent 700. Newby adds that the technology is scalable and could cover a range of thrusts from 30,000lb (134kN) to more than 100,000lb, a much broader band than the current family’s 53,000-95,000lb range.

However, the company is quick to point out that this does not offer a direct clue to how it might re-enter the single-aisle market in the next decade. “Scaling down is possible, and in theory these technologies could form the basis of a new narrowbody engine,” says Newby. “But this is not necessarily the route we will take.”

Rolls-Royce makes progress with Trent 7000

By: MURDO MORRISON published in flightglobal.com, Oct 2 2014

Although understandably coy before Airbus’s Farnborough announcement that it was launching the A330neo, Rolls-Royce was by July quite far along the path of finalising the design for the Trent 7000, the 72,000lb (320kN) thrust engine that will exclusively power the re-engined widebody. Rolls-Royce already has a more than 50% share of engines on in-service A330s, with its original Trent 700.

The 7000 is based on the latest iteration of the Trent 1000 for the Boeing 787, the Trent 1000-TEN, and includes features such as weight-saving blisks in the compressors and a system that integrates engine dressings into composite raft-like structures. The first engine will be built and ground tested next year. Flight test engines will follow in 2016 ahead of the first actual flight test in 2017, with entry into service slated for late 2017.

Other changes compared with the original Trent 700 for the Airbus A330 – launched in March 1995 – include a 2.84m (112in) fan, rather than a 97in one that helps double the bypass ratio to 10 and improve specific fuel consumption by 10%. “For us, basing it on the TEN makes it a very low-risk programme,” says Peter Johnston, head of customer marketing.

The bigger fan means the engine and Aircelle-designed nacelle have to be moved forwards and upwards, compared with the Airbus A330’s Trent 700, to retain the same level of ground clearance and avoid “sucking in too much dirt”, says Johnston. The big architectual difference with the TEN is a new external gearbox because Airbus’s system is different to Boeing’s.

The engine manufacturer has a full dedicated project team in place for the 7000, which can pull in expertise from both the Ten and the Trent 700 teams, he says. The engine gives R-R itself a foot in two camps too, with a competitive position – against General Electric’s GEnx – on the Boeing 787, as well as an exclusive arrangement on the Dreamliner’s new direct competitor.

GEnx misses fuel burn spec on 787, but on upgrade path

By: STEPHEN TRIMBLE, published in flightglobal.com, Sep 23, 2014

One month before Boeing returned the 787-8 to flight in May 2013 after an 18-week grounding caused by battery fires, GE Aviation quietly certificated the third major production version of the GEnx-1B, inching one of the two propulsion options for the Dreamliner closer to the promised fuel efficiency targets.

Similar to the rival Rolls-Royce Trent 1000 engine, the original Block 4 version of the GEnx-1B entered service with Air India in early 2012 several percentage points below the specification. The Block 4 standard also featured an under-performing low-pressure turbine (LPT) section that would require a redesign.

As of early September, GE had delivered 246 GEnx-1B engines, including the last 150 built to the performance improvement package (PIP) II standard. That number includes the first GEnx-1B-powered 787-9 delivered to United Airlines on 4 September, the last major certification campaign until the arrival of the 787-10 in four years.

With tens of thousands of hours and now two applications in service, GE now understands exactly how close the PIP II standard came to meeting Boeing’s specification – and it is not as close as was once widely expected.

“We’re probably off the original ‘spec’ by perhaps a little more than 1% but less than 2%,” says John How, business operations leader of the GEnx product line for GE Aviation.

Boeing

Importantly, the upgraded engines delivered after Block 4 was phased out of the production system meet contractual guarantees for airlines, How says.

“What matters to the airline customer is what they were sold by Boeing and what they were guaranteed,” How says.

Even the latest GEnx PIP-II engine installed on the United 787-9 delivered earlier this month, however, falls short of Boeing’s original promise to airlines. Judging by GE’s lead over R-R in the787 order backlog, the performance of the Trent engine has not been enough to usurp the GEnx.

The Trent and GEnx performance shortfalls were apparent well before either version was delivered to a customer. A leaked Airbus dossier on the 787 in 2008 included the prediction that both engines would miss the specification by 2-3%. As the original Trent 1000 and Block 4 entered service, the 3% shortfall became the baseline estimate used by both companies.

GE and R-R then designed a series of performance upgrades to reclaim the specification target. R-R has already rolled out Package B and C standards, with the final 1000-TEN configuration scheduled to appear in 2016.

GE, meanwhile, followed the Block 4 standard with the PIP 1 design, which included a revised LPT. GE had introduced lightweight titanium-aluminide blades in the LPT section of the GEnx engine, believing it could reduce the blade count significantly and lower the weight of the engine compared with the preceding GE90.

That estimate proved to be too aggressive by about 30% of the LPT blades that would ultimately be required to manage the airflow. The PIP 1 programme corrected the error with a more robust LPT blade count.

GE advertised that the PIP I would reclaim 1.4-1.6 percentage points of the 3% performance shortfall from the specification. A second upgrade – the PIP II design – was supposed to push the performance to nearly match Boeing’s original fuel burn target. With the LPT improved by the PIP 1 programme, GE now focused on improving the high-pressure compressor section in the PIP II design.

In previous statements, GE had indicated the PIP II configuration was coming within 1% of the specification target for fuel burn efficiency. That estimate proved illusory, however. GE has now recalculated the actual performance results, with the new figures showing the Block 4 missed the specification by 4-5%. With the PIP II standard, fuel burn efficiency improves by 3 percentage points, but remains 1-2% shy of the specification.

GE

GE officials emphasise that the performance will continue to improve as the new upgrades enter the fleet. They point to the record of the GE90-115B, the engine that powers the 777-300ER. That engine also entered service slightly below Boeing’s specification for fuel burn. Ten years later, it is now running more than 3% above the specification, according to GE’s numbers.

Despite the shortfall, there is no “PIP-3” version being proposed for the GEnx-1B. Instead, GE will introduce improvements gradually leveraging engine development programmes launched after the GEnx was unveiled in 2003 with a then-state-of-the-art 45:1 compression ratio. GE is currently testing a compressor section for the GE9X that will power the 777X with a 61:1 compression ratio.

Key enabling technologies, such as ceramic matrix composites, have already been tested in the core of a GEnx engine, as part of GE’s campaign to mature the technologies for the CFM InternationalLeap engine and the GE9X.

As GE works to improve the GEnx-1B’s fuel performance, the company is also looking at adding more thrust capability. The engine is already able to produce 78,000lb thrust (111kN) at sea level, a power reserve well beyond the needs of the 787-8 and 787-9. It is expected, however, to allow the 787-10 to take off with a full payload at high-altitude runways or in very hot weather. The standard rating for the 787-10 is 76,000lb thrust, with a 2,000lb thrust margin for “high-hot” conditions.

GE is now studying an even more powerful version of the GEnx, which would raise maximum thrust at sea level to 80,000lb. Although Boeing has not publicly discussed a requirement for such an engine -– perhaps to power a high-gross-weight version of the 787-10 – GE is preparing “in case the airplane needs increased thrust”, How says.

An increase in thrust often involves a wider inlet diameter, as more airflow is needed to produce more power efficiently. But there are ways to avoid a wider engine exterior. The PIP-II configuration, in fact, includes a 12.7mm (0.5in) wider flow path, without changing the exterior diameter.

“Thrust increase always involves more airflow,” How says. “As to whether or not we would need to increase the diameter of the fan, that’s not really decided.”

More efficiency and more power are not the only items on the list of improvements for the GEnx-1B engine.

Boeing and GE are close to clearing one of the most bothersome operational restrictions for certain operators, such as Japan Air Lines. The GEnx-1B has proved susceptible to a phenomenon unique to tropical clients called ice crystal ingestion. In tropical latitudes, small ice crystals can form at high altitudes, potentially causing damage to the engines. The GEnx-1B is currently restricted from flying within 50nm (93km) of weather in which ice crystals are able to form. As a result, JAL has replaced 787s with 777s on two routes to Vietnam and India.

“We think by the end of October Boeing will be able to issue a revision to that flight restriction, increasing the altitude limit significantly,” How says.

The solution to the problem requires no changes to the turbo machinery. Instead, GE has reprogrammed the software controlling the variable bleed valves located in front of the compressor section. These valves are normally opened on take-off or landing, siphoning potentially damaging objects sucked in by the fan into the bypass flow. The reprogramming allows these valves to open when conditions suggest ice crystals are forming on the blades.

Late Engine Issue May Cause A320neo First Flight Delay

By: Guy Norris and Jens Flottau , published in aviationweek.com , Sep 12, 2014

Airbus and Pratt & Whitney are believed to be tackling a late-developing certification issue with the PW1100Ggeared turbofan in an attempt to stave off the looming threat of a delay to the first flight of the re-enginedA320neo.

The aircraft manufacturer, which declines to comment, has targeted September for first flight of the A320neo with the Pratt engine but, according to industry sources, may be forced to delay this because of unidentified concerns related to the PW1100G. Airbus had hoped to fly the test aircraft, MSN6101, as early as Sept. 5. However the modified A320neo, which was pictured taxiing under its own power at Toulouse on Sept. 1, remains on the ground.

The Pratt-powered A320neo is the first of two re-engined variants to be developed and will be followed by the CFM Leap-1A powered version which is due to enter flight test in 2015.

The exact nature of the problem remains unclear, though industry sources indicate the hurdles to first flight are associated with the last set of fan-related certification tests that Pratt was conducting in the run-up to certification.

Pratt declines to comment specifically on the allegations of any certification or testing-related concerns. The company says “we are working closely with Airbus as we prepare for first flight. It is premature at this time to say exactly when that will occur. We will provide more details as they become available.” MTU Aero Engines, a key partner on the PW1100G program, deferred questions to Pratt & Whitney.

Sources within the supplier and customer community prefer to remain vague. One senior executive of a major A320neo customer confirms information that there has been an issue during testing. The fact that customer representatives know about it indicates that Pratt & Whitney has been briefing key industry players.

Although the PW1100Gs underwent oil system checks to verify that none of the recent seal failures which occurred with the PW1500G on the Bombardier CSeries would appear on the A320neo, the Airbus engine development has otherwise proceeded virtually to plan until now. The first two engines for the compliance aircraft were delivered on schedule to Airbus, and Pratt has at least 28 engines in build or already in the test program.

As of early July the engine maker was progressing rapidly through the final items on the check list for European JAR-E and U.S. FAR Part 33 engine certification, with high and low pressure compressor stress tests, 150 hr. block tests, water and hail ingestion and a final brace of bird strike tests yet to be completed. Another major final test remaining was the fan blade out test, which Pratt was confident of passing successfully having already passed an earlier evaluation on a test rig.

GE9X engine for the 777X to feature fewer, thinner composite fan blades

Published in compositesworld.com, September 2, 2014

 

GE Aviation (Evendale, Ohio, USA) reported on Aug. 26 that its GE9X engine for the Boeing 777X aircraft will feature fewer and thinner composite fan blades than any GE widebody engine in service. To do this, GE is designing a new composite fan blade using next-generation carbon fiber composite material.

GE Aviation says the new material incorporates a higher stiffness carbon fiber and a new epoxy resin. The leading edge material will also be modified from titanium to a steel alloy to further enhance the blade’s strength. GE Aviation declined to reveal type of carbon fiber that will be used, the type of epoxy that will be used, nor who the material suppliers would be.

“It has been a decade since GE designed a new composite fan blade for the GEnx engine,” says Bill Millhaem, general manager of the GE90/GE9X engine programs. “Carbon fiber composite material has advanced in those 10 years, and the advancements enable GE engineers to design a thinner GE9X blade, which is just as strong as our current composite fan blades. Fewer, thinner blades will enhance the airflow and make for a lighter, more efficient fan that will help with the GE9X engine’s overall performance and fuel burn.”

Last year, GE engineers received positive results from material testing on full-sized GEnx blades. Testing of the new material continues this quarter in preparation for next year’s testing on the new GE9X blade design.

The GE9X fan blades are the fourth-generation composite fan blade design, built on the success of the GE90-94B, GE90-115B and GEnx engines. GE engineers continue to work the final design of the GE9X fan blade that will incorporate improved aerodynamics.

GE will spend $300 million in 2014 on technology maturation testing for the new GE9X engine. Tests include the Universal Propulsion Simulator (UPS) fan performance tests as well as testing of ceramic matrix composite components in a GEnx engine.

The GE9X engine will be in the 100,000-lb thrust class. Key features include a 133-inch diameter composite fan case and 16 composite fan blades; a next-generation 27:1 pressure ratio 11-stage high pressure compressor; a third-generation TAPS (twin annular pre-swirl) combustor for greater efficiency and low emissions; and ceramic matrix composite (CMC) material in the combustor and turbine. Almost 700 GE9X engines have been ordered by customers since it was launched on the Boeing 777X aircraft last year.

The first full core test is scheduled for 2015. The first engine will test in 2016 with flight testing on GE’s flying testbed anticipated in 2017. Engine certification is scheduled for 2018.

IHI Corporation, Snecma and Techspace Aero (Safran) and MTU Aero Engines AG are participants in the GE9X engine program.

Rolls-Royce Details Advance And UltraFan Test Plan

By Guy Norris, published in Aviation Week & Space Technology, Aug 25, 2014

Earlier this year Rolls-Royce took the unusual step of publicly laying out its strategic vision for developing a new series of large turbofans for the next decade and beyond. Now the company is beginning to detail the first steps it will take to turn this vision into reality.

The launch of its next-generation road map comes at a good time for the company. Buoyed by growing volumes of business in the widebody airliner market with its three-shaft Trent engine family, Rolls is in the midst of its biggest production ramp-up ever to support expanding fleets of Trent 1000-powered Boeing 787s and XWB-powered AirbusA350s. At the same time, it is developing the Trent variants for the later derivatives of both these airliners, as well as beginning work on the Trent 7000 for the newly launchedA330neo.

First steps toward Advance are underway with ground and flight tests of a composite fan under the Advanced Low-Pressure System program. Credit: Mark Wagner/aviation-images.com

Banking on the notion espoused by President John F. Kennedy that “the time to repair the roof is when the Sun is shining,” Rolls is acting now to ensure its competitiveness for the next round of airliner developments from the end of the decade and beyond. Ric Parker, director of research and technology at Rolls, says that thanks to the A350 and 787 engine programs, “we are in an amazing position today.” At the American Institute of Aeronautics and Astronautics Joint Propulsion Conference in Cleveland in late July, Parker also noted that the company’s strategy closely monitors the point “where evolution gives up and revolution takes over.” For the near term, the plan remains focused on the former, and the next steps will therefore be based on two more evolutions of the well-proven three-shaft heritage. “At Rolls-Royce we say, ‘invent once and use many times,’” adds Parker.

Rolls-Royce’s fundamental product plan, as first unveiled in February (AW&ST March 3, p. 20), is a two-phase evolution from today’s Trent XWB. The first engine, the Advance, is aimed at entry into service around 2020 and will have a bypass ratio in excess of 11:1, overall pressure ratio of more than 60:1 and fuel-burn level at least 20% better than the current Trent 700. The second, more ambitious follow-on engine is called the UltraFan, which Rolls first revealed in concept form in early 2012 as part of NASA’s Environmentally Responsible Aviation (ERA) study with Lockheed Martin. The engine could be ready for service in 2025 and is targeted at fuel-burn at least 25% better than the Trent 700. UltraFan drives a variable-pitch fan through a gear system and is outlined with a 15:1 bypass ratio and overall pressure ratio of 70:1.

Step 1 of the evolution involves fundamentally changing the traditional architecture of the Trent core to off-load the work performed by the intermediate-pressure (IP) spool and split it more evenly with the high-pressure (HP) system. To understand the significance of this, it is useful to note the basic architectural differences between the Trent family and the competing two-shaft designs produced by General Electric and Pratt & Whitney. Unlike these two-shaft engines, in which the fan and low-pressure (LP) compressor are driven by the LP turbine, the fan alone is driven by the LP turbine in the Trent. In place of the conventional LP compressor, the three-shaft design has an IP compressor which is driven by an IP turbine. Both two- and three-shaft engines have similar high-pressure spools, though there are fewer stages in the three-shaft compressor and turbine.

In previous evolutions of the Trent, Rolls has grown engine capability by expanding the work done by the IP compressor and turbine. “As we grew the Trent family IP compressor, we grew the pressure ratio and gradually supercharged the engine, always keeping the high-pressure spool very similar,” says Alan Newby, Rolls commercial engines advanced projects chief engineer. “The big change from the core point of view is that the Advance reverses that, so we will put more on the high-pressure spool,” he adds. The new Rolls engine will have a relatively larger high-pressure compressor with up to 10 stages (compared to six on the Trent XWB) and a greater pressure ratio, and it will be driven by a two-stage turbine against the single-stage used today. At the same time, the IP compressor will shrink from the eight stages of today’s XWB to around four, while the IP turbine count will be cut to one from two stages.

The new configuration “provides a very lightly loaded high-pressure spool, which gives good efficiency and, more importantly, significant commonality with the follow-on core of the UltraFan,” says Newby. “So we are laying down an architecture which we think is enabling the future.” In addition, for the first time on any Rolls engine, Advance will have a lighter composite-titanium fan, composite fan casing and lighter LP turbine system.

With a bypass ratio of more than 11:1, Advance will be distinguished by a larger fan and longer high-pressure compressor. Credit: Rolls-royce

Beyond Advance, the next big architectural change is the inclusion of a gear system to drive what Rolls believes will be a new generation of larger, higher-bypass-ratio fans, as well as the introduction of variable pitch fan blades and complete elimination of the LP turbine. The move effectively means the engine is no longer a true three-shaft design but rather a “two-and-a-half” configuration, notes Newby. However, Parker adds, “Even with three shafts, we still haven’t reached the tipping point where the weight and complexity of the gearbox outweighs the weight and complexity of lower-speed, lower-efficiency components. That’s primarily because we don’t have a low-speed booster on the fan shaft. Instead, we have an IP compressor that finds its own speed.”

Besides major architectural changes, both Advance and UltraFan will see the wholescale introduction of new technologies. In some cases these will be key enablers to the new configuration and in others they will help augment overall performance. “Arguably, the Advance is mainly about the core, though we are introducing the lightweight low-pressure system, so it is a bit of improving propulsive efficiency and lot about improving thermal efficiency,” Newby says. The lightweight fan and casing will have “a novel system of embedding harnesses and pipes in a composite ‘raft’ attached to the casing,” he adds. Other technologies will include a more advanced low-emissions combustor, lightweight compressor and turbine blade designs, improved blade cooling, dynamic sealing and adaptive cooling systems to optimize bleed off-take cycles. It will also feature new hybrid ceramic bearings to support the lighter core in positions farther aft in cooler, more benign locations, away from hotter locations faced by current bearings. 

Key technologies for UltraFan will build on the Advance developments in some cases and in others—such as the power gearbox, variable pitch blades and variable area nozzle—will be all-new. UltraFan will also have a new form of fully integrated, slim-line nacelle design. As the fan system is designed to vary pitch in all phases of flight, including landing, the nacelle will not include a thrust reverser. UltraFan will have a multi-stage IP turbine, the blades of which will be longer than any previous design. To reduce weight, titanium aluminide will be used for rotating parts and ceramic matrix composites (CMC) for static parts such as nozzles. 

Some potential technology elements “may be longer-term and may not be in the UltraFan when we take it to market,” says Newby, citing cooled cooling air and “blings” (bladed rings) as examples. An actively controlled cooled cooling-air system holds the potential to enable higher pressure cycles and turbine exit temperatures because it not only removes bleed air at a later stage, but it reinjects significantly cooler air back into the turbine blades, stator vanes, rotor disk and possibly liners. The system works by taking bleed air from the back of the compressor, passing it through a heat exchanger system linked to the bypass duct, and routing it into the turbine section. Testing of basic cooled cooling-air systems has been undertaken as part of the European Newac program.

Blings are “the next evolution from blisks [bladed disks] today and this takes it further,” Newby says. The bling eliminates the need for a deeper ring by having a very strong, potentially reinforced metal-matrix ring with integral blades formed on the outside.

Validation of the composite fan for Advance is underway as part of the ALPS (Advanced Low-Pressure System) program. The new fan set has been mounted on a pair of Trent 1000 engines in a straight swap for the original hollow titanium fan. Following initial sea-level testing here, one ALPS test engine has been shipped to Rolls-Royce’s site at Stennis Space Center, Mississippi, for crosswind evaluation. A second engine is being readied for flight tests later this quarter on the company Boeing 747-200 flying testbed in Tucson, Arizona. “That’s really a final check to make sure there is nothing in terms of flight loads that we haven’t spotted in sea-level testing. We wanted to do the Stennis testing first to make sure we understand its behavior,” Newby says.

The projected weight savings of 750 lb. per engine from adopting the new material is “well worth having,” he adds. Although GE has been using composite fans on its large engines since the 1990s, Rolls said its hollow titanium blades have remained competitive. However, with increasing fan diameters, “the time is right because the manufacturing technology allows us to get the thickness [of a composite blade] right down,” says Newby.

More substantial tests of the Advance core technology at full engine scale are also planned using a Trent XWB donor engine. “We will take the HP and IP spool out of an XWB and replace it with an Advance core architecture,” Newby says. He notes that the “Stage 1” exit from concept definition is finished and design freeze is the next step. “We have already got the disk forgings in, and we are starting to machine those. We are looking at different supply chain options to get bits in quickly, and our plan is to run the first build by the end of next year and run a further build [for endurance testing] in 2016,” he adds. “A team has been created and it has got that buzz about it like a new project. It is quite exciting.”

The new core section will incorporate a four-stage IP compressor and 10-stage HP compressor for the testing, though Newby cautions that this “may or may not be the final production configuration,” adding: “It’s not just about the aerodynamics; it’s about how you bring it together as a system. It is those things we want to check as well as the basic aerodynamics.” The only stage counts that are guaranteed to carry through to the production standard will be the test unit’s single-stage IP and two-stage HP turbines.

The higher pressure ratios planned for Advance and UltraFan mean higher operating temperatures and increased generation of nitrous oxides. Several key technologies for coping with these—and to reduce fuel burn and emissions—will be validated during continuing runs of Rolls’s long-running Environmentally Friendly Engine (EFE) test unit. First run in 2010, the fourth build of the Trent 1000-based EFE recently completed a new series of evaluations of high-temperature-capable advanced turbine materials and a lean-burn combustor design. EFE was used to test CMC high-pressure turbine blade tracks in 2013 and more recently evaluated CMC shroud segments. Testing will continue through 2015, Newby says.

Trials of a robust lean-burn combustion system have “gone really well,” says Newby. “We have done rig and core engine testing and will run another Trent 1000 with a new combustion module. We’ve done the chemistry in the rigs and we know it works, so this is about putting into a systems environment to see how it behaves on relight, altitude relight, pull-away and when you put water down it. Again like ALPS, this Advanced Lean Combustion System (Alecsys) and EFE are all full-scale Trent 1000s, and Advance will be XWB.” Together with earlier work conducted in Germany under the European Clean Sky 1 research program and Alecsys, “we know this gives us good margin to the [emission regulations] CAEP 6 and 8, and gives us confidence we can meet targets even with more aggressive cycles,” Newby says. “So this allows us to grow these cycles and improve emissions which tend to go in the opposite direction.” Following ground tests, Rolls plans to flight-test the new combustor in 2015 on the company’s 747 flying testbed.

In readiness for UltraFan, Rolls is building a €65 million ($87 million) research and development facility in Dahlewitz, Germany, for testing power gearboxes. “This is a big program,” says Newby. “It will take the Advance core, which we are laying down through the XWB, and wrap a new low-pressure system around it. This will be one of the main parts of the Clean Sky 2 program and is partially funded through both U.K. and German national programs,” he adds. Although Rolls acknowledges the UltraFan gear will be a form of planetary device, it is reluctant to divulge more details. “We have a clear idea of what the baseline is, and we think we know what the right answer is; we just have to validate it. The gear ratio will be around 3:1, if not probably a bit more.” The rig will be adaptable to various engine sizes and capable of testing gear units and associated oil systems at various angles and attitudes. Power gearbox testing is scheduled to run through the end of 2015, with component testing running beyond that. 

International Aero Engines Achieves Certification of V2500®-E5 Engine

 

aviationnews.eu. Published August 27, 2014. By Marcel van Leeuwen

 

IAE International Aero Engines AG has achieved Federal Aviation Administration certification of the V2500®-E5 engine for Embraer’s KC-390 aircraft. The KC-390′s launch customer is the Brazilian Air Force.”Achieving engine certification on schedule is a big win for the program,” said Jackson Schneider, president and CEO, Embraer Defense & Security. “We have a high level of confidence that the engine will perform as reliably as its in-service counterpart has done, and we look forward to a successful first flight.””Reaching certification is further proof of the steadfast reliability of our V2500 engines and our development team’s ability to enhance this technology,” said Dave Brantner, president, Pratt & Whitney Commercial Engines. “Our entire team looks forward to supporting Embraer’s goals for the KC-390 program.”The V2500-E5 engine, rated at 31,330 pounds of thrust, was selected in July 2011 by Embraer Defense & Security and the Brazilian Air Force, which established the KC-390 requirements. While Embraer and its customers desire maximum commonality with the V2500 engine, changes have been made to optimize installation with the new airframe.The overall IAE program provides a fully integrated propulsion system, including the V2500-E5 engine and nacelle with engine build-up and nacelle installations supported by UTC Aerospace Systems’ Aerostructures business. The system will be delivered to Embraer’s customer, the Brazilian Air Force, supporting a scheduled 2016 entry into service.Throughout its 45-year history, Embraer has been involved in all aspects of aviation. In addition to design, development, manufacturing, sales and technical support for commercial, agricultural and executive aviation, Embraer also offers integrated solutions for defense and security. It has produced more than 5,000 aircraft that operate in 80 countries on five continents, and it is the market leader for commercial jets with up to 120 seats. Embraer currently manufactures executive jets, and is now entering a new level in the defense segment.IAE is a multinational aero engine consortium whose shareholders comprise Pratt & Whitney (NYSE: UTX), Pratt & Whitney Aero Engines International GmbH, Japanese Aero Engines Corporation and MTU Aero Engines. To date, more than 6,000 V2500 engines have been delivered to close to 200 customers around the world.

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