Rappel de la dispute sur la conso... EA semblant être mieux sorti de l'emballage et RR mieux sur la durée (
http://atwonline.com/aircraft-engines-components/article/when-every-fraction-counts-1028
Although it may not be quite in the“my kingdom for a nail” category, Engine Alliance and Rolls-Royce are emphasizing gains of fractions of percentage points in the battle for uncommitted A380 orders. And when engine and aircraft deals are won and lost on those fractions, any advantage can be a winner.
That is the message from Engine Alliance, the joint venture between GE Aircraft Engines and Pratt & Whitney, which has delivered more than 100 GP7200 Series engines for the A380. EA President Mary Ellen Jones tells ATW, “The GP7200 has met or exceeded our customers’ expectations and Airbus recently revised the performance handbook, or Orange Book, to reflect a 0.5% SFC improvement for the GP7200-powered aircraft.” The improvement was measured from flight test aircraft MSN009 and first production aircraft MSN011 and EA believes further gains can be expected in later models.
The Orange Book is used frequently by prospective purchasers as a predictor of aircraft performance. “We believe this demonstrates an advantage of approximately 1.5% versus the competition,” Jones says, adding that after nearly two years in revenue service, the engine’s dispatch reliability rating is “99.9%.”
There are two variants, the GP7270 rated at 70,000 lb. and the GP7270E rated at 77,000 lb. The engine has a bypass ratio of 8.7 and can be certified beyond 81,500 lb. with a little additional work, as most of the certification was done at the higher thrust for the proposed freighter version.
Rolls dismisses the EA claim that the GP7200 has a 1.5% fuel burn advantage. “Only Airbus has the precise data and the company does not share that with anyone,” says Head of Marketing-Airbus Programs Richard Keen. “The Trent 900 is delivering as per the Airbus specification on weight, fuel burn and noise.” In fact, on noise it is better than specification, exceeding London Heathrow’s QC1 requirement with a QC0.5 rating. Rolls also highlights that the Trent 900’s three-shaft architecture has a slower rate of deterioration, which in combination with better-than-specification fuel burn at EIS gives it the lowest lifetime fuel burn on the A380.
The Trent 900 is certified at 76,500 lb. thrust with a BPR of 8.7. It weighs in at 14,190 lb. with a fan diameter of 116 in. In test it has run up to 93,000 lb. and can be certified up to 80,000 lb. using the current bill of materials.
While disputing the EA claims regarding fuel burn numbers, Rolls is working on leapfrogging the GP7200 with a two-pronged plan to boost the Trent’s performance. The first phase, dubbed the Trent 900EP, is available for delivery from 2011 and will provide a 1% fuel burn improvement over the in-service engines with Singapore Airlines and Qantas. The package takes compressor blade/vane technology from the Trent 1000 for the 787 that has been incorporated into the Trent 700EP launched in 2008. This ability to migrate new technology advances back into existing programs is one of the major benefits of being part of an engine family, says Strategic Marketing Manager-Civil Aerospace Future Programs Paul Randall.
Specifically, the Trent 900EP upgrade relates to a new standard of airfoil throughout both IP and HP compressor systems that is interchangeable with today’s standard. However, Rolls says that because the retrofit would require swapping out many serviceable blades, it is not actively pursuing a retrofit policy. The upgrade also includes some tweaks to the air management system. The package, which will be standard from 2011, delivers a 1% improvement in fuel burn while not impacting maintenance. Rolls additionally is incorporating “maturity modifications to upgrade areas” that have become apparent from early engines. These include tip clearance and seals.
The second phase of the improvement plan is for the 2014 timeframe and focuses on the Trent XWB for the A350. The gains are expected to exceed those of the current Phase 1 upgrade although that program is not due to be launched till 2013. The Trent XWB will be the first to feature a two-stage IP turbine and also the first to add blisks—single components comprising the rotor disk and blades. This decreases the number of components, which in turn lowers weight and improves drag. Removal of the attachment also eliminates a common source for crack initiation and propagation. Blisks are used on the GE F110 and will be used by CFM in the compressor section of its LEAP-X program. To increase cruise efficiency, the Trent XWB will have a modulation system that optimizes bleed air for turbine blade cooling. Certification is set for the end of 2011.
Director-Airbus Programs Ian Crawford sums up by saying: “Rolls-Royce has shown a commitment to continuous improvement through the whole Trent engine family. With two engines demonstrating new technologies (Trent 1000 and Trent XWB), the opportunity for further improvement is clear. Rolls-Royce will continue to review these opportunities and apply them as appropriate.”
Engine Alliance is not standing still either. “We and our customers are very pleased with the GP7200’s performance to date. We’re always looking for ways to improve even further and will stay aligned with Airbus’s A380 product plan as we evaluate the next steps,” says Jones. One improvement has been weight reduction, she says. “The GP7200 was a bit over its spec weight at entry into service. Recognizing the importance of weight to both Airbus and our airline customers, we successfully implemented a number of weight reduction initiatives in the past couple of years. The latest contributor is a redesigned turbine exhaust case that will enter service next year and will reduce engine weight by about 50 lb. At that point, we’ll have taken about 150 lb. out of the engine, bringing us to approximately 100 lb. below spec.”
Reliability
Thus far the GP7200 has had only a couple of cautionary inflight shutdowns in more than 200,000 flight hr. and dispatch reliability was 99.9% as of June 30. There have been two engine removals caused by unrelated oil pressure issues. By year end there should be 19 GP7200 A380s in service—15 with Emirates and four with Air France—and the engines will have performed 300,000 flight hr. and 60,000 takeoffs.
EK President Tim Clark waxes lyrical about the engine. “There are simply no problems,” he tells this magazine. “Meeting performance guarantees doesn’t come into it. The A380 is ahead of her specs.” And in a twist, he adds that “the faster she flies the less fuel she burns.” Long-range cruise is Mach 0.85, but “if she operates at Mach 0.83, fuel burn increases,” he says. The GP7200 has shown “no degradation” in performance.
Like EK, Qantas is delighted with the Trent 900’s performance with no IFSD issues. SIA suffered some “teething issues” with its engines but the removals were precautionary, not required for preventative action. It also had three early IFSDs, but the engine has settled down well over the last 18 months after some upgrades and changes that included solenoid valves, bleed valves, wiring, guide vanes and electronic controls.
Rolls argues that reliability statistics show the Trent 900 to be the most reliable product on the A380. It claims it has a better rating in every reliability category than the “competing” engine and is the cleanest, with the lowest cumulative emissions including the lowest NOx rating.
Emirates’ recent buy of 32 more A380s gives Engine Alliance bragging rights on numbers of engines ordered at 548 for 128 aircraft including spares. As well as EK and AF, Etihad Airways, Korean Air, ILFC and Air Austral have specified the GP7200. Rolls counts more customers, however, with Qantas, SIA, Thai International, Malaysia Airlines, Lufthansa, Virgin Atlantic, China Southern, British Airways and Prince Al Walid committed to 90 aircraft.
Qatar Airways and Kingfisher are uncommitted on engine selection. Vietnam Airlines is a potential customer for the A380 along with ANA and Asiana, while Jones says talks are underway with some potential US customers thought to be passenger airlines.
Origins
The GP7200 combines components from the GE90 and PW4000 and their combined 25 million-plus flight hr. of operation with new technologies. GE is responsible for the manufacture of the high-pressure compressor, combustor and high-pressure turbine, while P&W builds the fan module, low-pressure compressor and low-pressure turbine. Major program participants include Snecma, Techspace Aero and MTU Aero Engines.
Like the Trent 900, the GP7200 had its origins not as an engine for the then-A3XX but for the 747-500X and -600X, which at the time had a tight 33-month certification goal of December 1999. The partnership was announced in May 1996.
Rolls signed with Boeing in July 1996 and its design was based on the Trent 500 core for the A340-500/-600 scaled up 10%. Since that date, a number of partners have joined the program including FiatAvio, Goodrich, Hamilton Sundstrand, Honeywell, Marubeni, Volvo, Samsung Techwin and Kawasaki Heavy Industries.
Interestingly, EA was formed because the two companies did not think the market for the 747-500X/-600X was big enough to support three products and neither wished to repeat the incredibly sporty competition among Rolls, Pratt and GE on the original 777, an experience for which the phrase “no more three on a wing,” was coined. In another departure, the requirement to meet Heathrow’s QC2 takeoff noise level instead of the original QC4 drove the engine design.
The noise requirement, which came from SIA and Qantas late in the design process in early 2000, was more demanding than weight for both engine-makers. Then-Rolls President-Civil Aerospace programs Mike Terrett told ATWin 2004 that “for the Trent 900 and the Engine Alliance GP7200—both engines—I think that for the first time in history the noise requirement, the requirement for Heathrow, was the design point.” Both achieved the goal with a larger fan and dramatically swept blades.
The quietness of the engines is having major benefits for airlines in attracting customers, with all operators reporting very positive feedback from passengers on the quiet of the cabin. Flight attendants are also bullish on the low noise levels, which make their jobs less stressful by allowing them to sleep more readily on rest breaks.
While some had considered the A380 engine program limited, Emirates’ recent reorder has shifted the dynamics of the market, with the airline reporting more than a dozen new airports talking to it about services. More carriers well may take greater interest in the aircraft—and thus engines—that continues to turn heads and more importantly passenger habits.
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par Beochien Ven 23 Juil 2010 - 17:18
EA = 
... ben i l n'y a rien a faire de mieux, si c'est un défaut conceptuel sur l'arbre IP/ Disc (Et on va finir par l'admettre que ça plaise ou pas à RR) 
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