FLUG REVUE October 2002: GP7000 competes for A380 business

ENGINE ALLIANCE GP7200 SCORES ON A380

By Patrick Hoeveler

With the order announcement from FedEx, General Electric and Pratt & Whitney have brought the market share of their GP7200 to 41%. Its competitor Rolls-Royce has won another 42% for its Trent 900. Qatar and ILFC (the remaining 17%) have not yet decided on an engine and, according to Thompson, the leasing company will go along with whatever its customers choose: "It will be a tie between the two engines.” First deliveries to Emirates (22 aircraft) are scheduled for October 2006, followed by Air France (ten aircraft from the end of 2006) and FedEx (third quarter of 2008).

GP7200 for A380

To meet these dates, the programme is already in full swing. The GP7200 combines technologies perfected on the GE90 and PW4000, along with some new elements. Thus the new powerplant has been aerodynamically optimised using 3D aero design throughout. Pratt & Whitney is responsible for the fan, the low pressure system and the gearbox, whereas GE is in charge of the high pressure system, the combustor and the FADEC.

The fan consists of 24 swept, hollow titanium blades and has a diameter of 2.95m. Borrowed from the PW4090, it had to be increased from its original size, as Bruce Hughes, Executive Vice President of the Engine Alliance explains: "In the Singapore competition, Airbus modified the specifications to take account of QC2.” The GP7200 had to satisfy these new stringent noise limits imposed at London's Heathrow airport. The original fan size of 2.84m would have produced 1.2% better fuel burn, but at the expense of higher noise emissions, as product line general manager Dennis King explained to FLUG REVUE in Cincinnati. In the other headquarters of the joint venture in East Hartford, product marketing manager Peter Corliss added, "Noise is driving design criterion on this engine.”

Chevron nozzles on the core would provide additional scope for noise reduction. At present, according to Hughes, this will not be necessary to satisfy QC2. However, the Engine Alliance has only guaranteed to Airbus that the passenger version of the engine will be QC2-compliant. The cargo version at present only just meets the requirement without margins.

Also in the core engine the companies are building on tried and tested technology. Thus the core of the GP7200 is essentially the same as the GE90-115B but with 86% of its physical size and 72% of its aerodynamic airflow. The low pressure compressor consists of five stages, while the nine-stage high pressure compressor uses blisk (bladed disk) technology in teh first stage. Also from the GE90-115B is the third generation digital FADEC.

On the other hand the single annular combustor comes from the CF6 programme. According to Hughes, compared with the larger GE90, which uses a dual annular combustor, a single combustor is sufficient in this case and will ensure that NOx emissions are up to 40% below the CAEP4 limits. Emissions of hydrocarbon and carbon monoxide are as much as 80% below the limit values.

One of the special features of the two-stage high-pressure turbine is the use of the N5 single crystal alloy, while ME3, a disc alloy, is to be used in the six-stage low pressure turbine, which has hollow blades in the forward stages. These materials make the GP7200 more heat-resistant, and with good reason. "A four-engined aircraft climbs more slowly and hotter than a twin, which because of ETOPS regulations has to be overpowered,” says King.

On the turbines the engineers are paying close attention to the phenomenon where the airflow spirals through the different stages and is influenced by the interaction between the rotor and stator airfoils. Indexing or "vane clocking” should increase the efficiency of the individual stages.

The experts from the two American industry giants are offering the engine at two thrust ratings: the GP7270 at 311kN (70,000lb) for the passenger Airbus and the 340kN (76,500lb) GP7277 for the freighter. However, the engine is to be certified at 363kN (81,500lb) of thrust. "That will give us growth potential for the future,” says Lloyd Thompson.

All of the variants are 4.67m long, have a diameter of 3.16m and a bypass ratio during cruise of 8.7. The overall pressure ratio at maximal climb will be 43.9 for the GP7270 and 45.6 for the GP7277. The need to reduce costs has been a paramount consideration during development. "The GP7200 will probably have the lowest specific fuel consumption of all the GE and PW engines at the entry into service,” says Thompson.

This December will see the start of the detailed development phase. Already this summer the engineers have implemented some changes such as the use of carbon seals to reduce oil consumption. Moreover, at the request of Air France, the FADEC monitoring system has been moved away from the oil tank, which was immediately above it, so that there is now a "dry” side and a "wet” side.

The first full engine tests are scheduled for March 2004. Flight testing on GE's Boeing 747 will commence in September 2004. If everything goes according to plan, the engine should achieve FAR33 certification in July 2005, with an entry into service in October 2006. By then it will have completed 23,000 tests cycles, 30% more than on the ETOPS programmes. "With more than 555 passengers on board, there must not be any problems,” says King. But not only safety but also reliability is very important, since with this number of passengers any cancelled flight would be very expensive.

The biggest challenges according to the Engine Alliance's management are the core and the fan. For this reason, several test programmes have already been carried out, such as the Advanced Technology Fan Integrator, (ATFI). This is a 42% scale version of the GP7200 fan, but without hollow blades. Next year Pratt & Whitney is planning trials with a 2.74m diameter demonstrator fan on a PW4098.

Extensive compressor tests are also planned. Despite good results, GE is planning a third series of trials for the core engine at the beginning of 2003 in order, according to Bruce Hughes, to improve the air flow by 0.5% and the stall margin by 2%.

The core is to be built at GE's plant in Raleigh/Durham, North Carolina, while final assembly will be carried out by Pratt in Middletown, Connecticut. A relatively large proportion of the engine will be coming from Europe. Thus, Techspace Aero, a member of the Snecma Group, is to produce parts of the low pressure compressor and will be responsible for final assembly of this element. Snecma itself is to build the first six stages of the high pressure compressor and assemble the compressor. MTU Aero Engines is working for both the American companies. The German firm is to build components of the high-pressure turbine and is also developing and building the low pressure turbine. According to MTU, its overall share of the programme will be approximately 22%.

The market for the GP7200 continues to be viewed with confidence by the managers. Lloyd Thompson sees a requirement for 700 A380's over the next 20 years and is aiming for a 50% market share for his Engine Alliance. He does not exclude the possibility of installing this engine on the Boeing 747, for which the GP7000 was originally intended. "If Boeing wants it, the product will be available.” A possible GP7100 would have a smaller fan. The modifications could be completed in a year. However, there is no question of it being used on the present version of the Jumbo Jet, as the EU contract restricts use of the engine to aircraft with at least 450 seats. As far as the Alliance is concerned, this rules out the Sonic Cruiser as well.

From page 84 of FLUG REVUE 10/2002

Last updated 12 September 2002

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