FLUG REVUE September 2002: Mid-sized engine market has good outlook

THE MID-SIZE ENGINE MARKET

By Patrick Hoeveler

Between now and 2020 13,350 new aircraft will be needed in the 100-240 seat range according to Boeing, 57% of all the new airliners. An idea of the magnitude of this requirement can be gained from considering that it is the number of planes that would be necessary to fly the entire population of Berlin, over 3 million in number, to the holiday destination Majorca all at once. Boeing's European rival, Airbus, believes that 7,500 new single-aisle aircraft, worth some $327 billion, will be required between now and 2019 just in the 100-175 seat class. In view of the scale of the requirement, it would appear that there are rich pickings to be had in sales of engines, especially of engines in the mid-thrust range.

In this segment, CFM International remains the clear market leader, with no less than 13,000 of its engines currently in service around the world. And here, according to Pierre Fabre, President and CEO of this joint company between GE Aircraft Engines and Snecma, the company will hold on to its lead. Its TECH56 technology programme is aimed at developing fifth generation versions of the successful CFM56 engine, of which no less than 1,040 were delivered last year. However, the programme is also benefiting earlier versions, as Robert Barton, General Manager of GE Engine Services, explained to FLUG REVUE in Cincinnati.

CFM56 engine

The first type, the CFM56-2 which powered the Douglas DC-8 Super 70, was followed by the CFM56-3 for the Boeing 737 Classic. Full Authority Digital Engine Control (FADEC) was introduced on the third generation CFM56-5A and –5C, which power the Airbus A320 family and the A340, along with the improved materials and coatings. The present product range, centred around the CFM56-5B/P and the CFM56-7 for the 737NG, incorporates wide-chord fan blades and three-dimensional computational design (3-D aero), features which in turn will be passed on to upgrades of the earlier models. According to Barton, the next generation of engines will have characteristics demonstrated in the TECH56 programme, which can then be incorporated retrospectively in the present models as well.

The latest example is the CFM56-3 upgrade. "We analysed the areas that were calling for cost-intensive maintenance work and then identified the technologies which could help reduce the maintenance requirement. Most of this occurs in the hot section.” On the CFM56-3, the main items affected were the compressor blades and the materials used in the high pressure turbine. The new modified core should lengthen the time between shop visits. "Back in 1986 engines were coming off the wing after 3,500 hours, but ten years later this had increased to 12,000 hours.”

And thanks to the compressor and high pressure turbine borrowed from the CFM56-5B/P and CFM56-7, these figures should improve still further. According to Barton, the $1.2 million kit offers a 1.1% reduction in fuel consumption, a 15ºC lower exhaust temperature and, by this, up to 2,000 additional cycles.

But even the more recent variants are enjoying state-of-the-art technologies. The latest upgrade product to have been developed is the CFM56-5C/P, which is to commence flight trials on the Airbus A340-300 Enhanced this autumn. The high pressure compressor and turbine, which have been aerodynamically optimised using 3-D aero, should reduce maintenance costs by 10%. "We are keeping even our latest engines ready for improvements and changes in the emission limits.”

One of the possible strategies mentioned by Barton is the retention of performance in the compressor, something which normally declines over the time. "Up to 4.5ºC per 1,000 cycles are noticable.” From 2005, due to improved materials, performance retention features could be offered. In the same time frame, improved cooling should increase the service life of the high pressure turbine blades.

From 2006 a single annular combustor that uses new cooling technology could be available, enabling NOx emissions to be further reduced. The market for such upgrades is growing visibly. "Even early versions of the CFM56 can remain in service for 30 to 40 years,” says Barton.

Features likely to be introduced on the next generation of engines include swept wide-chord fan blades and fan blade-out decoupler technology, under which, in the event of a blade becoming loose, the low pressure turbine decouples itself from the fan. This reduces the amount of energy acting on the fan casing, so that the casing can be constructed with a lighter weight. "In ten years we could also integrate this into the earlier generations.” However, the precise form that a successor to the CFM56 will take will be determined by the aircraft manufacturers. "No one knows what the next generation of aircraft for 150-200 passengers will be like. TECH56 was originally intended for precisely this, but the programme results will probably be fed into upgrades for existing engine types.”

A similar view of the future is taken by management at International Aero Engines (IAE). The consortium formed between Pratt & Whitney (32.5%), Rolls-Royce (32.5%), the Japanese Aero Engines Corporation (JAEC) (23%), itself a consortium of Japanese aerospace companies, and MTU Aero Engines GmbH (12%) is CFM's main rival in the competition over the A320 family, having delivered 1,800 V2500 engines. 281 engines were delivered last year and, with 94 firm orders, the company increased its market share on single-aisle Airbuses to 72% for 2001. Naturally IAE intends to boost this further. At present some 37 sales campaigns are under way, relating to a total of up to 800 aircraft. Military applications on transport and surveillance aircraft are also being studied. However, there are no plans for any four-engined applications.

In the new headquarters in East Hartford, Connecticut, the company relies on the improvements already implemented on the V2500-A5, producing lower exhaust gas temperatures and improved performance retention combined with better emission levels. Thus, all V2500 variants satisfy the Stage 4 noise limits, including the V2533 which has been designed for the A321 and produces 146.7kN of thrust with an improved hot section.

Compared with the earlier V2500-A1, the engineers have added an extra 1.27cm to the blade chord and moved the fan further forward. The low pressure turbine now has four stages instead of five. About 70% of the fleet has already upgraded from A1 to A5.

But IAE is not planning to rest on its laurels either. "What customers want most of all today is low operating costs.” It is the intention of Stephen Heath, President and CEO of the joint venture, to reduce these by up to 30% by the middle of the next decade. "We are working hard on the future. The next generation of engines will come from IAE, both for Airbus and Boeing. We will never again make the mistake of concentrating on just one application.” However, the first concrete discussions are not expected to take place for another two to four years.

By 2010 they are hoping to have reduced fuel consumption on a possible successor to the V2500 by five to ten per cent and to have lengthened the minimum time between overhauls to 15,000 hours. NOx emissions are to be reduced 40% below the CAEP/2 ICAO limits. According to Heath, an engine built for a new application that incorporates these features could enter service between 2010 and 2012.

For the present generation, the next step could be to make use of Pratt & Whitney's Technology for Advanced Low NOx (TALON) combustion technology. "In the area of technology we have a lot of experience available and can draw from the strengths of all the companies in the consortium,” says Ron Benson of IAE. A new wide-chord fan from Rolls-Royce could be installed, as could an improved high pressure turbine from Pratt & Whitney. However, such enhancements must be capable of being retrofitted on the entire fleet of the joint company. For example, where higher thrust is required, integration of a swept fan to obtain a higher bypass ratio would be possible in a relatively short time scale, 18 months, but it is more likely that this will be implemented on a new model. This could then perhaps incorporate a geared turbofan.

In the next higher thrust segment, however, the IAE partners are in bitter competition with each other. Whereas Rolls-Royce is offering a three-shaft configuration in the RB211-535 for the Boeing 757, Pratt & Whitney's PW2000 family remains committed to a two-shaft design. According to Rolls-Royce, the distinguishing feature of the British product, which has an order backlog totalling around 1,200 engines, is its low maintenance costs resulting from an average 22,000 hours' time on wing before the first overhaul.

Pratt & Whitney is also working on a further reduction of maintenance costs on the PW2000, which in the past has met with a number of problems. A new guide vane design is expected to eliminate vibration of the inlet guide vanes in the sixth compressor stage. In addition, by the third quarter of 2003 the entire fleet, currently numbering some 940 civil engines, is to be fitted with a new stator between the 10th and 11th stages of the high pressure compressor in order to prevent in-flight shutdowns due to cracks developing in the braze joint on the vane's trailing edge. The vanes and stator shrouds are now cast in a single piece.

Northwest recently took delivery of the first of sixteen PW2000 powered 757-300's. The certification granted in June also covers the 194kN variant, but this has not yet attracted any customers. It would merely require some software modifications plus the addition of an extra fuel pump. According to programme manager Joanne Hastings, there is no issue of using the PW2000 to power the Ilyushin Il-96, as there is no market for this at the moment.

At the lower end of the performance scale, two of the latest and most technologically advanced programmes are to be found. Here Pratt & Whitney's PW6000 is pitted against the BR715 from Rolls-Royce Deutschland. While the company located in Dahlewitz near Berlin recently celebrated delivery of the 200th engine for the Boeing 717, the PW6000 will not enter service on the Airbus A318 until the fourth quarter of 2005.

The American product has only 15 stages, compared with 19 on the rival CFM56-5B, and hence fewer blades, which account for some 60% of the material maintenance costs. According to programme director Brian Sill, the life-limited parts are designed for 25,000 cycles on shorthaul operations. The Block 4 version has the HDV12 high pressure compressor developed by MTU, which should satisfy the guarantees promised to Airbus. There are also plans to equip three stages of the high pressure compressor with Integrally Bladed Rotors (IBR). Testing on the PW6000 is scheduled to commence in the summer of 2003. Despite the 32 months' slippage, Sill is confident that the A318 market will revive. Here he is relying on the forward-looking technology used in the engine.

However, the technological advances on future powerplants are unlikely to be so major, as Jean Colpin, Vice-President, Commercial Engine Programmes, at P&W points out. "For this reason we are focusing on entire systems, not just on individual technologies.” He believes breakthroughs might be possible, for example, in the areas of cooling technology and lightweight materials. "We need a high bypass ratio without having to carry the weight.” But, "improvements are becoming ever more difficult.”

From FLUG REVUE 9/2002, page 88

Last updated 9 August 2002

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