FLUG REVUE September 2003: Smaller turbofans for regional aircraft

BRIGHT PROSPECTS FOR SMALL ENGINES

By Patrick Hoeveler

“It takes a lot of guts to build something out of nothing.” The at the time courageous decision by Bombardier to offer a 50-seater regional jet has paid off, as Charles “Chip” Blankenship, General Manager of the Small Commercial Engines Division of GE, acknowledges. Today the sector is booming, and the CRJ100/200, with around 1,026 orders, is still the market leader ahead of the Embraer ERJ series, which entered the market later and has clocked up 879 orders. Despite the recession and the terrorist attacks of 11 September 2001, the regionals are continuing to grow, while the rest of the industry is having to contend with major problems, as Blankenship points out. In his view, there will be increased emphasis in the future on aircraft for 70 passengers and above, as the latest major orders from US Airways and JetBlue suggest. “We knew that this would be the case, it just came sooner than we expected.”

Especially since the JetBlue order, according to Blankenship, both larger airlines and also low-cost carriers have been re-examining their structures. In his opinion the industry is in a transition phase. “The question is how long we will be using the terms 'regional jet' and 'regional airline'.” In view of this, his division will be renamed, although the new name has not yet been made public.

The competition is also anticipating sustained growth in this segment. Thus, Rolls-Royce is forecasting a requirement for more than 6,100 new regional jets between now and 2022 as well as around 8,290 business jets in the medium, long-range und very long-range segment until 2021. Snecma is expecting demand over the next 20 years to be as high as 8,000 units. At GE alone, they are expecting over 450 orders for 2003 after the scant 100 engine orders received last year. Production for this year and next year is expected to be around 400 units.

Back in the 1990s, when demand for regional jets first started to take off in a big way, no one foresaw how successful they would become. Lufthansa CityLine was the first airline to operate the Canadair Regional Jet. Almost 11 years later, over 900 CRJs of different versions are in service, all powered by CF34 engines built by GE Aircraft Engines. Altogether, GE has invested about $150 billion in the “small” engines, which are treated on the same footing and are regarded as just as important as the powerplants for widebodies and narrowbodies within the company, as Blankenship points out.

The engine is a derivative of the military TF34 used on the Fairchild A-10 and Lockheed S-3. At the end of the 1970s Canadair selected a version of this engine as the CF34 for the Challenger business jet. When the Canadians decided to develop a regional jet derivative of the CL-601, they stayed with GE. The engine builders delivered the more powerful CF34-3 variant, which still has hydromechanical controls. However, some 50 percent more thrust was required in the CF34-8 for the new 70-seaters from Bombardier and Embraer. The designers kept the basic architecture but enlarged the fan diameter and used a compressor that was a scaled-down version of the one on the F414 military engine for the Boeing F/A-18E/F Super Hornet. Other new features are the digital FADEC control system and a chevron exhaust nozzle designed to reduce noise emissions. The differences between the A/E variants for the CRJ and the Embraer 170 are confined to installation parts, as the turbo machinery is identical.

General Electric CF34-10D

Then when it came to the CF34-10 for the 90-seater, the specification required a further 15 percent thrust. “We decided to use the CFM56 core rather than enlarging the CF34-8 as a better commercial solution,” explains Blankenship. The result was a completely new engine with a new architecture. Actually it could have been renamed, but it was decided to stick with the CF34 as brand label.

Thus the nine-stage compressor is based on the CFM56-7, a product of the joint company in which GE and Snecma are equal partners. Originating from CFM's TECH56 research programme are the low-solidity blades which offer the greatest possible distance between themselves without causing a stall and therefore are reducing the blade count in the high-pressure turbine.

A total of seven engines are currently in a test programme, and five of these have already been run and completed 700 hours. In September, the CF34-10 will then undergo flight trials on the company's own testbed, a Boeing 747. The engine will be mounted in the number two position. This will mean that for the first time the test aircraft will be flying with only four engines instead of five with a member of the CF34 family. The initial rating for the -10E5, earmarked for the Embraer 190, is 82.21kN. “The aircraft has, not unexpectedly, grown a little in size,” says Blankenship. For this reason the company plans to have the model certificated in the -10E7 form, with an output of 88.88kN. Here the choice of an architecture which allows the thrust to be increased was proving to be an advantage according to Blankenship.

Currently, GE is in discussions with aircraft manufacturers regarding a successor to the CF34-3. “The question is about what the future of 50-seat RJs is. A decision won't be made until we have an answer.” By the end of this year 2,000 engines will already be in service with 37 customers, and by 2007 this figure could rise to as many as 3,000. “We are aware of our responsibility to our customers and are working on upgrades to feed new technology into the existing engines,” explains Blankenship. As well as the existing -3B1, with higher thrust and lower fuel consumption, they are working at GE on new materials made out of single-crystal alloys for the high-pressure turbine.

The innovations are being taken from the CF34-8 and -10 and will be tried out on a technology demonstrator at the end of the year along with other improvements intended to reduce maintenance costs. At present GE does not want to publish the name of the programme. It will, however, be the “next step for the -3B1”, according to Chip Blankenship.

Despite having got into the 50-seater segment early on, GE is not alone on this market. Rolls-Royce is close on the heels with its AE3007 for the smaller Embraer jets. The first version of the AE3007 for a regional jet entered service on an Embraer ERJ 145 with Continental Express in 1997. This engine has the same core as the AE2100 turboprop (Saab 2000, C-130J, C-27J) and the T406 turboshaft engine used on the Bell/Boeing V-22 Osprey. Originally the family was developed by Allison, but in 1993 the company left the General Motors group and was taken over by Rolls-Royce in 1995.

The most recent addition to the family, the AE3007A1E, produces seven percent more thrust and its other distinguishing features, according to Gary Bianchini, chief project engineer for the AE3007, are an upgraded hot section, longer maintenance intervals and a new software version. It entered service on an extended range Embraer ERJ 145XR with ExpressJet last November. Additionally, the engine manufacturer is thinking about more future upgrades. In this respect, Mike Terrett, President of Rolls-Royce Civil Aerospace, can imagine the results of present research programmes on larger engines to be flowing into the smaller ones as well.

The next thrust class up in the Rolls-Royce portfolio is produced in Dahlewitz, Germany. Some 400 BR710 engines produced by Rolls-Royce Deutschland are currently flying. The latest, 710C4-11 version for the Gulfstream G550 (formerly the GV-SP), with around five percent more take-off thrust and two percent lower fuel consumption, was certificated back in June of last year.

Another engine produced in Brandenburg is the Tay, now that responsibility for this type has passed from Derby to Dahlewitz. Some 1,500 of this engine are in service at present, including on the Fokker 100 and the Gulfstream IV (today known as the Gulfstream G300/G400). Moreover, a new version, the Tay 611-8C, with a digital engine control system (FADEC), is now available for the business jet application.

But new competition to the established players is around the corner. Snecma is to build the SM146 engine for the Russian Regional Jet (RRJ) family in collaboration with NPO Saturn from Russia. The French company is responsible for the core and the controls whereas Saturn will be in charge of the low pressure system and final assembly. According to Jean-Pierre Cojan, head of the civil division of Snecma Moteurs, this engine will have lower maintenance costs thanks to its reduced number of parts and will be available in different ratings between 53.33 and 80kN. Testing of the first engine is expected to commence in 2005, including on a new outdoor test rig in Rybinsk. This will be followed by flight tests at the end of 2005 or beginning of 2006. These might be carried out on an Ilyushin Il-76, which was cheaper than western types. The SM146 will incorporate state-of-the-art technologies such as 3-D aerodynamic design, single-crystal alloys and new cooling technologies. Pioneering innovations are not expected. The main objective is reliability “for typical small regional carriers that do not have large technical departments,” explains Cojan.

The fan will have swept wide-chord blades. Here Snecma is building on experience gleaned from the TECH56 research programme. According to Cojan, a reduced version of the research fan could be used on the SM146 without violating the terms of the agreement with GE. “Either partner can use its technologies as long as they don't go above 80kN.”

Meanwhile Snecma is building on results gained from the DEM21 experimental core engine. A preliminary test phase, begun in 2001, was successfully completed after 80 hours. The second phase began in June of this year and will entail up to 100 hours. Next year another development based on the same architecture, the DEM21-3 will follow. Despite its size, which is comparable with the SM146, it remains a pure technology acquisition programme.

According to Cojan, western airlines have shown a lot of interest in the French-Russian joint venture. “We are offering a substantial cost improvement compared with the competition. That was the formula which Embraer used before.” In this case Russia's low-cost structures are being combined with western expertise. In Cojan's view, Air France is a “natural partner for Snecma”. That is why the airline was the first to be approached. Besides, the engine builders had already had a meeting with other SkyTeam members. Cojan believes a procurement programme similar to that of the Star Alliance is possible. Eventually, over half of the RRJs are to be exported to the West, as Sukhoi General Director Mikhail Pogosyan confirmed.

Like all previous regional jets, the RRJ will be powered exclusively by a single engine, the SM146. “Two engine types would not work on an RJ”, given the likely level of orders. Besides, it would be too expensive to have two engines certificated, as Cojan makes clear.

Meanwhile the Antonov An-148 as the direct competitor on the Russian market, whose first prototype is to be completed by the end of this year, has time on its side. The jet will be powered by the Progress D-436, another version of which is already flying on the amphibious Beriev Be-200 and which is based on the D-36, previously developed by Lotarev, for the An-72/74. Another engine, the AI-22, is also under development at Progress for the 50-seater Tupolev Tu-324.

Pratt & Whitney Canada had submitted a tender for the RRJ programme as well with the PW800. After losing in the Russian competition and also in the competition for the Airbus A400M airlifter, for which a gas generator derivative was proposed, the company is now concentrating on unmanned air vehicle applications. Nevertheless, the management is still focusing on the next generation of 50 to 100-seat regional jets, as P&W Canada President Alain Bellemare confirms. “Regional jets are a very attractive market for us. We need to wait for the next wave of RJs and be patient.” According to Bellemare, his company is concentrating on new applications rather than on upgrades. The company is most likely expecting new types in the 50-seater market.

Meanwhile work continues on the PW800, which is supposed to consume ten percent less fuel than today's engines. A demonstrator of the core engine should be running later in the year. The PW800 will build on the geared fan technology which has been undergoing testing on the Advanced Technology Fan Integrator (ATFI) since March 2001. In the second phase of the programme (ATFI 2), the first engine runs are scheduled for the spring of 2004. MTU Aero Engines of Germany is still involved in this development. The company from Munich is contributing both the high-pressure compressor and also to the low pressure turbine.

It is also involved in most of the PW300 family, which now possesses eight members. The most powerful of these is the PW308 for the Hawker Horizon and the Dassault Falcon 2000EX with an enlarged fan and compressor. Additionally, the new, 27.1kN rated PW307A is to power the Dassault Falcon 7X.

Honeywell, too, is courting customers in the same thrust class with its AS907. Since BAE Systems ceased production of the RJX regional jet, which had been powered by the AS977, the AS907 for business aircraft has been the focus of attention. Certification of the powerplant used on the Bombardier Challenger 300 (formerly the Continental) was completed last year. According to Michael Bevans, Marketing and Sales Manager of the company based in Phoenix, Arizona, a new trend is emerging in the business aircraft segment. “Business jets are getting there today where the regionals already are. Customers want reliability and, especially, time-on-wing.”

In the case of the AS907, of which 40 are to be delivered this year, the designers therefore made simple maintenance a priority. According to Honeywell, line maintenance checks can be carried out entirely with only thirteen tools that are widely available, and line-replaceable units (LRUs) can be replaced in 20 minutes. Thanks to the round cross-section of the nacelle, the unit, which arrives at the aircraft manufacturer's in Canada as an integrated propulsion system, complete with nacelle and thrust reverse system, can be replaced from either side.

In Phoenix, they are hoping for new regional jets applications as well, in this case with up to 35 seats, and, according to Bevans, Asia might be a possibility here. If the manufacturers' forecasts are correct and 8,000 new aircraft are required over the next 20 years, then, in the view of Snecma's Jean-Pierre Cojan, there should be plenty of room for new candidates as regards both aircraft and engines. “A few years ago no one would have believed in the success of Embraer as it is today.”

From FLUG REVUE 9/2003

Last updated 11 August 2003

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