PowerJet has won over sceptics by delivering a Western-standard engine with Russian help
Leonardo da Vinci said that simplicity was the ultimate sophistication, and the French-Russian joint venture PowerJet is adopting the same philosophy in its development of the SSJ's SaM146 engine. PowerJet has just completed tests on the second of a series of eight examples of the engine, which has largely been developed over the past six years and which is due to undergo its first flight tests in the near future.
The engine effectively began life in late 1999 as a Snecma high-pressure core demonstration project known as DEM21, created as the French company sought to compete within the burgeoning regional jet market - having been forced to scrap proposed joint development, with Pratt & Whitney Canada, of the SPW14 turbofan for the axed 70-seat Aero International (Regional) Airjet.
Snecma reasoned that regional jets needed to be less expensive to operate and that a simplified engine based on the DEM21 core, with a thrust range slotted beneath that of the CFM International CFM56, would prove a strong candidate. "It's a basic engine," says SaM146 product manager Antoine Chereau. "We wanted to have a low-cost engine, and needed something with mature technology to make sure there would be no surprises."
But while Snecma had experience in constructing "hot section" components for its M88 military engine, as well as fan, gearbox and low-pressure turbines for the CFM56, it was nevertheless a new entrant when it came to high-pressure cores for civil aircraft. Success with the new powerplant would enable Snecma to accede to the much-sought lead position on a civil engine programme. Having decided that nothing short of a working example would be necessary to convince potential customers that it was serious, Snecma built the DEM21.
Regional jets typically operate short sector lengths with high numbers of cycles and Snecma aimed to reduce operating and maintenance costs by constructing a core with thermally durable materials, including monocrystalline blades, and fewer overall components.
Six-stage compressor
The DEM21's architecture featured a six-stage compressor compared with the nine stages in the CFM56. The core was short, with a single-stage high-pressure turbine and compact compressor. The first three compressor disks employed bladed-disk technology they were produced as integrated one-piece titanium components rather than comprising separate blades fixed to a central retainer.
Turbine blades were also subject to automated clearance control to minimise clearance between the rotating and stationary parts of the core. Although the DEM21 was officially a demonstration model, Snecma built the core using available industrial processes to ensure that, if a customer emerged, the powerplant could be developed within three years.
Snecma's opportunity to build the engine came in 2001 when Sukhoi started pursuing the Russian Regional Jet (RRJ) programme (as the SSJ was originally dubbed). CFM had long been interested in powerplant work within Russia, with proposals to re-engine aircraft such as the Ilyushin Il-86. Although these projects made little progress, Russia's Rybinsk Motors - which manufactured engines for types including the Tupolev Tu-154, Ilyushin Il-76 and Il-62 - was supplying components for CFM56s under a 1997 co-operation agreement.
Rybinsk Motors combined with Lulka-Saturn in 2001 to create NPO Saturn, and Snecma agreed with the Russian company in the same year to develop and offer the SM146 - later redesignated the SaM146 to reflect Saturn's contribution - for Sukhoi's planned jet. Snecma and Saturn faced competition, notably from P&WC, which put forward its geared-fan PW800, with promises of substantial workshare to Russian firms including engine design bureau Aviadvigatel. The PW800 featured on Sukhoi's shortlist, after the rival General Electric CF34 and Rolls-Royce BR710 were eliminated, but ultimately lost to the SaM146 in April 2003.
"One of the reasons we were selected was because of the lower cost," says Chereau. "We'd also chosen to make it in Russia, with a Russian partner. Both of those were important."
Several Safran Group companies besides Snecma are contributing to the project: Hispano-Suiza has developed the third-generation full-authority digital engine control (FADEC). Aircelle is designing and manufacturing the high-composite nacelle, including the butterfly-type thrust reverser, exhaust nozzle, engine mounts and cowl doors. Under a risk-sharing agreement sealed last year, Italy's Avio has 10% of the programme, providing the accessory drive and transfer gearbox.
Easy maintenance
"We've been working with 3D tools to anticipate MRO operations, to do it virtually, to make sure the engine is simple and easily maintainable," says Chereau, who adds that a basic quick engine change should be achievable within 2h.
While Snecma leads on the core, the Russian manufacturer handles the "cold" section: the 1.2m (48in) fan and booster, low-pressure turbine and exhaust. The two partners founded a new venture, the VolgAero plant in Rybinsk, in October 2005, and this facility is at the heart of Russian SaM146 production. VolgAero has three production lines handling rotating parts, casings and powerplant accessories. It handles the fan disk and low-pressure spool, and is responsible for casings for the high-pressure compressor, as well as those for the high-pressure and low-pressure turbines. The plant also builds the intermediate and exhaust casings.
"Establishment of the joint venture enables us to use the state-of-the-art manufacturing technology that other aviation manufacturing companies possess," says NPO Saturn's SaM146 programme director Igor Yudin. The VolgAero plant is to install 100 machining systems, including over 20 numerical-control machining cells, for its work.
Moscow's All-Russian Scientific Research Institute of Aviation Materials and Central Institute of Aviation Motors are lending technical support to qualify the material supply chain on the Russian side.
"It's going to be the first time we've led integration of a commercial aircraft engine and designed such central elements as the core and the FADEC," says Snecma vice-president for commercial engines Jean-Pierre Cojan. "We had a lot of sceptics in the beginning, people who predicted we couldn't build a Western-certificated engine with such a large content being from Russia. But Russia has a fantastic educational base and fantastic employees."
As well as overseeing design and production, PowerJet will co-ordinate marketing of the SaM146. Chereau says: "Russian partners are very good at designing engines and good at building them, but they're not particularly good at selling them."
Tests on the SaM146 core began at the end of November 2005 at Snecma's Villaroche facility in France, where the section achieved its nominal thrust. The SaM146 is designed for the 14,000-17,500lb thrust (62-78kN) range.
Much of the full engine testing will be done in Russia. Saturn's Rybinsk facility has refurbished one test cell and is constructing two more, while a further Safran-Saturn joint venture, Poluevo-Invest, has completed an open-air test cell outside the city. One of only three in the world, the $25 million open-air facility will be used for crosswind, weather, ingestion and blade-out tests. It will be commercially available for other powerplant testing once SaM146 work is finished.
First tests on the SaM146 engine, to check basic structural elements, began in July 2006 and a second example completed test runs in December. During 34h of testing this second engine achieved take-off thrust requirements for the larger SSJ 100-95 variant.
Fuel consumption
It confirmed aeromechanical characteristics of the fan, demonstrated steady-state and transient stability between operating modes, and the engine's parameters stayed within limits. Specific fuel consumption was close to forecast levels, and the engine has undergone dismantling and inspection to ensure no defects have emerged that might delay further tests.
Eight engines will be used in the certification programme that will span over 4,500 cycles. Flight tests, probably using the fourth engine, are scheduled to begin by the end of March using an Ilyushin Il-76 from the Gromov Flight Research Institute. Two series of flight tests will be performed, in Moscow and at Istres in France. Another 10 or 12 SaM146 engines will be built for SSJ certification tests.
Certification of the SaM146 is scheduled for March next year. While the SSJ will be certified in Russia first, PowerJet is prioritising European certification for the engine to maximise its market appeal. The company hopes to sell two-thirds of the engines outside Russia.
"From the point of view of NPO Saturn it's not just an engine project. Our prime objective is to manufacture an engine that will comply with European and international environmental regulations - it means entry to the international market," says Yudin. "Russian companies alone cannot break this market."
Snecma believes that, with the SaM146, it will be able to pursue other programmes beyond the Russian jet, although it has yet to identify these formally. Cojan says: "This engine will have other applications. But for now we're mainly focusing on making the Superjet successful."
Source: Flight International
