Technology - LEAP of Pure Power

The looming threat of CFM International LEAP-ing ahead seems to have persuaded the two partners, Rolls-Royce and Pratt & Whitney, to bury their differences and cooperate more closely. They have set their sights on the next-generation of 120- to 230-seat airliners that is expected to generate a worldwide demand for around 20,000 planes and perhaps 45,000 engines over the next 20 years.

A jet engine is one of the most complex and amazing inventions ever, a marvel of human ingenuity. Its components, numbered by the thousands, must be machined to precise specifications using the lightest and toughest materials available and packed into the smallest possible space. For decades, technologists have toiled tirelessly to coax engines towards higher levels of power and efficiency and their mission will never be over. The surging price of oil is chiefly to blame; it has burned a big hole in the airline industry’s pocket and ruined most of its operating cost assumptions. The airlines are constrained to raise ticket prices but fear that this would make economy-class passengers desert them in droves. Consequently, many carriers worldwide have shut shop while scores have been driven to the brink.

Pressure is also mounting on the industry to do its bit in the fight against climate change through perceptible improvement in fuel burn and slashing CO2 emissions. The main emphasis is on replacements of today’s narrow-body planes that constitute the vast majority of the global commercial fleet. They must fly cleaner and quieter than ever before. However, this would require huge investments and a quantum leap in technology across the board. Once again, jet designers are being pressed to make their engines more fuel-efficient. But is the radical improvement demanded in commercial jet engine performance likely or even possible?

CFM LEAPS Ahead

CFM International, the global leader in jet engines by a long shot, thinks it is. The 50-50 joint venture between General Electric and Snecma delivers three out of every five engines that power narrow-body jet airliners. It is most closely associated with the iconic CFM56 family of power-plants fitted on a number of Airbus and Boeing variants. The CFM56, of which 29,000 engines have been ordered and 23,500 have already been delivered, is amongst the quietest and lowest-emissions engines flying. It is also claimed to have the lowest cost of ownership in the narrow-body market and a departure rating of over 99 per cent. Its successor, the eagerly awaited leading edge aviation propulsion (LEAP-X) turbofan, is bound to be just as exciting. The LEAP-X is a conventional design that uses technology developed for engines like the GE90 and GEnx. It employs sophisticated composite materials, next-generation 3D aerodynamics and low-emission combustion techniques in the engine’s hot-section (core) to cut fuel consumption. Its large fan will have just 18 blades, as against 36 on the CFM56-5C and 24 on the CFM56-7B engine. The reduced number of blades means a lighter fan containment structure, the weight saving on account of which is estimated to be 455 kg per twinjet. CFM has already completed full-scale aerodynamic, acoustic, bird strike and other tests on the fan.

Airframe manufacturers are queuing up to cash in on the LEAP-X programme, having been assured that the revolutionary new turbofan expected to be certified in 2016, will produce 50 to 60 per cent less NOX, emit 16 per cent less CO2, burn 16 per cent less fuel and fly 50 per cent quieter than today’s best CFM56 engine. The new engine also comes with the CFM56 legacy of unsurpassed reliability and low maintenance cost. The LEAP-1B has been selected as the sole power-plant for the new Boeing 737 MAX. The LEAP-1C will exclusively power the Comac C919 aircraft, a 168-190 passenger narrow-body twinjet, being designed and built in China. The LEAP-1A is being offered as one of the two options on the forthcoming Airbus A320neo. All these aircraft should enter commercial service in the 2016-17 time frame and are expected to dominate the global narrow-body market thereafter. CFM has already received advance orders for more than 3,400 LEAP engines. The future of the LEAP-X programme may be even brighter since the same technologies can be applied to an open rotor engine for 26 per cent decrease in fuel burn compared to the CFM56.

Pratt & Whitney’s PurePower Riposte

After sitting on the sidelines of the lucrative narrow-body market for some years, Pratt & Whitney seems determined to capture a greater market share. And the talisman of its ambitions is the PurePower PW1000G, a high-bypass geared turbofan (GTF) engine. The engine’s sophisticated gearing system allows the fan to rotate at relatively low speed, while the compressor and turbine operate at relatively high speed. This increases engine efficiency and reduces fuel burn, emissions, and noise. The radical design, expected to absorb at least $2 billion ( Rs. 11,000 crore) during development, has fewer engine stages and approximately 1,500 fewer compressor aerofoils, promising lower weight and reduced maintenance costs.

Last November, Time magazine named the PurePower PW1000G engine as one of the “50 Best Inventions” of 2011 and the most important development in aviation in the year. Although the PW1000G does not as yet enjoy the patronage that CFM’s LEAP engine commands, it has attracted some important customers, including Airbus for its A320neo airliner. This gives PurePower an Indian connection because low-cost carrier IndiGo has selected the GTF engine to power its 150 A320neo aircraft, due to begin entry into service in October 2015. The PW1000G will be the sole power-plant for the 150-to-215 seat Russian Irkut MS-21 narrow-body jet, first delivery expected in 2017 or later. Then there are forthcoming regional jets. Bombardier has chosen the PW1500G for its futuristic 110- to 145-seat CSeries regional twinjets. The CS100, expected to enter service by the end of 2013, will fly with the first operational PurePower engine. It will be followed by the CS300 a year later. The 70 to 96 capacity Mitsubishi Regional Jet (MRJ), whose first delivery is expected by early 2016, will be fitted with the smaller PW1217G GTF engine.

Pratt & Whitney claims that its new engines will offer a 12 to 15 per cent reduction in fuel burn, up to 15 per cent reduction in CO2 emissions as also 50 per cent decrease in NOX emissions and noise. The company has begun icing tests on the PurePower intended for the Bombardier CSeries and anticipates completing its certification by the end of the year. The engine slated for the MRJ logged its first flight in April and is also scheduled to begin certification testing soon.

Rolls-Royce Rolls Along

Meanwhile, Rolls-Royce is currently the exclusive engine supplier for the forthcoming Airbus A350 XWB longrange twinjet, boosting its prospects in the wide-body segment. Powered by Rolls-Royce Trent XWB engines, the A350 XWB is designed to compete against Boeing’s B777 as well as the larger B787 variants. It claims to offer an astounding fuel savings of up to 30 per cent compared with similar current aircraft. The 314-seat A350-900 is scheduled to make its first flight in the first half of 2013, with first delivery to launch customer Qatar Airways set for 2014. The 270-seat A350-800 and the 350-seat A350-1000 will follow.

Although Rolls-Royce and Pratt & Whitney are partners in the International Aero Engines (IAE) consortium, Rolls has steered clear of the LEAP-GTF tussle. Till date, it preferred to look further into the future and concentrate on developing a new, more efficient engine core to power the next generation of narrow-body airliners. While Pratt & Whitney enthusiastically embraced the GTF model, Rolls-Royce developed advanced two and three-shaft turbofans, known as the RB282 and RB285, respectively. Rolls-Royce believed these new designs could deliver the same efficiency as the GTF, obviating the requirement of a gearbox that might introduce needless complexity into the engine.