A recent Boeing study predicted a demand for up to 23,000 single-aisle airliners over the next 20 years. For the three engine manufacturers involved in the seven single-aisle aircraft currently in development, the business case for developing all-new engines to power them has been more than justified.

Orders for the re-engined Airbus A320neo and Boeing 737MAX have already gone way beyond initial expectations, while other new narrowbodies, including Bombardier’s CSeries, China’s Comac C919, Embraer’s E-Jet family and Irkut’s MS-21, plus the Mitsubishi MRJ regional jet, are pushing the sales tally even higher.

All of these aircraft, except for the MS-21 which is also offered with Russian Aviadvigatel PD-14 powerplants, will be powered by new centreline turbofan engines, either CFM Leap-1 engines from the GE/Snecma partnership or Pratt & Whitney PurePower PW1000G geared turbofans.

Rolls-Royce is not involved in the current sales bonanza, having made an early decision that there was “no business case” for developing an engine for re-engined aircraft. The UK company insisted it would only commit to powering all-new designs, and had hoped to power the Embraer E-Jet family with a new two-shaft engine. Given the huge popularity of its neo range, Airbus is unlikely to launch a new design for at least a decade. Boeing is known to be studying an all-new replacement for the 737, however.

There is little doubt that the advent of new engines producing a claimed 15 percent improvement in specific fuel consumption over the existing CFM56 and International Aero Engines V2500 was a major stimulant to the decisions by Airbus (Hall 1, Stand 276) and Boeing (Chalets A324, B321) to re-engine their existing single-aisle aircraft. While both have futuristic designs in their respective technology drawers, committing to a new, conventionally configured design, with its huge development costs, would not have produced significant extra fuel-burn advantages to the re-engined derivatives. Blended-wing-body designs may come in a few years, while open-rotor engines have not reached a sufficient stage of development and will require an all-new airframe. Testing has shown that open-rotor noise can probably be made acceptable, but the timescale for service-entry remains uncertain.

Another factor known to have influenced Airbus’s decision to continue with the A320 was that major fuel savings are on the way from a forthcoming revolution in air traffic management. Programs such as the Single European Sky and NextGen in the U.S. will improve the efficiency with which aircraft navigate, reducing fuel usage by at least 10 percent. This will be at minimal cost to aircraft manufacturers, apart from avionics upgrades. Again, the business case for re-engining the existing aircraft was incontrovertible.

As the Paris Air Show approached, CFM (Chalet B121, Hall 2a B252) was leading the orders tally–but only just. Its Leap-1 family of engines are exclusive on the Chinese C919 and Boeing 737MAX and at the time of writing had garnered slightly more than half of A320neo orders to date. As the successor to the hugely successful CFM56, the Leap-1 engine will form the basis of the 50/50 Franco-American CFM International partnership’s business case for decades to come.

CFM is, however, competing against a formidable opponent in the form of Pratt & Whitney’s PurePower PW1000G. The early success of the company’s unique geared-turbofan technology (GTF) concept has surprised even the Hartford, Connecticut-based manufacturer, with five applications and more than 3,500 sales since the PW1000G program was launched in 2008.

The PW1000 has found exclusive applications on the Bombardier CSeries, Mitsubishi MRJ and, in a recent development, the Embraer E-Jet. P&W formerly competed on the A320 as part of the International Aero Engines (IAE) V2500 consortium, which included Rolls-Royce and Japanese Aero Engines (JAEC). Under the revised IAE arrangement, which was finalized in mid-2012, MTU’s share grew to 16 percent, Japanese Aero Engines retained its original 23 percent and Pratt & Whitney holds the balance. The reshuffle followed Rolls-Royce’s decision in October 2011 to sell its 32.5 percent equity stake in the V2500 program to Pratt & Whitney for $1.5 billion. The U.S. manufacturer is partnered with German engine manufacturer MTU Aero Engines on development of all PurePower engines, and with MTU and JAEC on engines for the A320neo only.

Three versions of the Leap-1 are currently in development: The Leap 1A and 1C for the Airbus A320neo and Comac C919; and the Leap 1B for the Boeing 737MAX. The first two engines, both producing 24,500 to 33,000 pounds thrust, feature identical turbomachinery, the externals customized for their respective applications. The MAX engine, running at 20,000 to 28,000 pounds thrust, has a smaller fan and core.

Testing of individual modules has been ongoing and assembly of the first complete test engines began in late April, with performance testing due to start in September. “We’re going through a long build process because there is a lot of test instrumentation, as these are brand new, clean-sheet [design] engines,” said Gareth Richards, Leap program manager.

An unprecedented 28 engines are involved in the overall Leap development and certification program, of which 13 are dedicated to the A320neo, 12 for the 737Max and three for the Comac C919. A further 30 flight compliance engines will be built to support the three-aircraft flight-test programs.

The Leap 1A and 1C programs are about nine months ahead of the Leap 1B effort, so it is a busy time for CFM as it prepares all three engines for the test and certification programs. “We’re running 14 engines in the certification program, which is more than normal because we want to achieve total validation before it flies,” said Richards. “Another 14 will be run for the 737MAX program, so by mid-2014 to mid 2015 we’ll have 28 engines on test.” Testing will be shared equally between GE and Snecma, with icing trials to be carried out at its new, $50 million icing test center at Winnipeg, Canada.

CFM’s original, but aging, Boeing 747-100 and a newly acquired ex-JAL 747-400 will fly the engine tests. “We’ll start flight tests of the 1A and 1C in mid-2014 and of the 1B in early 2015,” said Richards.

Such is the level of orders that CFM is preparing for an unprecedented increase in production rates as it transitions from CFM56 to Leap production. “We’ll build more than 1,400 engines this year and 1,500 in 2015,” said Richards. “Our task in 2016 is to begin producing the Leap 1A and 1C. It will be like changing a wheel while driving down a highway at 70 [miles per hour].” To compound the challenge, he added that CFM is totally changing its supply chain and assembly process, “because the Leap is a new design and the engine goes together in a different way.”

By 2019, production of the Leap family will have reached 1,700 a year for all versions. “We could go to more than 1,800 after 2020,” he said. “We’re investing in new factories all over the world in anticipation of that.” Only a few hundred CFM56s a year will still be produced, for U.S. military aircraft and spares to support the more than 24,000 engines in service. “As long as there are orders, we’ll build them,” said Richards.

CSeries First Flight

As it prepares PW1000-series engines for five applications, Pratt & Whitney (Chalet A330) has been faced with no less a test and certification task than CFM. Certification of the PW1500G Bombardier CSeries engine was achieved on time in February, marking the first certification milestone for the new powerplant. It followed 4,500 hours of rigorous ground tests since the first engine went to test in September 2010, including 340 hours of flight trials on P&W’s Boeing 747SP aircraft. The first flight of the CSeries test aircraft is now set for the end of June.

To date more than 9,000 hours of tests have been accumulated on the PW1000G fan drive reduction gear system, which enables the fan and core to run at optimum speeds. “We’ve validated the improvements in fuel efficiency and noise reduction we targeted in 2007,” said Bob Saia, vice-president, next generation product family at P&W.

Flight testing of the PW1200G engine powering the Mitsubishi MRJ began in April 2012, although with certification delayed until the second half of 2015, the program is on a slower timescale than originally planned. The engine shares considerable commonality with that of the CSeries, however. “We’re able to use a lot of experience from the PW1500G for the MRJ, which reduces the scale of the test program,” Saia said.

Ground tests of the 33,000-pound-thrust PW1100G-JM engines for the A320neo (the “JM” stands for Japanese Aero-Engines and MTU, partners in the A320) was completed in April after 120 hours. The engine recently flew on a 747SP testbed for the first time.

Saia said that despite the introduction of “game changing” technology, there has been nothing particularly unusual about the PurePower test program. “We’ve done about the same amount of work as we did for the GP7000 and PW2000 before that,” he said. “There’s nothing unique about the gearbox architecture, even though there is a lot of new technology, but that’s the same for any engine.” He added that ongoing development would bring fuel efficiency improvements of around one percent a year, and include increasing the reduction gearing from the current 3:1 to 4:1, or even 5:1, further reducing fan speed and increasing the core efficiency. “We’ll deliver a 15-percent fuel-burn advantage for the A320neo. Our development program will being a further 10 percent over the next decade,” he said.

The recent success in winning the powerplant battle for the Embraer E-Jet family was a huge boost to the PurePower program and will see the 15,000- to 22,000-pound-thrust PW1700G and 1900G engines enter service in 2018. The win was a blow to both CFM and Rolls-Royce, GE having powered the earlier E-Jets (while R-R powered the earlier Embraer regional jets). “Pratt & Whitney’s extensive engine testing and validation process positioned them to meet our economic and environmental improvement targets as well as the program timeline for the new generation of the E-Jet aircraft family,” said Embraer president and CEO Frederico Fleury when the award was announced in January.

Despite uncertain beginnings, Pratt & Whitney now knows the company’s huge investment in geared-turbofan technology has paid off. Saia said the change in the engine’s fortunes can be traced back to the early 2000s, when the dramatic increases in aircraft operating costs resulting from fuel price rises began to dominate thinking about engine development. “We’d found it difficult to get momentum behind the geared concept when fuel was just a dollar a gallon. When it reached $3.50 that changed,” he said. Fuel costs now account for 40 to 50 percent of total operating costs. “That’s when we re-energized the GTF program and moved from research to product development.”

Saia admited that P&W had expected the PW1000 to power an all-new aircraft in 2012/13. “We’d created a technology roadmap for geared architecture and product entry for then.” The engine flew on Airbus A340 and Boeing 747 demonstrators in 2007/8, proving the GTF concept. Then, in late 2007, Bombardier and Mitsubishi chose the engine for their respective aircraft. “We sold the GTF to them on the basis of double-digit fuel-burn improvements and lower maintenance costs than current engines,” said Saia.

The rest is undeniably history. “Airbus and Boeing were both looking at product refreshment for both new and re-engined aircraft,” recalled Saia. “Ten years ago I would have said there was no probability that they would re-engine the A320 and 737. I firmly believe the CSeries and MRJ decisions were major factors in Airbus’s decision to go with our engine.”