CFM International will announce a raft of orders for the Leap engine on the A320NEO (new engine option) at the Paris air show following a late redesign with a larger fan, which makes the engine more competitive with Pratt & Whitney's PW1100G geared turbofan.

Over the course of the show, CFM will reveal additional members to the initial Leap customer group, which is expected to include International Lease Finance Corp. (ILFC), Gecas (General Electric Capital Aviation Services), TAM of Brazil and Malaysian low-cost carrier AirAsia. Virgin America, which confirmed its selection on June 15, also chose Leap after CFM grew its fan diameter by 2 in.

In all, the initial sales surge is likely to include engines for up to 350 aircraft. The bulk of these are destined for AirAsia, which is reported to have recently upped its order to 200 from 150, while Gecas is expected to announce orders for 40-60. TAM, which earlier this year signed a memorandum of understanding for 22 A320NEOs, is also poised to select the Leap engine. A further 40 aircraft are on order for ILFC and 30 for Virgin America.

The PW1100G is already launched on the A320NEO following firm commitments from Lufthansa, ILFC and India's IndiGo, while the first Leap version is already committed to development for the Comac C919. Both engines are also officially in the frame for possible use on a re-engined Boeing 737. To date, Pratt has announced agreements to power 240 of the 332 A320NEO aircraft confirmed so far, although these numbers are due to change as Airbus has targeted orders and commitments for 500 or more NEOs by the Paris air show.

“We've recently optimized the product and gone to a little larger fan diameter,” says Tom Brisken, CFM's general manager for commercial customer strategy. “In the beginning, Airbus was not giving us a good score, and we heard that from customers. We were extremely upset, but now we've got the same boundary as Pratt & Whitney. The result is, we have increased the fan diameter by 2 in. without impacting ground clearance, and we've increased the bypass ratio to 10:1.”

Exactly why CFM appears to have been constrained to a smaller fan for so long remains a mystery; but following the change to a 78-in. fan, Brisken says, “I think Airbus will rate us equal in fuel burn, although we think we're 1% better, so we're going to have a 1% advantage—and that's the story we're going to be telling customers. Before we were discussing an engine with a 76-in. fan, and over the last month we've been able to market the engine on a much more competitive position. Before that, we were having issues in our campaigns,” he admits.

Ron Klapproth, Leap program director, notes that by “working the nacelle and aerodynamics, the overall change in nacelle maximum diameter is very small.” In addition, he says CFM hopes to have an edge over the PW1100G in terms of life-on-wing. “We have a very rigid structure with stiff frames and a stiff backbone, as well as active and passive clearance-control technology in the engine. So we're very confident we'll have the best fuel burn in a new engine, and we think we're going to have the best performance retention.”

The redesign also adds an additional stage to what is now a seven-stage low-pressure (LP) turbine. The first full-scale engineering core (eCore 2), with the production-standard 10-stage high-pressure compressor and two-stage HP turbine, began running at GE's Evendale, Ohio, facility in late May. “This is the Leap configuration, and we will run additional cores with a third in 2012 and a fourth in 2013,” says Klapproth. “It's just part of the normal development of a core engine. We ran eight builds of the GE90/GEnx architecture in 18 months, so Leap is running builds 9, 10, 11 and 12.”

The additional core runs will evaluate a series of planned improvements in materials, cooling, design and controls to provide the basis for further Leap generations. “People think we're out of gas and that's absolutely false. We're taking a proven architecture from a long-range fuel-burn, high-performance engine in the GEnx and combining it with the high-cycle reliability and endurance of the CFM56,” says Brisken.

Although eCore 1 was based on a single-stage HP turbine, rather than the two-stage production standard, CFM used the development to test blade technology. “It was mostly aimed at performance and cooling, and we're now taking lessons from that,” he declares.

“The LP turbine rig will run for several more weeks, and the next step will be to put together the HP and LP turbines in a dual-spool rig. So the second-stage HP turbine will be on its own spool and the LP turbine will have its own drive system. We've already got a performance signature of the LP turbine and we're getting good efficiency,” says Klapproth.

First run of the complete engine is scheduled for the first quarter of 2013, with certification in 2014 and entry-into-service on the A320NEO in 2016. “We will have run the equivalent of 18,000 full engine cycles on eight Leap engines by then,” he says.