CFM is on track to complete by the end December the final design drawings for the first Leap-1A engine for the Airbus A320NEO, maintaining a plan that will culminate with entry-into-service in mid-2016.

The General Electric (GE) and Snecma joint venture is developing three versions of the Leap engine in parallel. In conjunction with the new Airbus engine, CFM is developing an almost identical -1C variant that is set to enter service on the Chinese-made Comac C919 in 2016. A third version, the -1B, is in development for the Boeing 737 MAX, which is scheduled for service entry in late 2017.

Revealing new details about the development effort, Leap Program Manager Gareth Richards says parts for the first Leap-1A test engine are being produced, and assembly is expected to start in April 2013. The engine is the first of 28 planned for the overall Leap development and certification effort, with 13 dedicated to the NEO engine, 12 to the -1B for the MAX and three for the -1C. “There is a lot of synergy between the -1A and -1C, although the fan structure is slightly different, as are the externals, which are unique. But the turbomachinery is all common,” says Richards.

About 30 more “flight compliance” engines also will be built to support the three flight test programs.

The design freeze on the Leap-1A/1C engines was completed earlier this summer, and the same “Toll Gate 6” milestone is expected for the Leap-1B in April 2013.

According to Richards, the focus now is shifting to initial assembly. “Once we pass that release, there are hundreds of design engineers who go to work to put that design down to the detailed level for sending out to engineering. So that’s what is in process right now. We are around 90% through that and aim to be finished by the end of the year,” he says.

The first Leap engine is expected to be fired up on the test stand for the first time around the end of September 2013. Although the Leap-1A and -1C are being developed in parallel because of their commonality, the first Leap to fly on the GE-operated Boeing 747 flying testbed will be the -1C C919 engine at the end of April 2014.

The current plan will be for the Chinese aircraft to fly shortly after, with U.S. FAR33 engine certification expected around the end of March 2015, and entry-into-service on the C919 in the second quarter of 2016.

The engine for the NEO, on the other hand, currently is scheduled to be airborne under the wing of the flying testbed at the end of September 2014, with FAR33 engine certification expected the following summer. First flight on the A320NEO is due around the third quarter of 2015 with entry-into-service the following year.

Development of the -1B engine begins in earnest with the first engine to test around the end of June 2014, followed by the start of flight tests on the flying testbed by the end of the first quarter 2015. Unlike the earlier Leap test engines, which will fly on GE’s existing 747-100 testbed, the 737 MAX engine will be flown on GE’s recently acquired, former Japan Airlines-operated 747-400.

FAR33 certification of the -1B is anticipated before the end of the first quarter 2016, providing margin before the planned start of 737 MAX flight tests.

Boeing officially says that these are expected sometime in 2016, though Aviation Week understands the timetable calls for the flight test program to start in the second quarter of that year.

Rather than the F101-derived core at the heart of the CFM56, the Leap engine series is based on an all-new core. Three core builds so far have been tested in support of the Leap effort, with a third due to start in the first quarter 2013. Further derivatives of the core, which is scaled to about 90% of the actual size of the Leap high-pressure spool, are planned beyond Core 3, says Richards. “We will be running a Core 4 and Core 5 to look at technology for the future. They need to be off the critical path, but will be used to support GE9X in particular (the engine in early development for Boeing’s proposed 777X), as well as for Leap future evolution,” he notes

Another question still hangs over the final thrust ratings for the Leap engine. The larger—1A and 1C—variants are expected to be defined in the same 33,000-lb.-thrust bracket as Pratt & Whitney’s PW1100G, while the -1B is widely expected to be configured around 28,000 lb. Boeing has yet to officially announce the targeted thrust, but confirms it plans to do so “before engine design freeze and before we reach firm configuration on the 737 MAX, which will be by mid-2013.”