CFM International last week froze the design of the Leap engine variant destined to power Boeing’s new 737 Max narrowbody. The Snecma-GE joint venture has said it expects to achieve the first full engine test of the Leap-1B in the middle of next year, followed by initial flight-testing in 2015 and powerplant certification in 2016. Boeing expects the 737 Max to enter service in 2017.

The 20,000- to 28,000-pound-thrust Leap-1B turbofan uses a smaller fan and core than do the Leap-1A and -1C engines under development for the Airbus A320neo and Comac C919, respectively. CFM froze the design for the -1A and -1C in June last year. Manufacturing of the first complete Leap-1A started last month under a schedule that calls for the start of ground testing 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 engines,” said GE’s Leap program manager, Gareth Richards.

CFM has spent five years conducting component and rig tests on Leap hardware. An unprecedented 28 engines participate in the overall Leap development and certification program, of which 13 perform tests for the A320neo, 12 for the 737 Max and three for the C919. The company plans to build a further 30 flight compliance engines to support the three-aircraft flight-test 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 737 Max program, so by mid-2014 to mid-2015 we’ll have 28 engines on test.” Plans call for GE, which expects to share testing equally with Snecma, to carry out icing trials at its new $50 million research and development center at Winnipeg, Canada.

“The extensive component tests we have completed so far, including both the core engine and full fan module testing currently under way, indicate that we are on track to deliver world-class fuel efficiency for the 737 Max, along with the world-class durability that we established with the CFM56 engine family,” said Snecma’s Leap program manager, François Bastin.

Meanwhile, strong orders for both the A320neo and 737 Max mean that CFM will need to accelerate production rates rapidly. This year it expects to build 1,400 of the existing CFM56 engines, rising to 1,500 in 2015. Then in 2019, after the Leap turbofans enter production, overall annual output could run as high as 1,900 engines.