CFM International has started assembling the third version of the Leap-series turbofan engine family as initial test results on the first variant have “thrilled” company officials.

Assembly of the first Leap-1B for the Boeing 737 Max is starting about six weeks after CFM began testing the version of the Leap that is largely shared between the Airbus A320neo and the Comac C919. Testing on the Leap-1B is scheduled to begin in June next year.

“I’m proud and really happy to tell you that the engine is running very smoothly,” says Chaker Chahrour, CFM’s executive vice-president. “This engine wants to run.”

Although CFM is the exclusive engine provider for the 737 Max and C919, the Leap is locked in a heated battle with the Pratt & Whitney PW1100G geared turbofan for orders on the A320neo family.

The PW1100G entered flight-testing last May, but airlines are only now getting a chance to scrutinise the test data from both engines.

Not surprisingly, CFM wants airlines to know the tests on the Leap-1A model seems encouraging so far.

“From a mechanical standpoint the engine is running great,” Chahrour says. “It’s running smoothly. There are no glitches, no show-stoppers that we know of.”

A special point of emphasis by CFM was the timing of the first engine to test milestone for the Leap-1A on 6 September.

P&W has had mixed results with keeping all the variants of the PW1000G geared turbofan family on schedule. The PW1100G was delivered to testing on time in October last year. On the other hand, P&W delivered the PW1500G for the Bombardier CSeries last February, or more than a month after the aircraft was originally scheduled to achieve first flight.

By comparison, CFM delivered the Leap-1A a few weeks earlier than the company had predicted three years ago.

Within 24h of the first test, the Leap-1A was run “well above” full power at 33,000lb-thrust. It has also recorded 164 engine starts, 174h of tests and 269 cycles as of 16 October, Chahrour says.

Performance estimates of the engines vary, but CFM’s analysis predicts that the Leap-1A-powered A320neo will have a 2% fuel burn advantage over the same aircraft powered by the rival engine. The A321neo should have a 3% advantage, Chahrour says. CFM’s calculations include a 1% margin based on its expectation the Leap engine’s performance will degrade more slowly.

The device CFM is counting on to slow the rate of degradation is the debris rejection system, which includes inward-opening variable bleed vanes that divert dangerous particles away from the engine core. The one-year engine certification tests are not long enough to validate CFM’s analysed predictions, Chahrour says.

But CFM has collected initial results on tests of the Leap engine’s key technologies, including a ceramic matrix composite material in the stage 1 turbine shrouds and a five-stage compressor blisk. Both are new technologies being applied for the first time on the Leap, and are critical in CFM’s calculations of the engine’s potential fuel-savings.

“We stop every so often and borescope the engine actually on a daily basis after every series of tests that we do,” Chahrour says. “Everything is going very well.”

The tests on the Leap-1A will continue for about 10 more months, and the hardest tests are still to come. CFM plans to run an early version of the bock test – in which the engine is figuratively “tortured” – before submitting to the same test for certification. The Leap-1A also will be subjected to an early run of icing tests, Chahrour says.

In all, CFM will induct more than 15 of 28 development engines across all three variants by the end of 2014. Another 32 engines will be delivered to the manufacturers to complete airworthiness testing before the aircraft enter commercial service.