ATLANTA, Georgia — Ground tests of the first CFM Leap-1B engine for Boeing’s 737 MAX family have begun at Snecma’s site in Villaroche, France.

The engine, which ran for the first time on June 13, subsequently reached its full thrust rating of 28,000-lb, says the General Electric-Snecma joint venture. The Leap-1B, which will be available at various thrust ratings down to 23,000-lb., is aimed at engine certification in 2016 and entry into service on the initial 737-8 variant in 2017.

Flight tests of the Leap-1B are expected to begin in early 2015 on one of GE’s two 747 flying testbed aircraft in Victorville, California, while the first -1B powered 737 MAX is due to make its maiden flight in 2016. The initial ground test engine in France will be used to verify mechanical operation, stall margin and engine starting. The -1B work forms part of a broader test campaign which includes two other engine variants for the Airbus A320neo and the Comac C919. In all, the total program for all three versions includes 28 ground and CFM flight test engines, along with a total of 32 flight test engines for Boeing, as well as Airbus and COMAC. CFM estimates the test fleet will accumulate approximately 40,000 engine cycles leading up to entry into service.

Boeing, which will take delivery later this month of the 10,000th CFM56-7B engine for the Next Generation 737, says the Leap-1B makes up the bulk of what will be a 14% fuel burn improvement over the current model. The CFM56-7B-powered version has itself seen a 6% improvement in fuel burn since entering service in the late 1990s.

The 737 MAX also currently makes up the bulk of the firm backlog for the Leap engine, accounting for 4,046 units out of the total orderbook of 6,620 engines. The tally also includes 1,774 Leap-1A engines for the A320neo and 800 Leap-1Cs for the C919.