With now more than 600 commitments for the 737 Max, Boeing has revealed additional details around its configuration decisions, including the selection of a 173cm (68in) engine fan size.

The CFM International Leap-1B featured on the 737 Max family will also have a "custom core" to meet Boeing's performance goals, said commercial aircraft unit CEO Jim Albaugh at the Goldman Sachs Global Industrials Conference in New York.

Albaugh called the selection of the 173cm fan the "sweetspot" that balances both fuel consumption, drag and weight considerations on the re-engined narrowbody.

With the larger fan, Boeing will also have to lengthen the nose landing gear of the aircraft by 15-20cm (6-8in) to increase the nacelle ground clearance to avoid contact with taxiway lighting.

Boeing Next Generation 737 chief engineer, John Hamilton, told Flightglobal in November 2010 the company had found a way to relocate items from the forward electronics equipment bay to accommodate the longer gear without the need of a nose blister fairing.

Albaugh said fly-by-wire will be introduced on one control surface, but did not specify which surface had been selected. Programme sources have indicated the spoilers are the most likely candidates for transition from mechanical to fly-by-wire flight control system.

Boeing now holds commitments for "north of 600" 737 Max family aircraft, said Albaugh, which he expects to enter service in 2017, though he is "driving our team to an earlier date than that".

"We're working very hard on what the airplane guarantees will be, once we finalise those we'll get the definitive agreements in place for the customers that we have," he said.

Boeing launched the 737 Max in August with 496 commitments from five customers and only one, American Airlines with an order for 100 aircraft, has been disclosed.

Source: Air Transport Intelligence news