Boeing's changes to the 737 Max 8 reveal the airframer accepted a significantly larger weight penalty to achieve a similar range increase as the Airbus A320neo, although with what the US airframer considers as superior fuel efficiency.
Boeing had not publicised 737 Max weight and range specifications before today. The programme does not expect to complete a firm concept for the new single-aisle derivative until at least September, and a firm configuration will not be finalised until mid-2013.
But the new figures allow a direct comparison between the 737 Max 8 and A320neo, the two most in demand competitors in the 150- to 179-seat segment.
Last December, Airbus had revealed the re-engined A320neo will fly 510nm further than the A320, but with a 3,500lb (1,580kg) increase in operating empty weight.
Boeing has increased the range of the 737 Max 8 by 540nm (945km), but at the cost of a 5,000-6,000lb increase in operating empty weight, says Michael Teal, 737 Max chief project engineer.
For Airbus, the switch to either the CFM International Leap-1A or the Pratt & Whitney PW1100G involved fewer complications. Besides adding sharklets, Airbus made few major structural or system changes to the standard A320.
Ground clearance requirements forced Boeing to extend the landing gear of the 737 Max by 20.3cm (8in). The initial concept images of the 737 Max released in May revealed a small chin blister to accommodate the extra bulk of the landing gear. As Boeing refines the design concept, engineers are working to slim down the gear fairing, either by reducing the size of the gear or englarging the internal space inside the wheel well.
Even eliminating the fairing completely will not produce a measurable decrease in airframe drag, but Boeing engineers are motivated to make the airframe as clean as possible, Teal says.
In addition to the nose gear change, Boeing also strengthened the wing section around the engine strut, as the heavier Leap-1B engine requires extra support, he says.
The design changes also include a new blended-feather winglet, a 787-like extended tail cone and fly-by-wire spoiler controls, Teal says.