As Boeing designers work toward firm configuration of the new 737 MAX narrowbody airliner next year, improvements to the current 737 family continue apace, while program v-p and general manager Beverly Wyse oversees preparations for the next production rate break. Now building thirty-five 737NGs a month, the company’s plant in Renton, Washington, early this year increased its rate from 31.5 “nearly flawlessly,” said Wyse, thanks to what she described as an intense focus on the fundamentals of ensuring that suppliers and Boeing itself had put enough capacity in place well in advance of the actual rate break.

Next, Boeing expects to raise production to 38 in April of next year and, finally, to 42 about a year later. “All of the data we have says those transitions are on plan,” said Wyse.

Judging by the continued strength in narrowbody demand, particularly from emerging markets, Boeing sees little choice but to continue its push to raise output.

“What we hear from our customers is, especially in these next three to five years, we’re underserving the market just slightly,” said Wyse. “That is, customers that tell us they would take earlier, increased numbers of positions in the next three to four years if we could provide them.”

Although Wyse wouldn’t venture to project the timing of any rate increase beyond 42 a month, she said the company has begun studies into the prospect, and it appears highly likely that Boeing will need to add a third line in Renton as it introduces production of the 737 MAX in 2017. Preliminary plans call for the third line to run parallel to today’s Line 1, where it now builds 21 airplanes a month. By that time the shorter Line 2, which now produces 14 airplanes monthly, will have progressively raised its output, to 17, then to 19 and, finally, to 21 as well.

Just weeks before this year’s Farnborough International Airshow, Boeing took reporters on a tour of its Renton facility, highlighted by a rare look at the 4-20 Building, where two years ago it switched from the traditional method of assembling wings in a vertical position to one that uses a so-called horizontal build line in an effort to foster efficiency as it continues its rate hikes.

By 2014 it expects to employ a second horizontal build line, or HBL 2, for which it has already begun preparing floor space. By 2017 the facility expects to build wings for both the 737NG and 737 MAX and is likely to continue to do so for at least two years, until a full transition to MAX production takes place.

PIP Plans

Meanwhile, Boeing continues to add new features to the NG, following last year’s introduction of a performance improvement package (PIP) that has delivered between a 1- and 2-percent fuel-burn reduction. Further PIP developments will produce another 0.2 to 0.3 percent of improvement by the fourth quarter of 2013, according to Wyse.

Plans for further enhancements include what Wyse characterized as a fairly major package to extend B, C and D check intervals that would result in a 7-percent cut in scheduled maintenance burdens and increasing in-service times.

Finally, a modification to the new Sky interior planned for introduction by 2014 would involve a slim-line “S-wall” in the lavatory that would allow another seven inches of space and give airlines an option to reconfigure the cabin to add three more passenger seats.

Boost Demand

Boeing expects the improvements to boost already strong demand for the NG, and not only from its established operator base: over the past five years it has introduced 28 new customers. By late June the company had delivered more than 7,000 737NGs and its backlog stood at 2,605 airplanes. Wyse said it would likely collect its 10,000th order in a matter of a month or two. Boeing has sold out all delivery slots into the second half of 2016. Only “minimal” capacity remains in 2016 and 2017.

By that time Boeing expects to have flown the first MAX 8, the core product of the three-airplane family. Scheduled for entry into service in 2017, the MAX represents “the next big step” in the 737’s evolution with its new CFM Leap-1B engines, new nacelle package and new struts to support the heavier powerplants. An eight-inch nose gear extension will provide the clearance to allow for a wider fan, now fixed at 69 inches, said Wyse. Boeing introduced the rest of the fuselage, systems and wing revisions to support the extra weight of the airplane, she added.

Plans call for a new, “advanced technology” winglet designed by Boeing to aid fuel efficiency by 1 to 1.5 percent, while an aftbody aero improvement–involving removal of the NG’s vortex generators, a redesign of the auxiliary power unit inlet and an extension of the tail cone to do away with blunt end on today’s 737–would cut fuel burn by another 1 percent; flight deck revisions would support certification and new engine requirements.

Having now completed the so-called aerodynamic trades, designers expect to complete all architectural trades by this year’s third quarter, said Wyse. Although she hesitated to offer specifics, she did mention design work on new digital-bleed and fly-by-wire spoiler systems.

Planning for a supplemental type certificate based on the NG, Boeing expects no “significant” changes to the architecture that would affect performance or the aircraft’s overall capabilities, however. “Our intent is to largely use the same production system that we have today,” said Wyse. “So, while we may have gauge-ups, it’s not going to be a whole new digital design or fundamentally restructuring the aircraft.”

Also reluctant to quote any percentage of commonality between the NG and MAX, Wyse questioned the basis for Airbus’s claims that the A320neo will be 95 percent common to the current A320. “I could pick a metric, and say it will be 96 percent common,” she said. “But basically what we’re focused on right now is just making the minimum number of changes to the aircraft that will provide us with the maximum amount of performance benefits for the customers.”

Boeing expects the MAX to burn, on average, 14 percent less fuel than the 737NG uses and 8 percent less than the Neo.

Schedules call for completion of firm configuration next year, followed by detailed design in 2014, aircraft assembly in 2015, first flight in 2016 and entry into service in 2017.